Improved x86 SSE build and run-time checks.

include/core/SkPreConfig.h

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef SkPreConfig_DEFINED
@@ skipping 105 matching lines @@
  *  SK_CPU_SSE_LEVEL
  *
  *  If defined, SK_CPU_SSE_LEVEL should be set to the highest supported level.
  *  On non-intel CPU this should be undefined.
  */
 
 #define SK_CPU_SSE_LEVEL_SSE1     10
 #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
     #elif defined(__SSE2__)
         #define SK_CPU_SSE_LEVEL    SK_CPU_SSE_LEVEL_SSE2
     #endif
 #endif
 
 // Are we in VisualStudio?
 #ifndef SK_CPU_SSE_LEVEL
@@ skipping 105 matching lines @@
  *
  * NOTE: Clang/ARM (r161757) does not support the 'optimize' attribute.
  */
 #if SK_HAS_ATTRIBUTE(optimize)
 #   define SK_ATTRIBUTE_OPTIMIZE_O1 __attribute__((optimize("O1")))
 #else
 #   define SK_ATTRIBUTE_OPTIMIZE_O1 /* nothing */
 #endif
 
 #endif