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diff --git a/js/src/jit-test/tests/gc/deduplicateTenuringStrings.js b/js/src/jit-test/tests/gc/deduplicateTenuringStrings.js
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+// |jit-test| skip-if: !('stringRepresentation' in this)
+
+// This is to test the correctness of the string deduplication algorithm during
+// the tenuring phase. Same strings below refer to the same character encoding
+// (either latin1 or twobyte) and the same characters.
+
+// Tests:
+// 1. Same strings with same flags and zones should be deduplicated for
+// all linear strings except atoms and external strings.
+// 2. Same strings, but from different zones should not be deduplicated.
+// 3. Same strings, but with different flags should not be deduplicated.
+
+// We require predictable GC timing to make sure the correct
+// strings are tenured together.
+gczeal(0);
+
+var helperCode = `
+function makeInlineStr(isLatin1) {
+  var s = isLatin1 ? "123456789*1" : "一二三";
+  return s + s;
+}
+
+// Generic linear strings are non-atom, non-extensible, non-inline
+// linear strings.
+// Generic linear strings can only have latin1 characters.
+function makeGenericLinearStr() {
+  return notes(() => 1);
+}
+
+function makeRopeStr(isLatin1) {
+  var left = isLatin1 ? "1" : "一";
+  var right = isLatin1 ? "123456789*123456789*123456" :
+    					   "一二三四五六七八九*一二三四五六七八";
+  return left + right;
+}
+
+function makeExtensibleStr(isLatin1) {
+  var r = makeRopeStr(isLatin1);
+  ensureLinearString(r);
+  return r;
+}
+
+function makeExtensibleStrFrom(str) {
+  var left = str.substr(0, str.length/2);
+  var right = str.substr(str.length/2, str.length);
+  var ropeStr = left + right;
+  return ensureLinearString(ropeStr);
+}
+
+function makeDependentStr(isLatin1) {
+  var e = makeExtensibleStr(isLatin1);
+  var r1 = e + "!";
+  var r2 = e + r1;
+  ensureLinearString(r2);
+  return r1;
+}
+
+function makeDependentStrFrom(str) {
+  var e = makeExtensibleStrFrom(str);
+  var r1 = e.substr(0, e.length/2) + e.substr(e.length/2, e.length);
+  var r2 = e + r1;
+  ensureLinearString(r2);
+  return r1;
+}
+
+function makeExternalStr(isLatin1) {
+  return isLatin1 ? newString("12345678", {external: true}) :
+                    newString("一二三", {external: true});
+}
+
+function tenureStringsWithSameChars(str1, str2, isDeduplicatable) {
+  minorgc();
+  assertEq(stringRepresentation(str1) == stringRepresentation(str2),
+	   isDeduplicatable);
+}
+
+function assertDiffStrRepAfterMinorGC(g1, g2) {
+  minorgc();
+  g1.eval(\`strRep = stringRepresentation(str);\`);
+  g2.eval(\`strRep = stringRepresentation(str);\`);
+  assertEq(g1.strRep == g2.strRep, false);
+}
+`;
+
+eval(helperCode);
+
+// test1:
+// Same strings with same flags and zones should be deduplicated for all linear
+// strings except atoms, external strings.
+function test1(isLatin1) {
+  const isDeduplicatable = true;
+
+  // Deduplicatable:
+  // --> Inline Strings
+  var str1 = makeInlineStr(isLatin1);
+  var str2 = makeInlineStr(isLatin1);
+  tenureStringsWithSameChars(str1, str2, isDeduplicatable);
+
+  // --> Extensible Strings
+  str1 = makeExtensibleStr(isLatin1);
+  str2 = makeExtensibleStr(isLatin1);
+  tenureStringsWithSameChars(str1, str2, isDeduplicatable);
+
+  // --> Dependent Strings
+  str1 = makeDependentStr(isLatin1);
+  str2 = makeDependentStr(isLatin1);
+  tenureStringsWithSameChars(str1, str2, isDeduplicatable);
+
+  // --> Generic Linear Strings
+  if (isLatin1) {
+    var str1 = makeGenericLinearStr();
+    var str2 = makeGenericLinearStr();
+    tenureStringsWithSameChars(str1, str2, isDeduplicatable);
+  }
+
+  // Non-Deduplicatable:
+  // --> Rope Strings
+  str1 = makeRopeStr(isLatin1);
+  str2 = makeRopeStr(isLatin1);
+  tenureStringsWithSameChars(str1, str2, !isDeduplicatable);
+
+  // --> Atom strings are deduplicated already but not through string
+  // deduplication during tenuring.
+
+  // --> External strings are not nursery allocated.
+}
+
+// test2:
+// Same strings, but from different zones should not be deduplicated.
+function test2(isLatin1) {
+  var g1 = newGlobal({ newCompartment: true });
+  var g2 = newGlobal({ newCompartment: true });
+
+  g1.eval(helperCode);
+  g2.eval(helperCode);
+
+  // --> Inline Strings
+  g1.eval(`var str = makeInlineStr(${isLatin1}); `);
+  g2.eval(`var str = makeInlineStr(${isLatin1}); `);
+  assertDiffStrRepAfterMinorGC(g1, g2);
+
+  // --> Extensible Strings
+  g1.eval(`str = makeExtensibleStr(${isLatin1}); `);
+  g2.eval(`str = makeExtensibleStr(${isLatin1}); `);
+  assertDiffStrRepAfterMinorGC(g1, g2);
+
+  // --> Dependent Strings
+  g1.eval(`str = makeDependentStr(${isLatin1}); `);
+  g2.eval(`str = makeDependentStr(${isLatin1}); `);
+  assertDiffStrRepAfterMinorGC(g1, g2);
+
+  // --> Generic Linear Strings
+  if (isLatin1) {
+    g1.eval(`str = makeGenericLinearStr();`);
+    g2.eval(`str = makeGenericLinearStr();`);
+    assertDiffStrRepAfterMinorGC(g1, g2);
+  }
+}
+
+// test3:
+// Same strings, but with different flags should not be deduplicated.
+function test3(isLatin1) {
+  const isDeduplicatable = true;
+
+  // --> Dependent String and Extensible String
+  var dependentStr = makeDependentStr(isLatin1);
+  var extensibleStr = makeExtensibleStrFrom(dependentStr);
+  tenureStringsWithSameChars(dependentStr, extensibleStr, !isDeduplicatable);
+
+  if (isLatin1) {
+    // --> Generic Linear String and Extensible String
+    var genericLinearStr = makeGenericLinearStr();
+    var extensibleStr = makeExtensibleStrFrom(genericLinearStr);
+    tenureStringsWithSameChars(
+      genericLinearStr,
+      extensibleStr,
+      !isDeduplicatable
+    );
+
+    // --> Generic Linear String and Dependent String
+    var dependentStr = makeDependentStrFrom(genericLinearStr);
+    tenureStringsWithSameChars(
+      dependentStr,
+      genericLinearStr,
+      !isDeduplicatable
+    );
+  }
+
+  // --> Inline strings are too short to have the same chars as the extensible
+  // strings, generic linear strings and dependent strings
+}
+
+function runTests() {
+  var charEncoding = { TWOBYTE: 0, LATIN1: 1 };
+
+  test1(charEncoding.TWOBYTE);
+  test2(charEncoding.TWOBYTE);
+  test3(charEncoding.TWOBYTE);
+
+  test1(charEncoding.LATIN1);
+  test2(charEncoding.LATIN1);
+  test3(charEncoding.LATIN1);
+}
+
+runTests();