tint/writer: Handle diagnostic directives

The WGSL writer emits them, the other writers ignore them.

Bug: tint:1809
Change-Id: I163d868005c076b8fd4602f13d3e267b16c474c0
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/117567
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>

src/tint/BUILD.gn

@@ -1672,6 +1672,7 @@ if (tint_build_unittests) {
       "writer/wgsl/generator_impl_cast_test.cc",
       "writer/wgsl/generator_impl_const_assert_test.cc",
       "writer/wgsl/generator_impl_continue_test.cc",
+      "writer/wgsl/generator_impl_diagnostic_test.cc",
       "writer/wgsl/generator_impl_discard_test.cc",
       "writer/wgsl/generator_impl_enable_test.cc",
       "writer/wgsl/generator_impl_function_test.cc",

src/tint/CMakeLists.txt

@@ -1212,6 +1212,7 @@ if(TINT_BUILD_TESTS)
       writer/wgsl/generator_impl_cast_test.cc
       writer/wgsl/generator_impl_const_assert_test.cc
       writer/wgsl/generator_impl_continue_test.cc
+      writer/wgsl/generator_impl_diagnostic_test.cc
       writer/wgsl/generator_impl_discard_test.cc
       writer/wgsl/generator_impl_enable_test.cc
       writer/wgsl/generator_impl_function_test.cc

src/tint/writer/glsl/generator_impl.cc

@@ -250,7 +250,7 @@ bool GeneratorImpl::Generate() {
 
     auto* mod = builder_.Sem().Module();
     for (auto* decl : mod->DependencyOrderedDeclarations()) {
-        if (decl->IsAnyOf<ast::Alias, ast::ConstAssert>()) {
+        if (decl->IsAnyOf<ast::Alias, ast::ConstAssert, ast::DiagnosticControl>()) {
             continue;  // These are not emitted.
         }
 

src/tint/writer/hlsl/generator_impl.cc

@@ -310,7 +310,7 @@ bool GeneratorImpl::Generate() {
 
     auto* mod = builder_.Sem().Module();
     for (auto* decl : mod->DependencyOrderedDeclarations()) {
-        if (decl->IsAnyOf<ast::Alias, ast::Enable, ast::ConstAssert>()) {
+        if (decl->IsAnyOf<ast::Alias, ast::DiagnosticControl, ast::Enable, ast::ConstAssert>()) {
             continue;  // These are not emitted.
         }
 

src/tint/writer/msl/generator_impl.cc

@@ -313,6 +313,10 @@ bool GeneratorImpl::Generate() {
                 }
                 return EmitFunction(func);
             },
+            [&](const ast::DiagnosticControl*) {
+                // Do nothing for diagnostic directives in MSL
+                return true;
+            },
             [&](const ast::Enable*) {
                 // Do nothing for enabling extension in MSL
                 return true;

src/tint/writer/wgsl/generator_impl.cc

@@ -63,18 +63,28 @@ GeneratorImpl::GeneratorImpl(const Program* program) : TextGenerator(program) {}
 GeneratorImpl::~GeneratorImpl() = default;
 
 bool GeneratorImpl::Generate() {
-    // Generate enable directives before any other global declarations.
+    // Generate directives before any other global declarations.
+    bool has_directives = false;
     for (auto enable : program_->AST().Enables()) {
         if (!EmitEnable(enable)) {
             return false;
         }
+        has_directives = true;
     }
-    if (!program_->AST().Enables().IsEmpty()) {
+    for (auto diagnostic : program_->AST().DiagnosticControls()) {
+        auto out = line();
+        if (!EmitDiagnosticControl(out, diagnostic)) {
+            return false;
+        }
+        out << ";";
+        has_directives = true;
+    }
+    if (has_directives) {
         line();
     }
     // Generate global declarations in the order they appear in the module.
     for (auto* decl : program_->AST().GlobalDeclarations()) {
-        if (decl->Is<ast::Enable>()) {
+        if (decl->IsAnyOf<ast::DiagnosticControl, ast::Enable>()) {
             continue;
         }
         if (!Switch(
@@ -97,6 +107,13 @@ bool GeneratorImpl::Generate() {
     return true;
 }
 
+bool GeneratorImpl::EmitDiagnosticControl(std::ostream& out,
+                                          const ast::DiagnosticControl* diagnostic) {
+    out << "diagnostic(" << diagnostic->severity << ", "
+        << program_->Symbols().NameFor(diagnostic->rule_name->symbol) << ")";
+    return true;
+}
+
 bool GeneratorImpl::EmitEnable(const ast::Enable* enable) {
     auto out = line();
     out << "enable " << enable->extension << ";";

src/tint/writer/wgsl/generator_impl.h

@@ -52,7 +52,12 @@ class GeneratorImpl : public TextGenerator {
     /// @returns true on successful generation; false otherwise
     bool Generate();
 
-    /// Handles generating a enable directive
+    /// Handles generating a diagnostic control
+    /// @param out the output of the expression stream
+    /// @param diagnostic the diagnostic control node
+    /// @returns true if the diagnostic control was emitted
+    bool EmitDiagnosticControl(std::ostream& out, const ast::DiagnosticControl* diagnostic);
+    /// Handles generating an enable directive
     /// @param enable the enable node
     /// @returns true if the enable directive was emitted
     bool EmitEnable(const ast::Enable* enable);

src/tint/writer/wgsl/generator_impl_diagnostic_test.cc

@@ -0,0 +1,34 @@
+// Copyright 2022 The Tint Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "src/tint/writer/wgsl/test_helper.h"
+
+namespace tint::writer::wgsl {
+namespace {
+
+using WgslGeneratorImplTest = TestHelper;
+
+TEST_F(WgslGeneratorImplTest, Emit_DiagnosticDirective) {
+    DiagnosticDirective(ast::DiagnosticSeverity::kError, Expr("chromium_unreachable_code"));
+
+    GeneratorImpl& gen = Build();
+
+    ASSERT_TRUE(gen.Generate());
+    EXPECT_EQ(gen.result(), R"(diagnostic(error, chromium_unreachable_code);
+
+)");
+}
+
+}  // namespace
+}  // namespace tint::writer::wgsl