Improved x86 SSE build and run-time checks.

include/core/SkPreConfig.h

Index: include/core/SkPreConfig.h
diff --git a/include/core/SkPreConfig.h b/include/core/SkPreConfig.h
index 9aefc2d64a6abcd4fc3ffae86896eaa89a5039ea..a91ddf2bf84505c7fbee75c7fe169368f982afaf 100644
--- a/include/core/SkPreConfig.h
+++ b/include/core/SkPreConfig.h
@@ -123,12 +123,18 @@
 #define SK_CPU_SSE_LEVEL_SSE2     20
 #define SK_CPU_SSE_LEVEL_SSE3     30
 #define SK_CPU_SSE_LEVEL_SSSE3    31
+#define SK_CPU_SSE_LEVEL_SSE41    41
+#define SK_CPU_SSE_LEVEL_SSE42    42
 
 // Are we in GCC?
 #ifndef SK_CPU_SSE_LEVEL
     // These checks must be done in descending order to ensure we set the highest
     // available SSE level.
-    #if defined(__SSSE3__)
+    #if defined(__SSE4_2__) || defined(__SSE4__)

[mtklein, 2014/05/07 17:34:41]

Are there compilers where __SSE4_2__ isn't defined but __SSE4__ is for SSE 4.2? 
Just curious about the need for the extra condition here.  Clang and GCC's
immintrin.h just seem to check __SSE4_2__.

[henrik.smiding, 2014/05/08 11:02:46]

As far as I can remember gcc used to set __SSE4__ as well, if you specified
-msse4. This does not seem to be the case with the current gcc version, though.
There's also a fair amount of hits in code, if you google "__SSE4__". They might
have been set manually, though.
I see no problem with removing this.

[henrik.smiding, 2014/05/08 11:02:46]

Done.

+        #define SK_CPU_SSE_LEVEL    SK_CPU_SSE_LEVEL_SSE42
+    #elif defined(__SSE4_1__)
+        #define SK_CPU_SSE_LEVEL    SK_CPU_SSE_LEVEL_SSE41
+    #elif defined(__SSSE3__)
         #define SK_CPU_SSE_LEVEL    SK_CPU_SSE_LEVEL_SSSE3
     #elif defined(__SSE3__)
         #define SK_CPU_SSE_LEVEL    SK_CPU_SSE_LEVEL_SSE3