commit 9954bc38c498f6b9e9d8c0bcc5cd00d45bfc6e23
author cdalton <cdalton@nvidia.com> Wed Apr 29 14:17:00 2015 -0700
committer Commit bot <commit-bot@chromium.org> Wed Apr 29 14:17:00 2015 -0700
tree f88d88bad3884d979e595a6a462e21cf89b4bdc9
parent dbc3cefb0b624808ddb86d444e6103f216e12fa5

Use texture barriers to read directly from the RT

Updates GrXferProcessor to read directly from the RT texture when
texture barriers are supported and it needs to know the dst color.
Also adds the notion of an Xfer barrier and uses it to issue texture
barriers when the XP will read the RT.

BUG=skia:

Review URL: https://codereview.chromium.org/1040303002

src/gpu/GrDrawTarget.cpp

diff --git a/src/gpu/GrDrawTarget.cpp b/src/gpu/GrDrawTarget.cpp
index e52e4f9..d868bcb 100644
--- a/src/gpu/GrDrawTarget.cpp
+++ b/src/gpu/GrDrawTarget.cpp
@@ -78,8 +78,20 @@
     if (!pipelineBuilder.willXPNeedDstCopy(*this->caps(), colorPOI, coveragePOI)) {
         return true;
     }
-    SkIRect copyRect;
+
     GrRenderTarget* rt = pipelineBuilder.getRenderTarget();
+
+    if (this->caps()->textureBarrierSupport()) {
+        if (GrTexture* rtTex = rt->asTexture()) {
+            // The render target is a texture, se we can read from it directly in the shader. The XP
+            // will be responsible to detect this situation and request a texture barrier.
+            dstCopy->setTexture(rtTex);
+            dstCopy->setOffset(0, 0);
+            return true;
+        }
+    }
+
+    SkIRect copyRect;
     pipelineBuilder.clip().getConservativeBounds(rt, &copyRect);
 
     if (drawBounds) {