Porting Math.pow changes to x64.

Porting Math.pow changes to x64.

TEST=math-pow.js, regress-397.js

Committed: http://code.google.com/p/v8/source/detail?r=10185

[Yang, 2011-12-06 14:47:23]

PTAL.

This should essentially be the same as the ia32 version, except that base is now
stored in xmm2 and exponent is stored in xmm1 because the runtime call requires
base in xmm0 and exponent in xmm2, but xmm0 cannot be reserved in hydrogen.

[Yang, 2011-12-06 16:16:38]

Uploaded patch set to change register names.

[ulan, 2011-12-06 17:38:04]

LGTM if the comments are addressed.

http://codereview.chromium.org/8821019/diff/10/src/ia32/code-stubs-ia32.cc
File src/ia32/code-stubs-ia32.cc (right):

http://codereview.chromium.org/8821019/diff/10/src/ia32/code-stubs-ia32.cc#ne...
src/ia32/code-stubs-ia32.cc:2978: 
Moving the empty line before the bind would be better.

http://codereview.chromium.org/8821019/diff/10/src/ia32/code-stubs-ia32.cc#ne...
src/ia32/code-stubs-ia32.cc:3078: __ addsd(double_exponent, double_base);  //
Convert -0 to +0.
addsd(double_base, double_exponent) would allow you to use double_base later.

http://codereview.chromium.org/8821019/diff/10/src/ia32/code-stubs-ia32.cc#ne...
src/ia32/code-stubs-ia32.cc:3112: __ test_b(exponent, 0x5F);  // We check for
all but precision exception.
Assuming that exponent == eax.

http://codereview.chromium.org/8821019/diff/10/src/x64/code-stubs-x64.cc
File src/x64/code-stubs-x64.cc (right):

http://codereview.chromium.org/8821019/diff/10/src/x64/code-stubs-x64.cc#newc...
src/x64/code-stubs-x64.cc:2128: __ addsd(double_exponent, double_base);  //
Convert -0 to +0.
addsd(double_base, double_exponent) would allow you to use double_base later.

http://codereview.chromium.org/8821019/diff/2002/src/ia32/lithium-codegen-ia3...
File src/ia32/lithium-codegen-ia32.cc (right):

http://codereview.chromium.org/8821019/diff/2002/src/ia32/lithium-codegen-ia3...
src/ia32/lithium-codegen-ia32.cc:2995:
ASSERT(!instr->InputAt(1)->IsDoubleRegister() ||
Don't forget to change the assertions to reflect register changes.