Add gcc 4.7 support for AVX2

BUG=269
TEST=g++ -c source/row_posix.cc -I include/
R=nfullagar@google.com

Review URL: https://webrtc-codereview.appspot.com/2273006

git-svn-id: http://libyuv.googlecode.com/svn/trunk@797 16f28f9a-4ce2-e073-06de-1de4eb20be90

README.chromium

 Name: libyuv
 URL: http://code.google.com/p/libyuv/
-Version: 796
+Version: 797
 License: BSD
 License File: LICENSE
 

include/libyuv/row.h

@@ -142,11 +142,17 @@ extern "C" {
 #endif
 
 // The following are available on all x86 platforms, including NaCL, but
-// require VS2012, llvm or NaCL.
+// require VS2012, clang, gcc4.7 or NaCL.
 // Caveat: llvm 3.1 required, but does not provide a version.
+#if defined(__GNUC__) && (defined(__x86_64__) || defined(__i386__))
+/* Test for GCC >= 4.7.0 */
+#if (__GNUC__ > 4) || (__GNUC__ == 4 && (__GNUC_MINOR__ >= 7))
+#define GCC_HAS_AVX2 1
+#endif  // GNUC >= 4.7
+#endif  // __GNUC__
 #if !defined(LIBYUV_DISABLE_X86) && \
   ((defined(_M_IX86) && defined(_MSC_VER) && _MSC_VER >= 1700) || \
-  defined(__native_client__) || defined(__clang__))
+  defined(__native_client__) || defined(__clang__) || defined(GCC_HAS_AVX2))
 // Effects:
 #define HAS_ARGBPOLYNOMIALROW_AVX2
 #endif

include/libyuv/version.h

@@ -11,6 +11,6 @@
 #ifndef INCLUDE_LIBYUV_VERSION_H_  // NOLINT
 #define INCLUDE_LIBYUV_VERSION_H_
 
-#define LIBYUV_VERSION 796
+#define LIBYUV_VERSION 797
 
 #endif  // INCLUDE_LIBYUV_VERSION_H_  NOLINT

source/row_posix.cc

@@ -5915,7 +5915,8 @@ void ARGBPolynomialRow_AVX2(const uint8* src_argb,
   : "r"(poly)        // %3
   : "memory", "cc"
 #if defined(__SSE2__)
-    , "ymm0", "ymm1", "ymm2", "ymm3", "ymm4", "ymm5", "ymm6", "ymm7"
+// TODO(fbarchard): declare ymm usage when applicable.
+    , "xmm0", "xmm1", "xmm2", "xmm3", "xmm4", "xmm5", "xmm6", "xmm7"
 #endif
   );
 }