GLSL: add location layout qualifier before in/out variables.

Bug: tint:1398
Change-Id: I89c985d01d539ed166661ee5e858247cde4702b3
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/78080
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Stephen White <senorblanco@chromium.org>

src/writer/glsl/generator_impl.cc

@@ -1877,6 +1877,25 @@ std::string GeneratorImpl::interpolation_to_modifiers(
   return modifiers;
 }
 
+bool GeneratorImpl::EmitDecorations(std::ostream& out,
+                                    const ast::DecorationList& decorations) {
+  if (decorations.empty()) {
+    return true;
+  }
+  bool first = true;
+  for (auto* deco : decorations) {
+    if (auto* location = deco->As<ast::LocationDecoration>()) {
+      out << (first ? "layout(" : ", ");
+      out << "location = " << std::to_string(location->value);
+      first = false;
+    }
+  }
+  if (!first) {
+    out << ") ";
+  }
+  return true;
+}
+
 bool GeneratorImpl::EmitEntryPointFunction(const ast::Function* func) {
   auto* func_sem = builder_.Sem().Get(func);
 
@@ -1962,10 +1981,13 @@ bool GeneratorImpl::EmitEntryPointFunction(const ast::Function* func) {
     auto* sem = builder_.Sem().Get(var);
     auto* str = sem->Type()->As<sem::Struct>();
     for (auto* member : str->Members()) {
-      if (ast::HasDecoration<ast::BuiltinDecoration>(
-              member->Declaration()->decorations)) {
+      auto decorations = member->Declaration()->decorations;
+      if (ast::HasDecoration<ast::BuiltinDecoration>(decorations)) {
         continue;
       }
+      if (!EmitDecorations(out, decorations)) {
+        return false;
+      }
       if (!EmitTypeAndName(
               out, member->Type(), ast::StorageClass::kInput,
               ast::Access::kReadWrite,
@@ -1980,10 +2002,13 @@ bool GeneratorImpl::EmitEntryPointFunction(const ast::Function* func) {
   auto* return_type = func_sem->ReturnType()->As<sem::Struct>();
   if (return_type) {
     for (auto* member : return_type->Members()) {
-      if (ast::HasDecoration<ast::BuiltinDecoration>(
-              member->Declaration()->decorations)) {
+      auto decorations = member->Declaration()->decorations;
+      if (ast::HasDecoration<ast::BuiltinDecoration>(decorations)) {
         continue;
       }
+      if (!EmitDecorations(out, decorations)) {
+        return false;
+      }
       if (!EmitTypeAndName(
               out, member->Type(), ast::StorageClass::kOutput,
               ast::Access::kReadWrite,

src/writer/glsl/generator_impl.h

@@ -292,6 +292,11 @@ class GeneratorImpl : public TextGenerator {
   /// @returns true on success
   bool EmitWorkgroupVariable(const sem::Variable* var);
 
+  /// Handles emitting decorations
+  /// @param out the output of the expression stream
+  /// @param decos the decorations
+  /// @returns true if the decorations were emitted
+  bool EmitDecorations(std::ostream& out, const ast::DecorationList& decos);
   /// Handles emitting the entry point function
   /// @param func the entry point
   /// @returns true if the entry point function was emitted
@@ -316,7 +321,7 @@ class GeneratorImpl : public TextGenerator {
   /// Handles generating an identifier expression
   /// @param out the output of the expression stream
   /// @param expr the identifier expression
-  /// @returns true if the identifeir was emitted
+  /// @returns true if the identifier was emitted
   bool EmitIdentifier(std::ostream& out, const ast::IdentifierExpression* expr);
   /// Handles a member accessor expression
   /// @param out the output of the expression stream

src/writer/glsl/generator_impl_function_test.cc

@@ -157,8 +157,8 @@ tint_symbol_2 frag_main(tint_symbol_1 tint_symbol) {
   wrapper_result.value = inner_result;
   return wrapper_result;
 }
-in float foo;
-out float value;
+layout(location = 0) in float foo;
+layout(location = 1) out float value;
 void main() {
   tint_symbol_1 inputs;
   inputs.foo = foo;
@@ -284,8 +284,8 @@ tint_symbol vert_main() {
   wrapper_result.col2 = inner_result.col2;
   return wrapper_result;
 }
-out float col1;
-out float col2;
+layout(location = 1) out float col1;
+layout(location = 2) out float col2;
 void main() {
   tint_symbol outputs;
   outputs = vert_main();
@@ -314,8 +314,8 @@ void frag_main(tint_symbol_2 tint_symbol_1) {
   frag_main_inner(tint_symbol_4);
   return;
 }
-in float col1;
-in float col2;
+layout(location = 1) in float col1;
+layout(location = 2) in float col2;
 void main() {
   tint_symbol_2 inputs;
   inputs.col1 = col1;