InlineSimple.cpp revision 009505452b713ed2e3a8e99c5545a6e721c65495
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/Module.h" 23#include "llvm/Method.h" 24#include "llvm/BasicBlock.h" 25#include "llvm/iTerminators.h" 26#include "llvm/iOther.h" 27#include "llvm/Opt/AllOpts.h" 28#include <algorithm> 29#include <map> 30 31#include "llvm/Assembly/Writer.h" 32 33// RemapInstruction - Convert the instruction operands from referencing the 34// current values into those specified by ValueMap. 35// 36static inline void RemapInstruction(Instruction *I, 37 map<const Value *, Value*> &ValueMap) { 38 39 for (unsigned op = 0; const Value *Op = I->getOperand(op); op++) { 40 Value *V = ValueMap[Op]; 41 if (!V && Op->getValueType() == Value::MethodVal) 42 continue; // Methods don't get relocated 43 44 if (!V) { 45 cerr << "Val = " << endl << Op << "Addr = " << (void*)Op << endl; 46 cerr << "Inst = " << I; 47 } 48 assert(V && "Referenced value not in value map!"); 49 I->setOperand(op, V); 50 } 51} 52 53// InlineMethod - This function forcibly inlines the called method into the 54// basic block of the caller. This returns false if it is not possible to 55// inline this call. The program is still in a well defined state if this 56// occurs though. 57// 58// Note that this only does one level of inlining. For example, if the 59// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now 60// exists in the instruction stream. Similiarly this will inline a recursive 61// method by one level. 62// 63bool InlineMethod(BasicBlock::InstListType::iterator CIIt) { 64 assert((*CIIt)->getInstType() == Instruction::Call && 65 "InlineMethod only works on CallInst nodes!"); 66 assert((*CIIt)->getParent() && "Instruction not embedded in basic block!"); 67 assert((*CIIt)->getParent()->getParent() && "Instruction not in method!"); 68 69 CallInst *CI = (CallInst*)*CIIt; 70 const Method *CalledMeth = CI->getCalledMethod(); 71 Method *CurrentMeth = CI->getParent()->getParent(); 72 73 //cerr << "Inlining " << CalledMeth->getName() << " into " 74 // << CurrentMeth->getName() << endl; 75 76 BasicBlock *OrigBB = CI->getParent(); 77 78 // Call splitBasicBlock - The original basic block now ends at the instruction 79 // immediately before the call. The original basic block now ends with an 80 // unconditional branch to NewBB, and NewBB starts with the call instruction. 81 // 82 BasicBlock *NewBB = OrigBB->splitBasicBlock(CIIt); 83 84 // Remove (unlink) the CallInst from the start of the new basic block. 85 NewBB->getInstList().remove(CI); 86 87 // If we have a return value generated by this call, convert it into a PHI 88 // node that gets values from each of the old RET instructions in the original 89 // method. 90 // 91 PHINode *PHI = 0; 92 if (CalledMeth->getReturnType() != Type::VoidTy) { 93 PHI = new PHINode(CalledMeth->getReturnType(), CI->getName()); 94 95 // The PHI node should go at the front of the new basic block to merge all 96 // possible incoming values. 97 // 98 NewBB->getInstList().push_front(PHI); 99 100 // Anything that used the result of the function call should now use the PHI 101 // node as their operand. 102 // 103 CI->replaceAllUsesWith(PHI); 104 } 105 106 // Keep a mapping between the original method's values and the new duplicated 107 // code's values. This includes all of: Method arguments, instruction values, 108 // constant pool entries, and basic blocks. 109 // 110 map<const Value *, Value*> ValueMap; 111 112 // Add the method arguments to the mapping: (start counting at 1 to skip the 113 // method reference itself) 114 // 115 Method::ArgumentListType::const_iterator PTI = 116 CalledMeth->getArgumentList().begin(); 117 for (unsigned a = 1; Value *Operand = CI->getOperand(a); ++a, ++PTI) { 118 ValueMap[*PTI] = Operand; 119 } 120 121 122 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::BasicBlocksType::const_iterator BI = 128 CalledMeth->getBasicBlocks().begin(); 129 BI != CalledMeth->getBasicBlocks().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::InstListType::const_iterator II = BB->getInstList().begin(); 147 II != (BB->getInstList().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->getInstType()) { 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()); 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 // Copy over the constant pool... 180 // 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 190 } 191 } 192 193 // 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. 195 // 196 for (Method::BasicBlocksType::const_iterator BI = 197 CalledMeth->getBasicBlocks().begin(); 198 BI != CalledMeth->getBasicBlocks().end(); BI++) { 199 const BasicBlock *BB = *BI; 200 BasicBlock *NBB = (BasicBlock*)ValueMap[BB]; 201 202 // Loop over all instructions, fixing each one as we find it... 203 // 204 for (BasicBlock::InstListType::iterator II = NBB->getInstList().begin(); 205 II != NBB->getInstList().end(); II++) 206 RemapInstruction(*II, ValueMap); 207 } 208 209 if (PHI) RemapInstruction(PHI, ValueMap); // Fix the PHI node also... 210 211 // Change the branch that used to go to NewBB to branch to the first basic 212 // block of the inlined method. 213 // 214 TerminatorInst *Br = OrigBB->getTerminator(); 215 assert(Br && Br->getInstType() == Instruction::Br && 216 "splitBasicBlock broken!"); 217 Br->setOperand(0, ValueMap[CalledMeth->getBasicBlocks().front()]); 218 219 // Since we are now done with the CallInst, we can finally delete it. 220 delete CI; 221 return true; 222} 223 224bool InlineMethod(CallInst *CI) { 225 assert(CI->getParent() && "CallInst not embeded in BasicBlock!"); 226 BasicBlock *PBB = CI->getParent(); 227 228 BasicBlock::InstListType::iterator CallIt = find(PBB->getInstList().begin(), 229 PBB->getInstList().end(), 230 CI); 231 assert(CallIt != PBB->getInstList().end() && 232 "CallInst has parent that doesn't contain CallInst?!?"); 233 return InlineMethod(CallIt); 234} 235 236static inline bool ShouldInlineMethod(const CallInst *CI, const Method *M) { 237 assert(CI->getParent() && CI->getParent()->getParent() && 238 "Call not embedded into a method!"); 239 240 // Don't inline a recursive call. 241 if (CI->getParent()->getParent() == M) return false; 242 243 // Don't inline something too big. This is a really crappy heuristic 244 if (M->getBasicBlocks().size() > 3) return false; 245 246 // Don't inline into something too big. This is a **really** crappy heuristic 247 if (CI->getParent()->getParent()->getBasicBlocks().size() > 10) return false; 248 249 // Go ahead and try just about anything else. 250 return true; 251} 252 253 254static inline bool DoMethodInlining(BasicBlock *BB) { 255 for (BasicBlock::InstListType::iterator I = BB->getInstList().begin(); 256 I != BB->getInstList().end(); I++) { 257 if ((*I)->getInstType() == Instruction::Call) { 258 // Check to see if we should inline this method 259 CallInst *CI = (CallInst*)*I; 260 Method *M = CI->getCalledMethod(); 261 if (ShouldInlineMethod(CI, M)) 262 return InlineMethod(I); 263 } 264 } 265 return false; 266} 267 268bool DoMethodInlining(Method *M) { 269 Method::BasicBlocksType &BBs = M->getBasicBlocks(); 270 bool Changed = false; 271 272 // Loop through now and inline instructions a basic block at a time... 273 for (Method::BasicBlocksType::iterator I = BBs.begin(); I != BBs.end(); ) 274 if (DoMethodInlining(*I)) { 275 Changed = true; 276 // Iterator is now invalidated by new basic blocks inserted 277 I = BBs.begin(); 278 } else { 279 ++I; 280 } 281 282 return Changed; 283} 284