InlineSimple.cpp revision c8b25d40cbec063b1ca99cc1adf794399c6d05c0
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()) 44 continue; // Methods 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)->getInstType() == 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 Method *CurrentMeth = CI->getParent()->getParent(); 74 75 //cerr << "Inlining " << CalledMeth->getName() << " into " 76 // << CurrentMeth->getName() << endl; 77 78 BasicBlock *OrigBB = CI->getParent(); 79 80 // Call splitBasicBlock - The original basic block now ends at the instruction 81 // immediately before the call. The original basic block now ends with an 82 // unconditional branch to NewBB, and NewBB starts with the call instruction. 83 // 84 BasicBlock *NewBB = OrigBB->splitBasicBlock(CIIt); 85 86 // Remove (unlink) the CallInst from the start of the new basic block. 87 NewBB->getInstList().remove(CI); 88 89 // If we have a return value generated by this call, convert it into a PHI 90 // node that gets values from each of the old RET instructions in the original 91 // method. 92 // 93 PHINode *PHI = 0; 94 if (CalledMeth->getReturnType() != Type::VoidTy) { 95 PHI = new PHINode(CalledMeth->getReturnType(), CI->getName()); 96 97 // The PHI node should go at the front of the new basic block to merge all 98 // possible incoming values. 99 // 100 NewBB->getInstList().push_front(PHI); 101 102 // Anything that used the result of the function call should now use the PHI 103 // node as their operand. 104 // 105 CI->replaceAllUsesWith(PHI); 106 } 107 108 // Keep a mapping between the original method's values and the new duplicated 109 // code's values. This includes all of: Method arguments, instruction values, 110 // constant pool entries, and basic blocks. 111 // 112 map<const Value *, Value*> ValueMap; 113 114 // Add the method arguments to the mapping: (start counting at 1 to skip the 115 // method reference itself) 116 // 117 Method::ArgumentListType::const_iterator PTI = 118 CalledMeth->getArgumentList().begin(); 119 for (unsigned a = 1, E = CI->getNumOperands(); a != E; ++a, ++PTI) 120 ValueMap[*PTI] = CI->getOperand(a); 121 122 ValueMap[NewBB] = NewBB; // Returns get converted to reference NewBB 123 124 // Loop over all of the basic blocks in the method, inlining them as 125 // appropriate. Keep track of the first basic block of the method... 126 // 127 for (Method::const_iterator BI = CalledMeth->begin(); 128 BI != CalledMeth->end(); ++BI) { 129 const BasicBlock *BB = *BI; 130 assert(BB->getTerminator() && "BasicBlock doesn't have terminator!?!?"); 131 132 // Create a new basic block to copy instructions into! 133 BasicBlock *IBB = new BasicBlock("", NewBB->getParent()); 134 135 ValueMap[*BI] = IBB; // Add basic block mapping. 136 137 // Make sure to capture the mapping that a return will use... 138 // TODO: This assumes that the RET is returning a value computed in the same 139 // basic block as the return was issued from! 140 // 141 const TerminatorInst *TI = BB->getTerminator(); 142 143 // Loop over all instructions copying them over... 144 Instruction *NewInst; 145 for (BasicBlock::const_iterator II = BB->begin(); 146 II != (BB->end()-1); ++II) { 147 IBB->getInstList().push_back((NewInst = (*II)->clone())); 148 ValueMap[*II] = NewInst; // Add instruction map to value. 149 } 150 151 // Copy over the terminator now... 152 switch (TI->getInstType()) { 153 case Instruction::Ret: { 154 const ReturnInst *RI = (const ReturnInst*)TI; 155 156 if (PHI) { // The PHI node should include this value! 157 assert(RI->getReturnValue() && "Ret should have value!"); 158 assert(RI->getReturnValue()->getType() == PHI->getType() && 159 "Ret value not consistent in method!"); 160 PHI->addIncoming((Value*)RI->getReturnValue(), (BasicBlock*)BB); 161 } 162 163 // Add a branch to the code that was after the original Call. 164 IBB->getInstList().push_back(new BranchInst(NewBB)); 165 break; 166 } 167 case Instruction::Br: 168 IBB->getInstList().push_back(TI->clone()); 169 break; 170 171 default: 172 cerr << "MethodInlining: Don't know how to handle terminator: " << TI; 173 abort(); 174 } 175 } 176 177 178 // Copy over the constant pool... 179 // 180 const ConstantPool &CP = CalledMeth->getConstantPool(); 181 ConstantPool &NewCP = CurrentMeth->getConstantPool(); 182 for (ConstantPool::plane_const_iterator PI = CP.begin(); PI != CP.end(); ++PI){ 183 ConstantPool::PlaneType &Plane = **PI; 184 for (ConstantPool::PlaneType::const_iterator I = Plane.begin(); 185 I != Plane.end(); ++I) { 186 ConstPoolVal *NewVal = (*I)->clone(); // Copy existing constant 187 NewCP.insert(NewVal); // Insert the new copy into local const pool 188 ValueMap[*I] = NewVal; // Keep track of constant value mappings 189 } 190 } 191 192 // Loop over all of the instructions in the method, fixing up operand 193 // references as we go. This uses ValueMap to do all the hard work. 194 // 195 for (Method::const_iterator BI = CalledMeth->begin(); 196 BI != CalledMeth->end(); ++BI) { 197 const BasicBlock *BB = *BI; 198 BasicBlock *NBB = (BasicBlock*)ValueMap[BB]; 199 200 // Loop over all instructions, fixing each one as we find it... 201 // 202 for (BasicBlock::iterator II = NBB->begin(); II != NBB->end(); II++) 203 RemapInstruction(*II, ValueMap); 204 } 205 206 if (PHI) RemapInstruction(PHI, ValueMap); // Fix the PHI node also... 207 208 // Change the branch that used to go to NewBB to branch to the first basic 209 // block of the inlined method. 210 // 211 TerminatorInst *Br = OrigBB->getTerminator(); 212 assert(Br && Br->getInstType() == Instruction::Br && 213 "splitBasicBlock broken!"); 214 Br->setOperand(0, ValueMap[CalledMeth->front()]); 215 216 // Since we are now done with the CallInst, we can finally delete it. 217 delete CI; 218 return true; 219} 220 221bool opt::InlineMethod(CallInst *CI) { 222 assert(CI->getParent() && "CallInst not embeded in BasicBlock!"); 223 BasicBlock *PBB = CI->getParent(); 224 225 BasicBlock::iterator CallIt = find(PBB->begin(), PBB->end(), CI); 226 227 assert(CallIt != PBB->end() && 228 "CallInst has parent that doesn't contain CallInst?!?"); 229 return InlineMethod(CallIt); 230} 231 232static inline bool ShouldInlineMethod(const CallInst *CI, const Method *M) { 233 assert(CI->getParent() && CI->getParent()->getParent() && 234 "Call not embedded into a method!"); 235 236 // Don't inline a recursive call. 237 if (CI->getParent()->getParent() == M) return false; 238 239 // Don't inline something too big. This is a really crappy heuristic 240 if (M->size() > 3) return false; 241 242 // Don't inline into something too big. This is a **really** crappy heuristic 243 if (CI->getParent()->getParent()->size() > 10) return false; 244 245 // Go ahead and try just about anything else. 246 return true; 247} 248 249 250static inline bool DoMethodInlining(BasicBlock *BB) { 251 for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) { 252 if ((*I)->getInstType() == Instruction::Call) { 253 // Check to see if we should inline this method 254 CallInst *CI = (CallInst*)*I; 255 Method *M = CI->getCalledMethod(); 256 if (ShouldInlineMethod(CI, M)) 257 return InlineMethod(I); 258 } 259 } 260 return false; 261} 262 263bool opt::DoMethodInlining(Method *M) { 264 bool Changed = false; 265 266 // Loop through now and inline instructions a basic block at a time... 267 for (Method::iterator I = M->begin(); I != M->end(); ) 268 if (DoMethodInlining(*I)) { 269 Changed = true; 270 // Iterator is now invalidated by new basic blocks inserted 271 I = M->begin(); 272 } else { 273 ++I; 274 } 275 276 return Changed; 277} 278