commit 5e1f6ea595633e2c9abf1c40646dc53394c27498
author Michael Ludwig <michaelludwig@google.com> Mon Dec 03 15:14:50 2018 -0500
committer Skia Commit-Bot <skia-commit-bot@chromium.org> Mon Dec 03 21:32:11 2018 +0000
tree 04789b9a582285a136655c399e3d06861fd0b6f0
parent f8dfe4cbbfef01c7244df0686f2fb8fd642abb96

Remove unnecessary gl_FragCoord workaround

Bug: skia:
Change-Id: I04b6cbfe083c32a25205e04a4b15672d4b678a9c
Reviewed-on: https://skia-review.googlesource.com/c/174063
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>

src/gpu/gl/GrGLCaps.cpp

diff --git a/src/gpu/gl/GrGLCaps.cpp b/src/gpu/gl/GrGLCaps.cpp
index de239fc..1f2d8f3 100644
--- a/src/gpu/gl/GrGLCaps.cpp
+++ b/src/gpu/gl/GrGLCaps.cpp
@@ -2604,7 +2604,9 @@
 #endif
 
     // We've seen Adreno 3xx devices produce incorrect (flipped) values for gl_FragCoord, in some
-    // (rare) situations. It's sporadic, and mostly on older drivers.
+    // (rare) situations. It's sporadic, and mostly on older drivers. Additionally, old Adreno
+    // compilers (see crbug.com/skia/4078) crash when accessing .zw of gl_FragCoord, so just bypass
+    // using gl_FragCoord at all to get around it.
     if (kAdreno3xx_GrGLRenderer == ctxInfo.renderer()) {
         shaderCaps->fCanUseFragCoord = false;
     }

src/sksl/SkSLGLSLCodeGenerator.cpp

diff --git a/src/sksl/SkSLGLSLCodeGenerator.cpp b/src/sksl/SkSLGLSLCodeGenerator.cpp
index 26bda18..c231626 100644
--- a/src/sksl/SkSLGLSLCodeGenerator.cpp
+++ b/src/sksl/SkSLGLSLCodeGenerator.cpp
@@ -756,17 +756,9 @@
         this->write("gl_FragCoord");
     } else {
         if (!fSetupFragPositionLocal) {
-            // The Adreno compiler seems to be very touchy about access to "gl_FragCoord".
-            // Accessing glFragCoord.zw can cause a program to fail to link. Additionally,
-            // depending on the surrounding code, accessing .xy with a uniform involved can
-            // do the same thing. Copying gl_FragCoord.xy into a temp float2 beforehand
-            // (and only accessing .xy) seems to "fix" things.
-            const char* precision = usesPrecisionModifiers() ? "highp " : "";
-            fFunctionHeader += precision;
-            fFunctionHeader += "    vec2 _sktmpCoord = gl_FragCoord.xy;\n";
-            fFunctionHeader += precision;
-            fFunctionHeader += "    vec4 sk_FragCoord = vec4(_sktmpCoord.x, " SKSL_RTHEIGHT_NAME
-                               " - _sktmpCoord.y, 1.0, 1.0);\n";
+            fFunctionHeader += usesPrecisionModifiers() ? "highp " : "";
+            fFunctionHeader += "    vec4 sk_FragCoord = vec4(gl_FragCoord.x, " SKSL_RTHEIGHT_NAME
+                               " - gl_FragCoord.y, gl_FragCoord.z, gl_FragCoord.w);\n";
             fSetupFragPositionLocal = true;
         }
         this->write("sk_FragCoord");

tests/SkSLGLSLTest.cpp

diff --git a/tests/SkSLGLSLTest.cpp b/tests/SkSLGLSLTest.cpp
index a9f1abe..8d12dcc 100644
--- a/tests/SkSLGLSLTest.cpp
+++ b/tests/SkSLGLSLTest.cpp
@@ -1147,8 +1147,8 @@
          "uniform float u_skRTHeight;\n"
          "out vec4 sk_FragColor;\n"
          "void main() {\n"
-         "    vec2 _sktmpCoord = gl_FragCoord.xy;\n"
-         "    vec4 sk_FragCoord = vec4(_sktmpCoord.x, u_skRTHeight - _sktmpCoord.y, 1.0, 1.0);\n"
+         "    vec4 sk_FragCoord = vec4(gl_FragCoord.x, u_skRTHeight - gl_FragCoord.y, "
+                 "gl_FragCoord.z, gl_FragCoord.w);\n"
          "    sk_FragColor.xy = sk_FragCoord.xy;\n"
          "}\n",
          &inputs);