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