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; const Value *Op = I->getOperand(op); ++op) {
41 Value *V = ValueMap[Op];
42 if (!V && Op->isMethod())
43 continue; // Methods don't get relocated
46 cerr << "Val = " << endl << Op << "Addr = " << (void*)Op << endl;
47 cerr << "Inst = " << I;
49 assert(V && "Referenced value not in value map!");
54 // InlineMethod - This function forcibly inlines the called method into the
55 // basic block of the caller. This returns false if it is not possible to
56 // inline this call. The program is still in a well defined state if this
59 // Note that this only does one level of inlining. For example, if the
60 // instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
61 // exists in the instruction stream. Similiarly this will inline a recursive
62 // method by one level.
64 bool opt::InlineMethod(BasicBlock::iterator CIIt) {
65 assert((*CIIt)->getInstType() == Instruction::Call &&
66 "InlineMethod only works on CallInst nodes!");
67 assert((*CIIt)->getParent() && "Instruction not embedded in basic block!");
68 assert((*CIIt)->getParent()->getParent() && "Instruction not in method!");
70 CallInst *CI = (CallInst*)*CIIt;
71 const Method *CalledMeth = CI->getCalledMethod();
72 Method *CurrentMeth = CI->getParent()->getParent();
74 //cerr << "Inlining " << CalledMeth->getName() << " into "
75 // << CurrentMeth->getName() << endl;
77 BasicBlock *OrigBB = CI->getParent();
79 // Call splitBasicBlock - The original basic block now ends at the instruction
80 // immediately before the call. The original basic block now ends with an
81 // unconditional branch to NewBB, and NewBB starts with the call instruction.
83 BasicBlock *NewBB = OrigBB->splitBasicBlock(CIIt);
85 // Remove (unlink) the CallInst from the start of the new basic block.
86 NewBB->getInstList().remove(CI);
88 // If we have a return value generated by this call, convert it into a PHI
89 // node that gets values from each of the old RET instructions in the original
93 if (CalledMeth->getReturnType() != Type::VoidTy) {
94 PHI = new PHINode(CalledMeth->getReturnType(), CI->getName());
96 // The PHI node should go at the front of the new basic block to merge all
97 // possible incoming values.
99 NewBB->getInstList().push_front(PHI);
101 // Anything that used the result of the function call should now use the PHI
102 // node as their operand.
104 CI->replaceAllUsesWith(PHI);
107 // Keep a mapping between the original method's values and the new duplicated
108 // code's values. This includes all of: Method arguments, instruction values,
109 // constant pool entries, and basic blocks.
111 map<const Value *, Value*> ValueMap;
113 // Add the method arguments to the mapping: (start counting at 1 to skip the
114 // method reference itself)
116 Method::ArgumentListType::const_iterator PTI =
117 CalledMeth->getArgumentList().begin();
118 for (unsigned a = 1; Value *Operand = CI->getOperand(a); ++a, ++PTI) {
119 ValueMap[*PTI] = Operand;
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->getInstType()) {
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 // Copy over the constant pool...
181 const ConstantPool &CP = CalledMeth->getConstantPool();
182 ConstantPool &NewCP = CurrentMeth->getConstantPool();
183 for (ConstantPool::plane_const_iterator PI = CP.begin(); PI != CP.end(); ++PI){
184 ConstantPool::PlaneType &Plane = **PI;
185 for (ConstantPool::PlaneType::const_iterator I = Plane.begin();
186 I != Plane.end(); ++I) {
187 ConstPoolVal *NewVal = (*I)->clone(); // Copy existing constant
188 NewCP.insert(NewVal); // Insert the new copy into local const pool
189 ValueMap[*I] = NewVal; // Keep track of constant value mappings
193 // Loop over all of the instructions in the method, fixing up operand
194 // references as we go. This uses ValueMap to do all the hard work.
196 for (Method::const_iterator BI = CalledMeth->begin();
197 BI != CalledMeth->end(); ++BI) {
198 const BasicBlock *BB = *BI;
199 BasicBlock *NBB = (BasicBlock*)ValueMap[BB];
201 // Loop over all instructions, fixing each one as we find it...
203 for (BasicBlock::iterator II = NBB->begin(); II != NBB->end(); II++)
204 RemapInstruction(*II, ValueMap);
207 if (PHI) RemapInstruction(PHI, ValueMap); // Fix the PHI node also...
209 // Change the branch that used to go to NewBB to branch to the first basic
210 // block of the inlined method.
212 TerminatorInst *Br = OrigBB->getTerminator();
213 assert(Br && Br->getInstType() == Instruction::Br &&
214 "splitBasicBlock broken!");
215 Br->setOperand(0, ValueMap[CalledMeth->front()]);
217 // Since we are now done with the CallInst, we can finally delete it.
222 bool opt::InlineMethod(CallInst *CI) {
223 assert(CI->getParent() && "CallInst not embeded in BasicBlock!");
224 BasicBlock *PBB = CI->getParent();
226 BasicBlock::iterator CallIt = find(PBB->begin(), PBB->end(), CI);
228 assert(CallIt != PBB->end() &&
229 "CallInst has parent that doesn't contain CallInst?!?");
230 return InlineMethod(CallIt);
233 static inline bool ShouldInlineMethod(const CallInst *CI, const Method *M) {
234 assert(CI->getParent() && CI->getParent()->getParent() &&
235 "Call not embedded into a method!");
237 // Don't inline a recursive call.
238 if (CI->getParent()->getParent() == M) return false;
240 // Don't inline something too big. This is a really crappy heuristic
241 if (M->size() > 3) return false;
243 // Don't inline into something too big. This is a **really** crappy heuristic
244 if (CI->getParent()->getParent()->size() > 10) return false;
246 // Go ahead and try just about anything else.
251 static inline bool DoMethodInlining(BasicBlock *BB) {
252 for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
253 if ((*I)->getInstType() == Instruction::Call) {
254 // Check to see if we should inline this method
255 CallInst *CI = (CallInst*)*I;
256 Method *M = CI->getCalledMethod();
257 if (ShouldInlineMethod(CI, M))
258 return InlineMethod(I);
264 bool opt::DoMethodInlining(Method *M) {
265 bool Changed = false;
267 // Loop through now and inline instructions a basic block at a time...
268 for (Method::iterator I = M->begin(); I != M->end(); )
269 if (DoMethodInlining(*I)) {
271 // Iterator is now invalidated by new basic blocks inserted