1 //===- MethodInlining.cpp - Code to perform method inlining ---------------===//
3 // This file implements inlining of methods.
6 // * Exports functionality to inline any method call
7 // * Inlines methods that consist of a single basic block
8 // * Is able to inline ANY method call
9 // . Has a smart heuristic for when to inline a method
12 // * This pass has a habit of introducing duplicated constant pool entries,
13 // and also opens up a lot of opportunities for constant propogation. It is
14 // a good idea to to run a constant propogation pass, then a DCE pass
15 // sometime after running this pass.
17 // TODO: Currently this throws away all of the symbol names in the method being
18 // inlined to try to avoid name clashes. Use a name if it's not taken
20 //===----------------------------------------------------------------------===//
22 #include "llvm/Optimizations/MethodInlining.h"
23 #include "llvm/Module.h"
24 #include "llvm/Method.h"
25 #include "llvm/iTerminators.h"
26 #include "llvm/iOther.h"
30 #include "llvm/Assembly/Writer.h"
34 // RemapInstruction - Convert the instruction operands from referencing the
35 // current values into those specified by ValueMap.
37 static inline void RemapInstruction(Instruction *I,
38 map<const Value *, Value*> &ValueMap) {
40 for (unsigned op = 0, E = I->getNumOperands(); op != E; ++op) {
41 const Value *Op = I->getOperand(op);
42 Value *V = ValueMap[Op];
43 if (!V && (Op->isMethod() || Op->isConstant()))
44 continue; // Methods and constants don't get relocated
47 cerr << "Val = " << endl << Op << "Addr = " << (void*)Op << endl;
48 cerr << "Inst = " << I;
50 assert(V && "Referenced value not in value map!");
55 // InlineMethod - This function forcibly inlines the called method into the
56 // basic block of the caller. This returns false if it is not possible to
57 // inline this call. The program is still in a well defined state if this
60 // Note that this only does one level of inlining. For example, if the
61 // instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
62 // exists in the instruction stream. Similiarly this will inline a recursive
63 // method by one level.
65 bool opt::InlineMethod(BasicBlock::iterator CIIt) {
66 assert((*CIIt)->getOpcode() == Instruction::Call &&
67 "InlineMethod only works on CallInst nodes!");
68 assert((*CIIt)->getParent() && "Instruction not embedded in basic block!");
69 assert((*CIIt)->getParent()->getParent() && "Instruction not in method!");
71 CallInst *CI = (CallInst*)*CIIt;
72 const Method *CalledMeth = CI->getCalledMethod();
73 if (CalledMeth->isExternal()) return false; // Can't inline external method!
74 Method *CurrentMeth = CI->getParent()->getParent();
76 //cerr << "Inlining " << CalledMeth->getName() << " into "
77 // << CurrentMeth->getName() << endl;
79 BasicBlock *OrigBB = CI->getParent();
81 // Call splitBasicBlock - The original basic block now ends at the instruction
82 // immediately before the call. The original basic block now ends with an
83 // unconditional branch to NewBB, and NewBB starts with the call instruction.
85 BasicBlock *NewBB = OrigBB->splitBasicBlock(CIIt);
87 // Remove (unlink) the CallInst from the start of the new basic block.
88 NewBB->getInstList().remove(CI);
90 // If we have a return value generated by this call, convert it into a PHI
91 // node that gets values from each of the old RET instructions in the original
95 if (CalledMeth->getReturnType() != Type::VoidTy) {
96 PHI = new PHINode(CalledMeth->getReturnType(), CI->getName());
98 // The PHI node should go at the front of the new basic block to merge all
99 // possible incoming values.
101 NewBB->getInstList().push_front(PHI);
103 // Anything that used the result of the function call should now use the PHI
104 // node as their operand.
106 CI->replaceAllUsesWith(PHI);
109 // Keep a mapping between the original method's values and the new duplicated
110 // code's values. This includes all of: Method arguments, instruction values,
111 // constant pool entries, and basic blocks.
113 map<const Value *, Value*> ValueMap;
115 // Add the method arguments to the mapping: (start counting at 1 to skip the
116 // method reference itself)
118 Method::ArgumentListType::const_iterator PTI =
119 CalledMeth->getArgumentList().begin();
120 for (unsigned a = 1, E = CI->getNumOperands(); a != E; ++a, ++PTI)
121 ValueMap[*PTI] = CI->getOperand(a);
123 ValueMap[NewBB] = NewBB; // Returns get converted to reference NewBB
125 // Loop over all of the basic blocks in the method, inlining them as
126 // appropriate. Keep track of the first basic block of the method...
128 for (Method::const_iterator BI = CalledMeth->begin();
129 BI != CalledMeth->end(); ++BI) {
130 const BasicBlock *BB = *BI;
131 assert(BB->getTerminator() && "BasicBlock doesn't have terminator!?!?");
133 // Create a new basic block to copy instructions into!
134 BasicBlock *IBB = new BasicBlock("", NewBB->getParent());
136 ValueMap[*BI] = IBB; // Add basic block mapping.
138 // Make sure to capture the mapping that a return will use...
139 // TODO: This assumes that the RET is returning a value computed in the same
140 // basic block as the return was issued from!
142 const TerminatorInst *TI = BB->getTerminator();
144 // Loop over all instructions copying them over...
145 Instruction *NewInst;
146 for (BasicBlock::const_iterator II = BB->begin();
147 II != (BB->end()-1); ++II) {
148 IBB->getInstList().push_back((NewInst = (*II)->clone()));
149 ValueMap[*II] = NewInst; // Add instruction map to value.
152 // Copy over the terminator now...
153 switch (TI->getOpcode()) {
154 case Instruction::Ret: {
155 const ReturnInst *RI = (const ReturnInst*)TI;
157 if (PHI) { // The PHI node should include this value!
158 assert(RI->getReturnValue() && "Ret should have value!");
159 assert(RI->getReturnValue()->getType() == PHI->getType() &&
160 "Ret value not consistent in method!");
161 PHI->addIncoming((Value*)RI->getReturnValue(), (BasicBlock*)BB);
164 // Add a branch to the code that was after the original Call.
165 IBB->getInstList().push_back(new BranchInst(NewBB));
168 case Instruction::Br:
169 IBB->getInstList().push_back(TI->clone());
173 cerr << "MethodInlining: Don't know how to handle terminator: " << TI;
179 // Loop over all of the instructions in the method, fixing up operand
180 // references as we go. This uses ValueMap to do all the hard work.
182 for (Method::const_iterator BI = CalledMeth->begin();
183 BI != CalledMeth->end(); ++BI) {
184 const BasicBlock *BB = *BI;
185 BasicBlock *NBB = (BasicBlock*)ValueMap[BB];
187 // Loop over all instructions, fixing each one as we find it...
189 for (BasicBlock::iterator II = NBB->begin(); II != NBB->end(); II++)
190 RemapInstruction(*II, ValueMap);
193 if (PHI) RemapInstruction(PHI, ValueMap); // Fix the PHI node also...
195 // Change the branch that used to go to NewBB to branch to the first basic
196 // block of the inlined method.
198 TerminatorInst *Br = OrigBB->getTerminator();
199 assert(Br && Br->getOpcode() == Instruction::Br &&
200 "splitBasicBlock broken!");
201 Br->setOperand(0, ValueMap[CalledMeth->front()]);
203 // Since we are now done with the CallInst, we can finally delete it.
208 bool opt::InlineMethod(CallInst *CI) {
209 assert(CI->getParent() && "CallInst not embeded in BasicBlock!");
210 BasicBlock *PBB = CI->getParent();
212 BasicBlock::iterator CallIt = find(PBB->begin(), PBB->end(), CI);
214 assert(CallIt != PBB->end() &&
215 "CallInst has parent that doesn't contain CallInst?!?");
216 return InlineMethod(CallIt);
219 static inline bool ShouldInlineMethod(const CallInst *CI, const Method *M) {
220 assert(CI->getParent() && CI->getParent()->getParent() &&
221 "Call not embedded into a method!");
223 // Don't inline a recursive call.
224 if (CI->getParent()->getParent() == M) return false;
226 // Don't inline something too big. This is a really crappy heuristic
227 if (M->size() > 3) return false;
229 // Don't inline into something too big. This is a **really** crappy heuristic
230 if (CI->getParent()->getParent()->size() > 10) return false;
232 // Go ahead and try just about anything else.
237 static inline bool DoMethodInlining(BasicBlock *BB) {
238 for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
239 if ((*I)->getOpcode() == Instruction::Call) {
240 // Check to see if we should inline this method
241 CallInst *CI = (CallInst*)*I;
242 Method *M = CI->getCalledMethod();
243 if (ShouldInlineMethod(CI, M))
244 return InlineMethod(I);
250 bool opt::DoMethodInlining(Method *M) {
251 bool Changed = false;
253 // Loop through now and inline instructions a basic block at a time...
254 for (Method::iterator I = M->begin(); I != M->end(); )
255 if (DoMethodInlining(*I)) {
257 // Iterator is now invalidated by new basic blocks inserted