Add code for CPU feature detection and use it to detect SSE3 and SSE 4.1.

Add code for CPU feature detection and use it to detect SSE3 and SSE 4.1.

The Dart VM now requires at least SSE3 to build and run.

There is a new flag --use-sse41 (default:true) to disable the use of 
SSE 4.1 features manually. 
Committed: https://code.google.com/p/dart/source/detail?r=12897

[Florian Schneider, 2012-09-25 15:52:14]

Is there a way currently to detect if the VM is creating a snapshot? I didn't
find any, so I added an API function for that in this change.

[Florian Schneider, 2012-09-25 17:08:35]

Uploaded new version with Srdjan's feedback addressed.

[srdjan, 2012-09-25 17:12:25]

LGTM with comments

https://codereview.chromium.org/10990028/diff/9001/runtime/bin/gen_snapshot.cc
File runtime/bin/gen_snapshot.cc (right):

https://codereview.chromium.org/10990028/diff/9001/runtime/bin/gen_snapshot.c...
runtime/bin/gen_snapshot.cc:304: return 255;
Why not exit(255) as below?

https://codereview.chromium.org/10990028/diff/9001/runtime/vm/assembler_x64.cc
File runtime/vm/assembler_x64.cc (right):

https://codereview.chromium.org/10990028/diff/9001/runtime/vm/assembler_x64.c...
runtime/vm/assembler_x64.cc:46: // Get feature information in ECX:EDX and return
it in RAX.
RCX, RDX ?

https://codereview.chromium.org/10990028/diff/9001/runtime/vm/assembler_x64.h
File runtime/vm/assembler_x64.h (right):

https://codereview.chromium.org/10990028/diff/9001/runtime/vm/assembler_x64.h...
runtime/vm/assembler_x64.h:287: static bool initialized_;
in #ifdef DEBUG as on ia32?

[Florian Schneider, 2012-09-26 09:03:16]

https://codereview.chromium.org/10990028/diff/9001/runtime/bin/gen_snapshot.cc
File runtime/bin/gen_snapshot.cc (right):

https://codereview.chromium.org/10990028/diff/9001/runtime/bin/gen_snapshot.c...
runtime/bin/gen_snapshot.cc:304: return 255;
On 2012/09/25 17:12:25, srdjan wrote:
> Why not exit(255) as below?

Because I copied it from above where return 255 is used :)
return seems cleaner to me since it also invokes destructors of stack-allocated
objects (e.g. CommandLineOptions)

I don't think that it matters here. exit() is used in many functions in case of
an error, so it would mean changing a lot to get rid of it.

https://codereview.chromium.org/10990028/diff/9001/runtime/vm/assembler_x64.cc
File runtime/vm/assembler_x64.cc (right):

https://codereview.chromium.org/10990028/diff/9001/runtime/vm/assembler_x64.c...
runtime/vm/assembler_x64.cc:46: // Get feature information in ECX:EDX and return
it in RAX.
On 2012/09/25 17:12:25, srdjan wrote:
> RCX, RDX ?

That is intentional according to the spec: cpuid only affects the 32-bit half
EAX, EBX, ECX, EDX also in 64-bit mode. I'll add a comment.

https://codereview.chromium.org/10990028/diff/9001/runtime/vm/assembler_x64.h
File runtime/vm/assembler_x64.h (right):

https://codereview.chromium.org/10990028/diff/9001/runtime/vm/assembler_x64.h...
runtime/vm/assembler_x64.h:287: static bool initialized_;
On 2012/09/25 17:12:25, srdjan wrote:
> in #ifdef DEBUG as on ia32?

Done.