InlineSimple.cpp revision e9bb2df410f7a22decad9a883f7139d5857c1520
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/iPHINode.h" 27#include "llvm/iOther.h" 28#include <algorithm> 29#include <map> 30 31#include "llvm/Assembly/Writer.h" 32 33using namespace opt; 34 35// RemapInstruction - Convert the instruction operands from referencing the 36// current values into those specified by ValueMap. 37// 38static inline void RemapInstruction(Instruction *I, 39 map<const Value *, Value*> &ValueMap) { 40 41 for (unsigned op = 0, E = I->getNumOperands(); op != E; ++op) { 42 const Value *Op = I->getOperand(op); 43 Value *V = ValueMap[Op]; 44 if (!V && (isa<GlobalValue>(Op) || isa<Constant>(Op))) 45 continue; // Globals and constants don't get relocated 46 47 if (!V) { 48 cerr << "Val = " << endl << Op << "Addr = " << (void*)Op << endl; 49 cerr << "Inst = " << I; 50 } 51 assert(V && "Referenced value not in value map!"); 52 I->setOperand(op, V); 53 } 54} 55 56// InlineMethod - This function forcibly inlines the called method into the 57// basic block of the caller. This returns false if it is not possible to 58// inline this call. The program is still in a well defined state if this 59// occurs though. 60// 61// Note that this only does one level of inlining. For example, if the 62// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now 63// exists in the instruction stream. Similiarly this will inline a recursive 64// method by one level. 65// 66bool opt::InlineMethod(BasicBlock::iterator CIIt) { 67 assert(isa<CallInst>(*CIIt) && "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 = cast<CallInst>(*CIIt); 72 const Method *CalledMeth = CI->getCalledMethod(); 73 if (CalledMeth == 0 || // Can't inline external method or indirect call! 74 CalledMeth->isExternal()) return false; 75 Method *CurrentMeth = CI->getParent()->getParent(); 76 77 //cerr << "Inlining " << CalledMeth->getName() << " into " 78 // << CurrentMeth->getName() << endl; 79 80 BasicBlock *OrigBB = CI->getParent(); 81 82 // Call splitBasicBlock - The original basic block now ends at the instruction 83 // immediately before the call. The original basic block now ends with an 84 // unconditional branch to NewBB, and NewBB starts with the call instruction. 85 // 86 BasicBlock *NewBB = OrigBB->splitBasicBlock(CIIt); 87 88 // Remove (unlink) the CallInst from the start of the new basic block. 89 NewBB->getInstList().remove(CI); 90 91 // If we have a return value generated by this call, convert it into a PHI 92 // node that gets values from each of the old RET instructions in the original 93 // method. 94 // 95 PHINode *PHI = 0; 96 if (CalledMeth->getReturnType() != Type::VoidTy) { 97 PHI = new PHINode(CalledMeth->getReturnType(), CI->getName()); 98 99 // The PHI node should go at the front of the new basic block to merge all 100 // possible incoming values. 101 // 102 NewBB->getInstList().push_front(PHI); 103 104 // Anything that used the result of the function call should now use the PHI 105 // node as their operand. 106 // 107 CI->replaceAllUsesWith(PHI); 108 } 109 110 // Keep a mapping between the original method's values and the new duplicated 111 // code's values. This includes all of: Method arguments, instruction values, 112 // constant pool entries, and basic blocks. 113 // 114 map<const Value *, Value*> ValueMap; 115 116 // Add the method arguments to the mapping: (start counting at 1 to skip the 117 // method reference itself) 118 // 119 Method::ArgumentListType::const_iterator PTI = 120 CalledMeth->getArgumentList().begin(); 121 for (unsigned a = 1, E = CI->getNumOperands(); a != E; ++a, ++PTI) 122 ValueMap[*PTI] = CI->getOperand(a); 123 124 ValueMap[NewBB] = NewBB; // Returns get converted to reference NewBB 125 126 // Loop over all of the basic blocks in the method, inlining them as 127 // appropriate. Keep track of the first basic block of the method... 128 // 129 for (Method::const_iterator BI = CalledMeth->begin(); 130 BI != CalledMeth->end(); ++BI) { 131 const BasicBlock *BB = *BI; 132 assert(BB->getTerminator() && "BasicBlock doesn't have terminator!?!?"); 133 134 // Create a new basic block to copy instructions into! 135 BasicBlock *IBB = new BasicBlock("", NewBB->getParent()); 136 137 ValueMap[BB] = IBB; // Add basic block mapping. 138 139 // Make sure to capture the mapping that a return will use... 140 // TODO: This assumes that the RET is returning a value computed in the same 141 // basic block as the return was issued from! 142 // 143 const TerminatorInst *TI = BB->getTerminator(); 144 145 // Loop over all instructions copying them over... 146 Instruction *NewInst; 147 for (BasicBlock::const_iterator II = BB->begin(); 148 II != (BB->end()-1); ++II) { 149 IBB->getInstList().push_back((NewInst = (*II)->clone())); 150 ValueMap[*II] = NewInst; // Add instruction map to value. 151 } 152 153 // Copy over the terminator now... 154 switch (TI->getOpcode()) { 155 case Instruction::Ret: { 156 const ReturnInst *RI = cast<const ReturnInst>(TI); 157 158 if (PHI) { // The PHI node should include this value! 159 assert(RI->getReturnValue() && "Ret should have value!"); 160 assert(RI->getReturnValue()->getType() == PHI->getType() && 161 "Ret value not consistent in method!"); 162 PHI->addIncoming((Value*)RI->getReturnValue(), cast<BasicBlock>(BB)); 163 } 164 165 // Add a branch to the code that was after the original Call. 166 IBB->getInstList().push_back(new BranchInst(NewBB)); 167 break; 168 } 169 case Instruction::Br: 170 IBB->getInstList().push_back(TI->clone()); 171 break; 172 173 default: 174 cerr << "MethodInlining: Don't know how to handle terminator: " << TI; 175 abort(); 176 } 177 } 178 179 180 // Loop over all of the instructions in the method, fixing up operand 181 // references as we go. This uses ValueMap to do all the hard work. 182 // 183 for (Method::const_iterator BI = CalledMeth->begin(); 184 BI != CalledMeth->end(); ++BI) { 185 const BasicBlock *BB = *BI; 186 BasicBlock *NBB = (BasicBlock*)ValueMap[BB]; 187 188 // Loop over all instructions, fixing each one as we find it... 189 // 190 for (BasicBlock::iterator II = NBB->begin(); II != NBB->end(); II++) 191 RemapInstruction(*II, ValueMap); 192 } 193 194 if (PHI) RemapInstruction(PHI, ValueMap); // Fix the PHI node also... 195 196 // Change the branch that used to go to NewBB to branch to the first basic 197 // block of the inlined method. 198 // 199 TerminatorInst *Br = OrigBB->getTerminator(); 200 assert(Br && Br->getOpcode() == Instruction::Br && 201 "splitBasicBlock broken!"); 202 Br->setOperand(0, ValueMap[CalledMeth->front()]); 203 204 // Since we are now done with the CallInst, we can finally delete it. 205 delete CI; 206 return true; 207} 208 209bool opt::InlineMethod(CallInst *CI) { 210 assert(CI->getParent() && "CallInst not embeded in BasicBlock!"); 211 BasicBlock *PBB = CI->getParent(); 212 213 BasicBlock::iterator CallIt = find(PBB->begin(), PBB->end(), CI); 214 215 assert(CallIt != PBB->end() && 216 "CallInst has parent that doesn't contain CallInst?!?"); 217 return InlineMethod(CallIt); 218} 219 220static inline bool ShouldInlineMethod(const CallInst *CI, const Method *M) { 221 assert(CI->getParent() && CI->getParent()->getParent() && 222 "Call not embedded into a method!"); 223 224 // Don't inline a recursive call. 225 if (CI->getParent()->getParent() == M) return false; 226 227 // Don't inline something too big. This is a really crappy heuristic 228 if (M->size() > 3) return false; 229 230 // Don't inline into something too big. This is a **really** crappy heuristic 231 if (CI->getParent()->getParent()->size() > 10) return false; 232 233 // Go ahead and try just about anything else. 234 return true; 235} 236 237 238static inline bool DoMethodInlining(BasicBlock *BB) { 239 for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) { 240 if (CallInst *CI = dyn_cast<CallInst>(*I)) { 241 // Check to see if we should inline this method 242 Method *M = CI->getCalledMethod(); 243 if (M && ShouldInlineMethod(CI, M)) 244 return InlineMethod(I); 245 } 246 } 247 return false; 248} 249 250bool opt::MethodInlining::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