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Owen Andersonca399022009-06-14 08:26:32 +00001//===- PartialInlining.cpp - Inline parts of functions --------------------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This pass performs partial inlining, typically by inlining an if statement
11// that surrounds the body of the function.
12//
13//===----------------------------------------------------------------------===//
14
15#define DEBUG_TYPE "partialinlining"
16#include "llvm/Transforms/IPO.h"
17#include "llvm/Instructions.h"
18#include "llvm/Module.h"
19#include "llvm/Pass.h"
20#include "llvm/Analysis/Dominators.h"
21#include "llvm/Transforms/Utils/Cloning.h"
22#include "llvm/Transforms/Utils/FunctionUtils.h"
Owen Anderson63676842009-06-15 20:50:26 +000023#include "llvm/ADT/Statistic.h"
Owen Andersonca399022009-06-14 08:26:32 +000024#include "llvm/Support/Compiler.h"
25#include "llvm/Support/CFG.h"
26using namespace llvm;
27
Owen Anderson63676842009-06-15 20:50:26 +000028STATISTIC(NumPartialInlined, "Number of functions partially inlined");
29
Owen Andersonca399022009-06-14 08:26:32 +000030namespace {
31 struct VISIBILITY_HIDDEN PartialInliner : public ModulePass {
32 virtual void getAnalysisUsage(AnalysisUsage &AU) const { }
33 static char ID; // Pass identification, replacement for typeid
34 PartialInliner() : ModulePass(&ID) {}
35
36 bool runOnModule(Module& M);
37
38 private:
39 Function* unswitchFunction(Function* F);
40 };
41}
42
43char PartialInliner::ID = 0;
44static RegisterPass<PartialInliner> X("partial-inliner", "Partial Inliner");
45
46ModulePass* llvm::createPartialInliningPass() { return new PartialInliner(); }
47
48Function* PartialInliner::unswitchFunction(Function* F) {
49 // First, verify that this function is an unswitching candidate...
50 BasicBlock* entryBlock = F->begin();
Owen Andersona0ecbe72009-09-08 19:53:15 +000051 BranchInst *BR = dyn_cast<BranchInst>(entryBlock->getTerminator());
52 if (!BR || BR->isUnconditional())
Owen Andersonca399022009-06-14 08:26:32 +000053 return 0;
54
55 BasicBlock* returnBlock = 0;
56 BasicBlock* nonReturnBlock = 0;
57 unsigned returnCount = 0;
58 for (succ_iterator SI = succ_begin(entryBlock), SE = succ_end(entryBlock);
59 SI != SE; ++SI)
60 if (isa<ReturnInst>((*SI)->getTerminator())) {
61 returnBlock = *SI;
62 returnCount++;
63 } else
64 nonReturnBlock = *SI;
65
66 if (returnCount != 1)
67 return 0;
68
69 // Clone the function, so that we can hack away on it.
70 DenseMap<const Value*, Value*> ValueMap;
71 Function* duplicateFunction = CloneFunction(F, ValueMap);
72 duplicateFunction->setLinkage(GlobalValue::InternalLinkage);
73 F->getParent()->getFunctionList().push_back(duplicateFunction);
74 BasicBlock* newEntryBlock = cast<BasicBlock>(ValueMap[entryBlock]);
75 BasicBlock* newReturnBlock = cast<BasicBlock>(ValueMap[returnBlock]);
76 BasicBlock* newNonReturnBlock = cast<BasicBlock>(ValueMap[nonReturnBlock]);
77
78 // Go ahead and update all uses to the duplicate, so that we can just
79 // use the inliner functionality when we're done hacking.
80 F->replaceAllUsesWith(duplicateFunction);
81
82 // Special hackery is needed with PHI nodes that have inputs from more than
83 // one extracted block. For simplicity, just split the PHIs into a two-level
84 // sequence of PHIs, some of which will go in the extracted region, and some
85 // of which will go outside.
86 BasicBlock* preReturn = newReturnBlock;
87 newReturnBlock = newReturnBlock->splitBasicBlock(
88 newReturnBlock->getFirstNonPHI());
89 BasicBlock::iterator I = preReturn->begin();
90 BasicBlock::iterator Ins = newReturnBlock->begin();
91 while (I != preReturn->end()) {
92 PHINode* OldPhi = dyn_cast<PHINode>(I);
93 if (!OldPhi) break;
94
95 PHINode* retPhi = PHINode::Create(OldPhi->getType(), "", Ins);
96 OldPhi->replaceAllUsesWith(retPhi);
97 Ins = newReturnBlock->getFirstNonPHI();
98
99 retPhi->addIncoming(I, preReturn);
100 retPhi->addIncoming(OldPhi->getIncomingValueForBlock(newEntryBlock),
101 newEntryBlock);
102 OldPhi->removeIncomingValue(newEntryBlock);
103
104 ++I;
105 }
106 newEntryBlock->getTerminator()->replaceUsesOfWith(preReturn, newReturnBlock);
107
108 // Gather up the blocks that we're going to extract.
109 std::vector<BasicBlock*> toExtract;
110 toExtract.push_back(newNonReturnBlock);
111 for (Function::iterator FI = duplicateFunction->begin(),
112 FE = duplicateFunction->end(); FI != FE; ++FI)
113 if (&*FI != newEntryBlock && &*FI != newReturnBlock &&
114 &*FI != newNonReturnBlock)
115 toExtract.push_back(FI);
116
117 // The CodeExtractor needs a dominator tree.
118 DominatorTree DT;
119 DT.runOnFunction(*duplicateFunction);
120
121 // Extract the body of the the if.
122 Function* extractedFunction = ExtractCodeRegion(DT, toExtract);
123
124 // Inline the top-level if test into all callers.
125 std::vector<User*> Users(duplicateFunction->use_begin(),
126 duplicateFunction->use_end());
127 for (std::vector<User*>::iterator UI = Users.begin(), UE = Users.end();
128 UI != UE; ++UI)
129 if (CallInst* CI = dyn_cast<CallInst>(*UI))
130 InlineFunction(CI);
131 else if (InvokeInst* II = dyn_cast<InvokeInst>(*UI))
132 InlineFunction(II);
133
134 // Ditch the duplicate, since we're done with it, and rewrite all remaining
135 // users (function pointers, etc.) back to the original function.
136 duplicateFunction->replaceAllUsesWith(F);
137 duplicateFunction->eraseFromParent();
138
Owen Anderson63676842009-06-15 20:50:26 +0000139 ++NumPartialInlined;
140
Owen Andersonca399022009-06-14 08:26:32 +0000141 return extractedFunction;
142}
143
144bool PartialInliner::runOnModule(Module& M) {
145 std::vector<Function*> worklist;
146 worklist.reserve(M.size());
147 for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI)
148 if (!FI->use_empty() && !FI->isDeclaration())
149 worklist.push_back(&*FI);
150
151 bool changed = false;
152 while (!worklist.empty()) {
153 Function* currFunc = worklist.back();
154 worklist.pop_back();
155
156 if (currFunc->use_empty()) continue;
157
158 bool recursive = false;
159 for (Function::use_iterator UI = currFunc->use_begin(),
160 UE = currFunc->use_end(); UI != UE; ++UI)
161 if (Instruction* I = dyn_cast<Instruction>(UI))
162 if (I->getParent()->getParent() == currFunc) {
163 recursive = true;
164 break;
165 }
166 if (recursive) continue;
167
168
169 if (Function* newFunc = unswitchFunction(currFunc)) {
170 worklist.push_back(newFunc);
171 changed = true;
172 }
173
174 }
175
176 return changed;
Duncan Sandsd5f50da2009-07-03 15:30:58 +0000177}