Replace fWillReadFragmentPosition with a bitfield

src/gpu/GrProcOptInfo.cpp

Index: src/gpu/GrProcOptInfo.cpp
diff --git a/src/gpu/GrProcOptInfo.cpp b/src/gpu/GrProcOptInfo.cpp
index bfd9e9ec8ceabd638a3e50179bdfe1aff9216348..4410d7136c710caf7039d9ac017b6beef114f786 100644
--- a/src/gpu/GrProcOptInfo.cpp
+++ b/src/gpu/GrProcOptInfo.cpp
@@ -23,7 +23,7 @@ void GrProcOptInfo::calcWithInitialValues(const GrFragmentProcessor * const proc
     out.fValidFlags = flags;
     out.fIsLCDCoverage = isLCD;
     fInOut.reset(out);
-    this->internalCalc(processors, cnt, false);
+    this->internalCalc(processors, cnt);
 }
 
 void GrProcOptInfo::initUsingInvariantOutput(GrInitInvariantOutput invOutput) {
@@ -31,16 +31,14 @@ void GrProcOptInfo::initUsingInvariantOutput(GrInitInvariantOutput invOutput) {
 }
 
 void GrProcOptInfo::completeCalculations(const GrFragmentProcessor * const processors[], int cnt) {
-    this->internalCalc(processors, cnt, false);
+    this->internalCalc(processors, cnt);
 }
 
-void GrProcOptInfo::internalCalc(const GrFragmentProcessor* const processors[],
-                                 int cnt,
-                                 bool initWillReadFragmentPosition) {
+void GrProcOptInfo::internalCalc(const GrFragmentProcessor* const processors[], int cnt) {
     fFirstEffectiveProcessorIndex = 0;
     fInputColorIsUsed = true;
     fInputColor = fInOut.color();
-    fReadsFragPosition = initWillReadFragmentPosition;
+    fBuiltInState = GrProcessor::kNone_BuiltInState;
 
     for (int i = 0; i < cnt; ++i) {
         const GrFragmentProcessor* processor = processors[i];
@@ -50,12 +48,10 @@ void GrProcOptInfo::internalCalc(const GrFragmentProcessor* const processors[],
         if (!fInOut.willUseInputColor()) {
             fFirstEffectiveProcessorIndex = i;
             fInputColorIsUsed = false;
-            // Reset these since we don't care if previous stages read these values
-            fReadsFragPosition = initWillReadFragmentPosition;
-        }
-        if (processor->willReadFragmentPosition()) {
-            fReadsFragPosition = true;
+            // Reset these since we will be removing any previous stages that read these values.
+            fBuiltInState = GrProcessor::kNone_BuiltInState;
         }
+        fBuiltInState |= processor->builtInState();
         if (kRGBA_GrColorComponentFlags == fInOut.validFlags()) {
             fFirstEffectiveProcessorIndex = i + 1;
             fInputColor = fInOut.color();
@@ -63,8 +59,8 @@ void GrProcOptInfo::internalCalc(const GrFragmentProcessor* const processors[],
             // Since we are clearing all previous color stages we are in a state where we have found
             // zero stages that don't multiply the inputColor.
             fInOut.resetNonMulStageFound();
-            // Reset these since we don't care if previous stages read these values
-            fReadsFragPosition = initWillReadFragmentPosition;
+            // Reset these since we will be removing all processors.
+            fBuiltInState = GrProcessor::kNone_BuiltInState;

[Chris Dalton, 2016/02/25 19:19:03]

FYI, this is bad news for a processor that modifies the sample mask. We will
need to come up with some way for these sample mask processors to indicate that
they have side effects and can't be removed.

[joshualitt, 2016/02/25 20:50:27]

Yea, we don't actually remove processors from the coverage side of the pipeline,
so I think this isn't an issue, but it does seem fragile.

[bsalomon, 2016/02/25 21:11:03]

Yeah, querying willModifySampleMask could be the indicator.

         }
     }
 }