Add GrProcOptInfo class to track various output information for color and coverage stages.

src/gpu/GrProcOptInfo.h

Index: src/gpu/GrProcOptInfo.h
diff --git a/src/gpu/GrProcOptInfo.h b/src/gpu/GrProcOptInfo.h
new file mode 100644
index 0000000000000000000000000000000000000000..138b7da11ce2b1a0c86fbffd63e0fd8f67435760
--- /dev/null
+++ b/src/gpu/GrProcOptInfo.h
@@ -0,0 +1,87 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrProcOptInfo_DEFINED
+#define GrProcOptInfo_DEFINED
+
+#include "GrColor.h"
+#include "GrInvariantOutput.h"
+
+class GrFragmentStage;
+class GrGeometryProcessor;
+
+class GrProcOptInfo {

[bsalomon, 2014/11/13 15:09:19]

GrProcOptInfo is gathers invariant data from a set of processor stages. It is
used to recognize optimizations related to eliminating stages and vertex
attributes that aren't necessary for a draw.

[egdaniel, 2014/11/13 18:34:16]

Done.

+public:
+    GrProcOptInfo()
+        : fInOut(0, static_cast<GrColorComponentFlags>(0), false),
+          fFirstEffectStageIndex(0),

[bsalomon, 2014/11/13 15:09:19]

style is to 

: fPut()
, fThe()
, fCommas()
, fUnder()
, fTheColon() {
}

[egdaniel, 2014/11/13 18:34:16]

Ahh I understand my error, just like TheColon I should merge my last two data
members into a single variable. Thanks for the advice!

+          fInputColorIsUsed(true),
+          fInputColor(0),
+          fRemoveVertexAttrib(false),
+          fReadsDst(false) {}
+
+    void calcWithInitialValues(const GrFragmentStage*, int stageCount, GrColor startColor,
+                               GrColorComponentFlags flags, bool areCoverageStages,
+                               const GrGeometryProcessor* gp = NULL);
+
+    bool isSolidWhite() const { return fInOut.isSolidWhite(); }
+    bool isOpaque() const { return fInOut.isOpaque(); }
+
+    GrColor color() const { return fInOut.color(); }
+    uint8_t validFlags() const { return fInOut.validFlags(); }
+
+    /**
+     * Returns the index of the first effective color stage. If an intermediate stage doesn't read
+     * its input or has a known output, then we can ignore all earlier stages since they will not
+     * affect the final output. Thus the first effective stage index is the index to the first stage
+     * that will have an effect on the final output.
+     *
+     * If the firstEffectiveStageIndex is used, corresponding values from inputColorIsUsed(),

[bsalomon, 2014/11/13 15:09:19]

"If stages before the first effective stage are removed,"
?

[egdaniel, 2014/11/13 18:34:16]

Done.

+     * inputColorToEffectiveStage(), removeVertexAttribs(), and readsDst() must be used when setting
+     * up the draw to ensure correct drawing.
+     */
+    int firstEffectiveStageIndex() const { return fFirstEffectStageIndex; }
+
+    /**
+     * This value returns whether or not an input will be read by the starting stage. The starting

[bsalomon, 2014/11/13 15:09:19]

Maybe simplify to "True if the first effective stage reads its input, false
otherwise."?

[egdaniel, 2014/11/13 18:34:16]

Done.

+     * stage is assumed to be that which is indexed by firstEffectiveStageIndex().
+     */
+    bool inputColorIsUsed() const { return fInputColorIsUsed; }
+
+    /**
+     * This returns the color that should be inputed into the starting stage. This value is only

[bsalomon, 2014/11/13 15:09:19]

"If input color is used and per-vertex colors are not used, this is the input
color to the first effective stage"
?

Sorry for nit picking these comments, but its confusing stuff and making this
concise and clear may help us later.

[egdaniel, 2014/11/13 18:34:16]

Done.

+     * valid if inputColorIsUsed is true and we are not using vertex attribs for color/coverage
+     * input. The starting stage is assumed to be that which is indexed by
+     * firstEffectiveStageIndex().
+     */
+    GrColor inputColorToEffectiveStage() const { return fInputColor; }
+
+    /**
+     * Returns whether or not the client should remove corresponding color/coverage vertex attribs
+     * for the given set of stages. If we remove stages because of a known output at some
+     * intermediate stage, then we want to feed that known output into the start of its following
+     * stage. Thus we want to make sure we don't use color/coverage vertex attribs for this reduced
+     * set of stages.
+     */

[bsalomon, 2014/11/13 15:09:19]

"Given the set of optimizations determined by GrProcOptInfo, should the caller
remove a the color/coverage vertex attribute that was input to the first stage."

?

[egdaniel, 2014/11/13 18:34:16]

Done.

+    bool removeVertexAttrib() const { return fRemoveVertexAttrib; }
+
+    /**
+     * Returns whether or not any of the stages, begining with start stage, will read the dst. The
+     * start stage is determined by firstEffectiveStageIndex()
+     */
+    bool readsDst() const { return fReadsDst; }

[bsalomon, 2014/11/13 15:09:19]

"Returns true if any of the stages preserved by GrProcOptInfo read the dst
color."

?

[egdaniel, 2014/11/13 18:34:16]

Done.

+
+private:
+    GrInvariantOutput fInOut;
+    int fFirstEffectStageIndex;
+    bool fInputColorIsUsed;
+    GrColor fInputColor;
+    bool fRemoveVertexAttrib;
+    bool fReadsDst;
+};
+
+#endif