Fix regression caused by the generation of a shift stub during...

Fix regression caused by the generation of a shift stub during
snapshot creation in a better way.

Encode whether or not the stub should use sse3 instructions in the
minor key of the stub.  The stubs generated during snapshot creation
will have sse3 disabled, but they will not be found when sse3 is
enabled.  Therefore they will only affect the code generated as part
of the snapshot.

Committed: http://code.google.com/p/v8/source/detail?r=2705

[Kasper Lund, 2009-08-18 09:34:56]

LGTM, but I noticed similar code on x64. Apparently, it is possible (yet
unlikely) to have an x64 chip with no SSE3 support, so you need to fix that too.

Maybe while you're at it, you should double check that
CpuFeatures::IsSupported(CpuFeatures::SSE3) returns what you expect on x64
platforms?

[Mads Ager (chromium), 2009-08-18 09:46:20]

On 2009/08/18 09:34:56, Kasper Lund wrote:
> LGTM, but I noticed similar code on x64. Apparently, it is possible (yet
> unlikely) to have an x64 chip with no SSE3 support, so you need to fix that
too.

Good point, done.

> Maybe while you're at it, you should double check that
> CpuFeatures::IsSupported(CpuFeatures::SSE3) returns what you expect on x64
> platforms?

Double checked.  The x64 probing code looks fine.  The regression is there and
it is fixed by these changes.

Thanks!