Calculate stage stats in GrOptDrawState

src/gpu/GrOptDrawState.cpp

Index: src/gpu/GrOptDrawState.cpp
diff --git a/src/gpu/GrOptDrawState.cpp b/src/gpu/GrOptDrawState.cpp
index 5f352966b8a3441d5faf603c6234788dc2e23db6..40a9509201e4b60a11bc9cdb5cf79bc508e1738e 100644
--- a/src/gpu/GrOptDrawState.cpp
+++ b/src/gpu/GrOptDrawState.cpp
@@ -44,6 +44,7 @@ GrOptDrawState::GrOptDrawState(const GrDrawState& drawState,
     this->copyEffectiveColorStages(drawState);
     this->copyEffectiveCoverageStages(drawState);
     this->adjustFromBlendOpts();
+    this->getStageStats();
 };
 
 void GrOptDrawState::adjustFromBlendOpts() {
@@ -179,6 +180,44 @@ void GrOptDrawState::copyEffectiveCoverageStages(const GrDrawState& ds) {
     }
 }
 
+static void get_stage_stats(const GrEffectStage& stage, bool* readsDst,
+                            bool* readsFragPosition, bool* requiresVertexShader) {
+    if (stage.getEffect()->willReadDstColor()) {
+        *readsDst = true;
+    }
+    if (stage.getEffect()->willReadFragmentPosition()) {
+        *readsFragPosition = true;
+    }
+    if (stage.getEffect()->requiresVertexShader()) {
+        *requiresVertexShader = true;
+    }
+}
+void GrOptDrawState::getStageStats() {
+    fReadsDst = false;
+    fReadsFragPosition = false;
+    fRequiresVertexShader = false;
+
+    for (int s = 0; s < this->numColorStages(); ++s) {
+        const GrEffectStage& stage = this->getColorStage(s);
+        get_stage_stats(stage, &fReadsDst, &fReadsFragPosition, &fRequiresVertexShader);
+    }
+    for (int s = 0; s < this->numCoverageStages(); ++s) {
+        const GrEffectStage& stage = this->getCoverageStage(s);
+        get_stage_stats(stage, &fReadsDst, &fReadsFragPosition, &fRequiresVertexShader);
+    }
+    // TODO: Once non Geom Processors can't be vertex effects we can remove this assert
+    SkASSERT(!fRequiresVertexShader);
+    if (this->hasGeometryProcessor()) {
+        const GrEffectStage& stage = *this->getGeometryProcessor();
+        get_stage_stats(stage, &fReadsDst, &fReadsFragPosition, &fRequiresVertexShader);
+        SkASSERT(fRequiresVertexShader);
+    }
+    // TODO: Once we have actually separate GP's from other effects we can just set
+    // fRequiresVertexShader to be hasGeometryProcessor (or actaully just drop the bool all
+    // together and just check for GP when needed.
+    SkASSERT(this->hasGeometryProcessor() == fRequiresVertexShader);
+}
+
 bool GrOptDrawState::operator== (const GrOptDrawState& that) const {
     return this->isEqual(that);
 }