Reviewers: Sven Panne,
Message:
PTAL
Description:
Optimistically untag the input in tagged-to-i.
Also drop redundant jmp instruction in deferred code.
Please review this at https://codereview.chromium.org/182723003/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files (+10, -3 lines):
M src/ia32/lithium-codegen-ia32.cc
Index: src/ia32/lithium-codegen-ia32.cc
diff --git a/src/ia32/lithium-codegen-ia32.cc
b/src/ia32/lithium-codegen-ia32.cc
index
ed5bd47a403101735846ab11fefd8e08fa670594..d1c59ac693564c473ebf41850bd831015878e16c
100644
--- a/src/ia32/lithium-codegen-ia32.cc
+++ b/src/ia32/lithium-codegen-ia32.cc
@@ -5244,6 +5244,10 @@ void LCodeGen::EmitNumberUntagD(Register input_reg,
void LCodeGen::DoDeferredTaggedToI(LTaggedToI* instr, Label* done) {
Register input_reg = ToRegister(instr->value());
+ // The input was optimistically untagged; revert it.
+ STATIC_ASSERT(kSmiTagSize == 1);
+ __ lea(input_reg, Operand(input_reg, times_2, kHeapObjectTag));
+
if (instr->truncating()) {
Label no_heap_number, check_bools, check_false;
@@ -5273,7 +5277,6 @@ void LCodeGen::DoDeferredTaggedToI(LTaggedToI* instr,
Label* done) {
__ RecordComment("Deferred TaggedToI: cannot truncate");
DeoptimizeIf(not_equal, instr->environment());
__ Set(input_reg, Immediate(0));
- __ jmp(done);
} else {
Label bailout;
XMMRegister scratch = (instr->temp() != NULL)
@@ -5313,9 +5316,13 @@ void LCodeGen::DoTaggedToI(LTaggedToI* instr) {
} else {
DeferredTaggedToI* deferred =
new(zone()) DeferredTaggedToI(this, instr, x87_stack_);
-
- __ JumpIfNotSmi(input_reg, deferred->entry());
+ // Optimistically untag the input.
+ // If the input is a HeapObject, SmiUntag will set the carry flag.
+ STATIC_ASSERT(kSmiTagSize == 1 && kSmiTag == 0);
__ SmiUntag(input_reg);
+ // Branch to deferred code if the input was tagged.
+ // The deferred code will take care of restoring the tag.
+ __ j(carry, deferred->entry());
__ bind(deferred->exit());
}
}
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