使用现代LLVM运行默认优化管道 [英] Run default optimization pipeline using modern LLVM

问题描述

我正在使用LLVM 7，我有一个llvm::Module，我想使用标准优化管道进行优化.不幸的是，我没有可以调用的llvm::runDefaultOptimizations函数.似乎有无数种方法可以优化LLVM中的模块.我在此主题上进行的搜索发现了许多旧的/折旧的API，以及一些无法在我的系统上运行的示例.

I'm using LLVM 7 and I have an llvm::Module that I'd like to optimize using the standard optimization pipeline. Unfortunately, there isn't a llvm::runDefaultOptimizations function that I can call. There seems to be a bajillion ways to optimize a module in LLVM. My searches on this topic have found many old/depreciated APIs and some examples that don't work on my system.

我希望在-O3上运行所有标准优化，并尽可能减少麻烦.我不想手动列出所有过程，甚至不想编写for循环.我以为llvm::PassBuilder::buildModuleOptimizationPipeline可能是解决方案，但是当我尝试使用该功能时却收到了链接器错误，我认为这很奇怪.

I want to run all of the standard optimizations at -O3 with the least amount of hassle possible. I don't want to manually list all of the passes or even write a for loop. I thought llvm::PassBuilder::buildModuleOptimizationPipeline might be the solution but I get a linker error when I try to use that function which I think is really strange.

推荐答案

我最终使用了opt工具的源代码(

I ended up taking the source of the opt tool (found here) and stripping everything I didn't need. I ended up with this:

#include <llvm/IR/Verifier.h>
#include <llvm/Transforms/IPO.h>
#include <llvm/IR/LegacyPassManager.h>
#include <llvm/Target/TargetMachine.h>
#include <llvm/Analysis/TargetLibraryInfo.h>
#include <llvm/Analysis/TargetTransformInfo.h>
#include <llvm/Transforms/IPO/PassManagerBuilder.h>

namespace {

void addOptPasses(
  llvm::legacy::PassManagerBase &passes,
  llvm::legacy::FunctionPassManager &fnPasses,
  llvm::TargetMachine *machine
) {
  llvm::PassManagerBuilder builder;
  builder.OptLevel = 3;
  builder.SizeLevel = 0;
  builder.Inliner = llvm::createFunctionInliningPass(3, 0, false);
  builder.LoopVectorize = true;
  builder.SLPVectorize = true;
  machine->adjustPassManager(builder);

  builder.populateFunctionPassManager(fnPasses);
  builder.populateModulePassManager(passes);
}

void addLinkPasses(llvm::legacy::PassManagerBase &passes) {
  llvm::PassManagerBuilder builder;
  builder.VerifyInput = true;
  builder.Inliner = llvm::createFunctionInliningPass(3, 0, false);
  builder.populateLTOPassManager(passes);
}

}

void optimizeModule(llvm::TargetMachine *machine, llvm::Module *module) {
  module->setTargetTriple(machine->getTargetTriple().str());
  module->setDataLayout(machine->createDataLayout());

  llvm::legacy::PassManager passes;
  passes.add(new llvm::TargetLibraryInfoWrapperPass(machine->getTargetTriple()));
  passes.add(llvm::createTargetTransformInfoWrapperPass(machine->getTargetIRAnalysis()));

  llvm::legacy::FunctionPassManager fnPasses(module);
  fnPasses.add(llvm::createTargetTransformInfoWrapperPass(machine->getTargetIRAnalysis()));

  addOptPasses(passes, fnPasses, machine);
  addLinkPasses(passes);

  fnPasses.doInitialization();
  for (llvm::Function &func : *module) {
    fnPasses.run(func);
  }
  fnPasses.doFinalization();

  passes.add(llvm::createVerifierPass());
  passes.run(*module);
}

这大致等效于将-O3传递给opt.它正在使用某些legacy内容，但我并不介意.

This is roughly equivalent to passing -O3 to opt. It's using some legacy stuff but I don't really mind.

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