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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-19 00:47:55 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-19 00:47:55 +0000
commit26a029d407be480d791972afb5975cf62c9360a6 (patch)
treef435a8308119effd964b339f76abb83a57c29483 /js/src/frontend/JumpList.h
parentInitial commit. (diff)
downloadfirefox-26a029d407be480d791972afb5975cf62c9360a6.tar.xz
firefox-26a029d407be480d791972afb5975cf62c9360a6.zip
Adding upstream version 124.0.1.upstream/124.0.1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'js/src/frontend/JumpList.h')
-rw-r--r--js/src/frontend/JumpList.h84
1 files changed, 84 insertions, 0 deletions
diff --git a/js/src/frontend/JumpList.h b/js/src/frontend/JumpList.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef frontend_JumpList_h
+#define frontend_JumpList_h
+
+#include <stddef.h> // ptrdiff_t
+
+#include "frontend/BytecodeOffset.h" // BytecodeOffset
+#include "js/TypeDecls.h" // jsbytecode
+
+namespace js {
+namespace frontend {
+
+// Linked list of jump instructions that need to be patched. The linked list is
+// stored in the bytes of the incomplete bytecode that will be patched, so no
+// extra memory is needed, and patching the instructions destroys the list.
+//
+// Example:
+//
+// JumpList brList;
+// if (!emitJump(JSOp::JumpIfFalse, &brList)) {
+// return false;
+// }
+// ...
+// JumpTarget label;
+// if (!emitJumpTarget(&label)) {
+// return false;
+// }
+// ...
+// if (!emitJump(JSOp::Goto, &brList)) {
+// return false;
+// }
+// ...
+// patchJumpsToTarget(brList, label);
+//
+// +-> (the delta is END_OF_LIST_DELTA (=0) for the last
+// | item)
+// |
+// |
+// JumpIfFalse .. <+ + +-+ JumpIfFalse ..
+// .. | | ..
+// label: | +-> label:
+// JumpTarget | | JumpTarget
+// .. | | ..
+// Goto .. <+ +----+ +-+ Goto .. <+
+// | |
+// | |
+// + +
+// brList brList
+//
+// | ^
+// +------- patchJumpsToTarget -------+
+//
+
+// Offset of a jump target instruction, used for patching jump instructions.
+struct JumpTarget {
+ BytecodeOffset offset = BytecodeOffset::invalidOffset();
+};
+
+struct JumpList {
+ // Delta value for pre-patchJumpsToTarget that marks the end of the link.
+ static const ptrdiff_t END_OF_LIST_DELTA = 0;
+
+ // -1 is used to mark the end of jump lists.
+ JumpList() : offset(BytecodeOffset::invalidOffset()) {}
+
+ BytecodeOffset offset;
+
+ // Add a jump instruction to the list.
+ void push(jsbytecode* code, BytecodeOffset jumpOffset);
+
+ // Patch all jump instructions in this list to jump to `target`. This
+ // clobbers the list.
+ void patchAll(jsbytecode* code, JumpTarget target);
+};
+
+} /* namespace frontend */
+} /* namespace js */
+
+#endif /* frontend_JumpList_h */