Revert "Revert "Make SkSL GLSL generator declare sk_FragColor inout when EXT fb fetch is used.""

This reverts commit d40133092ae138b3d47a1158101faec3c53c6b1f.

Bug: skia:
Change-Id: I236505da047d5ad29e4952d8955eb7aa1bfb870b
Reviewed-on: https://skia-review.googlesource.com/118621
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>

4 files changed, 10 insertions, 1 deletions

diff --git a/src/sksl/SkSLGLSLCodeGenerator.cpp b/src/sksl/SkSLGLSLCodeGenerator.cpp
index 996714ec62..43c1c95327 100644
--- a/src/sksl/SkSLGLSLCodeGenerator.cpp
+++ b/src/sksl/SkSLGLSLCodeGenerator.cpp
@@ -1270,7 +1270,11 @@ void GLSLCodeGenerator::writeProgramElement(const ProgramElement& e) {
                     this->writeLine();
                 } else if (builtin == SK_FRAGCOLOR_BUILTIN &&
                            fProgram.fSettings.fCaps->mustDeclareFragmentShaderOutput()) {
-                    this->write("out ");
+                    if (fProgram.fSettings.fFragColorIsInOut) {
+                        this->write("inout ");
+                    } else {
+                        this->write("out ");
+                    }
                     if (usesPrecisionModifiers()) {
                         this->write("mediump ");
                     }
diff --git a/src/sksl/SkSLMetalCodeGenerator.cpp b/src/sksl/SkSLMetalCodeGenerator.cpp
index de6b1d0854..a8301c2eb4 100644
--- a/src/sksl/SkSLMetalCodeGenerator.cpp
+++ b/src/sksl/SkSLMetalCodeGenerator.cpp
@@ -451,6 +451,8 @@ void MetalCodeGenerator::writeFunction(const FunctionDefinition& f) {
     }
     this->writeLine(") {");
 
+    ASSERT(!fProgram.fSettings.fFragColorIsInOut);
+
     if ("main" == f.fDeclaration.fName) {
         switch (fProgram.fKind) {
             case Program::kFragment_Kind:
diff --git a/src/sksl/SkSLSPIRVCodeGenerator.cpp b/src/sksl/SkSLSPIRVCodeGenerator.cpp
index dadab91753..5f312afef1 100644
--- a/src/sksl/SkSLSPIRVCodeGenerator.cpp
+++ b/src/sksl/SkSLSPIRVCodeGenerator.cpp
@@ -2545,6 +2545,7 @@ void SPIRVCodeGenerator::writeGlobalVars(Program::Kind kind, const VarDeclaratio
         }
         if (var->fModifiers.fLayout.fBuiltin == SK_FRAGCOLOR_BUILTIN &&
             kind != Program::kFragment_Kind) {
+            ASSERT(!fProgram.fSettings.fFragColorIsInOut);
             continue;
         }
         if (!var->fReadCount && !var->fWriteCount &&
diff --git a/src/sksl/ir/SkSLProgram.h b/src/sksl/ir/SkSLProgram.h
index cbb9dfe1a7..03a94fa03f 100644
--- a/src/sksl/ir/SkSLProgram.h
+++ b/src/sksl/ir/SkSLProgram.h
@@ -71,6 +71,8 @@ struct Program {
         // if false, sk_FragCoord is exactly the same as gl_FragCoord. If true, the y coordinate
         // must be flipped.
         bool fFlipY = false;
+        // If true the destination fragment color is read sk_FragColor. It must be declared inout.
+        bool fFragColorIsInOut = false;
         // if true, Setting objects (e.g. sk_Caps.fbFetchSupport) should be replaced with their
         // constant equivalents during compilation
         bool fReplaceSettings = true;