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authorwolfbeast <mcwerewolf@wolfbeast.com>2019-05-28 18:03:08 +0200
committerwolfbeast <mcwerewolf@wolfbeast.com>2019-05-28 18:22:48 +0200
commit528072c39363668b528b2bcfaaa6891b92caa8fa (patch)
tree6f26f37d0ee1c3fa13bac7d423addba6c9d9c376
parent4ad94cfde9ffbb8b32b461ed288327e17ea936c9 (diff)
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Improve efficiency of (C++) heap allocations related to
BytecodeEmitter::code. While there, also add some sanity checks and clean up code.
-rw-r--r--js/src/frontend/BytecodeEmitter.cpp28
-rw-r--r--js/src/frontend/BytecodeEmitter.h10
2 files changed, 24 insertions, 14 deletions
diff --git a/js/src/frontend/BytecodeEmitter.cpp b/js/src/frontend/BytecodeEmitter.cpp
index b3dd6d777..c524184d6 100644
--- a/js/src/frontend/BytecodeEmitter.cpp
+++ b/js/src/frontend/BytecodeEmitter.cpp
@@ -2260,12 +2260,14 @@ BytecodeEmitter::locationOfNameBoundInFunctionScope(JSAtom* name, EmitterScope*
bool
BytecodeEmitter::emitCheck(ptrdiff_t delta, ptrdiff_t* offset)
{
- *offset = code().length();
+ size_t oldLength = code().length();
+ *offset = ptrdiff_t(oldLength);
- // Start it off moderately large to avoid repeated resizings early on.
- // ~98% of cases fit within 1024 bytes.
- if (code().capacity() == 0 && !code().reserve(1024))
- return false;
+ size_t newLength = oldLength + size_t(delta);
+ if (MOZ_UNLIKELY(newLength > MaxBytecodeLength)) {
+ ReportAllocationOverflow(cx);
+ return false;
+ }
if (!code().growBy(delta)) {
ReportOutOfMemory(cx);
@@ -10697,17 +10699,19 @@ BytecodeEmitter::emitTreeInBranch(ParseNode* pn)
static bool
AllocSrcNote(ExclusiveContext* cx, SrcNotesVector& notes, unsigned* index)
{
- // Start it off moderately large to avoid repeated resizings early on.
- // ~99% of cases fit within 256 bytes.
- if (notes.capacity() == 0 && !notes.reserve(256))
- return false;
+ size_t oldLength = notes.length();
+ if (MOZ_UNLIKELY(oldLength + 1 > MaxSrcNotesLength)) {
+ ReportAllocationOverflow(cx);
+ return false;
+ }
+
if (!notes.growBy(1)) {
ReportOutOfMemory(cx);
return false;
}
- *index = notes.length() - 1;
+ *index = oldLength;
return true;
}
@@ -10833,6 +10837,10 @@ BytecodeEmitter::setSrcNoteOffset(unsigned index, unsigned which, ptrdiff_t offs
/* Maybe this offset was already set to a four-byte value. */
if (!(*sn & SN_4BYTE_OFFSET_FLAG)) {
/* Insert three dummy bytes that will be overwritten shortly. */
+ if (MOZ_UNLIKELY(notes.length() + 3 > MaxSrcNotesLength)) {
+ ReportAllocationOverflow(cx);
+ return false;
+ }
jssrcnote dummy = 0;
if (!(sn = notes.insert(sn, dummy)) ||
!(sn = notes.insert(sn, dummy)) ||
diff --git a/js/src/frontend/BytecodeEmitter.h b/js/src/frontend/BytecodeEmitter.h
index 32668a34c..814fa11d4 100644
--- a/js/src/frontend/BytecodeEmitter.h
+++ b/js/src/frontend/BytecodeEmitter.h
@@ -109,10 +109,12 @@ struct CGYieldOffsetList {
void finish(YieldOffsetArray& array, uint32_t prologueLength);
};
-// Use zero inline elements because these go on the stack and affect how many
-// nested functions are possible.
-typedef Vector<jsbytecode, 0> BytecodeVector;
-typedef Vector<jssrcnote, 0> SrcNotesVector;
+static size_t MaxBytecodeLength = INT32_MAX;
+static size_t MaxSrcNotesLength = INT32_MAX;
+
+// Have a few inline elements to avoid heap allocation for tiny sequences.
+typedef Vector<jsbytecode, 256> BytecodeVector;
+typedef Vector<jssrcnote, 64> SrcNotesVector;
// 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