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Bug 1354554 - Remove iterator result object from the stack and place IteratorNext at the top of the loop to avoid having unnecessary values at the backedge. r=shu

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This commit is contained in:
Tooru Fujisawa 2017-04-12 00:43:42 +09:00
parent 07cf9baccd
commit df77d281bb
3 changed files with 110 additions and 78 deletions
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179
js/src/frontend/BytecodeEmitter.cpp
View File

@ -244,9 +244,9 @@ class LoopControl : public BreakableControl
loopDepth_ = enclosingLoop ? enclosingLoop->loopDepth_ + 1 : 1;
int loopSlots;
if (loopKind == StatementKind::Spread || loopKind == StatementKind::ForOfLoop)
if (loopKind == StatementKind::Spread)
loopSlots = 3;
else if (loopKind == StatementKind::ForInLoop)
else if (loopKind == StatementKind::ForInLoop || loopKind == StatementKind::ForOfLoop)
loopSlots = 2;
else
loopSlots = 0;
@ -269,6 +269,20 @@ class LoopControl : public BreakableControl
return canIonOsr_;
}
MOZ_MUST_USE bool emitSpecialBreakForDone(BytecodeEmitter* bce) {
// This doesn't pop stack values, nor handle any other controls.
// Should be called on the toplevel of the loop.
MOZ_ASSERT(bce->stackDepth == stackDepth_);
MOZ_ASSERT(bce->innermostNestableControl == this);
if (!bce->newSrcNote(SRC_BREAK))
return false;
if (!bce->emitJump(JSOP_GOTO, &breaks))
return false;
return true;
}
MOZ_MUST_USE bool patchBreaksAndContinues(BytecodeEmitter* bce) {
MOZ_ASSERT(continueTarget.offset != -1);
if (!patchBreaks(bce))
@ -2080,11 +2094,11 @@ class ForOfLoopControl : public LoopControl
}
bool emitPrepareForNonLocalJump(BytecodeEmitter* bce, bool isTarget) {
// Pop unnecessary values from the stack. Effectively this means
// Pop unnecessary value from the stack. Effectively this means
// leaving try-catch block. However, the performing IteratorClose can
// reach the depth for try-catch, and effectively re-enter the
// try-catch block.
if (!bce->emitPopN(2)) // ITER
if (!bce->emit1(JSOP_POP)) // ITER
return false;
// Clear ITER slot on the stack to tell catch block to avoid performing
@ -2100,11 +2114,9 @@ class ForOfLoopControl : public LoopControl
if (isTarget) {
// At the level of the target block, there's bytecode after the
// loop that will pop the iterator and the value, so push
// undefineds to balance the stack.
// an undefined to balance the stack.
if (!bce->emit1(JSOP_UNDEFINED)) // UNDEF UNDEF
return false;
if (!bce->emit1(JSOP_UNDEFINED)) // UNDEF UNDEF UNDEF
return false;
} else {
if (!bce->emit1(JSOP_POP)) //
return false;
@ -2780,7 +2792,7 @@ NonLocalExitControl::prepareForNonLocalJump(BytecodeEmitter::NestableControl* ta
if (!loopinfo.emitPrepareForNonLocalJump(bce_, /* isTarget = */ false)) // ...
return false;
} else {
npops += 3;
npops += 2;
}
break;
@ -2805,7 +2817,7 @@ NonLocalExitControl::prepareForNonLocalJump(BytecodeEmitter::NestableControl* ta
if (target && emitIteratorCloseAtTarget && target->is<ForOfLoopControl>()) {
ForOfLoopControl& loopinfo = target->as<ForOfLoopControl>();
if (!loopinfo.emitPrepareForNonLocalJump(bce_, /* isTarget = */ true)) // ... UNDEF UNDEF UNDEF
if (!loopinfo.emitPrepareForNonLocalJump(bce_, /* isTarget = */ true)) // ... UNDEF UNDEF
return false;
}
@ -7026,11 +7038,9 @@ BytecodeEmitter::emitForOf(ParseNode* forOfLoop, EmitterScope* headLexicalEmitte
int32_t iterDepth = stackDepth;
// For-of loops have both the iterator, the result, and the result.value
// on the stack. Push undefineds to balance the stack.
if (!emit1(JSOP_UNDEFINED)) // ITER RESULT
return false;
if (!emit1(JSOP_UNDEFINED)) // ITER RESULT UNDEF
// For-of loops have both the iterator and the result.value on the stack.
// Push an undefined to balance the stack.
if (!emit1(JSOP_UNDEFINED)) // ITER UNDEF
return false;
ForOfLoopControl loopInfo(this, iterDepth, allowSelfHostedIter, iterKind);
@ -7041,11 +7051,11 @@ BytecodeEmitter::emitForOf(ParseNode* forOfLoop, EmitterScope* headLexicalEmitte
return false;
JumpList initialJump;
if (!emitJump(JSOP_GOTO, &initialJump)) // ITER RESULT UNDEF
if (!emitJump(JSOP_GOTO, &initialJump)) // ITER UNDEF
return false;
JumpTarget top{ -1 };
if (!emitLoopHead(nullptr, &top)) // ITER RESULT UNDEF
if (!emitLoopHead(nullptr, &top)) // ITER UNDEF
return false;
// If the loop had an escaping lexical declaration, replace the current
@ -7062,7 +7072,7 @@ BytecodeEmitter::emitForOf(ParseNode* forOfLoop, EmitterScope* headLexicalEmitte
MOZ_ASSERT(headLexicalEmitterScope->scope(this)->kind() == ScopeKind::Lexical);
if (headLexicalEmitterScope->hasEnvironment()) {
if (!emit1(JSOP_RECREATELEXICALENV)) // ITER RESULT UNDEF
if (!emit1(JSOP_RECREATELEXICALENV)) // ITER UNDEF
return false;
}
@ -7078,21 +7088,49 @@ BytecodeEmitter::emitForOf(ParseNode* forOfLoop, EmitterScope* headLexicalEmitte
auto loopDepth = this->stackDepth;
#endif
if (!emit1(JSOP_POP)) // ITER
return false;
if (!emit1(JSOP_DUP)) // ITER ITER
return false;
if (!emitIteratorNext(forOfHead, iterKind, allowSelfHostedIter))
return false; // ITER RESULT
if (!emit1(JSOP_DUP)) // ITER RESULT RESULT
return false;
if (!emitAtomOp(cx->names().done, JSOP_GETPROP)) // ITER RESULT DONE
return false;
IfThenElseEmitter ifDone(this);
if (!ifDone.emitIf()) // ITER RESULT
return false;
// Remove RESULT from the stack to release it.
if (!emit1(JSOP_POP)) // ITER
return false;
if (!emit1(JSOP_UNDEFINED)) // ITER UNDEF
return false;
// If the iteration is done, leave loop here, instead of the branch at
// the end of the loop.
if (!loopInfo.emitSpecialBreakForDone(this)) // ITER UNDEF
return false;
if (!ifDone.emitEnd()) // ITER RESULT
return false;
// Emit code to assign result.value to the iteration variable.
//
// Note that ES 13.7.5.13, step 5.c says getting result.value does not
// call IteratorClose, so start JSTRY_ITERCLOSE after the GETPROP.
if (!emit1(JSOP_POP)) // ITER RESULT
return false;
if (!emit1(JSOP_DUP)) // ITER RESULT RESULT
return false;
if (!emitAtomOp(cx->names().value, JSOP_GETPROP)) // ITER RESULT VALUE
if (!emitAtomOp(cx->names().value, JSOP_GETPROP)) // ITER VALUE
return false;
if (!loopInfo.emitBeginCodeNeedingIteratorClose(this))
return false;
if (!emitInitializeForInOrOfTarget(forOfHead)) // ITER RESULT VALUE
if (!emitInitializeForInOrOfTarget(forOfHead)) // ITER VALUE
return false;
MOZ_ASSERT(stackDepth == loopDepth,
@ -7100,14 +7138,14 @@ BytecodeEmitter::emitForOf(ParseNode* forOfLoop, EmitterScope* headLexicalEmitte
"operation");
// Remove VALUE from the stack to release it.
if (!emit1(JSOP_POP)) // ITER RESULT
if (!emit1(JSOP_POP)) // ITER
return false;
if (!emit1(JSOP_UNDEFINED)) // ITER RESULT UNDEF
if (!emit1(JSOP_UNDEFINED)) // ITER UNDEF
return false;
// Perform the loop body.
ParseNode* forBody = forOfLoop->pn_right;
if (!emitTree(forBody)) // ITER RESULT UNDEF
if (!emitTree(forBody)) // ITER UNDEF
return false;
MOZ_ASSERT(stackDepth == loopDepth,
@ -7119,29 +7157,13 @@ BytecodeEmitter::emitForOf(ParseNode* forOfLoop, EmitterScope* headLexicalEmitte
// Set offset for continues.
loopInfo.continueTarget = { offset() };
if (!emitLoopEntry(forHeadExpr, initialJump)) // ITER RESULT UNDEF
if (!emitLoopEntry(forHeadExpr, initialJump)) // ITER UNDEF
return false;
if (!emit1(JSOP_SWAP)) // ITER UNDEF RESULT
if (!emit1(JSOP_FALSE)) // ITER UNDEF FALSE
return false;
if (!emit1(JSOP_POP)) // ITER UNDEF
return false;
if (!emitDupAt(1)) // ITER UNDEF ITER
return false;
if (!emitIteratorNext(forOfHead, iterKind, allowSelfHostedIter)) // ITER UNDEF RESULT
return false;
if (!emit1(JSOP_SWAP)) // ITER RESULT UNDEF
return false;
if (!emitDupAt(1)) // ITER RESULT UNDEF RESULT
return false;
if (!emitAtomOp(cx->names().done, JSOP_GETPROP)) // ITER RESULT UNDEF DONE
return false;
if (!emitBackwardJump(JSOP_IFEQ, top, &beq, &breakTarget))
return false; // ITER RESULT UNDEF
return false; // ITER UNDEF
MOZ_ASSERT(this->stackDepth == loopDepth);
}
@ -7156,7 +7178,7 @@ BytecodeEmitter::emitForOf(ParseNode* forOfLoop, EmitterScope* headLexicalEmitte
if (!tryNoteList.append(JSTRY_FOR_OF, stackDepth, top.offset, breakTarget.offset))
return false;
return emitPopN(3); //
return emitPopN(2); //
}
bool
@ -7566,9 +7588,7 @@ BytecodeEmitter::emitComprehensionForOf(ParseNode* pn)
return false;
// Push a dummy result so that we properly enter iteration midstream.
if (!emit1(JSOP_UNDEFINED)) // ITER RESULT
return false;
if (!emit1(JSOP_UNDEFINED)) // ITER RESULT VALUE
if (!emit1(JSOP_UNDEFINED)) // ITER VALUE
return false;
// Enter the block before the loop body, after evaluating the obj.
@ -7606,31 +7626,56 @@ BytecodeEmitter::emitComprehensionForOf(ParseNode* pn)
int loopDepth = this->stackDepth;
#endif
// Emit code to assign result.value to the iteration variable.
if (!emit1(JSOP_POP)) // ITER RESULT
if (!emit1(JSOP_POP)) // ITER
return false;
if (!emit1(JSOP_DUP)) // ITER ITER
return false;
if (!emitIteratorNext(forHead)) // ITER RESULT
return false;
if (!emit1(JSOP_DUP)) // ITER RESULT RESULT
return false;
if (!emitAtomOp(cx->names().value, JSOP_GETPROP)) // ITER RESULT VALUE
if (!emitAtomOp(cx->names().done, JSOP_GETPROP)) // ITER RESULT DONE
return false;
IfThenElseEmitter ifDone(this);
if (!ifDone.emitIf()) // ITER RESULT
return false;
// Remove RESULT from the stack to release it.
if (!emit1(JSOP_POP)) // ITER
return false;
if (!emit1(JSOP_UNDEFINED)) // ITER UNDEF
return false;
// If the iteration is done, leave loop here, instead of the branch at
// the end of the loop.
if (!loopInfo.emitSpecialBreakForDone(this)) // ITER UNDEF
return false;
if (!ifDone.emitEnd()) // ITER RESULT
return false;
// Emit code to assign result.value to the iteration variable.
if (!emitAtomOp(cx->names().value, JSOP_GETPROP)) // ITER VALUE
return false;
// Notice: Comprehension for-of doesn't perform IteratorClose, since it's
// not in the spec.
if (!emitAssignment(loopVariableName, JSOP_NOP, nullptr)) // ITER RESULT VALUE
if (!emitAssignment(loopVariableName, JSOP_NOP, nullptr)) // ITER VALUE
return false;
// Remove VALUE from the stack to release it.
if (!emit1(JSOP_POP)) // ITER RESULT
if (!emit1(JSOP_POP)) // ITER
return false;
if (!emit1(JSOP_UNDEFINED)) // ITER RESULT UNDEF
if (!emit1(JSOP_UNDEFINED)) // ITER UNDEF
return false;
// The stack should be balanced around the assignment opcode sequence.
MOZ_ASSERT(this->stackDepth == loopDepth);
// Emit code for the loop body.
if (!emitTree(forBody)) // ITER RESULT UNDEF
if (!emitTree(forBody)) // ITER UNDEF
return false;
// The stack should be balanced around the assignment opcode sequence.
@ -7642,25 +7687,13 @@ BytecodeEmitter::emitComprehensionForOf(ParseNode* pn)
if (!emitLoopEntry(forHeadExpr, jmp))
return false;
if (!emit1(JSOP_SWAP)) // ITER UNDEF RESULT
return false;
if (!emit1(JSOP_POP)) // ITER UNDEF
return false;
if (!emitDupAt(1)) // ITER UNDEF ITER
return false;
if (!emitIteratorNext(forHead)) // ITER UNDEF RESULT
return false;
if (!emit1(JSOP_SWAP)) // ITER RESULT UNDEF
return false;
if (!emitDupAt(1)) // ITER RESULT UNDEF RESULT
return false;
if (!emitAtomOp(cx->names().done, JSOP_GETPROP)) // ITER RESULT UNDEF DONE
if (!emit1(JSOP_FALSE)) // ITER VALUE FALSE
return false;
JumpList beq;
JumpTarget breakTarget{ -1 };
if (!emitBackwardJump(JSOP_IFEQ, top, &beq, &breakTarget)) // ITER RESULT UNDEF
return false;
if (!emitBackwardJump(JSOP_IFEQ, top, &beq, &breakTarget))
return false; // ITER VALUE
MOZ_ASSERT(this->stackDepth == loopDepth);
@ -7681,7 +7714,7 @@ BytecodeEmitter::emitComprehensionForOf(ParseNode* pn)
}
// Pop the result and the iter.
return emitPopN(3); //
return emitPopN(2); //
}
bool

7
js/src/jit/BaselineBailouts.cpp
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@ -516,10 +516,9 @@ HasLiveStackValueAtDepth(JSScript* script, jsbytecode* pc, uint32_t stackDepth)
break;
case JSTRY_FOR_OF:
// For-of loops have the iterator, the result object, and the value
// of the result object on stack. The iterator is below the result
// object and the value.
if (stackDepth == tn->stackDepth - 2)
// For-of loops have the iterator and the result.value on stack.
// The iterator is below the result.value.
if (stackDepth == tn->stackDepth - 1)
return true;
break;

2
js/src/jit/IonControlFlow.cpp
View File

@ -937,7 +937,7 @@ ControlFlowGenerator::processWhileOrForInLoop(jssrcnote* sn)
size_t stackPhiCount;
if (SN_TYPE(sn) == SRC_FOR_OF)
stackPhiCount = 3;
stackPhiCount = 2;
else if (SN_TYPE(sn) == SRC_FOR_IN)
stackPhiCount = 1;
else