InlineFunction.cpp revision 727d1dd58793447e83ade712f0e58172f156edcf
1//===- InlineFunction.cpp - Code to perform function inlining -------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by the LLVM research group and is distributed under 6// the University of Illinois Open Source License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file implements inlining of a function into a call site, resolving 11// parameters and the return value as appropriate. 12// 13//===----------------------------------------------------------------------===// 14 15#include "llvm/Transforms/Utils/Cloning.h" 16#include "llvm/Constants.h" 17#include "llvm/DerivedTypes.h" 18#include "llvm/Module.h" 19#include "llvm/Instructions.h" 20#include "llvm/Intrinsics.h" 21#include "llvm/Support/CallSite.h" 22using namespace llvm; 23 24bool llvm::InlineFunction(CallInst *CI) { return InlineFunction(CallSite(CI)); } 25bool llvm::InlineFunction(InvokeInst *II) {return InlineFunction(CallSite(II));} 26 27/// HandleInlinedInvoke - If we inlined an invoke site, we need to convert calls 28/// in the body of the inlined function into invokes and turn unwind 29/// instructions into branches to the invoke unwind dest. 30/// 31/// II is the invoke instruction begin inlined. FirstNewBlock is the first 32/// block of the inlined code (the last block is the end of the function), 33/// and InlineCodeInfo is information about the code that got inlined. 34static void HandleInlinedInvoke(InvokeInst *II, BasicBlock *FirstNewBlock, 35 ClonedCodeInfo &InlinedCodeInfo) { 36 BasicBlock *InvokeDest = II->getUnwindDest(); 37 std::vector<Value*> InvokeDestPHIValues; 38 39 // If there are PHI nodes in the unwind destination block, we need to 40 // keep track of which values came into them from this invoke, then remove 41 // the entry for this block. 42 BasicBlock *InvokeBlock = II->getParent(); 43 for (BasicBlock::iterator I = InvokeDest->begin(); isa<PHINode>(I); ++I) { 44 PHINode *PN = cast<PHINode>(I); 45 // Save the value to use for this edge. 46 InvokeDestPHIValues.push_back(PN->getIncomingValueForBlock(InvokeBlock)); 47 } 48 49 Function *Caller = FirstNewBlock->getParent(); 50 51 // The inlined code is currently at the end of the function, scan from the 52 // start of the inlined code to its end, checking for stuff we need to 53 // rewrite. 54 if (InlinedCodeInfo.ContainsCalls || InlinedCodeInfo.ContainsUnwinds) { 55 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 56 BB != E; ++BB) { 57 if (InlinedCodeInfo.ContainsCalls) { 58 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ){ 59 Instruction *I = BBI++; 60 61 // We only need to check for function calls: inlined invoke 62 // instructions require no special handling. 63 if (!isa<CallInst>(I)) continue; 64 CallInst *CI = cast<CallInst>(I); 65 66 // If this is an intrinsic function call, don't convert it to an 67 // invoke. 68 if (CI->getCalledFunction() && 69 CI->getCalledFunction()->getIntrinsicID()) 70 continue; 71 72 // Convert this function call into an invoke instruction. 73 // First, split the basic block. 74 BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc"); 75 76 // Next, create the new invoke instruction, inserting it at the end 77 // of the old basic block. 78 InvokeInst *II = 79 new InvokeInst(CI->getCalledValue(), Split, InvokeDest, 80 std::vector<Value*>(CI->op_begin()+1, CI->op_end()), 81 CI->getName(), BB->getTerminator()); 82 II->setCallingConv(CI->getCallingConv()); 83 84 // Make sure that anything using the call now uses the invoke! 85 CI->replaceAllUsesWith(II); 86 87 // Delete the unconditional branch inserted by splitBasicBlock 88 BB->getInstList().pop_back(); 89 Split->getInstList().pop_front(); // Delete the original call 90 91 // Update any PHI nodes in the exceptional block to indicate that 92 // there is now a new entry in them. 93 unsigned i = 0; 94 for (BasicBlock::iterator I = InvokeDest->begin(); 95 isa<PHINode>(I); ++I, ++i) { 96 PHINode *PN = cast<PHINode>(I); 97 PN->addIncoming(InvokeDestPHIValues[i], BB); 98 } 99 100 // This basic block is now complete, start scanning the next one. 101 break; 102 } 103 } 104 105 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 106 // An UnwindInst requires special handling when it gets inlined into an 107 // invoke site. Once this happens, we know that the unwind would cause 108 // a control transfer to the invoke exception destination, so we can 109 // transform it into a direct branch to the exception destination. 110 new BranchInst(InvokeDest, UI); 111 112 // Delete the unwind instruction! 113 UI->getParent()->getInstList().pop_back(); 114 115 // Update any PHI nodes in the exceptional block to indicate that 116 // there is now a new entry in them. 117 unsigned i = 0; 118 for (BasicBlock::iterator I = InvokeDest->begin(); 119 isa<PHINode>(I); ++I, ++i) { 120 PHINode *PN = cast<PHINode>(I); 121 PN->addIncoming(InvokeDestPHIValues[i], BB); 122 } 123 } 124 } 125 } 126 127 // Now that everything is happy, we have one final detail. The PHI nodes in 128 // the exception destination block still have entries due to the original 129 // invoke instruction. Eliminate these entries (which might even delete the 130 // PHI node) now. 131 InvokeDest->removePredecessor(II->getParent()); 132} 133 134 135// InlineFunction - This function inlines the called function into the basic 136// block of the caller. This returns false if it is not possible to inline this 137// call. The program is still in a well defined state if this occurs though. 138// 139// Note that this only does one level of inlining. For example, if the 140// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now 141// exists in the instruction stream. Similiarly this will inline a recursive 142// function by one level. 143// 144bool llvm::InlineFunction(CallSite CS) { 145 Instruction *TheCall = CS.getInstruction(); 146 assert(TheCall->getParent() && TheCall->getParent()->getParent() && 147 "Instruction not in function!"); 148 149 const Function *CalledFunc = CS.getCalledFunction(); 150 if (CalledFunc == 0 || // Can't inline external function or indirect 151 CalledFunc->isExternal() || // call, or call to a vararg function! 152 CalledFunc->getFunctionType()->isVarArg()) return false; 153 154 155 // If the call to the callee is a non-tail call, we must clear the 'tail' 156 // flags on any calls that we inline. 157 bool MustClearTailCallFlags = 158 isa<CallInst>(TheCall) && !cast<CallInst>(TheCall)->isTailCall(); 159 160 BasicBlock *OrigBB = TheCall->getParent(); 161 Function *Caller = OrigBB->getParent(); 162 163 // Get an iterator to the last basic block in the function, which will have 164 // the new function inlined after it. 165 // 166 Function::iterator LastBlock = &Caller->back(); 167 168 // Make sure to capture all of the return instructions from the cloned 169 // function. 170 std::vector<ReturnInst*> Returns; 171 ClonedCodeInfo InlinedFunctionInfo; 172 { // Scope to destroy ValueMap after cloning. 173 // Calculate the vector of arguments to pass into the function cloner... 174 std::map<const Value*, Value*> ValueMap; 175 assert(std::distance(CalledFunc->arg_begin(), CalledFunc->arg_end()) == 176 std::distance(CS.arg_begin(), CS.arg_end()) && 177 "No varargs calls can be inlined!"); 178 179 CallSite::arg_iterator AI = CS.arg_begin(); 180 for (Function::const_arg_iterator I = CalledFunc->arg_begin(), 181 E = CalledFunc->arg_end(); I != E; ++I, ++AI) 182 ValueMap[I] = *AI; 183 184 // Clone the entire body of the callee into the caller. 185 CloneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i", 186 &InlinedFunctionInfo); 187 } 188 189 // Remember the first block that is newly cloned over. 190 Function::iterator FirstNewBlock = LastBlock; ++FirstNewBlock; 191 192 // If there are any alloca instructions in the block that used to be the entry 193 // block for the callee, move them to the entry block of the caller. First 194 // calculate which instruction they should be inserted before. We insert the 195 // instructions at the end of the current alloca list. 196 // 197 { 198 BasicBlock::iterator InsertPoint = Caller->begin()->begin(); 199 for (BasicBlock::iterator I = FirstNewBlock->begin(), 200 E = FirstNewBlock->end(); I != E; ) 201 if (AllocaInst *AI = dyn_cast<AllocaInst>(I++)) 202 if (isa<Constant>(AI->getArraySize())) { 203 // Scan for the block of allocas that we can move over, and move them 204 // all at once. 205 while (isa<AllocaInst>(I) && 206 isa<Constant>(cast<AllocaInst>(I)->getArraySize())) 207 ++I; 208 209 // Transfer all of the allocas over in a block. Using splice means 210 // that they instructions aren't removed from the symbol table, then 211 // reinserted. 212 Caller->front().getInstList().splice(InsertPoint, 213 FirstNewBlock->getInstList(), 214 AI, I); 215 } 216 } 217 218 // If we are inlining tail call instruction through an invoke or 219 if (MustClearTailCallFlags) { 220 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 221 BB != E; ++BB) 222 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) 223 if (CallInst *CI = dyn_cast<CallInst>(I)) 224 CI->setTailCall(false); 225 } 226 227 // If we are inlining for an invoke instruction, we must make sure to rewrite 228 // any inlined 'unwind' instructions into branches to the invoke exception 229 // destination, and call instructions into invoke instructions. 230 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 231 HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo); 232 233 // If we cloned in _exactly one_ basic block, and if that block ends in a 234 // return instruction, we splice the body of the inlined callee directly into 235 // the calling basic block. 236 if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) { 237 // Move all of the instructions right before the call. 238 OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(), 239 FirstNewBlock->begin(), FirstNewBlock->end()); 240 // Remove the cloned basic block. 241 Caller->getBasicBlockList().pop_back(); 242 243 // If the call site was an invoke instruction, add a branch to the normal 244 // destination. 245 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 246 new BranchInst(II->getNormalDest(), TheCall); 247 248 // If the return instruction returned a value, replace uses of the call with 249 // uses of the returned value. 250 if (!TheCall->use_empty()) 251 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue()); 252 253 // Since we are now done with the Call/Invoke, we can delete it. 254 TheCall->getParent()->getInstList().erase(TheCall); 255 256 // Since we are now done with the return instruction, delete it also. 257 Returns[0]->getParent()->getInstList().erase(Returns[0]); 258 259 // We are now done with the inlining. 260 return true; 261 } 262 263 // Otherwise, we have the normal case, of more than one block to inline or 264 // multiple return sites. 265 266 // We want to clone the entire callee function into the hole between the 267 // "starter" and "ender" blocks. How we accomplish this depends on whether 268 // this is an invoke instruction or a call instruction. 269 BasicBlock *AfterCallBB; 270 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) { 271 272 // Add an unconditional branch to make this look like the CallInst case... 273 BranchInst *NewBr = new BranchInst(II->getNormalDest(), TheCall); 274 275 // Split the basic block. This guarantees that no PHI nodes will have to be 276 // updated due to new incoming edges, and make the invoke case more 277 // symmetric to the call case. 278 AfterCallBB = OrigBB->splitBasicBlock(NewBr, 279 CalledFunc->getName()+".exit"); 280 281 } else { // It's a call 282 // If this is a call instruction, we need to split the basic block that 283 // the call lives in. 284 // 285 AfterCallBB = OrigBB->splitBasicBlock(TheCall, 286 CalledFunc->getName()+".exit"); 287 } 288 289 // Change the branch that used to go to AfterCallBB to branch to the first 290 // basic block of the inlined function. 291 // 292 TerminatorInst *Br = OrigBB->getTerminator(); 293 assert(Br && Br->getOpcode() == Instruction::Br && 294 "splitBasicBlock broken!"); 295 Br->setOperand(0, FirstNewBlock); 296 297 298 // Now that the function is correct, make it a little bit nicer. In 299 // particular, move the basic blocks inserted from the end of the function 300 // into the space made by splitting the source basic block. 301 // 302 Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(), 303 FirstNewBlock, Caller->end()); 304 305 // Handle all of the return instructions that we just cloned in, and eliminate 306 // any users of the original call/invoke instruction. 307 if (Returns.size() > 1) { 308 // The PHI node should go at the front of the new basic block to merge all 309 // possible incoming values. 310 // 311 PHINode *PHI = 0; 312 if (!TheCall->use_empty()) { 313 PHI = new PHINode(CalledFunc->getReturnType(), 314 TheCall->getName(), AfterCallBB->begin()); 315 316 // Anything that used the result of the function call should now use the 317 // PHI node as their operand. 318 // 319 TheCall->replaceAllUsesWith(PHI); 320 } 321 322 // Loop over all of the return instructions, turning them into unconditional 323 // branches to the merge point now, and adding entries to the PHI node as 324 // appropriate. 325 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 326 ReturnInst *RI = Returns[i]; 327 328 if (PHI) { 329 assert(RI->getReturnValue() && "Ret should have value!"); 330 assert(RI->getReturnValue()->getType() == PHI->getType() && 331 "Ret value not consistent in function!"); 332 PHI->addIncoming(RI->getReturnValue(), RI->getParent()); 333 } 334 335 // Add a branch to the merge point where the PHI node lives if it exists. 336 new BranchInst(AfterCallBB, RI); 337 338 // Delete the return instruction now 339 RI->getParent()->getInstList().erase(RI); 340 } 341 342 } else if (!Returns.empty()) { 343 // Otherwise, if there is exactly one return value, just replace anything 344 // using the return value of the call with the computed value. 345 if (!TheCall->use_empty()) 346 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue()); 347 348 // Splice the code from the return block into the block that it will return 349 // to, which contains the code that was after the call. 350 BasicBlock *ReturnBB = Returns[0]->getParent(); 351 AfterCallBB->getInstList().splice(AfterCallBB->begin(), 352 ReturnBB->getInstList()); 353 354 // Update PHI nodes that use the ReturnBB to use the AfterCallBB. 355 ReturnBB->replaceAllUsesWith(AfterCallBB); 356 357 // Delete the return instruction now and empty ReturnBB now. 358 Returns[0]->eraseFromParent(); 359 ReturnBB->eraseFromParent(); 360 } else if (!TheCall->use_empty()) { 361 // No returns, but something is using the return value of the call. Just 362 // nuke the result. 363 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType())); 364 } 365 366 // Since we are now done with the Call/Invoke, we can delete it. 367 TheCall->eraseFromParent(); 368 369 // We should always be able to fold the entry block of the function into the 370 // single predecessor of the block... 371 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!"); 372 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0); 373 374 // Splice the code entry block into calling block, right before the 375 // unconditional branch. 376 OrigBB->getInstList().splice(Br, CalleeEntry->getInstList()); 377 CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes 378 379 // Remove the unconditional branch. 380 OrigBB->getInstList().erase(Br); 381 382 // Now we can remove the CalleeEntry block, which is now empty. 383 Caller->getBasicBlockList().erase(CalleeEntry); 384 return true; 385} 386