Focus disabled optimizations on just BGRAConvolve2D, and only 32-bit.

Last CL accidentally disabled autovectorization on 64-bit builds too.
This fixes that.

BUG=skia:2575
R=rmistry@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/353823005

gyp/core.gyp

@@ -31,11 +31,6 @@
       ],
       'msvs_disabled_warnings': [4244, 4267,4345, 4390, 4554, 4800],
       'conditions': [
-        [ 'skia_arch_type == "x86"', {
-          # GCC autovectorization makes some GMs flaky on 32-bit release builds.
-          # skbug.com/2575.   This bug is likely somewhere here in src/core.
-          'cflags': [ '-fno-tree-vectorize' ]
-        }],
         [ 'skia_os in ["linux", "freebsd", "openbsd", "solaris", "chromeos"]', {
           'link_settings': {
             'libraries': [

src/core/SkConvolver.cpp

@@ -330,6 +330,11 @@ const SkConvolutionFilter1D::ConvolutionFixed* SkConvolutionFilter1D::GetSingleF
     return &fFilterValues[filter.fDataLocation];
 }
 
+// There's a bug somewhere in here with GCC autovectorization (-ftree-vectorize) on 32 bit builds.
+// Dropping to -O2 disables -ftree-vectorize.  http://skbug.com/2575
+#if defined(__i386) && SK_HAS_ATTRIBUTE(optimize)
+    __attribute__((optimize("O2")))
+#endif
 void BGRAConvolve2D(const unsigned char* sourceData,
                     int sourceByteRowStride,
                     bool sourceHasAlpha,