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use llvm-mca as a cost model -- this implements that, but the work is…
… unfinished and it isn't used anywhere, still work to do (google#816)
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| Original file line number | Diff line number | Diff line change |
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| // Copyright 2014 The Souper Authors. All rights reserved. | ||
| // | ||
| // 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. | ||
|
|
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| #include "souper/Codegen/Codegen.h" | ||
| #include "souper/Inst/Inst.h" | ||
| #include "llvm/ADT/Statistic.h" | ||
| #include "llvm/IR/Dominators.h" | ||
| #include "llvm/IR/IRBuilder.h" | ||
| #include "llvm/IR/LegacyPassManager.h" | ||
| #include "llvm/IR/LLVMContext.h" | ||
| #include "llvm/IR/Module.h" | ||
| #include "llvm/IR/PassManager.h" | ||
| #include "llvm/IR/Value.h" | ||
| #include "llvm/Object/ObjectFile.h" | ||
| #include "llvm/Passes/PassBuilder.h" | ||
| #include "llvm/Support/SmallVectorMemoryBuffer.h" | ||
| #include "llvm/Support/TargetRegistry.h" | ||
| #include "llvm/Support/TargetSelect.h" | ||
| #include "llvm/Target/TargetMachine.h" | ||
| #include "llvm/Target/TargetOptions.h" | ||
| #include <map> | ||
|
|
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| #define DEBUG_TYPE "souper" | ||
|
|
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| using namespace llvm; | ||
|
|
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| namespace souper { | ||
|
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| void optimizeModule(llvm::Module &M) { | ||
| llvm::LoopAnalysisManager LAM; | ||
| llvm::FunctionAnalysisManager FAM; | ||
| llvm::CGSCCAnalysisManager CGAM; | ||
| llvm::ModuleAnalysisManager MAM; | ||
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| llvm::PassBuilder PB; | ||
| PB.registerModuleAnalyses(MAM); | ||
| PB.registerCGSCCAnalyses(CGAM); | ||
| PB.registerFunctionAnalyses(FAM); | ||
| PB.registerLoopAnalyses(LAM); | ||
| PB.crossRegisterProxies(LAM, FAM, CGAM, MAM); | ||
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| llvm::FunctionPassManager FPM = | ||
| PB.buildFunctionSimplificationPipeline(llvm::PassBuilder::OptimizationLevel::O2, | ||
| ThinOrFullLTOPhase::None); | ||
| llvm::ModulePassManager MPM; | ||
| MPM.addPass(createModuleToFunctionPassAdaptor(std::move(FPM))); | ||
| MPM.run(M, MAM); | ||
| } | ||
|
|
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| long getCodeSize(Module &M, TargetMachine *TM) { | ||
| M.setDataLayout(TM->createDataLayout()); | ||
| SmallVector<char, 256> DotO; | ||
| raw_svector_ostream dest(DotO); | ||
|
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| legacy::PassManager pass; | ||
| if (TM->addPassesToEmitFile(pass, dest, nullptr, CGFT_ObjectFile)) { | ||
| errs() << "Target machine can't emit a file of this type"; | ||
| report_fatal_error("oops"); | ||
| } | ||
| pass.run(M); | ||
|
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| SmallVectorMemoryBuffer Buf(std::move(DotO)); | ||
| auto ObjOrErr = object::ObjectFile::createObjectFile(Buf); | ||
| if (!ObjOrErr) | ||
| report_fatal_error("createObjectFile() failed"); | ||
| object::ObjectFile *OF = ObjOrErr.get().get(); | ||
| auto SecList = OF->sections(); | ||
| long Size = 0; | ||
| for (auto &S : SecList) { | ||
| if (S.isText()) | ||
| Size += S.getSize(); | ||
| } | ||
| if (Size > 0) | ||
| return Size; | ||
| else | ||
| report_fatal_error("no text segment found"); | ||
| } | ||
|
|
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| struct TargetInfo { | ||
| std::string Trip, CPU; | ||
| }; | ||
|
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| std::vector<TargetInfo> Targets { | ||
| { "x86_64", "skylake" }, | ||
| { "aarch64", "apple-a12" }, | ||
| }; | ||
|
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| bool Init = false; | ||
|
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| void getBackendCost(InstContext &IC, souper::Inst *I, BackendCost &BC) { | ||
| // TODO is this better than just forcing all clients of this code to | ||
| // do the init themselves? | ||
| if (!Init) { | ||
| InitializeAllTargetInfos(); | ||
| InitializeAllTargets(); | ||
| InitializeAllTargetMCs(); | ||
| InitializeAllAsmParsers(); | ||
| InitializeAllAsmPrinters(); | ||
| Init = true; | ||
| } | ||
|
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| llvm::LLVMContext C; | ||
| llvm::Module M("", C); | ||
| if (genModule(IC, I, M)) | ||
| llvm::report_fatal_error("codegen error in getBackendCost()"); | ||
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| optimizeModule(M); | ||
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| llvm::errs() << M; | ||
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| BackendCost Cost; | ||
| for (auto &T : Targets) { | ||
| std::string Error; | ||
| auto Target = TargetRegistry::lookupTarget(T.Trip, Error); | ||
| if (!Target) { | ||
| errs() << Error; | ||
| report_fatal_error("can't lookup target"); | ||
| } | ||
|
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| auto Features = ""; | ||
| TargetOptions Opt; | ||
| auto RM = Optional<Reloc::Model>(); | ||
| auto TM = Target->createTargetMachine(T.Trip, T.CPU, Features, Opt, RM); | ||
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| Cost.C.push_back(getCodeSize(M, TM)); | ||
| } | ||
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| llvm::errs() << "cost vector: "; | ||
| for (auto I : Cost.C) { | ||
| llvm::errs() << I << " "; | ||
| } | ||
| llvm::errs() << "\n"; | ||
| } | ||
|
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| int threeWayCompare(int A, int B) { | ||
| if (A < B) | ||
| return -1; | ||
| if (A > B) | ||
| return 1; | ||
| return 0; | ||
| } | ||
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| // "The value returned indicates whether the element passed as first | ||
| // argument is considered to go before the second" | ||
| bool compareCosts(const BackendCost &C1, const BackendCost &C2) { | ||
| assert(C1.C.size() == C2.C.size()); | ||
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| int Count = 0; | ||
| for (int i = 0; i < C1.C.size(); ++i) | ||
| Count += threeWayCompare(C1.C[i], C2.C[i]); | ||
| if (Count < 0) | ||
| return true; | ||
| if (Count > 0) | ||
| return false; | ||
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| // break ties using souper cost? | ||
| // break final ties how? we want a canonical winner for all cases | ||
| // FIXME -- not finished | ||
| return false; | ||
| } | ||
|
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| } // namespace souper |
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