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[INFER] Constant fold 'x ==/!= null' comparisons with a known result, bug 654705.

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This commit is contained in:
Brian Hackett 2011-05-22 20:53:33 -07:00
parent 30f0c2d28b
commit bdd6f8267a
3 changed files with 34 additions and 16 deletions
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37
js/src/methodjit/Compiler.cpp
View File

@ -1724,21 +1724,8 @@ mjit::Compiler::generateMethod()
} else {
if (fused == JSOP_IFEQ)
result = !result;
if (result) {
if (!frame.syncForBranch(target, Uses(0)))
return Compile_Error;
Jump j = masm.jump();
if (!jumpAndTrace(j, target))
return Compile_Error;
} else {
/*
* Branch is never taken, but clean up any loop
* if this is a backedge.
*/
if (target < PC && !finishLoop(target))
return Compile_Error;
}
if (!constantFoldBranch(target, result))
return Compile_Error;
}
} else {
if (!emitStubCmpOp(stub, target, fused))
@ -4035,6 +4022,26 @@ mjit::Compiler::compareTwoValues(JSContext *cx, JSOp op, const Value &lhs, const
return false;
}
bool
mjit::Compiler::constantFoldBranch(jsbytecode *target, bool taken)
{
if (taken) {
if (!frame.syncForBranch(target, Uses(0)))
return false;
Jump j = masm.jump();
if (!jumpAndTrace(j, target))
return false;
} else {
/*
* Branch is never taken, but clean up any loop
* if this is a backedge.
*/
if (target < PC && !finishLoop(target))
return false;
}
return true;
}
bool
mjit::Compiler::emitStubCmpOp(BoolStub stub, jsbytecode *target, JSOp fused)
{

1
js/src/methodjit/Compiler.h
View File

@ -572,6 +572,7 @@ class Compiler : public BaseCompiler
bool canUseApplyTricks();
/* Emitting helpers. */
bool constantFoldBranch(jsbytecode *target, bool taken);
bool emitStubCmpOp(BoolStub stub, jsbytecode *target, JSOp fused);
bool iter(uintN flags);
void iterNext();

12
js/src/methodjit/FastOps.cpp
View File

@ -414,8 +414,18 @@ mjit::Compiler::jsop_equality(JSOp op, BoolStub stub, jsbytecode *target, JSOp f
/* What's the other mask? */
FrameEntry *test = lhsTest ? rhs : lhs;
if (test->isTypeKnown())
if (test->isType(JSVAL_TYPE_NULL) || test->isType(JSVAL_TYPE_UNDEFINED)) {
return emitStubCmpOp(stub, target, fused);
} else if (test->isTypeKnown()) {
/* The test will not succeed, constant fold the compare. */
bool result = GetCompareCondition(op, fused) == Assembler::NotEqual;
frame.pop();
frame.pop();
if (target)
return constantFoldBranch(target, result);
frame.push(BooleanValue(result));
return true;
}
/* The other side must be null or undefined. */
RegisterID reg = frame.ownRegForType(test);