forked from OSchip/llvm-project
132 lines
4.5 KiB
C++
132 lines
4.5 KiB
C++
//===- LoopExtractor.cpp - Extract each loop into a new function ----------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// A pass wrapper around the ExtractLoop() scalar transformation to extract each
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// top-level loop into its own new function. If the loop is the ONLY loop in a
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// given function, it is not touched. This is a pass most useful for debugging
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// via bugpoint.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/IPO.h"
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#include "llvm/iTerminators.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/Analysis/LoopInfo.h"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Transforms/Utils/FunctionUtils.h"
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#include "Support/Statistic.h"
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using namespace llvm;
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namespace {
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Statistic<> NumExtracted("loop-extract", "Number of loops extracted");
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// FIXME: This is not a function pass, but the PassManager doesn't allow
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// Module passes to require FunctionPasses, so we can't get loop info if we're
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// not a function pass.
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struct LoopExtractor : public FunctionPass {
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unsigned NumLoops;
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LoopExtractor(unsigned numLoops = ~0) : NumLoops(numLoops) {}
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virtual bool runOnFunction(Function &F);
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequiredID(BreakCriticalEdgesID);
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AU.addRequiredID(LoopSimplifyID);
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AU.addRequired<DominatorSet>();
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AU.addRequired<LoopInfo>();
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}
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};
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RegisterOpt<LoopExtractor>
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X("loop-extract", "Extract loops into new functions");
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/// SingleLoopExtractor - For bugpoint.
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struct SingleLoopExtractor : public LoopExtractor {
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SingleLoopExtractor() : LoopExtractor(1) {}
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};
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RegisterOpt<SingleLoopExtractor>
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Y("loop-extract-single", "Extract at most one loop into a new function");
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} // End anonymous namespace
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bool LoopExtractor::runOnFunction(Function &F) {
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LoopInfo &LI = getAnalysis<LoopInfo>();
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// If this function has no loops, there is nothing to do.
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if (LI.begin() == LI.end())
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return false;
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DominatorSet &DS = getAnalysis<DominatorSet>();
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// If there is more than one top-level loop in this function, extract all of
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// the loops.
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bool Changed = false;
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if (LI.end()-LI.begin() > 1) {
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for (LoopInfo::iterator i = LI.begin(), e = LI.end(); i != e; ++i) {
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if (NumLoops == 0) return Changed;
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--NumLoops;
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Changed |= ExtractLoop(DS, *i) != 0;
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++NumExtracted;
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}
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} else {
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// Otherwise there is exactly one top-level loop. If this function is more
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// than a minimal wrapper around the loop, extract the loop.
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Loop *TLL = *LI.begin();
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bool ShouldExtractLoop = false;
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// Extract the loop if the entry block doesn't branch to the loop header.
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TerminatorInst *EntryTI = F.getEntryBlock().getTerminator();
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if (!isa<BranchInst>(EntryTI) ||
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!cast<BranchInst>(EntryTI)->isUnconditional() ||
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EntryTI->getSuccessor(0) != TLL->getHeader())
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ShouldExtractLoop = true;
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else {
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// Check to see if any exits from the loop are more than just return
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// blocks.
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std::vector<BasicBlock*> ExitBlocks;
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TLL->getExitBlocks(ExitBlocks);
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for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
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if (!isa<ReturnInst>(ExitBlocks[i]->getTerminator())) {
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ShouldExtractLoop = true;
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break;
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}
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}
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if (ShouldExtractLoop) {
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if (NumLoops == 0) return Changed;
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--NumLoops;
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Changed |= ExtractLoop(DS, TLL) != 0;
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++NumExtracted;
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} else {
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// Okay, this function is a minimal container around the specified loop.
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// If we extract the loop, we will continue to just keep extracting it
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// infinitely... so don't extract it. However, if the loop contains any
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// subloops, extract them.
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for (Loop::iterator i = TLL->begin(), e = TLL->end(); i != e; ++i) {
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if (NumLoops == 0) return Changed;
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--NumLoops;
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Changed |= ExtractLoop(DS, *i) != 0;
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++NumExtracted;
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}
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}
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}
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return Changed;
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}
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// createSingleLoopExtractorPass - This pass extracts one natural loop from the
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// program into a function if it can. This is used by bugpoint.
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//
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Pass *llvm::createSingleLoopExtractorPass() {
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return new SingleLoopExtractor();
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}
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