[msl-writer] Handle emitting user function calls.

This CL adds support for calling user defined functions from the MSL
backend. Intrinsics and imports are not handled yet.

Bug: tint:8
Change-Id: I45c3078d014ab89cc0eec76dd626759077e1a890
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/24763
Reviewed-by: David Neto <dneto@google.com>

BUILD.gn

@@ -892,6 +892,7 @@ source_set("tint_unittests_msl_writer_src") {
     "src/writer/msl/generator_impl_assign_test.cc",
     "src/writer/msl/generator_impl_binary_test.cc",
     "src/writer/msl/generator_impl_break_test.cc",
+    "src/writer/msl/generator_impl_call_test.cc",
     "src/writer/msl/generator_impl_case_test.cc",
     "src/writer/msl/generator_impl_cast_test.cc",
     "src/writer/msl/generator_impl_constructor_test.cc",

src/CMakeLists.txt

@@ -500,6 +500,7 @@ if(${TINT_BUILD_MSL_WRITER})
     writer/msl/generator_impl_assign_test.cc
     writer/msl/generator_impl_binary_test.cc
     writer/msl/generator_impl_break_test.cc
+    writer/msl/generator_impl_call_test.cc
     writer/msl/generator_impl_case_test.cc
     writer/msl/generator_impl_cast_test.cc
     writer/msl/generator_impl_constructor_test.cc

src/writer/msl/generator_impl.cc

@@ -20,6 +20,7 @@
 #include "src/ast/binary_expression.h"
 #include "src/ast/bool_literal.h"
 #include "src/ast/break_statement.h"
+#include "src/ast/call_expression.h"
 #include "src/ast/case_statement.h"
 #include "src/ast/cast_expression.h"
 #include "src/ast/continue_statement.h"
@@ -29,6 +30,7 @@
 #include "src/ast/function.h"
 #include "src/ast/identifier_expression.h"
 #include "src/ast/if_statement.h"
+#include "src/ast/intrinsic.h"
 #include "src/ast/location_decoration.h"
 #include "src/ast/loop_statement.h"
 #include "src/ast/member_accessor_expression.h"
@@ -266,6 +268,48 @@ bool GeneratorImpl::EmitBreak(ast::BreakStatement*) {
   return true;
 }
 
+bool GeneratorImpl::EmitCall(ast::CallExpression* expr) {
+  if (!expr->func()->IsIdentifier()) {
+    error_ = "invalid function name";
+    return 0;
+  }
+
+  auto* ident = expr->func()->AsIdentifier();
+
+  if (!ident->has_path() && ast::intrinsic::IsIntrinsic(ident->name())) {
+    // TODO(dsinclair): Generate intrinsic
+    error_ = "intrinsics not generated yet";
+    return false;
+  }
+
+  if (!ident->has_path()) {
+    if (!EmitExpression(expr->func())) {
+      return false;
+    }
+    out_ << "(";
+
+    bool first = true;
+    const auto& params = expr->params();
+    for (const auto& param : params) {
+      if (!first) {
+        out_ << ", ";
+      }
+      first = false;
+
+      if (!EmitExpression(param.get())) {
+        return false;
+      }
+    }
+
+    out_ << ")";
+  } else {
+    // TODO(dsinclair): Handle imported function
+    error_ = "imported calls not handled yet";
+    return false;
+  }
+  return true;
+}
+
 bool GeneratorImpl::EmitCase(ast::CaseStatement* stmt) {
   make_indent();
 
@@ -528,6 +572,9 @@ bool GeneratorImpl::EmitExpression(ast::Expression* expr) {
   if (expr->IsBinary()) {
     return EmitBinary(expr->AsBinary());
   }
+  if (expr->IsCall()) {
+    return EmitCall(expr->AsCall());
+  }
   if (expr->IsCast()) {
     return EmitCast(expr->AsCast());
   }

src/writer/msl/generator_impl.h

@@ -66,6 +66,10 @@ class GeneratorImpl : public TextGenerator {
   /// @param stmt the statement to emit
   /// @returns true if the statement was emitted successfully
   bool EmitBreak(ast::BreakStatement* stmt);
+  /// Handles generating a call expression
+  /// @param expr the call expression
+  /// @returns true if the call expression is emitted
+  bool EmitCall(ast::CallExpression* expr);
   /// Handles a case statement
   /// @param stmt the statement
   /// @returns true if the statment was emitted successfully

src/writer/msl/generator_impl_call_test.cc

@@ -0,0 +1,53 @@
+// 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 <memory>
+
+#include "gtest/gtest.h"
+#include "src/ast/call_expression.h"
+#include "src/ast/identifier_expression.h"
+#include "src/writer/msl/generator_impl.h"
+
+namespace tint {
+namespace writer {
+namespace msl {
+namespace {
+
+using MslGeneratorImplTest = testing::Test;
+
+TEST_F(MslGeneratorImplTest, EmitExpression_Call_WithoutParams) {
+  auto id = std::make_unique<ast::IdentifierExpression>("my_func");
+  ast::CallExpression call(std::move(id), {});
+
+  GeneratorImpl g;
+  ASSERT_TRUE(g.EmitExpression(&call)) << g.error();
+  EXPECT_EQ(g.result(), "my_func()");
+}
+
+TEST_F(MslGeneratorImplTest, EmitExpression_Call_WithParams) {
+  auto id = std::make_unique<ast::IdentifierExpression>("my_func");
+  ast::ExpressionList params;
+  params.push_back(std::make_unique<ast::IdentifierExpression>("param1"));
+  params.push_back(std::make_unique<ast::IdentifierExpression>("param2"));
+  ast::CallExpression call(std::move(id), std::move(params));
+
+  GeneratorImpl g;
+  ASSERT_TRUE(g.EmitExpression(&call)) << g.error();
+  EXPECT_EQ(g.result(), "my_func(param1, param2)");
+}
+
+}  // namespace
+}  // namespace msl
+}  // namespace writer
+}  // namespace tint