commit 4d7ac49dcae8c58608813d4d208d60e5a247c9e3
author John Stiles <johnstiles@google.com> Tue Mar 09 20:16:43 2021 -0500
committer Skia Commit-Bot <skia-commit-bot@chromium.org> Wed Mar 10 16:03:18 2021 +0000
tree 33607968532ac4aaa073255936d971c5c7ec676f
parent 38847cda8969360187bb838532a9a7e3367f9964

Declare outputColor and outputCoverage inside emitCode.

This is useful because it allows the variables to be declared as `const`
when they are trivial values like `half4(1)`. This enables the constant
folder to simplify or eliminate them. In most cases, this is only a
small benefit, as you'd expect a competent GPU driver to do the same.
However, Mali-400 can benefit significantly from optimizing away the
multiplication against a constant half4(1) coverage in Porter-Duff.

Mali-400 performance is back to normal: http://screen/3cDxdaGkYE8oBcS

Change-Id: I21fd23f91f747079cd05b082f7b3444aeabafb93
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/382476
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>

src/gpu/effects/GrDistanceFieldGeoProc.cpp

diff --git a/src/gpu/effects/GrDistanceFieldGeoProc.cpp b/src/gpu/effects/GrDistanceFieldGeoProc.cpp
index c79a207..1a307e9 100644
--- a/src/gpu/effects/GrDistanceFieldGeoProc.cpp
+++ b/src/gpu/effects/GrDistanceFieldGeoProc.cpp
@@ -53,6 +53,7 @@
 #endif
 
         // Setup pass through color
+        fragBuilder->codeAppendf("half4 %s;\n", args.fOutputColor);
         varyingHandler->addPassThroughAttribute(dfTexEffect.inColor(), args.fOutputColor);
 
         // Setup position
@@ -152,7 +153,7 @@
             fragBuilder->codeAppend("half val = smoothstep(-afwidth, afwidth, distance);");
         }
 
-        fragBuilder->codeAppendf("%s = half4(val);", args.fOutputCoverage);
+        fragBuilder->codeAppendf("half4 %s = half4(val);", args.fOutputCoverage);
     }
 
     void setData(const GrGLSLProgramDataManager& pdman, const GrPrimitiveProcessor& proc) override {
@@ -342,6 +343,7 @@
                                  &texIdx, &st);
 
         // setup pass through color
+        fragBuilder->codeAppendf("half4 %s;", args.fOutputColor);
         varyingHandler->addPassThroughAttribute(dfPathEffect.inColor(), args.fOutputColor);
 
         if (dfPathEffect.matrix().hasPerspective()) {
@@ -436,7 +438,7 @@
             fragBuilder->codeAppend("half val = smoothstep(-afwidth, afwidth, distance);");
         }
 
-        fragBuilder->codeAppendf("%s = half4(val);", args.fOutputCoverage);
+        fragBuilder->codeAppendf("half4 %s = half4(val);", args.fOutputCoverage);
     }
 
     void setData(const GrGLSLProgramDataManager& pdman, const GrPrimitiveProcessor& proc) override {
@@ -604,6 +606,7 @@
         GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
 
         // setup pass through color
+        fragBuilder->codeAppendf("half4 %s;\n", args.fOutputColor);
         varyingHandler->addPassThroughAttribute(dfTexEffect.inColor(), args.fOutputColor);
 
         // Setup position
@@ -735,13 +738,13 @@
         // doing gamma-correct rendering (to an sRGB or F16 buffer), then we actually want distance
         // mapped linearly to coverage, so use a linear step:
         if (isGammaCorrect) {
-            fragBuilder->codeAppendf("%s = "
-                "half4(saturate((distance + half3(afwidth)) / half3(2.0 * afwidth)), 1.0);",
-                args.fOutputCoverage);
+            fragBuilder->codeAppendf("half4 %s = "
+                    "half4(saturate((distance + half3(afwidth)) / half3(2.0 * afwidth)), 1.0);",
+                    args.fOutputCoverage);
         } else {
             fragBuilder->codeAppendf(
-                "%s = half4(smoothstep(half3(-afwidth), half3(afwidth), distance), 1.0);",
-                args.fOutputCoverage);
+                    "half4 %s = half4(smoothstep(half3(-afwidth), half3(afwidth), distance), 1.0);",
+                    args.fOutputCoverage);
         }
     }