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and expose it as a utility class rather than as free function wrappers. The simple free-function interface works well for the bugpoint-specific pass's uses of code extraction, but in an upcoming patch for more advanced code extraction, they simply don't expose a rich enough interface. I need to expose various stages of the process of doing the code extraction and query information to decide whether or not to actually complete the extraction or give up. Rather than build up a new predicate model and pass that into these functions, just take the class that was actually implementing the functions and lift it up into a proper interface that can be used to perform code extraction. The interface is cleaned up and re-documented to work better in a header. It also is now setup to accept the blocks to be extracted in the constructor rather than in a method. In passing this essentially reverts my previous commit here exposing a block-level query for eligibility of extraction. That is no longer necessary with the more rich interface as clients can query the extraction object for eligibility directly. This will reduce the number of walks of the input basic block sequence by quite a bit which is useful if this enters the normal optimization pipeline. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156163 91177308-0d34-0410-b5e6-96231b3b80d8
184 lines
6.3 KiB
C++
184 lines
6.3 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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#define DEBUG_TYPE "partialinlining"
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#include "llvm/Transforms/IPO.h"
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#include "llvm/Instructions.h"
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#include "llvm/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/Analysis/Dominators.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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#include "llvm/ADT/Statistic.h"
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#include "llvm/Support/CFG.h"
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using namespace llvm;
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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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virtual void getAnalysisUsage(AnalysisUsage &AU) const { }
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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);
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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 0;
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BasicBlock* returnBlock = 0;
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BasicBlock* nonReturnBlock = 0;
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unsigned returnCount = 0;
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for (succ_iterator SI = succ_begin(entryBlock), SE = succ_end(entryBlock);
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SI != SE; ++SI)
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if (isa<ReturnInst>((*SI)->getTerminator())) {
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returnBlock = *SI;
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returnCount++;
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} else
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nonReturnBlock = *SI;
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if (returnCount != 1)
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return 0;
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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.runOnFunction(*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->use_begin(),
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duplicateFunction->use_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 (Function::use_iterator UI = currFunc->use_begin(),
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UE = currFunc->use_end(); UI != UE; ++UI)
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if (Instruction* I = dyn_cast<Instruction>(*UI))
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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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