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-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-dotAll-does-not-affect-dotAll-property.js49
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-dotAll-does-not-affect-ignoreCase-flag.js67
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-dotAll-does-not-affect-multiline-flag.js59
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-dotAll.js105
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-backreferences.js55
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-characterClasses.js67
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-characterEscapes.js67
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-lower-b.js77
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-lower-p.js61
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-lower-w.js77
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-upper-b.js57
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-upper-p.js63
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-upper-w.js57
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-does-not-affect-dotAll-flag.js67
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-does-not-affect-ignoreCase-property.js55
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-does-not-affect-multiline-flag.js67
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase.js47
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-multiline-does-not-affect-dotAll-flag.js59
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-multiline-does-not-affect-ignoreCase-flag.js67
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-multiline-does-not-affect-multiline-property.js49
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-multiline.js49
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-remove-modifiers.js45
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/browser.js0
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/changing-dotAll-flag-does-not-affect-dotAll-modifier.js77
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/changing-ignoreCase-flag-does-not-affect-ignoreCase-modifier.js55
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/changing-multiline-flag-does-not-affect-multiline-modifier.js51
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nested-add-remove-modifiers.js45
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-add-dotAll-within-remove-dotAll.js71
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-add-ignoreCase-within-remove-ignoreCase.js45
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-add-multiline-within-remove-multiline.js47
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-remove-dotAll-within-add-dotAll.js71
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-remove-ignoreCase-within-add-ignoreCase.js45
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-remove-multiline-within-add-multiline.js47
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-dotAll-does-not-affect-dotAll-property.js43
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-dotAll-does-not-affect-ignoreCase-flag.js49
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-dotAll-does-not-affect-multiline-flag.js49
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-dotAll.js71
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-backreferences.js43
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-characterClasses.js55
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-characterEscapes.js52
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-lower-b.js53
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-lower-p.js55
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-lower-w.js53
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-upper-b.js53
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-upper-p.js56
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-upper-w.js53
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-does-not-affect-dotAll-flag.js49
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-does-not-affect-ignoreCase-property.js49
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-does-not-affect-multiline-flag.js49
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase.js49
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-multiline-does-not-affect-dotAll-flag.js49
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-multiline-does-not-affect-ignoreCase-flag.js49
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-multiline-does-not-affect-multiline-property.js43
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-multiline.js45
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/shell.js0
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/browser.js0
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/shell.js0
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-and-remove-modifiers-can-have-empty-remove-modifiers.js68
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-and-remove-modifiers.js74
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-modifiers-when-nested.js44
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-modifiers-when-not-set-as-flags.js68
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-modifiers-when-set-as-flags.js46
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/browser.js0
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/remove-modifiers-when-nested.js44
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/remove-modifiers-when-not-set-as-flags.js68
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/remove-modifiers-when-set-as-flags.js68
-rw-r--r--js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/shell.js0
67 files changed, 3467 insertions, 0 deletions
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-dotAll-does-not-affect-dotAll-property.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-dotAll-does-not-affect-dotAll-property.js
new file mode 100644
index 0000000000..7edf9b90a4
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-dotAll-does-not-affect-dotAll-property.js
@@ -0,0 +1,49 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Adding dotAll (`s`) modifier does not affect RegExp instance `dotAll` property.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?s:)/;
+assert(!re1.dotAll, "RegExp instance dotAll flag should not be set");
+
+var re2 = new RegExp("(?s:)");
+assert(!re2.dotAll, "RegExp instance dotAll flag should not be set");
+
+var re3 = /(?s-:)/;
+assert(!re3.dotAll, "RegExp instance dotAll flag should not be set");
+
+var re4 = new RegExp("(?s-:)");
+assert(!re4.dotAll, "RegExp instance dotAll flag should not be set");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-dotAll-does-not-affect-ignoreCase-flag.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-dotAll-does-not-affect-ignoreCase-flag.js
new file mode 100644
index 0000000000..1ebb730625
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-dotAll-does-not-affect-ignoreCase-flag.js
@@ -0,0 +1,67 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Adding dotAll (`s`) modifier in group should not affect ignoreCase (`i`) flag.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?s:.es)/;
+assert(re1.test("aes"), "s should match s in modified group");
+assert(re1.test("\nes"), "s should match s in modified group");
+assert(!re1.test("aeS"), "s should not match S in modified group");
+assert(!re1.test("\neS"), "s should not match S in modified group");
+
+var re2 = /(?s:.es)/i;
+assert(re2.test("aes"), "s should match s in modified group");
+assert(re2.test("aeS"), "s should match S in modified group");
+assert(re2.test("\nes"), "s should match s in modified group");
+assert(re2.test("\neS"), "s should match S in modified group");
+
+var re3 = /(?s-:.es)/;
+assert(re3.test("aes"), "s should match s in modified group");
+assert(re3.test("\nes"), "s should match s in modified group");
+assert(!re3.test("aeS"), "s should not match S in modified group");
+assert(!re3.test("\neS"), "s should not match S in modified group");
+
+var re4 = /(?s-:.es)/i;
+assert(re4.test("aes"), "s should match s in modified group");
+assert(re4.test("aeS"), "s should match S in modified group");
+assert(re4.test("\nes"), "s should match s in modified group");
+assert(re4.test("\neS"), "s should match S in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-dotAll-does-not-affect-multiline-flag.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-dotAll-does-not-affect-multiline-flag.js
new file mode 100644
index 0000000000..2f9adf75e3
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-dotAll-does-not-affect-multiline-flag.js
@@ -0,0 +1,59 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Adding dotAll (`s`) modifier in group should not affect multiline (`m`) flag.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?s:.es$)/;
+assert(re1.test("\nes"), ". should match newline in modified group");
+assert(!re1.test("\nes\nz"), "$ should not match newline in modified group");
+
+var re2 = /(?s:.es$)/m;
+assert(re2.test("\nes"), ". should match newline in modified group");
+assert(re2.test("\nes\nz"), "$ should match newline in modified group");
+
+var re3 = /(?s-:.es$)/;
+assert(re3.test("\nes"), ". should match newline in modified group");
+assert(!re3.test("\nes\nz"), "$ should not match newline in modified group");
+
+var re4 = /(?s-:.es$)/m;
+assert(re4.test("\nes"), ". should match newline in modified group");
+assert(re4.test("\nes\nz"), "$ should match newline in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-dotAll.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-dotAll.js
new file mode 100644
index 0000000000..8c163adf54
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-dotAll.js
@@ -0,0 +1,105 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ dotAll (`s`) modifier can be added via `(?s:)` or `(?s-:)`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?s:^.$)/;
+assert(re1.test("a"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("3"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("Ï€"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("\u2027"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("\u0085"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("\v"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re1.test("\f"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re1.test("\u180E"), "Pattern character '.' should match non-line terminators in modified group");
+assert(!re1.test("\u{10300}"), "Supplementary plane not matched by a single .");
+assert(re1.test("\n"), "Pattern character '.' should match line terminators in modified group");
+assert(re1.test("\r"), "Pattern character '.' should match line terminators in modified group");
+assert(re1.test("\u2028"), "Pattern character '.' should match line terminators in modified group");
+assert(re1.test("\u2029"), "Pattern character '.' should match line terminators in modified group");
+assert(re1.test("\uD800"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("\uDFFF"), "Pattern character '.' should match non-line terminators in modified group");
+
+var re2 = new RegExp("(?s:^.$)");
+assert(re2.test("a"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("3"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("Ï€"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("\u2027"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("\u0085"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("\v"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re2.test("\f"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re2.test("\u180E"), "Pattern character '.' should match non-line terminators in modified group");
+assert(!re2.test("\u{10300}"), "Supplementary plane not matched by a single .");
+assert(re2.test("\n"), "Pattern character '.' should match line terminators in modified group");
+assert(re2.test("\r"), "Pattern character '.' should match line terminators in modified group");
+assert(re2.test("\u2028"), "Pattern character '.' should match line terminators in modified group");
+assert(re2.test("\u2029"), "Pattern character '.' should match line terminators in modified group");
+assert(re2.test("\uD800"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("\uDFFF"), "Pattern character '.' should match non-line terminators in modified group");
+
+var re3 = /(?s-:^.$)/;
+assert(re3.test("a"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re3.test("3"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re3.test("Ï€"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re3.test("\u2027"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re3.test("\u0085"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re3.test("\v"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re3.test("\f"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re3.test("\u180E"), "Pattern character '.' should match non-line terminators in modified group");
+assert(!re3.test("\u{10300}"), "Supplementary plane not matched by a single .");
+assert(re3.test("\n"), "Pattern character '.' should match line terminators in modified group");
+assert(re3.test("\r"), "Pattern character '.' should match line terminators in modified group");
+assert(re3.test("\u2028"), "Pattern character '.' should match line terminators in modified group");
+assert(re3.test("\u2029"), "Pattern character '.' should match line terminators in modified group");
+assert(re3.test("\uD800"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re3.test("\uDFFF"), "Pattern character '.' should match non-line terminators in modified group");
+
+var re4 = new RegExp("(?s-:^.$)");
+assert(re4.test("a"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re4.test("3"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re4.test("Ï€"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re4.test("\u2027"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re4.test("\u0085"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re4.test("\v"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re4.test("\f"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re4.test("\u180E"), "Pattern character '.' should match non-line terminators in modified group");
+assert(!re4.test("\u{10300}"), "Supplementary plane not matched by a single .");
+assert(re4.test("\n"), "Pattern character '.' should match line terminators in modified group");
+assert(re4.test("\r"), "Pattern character '.' should match line terminators in modified group");
+assert(re4.test("\u2028"), "Pattern character '.' should match line terminators in modified group");
+assert(re4.test("\u2029"), "Pattern character '.' should match line terminators in modified group");
+assert(re4.test("\uD800"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re4.test("\uDFFF"), "Pattern character '.' should match non-line terminators in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-backreferences.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-backreferences.js
new file mode 100644
index 0000000000..53e9ecb991
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-backreferences.js
@@ -0,0 +1,55 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Adding ignoreCase (`i`) modifier in group affects backreferences in group.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(a)(?i:\1)/;
+assert(!re1.test("AA"), "a should not match first A");
+assert(!re1.test("Aa"), "a should not match A");
+assert(re1.test("aa"), "a matches first a, so \\1 should match second a");
+assert(re1.test("aA"), "a matches a, so \\1 should match A (ignores case)");
+
+var re2 = /(a)(?i-:\1)/;
+assert(!re2.test("AA"), "a should not match first A");
+assert(!re2.test("Aa"), "a should not match A");
+assert(re2.test("aa"), "a matches first a, so \\1 should match second a");
+assert(re2.test("aA"), "a matches a, so \\1 should match A (ignores case)");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-characterClasses.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-characterClasses.js
new file mode 100644
index 0000000000..75c50a97fa
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-characterClasses.js
@@ -0,0 +1,67 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Adding ignoreCase (`i`) modifier in group affects character classes in group.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?i:[ab])c/;
+assert(re1.test("ac"), "[ab] should match a");
+assert(re1.test("Ac"), "[ab] should match A");
+assert(re1.test("bc"), "[ab] should match b");
+assert(re1.test("Bc"), "[ab] should match B");
+
+var re2 = /(?i-:[ab])c/;
+assert(re2.test("ac"), "[ab] should match a");
+assert(re2.test("Ac"), "[ab] should match A");
+assert(re2.test("bc"), "[ab] should match b");
+assert(re2.test("Bc"), "[ab] should match B");
+
+var re3 = /(?i:[^ab])c/;
+assert(!re3.test("ac"), "[^ab] should not match a");
+assert(!re3.test("Ac"), "[^ab] should not match A");
+assert(!re3.test("bc"), "[^ab] should not match b");
+assert(!re3.test("Bc"), "[^ab] should not match B");
+
+var re4 = /(?i-:[^ab])c/;
+assert(!re4.test("ac"), "[^ab] should not match a");
+assert(!re4.test("Ac"), "[^ab] should not match A");
+assert(!re4.test("bc"), "[^ab] should not match b");
+assert(!re4.test("Bc"), "[^ab] should not match B");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-characterEscapes.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-characterEscapes.js
new file mode 100644
index 0000000000..98fa435027
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-characterEscapes.js
@@ -0,0 +1,67 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Adding ignoreCase (`i`) modifier in group affects character escapes in group.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?i:\x61)b/;
+assert(re1.test("ab"), "\\x61 should match a");
+assert(re1.test("Ab"), "\\x61 should match A");
+
+var re2 = /(?i:\u0061)b/;
+assert(re2.test("ab"), "\\u0061 should match a");
+assert(re2.test("Ab"), "\\u0061 should match A");
+
+var re3 = /(?i:\u{0061})b/u;
+assert(re3.test("ab"), "\\u0061 should match a");
+assert(re3.test("Ab"), "\\u0061 should match A");
+
+var re4 = /(?i-:\x61)b/;
+assert(re4.test("ab"), "\\x61 should match a");
+assert(re4.test("Ab"), "\\x61 should match A");
+
+var re5 = /(?i-:\u0061)b/;
+assert(re5.test("ab"), "\\u0061 should match a");
+assert(re5.test("Ab"), "\\u0061 should match A");
+
+var re6 = /(?i-:\u{0061})b/u;
+assert(re6.test("ab"), "\\u0061 should match a");
+assert(re6.test("Ab"), "\\u0061 should match A");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-lower-b.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-lower-b.js
new file mode 100644
index 0000000000..a3f5b9f009
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-lower-b.js
@@ -0,0 +1,77 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Adding ignoreCase (`i`) modifier affects matching for `\b`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+ GetWordCharacters ( modifiers )
+ The abstract operation GetWordCharacters takes argument modifiers (a Modifiers Record) and returns a CharSet. It performs the following steps when called:
+
+ 1. Let wordCharacters be the mathematical set that is the union of all sixty-three characters in "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_" (letters, numbers, and U+005F (LOW LINE) in the Unicode Basic Latin block) and all characters c for which c is not in that set but Canonicalize(c, modifiers) is.
+ 2. Return wordCharacters.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?i:\b)/;
+assert(re1.test("A"), "\\b should match after A");
+assert(re1.test("a"), "\\b should match after a");
+assert(re1.test("z"), "\\b should match after z");
+assert(re1.test("Z"), "\\b should match after Z");
+
+var re2 = /(?i:\b)/u;
+assert(re2.test("A"), "\\b should match after A");
+assert(re2.test("a"), "\\b should match after a");
+assert(re2.test("z"), "\\b should match after z");
+assert(re2.test("Z"), "\\b should match after Z");
+assert(re2.test("\u017f"), "\\b should match after \u017f");
+assert(re2.test("\u212a"), "\\b should match after \u212a");
+
+var re3 = /(?i-:\b)/;
+assert(re3.test("A"), "\\b should match after A");
+assert(re3.test("a"), "\\b should match after a");
+assert(re3.test("z"), "\\b should match after z");
+assert(re3.test("Z"), "\\b should match after Z");
+
+var re4 = /(?i-:\b)/u;
+assert(re4.test("A"), "\\b should match after A");
+assert(re4.test("a"), "\\b should match after a");
+assert(re4.test("z"), "\\b should match after z");
+assert(re4.test("Z"), "\\b should match after Z");
+assert(re4.test("\u017f"), "\\b should match after \u017f");
+assert(re4.test("\u212a"), "\\b should match after \u212a");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-lower-p.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-lower-p.js
new file mode 100644
index 0000000000..41788082ee
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-lower-p.js
@@ -0,0 +1,61 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Adding ignoreCase (`i`) modifier affects matching for `\p{}`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+ GetWordCharacters ( modifiers )
+ The abstract operation GetWordCharacters takes argument modifiers (a Modifiers Record) and returns a CharSet. It performs the following steps when called:
+
+ 1. Let wordCharacters be the mathematical set that is the union of all sixty-three characters in "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_" (letters, numbers, and U+005F (LOW LINE) in the Unicode Basic Latin block) and all characters c for which c is not in that set but Canonicalize(c, modifiers) is.
+ 2. Return wordCharacters.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?i:\p{Lu})/u;
+assert(re1.test("A"), "\\p{Lu} should match A");
+assert(re1.test("a"), "\\p{Lu} should match a (ignores case)");
+assert(re1.test("Z"), "\\p{Lu} should match Z");
+assert(re1.test("z"), "\\p{Lu} should match z (ignores case)");
+
+var re2 = /(?i-:\p{Lu})/u;
+assert(re2.test("A"), "\\p{Lu} should match A");
+assert(re2.test("a"), "\\p{Lu} should match a (ignores case)");
+assert(re2.test("Z"), "\\p{Lu} should match Z");
+assert(re2.test("z"), "\\p{Lu} should match z (ignores case)");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-lower-w.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-lower-w.js
new file mode 100644
index 0000000000..324961d782
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-lower-w.js
@@ -0,0 +1,77 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Adding ignoreCase (`i`) modifier affects matching for `\w`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+ GetWordCharacters ( modifiers )
+ The abstract operation GetWordCharacters takes argument modifiers (a Modifiers Record) and returns a CharSet. It performs the following steps when called:
+
+ 1. Let wordCharacters be the mathematical set that is the union of all sixty-three characters in "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_" (letters, numbers, and U+005F (LOW LINE) in the Unicode Basic Latin block) and all characters c for which c is not in that set but Canonicalize(c, modifiers) is.
+ 2. Return wordCharacters.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?i:\w)/;
+assert(re1.test("A"), "\\w should match A");
+assert(re1.test("a"), "\\w should match a");
+assert(re1.test("z"), "\\w should match z");
+assert(re1.test("Z"), "\\w should match Z");
+
+var re2 = /(?i:\w)/u;
+assert(re2.test("A"), "\\w should match A");
+assert(re2.test("a"), "\\w should match a");
+assert(re2.test("z"), "\\w should match z");
+assert(re2.test("Z"), "\\w should match Z");
+assert(re2.test("\u017f"), "\\w should match \u017f");
+assert(re2.test("\u212a"), "\\w should match \u212a");
+
+var re3 = /(?i-:\w)/;
+assert(re3.test("A"), "\\w should match A");
+assert(re3.test("a"), "\\w should match a");
+assert(re3.test("z"), "\\w should match z");
+assert(re3.test("Z"), "\\w should match Z");
+
+var re4 = /(?i-:\w)/u;
+assert(re4.test("A"), "\\w should match A");
+assert(re4.test("a"), "\\w should match a");
+assert(re4.test("z"), "\\w should match z");
+assert(re4.test("Z"), "\\w should match Z");
+assert(re4.test("\u017f"), "\\w should match \u017f");
+assert(re4.test("\u212a"), "\\w should match \u212a");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-upper-b.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-upper-b.js
new file mode 100644
index 0000000000..ffb346277f
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-upper-b.js
@@ -0,0 +1,57 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Adding ignoreCase (`i`) modifier affects matching for `\B`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+ GetWordCharacters ( modifiers )
+ The abstract operation GetWordCharacters takes argument modifiers (a Modifiers Record) and returns a CharSet. It performs the following steps when called:
+
+ 1. Let wordCharacters be the mathematical set that is the union of all sixty-three characters in "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_" (letters, numbers, and U+005F (LOW LINE) in the Unicode Basic Latin block) and all characters c for which c is not in that set but Canonicalize(c, modifiers) is.
+ 2. Return wordCharacters.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?i:Z\B)/u;
+assert(re1.test("Z\u017f"), "\\B should match between Z and \u017f");
+assert(re1.test("Z\u212a"), "\\B should match between Z and \u212a");
+
+var re2 = /(?i-:Z\B)/u;
+assert(re2.test("Z\u017f"), "\\B should match between Z and \u017f");
+assert(re2.test("Z\u212a"), "\\B should match between Z and \u212a");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-upper-p.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-upper-p.js
new file mode 100644
index 0000000000..d5f30655cb
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-upper-p.js
@@ -0,0 +1,63 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Adding ignoreCase (`i`) modifier affects matching for `\P{}`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+ GetWordCharacters ( modifiers )
+ The abstract operation GetWordCharacters takes argument modifiers (a Modifiers Record) and returns a CharSet. It performs the following steps when called:
+
+ 1. Let wordCharacters be the mathematical set that is the union of all sixty-three characters in "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_" (letters, numbers, and U+005F (LOW LINE) in the Unicode Basic Latin block) and all characters c for which c is not in that set but Canonicalize(c, modifiers) is.
+ 2. Return wordCharacters.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?i:\P{Lu})/u;
+assert(re1.test("A"), "\\P{Lu} should match A (ignores case)");
+assert(re1.test("a"), "\\P{Lu} should match a");
+assert(re1.test("Z"), "\\P{Lu} should match Z (ignores case)");
+assert(re1.test("z"), "\\P{Lu} should match z");
+assert(re1.test("0"), "\\P{Lu} should match 0");
+
+var re2 = /(?i-:\P{Lu})/u;
+assert(re2.test("A"), "\\P{Lu} should match A (ignores case)");
+assert(re2.test("a"), "\\P{Lu} should match a");
+assert(re2.test("Z"), "\\P{Lu} should match Z (ignores case)");
+assert(re2.test("z"), "\\P{Lu} should match z");
+assert(re2.test("0"), "\\P{Lu} should match 0");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-upper-w.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-upper-w.js
new file mode 100644
index 0000000000..a0c527efa2
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-affects-slash-upper-w.js
@@ -0,0 +1,57 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Adding ignoreCase (`i`) modifier affects matching for `\W`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+ GetWordCharacters ( modifiers )
+ The abstract operation GetWordCharacters takes argument modifiers (a Modifiers Record) and returns a CharSet. It performs the following steps when called:
+
+ 1. Let wordCharacters be the mathematical set that is the union of all sixty-three characters in "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_" (letters, numbers, and U+005F (LOW LINE) in the Unicode Basic Latin block) and all characters c for which c is not in that set but Canonicalize(c, modifiers) is.
+ 2. Return wordCharacters.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?i:\W)/u;
+assert(!re1.test("\u017f"), "\\W should not match \u017f");
+assert(!re1.test("\u212a"), "\\W should not match \u212a");
+
+var re2 = /(?i-:\W)/u;
+assert(!re2.test("\u017f"), "\\W should not match \u017f");
+assert(!re2.test("\u212a"), "\\W should not match \u212a");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-does-not-affect-dotAll-flag.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-does-not-affect-dotAll-flag.js
new file mode 100644
index 0000000000..999598c492
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-does-not-affect-dotAll-flag.js
@@ -0,0 +1,67 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Adding ignoreCase (`i`) modifier in group should not affect dotAll (`s`) flag.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?i:.es)/;
+assert(re1.test("aes"), ". should match a in modified group");
+assert(re1.test("aeS"), ". should match a in modified group");
+assert(!re1.test("\nes"), ". should not match newline in modified group");
+assert(!re1.test("\neS"), ". should not match newline in modified group");
+
+var re2 = /(?i:.es)/s;
+assert(re2.test("aes"), ". should match a in modified group");
+assert(re2.test("aeS"), ". should match a in modified group");
+assert(re2.test("\nes"), ". should match newline in modified group");
+assert(re2.test("\neS"), ". should match newline in modified group");
+
+var re3 = /(?i-:.es)/;
+assert(re3.test("aes"), ". should match a in modified group");
+assert(re3.test("aeS"), ". should match a in modified group");
+assert(!re3.test("\nes"), ". should not match newline in modified group");
+assert(!re3.test("\neS"), ". should not match newline in modified group");
+
+var re4 = /(?i-:.es)/s;
+assert(re4.test("aes"), ". should match a in modified group");
+assert(re4.test("aeS"), ". should match a in modified group");
+assert(re4.test("\nes"), ". should match newline in modified group");
+assert(re4.test("\neS"), ". should match newline in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-does-not-affect-ignoreCase-property.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-does-not-affect-ignoreCase-property.js
new file mode 100644
index 0000000000..24da245c46
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-does-not-affect-ignoreCase-property.js
@@ -0,0 +1,55 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Adding ignoreCase (`i`) modifier does not affect RegExp instance `ignoreCase` property.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?i:)/;
+assert(!re1.ignoreCase, "RegExp instance ignoreCase property should not be set");
+
+var re2 = new RegExp("(?i:)");
+assert(!re2.ignoreCase, "RegExp instance ignoreCase property should not be set");
+
+var re3 = /(?i-:)/;
+assert(!re3.ignoreCase, "RegExp instance ignoreCase property should not be set");
+
+var re4 = new RegExp("(?i-:)");
+assert(!re4.ignoreCase, "RegExp instance ignoreCase property should not be set");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-does-not-affect-multiline-flag.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-does-not-affect-multiline-flag.js
new file mode 100644
index 0000000000..692cfd9f2f
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase-does-not-affect-multiline-flag.js
@@ -0,0 +1,67 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Adding ignoreCase (`i`) modifier in group should not affect multiline (`m`) flag.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?i:es$)/;
+assert(re1.test("es"), "s should match s in modified group");
+assert(re1.test("eS"), "s should match S in modified group");
+assert(!re1.test("es\nz"), "$ should not match newline in modified group");
+assert(!re1.test("eS\nz"), "$ should not match newline in modified group");
+
+var re2 = /(?i:es$)/m;
+assert(re2.test("es"), "s should match s in modified group");
+assert(re2.test("eS"), "s should match S in modified group");
+assert(re2.test("es\nz"), "$ should match newline in modified group");
+assert(re2.test("eS\nz"), "$ should match newline in modified group");
+
+var re3 = /(?i-:es$)/;
+assert(re3.test("es"), "s should match s in modified group");
+assert(re3.test("eS"), "s should match S in modified group");
+assert(!re3.test("es\nz"), "$ should not match newline in modified group");
+assert(!re3.test("eS\nz"), "$ should not match newline in modified group");
+
+var re4 = /(?i-:es$)/m;
+assert(re4.test("es"), "s should match s in modified group");
+assert(re4.test("eS"), "s should match S in modified group");
+assert(re4.test("es\nz"), "$ should match newline in modified group");
+assert(re4.test("eS\nz"), "$ should match newline in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase.js
new file mode 100644
index 0000000000..bd07e7aa22
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-ignoreCase.js
@@ -0,0 +1,47 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ ignoreCase (`i`) modifier can be added via `(?i:)` or `(?i-:)`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?i:a)b/;
+assert(!re1.test("AB"), "b should not match B in AB");
+assert(re1.test("Ab"), "a should match A in AB");
+assert(re1.test("ab"), "should match AB");
+
+var re2 = new RegExp("(?i:a)b");
+assert(!re2.test("AB"), "b should not match B in AB");
+assert(re2.test("Ab"), "a should match A in AB");
+assert(re2.test("ab"), "should match AB");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-multiline-does-not-affect-dotAll-flag.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-multiline-does-not-affect-dotAll-flag.js
new file mode 100644
index 0000000000..c065d293ac
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-multiline-does-not-affect-dotAll-flag.js
@@ -0,0 +1,59 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Adding multiline (`m`) modifier in group should not affect dotAll (`s`) flag.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?m:es.$)/;
+assert(re1.test("esz\n"), "$ should match newline in modified group");
+assert(!re1.test("es\n\n"), ". should not match newline in modified group");
+
+var re2 = /(?m:es.$)/s;
+assert(re2.test("esz\n"), "$ should match newline in modified group");
+assert(re2.test("es\n\n"), ". should match newline in modified group");
+
+var re3 = /(?m-:es.$)/;
+assert(re3.test("esz\n"), "$ should match newline in modified group");
+assert(!re3.test("es\n\n"), ". should not match newline in modified group");
+
+var re4 = /(?m-:es.$)/s;
+assert(re4.test("esz\n"), "$ should match newline in modified group");
+assert(re4.test("es\n\n"), ". should match newline in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-multiline-does-not-affect-ignoreCase-flag.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-multiline-does-not-affect-ignoreCase-flag.js
new file mode 100644
index 0000000000..b8b33e9c22
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-multiline-does-not-affect-ignoreCase-flag.js
@@ -0,0 +1,67 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Adding multiline (`m`) modifier in group should not affect ignoreCase (`i`) flag.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?m:es$)/;
+assert(re1.test("es"), "s should match s in modified group");
+assert(!re1.test("eS"), "s should not match S in modified group");
+assert(re1.test("es\nz"), "$ should match newline in modified group");
+assert(!re1.test("eS\nz"), "s should not match S in modified group");
+
+var re2 = /(?m:es$)/i;
+assert(re2.test("es"), "s should match s in modified group");
+assert(re2.test("eS"), "s should match S in modified group");
+assert(re2.test("es\nz"), "$ should match newline in modified group");
+assert(re2.test("eS\nz"), "$ should match newline in modified group");
+
+var re3 = /(?m-:es$)/;
+assert(re3.test("es"), "s should match s in modified group");
+assert(!re3.test("eS"), "s should not match S in modified group");
+assert(re3.test("es\nz"), "$ should match newline in modified group");
+assert(!re3.test("eS\nz"), "s should not match S in modified group");
+
+var re4 = /(?m-:es$)/i;
+assert(re4.test("es"), "s should match s in modified group");
+assert(re4.test("eS"), "s should match S in modified group");
+assert(re4.test("es\nz"), "$ should match newline in modified group");
+assert(re4.test("eS\nz"), "$ should match newline in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-multiline-does-not-affect-multiline-property.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-multiline-does-not-affect-multiline-property.js
new file mode 100644
index 0000000000..3b960f5a6c
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-multiline-does-not-affect-multiline-property.js
@@ -0,0 +1,49 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Adding multiline (`m`) modifier does not affect RegExp instance `multiline` property.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?m:)/;
+assert(!re1.multiline, "RegExp instance multiline flag should not be set");
+
+var re2 = new RegExp("(?m:)");
+assert(!re2.multiline, "RegExp instance multiline flag should not be set");
+
+var re3 = /(?m-:)/;
+assert(!re3.multiline, "RegExp instance multiline flag should not be set");
+
+var re4 = new RegExp("(?m-:)");
+assert(!re4.multiline, "RegExp instance multiline flag should not be set");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-multiline.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-multiline.js
new file mode 100644
index 0000000000..ee1d0a65cc
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-multiline.js
@@ -0,0 +1,49 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ multiline (`m`) modifier can be added via `(?m:)` or `(?m-:)`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?m:es$)/;
+assert(re1.test("es\ns"), "$ should match newline in modified group");
+
+var re2 = new RegExp("(?m:es$)");
+assert(re2.test("es\ns"), "$ should match newline in modified group");
+
+var re3 = /(?m-:es$)/;
+assert(re3.test("es\ns"), "$ should match newline in modified group");
+
+var re4 = new RegExp("(?m-:es$)");
+assert(re4.test("es\ns"), "$ should match newline in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-remove-modifiers.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-remove-modifiers.js
new file mode 100644
index 0000000000..68e4761cfc
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/add-remove-modifiers.js
@@ -0,0 +1,45 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Modifiers can be both added and removed via `(?ims-ims:)`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?m-i:^a$)/i;
+assert(!re1.test("A\n"), "Should not match 'A\\n'");
+assert(re1.test("a\n"), "Should match 'a\\n'");
+
+var re2 = new RegExp("(?m-i:^a$)", "i");
+assert(!re2.test("A\n"), "Should not match 'A\\n'");
+assert(re2.test("a\n"), "Should match 'a\\n'");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/browser.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/browser.js
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/browser.js
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/changing-dotAll-flag-does-not-affect-dotAll-modifier.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/changing-dotAll-flag-does-not-affect-dotAll-modifier.js
new file mode 100644
index 0000000000..b275621155
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/changing-dotAll-flag-does-not-affect-dotAll-modifier.js
@@ -0,0 +1,77 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ New dotAll (`s`) flag from RegExp constructor does not affect dotAll modifier in group.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = new RegExp(/(?s:^.$)/s, "");
+assert(re1.test("a"), "Pattern character '.' still should match non-line terminators in modified group");
+assert(re1.test("3"), "Pattern character '.' still should match non-line terminators in modified group");
+assert(re1.test("Ï€"), "Pattern character '.' still should match non-line terminators in modified group");
+assert(re1.test("\u2027"), "Pattern character '.' still should match non-line terminators in modified group");
+assert(re1.test("\u0085"), "Pattern character '.' still should match non-line terminators in modified group");
+assert(re1.test("\v"), "Pattern character '.' still should match mon-line terminators in modified group");
+assert(re1.test("\f"), "Pattern character '.' still should match mon-line terminators in modified group");
+assert(re1.test("\u180E"), "Pattern character '.' still should match non-line terminators in modified group");
+assert(!re1.test("\u{10300}"), "Supplementary plane still not matched by a single .");
+assert(re1.test("\n"), "Pattern character '.' still should match line terminators in modified group");
+assert(re1.test("\r"), "Pattern character '.' still should match line terminators in modified group");
+assert(re1.test("\u2028"), "Pattern character '.' still should match line terminators in modified group");
+assert(re1.test("\u2029"), "Pattern character '.' still should match line terminators in modified group");
+assert(re1.test("\uD800"), "Pattern character '.' still should match non-line terminators in modified group");
+assert(re1.test("\uDFFF"), "Pattern character '.' still should match non-line terminators in modified group");
+
+var re2 = new RegExp(/(?-s:^.$)/, "s");
+assert(re2.test("a"), "Pattern character '.' still should match non-line terminators in modified group");
+assert(re2.test("3"), "Pattern character '.' still should match non-line terminators in modified group");
+assert(re2.test("Ï€"), "Pattern character '.' still should match non-line terminators in modified group");
+assert(re2.test("\u2027"), "Pattern character '.' still should match non-line terminators in modified group");
+assert(re2.test("\u0085"), "Pattern character '.' still should match non-line terminators in modified group");
+assert(re2.test("\v"), "Pattern character '.' still should match mon-line terminators in modified group");
+assert(re2.test("\f"), "Pattern character '.' still should match mon-line terminators in modified group");
+assert(re2.test("\u180E"), "Pattern character '.' still should match non-line terminators in modified group");
+assert(!re2.test("\u{10300}"), "Supplementary plane still not matched by a single .");
+assert(!re2.test("\n"), "Pattern character '.' still should not match '\\n' in modified group");
+assert(!re2.test("\r"), "Pattern character '.' still should not match '\\r' in modified group");
+assert(!re2.test("\u2028"), "Pattern character '.' still should not match '\\u2028' in modified group");
+assert(!re2.test("\u2029"), "Pattern character '.' still should not match '\\u2029' in modified group");
+assert(re2.test("\uD800"), "Pattern character '.' still should match non-line terminators in modified group");
+assert(re2.test("\uDFFF"), "Pattern character '.' still should match non-line terminators in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/changing-ignoreCase-flag-does-not-affect-ignoreCase-modifier.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/changing-ignoreCase-flag-does-not-affect-ignoreCase-modifier.js
new file mode 100644
index 0000000000..8db72f0742
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/changing-ignoreCase-flag-does-not-affect-ignoreCase-modifier.js
@@ -0,0 +1,55 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ New ignoreCase (`i`) flag from RegExp constructor does not affect ignoreCase modifier in group.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = new RegExp(/(?i:aB)/i, "");
+assert(re1.test("AB"), "still should ignore case in modified group");
+assert(re1.test("Ab"), "still should ignore case in modified group");
+assert(re1.test("aB"), "still should ignore case in modified group");
+assert(re1.test("ab"), "still should ignore case in modified group");
+
+var re2 = new RegExp(/(?-i:aB)/, "i");
+assert(!re2.test("AB"), "still should preserve case in modified group");
+assert(!re2.test("Ab"), "still should preserve case in modified group");
+assert(!re2.test("ab"), "still should preserve case in modified group");
+assert(re2.test("aB"), "still should preserve case in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/changing-multiline-flag-does-not-affect-multiline-modifier.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/changing-multiline-flag-does-not-affect-multiline-modifier.js
new file mode 100644
index 0000000000..b890200b21
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/changing-multiline-flag-does-not-affect-multiline-modifier.js
@@ -0,0 +1,51 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ New multiline (`m`) flag from RegExp constructor does not affect multiline modifier in group.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = new RegExp(/(?m:es$)/m, "");
+assert(re1.test("es"), "$ still should match end of input in modified group");
+assert(re1.test("es\ns"), "$ still should match newline in modified group");
+
+var re2 = new RegExp(/^(?-m:es$)/, "m");
+assert(re2.test("es"), "$ still should match end of input in modified group");
+assert(!re2.test("es\ns"), "$ still should not match newline in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nested-add-remove-modifiers.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nested-add-remove-modifiers.js
new file mode 100644
index 0000000000..f2e1052643
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nested-add-remove-modifiers.js
@@ -0,0 +1,45 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Modifiers can be nested.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?m:^(?-i:a)$)/i;
+assert(!re1.test("A\n"), "Should not match 'A\\n'");
+assert(re1.test("a\n"), "Should match 'a\\n'");
+
+var re2 = new RegExp("(?m:^(?-i:a)$)", "i");
+assert(!re2.test("A\n"), "Should not match 'A\\n'");
+assert(re2.test("a\n"), "Should match 'a\\n'");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-add-dotAll-within-remove-dotAll.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-add-dotAll-within-remove-dotAll.js
new file mode 100644
index 0000000000..26b7d760b4
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-add-dotAll-within-remove-dotAll.js
@@ -0,0 +1,71 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Can add multiline (`m`) modifier for group nested within a group that removes multiline modifier.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-s:(?s:^.$))/s;
+assert(re1.test("a"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("3"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("Ï€"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("\u2027"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("\u0085"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("\v"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re1.test("\f"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re1.test("\u180E"), "Pattern character '.' should match non-line terminators in modified group");
+assert(!re1.test("\u{10300}"), "Supplementary plane not matched by a single .");
+assert(re1.test("\n"), "Pattern character '.' should match line terminators in modified group");
+assert(re1.test("\r"), "Pattern character '.' should match line terminators in modified group");
+assert(re1.test("\u2028"), "Pattern character '.' should match line terminators in modified group");
+assert(re1.test("\u2029"), "Pattern character '.' should match line terminators in modified group");
+assert(re1.test("\uD800"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("\uDFFF"), "Pattern character '.' should match non-line terminators in modified group");
+
+var re2 = /(?-s:(?s-:^.$))/s;
+assert(re2.test("a"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("3"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("Ï€"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("\u2027"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("\u0085"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("\v"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re2.test("\f"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re2.test("\u180E"), "Pattern character '.' should match non-line terminators in modified group");
+assert(!re2.test("\u{10300}"), "Supplementary plane not matched by a single .");
+assert(re2.test("\n"), "Pattern character '.' should match line terminators in modified group");
+assert(re2.test("\r"), "Pattern character '.' should match line terminators in modified group");
+assert(re2.test("\u2028"), "Pattern character '.' should match line terminators in modified group");
+assert(re2.test("\u2029"), "Pattern character '.' should match line terminators in modified group");
+assert(re2.test("\uD800"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("\uDFFF"), "Pattern character '.' should match non-line terminators in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-add-ignoreCase-within-remove-ignoreCase.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-add-ignoreCase-within-remove-ignoreCase.js
new file mode 100644
index 0000000000..04103802c6
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-add-ignoreCase-within-remove-ignoreCase.js
@@ -0,0 +1,45 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Can add ignoreCase (`i`) modifier for group nested within a group that removes ignoreCase modifier.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-i:a(?i:b))c/i;
+assert(!re1.test("ABC"), "a should not match A in ABC");
+assert(!re1.test("ABc"), "a should not match A in ABc");
+assert(!re1.test("Abc"), "a should not match A in Abc");
+assert(re1.test("aBc"), "b should match B in aBc");
+assert(re1.test("abC"), "c should match C in abC");
+assert(re1.test("abc"), "should match abc");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-add-multiline-within-remove-multiline.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-add-multiline-within-remove-multiline.js
new file mode 100644
index 0000000000..dcf7504067
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-add-multiline-within-remove-multiline.js
@@ -0,0 +1,47 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Can add multiline (`m`) modifier for group nested within a group that removes multiline modifier.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-m:es(?m:$)|js$)/m;
+assert(re1.test("es\ns"), "$ should match newline in modified group");
+assert(re1.test("js"), "$ should match end of input in nested modified group");
+assert(!re1.test("js\ns"), "$ should not match newline in nested modified group");
+
+var re2 = /(?-m:es(?m-:$)|js$)/m;
+assert(re2.test("es\ns"), "$ should match newline in modified group");
+assert(re2.test("js"), "$ should match end of input in nested modified group");
+assert(!re2.test("js\ns"), "$ should not match newline in nested modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-remove-dotAll-within-add-dotAll.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-remove-dotAll-within-add-dotAll.js
new file mode 100644
index 0000000000..e62290bedd
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-remove-dotAll-within-add-dotAll.js
@@ -0,0 +1,71 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Can remove multiline (`m`) modifier for group nested within a group that adds multiline modifier.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?s:(?-s:^.$))/;
+assert(re1.test("a"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("3"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("Ï€"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("\u2027"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("\u0085"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("\v"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re1.test("\f"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re1.test("\u180E"), "Pattern character '.' should match non-line terminators in modified group");
+assert(!re1.test("\u{10300}"), "Supplementary plane not matched by a single .");
+assert(!re1.test("\n"), "Pattern character '.' should not match '\\n' in modified group");
+assert(!re1.test("\r"), "Pattern character '.' should not match '\\r' in modified group");
+assert(!re1.test("\u2028"), "Pattern character '.' should not match '\\u2028' in modified group");
+assert(!re1.test("\u2029"), "Pattern character '.' should not match '\\u2029' in modified group");
+assert(re1.test("\uD800"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("\uDFFF"), "Pattern character '.' should match non-line terminators in modified group");
+
+var re2 = /(?s-:(?-s:^.$))/;
+assert(re2.test("a"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("3"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("Ï€"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("\u2027"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("\u0085"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("\v"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re2.test("\f"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re2.test("\u180E"), "Pattern character '.' should match non-line terminators in modified group");
+assert(!re2.test("\u{10300}"), "Supplementary plane not matched by a single .");
+assert(!re2.test("\n"), "Pattern character '.' should not match '\\n' in modified group");
+assert(!re2.test("\r"), "Pattern character '.' should not match '\\r' in modified group");
+assert(!re2.test("\u2028"), "Pattern character '.' should not match '\\u2028' in modified group");
+assert(!re2.test("\u2029"), "Pattern character '.' should not match '\\u2029' in modified group");
+assert(re2.test("\uD800"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("\uDFFF"), "Pattern character '.' should match non-line terminators in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-remove-ignoreCase-within-add-ignoreCase.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-remove-ignoreCase-within-add-ignoreCase.js
new file mode 100644
index 0000000000..6b260ab2cc
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-remove-ignoreCase-within-add-ignoreCase.js
@@ -0,0 +1,45 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Can remove ignoreCase (`i`) modifier for group nested within a group that adds ignoreCase modifier.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-i:a(?i:b))c/i;
+assert(!re1.test("ABC"), "a should not match A in ABC");
+assert(!re1.test("ABc"), "a should not match A in ABc");
+assert(!re1.test("Abc"), "a should not match A in Abc");
+assert(re1.test("aBc"), "b should match B in aBc");
+assert(re1.test("abC"), "c should match C in abC");
+assert(re1.test("abc"), "should match abc");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-remove-multiline-within-add-multiline.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-remove-multiline-within-add-multiline.js
new file mode 100644
index 0000000000..b7aa1b9895
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/nesting-remove-multiline-within-add-multiline.js
@@ -0,0 +1,47 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Can remove multiline (`m`) modifier for group nested within a group that adds multiline modifier.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?m:es$|(?-m:js$))/;
+assert(re1.test("es\ns"), "first $ should match newline in modified group");
+assert(re1.test("js"), "second $ should match end of input in nested modified group");
+assert(!re1.test("js\ns"), "second $ should not match newline in nested modified group");
+
+var re2 = /(?m-:es$|(?-m:js$))/;
+assert(re2.test("es\ns"), "first $ should match newline in modified group");
+assert(re2.test("js"), "second $ should match end of input in nested modified group");
+assert(!re2.test("js\ns"), "second $ should not match newline in nested modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-dotAll-does-not-affect-dotAll-property.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-dotAll-does-not-affect-dotAll-property.js
new file mode 100644
index 0000000000..23e607be8d
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-dotAll-does-not-affect-dotAll-property.js
@@ -0,0 +1,43 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Removing dotAll (`s`) modifier does not affect RegExp instance `dotAll` property.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-s:^.$)/s;
+assert(re1.dotAll, "RegExp instance dotAll flag should still be set");
+
+var re2 = new RegExp("(?-s:^.$)", "s");
+assert(re2.dotAll, "RegExp instance dotAll flag should still be set");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-dotAll-does-not-affect-ignoreCase-flag.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-dotAll-does-not-affect-ignoreCase-flag.js
new file mode 100644
index 0000000000..2ccd21b4e2
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-dotAll-does-not-affect-ignoreCase-flag.js
@@ -0,0 +1,49 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Removing dotAll (`s`) modifier in group should not affect ignoreCase (`i`) flag.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-s:.es)/s;
+assert(re1.test("aes"), "s should match s in modified group");
+assert(!re1.test("aeS"), "s should not match S in modified group");
+assert(!re1.test("\nes"), ". should not match newline in modified group");
+assert(!re1.test("\neS"), ". should not match newline in modified group");
+
+var re2 = /(?-s:.es)/si;
+assert(re2.test("aes"), "s should match s in modified group");
+assert(re2.test("aeS"), "s should match S in modified group");
+assert(!re2.test("\nes"), ". should not match newline in modified group");
+assert(!re2.test("\neS"), ". should not match newline in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-dotAll-does-not-affect-multiline-flag.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-dotAll-does-not-affect-multiline-flag.js
new file mode 100644
index 0000000000..1f73afc52c
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-dotAll-does-not-affect-multiline-flag.js
@@ -0,0 +1,49 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Removing dotAll (`s`) modifier in group should not affect multiline (`m`) flag.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-s:.es$)/s;
+assert(re1.test("aes"), ". should match a in modified group");
+assert(!re1.test("aes\nz"), "$ should not match newline in modified group");
+assert(!re1.test("\nes"), ". should not match newline in modified group");
+assert(!re1.test("\nes\nz"), "$ should not match newline in modified group");
+
+var re2 = /(?-s:.es$)/sm;
+assert(re2.test("aes"), ". should match a in modified group");
+assert(re2.test("aes\nz"), "$ should match newline in modified group");
+assert(!re2.test("\nes"), ". should not match newline in modified group");
+assert(!re2.test("\nes\nz"), ". should not match newline in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-dotAll.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-dotAll.js
new file mode 100644
index 0000000000..8abed77808
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-dotAll.js
@@ -0,0 +1,71 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ dotAll (`s`) modifier can be added via `(?s:)` or `(?s-:)`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-s:^.$)/s;
+assert(re1.test("a"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("3"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("Ï€"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("\u2027"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("\u0085"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("\v"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re1.test("\f"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re1.test("\u180E"), "Pattern character '.' should match non-line terminators in modified group");
+assert(!re1.test("\u{10300}"), "Supplementary plane not matched by a single .");
+assert(!re1.test("\n"), "Pattern character '.' should not match '\\n' in modified group");
+assert(!re1.test("\r"), "Pattern character '.' should not match '\\r' in modified group");
+assert(!re1.test("\u2028"), "Pattern character '.' should not match '\\u2028' in modified group");
+assert(!re1.test("\u2029"), "Pattern character '.' should not match '\\u2029' in modified group");
+assert(re1.test("\uD800"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re1.test("\uDFFF"), "Pattern character '.' should match non-line terminators in modified group");
+
+var re2 = new RegExp("(?-s:^.$)", "s");
+assert(re2.test("a"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("3"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("Ï€"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("\u2027"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("\u0085"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("\v"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re2.test("\f"), "Pattern character '.' should match mon-line terminators in modified group");
+assert(re2.test("\u180E"), "Pattern character '.' should match non-line terminators in modified group");
+assert(!re2.test("\u{10300}"), "Supplementary plane not matched by a single .");
+assert(!re2.test("\n"), "Pattern character '.' should not match '\\n' in modified group");
+assert(!re2.test("\r"), "Pattern character '.' should not match '\\r' in modified group");
+assert(!re2.test("\u2028"), "Pattern character '.' should not match '\\u2028' in modified group");
+assert(!re2.test("\u2029"), "Pattern character '.' should not match '\\u2029' in modified group");
+assert(re2.test("\uD800"), "Pattern character '.' should match non-line terminators in modified group");
+assert(re2.test("\uDFFF"), "Pattern character '.' should match non-line terminators in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-backreferences.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-backreferences.js
new file mode 100644
index 0000000000..1d1767651b
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-backreferences.js
@@ -0,0 +1,43 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Removing ignoreCase (`i`) modifier in group affects backreferences in group.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(a)(?-i:\1)/i;
+assert(re1.test("AA"), "a matches first A, so \\1 should match second A");
+assert(!re1.test("aA"), "a matches a, so \\1 should not match A (preserves case)");
+assert(!re1.test("Aa"), "a matches A, so \\1 should not match a (preserves case)");
+assert(re1.test("aa"), "a matches first a, so \\1 should match second a");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-characterClasses.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-characterClasses.js
new file mode 100644
index 0000000000..fbe2d16256
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-characterClasses.js
@@ -0,0 +1,55 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Removing ignoreCase (`i`) modifier in group affects character classes in group.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-i:[ab])c/i;
+assert(re1.test("ac"), "[ab] should match a");
+assert(!re1.test("Ac"), "[ab] should not match A");
+assert(re1.test("bc"), "[ab] should match b");
+assert(!re1.test("Bc"), "[ab] should not match B");
+
+var re2 = /(?-i:[^ab])c/i;
+assert(!re2.test("ac"), "[^ab] should not match a");
+assert(re2.test("Ac"), "[^ab] should match A");
+assert(!re2.test("bc"), "[^ab] should not match b");
+assert(re2.test("Bc"), "[^ab] should match B");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-characterEscapes.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-characterEscapes.js
new file mode 100644
index 0000000000..1edb2d2124
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-characterEscapes.js
@@ -0,0 +1,52 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Removing ignoreCase (`i`) modifier in group affects character escapes in group.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-i:\x61)b/i;
+assert(re1.test("ab"), "\\x61 should match a");
+assert(re1.test("aB"), "b should match B");
+assert(!re1.test("Ab"), "\\x61 should not match A");
+
+var re2 = /(?-i:\u0061)b/i;
+assert(re2.test("ab"), "\\u0061 should match a");
+assert(re2.test("aB"), "b should match B");
+assert(!re2.test("Ab"), "\\u0061 should not match A");
+
+var re3 = /(?-i:\u{0061})b/iu;
+assert(re3.test("ab"), "\\u0061 should match a");
+assert(re3.test("aB"), "b should match B");
+assert(!re3.test("Ab"), "\\u0061 should not match A");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-lower-b.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-lower-b.js
new file mode 100644
index 0000000000..b8b51d794b
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-lower-b.js
@@ -0,0 +1,53 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Removing ignoreCase (`i`) modifier affects matching for `\b`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+ GetWordCharacters ( modifiers )
+ The abstract operation GetWordCharacters takes argument modifiers (a Modifiers Record) and returns a CharSet. It performs the following steps when called:
+
+ 1. Let wordCharacters be the mathematical set that is the union of all sixty-three characters in "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_" (letters, numbers, and U+005F (LOW LINE) in the Unicode Basic Latin block) and all characters c for which c is not in that set but Canonicalize(c, modifiers) is.
+ 2. Return wordCharacters.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-i:\b)/ui;
+assert(!re1.test("\u017f"), "\\b should not match after \u017f");
+assert(!re1.test("\u212a"), "\\b should not match after \u212a");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-lower-p.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-lower-p.js
new file mode 100644
index 0000000000..2a0167b689
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-lower-p.js
@@ -0,0 +1,55 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Removing ignoreCase (`i`) modifier affects matching for `\p{}`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+ GetWordCharacters ( modifiers )
+ The abstract operation GetWordCharacters takes argument modifiers (a Modifiers Record) and returns a CharSet. It performs the following steps when called:
+
+ 1. Let wordCharacters be the mathematical set that is the union of all sixty-three characters in "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_" (letters, numbers, and U+005F (LOW LINE) in the Unicode Basic Latin block) and all characters c for which c is not in that set but Canonicalize(c, modifiers) is.
+ 2. Return wordCharacters.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-i:\p{Lu})/ui;
+assert(re1.test("A"), "\\p{Lu} should match A");
+assert(!re1.test("a"), "\\p{Lu} should not match a");
+assert(re1.test("Z"), "\\p{Lu} should match Z");
+assert(!re1.test("z"), "\\p{Lu} should not match z");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-lower-w.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-lower-w.js
new file mode 100644
index 0000000000..e8686f2e9d
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-lower-w.js
@@ -0,0 +1,53 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Removing ignoreCase (`i`) modifier affects matching for `\w`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+ GetWordCharacters ( modifiers )
+ The abstract operation GetWordCharacters takes argument modifiers (a Modifiers Record) and returns a CharSet. It performs the following steps when called:
+
+ 1. Let wordCharacters be the mathematical set that is the union of all sixty-three characters in "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_" (letters, numbers, and U+005F (LOW LINE) in the Unicode Basic Latin block) and all characters c for which c is not in that set but Canonicalize(c, modifiers) is.
+ 2. Return wordCharacters.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-i:\w)/ui;
+assert(!re1.test("\u017f"), "\\w should not match \u017f");
+assert(!re1.test("\u212a"), "\\w should not match \u212a");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-upper-b.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-upper-b.js
new file mode 100644
index 0000000000..9ed611bbe9
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-upper-b.js
@@ -0,0 +1,53 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Removing ignoreCase (`i`) modifier affects matching for `\B`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+ GetWordCharacters ( modifiers )
+ The abstract operation GetWordCharacters takes argument modifiers (a Modifiers Record) and returns a CharSet. It performs the following steps when called:
+
+ 1. Let wordCharacters be the mathematical set that is the union of all sixty-three characters in "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_" (letters, numbers, and U+005F (LOW LINE) in the Unicode Basic Latin block) and all characters c for which c is not in that set but Canonicalize(c, modifiers) is.
+ 2. Return wordCharacters.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-i:Z\B)/ui;
+assert(!re1.test("Z\u017f"), "\\B should not match between Z and \u017f");
+assert(!re1.test("Z\u212a"), "\\B should not match between Z and \u212a");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-upper-p.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-upper-p.js
new file mode 100644
index 0000000000..c764e66610
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-upper-p.js
@@ -0,0 +1,56 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Removing ignoreCase (`i`) modifier affects matching for `\P{}`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+ GetWordCharacters ( modifiers )
+ The abstract operation GetWordCharacters takes argument modifiers (a Modifiers Record) and returns a CharSet. It performs the following steps when called:
+
+ 1. Let wordCharacters be the mathematical set that is the union of all sixty-three characters in "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_" (letters, numbers, and U+005F (LOW LINE) in the Unicode Basic Latin block) and all characters c for which c is not in that set but Canonicalize(c, modifiers) is.
+ 2. Return wordCharacters.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-i:\P{Lu})/ui;
+assert(!re1.test("A"), "\\P{Lu} should not match A");
+assert(re1.test("a"), "\\P{Lu} should match a");
+assert(!re1.test("Z"), "\\P{Lu} should not match Z");
+assert(re1.test("z"), "\\P{Lu} should match z");
+assert(re1.test("0"), "\\P{Lu} should match 0");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-upper-w.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-upper-w.js
new file mode 100644
index 0000000000..fe2a24a2a2
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-affects-slash-upper-w.js
@@ -0,0 +1,53 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Removing ignoreCase (`i`) modifier affects matching for `\W`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+ GetWordCharacters ( modifiers )
+ The abstract operation GetWordCharacters takes argument modifiers (a Modifiers Record) and returns a CharSet. It performs the following steps when called:
+
+ 1. Let wordCharacters be the mathematical set that is the union of all sixty-three characters in "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_" (letters, numbers, and U+005F (LOW LINE) in the Unicode Basic Latin block) and all characters c for which c is not in that set but Canonicalize(c, modifiers) is.
+ 2. Return wordCharacters.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-i:\W)/ui;
+assert(re1.test("\u017f"), "\\W should match \u017f");
+assert(re1.test("\u212a"), "\\W should match \u212a");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-does-not-affect-dotAll-flag.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-does-not-affect-dotAll-flag.js
new file mode 100644
index 0000000000..f66c8f0857
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-does-not-affect-dotAll-flag.js
@@ -0,0 +1,49 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Removing ignoreCase (`i`) modifier in group should not affect dotAll (`s`) flag.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-i:.es)/i;
+assert(re1.test("aes"), "s should match s in modified group");
+assert(!re1.test("aeS"), "s should not match S in modified group");
+assert(!re1.test("\nes"), ". should not match newline in modified group");
+assert(!re1.test("\neS"), ". should not match newline in modified group");
+
+var re2 = /(?-i:.es)/is;
+assert(re2.test("aes"), "s should match s in modified group");
+assert(!re2.test("aeS"), "s should not match S in modified group");
+assert(re2.test("\nes"), ". should match newline in modified group");
+assert(!re2.test("\neS"), "s should not match S in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-does-not-affect-ignoreCase-property.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-does-not-affect-ignoreCase-property.js
new file mode 100644
index 0000000000..4b68807d35
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-does-not-affect-ignoreCase-property.js
@@ -0,0 +1,49 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Removing ignoreCase (`i`) modifier does not affect RegExp instance `ignoreCase` property.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-i:)/i;
+assert(re1.ignoreCase, "RegExp instance ignoreCase property should still be set");
+
+var re2 = new RegExp("(?-i:)", "i");
+assert(re2.ignoreCase, "RegExp instance ignoreCase property should still be set");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-does-not-affect-multiline-flag.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-does-not-affect-multiline-flag.js
new file mode 100644
index 0000000000..26bc3278b1
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase-does-not-affect-multiline-flag.js
@@ -0,0 +1,49 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Removing ignoreCase (`i`) modifier in group should not affect multiline (`m`) flag.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-i:es$)/i;
+assert(re1.test("es"), "s should match s in modified group");
+assert(!re1.test("eS"), "s should not match S in modified group");
+assert(!re1.test("es\nz"), "$ should not match newline in modified group");
+assert(!re1.test("eS\nz"), "s should not match S in modified group");
+
+var re2 = /(?-i:es$)/im;
+assert(re2.test("es"), "s should match s in modified group");
+assert(!re2.test("eS"), "s should not match S in modified group");
+assert(re2.test("es\nz"), "$ should match newline in modified group");
+assert(!re2.test("eS\nz"), "s should not match S in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase.js
new file mode 100644
index 0000000000..87fa013049
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-ignoreCase.js
@@ -0,0 +1,49 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ ignoreCase (`i`) modifier can be removed via `(?i:)` or `(?i-:)`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-i:fo)o/i;
+assert(!re1.test("FOO"), "Pattern should not match as modified group does not ignore case");
+assert(!re1.test("FOo"), "Pattern should not match as modified group does not ignore case");
+assert(re1.test("foo"), "Pattern should not ignore case in modified group");
+assert(re1.test("foO"), "Pattern should not ignore case in modified group");
+
+var re2 = new RegExp("(?-i:fo)o", "i");
+assert(!re2.test("FOO"), "Pattern should not match as modified group does not ignore case");
+assert(!re2.test("FOo"), "Pattern should not match as modified group does not ignore case");
+assert(re2.test("foo"), "Pattern should not ignore case in modified group");
+assert(re2.test("foO"), "Pattern should not ignore case in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-multiline-does-not-affect-dotAll-flag.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-multiline-does-not-affect-dotAll-flag.js
new file mode 100644
index 0000000000..b28b545cc0
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-multiline-does-not-affect-dotAll-flag.js
@@ -0,0 +1,49 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Removing multiline (`m`) modifier in group should not affect dotAll (`s`) flag.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-m:es.$)/m;
+assert(re1.test("esz"), ". should match z in modified group");
+assert(!re1.test("es\n"), ". should not match newline in modified group");
+assert(!re1.test("esz\n"), "$ should not match newline in modified group");
+assert(!re1.test("es\n\n"), "$ should not match newline in modified group");
+
+var re2 = /(?-m:es.$)/ms;
+assert(re2.test("esz"), ". should match z in modified group");
+assert(re2.test("es\n"), ". should match newline in modified group");
+assert(!re2.test("esz\n"), "$ should not match newline in modified group");
+assert(!re2.test("es\n\n"), "$ should not match newline in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-multiline-does-not-affect-ignoreCase-flag.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-multiline-does-not-affect-ignoreCase-flag.js
new file mode 100644
index 0000000000..a482105dee
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-multiline-does-not-affect-ignoreCase-flag.js
@@ -0,0 +1,49 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Removing multiline (`m`) modifier in group should not affect ignoreCase (`i`) flag.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-m:es$)/m;
+assert(re1.test("es"), "s should match s in modified group");
+assert(!re1.test("eS"), "s should not match S in modified group");
+assert(!re1.test("es\nz"), "$ should not match newline in modified group");
+assert(!re1.test("eS\nz"), "s should not match S in modified group");
+
+var re2 = /(?-m:es$)/mi;
+assert(re2.test("es"), "s should match s in modified group");
+assert(re2.test("eS"), "s should match S in modified group");
+assert(!re2.test("es\nz"), "$ should not match newline in modified group");
+assert(!re2.test("eS\nz"), "$ should not match newline in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-multiline-does-not-affect-multiline-property.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-multiline-does-not-affect-multiline-property.js
new file mode 100644
index 0000000000..885ae9b242
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-multiline-does-not-affect-multiline-property.js
@@ -0,0 +1,43 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Removing multiline (`m`) modifier does not affect RegExp instance `multiline` property.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /(?-m:)/m;
+assert(re1.multiline, "RegExp instance multiline flag should still be set");
+
+var re2 = new RegExp("(?-m:)", "m");
+assert(re2.multiline, "RegExp instance multiline flag should still be set");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-multiline.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-multiline.js
new file mode 100644
index 0000000000..730888a662
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/remove-multiline.js
@@ -0,0 +1,45 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ multiline (`m`) modifier can be removed via `(?-m:)`.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+var re1 = /^(?-m:es$)/m;
+assert(!re1.test("\nes\ns"), "$ should not match newline in modified group");
+assert(re1.test("\nes"), "$ should match end of input in modified group");
+
+var re2 = new RegExp("^(?-m:es$)", "m");
+assert(!re2.test("\nes\ns"), "$ should not match newline in modified group");
+assert(re2.test("\nes"), "$ should match end of input in modified group");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/shell.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/shell.js
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/shell.js
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/browser.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/browser.js
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/browser.js
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/shell.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/shell.js
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/shell.js
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-and-remove-modifiers-can-have-empty-remove-modifiers.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-and-remove-modifiers-can-have-empty-remove-modifiers.js
new file mode 100644
index 0000000000..9d5fd6c879
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-and-remove-modifiers-can-have-empty-remove-modifiers.js
@@ -0,0 +1,68 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Modifiers syntax `(?ims-:)` is legal.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+/(?i-:)/;
+/(?is-:)/;
+/(?im-:)/;
+/(?s-:)/;
+/(?si-:)/;
+/(?sm-:)/;
+/(?m-:)/;
+/(?mi-:)/;
+/(?ms-:)/;
+/(?ims-:)/;
+/(?ism-:)/;
+/(?sim-:)/;
+/(?smi-:)/;
+/(?mis-:)/;
+/(?msi-:)/;
+new RegExp("(?i-:)");
+new RegExp("(?is-:)");
+new RegExp("(?im-:)");
+new RegExp("(?s-:)");
+new RegExp("(?si-:)");
+new RegExp("(?sm-:)");
+new RegExp("(?m-:)");
+new RegExp("(?mi-:)");
+new RegExp("(?ms-:)");
+new RegExp("(?ims-:)");
+new RegExp("(?ism-:)");
+new RegExp("(?sim-:)");
+new RegExp("(?smi-:)");
+new RegExp("(?mis-:)");
+new RegExp("(?msi-:)");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-and-remove-modifiers.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-and-remove-modifiers.js
new file mode 100644
index 0000000000..728d47d3a0
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-and-remove-modifiers.js
@@ -0,0 +1,74 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Modifiers syntax `(?im-s:)` (and similar) is legal, as long as they do not overlap.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+/(?i-s:)/;
+/(?i-sm:)/;
+/(?i-m:)/;
+/(?i-ms:)/;
+/(?s-i:)/;
+/(?s-im:)/;
+/(?s-m:)/;
+/(?s-mi:)/;
+/(?m-i:)/;
+/(?m-is:)/;
+/(?m-s:)/;
+/(?m-si:)/;
+/(?is-m:)/;
+/(?im-s:)/;
+/(?si-m:)/;
+/(?sm-i:)/;
+/(?mi-s:)/;
+/(?ms-i:)/;
+new RegExp("(?i-s:)");
+new RegExp("(?i-sm:)");
+new RegExp("(?i-m:)");
+new RegExp("(?i-ms:)");
+new RegExp("(?s-i:)");
+new RegExp("(?s-im:)");
+new RegExp("(?s-m:)");
+new RegExp("(?s-mi:)");
+new RegExp("(?m-i:)");
+new RegExp("(?m-is:)");
+new RegExp("(?m-s:)");
+new RegExp("(?m-si:)");
+new RegExp("(?is-m:)");
+new RegExp("(?im-s:)");
+new RegExp("(?si-m:)");
+new RegExp("(?sm-i:)");
+new RegExp("(?mi-s:)");
+new RegExp("(?ms-i:)");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-modifiers-when-nested.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-modifiers-when-nested.js
new file mode 100644
index 0000000000..278633d304
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-modifiers-when-nested.js
@@ -0,0 +1,44 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Modifiers syntax `(?ims:)` is legal, even when modifiers are already set via an outer non-capturing group.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+/(?i:(?i:))/;
+/(?s:(?s:))/;
+/(?m:(?m:))/;
+new RegExp("(?i:(?i:))");
+new RegExp("(?s:(?s:))");
+new RegExp("(?m:(?m:))");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-modifiers-when-not-set-as-flags.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-modifiers-when-not-set-as-flags.js
new file mode 100644
index 0000000000..e288c833c6
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-modifiers-when-not-set-as-flags.js
@@ -0,0 +1,68 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Modifiers syntax `(?ims:)` is legal.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+/(?i:)/;
+/(?is:)/;
+/(?im:)/;
+/(?s:)/;
+/(?si:)/;
+/(?sm:)/;
+/(?m:)/;
+/(?mi:)/;
+/(?ms:)/;
+/(?ims:)/;
+/(?ism:)/;
+/(?sim:)/;
+/(?smi:)/;
+/(?mis:)/;
+/(?msi:)/;
+new RegExp("(?i:)");
+new RegExp("(?is:)");
+new RegExp("(?im:)");
+new RegExp("(?s:)");
+new RegExp("(?si:)");
+new RegExp("(?sm:)");
+new RegExp("(?m:)");
+new RegExp("(?mi:)");
+new RegExp("(?ms:)");
+new RegExp("(?ims:)");
+new RegExp("(?ism:)");
+new RegExp("(?sim:)");
+new RegExp("(?smi:)");
+new RegExp("(?mis:)");
+new RegExp("(?msi:)");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-modifiers-when-set-as-flags.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-modifiers-when-set-as-flags.js
new file mode 100644
index 0000000000..f1d5cedc83
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/add-modifiers-when-set-as-flags.js
@@ -0,0 +1,46 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Modifiers syntax `(?ims:)` is legal, even when modifiers are already set via flags.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by RegularExpressionFlags.
+ 2. Let removeModifiers be the empty String.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), removeModifiers).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+/(?i:)/i;
+/(?s:)/s;
+/(?m:)/m;
+/(?ims:)/ims;
+new RegExp("(?i:)", "i");
+new RegExp("(?s:)", "s");
+new RegExp("(?m:)", "m");
+new RegExp("(?ims:)", "ims");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/browser.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/browser.js
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/browser.js
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/remove-modifiers-when-nested.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/remove-modifiers-when-nested.js
new file mode 100644
index 0000000000..90d5e5e606
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/remove-modifiers-when-nested.js
@@ -0,0 +1,44 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Modifiers syntax `(?-ims:)` is legal, even when modifiers are already cleared via an outer non-capturing group.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+/(?-i:(?-i:))/;
+/(?-s:(?-s:))/;
+/(?-m:(?-m:))/;
+new RegExp("(?-i:(?-i:))");
+new RegExp("(?-s:(?-s:))");
+new RegExp("(?-m:(?-m:))");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/remove-modifiers-when-not-set-as-flags.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/remove-modifiers-when-not-set-as-flags.js
new file mode 100644
index 0000000000..397e94ce6b
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/remove-modifiers-when-not-set-as-flags.js
@@ -0,0 +1,68 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Modifiers syntax `(?-ims:)` is legal, even when not set as flags.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+/(?-i:)/;
+/(?-is:)/;
+/(?-im:)/;
+/(?-s:)/;
+/(?-si:)/;
+/(?-sm:)/;
+/(?-m:)/;
+/(?-mi:)/;
+/(?-ms:)/;
+/(?-ims:)/;
+/(?-ism:)/;
+/(?-smi:)/;
+/(?-sim:)/;
+/(?-mis:)/;
+/(?-msi:)/;
+new RegExp("(?-i:)");
+new RegExp("(?-is:)");
+new RegExp("(?-im:)");
+new RegExp("(?-s:)");
+new RegExp("(?-si:)");
+new RegExp("(?-sm:)");
+new RegExp("(?-m:)");
+new RegExp("(?-mi:)");
+new RegExp("(?-ms:)");
+new RegExp("(?-ims:)");
+new RegExp("(?-ism:)");
+new RegExp("(?-smi:)");
+new RegExp("(?-sim:)");
+new RegExp("(?-mis:)");
+new RegExp("(?-msi:)");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/remove-modifiers-when-set-as-flags.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/remove-modifiers-when-set-as-flags.js
new file mode 100644
index 0000000000..1b96c747a8
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/remove-modifiers-when-set-as-flags.js
@@ -0,0 +1,68 @@
+// |reftest| skip -- regexp-modifiers is not supported
+// Copyright 2023 Ron Buckton. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Ron Buckton
+description: >
+ Modifiers syntax `(?-ims:)` is legal.
+info: |
+ Runtime Semantics: CompileAtom
+ The syntax-directed operation CompileAtom takes arguments direction (forward or backward) and modifiers (a Modifiers Record) and returns a Matcher.
+
+ Atom :: `(` `?` RegularExpressionFlags `-` RegularExpressionFlags `:` Disjunction `)`
+ 1. Let addModifiers be the source text matched by the first RegularExpressionFlags.
+ 2. Let removeModifiers be the source text matched by the second RegularExpressionFlags.
+ 3. Let newModifiers be UpdateModifiers(modifiers, CodePointsToString(addModifiers), CodePointsToString(removeModifiers)).
+ 4. Return CompileSubpattern of Disjunction with arguments direction and newModifiers.
+
+ UpdateModifiers ( modifiers, add, remove )
+ The abstract operation UpdateModifiers takes arguments modifiers (a Modifiers Record), add (a String), and remove (a String) and returns a Modifiers. It performs the following steps when called:
+
+ 1. Let dotAll be modifiers.[[DotAll]].
+ 2. Let ignoreCase be modifiers.[[IgnoreCase]].
+ 3. Let multiline be modifiers.[[Multiline]].
+ 4. If add contains "s", set dotAll to true.
+ 5. If add contains "i", set ignoreCase to true.
+ 6. If add contains "m", set multiline to true.
+ 7. If remove contains "s", set dotAll to false.
+ 8. If remove contains "i", set ignoreCase to false.
+ 9. If remove contains "m", set multiline to false.
+ 10. Return the Modifiers Record { [[DotAll]]: dotAll, [[IgnoreCase]]: ignoreCase, [[Multiline]]: multiline }.
+
+esid: sec-compileatom
+features: [regexp-modifiers]
+---*/
+
+/(?-i:)/i;
+/(?-is:)/is;
+/(?-im:)/im;
+/(?-s:)/s;
+/(?-si:)/si;
+/(?-sm:)/sm;
+/(?-m:)/m;
+/(?-mi:)/mi;
+/(?-ms:)/ms;
+/(?-ims:)/ims;
+/(?-ism:)/ism;
+/(?-sim:)/sim;
+/(?-smi:)/smi;
+/(?-mis:)/mis;
+/(?-msi:)/msi;
+new RegExp("(?-i:)", "i");
+new RegExp("(?-is:)", "is");
+new RegExp("(?-im:)", "im");
+new RegExp("(?-s:)", "s");
+new RegExp("(?-si:)", "si");
+new RegExp("(?-sm:)", "sm");
+new RegExp("(?-m:)", "m");
+new RegExp("(?-mi:)", "mi");
+new RegExp("(?-ms:)", "ms");
+new RegExp("(?-ims:)", "ims");
+new RegExp("(?-ism:)", "ism");
+new RegExp("(?-sim:)", "sim");
+new RegExp("(?-smi:)", "smi");
+new RegExp("(?-mis:)", "mis");
+new RegExp("(?-msi:)", "msi");
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/shell.js b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/shell.js
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/js/src/tests/test262/built-ins/RegExp/regexp-modifiers/syntax/valid/shell.js