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Unified Diff: src/arm/codegen-arm.cc

Issue 2850043: Specialize GenericUnaryStub so that it knows whether it needs to... (Closed) Base URL: http://v8.googlecode.com/svn/branches/bleeding_edge/
Patch Set: '' Created 10 years, 5 months ago
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Index: src/arm/codegen-arm.cc
===================================================================
--- src/arm/codegen-arm.cc (revision 5015)
+++ src/arm/codegen-arm.cc (working copy)
@@ -5423,9 +5423,13 @@
frame_->EmitPush(r0); // r0 has result
} else {
- bool overwrite =
+ bool can_overwrite =
(node->expression()->AsBinaryOperation() != NULL &&
node->expression()->AsBinaryOperation()->ResultOverwriteAllowed());
+ UnaryOverwriteMode overwrite =
+ can_overwrite ? UNARY_OVERWRITE : UNARY_NO_OVERWRITE;
+
+ bool no_negative_zero = node->expression()->no_negative_zero();
Load(node->expression());
switch (op) {
case Token::NOT:
@@ -5436,7 +5440,10 @@
case Token::SUB: {
frame_->PopToR0();
- GenericUnaryOpStub stub(Token::SUB, overwrite);
+ GenericUnaryOpStub stub(
+ Token::SUB,
+ overwrite,
+ no_negative_zero ? kIgnoreNegativeZero : kStrictNegativeZero);
frame_->CallStub(&stub, 0);
frame_->EmitPush(r0); // r0 has result
break;
@@ -8899,24 +8906,31 @@
// Go slow case if the value of the expression is zero
// to make sure that we switch between 0 and -0.
- __ cmp(r0, Operand(0));
- __ b(eq, &slow);
+ if (negative_zero_ == kStrictNegativeZero) {
+ // If we have to check for zero, then we can check for the max negative
+ // smi while we are at it.
+ __ bic(ip, r0, Operand(0x80000000), SetCC);
+ __ b(eq, &slow);
+ __ rsb(r0, r0, Operand(0));
+ __ StubReturn(1);
+ } else {
+ // The value of the expression is a smi and 0 is OK for -0. Try
+ // optimistic subtraction '0 - value'.
+ __ rsb(r0, r0, Operand(0), SetCC);
+ __ StubReturn(1, vc);
+ // We don't have to reverse the optimistic neg since the only case
+ // where we fall through is the minimum negative Smi, which is the case
+ // where the neg leaves the register unchanged.
+ __ jmp(&slow); // Go slow on max negative Smi.
+ }
- // The value of the expression is a smi that is not zero. Try
- // optimistic subtraction '0 - value'.
- __ rsb(r1, r0, Operand(0), SetCC);
- __ b(vs, &slow);
-
- __ mov(r0, Operand(r1)); // Set r0 to result.
- __ b(&done);
-
__ bind(&try_float);
__ ldr(r1, FieldMemOperand(r0, HeapObject::kMapOffset));
__ AssertRegisterIsRoot(heap_number_map, Heap::kHeapNumberMapRootIndex);
__ cmp(r1, heap_number_map);
__ b(ne, &slow);
// r0 is a heap number. Get a new heap number in r1.
- if (overwrite_) {
+ if (overwrite_ == UNARY_OVERWRITE) {
__ ldr(r2, FieldMemOperand(r0, HeapNumber::kExponentOffset));
__ eor(r2, r2, Operand(HeapNumber::kSignMask)); // Flip sign.
__ str(r2, FieldMemOperand(r0, HeapNumber::kExponentOffset));
@@ -8949,7 +8963,7 @@
__ b(&done);
__ bind(&try_float);
- if (!overwrite_) {
+ if (!overwrite_ == UNARY_OVERWRITE) {
// Allocate a fresh heap number, but don't overwrite r0 until
// we're sure we can do it without going through the slow case
// that needs the value in r0.
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