test/reduce/simple_conditional_branch_to_branch_test.cpp

// Copyright (c) 2019 Google LLC
//
// 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 "source/reduce/simple_conditional_branch_to_branch_opportunity_finder.h"

#include "source/opt/build_module.h"
#include "source/reduce/reduction_opportunity.h"
#include "source/reduce/reduction_pass.h"
#include "test/reduce/reduce_test_util.h"

namespace spvtools {
namespace reduce {
namespace {

const spv_target_env kEnv = SPV_ENV_UNIVERSAL_1_3;

TEST(SimpleConditionalBranchToBranchTest, Diamond) {
  // A test with the following structure.
  //
  // selection header
  // OpBranchConditional
  //  ||
  //  b        b
  //  |        |
  //  selection merge
  //
  // The conditional branch cannot be simplified because selection headers
  // cannot end with OpBranch.

  std::string shader = R"(
               OpCapability Shader
          %1 = OpExtInstImport "GLSL.std.450"
               OpMemoryModel Logical GLSL450
               OpEntryPoint Fragment %2 "main"
               OpExecutionMode %2 OriginUpperLeft
               OpSource ESSL 310
               OpName %2 "main"
          %3 = OpTypeVoid
          %4 = OpTypeFunction %3
          %5 = OpTypeInt 32 1
          %6 = OpTypePointer Function %5
          %7 = OpTypeBool
          %8 = OpConstantTrue %7
          %2 = OpFunction %3 None %4
          %9 = OpLabel
               OpBranch %10
         %10 = OpLabel
               OpSelectionMerge %11 None
               OpBranchConditional %8 %12 %12
         %12 = OpLabel
               OpBranch %11
         %13 = OpLabel
               OpBranch %11
         %11 = OpLabel
               OpReturn
               OpFunctionEnd

    )";

  auto context = BuildModule(kEnv, nullptr, shader, kReduceAssembleOption);

  CheckValid(kEnv, context.get());

  auto ops = SimpleConditionalBranchToBranchOpportunityFinder()
                 .GetAvailableOpportunities(context.get(), 0);

  ASSERT_EQ(0, ops.size());
}

TEST(SimpleConditionalBranchToBranchTest, DiamondNoSelection) {
  // A test with the following structure.
  //
  // OpBranchConditional
  //  ||
  //  b  b
  //  | /
  //  b
  //
  // The conditional branch can be simplified.

  std::string shader = R"(
               OpCapability Shader
          %1 = OpExtInstImport "GLSL.std.450"
               OpMemoryModel Logical GLSL450
               OpEntryPoint Fragment %2 "main"
               OpExecutionMode %2 OriginUpperLeft
               OpSource ESSL 310
               OpName %2 "main"
          %3 = OpTypeVoid
          %4 = OpTypeFunction %3
          %5 = OpTypeInt 32 1
          %6 = OpTypePointer Function %5
          %7 = OpTypeBool
          %8 = OpConstantTrue %7
          %2 = OpFunction %3 None %4
          %9 = OpLabel
               OpBranch %10
         %10 = OpLabel
               OpBranchConditional %8 %12 %12
         %12 = OpLabel
               OpBranch %11
         %13 = OpLabel
               OpBranch %11
         %11 = OpLabel
               OpReturn
               OpFunctionEnd
    )";

  auto context = BuildModule(kEnv, nullptr, shader, kReduceAssembleOption);

  CheckValid(kEnv, context.get());

  auto ops = SimpleConditionalBranchToBranchOpportunityFinder()
                 .GetAvailableOpportunities(context.get(), 0);

  ASSERT_EQ(1, ops.size());

  ASSERT_TRUE(ops[0]->PreconditionHolds());
  ops[0]->TryToApply();
  CheckValid(kEnv, context.get());

  std::string after = R"(
               OpCapability Shader
          %1 = OpExtInstImport "GLSL.std.450"
               OpMemoryModel Logical GLSL450
               OpEntryPoint Fragment %2 "main"
               OpExecutionMode %2 OriginUpperLeft
               OpSource ESSL 310
               OpName %2 "main"
          %3 = OpTypeVoid
          %4 = OpTypeFunction %3
          %5 = OpTypeInt 32 1
          %6 = OpTypePointer Function %5
          %7 = OpTypeBool
          %8 = OpConstantTrue %7
          %2 = OpFunction %3 None %4
          %9 = OpLabel
               OpBranch %10
         %10 = OpLabel
               OpBranch %12
         %12 = OpLabel
               OpBranch %11
         %13 = OpLabel
               OpBranch %11
         %11 = OpLabel
               OpReturn
               OpFunctionEnd
    )";

  CheckEqual(kEnv, after, context.get());

  ops = SimpleConditionalBranchToBranchOpportunityFinder()
            .GetAvailableOpportunities(context.get(), 0);
  ASSERT_EQ(0, ops.size());
}

TEST(SimpleConditionalBranchToBranchTest, ConditionalBranchesButNotSimple) {
  // A test with the following structure.
  //
  // selection header
  // OpBranchConditional
  //  |        |
  //  b        OpBranchConditional
  //  |        |   |
  //  |        b   |
  //  |        |   |
  //  selection merge
  //
  // None of the conditional branches can be simplified; the first is not simple
  // AND part of a selection header; the second is just not simple (where
  // "simple" means it only has one target).

  std::string shader = R"(
               OpCapability Shader
          %1 = OpExtInstImport "GLSL.std.450"
               OpMemoryModel Logical GLSL450
               OpEntryPoint Fragment %2 "main"
               OpExecutionMode %2 OriginUpperLeft
               OpSource ESSL 310
               OpName %2 "main"
          %3 = OpTypeVoid
          %4 = OpTypeFunction %3
          %5 = OpTypeInt 32 1
          %6 = OpTypePointer Function %5
          %7 = OpTypeBool
          %8 = OpConstantTrue %7
          %2 = OpFunction %3 None %4
          %9 = OpLabel
               OpBranch %10
         %10 = OpLabel
               OpSelectionMerge %11 None
               OpBranchConditional %8 %12 %13
         %12 = OpLabel
               OpBranch %11
         %13 = OpLabel
               OpBranchConditional %8 %14 %11
         %14 = OpLabel
               OpBranch %11
         %11 = OpLabel
               OpReturn
               OpFunctionEnd
    )";

  auto context = BuildModule(kEnv, nullptr, shader, kReduceAssembleOption);

  CheckValid(kEnv, context.get());

  auto ops = SimpleConditionalBranchToBranchOpportunityFinder()
                 .GetAvailableOpportunities(context.get(), 0);

  ASSERT_EQ(0, ops.size());
}

TEST(SimpleConditionalBranchToBranchTest, SimplifyBackEdge) {
  // A test with the following structure. The loop has a continue construct that
  // ends with OpBranchConditional. The OpBranchConditional can be simplified.
  //
  // loop header
  //   |
  //   loop continue target and back-edge block
  //   OpBranchConditional
  //                  ||
  // loop merge       (to loop header^)

  std::string shader = R"(
               OpCapability Shader
          %1 = OpExtInstImport "GLSL.std.450"
               OpMemoryModel Logical GLSL450
               OpEntryPoint Fragment %2 "main"
               OpExecutionMode %2 OriginUpperLeft
               OpSource ESSL 310
               OpName %2 "main"
          %3 = OpTypeVoid
          %4 = OpTypeFunction %3
          %5 = OpTypeInt 32 1
          %6 = OpTypePointer Function %5
          %7 = OpTypeBool
          %8 = OpConstantTrue %7
          %2 = OpFunction %3 None %4
          %9 = OpLabel
               OpBranch %10
         %10 = OpLabel
               OpLoopMerge %11 %12 None
               OpBranch %12
         %12 = OpLabel
               OpBranchConditional %8 %10 %10
         %11 = OpLabel
               OpReturn
               OpFunctionEnd
    )";

  const auto context =
      BuildModule(kEnv, nullptr, shader, kReduceAssembleOption);

  CheckValid(kEnv, context.get());

  auto ops = SimpleConditionalBranchToBranchOpportunityFinder()
                 .GetAvailableOpportunities(context.get(), 0);

  ASSERT_EQ(1, ops.size());

  ASSERT_TRUE(ops[0]->PreconditionHolds());
  ops[0]->TryToApply();
  CheckValid(kEnv, context.get());

  std::string after = R"(
               OpCapability Shader
          %1 = OpExtInstImport "GLSL.std.450"
               OpMemoryModel Logical GLSL450
               OpEntryPoint Fragment %2 "main"
               OpExecutionMode %2 OriginUpperLeft
               OpSource ESSL 310
               OpName %2 "main"
          %3 = OpTypeVoid
          %4 = OpTypeFunction %3
          %5 = OpTypeInt 32 1
          %6 = OpTypePointer Function %5
          %7 = OpTypeBool
          %8 = OpConstantTrue %7
          %2 = OpFunction %3 None %4
          %9 = OpLabel
               OpBranch %10
         %10 = OpLabel
               OpLoopMerge %11 %12 None
               OpBranch %12
         %12 = OpLabel
               OpBranch %10
         %11 = OpLabel
               OpReturn
               OpFunctionEnd
    )";
  CheckEqual(kEnv, after, context.get());

  ops = SimpleConditionalBranchToBranchOpportunityFinder()
            .GetAvailableOpportunities(context.get(), 0);
  ASSERT_EQ(0, ops.size());
}

TEST(SimpleConditionalBranchToBranchTest,
     DontRemoveBackEdgeCombinedHeaderContinue) {
  // A test with the following structure.
  //
  // loop header and continue target and back-edge block
  //   OpBranchConditional
  //                  ||
  // loop merge       (to loop header^)
  //
  // The conditional branch can be simplified.

  std::string shader = R"(
               OpCapability Shader
          %1 = OpExtInstImport "GLSL.std.450"
               OpMemoryModel Logical GLSL450
               OpEntryPoint Fragment %2 "main"
               OpExecutionMode %2 OriginUpperLeft
               OpSource ESSL 310
               OpName %2 "main"
          %3 = OpTypeVoid
          %4 = OpTypeFunction %3
          %5 = OpTypeInt 32 1
          %6 = OpTypePointer Function %5
          %7 = OpTypeBool
          %8 = OpConstantTrue %7
          %2 = OpFunction %3 None %4
          %9 = OpLabel
               OpBranch %10
         %10 = OpLabel
               OpLoopMerge %11 %10 None
               OpBranchConditional %8 %10 %10
         %11 = OpLabel
               OpReturn
               OpFunctionEnd
    )";

  const auto context =
      BuildModule(kEnv, nullptr, shader, kReduceAssembleOption);

  CheckValid(kEnv, context.get());

  auto ops = SimpleConditionalBranchToBranchOpportunityFinder()
                 .GetAvailableOpportunities(context.get(), 0);

  ASSERT_EQ(1, ops.size());

  ASSERT_TRUE(ops[0]->PreconditionHolds());
  ops[0]->TryToApply();
  CheckValid(kEnv, context.get());

  std::string after = R"(
          OpCapability Shader
          %1 = OpExtInstImport "GLSL.std.450"
               OpMemoryModel Logical GLSL450
               OpEntryPoint Fragment %2 "main"
               OpExecutionMode %2 OriginUpperLeft
               OpSource ESSL 310
               OpName %2 "main"
          %3 = OpTypeVoid
          %4 = OpTypeFunction %3
          %5 = OpTypeInt 32 1
          %6 = OpTypePointer Function %5
          %7 = OpTypeBool
          %8 = OpConstantTrue %7
          %2 = OpFunction %3 None %4
          %9 = OpLabel
               OpBranch %10
         %10 = OpLabel
               OpLoopMerge %11 %10 None
               OpBranch %10
         %11 = OpLabel
               OpReturn
               OpFunctionEnd
    )";
  CheckEqual(kEnv, after, context.get());

  ops = SimpleConditionalBranchToBranchOpportunityFinder()
            .GetAvailableOpportunities(context.get(), 0);
  ASSERT_EQ(0, ops.size());
}

TEST(SimpleConditionalBranchToBranchTest, BackEdgeUnreachable) {
  // A test with the following structure. I.e. a loop with an unreachable
  // continue construct that ends with OpBranchConditional.
  //
  // loop header
  //   |
  //   | loop continue target (unreachable)
  //   |      |
  //   | back-edge block (unreachable)
  //   | OpBranchConditional
  //   |               ||
  // loop merge       (to loop header^)
  //
  // The conditional branch can be simplified.

  std::string shader = R"(
               OpCapability Shader
          %1 = OpExtInstImport "GLSL.std.450"
               OpMemoryModel Logical GLSL450
               OpEntryPoint Fragment %2 "main"
               OpExecutionMode %2 OriginUpperLeft
               OpSource ESSL 310
               OpName %2 "main"
          %3 = OpTypeVoid
          %4 = OpTypeFunction %3
          %5 = OpTypeInt 32 1
          %6 = OpTypePointer Function %5
          %7 = OpTypeBool
          %8 = OpConstantTrue %7
          %2 = OpFunction %3 None %4
          %9 = OpLabel
               OpBranch %10
         %10 = OpLabel
               OpLoopMerge %11 %12 None
               OpBranch %11
         %12 = OpLabel
               OpBranch %13
         %13 = OpLabel
               OpBranchConditional %8 %10 %10
         %11 = OpLabel
               OpReturn
               OpFunctionEnd
    )";

  const auto context =
      BuildModule(kEnv, nullptr, shader, kReduceAssembleOption);

  CheckValid(kEnv, context.get());

  auto ops = SimpleConditionalBranchToBranchOpportunityFinder()
                 .GetAvailableOpportunities(context.get(), 0);

  ASSERT_EQ(1, ops.size());

  ASSERT_TRUE(ops[0]->PreconditionHolds());
  ops[0]->TryToApply();
  CheckValid(kEnv, context.get());

  std::string after = R"(
               OpCapability Shader
          %1 = OpExtInstImport "GLSL.std.450"
               OpMemoryModel Logical GLSL450
               OpEntryPoint Fragment %2 "main"
               OpExecutionMode %2 OriginUpperLeft
               OpSource ESSL 310
               OpName %2 "main"
          %3 = OpTypeVoid
          %4 = OpTypeFunction %3
          %5 = OpTypeInt 32 1
          %6 = OpTypePointer Function %5
          %7 = OpTypeBool
          %8 = OpConstantTrue %7
          %2 = OpFunction %3 None %4
          %9 = OpLabel
               OpBranch %10
         %10 = OpLabel
               OpLoopMerge %11 %12 None
               OpBranch %11
         %12 = OpLabel
               OpBranch %13
         %13 = OpLabel
               OpBranch %10
         %11 = OpLabel
               OpReturn
               OpFunctionEnd
    )";
  CheckEqual(kEnv, after, context.get());

  ops = SimpleConditionalBranchToBranchOpportunityFinder()
            .GetAvailableOpportunities(context.get(), 0);
  ASSERT_EQ(0, ops.size());
}

}  // namespace
}  // namespace reduce
}  // namespace spvtools