InlineSimple.cpp revision 78721d54186cad8db817bad13360dad286524945
1//===- MethodInlining.cpp - Code to perform method inlining ---------------===// 2// 3// This file implements inlining of methods. 4// 5// Specifically, this: 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 10// 11// Notice that: 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. 16// 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 19// 20//===----------------------------------------------------------------------===// 21 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" 27#include <algorithm> 28#include <map> 29 30#include "llvm/Assembly/Writer.h" 31 32using namespace opt; 33 34// RemapInstruction - Convert the instruction operands from referencing the 35// current values into those specified by ValueMap. 36// 37static inline void RemapInstruction(Instruction *I, 38 map<const Value *, Value*> &ValueMap) { 39 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 45 46 if (!V) { 47 cerr << "Val = " << endl << Op << "Addr = " << (void*)Op << endl; 48 cerr << "Inst = " << I; 49 } 50 assert(V && "Referenced value not in value map!"); 51 I->setOperand(op, V); 52 } 53} 54 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 58// occurs though. 59// 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. 64// 65bool 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!"); 70 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(); 75 76 //cerr << "Inlining " << CalledMeth->getName() << " into " 77 // << CurrentMeth->getName() << endl; 78 79 BasicBlock *OrigBB = CI->getParent(); 80 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. 84 // 85 BasicBlock *NewBB = OrigBB->splitBasicBlock(CIIt); 86 87 // Remove (unlink) the CallInst from the start of the new basic block. 88 NewBB->getInstList().remove(CI); 89 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 92 // method. 93 // 94 PHINode *PHI = 0; 95 if (CalledMeth->getReturnType() != Type::VoidTy) { 96 PHI = new PHINode(CalledMeth->getReturnType(), CI->getName()); 97 98 // The PHI node should go at the front of the new basic block to merge all 99 // possible incoming values. 100 // 101 NewBB->getInstList().push_front(PHI); 102 103 // Anything that used the result of the function call should now use the PHI 104 // node as their operand. 105 // 106 CI->replaceAllUsesWith(PHI); 107 } 108 109 // 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. 112 // 113 map<const Value *, Value*> ValueMap; 114 115 // Add the method arguments to the mapping: (start counting at 1 to skip the 116 // method reference itself) 117 // 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); 122 123 ValueMap[NewBB] = NewBB; // Returns get converted to reference NewBB 124 125 // 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... 127 // 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!?!?"); 132 133 // Create a new basic block to copy instructions into! 134 BasicBlock *IBB = new BasicBlock("", NewBB->getParent()); 135 136 ValueMap[*BI] = IBB; // Add basic block mapping. 137 138 // 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! 141 // 142 const TerminatorInst *TI = BB->getTerminator(); 143 144 // 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. 150 } 151 152 // Copy over the terminator now... 153 switch (TI->getOpcode()) { 154 case Instruction::Ret: { 155 const ReturnInst *RI = (const ReturnInst*)TI; 156 157 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); 162 } 163 164 // Add a branch to the code that was after the original Call. 165 IBB->getInstList().push_back(new BranchInst(NewBB)); 166 break; 167 } 168 case Instruction::Br: 169 IBB->getInstList().push_back(TI->clone()); 170 break; 171 172 default: 173 cerr << "MethodInlining: Don't know how to handle terminator: " << TI; 174 abort(); 175 } 176 } 177 178 179 // 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. 181 // 182 for (Method::const_iterator BI = CalledMeth->begin(); 183 BI != CalledMeth->end(); ++BI) { 184 const BasicBlock *BB = *BI; 185 BasicBlock *NBB = (BasicBlock*)ValueMap[BB]; 186 187 // Loop over all instructions, fixing each one as we find it... 188 // 189 for (BasicBlock::iterator II = NBB->begin(); II != NBB->end(); II++) 190 RemapInstruction(*II, ValueMap); 191 } 192 193 if (PHI) RemapInstruction(PHI, ValueMap); // Fix the PHI node also... 194 195 // Change the branch that used to go to NewBB to branch to the first basic 196 // block of the inlined method. 197 // 198 TerminatorInst *Br = OrigBB->getTerminator(); 199 assert(Br && Br->getOpcode() == Instruction::Br && 200 "splitBasicBlock broken!"); 201 Br->setOperand(0, ValueMap[CalledMeth->front()]); 202 203 // Since we are now done with the CallInst, we can finally delete it. 204 delete CI; 205 return true; 206} 207 208bool opt::InlineMethod(CallInst *CI) { 209 assert(CI->getParent() && "CallInst not embeded in BasicBlock!"); 210 BasicBlock *PBB = CI->getParent(); 211 212 BasicBlock::iterator CallIt = find(PBB->begin(), PBB->end(), CI); 213 214 assert(CallIt != PBB->end() && 215 "CallInst has parent that doesn't contain CallInst?!?"); 216 return InlineMethod(CallIt); 217} 218 219static inline bool ShouldInlineMethod(const CallInst *CI, const Method *M) { 220 assert(CI->getParent() && CI->getParent()->getParent() && 221 "Call not embedded into a method!"); 222 223 // Don't inline a recursive call. 224 if (CI->getParent()->getParent() == M) return false; 225 226 // Don't inline something too big. This is a really crappy heuristic 227 if (M->size() > 3) return false; 228 229 // Don't inline into something too big. This is a **really** crappy heuristic 230 if (CI->getParent()->getParent()->size() > 10) return false; 231 232 // Go ahead and try just about anything else. 233 return true; 234} 235 236 237static 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); 245 } 246 } 247 return false; 248} 249 250bool opt::DoMethodInlining(Method *M) { 251 bool Changed = false; 252 253 // 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)) { 256 Changed = true; 257 // Iterator is now invalidated by new basic blocks inserted 258 I = M->begin(); 259 } else { 260 ++I; 261 } 262 263 return Changed; 264} 265