have shaders that need seed_shader call it themselves

This ought to make compose shader and our sprite blitter a bit more
efficient.  Compose shader can simply re-seed instead of saving the
xy values off to a buffer.  The sprite blitter doesn't need xy at all.

Change-Id: Ib4b3509288810f74a4c8e2978ce2ca14d8644980
Reviewed-on: https://skia-review.googlesource.com/18405
Reviewed-by: Herb Derby <herb@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>

3 files changed, 4 insertions, 7 deletions

diff --git a/src/shaders/SkComposeShader.cpp b/src/shaders/SkComposeShader.cpp
index 7735494291..be2388f4ec 100644
--- a/src/shaders/SkComposeShader.cpp
+++ b/src/shaders/SkComposeShader.cpp
@@ -128,24 +128,18 @@ bool SkComposeShader::onAppendStages(SkRasterPipeline* pipeline, SkColorSpace* d
                                      SkArenaAlloc* alloc, const SkMatrix& ctm,
                                      const SkPaint& paint, const SkMatrix* localM) const {
     struct Storage {
-        float   fXY[4 * SkJumper_kMaxStride];
         float   fRGBA[4 * SkJumper_kMaxStride];
         float   fAlpha;
     };
     auto storage = alloc->make<Storage>();
 
-    // We need to save off device x,y (inputs to shader), since after calling fShaderA they
-    // will be smashed, and I'll need them again for fShaderB. store_rgba saves off 4 registers
-    // even though we only need to save r,g.
-    pipeline->append(SkRasterPipeline::store_rgba, storage->fXY);
     if (!as_SB(fShaderB)->appendStages(pipeline, dstCS, alloc, ctm, paint, localM)) { // SRC
         return false;
     }
     // This outputs r,g,b,a, which we'll need later when we apply the mode, but we save it off now
     // since fShaderB will overwrite them.
     pipeline->append(SkRasterPipeline::store_rgba, storage->fRGBA);
-    // Now we restore the device x,y for the next shader
-    pipeline->append(SkRasterPipeline::load_rgba, storage->fXY);
+
     if (!as_SB(fShaderA)->appendStages(pipeline, dstCS, alloc, ctm, paint, localM)) {  // DST
         return false;
     }
diff --git a/src/shaders/SkImageShader.cpp b/src/shaders/SkImageShader.cpp
index d46d2558e8..bdbd382638 100644
--- a/src/shaders/SkImageShader.cpp
+++ b/src/shaders/SkImageShader.cpp
@@ -258,6 +258,7 @@ bool SkImageShader::onAppendStages(SkRasterPipeline* p, SkColorSpace* dstCS, SkA
         }
     }
 
+    p->append(SkRasterPipeline::seed_shader);
 
     struct MiscCtx {
         std::unique_ptr<SkBitmapController::State> state;
diff --git a/src/shaders/gradients/SkGradientShader.cpp b/src/shaders/gradients/SkGradientShader.cpp
index 137da84d0c..d98c8c6c7e 100644
--- a/src/shaders/gradients/SkGradientShader.cpp
+++ b/src/shaders/gradients/SkGradientShader.cpp
@@ -422,6 +422,8 @@ bool SkGradientShaderBase::onAppendStages(SkRasterPipeline* p,
         return false;
     }
 
+    p->append(SkRasterPipeline::seed_shader);
+
     auto* m = alloc->makeArrayDefault<float>(9);
     if (matrix.asAffine(m)) {
         p->append(SkRasterPipeline::matrix_2x3, m);