[spirv-writer] Start accessor chain additions.

This Cl adds the code for the ArrayAccessor generation. Some of the
MemberAccessor code is included, but tests are coming in a later Cl.

Bug: tint:5
Change-Id: Id7d006ab4a82c1d31d8036d141c83d0d61f9bea5
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/20180
Reviewed-by: David Neto <dneto@google.com>

BUILD.gn

@@ -552,6 +552,7 @@ source_set("tint_unittests_spv_reader_src") {
 source_set("tint_unittests_spv_writer_src") {
   sources = [
     "src/writer/spirv/binary_writer_test.cc",
+    "src/writer/spirv/builder_accessor_expression_test.cc",
     "src/writer/spirv/builder_assign_test.cc",
     "src/writer/spirv/builder_binary_expression_test.cc",
     "src/writer/spirv/builder_call_test.cc",

src/CMakeLists.txt

@@ -425,6 +425,7 @@ endif()
 if(${TINT_BUILD_SPV_WRITER})
   list(APPEND TINT_TEST_SRCS
     writer/spirv/binary_writer_test.cc
+    writer/spirv/builder_accessor_expression_test.cc
     writer/spirv/builder_assign_test.cc
     writer/spirv/builder_binary_expression_test.cc
     writer/spirv/builder_call_test.cc

src/writer/spirv/builder.cc

@@ -17,6 +17,7 @@
 #include <utility>
 
 #include "spirv/unified1/spirv.h"
+#include "src/ast/array_accessor_expression.h"
 #include "src/ast/assignment_statement.h"
 #include "src/ast/binary_expression.h"
 #include "src/ast/binding_decoration.h"
@@ -32,6 +33,7 @@
 #include "src/ast/int_literal.h"
 #include "src/ast/location_decoration.h"
 #include "src/ast/loop_statement.h"
+#include "src/ast/member_accessor_expression.h"
 #include "src/ast/return_statement.h"
 #include "src/ast/scalar_constructor_expression.h"
 #include "src/ast/set_decoration.h"
@@ -198,6 +200,9 @@ bool Builder::GenerateEntryPoint(ast::EntryPoint* ep) {
 }
 
 uint32_t Builder::GenerateExpression(ast::Expression* expr) {
+  if (expr->IsArrayAccessor()) {
+    return GenerateAccessorExpression(expr->AsArrayAccessor());
+  }
   if (expr->IsBinary()) {
     return GenerateBinaryExpression(expr->AsBinary());
   }
@@ -436,6 +441,77 @@ bool Builder::GenerateGlobalVariable(ast::Variable* var) {
   return true;
 }
 
+uint32_t Builder::GenerateAccessorExpression(ast::Expression* expr) {
+  assert(expr->IsArrayAccessor() || expr->IsMemberAccessor());
+
+  auto result = result_op();
+  auto result_id = result.to_i();
+
+  std::vector<Operand> idx_list;
+
+  ast::Expression* source = expr;
+  while (true) {
+    if (source->IsArrayAccessor()) {
+      auto* ary_accessor = source->AsArrayAccessor();
+      source = ary_accessor->array();
+
+      auto idx = GenerateExpression(ary_accessor->idx_expr());
+      if (idx == 0) {
+        return 0;
+      }
+      idx_list.insert(idx_list.begin(), Operand::Int(idx));
+
+    } else if (source->IsMemberAccessor()) {
+      auto* mem_accessor = source->AsMemberAccessor();
+      source = mem_accessor->structure();
+
+      auto* data_type = mem_accessor->structure()->result_type();
+      if (data_type->IsStruct()) {
+        auto* strct = data_type->AsStruct()->impl();
+        auto name = mem_accessor->member()->name();
+
+        uint32_t i = 0;
+        for (; i < strct->members().size(); ++i) {
+          const auto& member = strct->members()[i];
+          if (member->name() != name) {
+            continue;
+          }
+
+          break;
+        }
+        idx_list.insert(idx_list.begin(), Operand::Int(i));
+
+      } else if (data_type->IsVector()) {
+        // TODO(dsinclair): Handle swizzle
+      } else {
+        error_ = "invalid type for member accessor";
+        return 0;
+      }
+    } else {
+      break;
+    }
+  }
+
+  auto source_id = GenerateExpression(source);
+  if (source_id == 0) {
+    return 0;
+  }
+
+  // The access chain results in a pointer, so wrap the return type.
+  ast::type::PointerType ptr(expr->result_type(), ast::StorageClass::kFunction);
+  auto type_id = GenerateTypeIfNeeded(&ptr);
+  if (type_id == 0) {
+    return 0;
+  }
+
+  idx_list.insert(idx_list.begin(), Operand::Int(source_id));
+  idx_list.insert(idx_list.begin(), result);
+  idx_list.insert(idx_list.begin(), Operand::Int(type_id));
+  push_function_inst(spv::Op::OpAccessChain, idx_list);
+
+  return result_id;
+}
+
 uint32_t Builder::GenerateIdentifierExpression(
     ast::IdentifierExpression* expr) {
   uint32_t val = 0;

src/writer/spirv/builder.h

@@ -177,6 +177,10 @@ class Builder {
   /// @param var the variable to generate
   /// @returns true if the variable is emited.
   bool GenerateGlobalVariable(ast::Variable* var);
+  /// Generates an array accessor expression
+  /// @param expr the expresssion to generate
+  /// @returns the id of the expression or 0 on failure
+  uint32_t GenerateAccessorExpression(ast::Expression* expr);
   /// Generates an identifier expression
   /// @param expr the expresssion to generate
   /// @returns the id of the expression or 0 on failure

src/writer/spirv/builder_accessor_expression_test.cc

@@ -0,0 +1,131 @@
+// Copyright 2020 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 "gtest/gtest.h"
+#include "src/ast/array_accessor_expression.h"
+#include "src/ast/identifier_expression.h"
+#include "src/ast/int_literal.h"
+#include "src/ast/module.h"
+#include "src/ast/scalar_constructor_expression.h"
+#include "src/ast/type/array_type.h"
+#include "src/ast/type/f32_type.h"
+#include "src/ast/type/i32_type.h"
+#include "src/ast/type/vector_type.h"
+#include "src/ast/variable.h"
+#include "src/context.h"
+#include "src/type_determiner.h"
+#include "src/writer/spirv/builder.h"
+#include "src/writer/spirv/spv_dump.h"
+
+namespace tint {
+namespace writer {
+namespace spirv {
+namespace {
+
+using BuilderTest = testing::Test;
+
+TEST_F(BuilderTest, ArrayAccessor) {
+  ast::type::I32Type i32;
+  ast::type::F32Type f32;
+  ast::type::VectorType vec3(&f32, 3);
+
+  ast::Variable var("ary", ast::StorageClass::kFunction, &vec3);
+
+  auto ary = std::make_unique<ast::IdentifierExpression>("ary");
+  auto idx_expr = std::make_unique<ast::ScalarConstructorExpression>(
+      std::make_unique<ast::IntLiteral>(&i32, 1));
+
+  ast::ArrayAccessorExpression expr(std::move(ary), std::move(idx_expr));
+
+  Context ctx;
+  ast::Module mod;
+  TypeDeterminer td(&ctx, &mod);
+  td.RegisterVariableForTesting(&var);
+  ASSERT_TRUE(td.DetermineResultType(&expr)) << td.error();
+
+  Builder b(&mod);
+  b.push_function(Function{});
+  ASSERT_TRUE(b.GenerateFunctionVariable(&var)) << b.error();
+
+  EXPECT_EQ(b.GenerateAccessorExpression(&expr), 5u);
+
+  EXPECT_EQ(DumpInstructions(b.types()), R"(%4 = OpTypeFloat 32
+%3 = OpTypeVector %4 3
+%2 = OpTypePointer Function %3
+%6 = OpTypeInt 32 1
+%7 = OpConstant %6 1
+%8 = OpTypePointer Function %4
+)");
+  EXPECT_EQ(DumpInstructions(b.functions()[0].variables()),
+            R"(%1 = OpVariable %2 Function
+)");
+  EXPECT_EQ(DumpInstructions(b.functions()[0].instructions()),
+            R"(%5 = OpAccessChain %8 %1 %7
+)");
+}
+
+TEST_F(BuilderTest, ArrayAccessor_MultiLevel) {
+  ast::type::I32Type i32;
+  ast::type::F32Type f32;
+  ast::type::VectorType vec3(&f32, 3);
+  ast::type::ArrayType ary4(&vec3, 4);
+
+  // ary = array<vec3<f32>, 4>
+  // ary[3][2];
+
+  ast::Variable var("ary", ast::StorageClass::kFunction, &ary4);
+
+  ast::ArrayAccessorExpression expr(
+      std::make_unique<ast::ArrayAccessorExpression>(
+          std::make_unique<ast::IdentifierExpression>("ary"),
+          std::make_unique<ast::ScalarConstructorExpression>(
+              std::make_unique<ast::IntLiteral>(&i32, 3))),
+      std::make_unique<ast::ScalarConstructorExpression>(
+          std::make_unique<ast::IntLiteral>(&i32, 2)));
+
+  Context ctx;
+  ast::Module mod;
+  TypeDeterminer td(&ctx, &mod);
+  td.RegisterVariableForTesting(&var);
+  ASSERT_TRUE(td.DetermineResultType(&expr)) << td.error();
+
+  Builder b(&mod);
+  b.push_function(Function{});
+  ASSERT_TRUE(b.GenerateFunctionVariable(&var)) << b.error();
+
+  EXPECT_EQ(b.GenerateAccessorExpression(&expr), 8u);
+
+  EXPECT_EQ(DumpInstructions(b.types()), R"(%5 = OpTypeFloat 32
+%4 = OpTypeVector %5 3
+%6 = OpTypeInt 32 0
+%7 = OpConstant %6 4
+%3 = OpTypeArray %4 %7
+%2 = OpTypePointer Function %3
+%9 = OpTypeInt 32 1
+%10 = OpConstant %9 2
+%11 = OpConstant %9 3
+%12 = OpTypePointer Function %5
+)");
+  EXPECT_EQ(DumpInstructions(b.functions()[0].variables()),
+            R"(%1 = OpVariable %2 Function
+)");
+  EXPECT_EQ(DumpInstructions(b.functions()[0].instructions()),
+            R"(%8 = OpAccessChain %12 %1 %11 %10
+)");
+}
+
+}  // namespace
+}  // namespace spirv
+}  // namespace writer
+}  // namespace tint