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Make strict equality checks faster on IA32 by doing

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more work in the CompareStub. I'll port this to ARM
once I'm satisfied with the performance improvements.
Review URL: http://codereview.chromium.org/7014

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@481 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
kasperl@chromium.org 2008-10-10 06:26:35 +00:00
parent 89c762edf4
commit 1c89cef32d
2 changed files with 83 additions and 15 deletions
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77
src/codegen-ia32.cc
View File

@ -1127,9 +1127,8 @@ void CodeGenerator::Comparison(Condition cc, bool strict) {
__ pop(edx);
}
// Check for the smi case.
Label is_smi, done;
CompareStub stub(cc, strict);
__ mov(ecx, Operand(eax));
__ or_(ecx, Operand(edx));
__ test(ecx, Immediate(kSmiTagMask));
@ -1137,8 +1136,13 @@ void CodeGenerator::Comparison(Condition cc, bool strict) {
// When non-smi, call out to the compare stub. "parameters" setup by
// calling code in edx and eax and "result" is returned in the flags.
CompareStub stub(cc, strict);
__ CallStub(&stub);
__ cmp(eax, 0);
if (cc == equal) {
__ test(eax, Operand(eax));
} else {
__ cmp(eax, 0);
}
__ jmp(&done);
// Test smi equality by pointer comparison.
@ -4484,6 +4488,73 @@ void ArgumentsAccessStub::GenerateNewObject(MacroAssembler* masm) {
void CompareStub::Generate(MacroAssembler* masm) {
Label call_builtin, done;
// If we're doing a strict equality comparison, we generate code
// to do fast comparison for objects and oddballs. Numbers and
// strings still go through the usual slow-case code.
if (strict_) {
Label slow;
__ test(eax, Immediate(kSmiTagMask));
__ j(zero, &slow);
// Get the type of the first operand.
__ mov(ecx, FieldOperand(eax, HeapObject::kMapOffset));
__ movzx_b(ecx, FieldOperand(ecx, Map::kInstanceTypeOffset));
// If the first object is an object, we do pointer comparison.
ASSERT(LAST_TYPE == JS_FUNCTION_TYPE);
Label non_object;
__ cmp(ecx, FIRST_JS_OBJECT_TYPE);
__ j(less, &non_object);
__ sub(eax, Operand(edx));
__ ret(0);
// Check for oddballs: true, false, null, undefined.
__ bind(&non_object);
__ cmp(ecx, ODDBALL_TYPE);
__ j(not_equal, &slow);
// If the oddball isn't undefined, we do pointer comparison. For
// the undefined value, we have to be careful and check for
// 'undetectable' objects too.
Label undefined;
__ cmp(Operand(eax), Immediate(Factory::undefined_value()));
__ j(equal, &undefined);
__ sub(eax, Operand(edx));
__ ret(0);
// Undefined case: If the other operand isn't undefined too, we
// have to check if it's 'undetectable'.
Label check_undetectable;
__ bind(&undefined);
__ cmp(Operand(edx), Immediate(Factory::undefined_value()));
__ j(not_equal, &check_undetectable);
__ Set(eax, Immediate(0));
__ ret(0);
// Check for undetectability of the other operand.
Label not_strictly_equal;
__ bind(&check_undetectable);
__ test(edx, Immediate(kSmiTagMask));
__ j(zero, &not_strictly_equal);
__ mov(ecx, FieldOperand(edx, HeapObject::kMapOffset));
__ movzx_b(ecx, FieldOperand(ecx, Map::kBitFieldOffset));
__ and_(ecx, 1 << Map::kIsUndetectable);
__ cmp(ecx, 1 << Map::kIsUndetectable);
__ j(not_equal, &not_strictly_equal);
__ Set(eax, Immediate(0));
__ ret(0);
// No cigar: Objects aren't strictly equal. Register eax contains
// a non-smi value so it can't be 0. Just return.
ASSERT(kHeapTag != 0);
__ bind(&not_strictly_equal);
__ ret(0);
// Fall through to the general case.
__ bind(&slow);
}
// Save the return address (and get it off the stack).
__ pop(ecx);

21
src/runtime.js
View File

@ -91,26 +91,23 @@ function EQUALS(y) {
// ECMA-262, section 11.9.4, page 56.
function STRICT_EQUALS(x) {
if (IS_NUMBER(this)) {
if (!IS_NUMBER(x)) return 1; // not equal
return %NumberEquals(this, x);
}
if (IS_STRING(this)) {
if (!IS_STRING(x)) return 1; // not equal
return %StringEquals(this, x);
}
}
if (IS_BOOLEAN(this)) {
if (!IS_BOOLEAN(x)) return 1; // not equal
if (this) return x ? 0 : 1;
else return x ? 1 : 0;
}
if (IS_NUMBER(this)) {
if (!IS_NUMBER(x)) return 1; // not equal
return %NumberEquals(this, x);
}
if (IS_UNDEFINED(this)) { // both undefined and undetectable
if (IS_UNDEFINED(this)) {
// Both undefined and undetectable.
return IS_UNDEFINED(x) ? 0 : 1;
}
// Objects, null, booleans and functions are all that's left.
// They can all be compared with a simple identity check.
return %_ObjectEquals(this, x) ? 0 : 1;
}