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.addRequiredID(BreakCriticalEdgesID);
40 AU.addRequiredID(LoopSimplifyID);
41 AU.addRequired<DominatorSet>();
42 AU.addRequired<LoopInfo>();
46 RegisterOpt<LoopExtractor>
47 X("loop-extract", "Extract loops into new functions");
49 /// SingleLoopExtractor - For bugpoint.
50 struct SingleLoopExtractor : public LoopExtractor {
51 SingleLoopExtractor() : LoopExtractor(1) {}
54 RegisterOpt<SingleLoopExtractor>
55 Y("loop-extract-single", "Extract at most one loop into a new function");
56 } // End anonymous namespace
58 bool LoopExtractor::runOnFunction(Function &F) {
59 LoopInfo &LI = getAnalysis<LoopInfo>();
61 // If this function has no loops, there is nothing to do.
62 if (LI.begin() == LI.end())
65 DominatorSet &DS = getAnalysis<DominatorSet>();
67 // If there is more than one top-level loop in this function, extract all of
70 if (LI.end()-LI.begin() > 1) {
71 for (LoopInfo::iterator i = LI.begin(), e = LI.end(); i != e; ++i) {
72 if (NumLoops == 0) return Changed;
74 Changed |= ExtractLoop(DS, *i) != 0;
77 // Otherwise there is exactly one top-level loop. If this function is more
78 // than a minimal wrapper around the loop, extract the loop.
79 Loop *TLL = *LI.begin();
80 bool ShouldExtractLoop = false;
82 // Extract the loop if the entry block doesn't branch to the loop header.
83 TerminatorInst *EntryTI = F.getEntryBlock().getTerminator();
84 if (!isa<BranchInst>(EntryTI) ||
85 !cast<BranchInst>(EntryTI)->isUnconditional() ||
86 EntryTI->getSuccessor(0) != TLL->getHeader())
87 ShouldExtractLoop = true;
89 // Check to see if any exits from the loop are more than just return
91 for (unsigned i = 0, e = TLL->getExitBlocks().size(); i != e; ++i)
92 if (!isa<ReturnInst>(TLL->getExitBlocks()[i]->getTerminator())) {
93 ShouldExtractLoop = true;
98 if (ShouldExtractLoop) {
99 if (NumLoops == 0) return Changed;
101 Changed |= ExtractLoop(DS, TLL) != 0;
103 // Okay, this function is a minimal container around the specified loop.
104 // If we extract the loop, we will continue to just keep extracting it
105 // infinitely... so don't extract it. However, if the loop contains any
106 // subloops, extract them.
107 for (Loop::iterator i = TLL->begin(), e = TLL->end(); i != e; ++i) {
108 if (NumLoops == 0) return Changed;
110 Changed |= ExtractLoop(DS, *i) != 0;
118 // createSingleLoopExtractorPass - This pass extracts one natural loop from the
119 // program into a function if it can. This is used by bugpoint.
121 Pass *llvm::createSingleLoopExtractorPass() {
122 return new SingleLoopExtractor();