Guard against D3D NaN/Infinity literals bug in color burn

Bug: skia:6857
Change-Id: Ibbbdd70483502d9e21429f86d3183e55bc007dd6
Reviewed-on: https://skia-review.googlesource.com/30101
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/src/gpu/glsl/GrGLSLBlend.cpp b/src/gpu/glsl/GrGLSLBlend.cpp
index 9d7a064b81..5afb984528 100644
--- a/src/gpu/glsl/GrGLSLBlend.cpp
+++ b/src/gpu/glsl/GrGLSLBlend.cpp
@@ -70,6 +70,12 @@ static void color_burn_component(GrGLSLFragmentBuilder* fsBuilder,
                                  const char* src,
                                  const char* dst,
                                  const char component) {
+    const char* divisorGuard = "";
+    const GrShaderCaps* shaderCaps = fsBuilder->getProgramBuilder()->shaderCaps();
+    if (shaderCaps->mustGuardDivisionEvenAfterExplicitZeroCheck()) {
+        divisorGuard = "+ 0.00000001";
+    }
+
     fsBuilder->codeAppendf("if (%s.a == %s.%c) {", dst, dst, component);
     fsBuilder->codeAppendf("%s.%c = %s.a * %s.a + %s.%c * (1.0 - %s.a) + %s.%c * (1.0 - %s.a);",
                            final, component, src, dst, src, component, dst, dst, component,
@@ -78,8 +84,8 @@ static void color_burn_component(GrGLSLFragmentBuilder* fsBuilder,
     fsBuilder->codeAppendf("%s.%c = %s.%c * (1.0 - %s.a);",
                            final, component, dst, component, src);
     fsBuilder->codeAppend("} else {");
-    fsBuilder->codeAppendf("float d = max(0.0, %s.a - (%s.a - %s.%c) * %s.a / %s.%c);",
-                           dst, dst, dst, component, src, src, component);
+    fsBuilder->codeAppendf("float d = max(0.0, %s.a - (%s.a - %s.%c) * %s.a / (%s.%c %s));",
+                           dst, dst, dst, component, src, src, component, divisorGuard);
     fsBuilder->codeAppendf("%s.%c = %s.a * d + %s.%c * (1.0 - %s.a) + %s.%c * (1.0 - %s.a);",
                            final, component, src, src, component, dst, dst, component, src);
     fsBuilder->codeAppend("}");