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7724d08fc6
Use them in two isolated transforms so we know they work and aren't dead code. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228173 91177308-0d34-0410-b5e6-96231b3b80d8
184 lines
6.2 KiB
C++
184 lines
6.2 KiB
C++
//===- PartialInlining.cpp - Inline parts of functions --------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass performs partial inlining, typically by inlining an if statement
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// that surrounds the body of the function.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/IPO.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/IR/CFG.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/Transforms/Utils/Cloning.h"
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#include "llvm/Transforms/Utils/CodeExtractor.h"
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using namespace llvm;
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#define DEBUG_TYPE "partialinlining"
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STATISTIC(NumPartialInlined, "Number of functions partially inlined");
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namespace {
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struct PartialInliner : public ModulePass {
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void getAnalysisUsage(AnalysisUsage &AU) const override { }
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static char ID; // Pass identification, replacement for typeid
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PartialInliner() : ModulePass(ID) {
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initializePartialInlinerPass(*PassRegistry::getPassRegistry());
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}
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bool runOnModule(Module& M) override;
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private:
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Function* unswitchFunction(Function* F);
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};
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}
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char PartialInliner::ID = 0;
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INITIALIZE_PASS(PartialInliner, "partial-inliner",
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"Partial Inliner", false, false)
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ModulePass* llvm::createPartialInliningPass() { return new PartialInliner(); }
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Function* PartialInliner::unswitchFunction(Function* F) {
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// First, verify that this function is an unswitching candidate...
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BasicBlock* entryBlock = F->begin();
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BranchInst *BR = dyn_cast<BranchInst>(entryBlock->getTerminator());
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if (!BR || BR->isUnconditional())
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return nullptr;
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BasicBlock* returnBlock = nullptr;
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BasicBlock* nonReturnBlock = nullptr;
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unsigned returnCount = 0;
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for (BasicBlock *BB : successors(entryBlock)) {
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if (isa<ReturnInst>(BB->getTerminator())) {
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returnBlock = BB;
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returnCount++;
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} else
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nonReturnBlock = BB;
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}
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if (returnCount != 1)
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return nullptr;
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// Clone the function, so that we can hack away on it.
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ValueToValueMapTy VMap;
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Function* duplicateFunction = CloneFunction(F, VMap,
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/*ModuleLevelChanges=*/false);
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duplicateFunction->setLinkage(GlobalValue::InternalLinkage);
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F->getParent()->getFunctionList().push_back(duplicateFunction);
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BasicBlock* newEntryBlock = cast<BasicBlock>(VMap[entryBlock]);
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BasicBlock* newReturnBlock = cast<BasicBlock>(VMap[returnBlock]);
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BasicBlock* newNonReturnBlock = cast<BasicBlock>(VMap[nonReturnBlock]);
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// Go ahead and update all uses to the duplicate, so that we can just
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// use the inliner functionality when we're done hacking.
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F->replaceAllUsesWith(duplicateFunction);
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// Special hackery is needed with PHI nodes that have inputs from more than
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// one extracted block. For simplicity, just split the PHIs into a two-level
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// sequence of PHIs, some of which will go in the extracted region, and some
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// of which will go outside.
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BasicBlock* preReturn = newReturnBlock;
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newReturnBlock = newReturnBlock->splitBasicBlock(
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newReturnBlock->getFirstNonPHI());
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BasicBlock::iterator I = preReturn->begin();
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BasicBlock::iterator Ins = newReturnBlock->begin();
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while (I != preReturn->end()) {
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PHINode* OldPhi = dyn_cast<PHINode>(I);
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if (!OldPhi) break;
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PHINode* retPhi = PHINode::Create(OldPhi->getType(), 2, "", Ins);
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OldPhi->replaceAllUsesWith(retPhi);
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Ins = newReturnBlock->getFirstNonPHI();
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retPhi->addIncoming(I, preReturn);
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retPhi->addIncoming(OldPhi->getIncomingValueForBlock(newEntryBlock),
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newEntryBlock);
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OldPhi->removeIncomingValue(newEntryBlock);
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++I;
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}
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newEntryBlock->getTerminator()->replaceUsesOfWith(preReturn, newReturnBlock);
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// Gather up the blocks that we're going to extract.
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std::vector<BasicBlock*> toExtract;
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toExtract.push_back(newNonReturnBlock);
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for (Function::iterator FI = duplicateFunction->begin(),
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FE = duplicateFunction->end(); FI != FE; ++FI)
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if (&*FI != newEntryBlock && &*FI != newReturnBlock &&
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&*FI != newNonReturnBlock)
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toExtract.push_back(FI);
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// The CodeExtractor needs a dominator tree.
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DominatorTree DT;
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DT.recalculate(*duplicateFunction);
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// Extract the body of the if.
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Function* extractedFunction
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= CodeExtractor(toExtract, &DT).extractCodeRegion();
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InlineFunctionInfo IFI;
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// Inline the top-level if test into all callers.
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std::vector<User *> Users(duplicateFunction->user_begin(),
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duplicateFunction->user_end());
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for (std::vector<User*>::iterator UI = Users.begin(), UE = Users.end();
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UI != UE; ++UI)
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if (CallInst *CI = dyn_cast<CallInst>(*UI))
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InlineFunction(CI, IFI);
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else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI))
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InlineFunction(II, IFI);
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// Ditch the duplicate, since we're done with it, and rewrite all remaining
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// users (function pointers, etc.) back to the original function.
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duplicateFunction->replaceAllUsesWith(F);
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duplicateFunction->eraseFromParent();
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++NumPartialInlined;
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return extractedFunction;
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}
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bool PartialInliner::runOnModule(Module& M) {
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std::vector<Function*> worklist;
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worklist.reserve(M.size());
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for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI)
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if (!FI->use_empty() && !FI->isDeclaration())
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worklist.push_back(&*FI);
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bool changed = false;
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while (!worklist.empty()) {
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Function* currFunc = worklist.back();
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worklist.pop_back();
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if (currFunc->use_empty()) continue;
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bool recursive = false;
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for (User *U : currFunc->users())
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if (Instruction* I = dyn_cast<Instruction>(U))
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if (I->getParent()->getParent() == currFunc) {
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recursive = true;
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break;
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}
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if (recursive) continue;
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if (Function* newFunc = unswitchFunction(currFunc)) {
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worklist.push_back(newFunc);
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changed = true;
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}
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}
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return changed;
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}
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