Detect CRC32 instructions on ARMv8.

src/core/SkCpu.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkCpu_DEFINED
 #define SkCpu_DEFINED
 
 #include "SkTypes.h"
 
 struct SkCpu {
     enum {
         SSE1  = 1 << 0,
         SSE2  = 1 << 1,
         SSE3  = 1 << 2,
         SSSE3 = 1 << 3,
         SSE41 = 1 << 4,
         SSE42 = 1 << 5,
         AVX   = 1 << 6,
         F16C  = 1 << 7,
         FMA   = 1 << 8,
         AVX2  = 1 << 9,
     };
     enum {
         NEON     = 1 << 0,
         NEON_FMA = 1 << 1,
         VFP_FP16 = 1 << 2,
+        CRC32    = 1 << 3,
     };
 
     static void CacheRuntimeFeatures();
     static bool Supports(uint32_t);
 private:
     static uint32_t gCachedFeatures;
 };
 
 inline bool SkCpu::Supports(uint32_t mask) {
     uint32_t features = gCachedFeatures;
@@ skipping 32 matching lines @@
 
 #else
     #if defined(SK_ARM_HAS_NEON)
     features |= NEON;
     #endif
 
     #if defined(SK_CPU_ARM64)
     features |= NEON|NEON_FMA|VFP_FP16;
     #endif
 
+    #if defined(__ARM_FEATURE_CRC32)
+    features |= CRC32;
+    #endif
+
 #endif
     return (features & mask) == mask;
 }
 
 #endif//SkCpu_DEFINED