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/iPHINode.h"
27 #include "llvm/iOther.h"
33 #include "llvm/Assembly/Writer.h"
37 // RemapInstruction - Convert the instruction operands from referencing the
38 // current values into those specified by ValueMap.
40 static inline void RemapInstruction(Instruction *I,
41 std::map<const Value *, Value*> &ValueMap) {
43 for (unsigned op = 0, E = I->getNumOperands(); op != E; ++op) {
44 const Value *Op = I->getOperand(op);
45 Value *V = ValueMap[Op];
46 if (!V && (isa<GlobalValue>(Op) || isa<Constant>(Op)))
47 continue; // Globals and constants don't get relocated
50 cerr << "Val = \n" << Op << "Addr = " << (void*)Op;
51 cerr << "\nInst = " << I;
53 assert(V && "Referenced value not in value map!");
58 // InlineMethod - This function forcibly inlines the called method into the
59 // basic block of the caller. This returns false if it is not possible to
60 // inline this call. The program is still in a well defined state if this
63 // Note that this only does one level of inlining. For example, if the
64 // instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
65 // exists in the instruction stream. Similiarly this will inline a recursive
66 // method by one level.
68 bool opt::InlineMethod(BasicBlock::iterator CIIt) {
69 assert(isa<CallInst>(*CIIt) && "InlineMethod only works on CallInst nodes!");
70 assert((*CIIt)->getParent() && "Instruction not embedded in basic block!");
71 assert((*CIIt)->getParent()->getParent() && "Instruction not in method!");
73 CallInst *CI = cast<CallInst>(*CIIt);
74 const Method *CalledMeth = CI->getCalledMethod();
75 if (CalledMeth == 0 || // Can't inline external method or indirect call!
76 CalledMeth->isExternal()) return false;
78 //cerr << "Inlining " << CalledMeth->getName() << " into "
79 // << CurrentMeth->getName() << "\n";
81 BasicBlock *OrigBB = CI->getParent();
83 // Call splitBasicBlock - The original basic block now ends at the instruction
84 // immediately before the call. The original basic block now ends with an
85 // unconditional branch to NewBB, and NewBB starts with the call instruction.
87 BasicBlock *NewBB = OrigBB->splitBasicBlock(CIIt);
89 // Remove (unlink) the CallInst from the start of the new basic block.
90 NewBB->getInstList().remove(CI);
92 // If we have a return value generated by this call, convert it into a PHI
93 // node that gets values from each of the old RET instructions in the original
97 if (CalledMeth->getReturnType() != Type::VoidTy) {
98 PHI = new PHINode(CalledMeth->getReturnType(), CI->getName());
100 // The PHI node should go at the front of the new basic block to merge all
101 // possible incoming values.
103 NewBB->getInstList().push_front(PHI);
105 // Anything that used the result of the function call should now use the PHI
106 // node as their operand.
108 CI->replaceAllUsesWith(PHI);
111 // Keep a mapping between the original method's values and the new duplicated
112 // code's values. This includes all of: Method arguments, instruction values,
113 // constant pool entries, and basic blocks.
115 std::map<const Value *, Value*> ValueMap;
117 // Add the method arguments to the mapping: (start counting at 1 to skip the
118 // method reference itself)
120 Method::ArgumentListType::const_iterator PTI =
121 CalledMeth->getArgumentList().begin();
122 for (unsigned a = 1, E = CI->getNumOperands(); a != E; ++a, ++PTI)
123 ValueMap[*PTI] = CI->getOperand(a);
125 ValueMap[NewBB] = NewBB; // Returns get converted to reference NewBB
127 // Loop over all of the basic blocks in the method, inlining them as
128 // appropriate. Keep track of the first basic block of the method...
130 for (Method::const_iterator BI = CalledMeth->begin();
131 BI != CalledMeth->end(); ++BI) {
132 const BasicBlock *BB = *BI;
133 assert(BB->getTerminator() && "BasicBlock doesn't have terminator!?!?");
135 // Create a new basic block to copy instructions into!
136 BasicBlock *IBB = new BasicBlock("", NewBB->getParent());
138 ValueMap[BB] = IBB; // Add basic block mapping.
140 // Make sure to capture the mapping that a return will use...
141 // TODO: This assumes that the RET is returning a value computed in the same
142 // basic block as the return was issued from!
144 const TerminatorInst *TI = BB->getTerminator();
146 // Loop over all instructions copying them over...
147 Instruction *NewInst;
148 for (BasicBlock::const_iterator II = BB->begin();
149 II != (BB->end()-1); ++II) {
150 IBB->getInstList().push_back((NewInst = (*II)->clone()));
151 ValueMap[*II] = NewInst; // Add instruction map to value.
154 // Copy over the terminator now...
155 switch (TI->getOpcode()) {
156 case Instruction::Ret: {
157 const ReturnInst *RI = cast<const ReturnInst>(TI);
159 if (PHI) { // The PHI node should include this value!
160 assert(RI->getReturnValue() && "Ret should have value!");
161 assert(RI->getReturnValue()->getType() == PHI->getType() &&
162 "Ret value not consistent in method!");
163 PHI->addIncoming((Value*)RI->getReturnValue(), cast<BasicBlock>(BB));
166 // Add a branch to the code that was after the original Call.
167 IBB->getInstList().push_back(new BranchInst(NewBB));
170 case Instruction::Br:
171 IBB->getInstList().push_back(TI->clone());
175 cerr << "MethodInlining: Don't know how to handle terminator: " << TI;
181 // Loop over all of the instructions in the method, fixing up operand
182 // references as we go. This uses ValueMap to do all the hard work.
184 for (Method::const_iterator BI = CalledMeth->begin();
185 BI != CalledMeth->end(); ++BI) {
186 const BasicBlock *BB = *BI;
187 BasicBlock *NBB = (BasicBlock*)ValueMap[BB];
189 // Loop over all instructions, fixing each one as we find it...
191 for (BasicBlock::iterator II = NBB->begin(); II != NBB->end(); II++)
192 RemapInstruction(*II, ValueMap);
195 if (PHI) RemapInstruction(PHI, ValueMap); // Fix the PHI node also...
197 // Change the branch that used to go to NewBB to branch to the first basic
198 // block of the inlined method.
200 TerminatorInst *Br = OrigBB->getTerminator();
201 assert(Br && Br->getOpcode() == Instruction::Br &&
202 "splitBasicBlock broken!");
203 Br->setOperand(0, ValueMap[CalledMeth->front()]);
205 // Since we are now done with the CallInst, we can finally delete it.
210 bool opt::InlineMethod(CallInst *CI) {
211 assert(CI->getParent() && "CallInst not embeded in BasicBlock!");
212 BasicBlock *PBB = CI->getParent();
214 BasicBlock::iterator CallIt = find(PBB->begin(), PBB->end(), CI);
216 assert(CallIt != PBB->end() &&
217 "CallInst has parent that doesn't contain CallInst?!?");
218 return InlineMethod(CallIt);
221 static inline bool ShouldInlineMethod(const CallInst *CI, const Method *M) {
222 assert(CI->getParent() && CI->getParent()->getParent() &&
223 "Call not embedded into a method!");
225 // Don't inline a recursive call.
226 if (CI->getParent()->getParent() == M) return false;
228 // Don't inline something too big. This is a really crappy heuristic
229 if (M->size() > 3) return false;
231 // Don't inline into something too big. This is a **really** crappy heuristic
232 if (CI->getParent()->getParent()->size() > 10) return false;
234 // Go ahead and try just about anything else.
239 static inline bool DoMethodInlining(BasicBlock *BB) {
240 for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
241 if (CallInst *CI = dyn_cast<CallInst>(*I)) {
242 // Check to see if we should inline this method
243 Method *M = CI->getCalledMethod();
244 if (M && ShouldInlineMethod(CI, M))
245 return InlineMethod(I);
251 bool opt::MethodInlining::doMethodInlining(Method *M) {
252 bool Changed = false;
254 // Loop through now and inline instructions a basic block at a time...
255 for (Method::iterator I = M->begin(); I != M->end(); )
256 if (DoMethodInlining(*I)) {
258 // Iterator is now invalidated by new basic blocks inserted