add Start/EndFragmentProcessor to DSLWriter

Change-Id: I6f9d414d55b3ba64c3f67f3a590f6b7b5642062a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/364599
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>

gn/sksl.gni

@@ -74,6 +74,8 @@ skia_sksl_sources = [
   "$_src/sksl/dsl/DSLType.h",
   "$_src/sksl/dsl/DSLVar.cpp",
   "$_src/sksl/dsl/DSLVar.h",
+  "$_src/sksl/dsl/priv/DSLFPs.cpp",
+  "$_src/sksl/dsl/priv/DSLFPs.h",
   "$_src/sksl/dsl/priv/DSLWriter.cpp",
   "$_src/sksl/dsl/priv/DSLWriter.h",
   "$_src/sksl/ir/SkSLBinaryExpression.h",

src/sksl/dsl/priv/DSLFPs.cpp

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2021 Google LLC.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "src/sksl/dsl/priv/DSLFPs.h"
+
+#include "src/sksl/dsl/priv/DSLWriter.h"
+
+#if !defined(SKSL_STANDALONE) && SK_SUPPORT_GPU
+
+namespace SkSL {
+
+namespace dsl {
+
+void StartFragmentProcessor(GrGLSLFragmentProcessor* processor,
+                            GrGLSLFragmentProcessor::EmitArgs* emitArgs) {
+    DSLWriter::StartFragmentProcessor(processor, emitArgs);
+}
+
+void EndFragmentProcessor() {
+    DSLWriter::EndFragmentProcessor();
+}
+
+} // namespace dsl
+
+} // namespace SkSL
+
+#endif // !defined(SKSL_STANDALONE) && SK_SUPPORT_GPU

src/sksl/dsl/priv/DSLFPs.h

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2021 Google LLC.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SKSL_DSL_FPS
+#define SKSL_DSL_FPS
+
+#include "src/sksl/dsl/DSL.h"
+
+#if !defined(SKSL_STANDALONE) && SK_SUPPORT_GPU
+
+#include "src/gpu/glsl/GrGLSLFragmentProcessor.h"
+
+namespace SkSL {
+
+namespace dsl {
+
+void StartFragmentProcessor(GrGLSLFragmentProcessor* processor,
+                            GrGLSLFragmentProcessor::EmitArgs* emitArgs);
+
+void EndFragmentProcessor();
+
+} // namespace dsl
+
+} // namespace SkSL
+
+#endif // !defined(SKSL_STANDALONE) && SK_SUPPORT_GPU
+
+#endif

src/sksl/dsl/priv/DSLWriter.cpp

@@ -11,6 +11,7 @@
 #include "src/gpu/mock/GrMockCaps.h"
 #endif // !defined(SKSL_STANDALONE) && SK_SUPPORT_GPU
 #include "src/sksl/SkSLCompiler.h"
+#include "src/sksl/SkSLDefines.h"
 #include "src/sksl/SkSLIRGenerator.h"
 #include "src/sksl/dsl/DSLCore.h"
 
@@ -65,6 +66,21 @@ void DSLWriter::SetCurrentFunction(const SkSL::FunctionDeclaration* fn) {
     IRGenerator().fCurrentFunction = fn;
 }
 
+#if !defined(SKSL_STANDALONE) && SK_SUPPORT_GPU
+void DSLWriter::StartFragmentProcessor(GrGLSLFragmentProcessor* processor,
+                                       GrGLSLFragmentProcessor::EmitArgs* emitArgs) {
+    Instance().fStack.push({processor, emitArgs});
+    IRGenerator().pushSymbolTable();
+}
+
+void DSLWriter::EndFragmentProcessor() {
+    DSLWriter& instance = Instance();
+    SkASSERT(!instance.fStack.empty());
+    instance.fStack.pop();
+    IRGenerator().popSymbolTable();
+}
+#endif // !defined(SKSL_STANDALONE) && SK_SUPPORT_GPU
+
 std::unique_ptr<SkSL::Expression> DSLWriter::Check(std::unique_ptr<SkSL::Expression> expr) {
     if (expr == nullptr) {
         if (DSLWriter::Compiler().errorCount()) {

src/sksl/dsl/priv/DSLWriter.h

@@ -97,6 +97,36 @@ public:
      */
     static void SetCurrentFunction(const SkSL::FunctionDeclaration* fn);
 
+#if !defined(SKSL_STANDALONE) && SK_SUPPORT_GPU
+    /**
+     * Returns the fragment processor for which DSL output is being generated for the current
+     * thread.
+     */
+    static GrGLSLFragmentProcessor* CurrentProcessor() {
+        SkASSERTF(!Instance().fStack.empty(), "This feature requires a FragmentProcessor");
+        return Instance().fStack.top().fProcessor;
+    }
+
+    /**
+     * Returns the EmitArgs for fragment processor output in the current thread.
+     */
+    static GrGLSLFragmentProcessor::EmitArgs* CurrentEmitArgs() {
+        SkASSERTF(!Instance().fStack.empty(), "This feature requires a FragmentProcessor");
+        return Instance().fStack.top().fEmitArgs;
+    }
+
+    /**
+     * Pushes a new processor / emitArgs pair for the current thread.
+     */
+    static void StartFragmentProcessor(GrGLSLFragmentProcessor* processor,
+                                       GrGLSLFragmentProcessor::EmitArgs* emitArgs);
+
+    /**
+     * Pops the processor / emitArgs pair associated with the current thread.
+     */
+    static void EndFragmentProcessor();
+#endif // !defined(SKSL_STANDALONE) && SK_SUPPORT_GPU
+
     /**
      * Reports an error if the argument is null. Returns its argument unmodified.
      */
@@ -149,6 +179,13 @@ private:
     ErrorHandler* fErrorHandler = nullptr;
     bool fMangle = true;
     Mangler fMangler;
+#if !defined(SKSL_STANDALONE) && SK_SUPPORT_GPU
+    struct StackFrame {
+        GrGLSLFragmentProcessor* fProcessor;
+        GrGLSLFragmentProcessor::EmitArgs* fEmitArgs;
+    };
+    std::stack<StackFrame> fStack;
+#endif // !defined(SKSL_STANDALONE) && SK_SUPPORT_GPU
 
     friend class DSLCore;
     friend class ::AutoDSLContext;