Ensure consistency of Math.sqrt on Intel platforms.

Ensure consistency of Math.sqrt on Intel platforms.

BUG=
TEST=regress-sqrt.js

Committed: https://code.google.com/p/v8/source/detail?r=11012

[Yang, 2012-03-12 12:12:47]

PTAL.

[Sven Panne, 2012-03-12 13:23:46]

http://codereview.chromium.org/9690010/diff/1/src/ia32/codegen-ia32.cc
File src/ia32/codegen-ia32.cc (right):

http://codereview.chromium.org/9690010/diff/1/src/ia32/codegen-ia32.cc#newcod...
src/ia32/codegen-ia32.cc:114: if (buffer == NULL || !V8::UseCrankshaft()) return
&sqrt;
Using !CpuFeatures::IsSupported(SSE2) here would guarantee consistency between
runs with Crankshaft and without it on SSE2 platforms.

http://codereview.chromium.org/9690010/diff/1/src/runtime.cc
File src/runtime.cc (right):

http://codereview.chromium.org/9690010/diff/1/src/runtime.cc#newcode7444
src/runtime.cc:7444: // Convert -0 to +0.
This comment refers to the last part of the ternary ? operator, not the whole
statement.

http://codereview.chromium.org/9690010/diff/1/src/runtime.cc#newcode7447
src/runtime.cc:7447: // Convert -0 to +0.
See above.

http://codereview.chromium.org/9690010/diff/1/src/x64/codegen-x64.cc
File src/x64/codegen-x64.cc (right):

http://codereview.chromium.org/9690010/diff/1/src/x64/codegen-x64.cc#newcode111
src/x64/codegen-x64.cc:111: if (buffer == NULL || !V8::UseCrankshaft()) return
&sqrt;
To guarantee consistency between runs with and without "--nouse-crankshaft", it
would be better to remove this check. x64 always has SSE.

[Yang, 2012-03-12 14:44:39]

Please take another look.

[Sven Panne, 2012-03-12 14:50:20]

LGTM with a tiny nit.

http://codereview.chromium.org/9690010/diff/5001/src/ia32/codegen-ia32.cc
File src/ia32/codegen-ia32.cc (right):

http://codereview.chromium.org/9690010/diff/5001/src/ia32/codegen-ia32.cc#new...
src/ia32/codegen-ia32.cc:120: ASSERT(CpuFeatures::IsSupported(SSE2));
I think we can safely remove this assertion.