Fix race in supports_simd().

src/opts/opts_check_x86.cpp

Index: src/opts/opts_check_x86.cpp
diff --git a/src/opts/opts_check_x86.cpp b/src/opts/opts_check_x86.cpp
index 55eb843312746b7e475eb776a6d35549e7553884..8fec2ba69c528040cbb02c2bd603bd1e00120a6f 100644
--- a/src/opts/opts_check_x86.cpp
+++ b/src/opts/opts_check_x86.cpp
@@ -16,6 +16,7 @@
 #include "SkBlitRow_opts_SSE4.h"
 #include "SkBlurImage_opts_SSE2.h"
 #include "SkBlurImage_opts_SSE4.h"
+#include "SkLazyPtr.h"
 #include "SkMorphology_opts.h"
 #include "SkMorphology_opts_SSE2.h"
 #include "SkRTConf.h"
@@ -79,22 +80,29 @@ static inline void getcpuid(int info_type, int info[4]) {
 /* Fetch the SIMD level directly from the CPU, at run-time.
  * Only checks the levels needed by the optimizations in this file.
  */
-static int get_SIMD_level() {
-    int cpu_info[4] = { 0 };
-
+namespace {  // get_SIMD_level() technically must have external linkage, so no static.
+int* get_SIMD_level() {
+    int cpu_info[4] = { 0, 0, 0, 0 };
     getcpuid(1, cpu_info);
+
+    int* level = SkNEW(int);
+
     if ((cpu_info[2] & (1<<20)) != 0) {
-        return SK_CPU_SSE_LEVEL_SSE42;
+        *level = SK_CPU_SSE_LEVEL_SSE42;
     } else if ((cpu_info[2] & (1<<19)) != 0) {
-        return SK_CPU_SSE_LEVEL_SSE41;
+        *level = SK_CPU_SSE_LEVEL_SSE41;
     } else if ((cpu_info[2] & (1<<9)) != 0) {
-        return SK_CPU_SSE_LEVEL_SSSE3;
+        *level = SK_CPU_SSE_LEVEL_SSSE3;
     } else if ((cpu_info[3] & (1<<26)) != 0) {
-        return SK_CPU_SSE_LEVEL_SSE2;
+        *level = SK_CPU_SSE_LEVEL_SSE2;
     } else {
-        return 0;
+        *level = 0;
     }
+    return level;
 }
+} // namespace
+
+SK_DECLARE_STATIC_LAZY_PTR(int, gSIMDLevel, get_SIMD_level);
 
 /* Verify that the requested SIMD level is supported in the build.
  * If not, check if the platform supports it.
@@ -115,8 +123,7 @@ static inline bool supports_simd(int minLevel) {
          */
         return false;
 #else
-        static int gSIMDLevel = get_SIMD_level();
-        return (minLevel <= gSIMDLevel);
+        return minLevel <= *gSIMDLevel.get();
 #endif
     }
 }