Use a fixed input register where we require a byte register.

Use a fixed input register where we require a byte register.

Currently we can't specify a set of registers as a register constraint.
This change forces a fixed register (eax) in places that need
a byte register.

BUG=77752
Committed: http://code.google.com/p/v8/source/detail?r=7417

[danno, 2011-03-29 14:25:34]

here you go...

http://codereview.chromium.org/6708109/diff/3001/src/ia32/lithium-ia32.cc
File src/ia32/lithium-ia32.cc (right):

http://codereview.chromium.org/6708109/diff/3001/src/ia32/lithium-ia32.cc#new...
src/ia32/lithium-ia32.cc:1922: val = UseFixed(instr->value(), eax);
Good catch. Thanks :-)

http://codereview.chromium.org/6708109/diff/3001/src/x64/lithium-x64.cc
File src/x64/lithium-x64.cc (right):

http://codereview.chromium.org/6708109/diff/3001/src/x64/lithium-x64.cc#newco...
src/x64/lithium-x64.cc:1878: case kExternalPixelArray:
Doesn't pixel array still need to be a temp, since the clamping code overwrites
rax and you don't want to accidentally use it later expecting the contents to
still be val.

http://codereview.chromium.org/6708109/diff/3001/src/x64/lithium-x64.cc#newco...
src/x64/lithium-x64.cc:1882: val = UseFixed(instr->value(), rax);
Do you really need to use rax? On 64 bit the byte store should work for any
register with the REX prefix that's handled by the assembler?

[fschneider, 2011-03-29 14:43:58]

http://codereview.chromium.org/6708109/diff/3001/src/x64/lithium-x64.cc
File src/x64/lithium-x64.cc (right):

http://codereview.chromium.org/6708109/diff/3001/src/x64/lithium-x64.cc#newco...
src/x64/lithium-x64.cc:1878: case kExternalPixelArray:
On 2011/03/29 14:25:34, danno wrote:
> Doesn't pixel array still need to be a temp, since the clamping code
overwrites
> rax and you don't want to accidentally use it later expecting the contents to
> still be val. 

That would be ok, since UseFixed is always a fixed writable input register. The
naming of UseFixed is however not ideal.

http://codereview.chromium.org/6708109/diff/3001/src/x64/lithium-x64.cc#newco...
src/x64/lithium-x64.cc:1882: val = UseFixed(instr->value(), rax);
On 2011/03/29 14:25:34, danno wrote:
> Do you really need to use rax? On 64 bit the byte store should work for any
> register with the REX prefix that's handled by the assembler?

You're right. I didn't realize x64 allows that. I don't need to change anything
on x64 then.

[danno, 2011-03-29 15:12:26]

LGTM