Generate entry point instructions in SPIR-V writer.

This CL updates the SPIR-V generator to create entry point instructions.

Bug: tint:5
Change-Id: I04394bd508c0871ae9563cc811b4e49e42c2bb3a
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/17322
Reviewed-by: David Neto <dneto@google.com>

src/CMakeLists.txt

@@ -399,6 +399,7 @@ if(${TINT_BUILD_SPV_WRITER})
   list(APPEND TINT_TEST_SRCS
     writer/spirv/binary_writer_test.cc
     writer/spirv/builder_test.cc
+    writer/spirv/builder_test_entry_point_test.cc
     writer/spirv/instruction_test.cc
     writer/spirv/operand_test.cc
   )

src/writer/spirv/builder.cc

@@ -29,6 +29,26 @@ uint32_t size_of(const std::vector<Instruction>& instructions) {
   return size;
 }
 
+uint32_t pipeline_stage_to_execution_model(ast::PipelineStage stage) {
+  SpvExecutionModel model = SpvExecutionModelVertex;
+
+  switch (stage) {
+    case ast::PipelineStage::kFragment:
+      model = SpvExecutionModelFragment;
+      break;
+    case ast::PipelineStage::kVertex:
+      model = SpvExecutionModelVertex;
+      break;
+    case ast::PipelineStage::kCompute:
+      model = SpvExecutionModelGLCompute;
+      break;
+    case ast::PipelineStage::kNone:
+      model = SpvExecutionModelMax;
+      break;
+  }
+  return model;
+}
+
 }  // namespace
 
 Builder::Builder() = default;
@@ -47,6 +67,13 @@ bool Builder::Build(const ast::Module& m) {
   push_preamble(spv::Op::OpMemoryModel,
                 {Operand::Int(SpvAddressingModelLogical),
                  Operand::Int(SpvMemoryModelVulkanKHR)});
+
+  for (const auto& ep : m.entry_points()) {
+    if (!GenerateEntryPoint(ep.get())) {
+      return false;
+    }
+  }
+
   return true;
 }
 
@@ -85,6 +112,28 @@ void Builder::iterate(std::function<void(const Instruction&)> cb) const {
   }
 }
 
+bool Builder::GenerateEntryPoint(ast::EntryPoint* ep) {
+  auto name = ep->name();
+  if (name.empty()) {
+    name = ep->function_name();
+  }
+
+  auto id = id_for_func_name(ep->function_name());
+  if (id == 0) {
+    return false;
+  }
+
+  auto stage = pipeline_stage_to_execution_model(ep->stage());
+  if (stage == SpvExecutionModelMax) {
+    return false;
+  }
+
+  push_preamble(spv::Op::OpEntryPoint,
+                {Operand::Int(stage), Operand::Int(id), Operand::String(name)});
+
+  return true;
+}
+
 void Builder::GenerateImport(ast::Import* imp) {
   auto op = result_op();
   auto id = op.to_i();

src/writer/spirv/builder.h

@@ -52,6 +52,22 @@ class Builder {
     return id;
   }
 
+  /// Sets the id for a given function name
+  /// @param name the name to set
+  /// @param id the id to set
+  void set_func_name_to_id(const std::string& name, uint32_t id) {
+    func_name_to_id_[name] = id;
+  }
+
+  /// Retrives the id for the given function name
+  /// @returns the id for the given name or 0 on failure
+  uint32_t id_for_func_name(const std::string& name) {
+    if (func_name_to_id_.count(name) == 0) {
+      return 0;
+    }
+    return func_name_to_id_[name];
+  }
+
   /// Iterates over all the instructions in the correct order and calls the
   /// given callback
   /// @param cb the callback to execute
@@ -98,6 +114,10 @@ class Builder {
   /// @returns the annotations
   const std::vector<Instruction>& annot() const { return annotations_; }
 
+  /// Generates an entry point instruction
+  /// @param ep the entry point
+  /// @returns true if the instruction was generated, false otherwise
+  bool GenerateEntryPoint(ast::EntryPoint* ep);
   /// Generates an import instruction
   /// @param imp the import
   void GenerateImport(ast::Import* imp);
@@ -113,6 +133,7 @@ class Builder {
   std::vector<Instruction> annotations_;
 
   std::unordered_map<std::string, uint32_t> import_name_to_id_;
+  std::unordered_map<std::string, uint32_t> func_name_to_id_;
 };
 
 }  // namespace spirv

src/writer/spirv/builder_test_entry_point_test.cc

@@ -0,0 +1,111 @@
+// 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 <string>
+
+#include "gtest/gtest.h"
+#include "spirv/unified1/spirv.h"
+#include "spirv/unified1/spirv.hpp11"
+#include "src/ast/entry_point.h"
+#include "src/ast/pipeline_stage.h"
+#include "src/writer/spirv/builder.h"
+
+namespace tint {
+namespace writer {
+namespace spirv {
+
+using BuilderTest = testing::Test;
+
+TEST_F(BuilderTest, EntryPoint) {
+  ast::EntryPoint ep(ast::PipelineStage::kFragment, "main", "frag_main");
+
+  Builder b;
+  b.set_func_name_to_id("frag_main", 2);
+  ASSERT_TRUE(b.GenerateEntryPoint(&ep));
+
+  auto preamble = b.preamble();
+  ASSERT_EQ(preamble.size(), 1);
+  EXPECT_EQ(preamble[0].opcode(), spv::Op::OpEntryPoint);
+
+  ASSERT_TRUE(preamble[0].operands().size() >= 3);
+  EXPECT_EQ(preamble[0].operands()[0].to_i(), SpvExecutionModelFragment);
+  EXPECT_EQ(preamble[0].operands()[1].to_i(), 2);
+  EXPECT_EQ(preamble[0].operands()[2].to_s(), "main");
+}
+
+TEST_F(BuilderTest, EntryPoint_WithoutName) {
+  ast::EntryPoint ep(ast::PipelineStage::kCompute, "", "compute_main");
+
+  Builder b;
+  b.set_func_name_to_id("compute_main", 3);
+  ASSERT_TRUE(b.GenerateEntryPoint(&ep));
+
+  auto preamble = b.preamble();
+  ASSERT_EQ(preamble.size(), 1);
+  EXPECT_EQ(preamble[0].opcode(), spv::Op::OpEntryPoint);
+
+  ASSERT_TRUE(preamble[0].operands().size() >= 3);
+  EXPECT_EQ(preamble[0].operands()[0].to_i(), SpvExecutionModelGLCompute);
+  EXPECT_EQ(preamble[0].operands()[1].to_i(), 3);
+  EXPECT_EQ(preamble[0].operands()[2].to_s(), "compute_main");
+}
+
+TEST_F(BuilderTest, EntryPoint_BadFunction) {
+  ast::EntryPoint ep(ast::PipelineStage::kFragment, "main", "frag_main");
+
+  Builder b;
+  EXPECT_FALSE(b.GenerateEntryPoint(&ep));
+}
+
+struct EntryPointStageData {
+  ast::PipelineStage stage;
+  SpvExecutionModel model;
+};
+inline std::ostream& operator<<(std::ostream& out, EntryPointStageData data) {
+  out << data.stage;
+  return out;
+}
+using EntryPointStageTest = testing::TestWithParam<EntryPointStageData>;
+TEST_P(EntryPointStageTest, Emit) {
+  auto params = GetParam();
+
+  ast::EntryPoint ep(params.stage, "", "main");
+
+  Builder b;
+  b.set_func_name_to_id("main", 3);
+  ASSERT_TRUE(b.GenerateEntryPoint(&ep));
+
+  auto preamble = b.preamble();
+  ASSERT_EQ(preamble.size(), 1);
+  EXPECT_EQ(preamble[0].opcode(), spv::Op::OpEntryPoint);
+
+  ASSERT_TRUE(preamble[0].operands().size() >= 3);
+  EXPECT_EQ(preamble[0].operands()[0].to_i(), params.model);
+}
+INSTANTIATE_TEST_SUITE_P(
+    BuilderTest,
+    EntryPointStageTest,
+    testing::Values(EntryPointStageData{ast::PipelineStage::kVertex,
+                                        SpvExecutionModelVertex},
+                    EntryPointStageData{ast::PipelineStage::kFragment,
+                                        SpvExecutionModelFragment},
+                    EntryPointStageData{ast::PipelineStage::kCompute,
+                                        SpvExecutionModelGLCompute}));
+
+// TODO(http://crbug.com/tint/28)
+TEST_F(BuilderTest, DISABLED_EntryPoint_WithInterfaceIds) {}
+
+}  // namespace spirv
+}  // namespace writer
+}  // namespace tint