Add IdentifierExpression to WGSL writer.

This CL extends the WGSL writer to output IdentiferExpression and fills
out the variable with initializer test case and implementation.

Bug: tint:4
Change-Id: I9db9affb5ec4c4c109488f60bbc81bf3a96eee35
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/16744
Reviewed-by: David Neto <dneto@google.com>

src/writer/wgsl/generator_impl.cc

@@ -19,6 +19,7 @@
 #include "src/ast/binding_decoration.h"
 #include "src/ast/builtin_decoration.h"
 #include "src/ast/decorated_variable.h"
+#include "src/ast/identifier_expression.h"
 #include "src/ast/location_decoration.h"
 #include "src/ast/set_decoration.h"
 #include "src/ast/struct.h"
@@ -76,7 +77,14 @@ bool GeneratorImpl::Generate(const ast::Module& module) {
   return true;
 }
 
+void GeneratorImpl::make_indent() {
+  for (size_t i = 0; i < indent_; i++) {
+    out_ << " ";
+  }
+}
+
 bool GeneratorImpl::EmitAliasType(const ast::type::AliasType* alias) {
+  make_indent();
   out_ << "type " << alias->name() << " = ";
   if (!EmitType(alias->type())) {
     return false;
@@ -87,6 +95,7 @@ bool GeneratorImpl::EmitAliasType(const ast::type::AliasType* alias) {
 }
 
 bool GeneratorImpl::EmitEntryPoint(const ast::EntryPoint* ep) {
+  make_indent();
   out_ << "entry_point " << ep->stage() << " ";
   if (!ep->name().empty() && ep->name() != ep->function_name()) {
     out_ << R"(as ")" << ep->name() << R"(" )";
@@ -96,7 +105,25 @@ bool GeneratorImpl::EmitEntryPoint(const ast::EntryPoint* ep) {
   return true;
 }
 
+bool GeneratorImpl::EmitExpression(ast::Expression* expr) {
+  if (expr->IsIdentifier()) {
+    bool first = true;
+    for (const auto& part : expr->AsIdentifier()->name()) {
+      if (!first) {
+        out_ << "::";
+      }
+      first = false;
+      out_ << part;
+    }
+  } else {
+    error_ = "unknown expression type";
+    return false;
+  }
+  return true;
+}
+
 bool GeneratorImpl::EmitImport(const ast::Import* import) {
+  make_indent();
   out_ << R"(import ")" << import->path() << R"(" as )" << import->name() << ";"
        << std::endl;
   return true;
@@ -143,9 +170,10 @@ bool GeneratorImpl::EmitType(ast::type::Type* type) {
       out_ << "[[" << str->decoration() << "]] ";
     }
     out_ << "struct {" << std::endl;
+
+    increment_indent();
     for (const auto& mem : str->members()) {
-      // TODO(dsinclair): This formats bad with nested structs
-      out_ << "  ";
+      make_indent();
       if (!mem->decorations().empty()) {
         out_ << "[[";
         bool first = true;
@@ -169,6 +197,8 @@ bool GeneratorImpl::EmitType(ast::type::Type* type) {
       }
       out_ << ";" << std::endl;
     }
+    decrement_indent();
+    make_indent();
 
     out_ << "}";
   } else if (type->IsU32()) {
@@ -191,6 +221,8 @@ bool GeneratorImpl::EmitType(ast::type::Type* type) {
 }
 
 bool GeneratorImpl::EmitVariable(ast::Variable* var) {
+  make_indent();
+
   if (var->IsDecorated()) {
     if (!EmitVariableDecorations(var->AsDecorated())) {
       return false;
@@ -212,8 +244,10 @@ bool GeneratorImpl::EmitVariable(ast::Variable* var) {
   }
 
   if (var->initializer() != nullptr) {
-    // out_ << " = ";
-    // EmitExpr(var-initializer());
+    out_ << " = ";
+    if (!EmitExpression(var->initializer())) {
+      return false;
+    }
   }
   out_ << ";" << std::endl;
 

src/writer/wgsl/generator_impl.h

@@ -47,6 +47,20 @@ class GeneratorImpl {
   /// @returns the error from the generator
   std::string error() const { return error_; }
 
+  /// Increment the emitter indent level
+  void increment_indent() { indent_ += 2; }
+  /// Decrement the emiter indent level
+  void decrement_indent() {
+    if (indent_ < 2) {
+      indent_ = 0;
+      return;
+    }
+    indent_ -= 2;
+  }
+
+  /// Writes the current indent to the output stream
+  void make_indent();
+
   /// Handles generating an alias
   /// @param alias the alias to generate
   /// @returns true if the alias was emitted
@@ -55,6 +69,10 @@ class GeneratorImpl {
   /// @param ep the entry point
   /// @returns true if the entry point was emitted
   bool EmitEntryPoint(const ast::EntryPoint* ep);
+  /// Handles generate an Expression
+  /// @param expr the expression
+  /// @returns true if the expression was emitted
+  bool EmitExpression(ast::Expression* expr);
   /// Handles generating an import command
   /// @param import the import to generate
   /// @returns true if the import was emitted
@@ -73,6 +91,7 @@ class GeneratorImpl {
   bool EmitVariableDecorations(ast::DecoratedVariable* var);
 
  private:
+  size_t indent_ = 0;
   std::ostringstream out_;
   std::string error_;
 };

src/writer/wgsl/generator_impl_test.cc

@@ -23,6 +23,7 @@
 #include "src/ast/builtin.h"
 #include "src/ast/builtin_decoration.h"
 #include "src/ast/decorated_variable.h"
+#include "src/ast/identifier_expression.h"
 #include "src/ast/location_decoration.h"
 #include "src/ast/set_decoration.h"
 #include "src/ast/struct.h"
@@ -83,7 +84,7 @@ TEST_F(GeneratorImplTest, DISABLED_EmitAliasType_Struct) {
   GeneratorImpl g;
   ASSERT_TRUE(g.EmitAliasType(&alias));
   EXPECT_EQ(g.result(), R"(type a = struct {
-  a: f32;
+  a : f32;
   [[offset 4]] b : i32;
 }
 )");
@@ -322,9 +323,48 @@ TEST_F(GeneratorImplTest, EmitVariable_Decorated_Multiple) {
 )");
 }
 
-TEST_F(GeneratorImplTest, DISABLED_EmitVariable_Initializer) {}
+TEST_F(GeneratorImplTest, EmitVariable_Initializer) {
+  auto ident = std::make_unique<ast::IdentifierExpression>("initializer");
 
-TEST_F(GeneratorImplTest, DISABLED_EmitVariable_Const) {}
+  ast::type::F32Type f32;
+  ast::Variable v("a", ast::StorageClass::kNone, &f32);
+  v.set_initializer(std::move(ident));
+
+  GeneratorImpl g;
+  ASSERT_TRUE(g.EmitVariable(&v));
+  EXPECT_EQ(g.result(), R"(var a : f32 = initializer;
+)");
+}
+
+TEST_F(GeneratorImplTest, EmitVariable_Const) {
+  auto ident = std::make_unique<ast::IdentifierExpression>("initializer");
+
+  ast::type::F32Type f32;
+  ast::Variable v("a", ast::StorageClass::kNone, &f32);
+  v.set_initializer(std::move(ident));
+  v.set_is_const(true);
+
+  GeneratorImpl g;
+  ASSERT_TRUE(g.EmitVariable(&v));
+  EXPECT_EQ(g.result(), R"(const a : f32 = initializer;
+)");
+}
+
+TEST_F(GeneratorImplTest, EmitExpression_Identifier) {
+  ast::IdentifierExpression i("init");
+
+  GeneratorImpl g;
+  ASSERT_TRUE(g.EmitExpression(&i));
+  EXPECT_EQ(g.result(), "init");
+}
+
+TEST_F(GeneratorImplTest, EmitExpression_Identifier_MultipleNames) {
+  ast::IdentifierExpression i({"std", "glsl", "init"});
+
+  GeneratorImpl g;
+  ASSERT_TRUE(g.EmitExpression(&i));
+  EXPECT_EQ(g.result(), "std::glsl::init");
+}
 
 }  // namespace
 }  // namespace wgsl