added basic dataflow analysis to skslc

src/gpu/effects/GrXfermodeFragmentProcessor.cpp

 /*
 * Copyright 2015 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
 #include "effects/GrXfermodeFragmentProcessor.h"
 
 #include "GrFragmentProcessor.h"
@@ skipping 80 matching lines @@
     GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
     const ComposeTwoFragmentProcessor& cs = args.fFp.cast<ComposeTwoFragmentProcessor>();
 
     const char* inputColor = nullptr;
     if (args.fInputColor) {
         inputColor = "inputColor";
         fragBuilder->codeAppendf("vec4 inputColor = vec4(%s.rgb, 1.0);", args.fInputColor);
     }
 
     // declare outputColor and emit the code for each of the two children
-    SkString srcColor("src");
+    SkString srcColor("xfer_src");
     this->emitChild(0, inputColor, &srcColor, args);
 
-    SkString dstColor("dst");
+    SkString dstColor("xfer_dst");
     this->emitChild(1, inputColor, &dstColor, args);
 
     // emit blend code
     SkXfermode::Mode mode = cs.getMode();
     fragBuilder->codeAppendf("// Compose Xfer Mode: %s\n", SkXfermode::ModeName(mode));
     GrGLSLBlend::AppendMode(fragBuilder,
                             srcColor.c_str(),
                             dstColor.c_str(),
                             args.fOutputColor,
                             mode);
@@ skipping 188 matching lines @@
             return GrConstColorProcessor::Make(GrColor_TRANSPARENT_BLACK,
                                                  GrConstColorProcessor::kIgnore_InputMode);
         case SkXfermode::kDst_Mode:
             return nullptr;
         default:
             return sk_sp<GrFragmentProcessor>(
                 new ComposeOneFragmentProcessor(src, mode,
                                                 ComposeOneFragmentProcessor::kSrc_Child));
     }
 }