Revision: 19698
Author: [email protected]
Date: Fri Mar 7 08:36:13 2014 UTC
Log: Optimistically untag the input in tagged-to-i.
Also drop redundant jmp instruction in deferred code.
[email protected]
Review URL: https://codereview.chromium.org/182723003
http://code.google.com/p/v8/source/detail?r=19698
Modified:
/branches/bleeding_edge/src/ia32/lithium-codegen-ia32.cc
=======================================
--- /branches/bleeding_edge/src/ia32/lithium-codegen-ia32.cc Thu Mar 6
13:07:51 2014 UTC
+++ /branches/bleeding_edge/src/ia32/lithium-codegen-ia32.cc Fri Mar 7
08:36:13 2014 UTC
@@ -5249,6 +5249,10 @@
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;
@@ -5278,7 +5282,6 @@
__ 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)
@@ -5318,9 +5321,13 @@
} 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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