Use cmov instructions to avoid some conditional branches in stub code....

Use cmov instructions to avoid some conditional branches in stub code.

This change improves the ConstructStub and the ArgumentsAccessStub slightly
by using the cmov instruction (if available) to eliminate a 
conditional branch. It only applies to the IA-32 and X64 platforms.



Committed: http://code.google.com/p/v8/source/detail?r=3537

[Kevin Millikin (Chromium), 2010-01-05 11:48:06]

LGTM.

http://codereview.chromium.org/519035/diff/3001/10
File src/ia32/codegen-ia32.cc (right):

http://codereview.chromium.org/519035/diff/3001/10#newcode7753
src/ia32/codegen-ia32.cc:7753: __ j(equal, &adaptor);
Couldn't you simplify this code to be

Label exit;
__ j(not_equal, &exit);
__ mov(eax, Operand(...));
__ bind(exit);

and reuse the ret instruction?

[fschneider, 2010-01-05 11:54:39]

http://codereview.chromium.org/519035/diff/3001/10
File src/ia32/codegen-ia32.cc (right):

http://codereview.chromium.org/519035/diff/3001/10#newcode7753
src/ia32/codegen-ia32.cc:7753: __ j(equal, &adaptor);
On 2010/01/05 11:48:06, Kevin Millikin wrote:
> Couldn't you simplify this code to be
> 
> Label exit;
> __ j(not_equal, &exit);
> __ mov(eax, Operand(...));
> __ bind(exit);
> 
> and reuse the ret instruction?

Done.