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[CodeGen] Expose the extensibility of PassConfig to plugins (llvm#139059)
This PR exposes the backend pass config to plugins via a callback. Plugin authors can register a callback that is being triggered before the target backend adds their passes to the pipeline. In the callback they then get access to the `TargetMachine`, the `PassManager`, and the `TargetPassConfig`. This allows plugins to call `TargetPassConfig::insertPass`, which is honored in the subsequent `addPass` of the main backend. We implemented this using the legacy pass manager since backends still use it as the default.
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‎llvm/docs/WritingAnLLVMPass.rst

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@@ -442,6 +442,28 @@ in certain circumstances (such as calling the ``Pass::dump()`` from a
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debugger), so it should only be used to enhance debug output, it should not be
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depended on.
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Scheduling a MachineFunctionPass
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Backends create a ``TargetPassConfig`` and use ``addPass`` to schedule
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``MachineFunctionPass``\ es. External plugins can register a callback to modify
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and insert additional passes:
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.. code-block:: c++
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RegisterTargetPassConfigCallback X{[](auto &TM, auto &PM, auto *TPC) {
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TPC->insertPass(/* ... */);
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TPC->substitutePass(/* ... */);
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}};
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Note that passes still have to be registered:
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.. code-block:: c++
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__attribute__((constructor)) static void initCodeGenPlugin() {
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initializeExamplePass(*PassRegistry::getPassRegistry());
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}
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.. _writing-an-llvm-pass-interaction:
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Specifying interactions between passes

‎llvm/include/llvm/Target/RegisterTargetPassConfigCallback.h

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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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///
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/// This file contains the registry for PassConfigCallbacks that enable changes
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/// to the TargetPassConfig during the initialization of TargetMachine.
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///
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TARGET_REGISTERTARGETPASSCONFIGCALLBACK_H
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#define LLVM_TARGET_REGISTERTARGETPASSCONFIGCALLBACK_H
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#include "TargetMachine.h"
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namespace llvm {
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using PassConfigCallback =
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std::function<void(TargetMachine &, PassManagerBase &, TargetPassConfig *)>;
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class RegisterTargetPassConfigCallback {
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public:
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PassConfigCallback Callback;
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explicit RegisterTargetPassConfigCallback(PassConfigCallback &&C);
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~RegisterTargetPassConfigCallback();
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};
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void invokeGlobalTargetPassConfigCallbacks(TargetMachine &TM,
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PassManagerBase &PM,
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TargetPassConfig *PassConfig);
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} // namespace llvm
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#endif // LLVM_TARGET_REGISTERTARGETPASSCONFIGCALLBACK_H

‎llvm/lib/CodeGen/CodeGenTargetMachineImpl.cpp

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#include "llvm/MC/TargetRegistry.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/FormattedStream.h"
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#include "llvm/Target/RegisterTargetPassConfigCallback.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetOptions.h"
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using namespace llvm;
@@ -122,6 +123,7 @@ addPassesToGenerateCode(CodeGenTargetMachineImpl &TM, PassManagerBase &PM,
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PassConfig->setDisableVerify(DisableVerify);
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PM.add(PassConfig);
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PM.add(&MMIWP);
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invokeGlobalTargetPassConfigCallbacks(TM, PM, PassConfig);
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if (PassConfig->addISelPasses())
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return nullptr;

‎llvm/lib/Target/CMakeLists.txt

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@@ -3,6 +3,7 @@ list(APPEND LLVM_COMMON_DEPENDS intrinsics_gen)
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list(APPEND LLVM_TABLEGEN_FLAGS -I ${LLVM_MAIN_SRC_DIR}/lib/Target)
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add_llvm_component_library(LLVMTarget
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RegisterTargetPassConfigCallback.cpp
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Target.cpp
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TargetLoweringObjectFile.cpp
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TargetMachine.cpp

‎llvm/lib/Target/RegisterTargetPassConfigCallback.cpp

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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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///
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/// This file contains the registry for PassConfigCallbacks that enable changes
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/// to the TargetPassConfig during the initialization of TargetMachine.
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///
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//===----------------------------------------------------------------------===//
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#include "llvm/Target/RegisterTargetPassConfigCallback.h"
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namespace llvm {
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// TargetPassConfig callbacks
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static SmallVector<RegisterTargetPassConfigCallback *, 1>
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TargetPassConfigCallbacks{};
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void invokeGlobalTargetPassConfigCallbacks(TargetMachine &TM,
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PassManagerBase &PM,
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TargetPassConfig *PassConfig) {
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for (const RegisterTargetPassConfigCallback *Reg : TargetPassConfigCallbacks)
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Reg->Callback(TM, PM, PassConfig);
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}
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RegisterTargetPassConfigCallback::RegisterTargetPassConfigCallback(
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PassConfigCallback &&C)
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: Callback(std::move(C)) {
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TargetPassConfigCallbacks.push_back(this);
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}
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RegisterTargetPassConfigCallback::~RegisterTargetPassConfigCallback() {
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const auto &It = find(TargetPassConfigCallbacks, this);
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if (It != TargetPassConfigCallbacks.end())
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TargetPassConfigCallbacks.erase(It);
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}
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} // namespace llvm

‎llvm/test/Other/codegen-plugin-loading.ll

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; RUN: llc -load %llvmshlibdir/../unittests/CodeGen/CGPluginTest/CGTestPlugin%pluginext %s -o - | FileCheck %s
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; REQUIRES: native, system-linux, llvm-dylib
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; CHECK: CodeGen Test Pass running on main
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define void @main() {
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ret void
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}

‎llvm/unittests/CodeGen/CGPluginTest/CMakeLists.txt

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set(LLVM_LINK_COMPONENTS
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${LLVM_TARGETS_TO_BUILD}
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Support
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Core
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Target
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CodeGen
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)
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add_llvm_unittest(CGPluginTest
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PluginTest.cpp
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Plugin/CodeGenTestPass.cpp
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EXPORT_SYMBOLS
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)
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target_link_libraries(CGPluginTest PRIVATE LLVMTestingSupport)
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unset(LLVM_LINK_COMPONENTS)
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add_subdirectory(Plugin)

‎llvm/unittests/CodeGen/CGPluginTest/Plugin/CMakeLists.txt

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if (NOT WIN32 AND NOT CYGWIN)
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unset(LLVM_LINK_COMPONENTS)
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add_llvm_library(CGTestPlugin MODULE BUILDTREE_ONLY
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CodeGenTestPass.cpp
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Plugin.cpp
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)
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# Put PLUGIN next to the unit test executable.
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set_output_directory(CGTestPlugin
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BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_CFG_INTDIR}/../
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LIBRARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_CFG_INTDIR}/../
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)
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set_target_properties(CGTestPlugin PROPERTIES FOLDER "Tests")
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add_dependencies(CGTestPlugin intrinsics_gen vt_gen)
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add_dependencies(CGPluginTest CGTestPlugin)
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endif ()

‎llvm/unittests/CodeGen/CGPluginTest/Plugin/CodeGenTestPass.cpp

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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "CodeGenTestPass.h"
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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using namespace llvm;
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#define DEBUG_TYPE "codegen-test"
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#define CODEGEN_TEST_NAME "CodeGen Test Pass"
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CodeGenTest::CodeGenTest() : MachineFunctionPass(ID) {}
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bool CodeGenTest::runOnMachineFunction(MachineFunction &MF) {
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outs() << CODEGEN_TEST_NAME << " running on " << MF.getName()
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<< "\n"; // used for the lit test
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if (RunCallback)
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RunCallback();
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return true;
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}
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StringRef CodeGenTest::getPassName() const { return CODEGEN_TEST_NAME; }
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char CodeGenTest::ID = 0;
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std::function<void()> CodeGenTest::RunCallback;
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INITIALIZE_PASS(CodeGenTest, DEBUG_TYPE, CODEGEN_TEST_NAME, false, false)

‎llvm/unittests/CodeGen/CGPluginTest/Plugin/CodeGenTestPass.h

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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef CODEGEN_TEST_PASS
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#define CODEGEN_TEST_PASS
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#include <llvm/CodeGen/MachineFunctionPass.h>
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using namespace llvm;
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namespace llvm {
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void initializeCodeGenTestPass(PassRegistry &);
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} // namespace llvm
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class CodeGenTest : public MachineFunctionPass {
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public:
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static char ID;
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CodeGenTest();
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bool runOnMachineFunction(MachineFunction &MF) override;
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StringRef getPassName() const override;
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static std::function<void()> RunCallback;
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};
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#endif // CODEGEN_TEST_PASS

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