multi-thread fix: lock each entry points with a static var

we compare the current VP8GetCPUInfo pointer to the last used.
This is less code overall and each implementation is still
testable separately (by just changing VP8GetCPUInfo, but not
a separate threads!)

Change-Id: Ia13fa8ffc4561a884508f6ab71ed0d1b9f1ce59b

src/dsp/alpha_processing.c

@@ -347,7 +347,11 @@ extern void VP8FiltersInitMIPSdspR2(void);
 extern void WebPInitAlphaProcessingMIPSdspR2(void);
 extern void WebPInitAlphaProcessingSSE2(void);
 
+static volatile VP8CPUInfo last_cpuinfo_used = (VP8CPUInfo)&last_cpuinfo_used;
+
 WEBP_TSAN_IGNORE_FUNCTION void WebPInitAlphaProcessing(void) {
+  if (last_cpuinfo_used == VP8GetCPUInfo) return;
+
   WebPMultARGBRow = WebPMultARGBRowC;
   WebPMultRow = WebPMultRowC;
   WebPApplyAlphaMultiply = ApplyAlphaMultiply;
@@ -370,4 +374,5 @@ WEBP_TSAN_IGNORE_FUNCTION void WebPInitAlphaProcessing(void) {
     }
 #endif
   }
+  last_cpuinfo_used = VP8GetCPUInfo;
 }

src/dsp/argb.c

@@ -42,7 +42,11 @@ void (*VP8PackRGB)(const uint8_t*, const uint8_t*, const uint8_t*,
 
 extern void VP8EncDspARGBInitMIPSdspR2(void);
 
+static volatile VP8CPUInfo last_cpuinfo_used = (VP8CPUInfo)&last_cpuinfo_used;
+
 WEBP_TSAN_IGNORE_FUNCTION void VP8EncDspARGBInit(void) {
+  if (last_cpuinfo_used == VP8GetCPUInfo) return;
+
   VP8PackARGB = PackARGB;
   VP8PackRGB = PackRGB;
 
@@ -54,4 +58,5 @@ WEBP_TSAN_IGNORE_FUNCTION void VP8EncDspARGBInit(void) {
     }
 #endif
   }
+  last_cpuinfo_used = VP8GetCPUInfo;
 }

src/dsp/dec.c

@@ -684,7 +684,11 @@ extern void VP8DspInitNEON(void);
 extern void VP8DspInitMIPS32(void);
 extern void VP8DspInitMIPSdspR2(void);
 
+static volatile VP8CPUInfo last_cpuinfo_used = (VP8CPUInfo)&last_cpuinfo_used;
+
 WEBP_TSAN_IGNORE_FUNCTION void VP8DspInit(void) {
+  if (last_cpuinfo_used == VP8GetCPUInfo) return;
+
   VP8InitClipTables();
 
   VP8TransformWHT = TransformWHT;
@@ -749,5 +753,5 @@ WEBP_TSAN_IGNORE_FUNCTION void VP8DspInit(void) {
     }
 #endif
   }
+  last_cpuinfo_used = VP8GetCPUInfo;
 }
-

src/dsp/enc.c

@@ -727,7 +727,11 @@ extern void VP8EncDspInitNEON(void);
 extern void VP8EncDspInitMIPS32(void);
 extern void VP8EncDspInitMIPSdspR2(void);
 
+static volatile VP8CPUInfo last_cpuinfo_used = (VP8CPUInfo)&last_cpuinfo_used;
+
 WEBP_TSAN_IGNORE_FUNCTION void VP8EncDspInit(void) {
+  if (last_cpuinfo_used == VP8GetCPUInfo) return;
+
   VP8DspInit();  // common inverse transforms
   InitTables();
 
@@ -779,4 +783,5 @@ WEBP_TSAN_IGNORE_FUNCTION void VP8EncDspInit(void) {
     }
 #endif
   }
+  last_cpuinfo_used = VP8GetCPUInfo;
 }

src/dsp/lossless.c

@@ -1745,7 +1745,11 @@ extern void VP8LDspInitNEON(void);
 extern void VP8LDspInitMIPS32(void);
 extern void VP8LDspInitMIPSdspR2(void);
 
+static volatile VP8CPUInfo last_cpuinfo_used = (VP8CPUInfo)&last_cpuinfo_used;
+
 WEBP_TSAN_IGNORE_FUNCTION void VP8LDspInit(void) {
+  if (last_cpuinfo_used == VP8GetCPUInfo) return;
+
   memcpy(VP8LPredictors, kPredictorsC, sizeof(VP8LPredictors));
 
   VP8LSubtractGreenFromBlueAndRed = VP8LSubtractGreenFromBlueAndRed_C;
@@ -1797,6 +1801,7 @@ WEBP_TSAN_IGNORE_FUNCTION void VP8LDspInit(void) {
     }
 #endif
   }
+  last_cpuinfo_used = VP8GetCPUInfo;
 }
 
 //------------------------------------------------------------------------------

src/dsp/upsampling.c

@@ -173,7 +173,11 @@ WebPYUV444Converter WebPYUV444Converters[MODE_LAST];
 
 extern WEBP_TSAN_IGNORE_FUNCTION void WebPInitYUV444ConvertersMIPSdspR2(void);
 
+static volatile VP8CPUInfo last_cpuinfo_used1 = (VP8CPUInfo)&last_cpuinfo_used1;
+
 WEBP_TSAN_IGNORE_FUNCTION void WebPInitYUV444Converters(void) {
+  if (last_cpuinfo_used1 == VP8GetCPUInfo) return;
+
   WebPYUV444Converters[MODE_RGB]       = Yuv444ToRgb;
   WebPYUV444Converters[MODE_RGBA]      = Yuv444ToRgba;
   WebPYUV444Converters[MODE_BGR]       = Yuv444ToBgr;
@@ -193,6 +197,7 @@ WEBP_TSAN_IGNORE_FUNCTION void WebPInitYUV444Converters(void) {
     }
 #endif
   }
+  last_cpuinfo_used1 = VP8GetCPUInfo;
 }
 
 //------------------------------------------------------------------------------
@@ -202,7 +207,11 @@ extern WEBP_TSAN_IGNORE_FUNCTION void WebPInitUpsamplersSSE2(void);
 extern WEBP_TSAN_IGNORE_FUNCTION void WebPInitUpsamplersNEON(void);
 extern WEBP_TSAN_IGNORE_FUNCTION void WebPInitUpsamplersMIPSdspR2(void);
 
+static volatile VP8CPUInfo last_cpuinfo_used2 = (VP8CPUInfo)&last_cpuinfo_used2;
+
 WEBP_TSAN_IGNORE_FUNCTION void WebPInitUpsamplers(void) {
+  if (last_cpuinfo_used2 == VP8GetCPUInfo) return;
+
 #ifdef FANCY_UPSAMPLING
   WebPUpsamplers[MODE_RGB]       = UpsampleRgbLinePair;
   WebPUpsamplers[MODE_RGBA]      = UpsampleRgbaLinePair;
@@ -235,6 +244,7 @@ WEBP_TSAN_IGNORE_FUNCTION void WebPInitUpsamplers(void) {
 #endif
   }
 #endif  // FANCY_UPSAMPLING
+  last_cpuinfo_used2 = VP8GetCPUInfo;
 }
 
 //------------------------------------------------------------------------------

src/dsp/yuv.c

@@ -124,7 +124,11 @@ extern WEBP_TSAN_IGNORE_FUNCTION void WebPInitSamplersSSE2(void);
 extern WEBP_TSAN_IGNORE_FUNCTION void WebPInitSamplersMIPS32(void);
 extern WEBP_TSAN_IGNORE_FUNCTION void WebPInitSamplersMIPSdspR2(void);
 
+static volatile VP8CPUInfo last_cpuinfo_used = (VP8CPUInfo)&last_cpuinfo_used;
+
 WEBP_TSAN_IGNORE_FUNCTION void WebPInitSamplers(void) {
+  if (last_cpuinfo_used == VP8GetCPUInfo) return;
+
   WebPSamplers[MODE_RGB]       = YuvToRgbRow;
   WebPSamplers[MODE_RGBA]      = YuvToRgbaRow;
   WebPSamplers[MODE_BGR]       = YuvToBgrRow;
@@ -155,6 +159,7 @@ WEBP_TSAN_IGNORE_FUNCTION void WebPInitSamplers(void) {
     }
 #endif  // WEBP_USE_MIPS_DSP_R2
   }
+  last_cpuinfo_used = VP8GetCPUInfo;
 }
 
 //-----------------------------------------------------------------------------