Make GrGLConfigConversionEffect work for Imagination and some other GPUs.

src/gpu/effects/GrConfigConversionEffect.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrConfigConversionEffect.h"
 #include "GrContext.h"
 #include "GrTBackendEffectFactory.h"
@@ skipping 12 matching lines @@
         fPMConversion = effect.pmConversion();
     }
 
     virtual void emitCode(GrGLShaderBuilder* builder,
                           const GrDrawEffect&,
                           const GrEffectKey& key,
                           const char* outputColor,
                           const char* inputColor,
                           const TransformedCoordsArray& coords,
                           const TextureSamplerArray& samplers) SK_OVERRIDE {
-        builder->fsCodeAppendf("\t\t%s = ", outputColor);
+        // Using highp for GLES here in order to avoid some precision issues on specific GPUs.
+        GrGLShaderVar tmpVar("tmpColor", kVec4f_GrSLType, 0, GrGLShaderVar::kHigh_Precision);
+        SkString tmpDecl;
+        tmpVar.appendDecl(builder->ctxInfo(), &tmpDecl);
+        builder->fsCodeAppendf("%s;", tmpDecl.c_str());
+
+        builder->fsCodeAppendf("%s = ", tmpVar.c_str());
         builder->fsAppendTextureLookup(samplers[0], coords[0].c_str(), coords[0].type());
-        builder->fsCodeAppend(";\n");
+        builder->fsCodeAppend(";");
+
         if (GrConfigConversionEffect::kNone_PMConversion == fPMConversion) {
             SkASSERT(fSwapRedAndBlue);
-            builder->fsCodeAppendf("\t%s = %s.bgra;\n", outputColor, outputColor);
+            builder->fsCodeAppendf("%s = %s.bgra;", outputColor, tmpVar.c_str());
         } else {
             const char* swiz = fSwapRedAndBlue ? "bgr" : "rgb";
             switch (fPMConversion) {
                 case GrConfigConversionEffect::kMulByAlpha_RoundUp_PMConversion:
                     builder->fsCodeAppendf(
-                        "\t\t%s = vec4(ceil(%s.%s * %s.a * 255.0) / 255.0, %s.a);\n",
-                        outputColor, outputColor, swiz, outputColor, outputColor);
+                        "%s = vec4(ceil(%s.%s * %s.a * 255.0) / 255.0, %s.a);",
+                        tmpVar.c_str(), tmpVar.c_str(), swiz, tmpVar.c_str(), tmpVar.c_str());
                     break;
                 case GrConfigConversionEffect::kMulByAlpha_RoundDown_PMConversion:
                     // Add a compensation(0.001) here to avoid the side effect of the floor operation.
                     // In Intel GPUs, the integer value converted from floor(%s.r * 255.0) / 255.0
                     // is less than the integer value converted from  %s.r by 1 when the %s.r is
                     // converted from the integer value 2^n, such as 1, 2, 4, 8, etc.
                     builder->fsCodeAppendf(
-                        "\t\t%s = vec4(floor(%s.%s * %s.a * 255.0 + 0.001) / 255.0, %s.a);\n",
-                        outputColor, outputColor, swiz, outputColor, outputColor);
+                        "%s = vec4(floor(%s.%s * %s.a * 255.0 + 0.001) / 255.0, %s.a);",
+                        tmpVar.c_str(), tmpVar.c_str(), swiz, tmpVar.c_str(), tmpVar.c_str());
                     break;
                 case GrConfigConversionEffect::kDivByAlpha_RoundUp_PMConversion:
-                    builder->fsCodeAppendf("\t\t%s = %s.a <= 0.0 ? vec4(0,0,0,0) : vec4(ceil(%s.%s / %s.a * 255.0) / 255.0, %s.a);\n",
-                        outputColor, outputColor, outputColor, swiz, outputColor, outputColor);
+                    builder->fsCodeAppendf(
+                        "%s = %s.a <= 0.0 ? vec4(0,0,0,0) : vec4(ceil(%s.%s / %s.a * 255.0) / 255.0, %s.a);",
+                        tmpVar.c_str(), tmpVar.c_str(), tmpVar.c_str(), swiz, tmpVar.c_str(), tmpVar.c_str());
                     break;
                 case GrConfigConversionEffect::kDivByAlpha_RoundDown_PMConversion:
-                    builder->fsCodeAppendf("\t\t%s = %s.a <= 0.0 ? vec4(0,0,0,0) : vec4(floor(%s.%s / %s.a * 255.0) / 255.0, %s.a);\n",
-                        outputColor, outputColor, outputColor, swiz, outputColor, outputColor);
+                    builder->fsCodeAppendf(
+                        "%s = %s.a <= 0.0 ? vec4(0,0,0,0) : vec4(floor(%s.%s / %s.a * 255.0) / 255.0, %s.a);",
+                        tmpVar.c_str(), tmpVar.c_str(), tmpVar.c_str(), swiz, tmpVar.c_str(), tmpVar.c_str());
                     break;
                 default:
                     SkFAIL("Unknown conversion op.");
                     break;
             }
+            builder->fsCodeAppendf("%s = %s;", outputColor, tmpVar.c_str());
         }
         SkString modulate;
         GrGLSLMulVarBy4f(&modulate, 2, outputColor, inputColor);
         builder->fsCodeAppend(modulate.c_str());
     }
 
     static inline void GenKey(const GrDrawEffect& drawEffect, const GrGLCaps&,
                               GrEffectKeyBuilder* b) {
         const GrConfigConversionEffect& conv = drawEffect.castEffect<GrConfigConversionEffect>();
         uint32_t key = (conv.swapsRedAndBlue() ? 0 : 1) | (conv.pmConversion() << 1);
@@ skipping 187 matching lines @@
             kNone_PMConversion != pmConversion) {
             // The PM conversions assume colors are 0..255
             return NULL;
         }
         return SkNEW_ARGS(GrConfigConversionEffect, (texture,
                                                      swapRedAndBlue,
                                                      pmConversion,
                                                      matrix));
     }
 }