Workaround Mali static analysis bug

Comment describes it: Unless we do something to confuse their optimizer,
they will (incorrectly) deduce that uniform opaque color (modulated only
by a texture fetch) is always going to remain opaque. Then they skip
inserting their shader based blending code, turning SrcOver into Src.

Doing a max against zero is enough to squelch the optimization.

Bug: skia:
Change-Id: I74676cebb0b0c8d121da868dd8a88050e0cfcc0d
Reviewed-on: https://skia-review.googlesource.com/17924
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/gpu/GrShaderCaps.h b/include/gpu/GrShaderCaps.h
index e52bcf1c81..e5edc7ebea 100644
--- a/include/gpu/GrShaderCaps.h
+++ b/include/gpu/GrShaderCaps.h
@@ -161,6 +161,8 @@ public:
     // On MacBook, geometry shaders break if they have more than one invocation.
     bool mustImplementGSInvocationsWithLoop() const { return fMustImplementGSInvocationsWithLoop; }
 
+    bool mustObfuscateUniformColor() const { return fMustObfuscateUniformColor; }
+
     // Returns the string of an extension that must be enabled in the shader to support
     // derivatives. If nullptr is returned then no extension needs to be enabled. Before calling
     // this function, the caller should check that shaderDerivativeSupport exists.
@@ -289,6 +291,7 @@ private:
     bool fAtan2ImplementedAsAtanYOverX : 1;
     bool fRequiresLocalOutputColorForFBFetch : 1;
     bool fMustImplementGSInvocationsWithLoop : 1;
+    bool fMustObfuscateUniformColor : 1;
 
     PrecisionInfo fFloatPrecisions[kGrShaderTypeCount][kGrSLPrecisionCount];