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Improve efficiency of (C++) heap allocations related to

Browse source 
BytecodeEmitter::code.

While there, also add some sanity checks and clean up code.
This commit is contained in:
wolfbeast 2019-05-28 18:03:08 +02:00 • committed by Roy Tam
commit cdfd0e29e7
2 changed files with 24 additions and 14 deletions
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28
js/src/frontend/BytecodeEmitter.cpp
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@ -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)) ||