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Bug 1552154 part 4 - Stop using pc-to-native map for BaselineScript::approximatePcForNativeAddress. r=tcampbell

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Differential Revision: https://phabricator.services.mozilla.com/D40947

--HG--
extra : moz-landing-system : lando
This commit is contained in:
Jan de Mooij 2019-08-10 10:21:00 +00:00
parent 99451ccd92
commit e6fbf15029
2 changed files with 15 additions and 48 deletions
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59
js/src/jit/BaselineJIT.cpp
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@ -779,56 +779,23 @@ jsbytecode* BaselineScript::approximatePcForNativeAddress(
uint32_t nativeOffset = nativeAddress - method_->raw();
// The native code address can occur before the start of ops. Associate
// those with start of bytecode.
if (nativeOffset < pcMappingIndexEntry(0).nativeOffset) {
return script->code();
}
// Use the RetAddrEntry list (sorted on pc and return address) to look for the
// first pc that has a return address >= nativeOffset. This isn't perfect but
// it's a reasonable approximation for the profiler because most non-trivial
// bytecode ops have a RetAddrEntry.
// Find corresponding PCMappingIndexEntry for native offset. They are in
// ascedending order with the start of one entry being the end of the
// previous entry. Find first entry where nativeOffset < endOffset.
uint32_t i = 0;
for (; (i + 1) < numPCMappingIndexEntries(); i++) {
uint32_t endOffset = pcMappingIndexEntry(i + 1).nativeOffset;
if (nativeOffset < endOffset) {
break;
for (const RetAddrEntry& entry : retAddrEntries()) {
uint32_t retOffset = entry.returnOffset().offset();
if (retOffset >= nativeOffset) {
return script->offsetToPC(entry.pcOffset());
}
}
PCMappingIndexEntry& entry = pcMappingIndexEntry(i);
MOZ_ASSERT(nativeOffset >= entry.nativeOffset);
CompactBufferReader reader(pcMappingReader(i));
MOZ_ASSERT(reader.more());
jsbytecode* curPC = script->offsetToPC(entry.pcOffset);
uint32_t curNativeOffset = entry.nativeOffset;
MOZ_ASSERT(script->containsPC(curPC));
jsbytecode* lastPC = curPC;
while (reader.more()) {
// If the high bit is set, the native offset relative to the
// previous pc != 0 and comes next.
uint8_t b = reader.readByte();
if (b & 0x80) {
curNativeOffset += reader.readUnsigned();
}
// Return the last PC that matched nativeOffset. Some bytecode
// generate no native code (e.g., constant-pushing bytecode like
// JSOP_INT8), and so their entries share the same nativeOffset as the
// next op that does generate code.
if (curNativeOffset > nativeOffset) {
return lastPC;
}
lastPC = curPC;
curPC += GetBytecodeLength(curPC);
}
// Associate all addresses at end of PCMappingIndexEntry with lastPC.
return lastPC;
// Return the last entry's pc. Every BaselineScript has at least one
// RetAddrEntry for the prologue stack overflow check.
MOZ_ASSERT(retAddrEntries().size() > 0);
const RetAddrEntry& lastEntry = retAddrEntries()[retAddrEntries().size() - 1];
return script->offsetToPC(lastEntry.pcOffset());
}
void BaselineScript::toggleDebugTraps(JSScript* script, jsbytecode* pc) {

4
js/src/jit/BaselineJIT.h
View File

@ -421,8 +421,8 @@ struct BaselineScript final {
}
// Return the bytecode offset for a given native code address. Be careful
// when using this method: we don't emit code for some bytecode ops, so
// the result may not be accurate.
// when using this method: it's an approximation and not guaranteed to be the
// correct pc.
jsbytecode* approximatePcForNativeAddress(JSScript* script,
uint8_t* nativeAddress);