[hlsl-writer] Add read-only storage buffers.

This CL updates the HLSL backend to emit based on the AccessControlType.

Bug: tint:208 tint:108
Change-Id: I25baccaaa9af99a214467fe67d55a2f4256dab8c
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/31105
Commit-Queue: dan sinclair <dsinclair@chromium.org>
Reviewed-by: David Neto <dneto@google.com>

src/writer/hlsl/generator_impl.cc

@@ -35,6 +35,7 @@
 #include "src/ast/sint_literal.h"
 #include "src/ast/struct.h"
 #include "src/ast/switch_statement.h"
+#include "src/ast/type/access_control_type.h"
 #include "src/ast/type/alias_type.h"
 #include "src/ast/type/array_type.h"
 #include "src/ast/type/f32_type.h"
@@ -1206,7 +1207,16 @@ bool GeneratorImpl::EmitEntryPointData(std::ostream& out, ast::Function* func) {
     auto* var = data.first;
     auto* binding = data.second.binding;
 
-    out << "RWByteAddressBuffer " << var->name() << " : register(u"
+    if (!var->type()->IsAccessControl()) {
+      error_ = "access control type required for storage buffer";
+      return false;
+    }
+    auto* ac = var->type()->AsAccessControl();
+
+    if (ac->IsReadWrite()) {
+      out << "RW";
+    }
+    out << "ByteAddressBuffer " << var->name() << " : register(u"
         << binding->value() << ");" << std::endl;
     emitted_storagebuffer = true;
   }

src/writer/hlsl/generator_impl_function_test.cc

@@ -32,6 +32,7 @@
 #include "src/ast/stage_decoration.h"
 #include "src/ast/struct.h"
 #include "src/ast/struct_member_offset_decoration.h"
+#include "src/ast/type/access_control_type.h"
 #include "src/ast/type/array_type.h"
 #include "src/ast/type/f32_type.h"
 #include "src/ast/type/i32_type.h"
@@ -362,7 +363,7 @@ void frag_main() {
 }
 
 TEST_F(HlslGeneratorImplTest_Function,
-       Emit_FunctionDecoration_EntryPoint_With_StorageBuffer_Read) {
+       Emit_FunctionDecoration_EntryPoint_With_RW_StorageBuffer_Read) {
   ast::type::VoidType void_type;
   ast::type::F32Type f32;
   ast::type::I32Type i32;
@@ -382,10 +383,11 @@ TEST_F(HlslGeneratorImplTest_Function,
   str->set_members(std::move(members));
 
   ast::type::StructType s("Data", std::move(str));
+  ast::type::AccessControlType ac(ast::type::AccessControl::kReadWrite, &s);
 
   auto coord_var =
       std::make_unique<ast::DecoratedVariable>(std::make_unique<ast::Variable>(
-          "coord", ast::StorageClass::kStorageBuffer, &s));
+          "coord", ast::StorageClass::kStorageBuffer, &ac));
 
   ast::VariableDecorationList decos;
   decos.push_back(std::make_unique<ast::BindingDecoration>(0));
@@ -426,6 +428,72 @@ void frag_main() {
 )");
 }
 
+TEST_F(HlslGeneratorImplTest_Function,
+       Emit_FunctionDecoration_EntryPoint_With_RO_StorageBuffer_Read) {
+  ast::type::VoidType void_type;
+  ast::type::F32Type f32;
+  ast::type::I32Type i32;
+
+  ast::StructMemberList members;
+  ast::StructMemberDecorationList a_deco;
+  a_deco.push_back(std::make_unique<ast::StructMemberOffsetDecoration>(0));
+  members.push_back(
+      std::make_unique<ast::StructMember>("a", &i32, std::move(a_deco)));
+
+  ast::StructMemberDecorationList b_deco;
+  b_deco.push_back(std::make_unique<ast::StructMemberOffsetDecoration>(4));
+  members.push_back(
+      std::make_unique<ast::StructMember>("b", &f32, std::move(b_deco)));
+
+  auto str = std::make_unique<ast::Struct>();
+  str->set_members(std::move(members));
+
+  ast::type::StructType s("Data", std::move(str));
+  ast::type::AccessControlType ac(ast::type::AccessControl::kReadOnly, &s);
+
+  auto coord_var =
+      std::make_unique<ast::DecoratedVariable>(std::make_unique<ast::Variable>(
+          "coord", ast::StorageClass::kStorageBuffer, &ac));
+
+  ast::VariableDecorationList decos;
+  decos.push_back(std::make_unique<ast::BindingDecoration>(0));
+  decos.push_back(std::make_unique<ast::SetDecoration>(1));
+  coord_var->set_decorations(std::move(decos));
+
+  td().RegisterVariableForTesting(coord_var.get());
+  mod()->AddGlobalVariable(std::move(coord_var));
+
+  ast::VariableList params;
+  auto func = std::make_unique<ast::Function>("frag_main", std::move(params),
+                                              &void_type);
+  func->add_decoration(
+      std::make_unique<ast::StageDecoration>(ast::PipelineStage::kFragment));
+
+  auto var =
+      std::make_unique<ast::Variable>("v", ast::StorageClass::kFunction, &f32);
+  var->set_constructor(std::make_unique<ast::MemberAccessorExpression>(
+      std::make_unique<ast::IdentifierExpression>("coord"),
+      std::make_unique<ast::IdentifierExpression>("b")));
+
+  auto body = std::make_unique<ast::BlockStatement>();
+  body->append(std::make_unique<ast::VariableDeclStatement>(std::move(var)));
+  body->append(std::make_unique<ast::ReturnStatement>());
+  func->set_body(std::move(body));
+
+  mod()->AddFunction(std::move(func));
+
+  ASSERT_TRUE(td().Determine()) << td().error();
+  ASSERT_TRUE(gen().Generate(out())) << gen().error();
+  EXPECT_EQ(result(), R"(ByteAddressBuffer coord : register(u0);
+
+void frag_main() {
+  float v = asfloat(coord.Load(4));
+  return;
+}
+
+)");
+}
+
 TEST_F(HlslGeneratorImplTest_Function,
        Emit_FunctionDecoration_EntryPoint_With_StorageBuffer_Store) {
   ast::type::VoidType void_type;
@@ -447,10 +515,11 @@ TEST_F(HlslGeneratorImplTest_Function,
   str->set_members(std::move(members));
 
   ast::type::StructType s("Data", std::move(str));
+  ast::type::AccessControlType ac(ast::type::AccessControl::kReadWrite, &s);
 
   auto coord_var =
       std::make_unique<ast::DecoratedVariable>(std::make_unique<ast::Variable>(
-          "coord", ast::StorageClass::kStorageBuffer, &s));
+          "coord", ast::StorageClass::kStorageBuffer, &ac));
 
   ast::VariableDecorationList decos;
   decos.push_back(std::make_unique<ast::BindingDecoration>(0));
@@ -830,10 +899,10 @@ TEST_F(HlslGeneratorImplTest_Function,
   ast::type::VoidType void_type;
   ast::type::F32Type f32;
   ast::type::VectorType vec4(&f32, 4);
-
+  ast::type::AccessControlType ac(ast::type::AccessControl::kReadWrite, &vec4);
   auto coord_var =
       std::make_unique<ast::DecoratedVariable>(std::make_unique<ast::Variable>(
-          "coord", ast::StorageClass::kStorageBuffer, &vec4));
+          "coord", ast::StorageClass::kStorageBuffer, &ac));
 
   ast::VariableDecorationList decos;
   decos.push_back(std::make_unique<ast::BindingDecoration>(0));