Move symbol-table push/pop methods out of IRGenerator.

This will allow us to use AutoSymbolTable in more places (and helps cut
down IRGenerator, as we transition away from it).

Change-Id: Ie88c149e0f7eee080a8a4c8cbbc34c8a2a5401d1
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/449756
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>

bench/SkSLBench.cpp

@@ -139,11 +139,12 @@ protected:
 
     void onDraw(int loops, SkCanvas*) override {
         for (int i = 0; i < loops; i++) {
-            fCompiler.irGenerator().pushSymbolTable();
-            SkSL::Parser parser(fSrc, *fCompiler.irGenerator().symbolTable(),
-                                fCompiler.errorReporter());
-            parser.compilationUnit();
-            fCompiler.irGenerator().popSymbolTable();
+            {
+                SkSL::AutoSymbolTable table(&fCompiler.irGenerator().symbolTable());
+                SkSL::Parser parser(fSrc, *fCompiler.irGenerator().symbolTable(),
+                                    fCompiler.errorReporter());
+                parser.compilationUnit();
+            }
             if (fCompiler.errorCount()) {
                 SK_ABORT("shader compilation failed: %s\n", fCompiler.errorText().c_str());
             }

src/sksl/SkSLIRGenerator.cpp

@@ -62,35 +62,9 @@
 
 namespace SkSL {
 
-class AutoSymbolTable {
-public:
-    AutoSymbolTable(IRGenerator* ir)
-    : fIR(ir)
-    , fPrevious(fIR->fSymbolTable) {
-        fIR->pushSymbolTable();
-    }
-
-    ~AutoSymbolTable() {
-        fIR->popSymbolTable();
-        SkASSERT(fPrevious == fIR->fSymbolTable);
-    }
-
-    IRGenerator* fIR;
-    std::shared_ptr<SymbolTable> fPrevious;
-};
-
 IRGenerator::IRGenerator(const Context* context)
         : fContext(*context) {}
 
-void IRGenerator::pushSymbolTable() {
-    auto childSymTable = std::make_shared<SymbolTable>(std::move(fSymbolTable), fIsBuiltinCode);
-    fSymbolTable = std::move(childSymTable);
-}
-
-void IRGenerator::popSymbolTable() {
-    fSymbolTable = fSymbolTable->fParent;
-}
-
 std::unique_ptr<Extension> IRGenerator::convertExtension(int offset, skstd::string_view name) {
     if (this->programKind() != ProgramKind::kFragment &&
         this->programKind() != ProgramKind::kVertex) {
@@ -136,7 +110,7 @@ std::unique_ptr<Statement> IRGenerator::convertStatement(const ASTNode& statemen
 
 std::unique_ptr<Block> IRGenerator::convertBlock(const ASTNode& block) {
     SkASSERT(block.fKind == ASTNode::Kind::kBlock);
-    AutoSymbolTable table(this);
+    AutoSymbolTable table(&fSymbolTable);
     StatementArray statements;
     for (const auto& child : block) {
         std::unique_ptr<Statement> statement = this->convertStatement(child);
@@ -398,7 +372,7 @@ std::unique_ptr<Statement> IRGenerator::convertIf(const ASTNode& n) {
 
 std::unique_ptr<Statement> IRGenerator::convertFor(const ASTNode& f) {
     SkASSERT(f.fKind == ASTNode::Kind::kFor);
-    AutoSymbolTable table(this);
+    AutoSymbolTable table(&fSymbolTable);
     std::unique_ptr<Statement> initializer;
     auto iter = f.begin();
     if (*iter) {
@@ -470,7 +444,7 @@ std::unique_ptr<Statement> IRGenerator::convertSwitch(const ASTNode& s) {
     if (!value) {
         return nullptr;
     }
-    AutoSymbolTable table(this);
+    AutoSymbolTable table(&fSymbolTable);
     ExpressionArray caseValues;
     StatementArray caseStatements;
     for (; iter != s.end(); ++iter) {
@@ -714,7 +688,7 @@ void IRGenerator::convertFunction(const ASTNode& f) {
                                                                         fIsBuiltinCode));
     } else {
         // Compile function body.
-        AutoSymbolTable table(this);
+        AutoSymbolTable table(&fSymbolTable);
         for (const Variable* param : decl->parameters()) {
             fSymbolTable->addWithoutOwnership(param);
         }
@@ -778,7 +752,7 @@ std::unique_ptr<SkSL::InterfaceBlock> IRGenerator::convertInterfaceBlock(const A
     std::vector<Type::Field> fields;
     auto iter = intf.begin();
     {
-        AutoSymbolTable table(this);
+        AutoSymbolTable table(&fSymbolTable);
         symbols = fSymbolTable;
         for (size_t i = 0; i < id.fDeclarationCount; ++i) {
             StatementArray decls = this->convertVarDeclarations(*(iter++),
@@ -1326,7 +1300,7 @@ void IRGenerator::start(const ParsedModule& base,
     fRTAdjust = nullptr;
     fRTAdjustInterfaceBlock = nullptr;
     fDefinedStructs.clear();
-    this->pushSymbolTable();
+    SymbolTable::Push(&fSymbolTable, fIsBuiltinCode);
 
     if (this->settings().fExternalFunctions) {
         // Add any external values to the new symbol table, so they're only visible to this Program.

src/sksl/SkSLIRGenerator.h

@@ -133,9 +133,6 @@ public:
         fSymbolTable = symbolTable;
     }
 
-    void pushSymbolTable();
-    void popSymbolTable();
-
     static void CheckModifiers(const Context& context,
                                int offset,
                                const Modifiers& modifiers,

src/sksl/dsl/DSLSymbols.cpp

@@ -15,11 +15,11 @@ namespace SkSL {
 namespace dsl {
 
 void PushSymbolTable() {
-    DSLWriter::IRGenerator().pushSymbolTable();
+    SymbolTable::Push(&DSLWriter::IRGenerator().symbolTable());
 }
 
 void PopSymbolTable() {
-    DSLWriter::IRGenerator().popSymbolTable();
+    SymbolTable::Pop(&DSLWriter::IRGenerator().symbolTable());
 }
 
 std::shared_ptr<SymbolTable> CurrentSymbolTable() {

src/sksl/dsl/priv/DSLWriter.cpp

@@ -9,6 +9,7 @@
 
 #include "include/private/SkSLDefines.h"
 #include "include/sksl/DSLCore.h"
+#include "include/sksl/DSLSymbols.h"
 #include "include/sksl/SkSLErrorReporter.h"
 #if !defined(SKSL_STANDALONE) && SK_SUPPORT_GPU
 #include "src/gpu/glsl/GrGLSLFragmentShaderBuilder.h"
@@ -94,8 +95,8 @@ const std::shared_ptr<SkSL::SymbolTable>& DSLWriter::SymbolTable() {
 }
 
 void DSLWriter::Reset() {
-    IRGenerator().popSymbolTable();
-    IRGenerator().pushSymbolTable();
+    dsl::PopSymbolTable();
+    dsl::PushSymbolTable();
     ProgramElements().clear();
     Instance().fModifiersPool->clear();
 }
@@ -119,7 +120,7 @@ void DSLWriter::StartFragmentProcessor(GrFragmentProcessor::ProgramImpl* process
     DSLWriter& instance = Instance();
     instance.fStack.push({processor, emitArgs, StatementArray{}});
     CurrentEmitArgs()->fFragBuilder->fDeclarations.swap(instance.fStack.top().fSavedDeclarations);
-    IRGenerator().pushSymbolTable();
+    dsl::PushSymbolTable();
 }
 
 void DSLWriter::EndFragmentProcessor() {
@@ -127,7 +128,7 @@ void DSLWriter::EndFragmentProcessor() {
     SkASSERT(!instance.fStack.empty());
     CurrentEmitArgs()->fFragBuilder->fDeclarations.swap(instance.fStack.top().fSavedDeclarations);
     instance.fStack.pop();
-    IRGenerator().popSymbolTable();
+    dsl::PopSymbolTable();
 }
 
 GrGLSLUniformHandler::UniformHandle DSLWriter::VarUniformHandle(const DSLGlobalVar& var) {

src/sksl/ir/SkSLSymbolTable.h

@@ -37,6 +37,22 @@ public:
     , fBuiltin(builtin)
     , fContext(parent->fContext) {}
 
+    /** Replaces the passed-in SymbolTable with a newly-created child symbol table. */
+    static void Push(std::shared_ptr<SymbolTable>* table) {
+        Push(table, (*table)->isBuiltin());
+    }
+    static void Push(std::shared_ptr<SymbolTable>* table, bool isBuiltin) {
+        *table = std::make_shared<SymbolTable>(*table, isBuiltin);
+    }
+
+    /**
+     * Replaces the passed-in SymbolTable with its parent. If the child symbol table is otherwise
+     * unreferenced, it will be deleted.
+     */
+    static void Pop(std::shared_ptr<SymbolTable>* table) {
+        *table = (*table)->fParent;
+    }
+
     /**
      * If the input is a built-in symbol table, returns a new empty symbol table as a child of the
      * input table. If the input is not a built-in symbol table, returns it as-is. Built-in symbol
@@ -146,6 +162,26 @@ private:
     friend class Dehydrator;
 };
 
+/**
+ * While in scope, the passed-in symbol table is replaced with a child symbol table.
+ */
+class AutoSymbolTable {
+public:
+    AutoSymbolTable(std::shared_ptr<SymbolTable>* s)
+        : fSymbolTable(s) {
+        SkDEBUGCODE(fPrevious = fSymbolTable->get();)
+        SymbolTable::Push(fSymbolTable);
+    }
+
+    ~AutoSymbolTable() {
+        SymbolTable::Pop(fSymbolTable);
+        SkASSERT(fPrevious == fSymbolTable->get());
+    }
+
+    std::shared_ptr<SymbolTable>* fSymbolTable;
+    SkDEBUGCODE(SymbolTable* fPrevious;)
+};
+
 }  // namespace SkSL
 
 #endif