From 7ca217b3b2b691d09195924c0f1fa03c10e9858f Mon Sep 17 00:00:00 2001
From: Mike Klein <mtklein@google.com>
Date: Mon, 13 Aug 2018 11:03:08 -0400
Subject: [PATCH] avoid illegal enum values in GrGLGpu

This tracks the state of the blend equation and coefficients
using an out-of-band bool rather than an illegal enum value.

This was caught by -fsanitize=enum.

This CL doesn't change the size of fHWBlendState.

Change-Id: I8dbc8aaaa07e82186c148ceb19590390051eb296
Reviewed-on: https://skia-review.googlesource.com/146962
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
---
 src/gpu/gl/GrGLGpu.cpp |  7 +++++--
 src/gpu/gl/GrGLGpu.h   | 10 +++++++---
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/src/gpu/gl/GrGLGpu.cpp b/src/gpu/gl/GrGLGpu.cpp
index 2df6382067..6c4ec8de1f 100644
--- a/src/gpu/gl/GrGLGpu.cpp
+++ b/src/gpu/gl/GrGLGpu.cpp
@@ -2639,9 +2639,10 @@ void GrGLGpu::flushBlend(const GrXferProcessor::BlendInfo& blendInfo, const GrSw
         fHWBlendState.fEnabled = kYes_TriState;
     }
 
-    if (fHWBlendState.fEquation != equation) {
+    if (!fHWBlendState.fEquationValid || fHWBlendState.fEquation != equation) {
         GL_CALL(BlendEquation(gXfermodeEquation2Blend[equation]));
         fHWBlendState.fEquation = equation;
+        fHWBlendState.fEquationValid = true;
     }
 
     if (GrBlendEquationIsAdvanced(equation)) {
@@ -2650,11 +2651,13 @@ void GrGLGpu::flushBlend(const GrXferProcessor::BlendInfo& blendInfo, const GrSw
         return;
     }
 
-    if (fHWBlendState.fSrcCoeff != srcCoeff || fHWBlendState.fDstCoeff != dstCoeff) {
+    if (!fHWBlendState.fCoeffsValid || fHWBlendState.fSrcCoeff != srcCoeff
+                                    || fHWBlendState.fDstCoeff != dstCoeff) {
         GL_CALL(BlendFunc(gXfermodeCoeff2Blend[srcCoeff],
                           gXfermodeCoeff2Blend[dstCoeff]));
         fHWBlendState.fSrcCoeff = srcCoeff;
         fHWBlendState.fDstCoeff = dstCoeff;
+        fHWBlendState.fCoeffsValid = true;
     }
 
     if ((BlendCoeffReferencesConstant(srcCoeff) || BlendCoeffReferencesConstant(dstCoeff))) {
diff --git a/src/gpu/gl/GrGLGpu.h b/src/gpu/gl/GrGLGpu.h
index 5ac3f84e07..3e798536dc 100644
--- a/src/gpu/gl/GrGLGpu.h
+++ b/src/gpu/gl/GrGLGpu.h
@@ -558,13 +558,17 @@ private:
         GrBlendCoeff    fSrcCoeff;
         GrBlendCoeff    fDstCoeff;
         GrColor         fConstColor;
+
+        bool            fEquationValid;
+        bool            fCoeffsValid;
         bool            fConstColorValid;
+        /* there's a spare byte here */
+
         TriState        fEnabled;
 
         void invalidate() {
-            fEquation = static_cast<GrBlendEquation>(-1);
-            fSrcCoeff = static_cast<GrBlendCoeff>(-1);
-            fDstCoeff = static_cast<GrBlendCoeff>(-1);
+            fEquationValid   = false;
+            fCoeffsValid     = false;
             fConstColorValid = false;
             fEnabled = kUnknown_TriState;
         }