Revert "Added SkSL workaround for devices which cannot safely access gl_FragCoord"

This reverts commit 1001f843a45e95f6df1d44242b6b06c77898e870.

Reason for revert: Many failures.

Original change's description:
> Added SkSL workaround for devices which cannot safely access gl_FragCoord
> 
> This is the root cause of https://github.com/flutter/flutter/issues/13216
> I've got a GM that demonstrates the bug, but only in Viewer.
> 
> Bug: skia:7410
> Change-Id: Iaa1f27b10166aa09e4dc5949e5a6ca1bd14c99ac
> Reviewed-on: https://skia-review.googlesource.com/93920
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Brian Osman <brianosman@google.com>

TBR=bsalomon@google.com,brianosman@google.com,ethannicholas@google.com

Change-Id: I2a2edc0a8fa11fe9dac1045dc79ae91106518b02
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:7410
Reviewed-on: https://skia-review.googlesource.com/94281
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

6 files changed, 2 insertions, 100 deletions

diff --git a/include/gpu/GrShaderCaps.h b/include/gpu/GrShaderCaps.h
index 66e7d42306..b56694c7dc 100644
--- a/include/gpu/GrShaderCaps.h
+++ b/include/gpu/GrShaderCaps.h
@@ -121,9 +121,6 @@ public:
     // the shader.
     bool mustDoOpBetweenFloorAndAbs() const { return fMustDoOpBetweenFloorAndAbs; }
 
-    // If false, SkSL uses a workaround so that sk_FragCoord doesn't actually query gl_FragCoord
-    bool canUseFragCoord() const { return fCanUseFragCoord; }
-
     bool requiresLocalOutputColorForFBFetch() const { return fRequiresLocalOutputColorForFBFetch; }
 
     bool mustObfuscateUniformColor() const { return fMustObfuscateUniformColor; }
@@ -278,7 +275,6 @@ private:
     bool fRequiresLocalOutputColorForFBFetch : 1;
     bool fMustObfuscateUniformColor : 1;
     bool fMustGuardDivisionEvenAfterExplicitZeroCheck : 1;
-    bool fCanUseFragCoord : 1;
 
     const char* fVersionDeclString;
 
diff --git a/src/gpu/GrShaderCaps.cpp b/src/gpu/GrShaderCaps.cpp
index 2ab19478af..2041ada635 100644
--- a/src/gpu/GrShaderCaps.cpp
+++ b/src/gpu/GrShaderCaps.cpp
@@ -38,7 +38,6 @@ GrShaderCaps::GrShaderCaps(const GrContextOptions& options) {
     fRequiresLocalOutputColorForFBFetch = false;
     fMustObfuscateUniformColor = false;
     fMustGuardDivisionEvenAfterExplicitZeroCheck = false;
-    fCanUseFragCoord = true;
     fFlatInterpolationSupport = false;
     fPreferFlatInterpolation = false;
     fNoPerspectiveInterpolationSupport = false;
@@ -114,7 +113,6 @@ void GrShaderCaps::dumpJSON(SkJSONWriter* writer) const {
     writer->appendBool("Must obfuscate uniform color", fMustObfuscateUniformColor);
     writer->appendBool("Must guard division even after explicit zero check",
                        fMustGuardDivisionEvenAfterExplicitZeroCheck);
-    writer->appendBool("Can use gl_FragCoord", fCanUseFragCoord);
     writer->appendBool("Flat interpolation support", fFlatInterpolationSupport);
     writer->appendBool("Prefer flat interpolation", fPreferFlatInterpolation);
     writer->appendBool("No perspective interpolation support", fNoPerspectiveInterpolationSupport);
diff --git a/src/gpu/gl/GrGLCaps.cpp b/src/gpu/gl/GrGLCaps.cpp
index d310cd219b..4996859c51 100644
--- a/src/gpu/gl/GrGLCaps.cpp
+++ b/src/gpu/gl/GrGLCaps.cpp
@@ -1048,12 +1048,6 @@ void GrGLCaps::initGLSL(const GrGLContextInfo& ctxInfo, const GrGLInterface* gli
         shaderCaps->fMustGuardDivisionEvenAfterExplicitZeroCheck = true;
     }
 #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 drviers.
-    if (kAdreno3xx_GrGLRenderer == ctxInfo.renderer()) {
-        shaderCaps->fCanUseFragCoord = false;
-    }
 }
 
 bool GrGLCaps::hasPathRenderingSupport(const GrGLContextInfo& ctxInfo, const GrGLInterface* gli) {
diff --git a/src/sksl/SkSLGLSLCodeGenerator.cpp b/src/sksl/SkSLGLSLCodeGenerator.cpp
index f3400c7f5a..9e2336e22e 100644
--- a/src/sksl/SkSLGLSLCodeGenerator.cpp
+++ b/src/sksl/SkSLGLSLCodeGenerator.cpp
@@ -597,12 +597,6 @@ void GLSLCodeGenerator::writeConstructor(const Constructor& c, Precedence parent
 }
 
 void GLSLCodeGenerator::writeFragCoord() {
-    if (!fProgram.fSettings.fCaps->canUseFragCoord()) {
-        this->write("vec4(sk_FragCoord_Workaround.xyz / sk_FragCoord_Workaround.w, "
-                    "1.0 / sk_FragCoord_Workaround.w)");
-        return;
-    }
-
     // We only declare "gl_FragCoord" when we're in the case where we want to use layout qualifiers
     // to reverse y. Otherwise it isn't necessary and whether the "in" qualifier appears in the
     // declaration varies in earlier GLSL specs. So it is simpler to omit it.
@@ -625,7 +619,7 @@ void GLSLCodeGenerator::writeFragCoord() {
             // 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
+            // do the same thing. Copying gl_FragCoord.xy into a temp float2beforehand
             // (and only accessing .xy) seems to "fix" things.
             const char* precision = usesPrecisionModifiers() ? "highp " : "";
             fHeader.writeText("uniform ");
@@ -646,6 +640,7 @@ void GLSLCodeGenerator::writeFragCoord() {
     }
 }
 
+
 void GLSLCodeGenerator::writeVariableReference(const VariableReference& ref) {
     switch (ref.fVariable.fModifiers.fLayout.fBuiltin) {
         case SK_FRAGCOLOR_BUILTIN:
@@ -685,10 +680,6 @@ void GLSLCodeGenerator::writeIndexExpression(const IndexExpression& expr) {
     this->write("]");
 }
 
-bool is_sk_position(const FieldAccess& f) {
-    return "sk_Position" == f.fBase->fType.fields()[f.fFieldIndex].fName;
-}
-
 void GLSLCodeGenerator::writeFieldAccess(const FieldAccess& f) {
     if (f.fOwnerKind == FieldAccess::kDefault_OwnerKind) {
         this->writeExpression(*f.fBase, kPostfix_Precedence);
@@ -764,22 +755,11 @@ void GLSLCodeGenerator::writeBinaryExpression(const BinaryExpression& b,
     if (precedence >= parentPrecedence) {
         this->write("(");
     }
-    bool positionWorkaround = Compiler::IsAssignment(b.fOperator) &&
-                              Expression::kFieldAccess_Kind == b.fLeft->fKind &&
-                              is_sk_position((FieldAccess&) *b.fLeft) &&
-                              !strstr(b.fRight->description().c_str(), "sk_RTAdjust") &&
-                              !fProgram.fSettings.fCaps->canUseFragCoord();
-    if (positionWorkaround) {
-        this->write("sk_FragCoord_Workaround = (");
-    }
     this->writeExpression(*b.fLeft, precedence);
     this->write(" ");
     this->write(Compiler::OperatorName(b.fOperator));
     this->write(" ");
     this->writeExpression(*b.fRight, precedence);
-    if (positionWorkaround) {
-        this->write(")");
-    }
     if (precedence >= parentPrecedence) {
         this->write(")");
     }
@@ -1208,25 +1188,6 @@ void GLSLCodeGenerator::writeHeader() {
             this->writeExtension((Extension&) *e);
         }
     }
-    if (!fProgram.fSettings.fCaps->canUseFragCoord()) {
-        Layout layout;
-        switch (fProgram.fKind) {
-            case Program::kVertex_Kind: {
-                Modifiers modifiers(layout, Modifiers::kOut_Flag | Modifiers::kHighp_Flag);
-                this->writeModifiers(modifiers, true);
-                this->write("vec4 sk_FragCoord_Workaround;\n");
-                break;
-            }
-            case Program::kFragment_Kind: {
-                Modifiers modifiers(layout, Modifiers::kIn_Flag | Modifiers::kHighp_Flag);
-                this->writeModifiers(modifiers, true);
-                this->write("vec4 sk_FragCoord_Workaround;\n");
-                break;
-            }
-            default:
-                break;
-        }
-    }
 }
 
 void GLSLCodeGenerator::writeProgramElement(const ProgramElement& e) {
diff --git a/src/sksl/SkSLUtil.h b/src/sksl/SkSLUtil.h
index 787698f2c6..7a39386269 100644
--- a/src/sksl/SkSLUtil.h
+++ b/src/sksl/SkSLUtil.h
@@ -174,10 +174,6 @@ public:
     bool canUseFractForNegativeValues() const {
         return true;
     }
-
-    bool canUseFragCoord() const {
-        return true;
-    }
 };
 
 extern StandaloneShaderCaps standaloneCaps;
@@ -304,13 +300,6 @@ public:
         result->fCanUseAnyFunctionInShader = false;
         return result;
     }
-
-    static sk_sp<GrShaderCaps> CannotUseFragCoord() {
-        sk_sp<GrShaderCaps> result = sk_make_sp<GrShaderCaps>(GrContextOptions());
-        result->fVersionDeclString = "#version 400";
-        result->fCanUseFragCoord = false;
-        return result;
-    }
 };
 #endif
 
diff --git a/tests/SkSLGLSLTest.cpp b/tests/SkSLGLSLTest.cpp
index 9b0571bcdc..1ae421f8af 100644
--- a/tests/SkSLGLSLTest.cpp
+++ b/tests/SkSLGLSLTest.cpp
@@ -1059,42 +1059,6 @@ DEF_TEST(SkSLFragCoord, r) {
          "}\n",
          &inputs);
     REPORTER_ASSERT(r, !inputs.fRTHeight);
-
-    test(r,
-         "in float4 pos; void main() { sk_Position = pos; }",
-         *SkSL::ShaderCapsFactory::CannotUseFragCoord(),
-         "#version 400\n"
-         "out vec4 sk_FragCoord_Workaround;\n"
-         "in vec4 pos;\n"
-         "void main() {\n"
-         "    sk_FragCoord_Workaround = (gl_Position = pos);\n"
-         "}\n",
-         SkSL::Program::kVertex_Kind);
-
-    test(r,
-         "in uniform float4 sk_RTAdjust; in float4 pos; void main() { sk_Position = pos; }",
-         *SkSL::ShaderCapsFactory::CannotUseFragCoord(),
-         "#version 400\n"
-         "out vec4 sk_FragCoord_Workaround;\n"
-         "in uniform vec4 sk_RTAdjust;\n"
-         "in vec4 pos;\n"
-         "void main() {\n"
-         "    sk_FragCoord_Workaround = (gl_Position = pos);\n"
-         "    gl_Position = vec4(gl_Position.x * sk_RTAdjust.x + gl_Position.w * sk_RTAdjust.y, "
-              "gl_Position.y * sk_RTAdjust.z + gl_Position.w * sk_RTAdjust.w, 0, gl_Position.w);\n"
-         "}\n",
-         SkSL::Program::kVertex_Kind);
-
-    test(r,
-         "void main() { sk_FragColor.xy = sk_FragCoord.xy; }",
-         *SkSL::ShaderCapsFactory::CannotUseFragCoord(),
-         "#version 400\n"
-         "in vec4 sk_FragCoord_Workaround;\n"
-         "out vec4 sk_FragColor;\n"
-         "void main() {\n"
-         "    sk_FragColor.xy = vec4(sk_FragCoord_Workaround.xyz / sk_FragCoord_Workaround.w, "
-             "1.0 / sk_FragCoord_Workaround.w).xy;\n"
-         "}\n");
 }
 
 DEF_TEST(SkSLVertexID, r) {