1 //===- LoopExtractor.cpp - Extract each loop into a new function ----------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // A pass wrapper around the ExtractLoop() scalar transformation to extract each
11 // top-level loop into its own new function. If the loop is the ONLY loop in a
12 // given function, it is not touched. This is a pass most useful for debugging
15 //===----------------------------------------------------------------------===//
17 #include "llvm/Transforms/IPO.h"
18 #include "llvm/iTerminators.h"
19 #include "llvm/Module.h"
20 #include "llvm/Pass.h"
21 #include "llvm/Analysis/Dominators.h"
22 #include "llvm/Analysis/LoopInfo.h"
23 #include "llvm/Transforms/Scalar.h"
24 #include "llvm/Transforms/Utils/FunctionUtils.h"
28 // FIXME: This is not a function pass, but the PassManager doesn't allow
29 // Module passes to require FunctionPasses, so we can't get loop info if we're
30 // not a function pass.
31 struct LoopExtractor : public FunctionPass {
34 LoopExtractor(unsigned numLoops = ~0) : NumLoops(numLoops) {}
36 virtual bool runOnFunction(Function &F);
38 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
39 AU.addRequired<DominatorSet>();
40 AU.addRequired<LoopInfo>();
41 AU.addRequiredID(LoopSimplifyID);
45 RegisterOpt<LoopExtractor>
46 X("loop-extract", "Extract loops into new functions");
48 /// SingleLoopExtractor - For bugpoint.
49 struct SingleLoopExtractor : public LoopExtractor {
50 SingleLoopExtractor() : LoopExtractor(1) {}
53 RegisterOpt<SingleLoopExtractor>
54 Y("loop-extract-single", "Extract at most one loop into a new function");
55 } // End anonymous namespace
57 bool LoopExtractor::runOnFunction(Function &F) {
58 LoopInfo &LI = getAnalysis<LoopInfo>();
60 // If this function has no loops, there is nothing to do.
61 if (LI.begin() == LI.end())
64 DominatorSet &DS = getAnalysis<DominatorSet>();
66 // If there is more than one top-level loop in this function, extract all of
69 if (LI.end()-LI.begin() > 1) {
70 for (LoopInfo::iterator i = LI.begin(), e = LI.end(); i != e; ++i) {
71 if (NumLoops == 0) return Changed;
73 Changed |= ExtractLoop(DS, *i) != 0;
76 // Otherwise there is exactly one top-level loop. If this function is more
77 // than a minimal wrapper around the loop, extract the loop.
78 Loop *TLL = *LI.begin();
79 bool ShouldExtractLoop = false;
81 // Extract the loop if the entry block doesn't branch to the loop header.
82 TerminatorInst *EntryTI = F.getEntryBlock().getTerminator();
83 if (!isa<BranchInst>(EntryTI) ||
84 !cast<BranchInst>(EntryTI)->isUnconditional() ||
85 EntryTI->getSuccessor(0) != TLL->getHeader())
86 ShouldExtractLoop = true;
88 // Check to see if any exits from the loop are more than just return
90 for (unsigned i = 0, e = TLL->getExitBlocks().size(); i != e; ++i)
91 if (!isa<ReturnInst>(TLL->getExitBlocks()[i]->getTerminator())) {
92 ShouldExtractLoop = true;
97 if (ShouldExtractLoop) {
98 if (NumLoops == 0) return Changed;
100 Changed |= ExtractLoop(DS, TLL) != 0;
102 // Okay, this function is a minimal container around the specified loop.
103 // If we extract the loop, we will continue to just keep extracting it
104 // infinitely... so don't extract it. However, if the loop contains any
105 // subloops, extract them.
106 for (Loop::iterator i = TLL->begin(), e = TLL->end(); i != e; ++i) {
107 if (NumLoops == 0) return Changed;
109 Changed |= ExtractLoop(DS, *i) != 0;
117 // createSingleLoopExtractorPass - This pass extracts one natural loop from the
118 // program into a function if it can. This is used by bugpoint.
120 Pass *llvm::createSingleLoopExtractorPass() {
121 return new SingleLoopExtractor();