InlineFunction.cpp revision 43ad6b3e0d6ada51e9b23aab3e061187f1f5710c
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/Analysis/CallGraph.h" 22#include "llvm/ADT/SmallVector.h" 23#include "llvm/Support/CallSite.h" 24using namespace llvm; 25 26bool llvm::InlineFunction(CallInst *CI, CallGraph *CG, const TargetData *TD) { 27 return InlineFunction(CallSite(CI), CG, TD); 28} 29bool llvm::InlineFunction(InvokeInst *II, CallGraph *CG, const TargetData *TD) { 30 return InlineFunction(CallSite(II), CG, TD); 31} 32 33/// HandleInlinedInvoke - If we inlined an invoke site, we need to convert calls 34/// in the body of the inlined function into invokes and turn unwind 35/// instructions into branches to the invoke unwind dest. 36/// 37/// II is the invoke instruction begin inlined. FirstNewBlock is the first 38/// block of the inlined code (the last block is the end of the function), 39/// and InlineCodeInfo is information about the code that got inlined. 40static void HandleInlinedInvoke(InvokeInst *II, BasicBlock *FirstNewBlock, 41 ClonedCodeInfo &InlinedCodeInfo) { 42 BasicBlock *InvokeDest = II->getUnwindDest(); 43 std::vector<Value*> InvokeDestPHIValues; 44 45 // If there are PHI nodes in the unwind destination block, we need to 46 // keep track of which values came into them from this invoke, then remove 47 // the entry for this block. 48 BasicBlock *InvokeBlock = II->getParent(); 49 for (BasicBlock::iterator I = InvokeDest->begin(); isa<PHINode>(I); ++I) { 50 PHINode *PN = cast<PHINode>(I); 51 // Save the value to use for this edge. 52 InvokeDestPHIValues.push_back(PN->getIncomingValueForBlock(InvokeBlock)); 53 } 54 55 Function *Caller = FirstNewBlock->getParent(); 56 57 // The inlined code is currently at the end of the function, scan from the 58 // start of the inlined code to its end, checking for stuff we need to 59 // rewrite. 60 if (InlinedCodeInfo.ContainsCalls || InlinedCodeInfo.ContainsUnwinds) { 61 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 62 BB != E; ++BB) { 63 if (InlinedCodeInfo.ContainsCalls) { 64 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ){ 65 Instruction *I = BBI++; 66 67 // We only need to check for function calls: inlined invoke 68 // instructions require no special handling. 69 if (!isa<CallInst>(I)) continue; 70 CallInst *CI = cast<CallInst>(I); 71 72 // If this call cannot unwind or is an inline asm, don't 73 // convert it to an invoke. 74 if (CI->isNoUnwind() || isa<InlineAsm>(CI->getCalledValue())) 75 continue; 76 77 // Convert this function call into an invoke instruction. 78 // First, split the basic block. 79 BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc"); 80 81 // Next, create the new invoke instruction, inserting it at the end 82 // of the old basic block. 83 SmallVector<Value*, 8> InvokeArgs(CI->op_begin()+1, CI->op_end()); 84 InvokeInst *II = 85 new InvokeInst(CI->getCalledValue(), Split, InvokeDest, 86 InvokeArgs.begin(), InvokeArgs.end(), 87 CI->getName(), BB->getTerminator()); 88 II->setCallingConv(CI->getCallingConv()); 89 II->setParamAttrs(CI->getParamAttrs()); 90 91 // Make sure that anything using the call now uses the invoke! 92 CI->replaceAllUsesWith(II); 93 94 // Delete the unconditional branch inserted by splitBasicBlock 95 BB->getInstList().pop_back(); 96 Split->getInstList().pop_front(); // Delete the original call 97 98 // Update any PHI nodes in the exceptional block to indicate that 99 // there is now a new entry in them. 100 unsigned i = 0; 101 for (BasicBlock::iterator I = InvokeDest->begin(); 102 isa<PHINode>(I); ++I, ++i) { 103 PHINode *PN = cast<PHINode>(I); 104 PN->addIncoming(InvokeDestPHIValues[i], BB); 105 } 106 107 // This basic block is now complete, start scanning the next one. 108 break; 109 } 110 } 111 112 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 113 // An UnwindInst requires special handling when it gets inlined into an 114 // invoke site. Once this happens, we know that the unwind would cause 115 // a control transfer to the invoke exception destination, so we can 116 // transform it into a direct branch to the exception destination. 117 new BranchInst(InvokeDest, UI); 118 119 // Delete the unwind instruction! 120 UI->getParent()->getInstList().pop_back(); 121 122 // Update any PHI nodes in the exceptional block to indicate that 123 // there is now a new entry in them. 124 unsigned i = 0; 125 for (BasicBlock::iterator I = InvokeDest->begin(); 126 isa<PHINode>(I); ++I, ++i) { 127 PHINode *PN = cast<PHINode>(I); 128 PN->addIncoming(InvokeDestPHIValues[i], BB); 129 } 130 } 131 } 132 } 133 134 // Now that everything is happy, we have one final detail. The PHI nodes in 135 // the exception destination block still have entries due to the original 136 // invoke instruction. Eliminate these entries (which might even delete the 137 // PHI node) now. 138 InvokeDest->removePredecessor(II->getParent()); 139} 140 141/// UpdateCallGraphAfterInlining - Once we have cloned code over from a callee 142/// into the caller, update the specified callgraph to reflect the changes we 143/// made. Note that it's possible that not all code was copied over, so only 144/// some edges of the callgraph will be remain. 145static void UpdateCallGraphAfterInlining(const Function *Caller, 146 const Function *Callee, 147 Function::iterator FirstNewBlock, 148 DenseMap<const Value*, Value*> &ValueMap, 149 CallGraph &CG) { 150 // Update the call graph by deleting the edge from Callee to Caller 151 CallGraphNode *CalleeNode = CG[Callee]; 152 CallGraphNode *CallerNode = CG[Caller]; 153 CallerNode->removeCallEdgeTo(CalleeNode); 154 155 // Since we inlined some uninlined call sites in the callee into the caller, 156 // add edges from the caller to all of the callees of the callee. 157 for (CallGraphNode::iterator I = CalleeNode->begin(), 158 E = CalleeNode->end(); I != E; ++I) { 159 const Instruction *OrigCall = I->first.getInstruction(); 160 161 DenseMap<const Value*, Value*>::iterator VMI = ValueMap.find(OrigCall); 162 // Only copy the edge if the call was inlined! 163 if (VMI != ValueMap.end() && VMI->second) { 164 // If the call was inlined, but then constant folded, there is no edge to 165 // add. Check for this case. 166 if (Instruction *NewCall = dyn_cast<Instruction>(VMI->second)) 167 CallerNode->addCalledFunction(CallSite::get(NewCall), I->second); 168 } 169 } 170} 171 172 173// InlineFunction - This function inlines the called function into the basic 174// block of the caller. This returns false if it is not possible to inline this 175// call. The program is still in a well defined state if this occurs though. 176// 177// Note that this only does one level of inlining. For example, if the 178// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now 179// exists in the instruction stream. Similiarly this will inline a recursive 180// function by one level. 181// 182bool llvm::InlineFunction(CallSite CS, CallGraph *CG, const TargetData *TD) { 183 Instruction *TheCall = CS.getInstruction(); 184 assert(TheCall->getParent() && TheCall->getParent()->getParent() && 185 "Instruction not in function!"); 186 187 const Function *CalledFunc = CS.getCalledFunction(); 188 if (CalledFunc == 0 || // Can't inline external function or indirect 189 CalledFunc->isDeclaration() || // call, or call to a vararg function! 190 CalledFunc->getFunctionType()->isVarArg()) return false; 191 192 193 // If the call to the callee is a non-tail call, we must clear the 'tail' 194 // flags on any calls that we inline. 195 bool MustClearTailCallFlags = 196 isa<CallInst>(TheCall) && !cast<CallInst>(TheCall)->isTailCall(); 197 198 BasicBlock *OrigBB = TheCall->getParent(); 199 Function *Caller = OrigBB->getParent(); 200 201 // Get an iterator to the last basic block in the function, which will have 202 // the new function inlined after it. 203 // 204 Function::iterator LastBlock = &Caller->back(); 205 206 // Make sure to capture all of the return instructions from the cloned 207 // function. 208 std::vector<ReturnInst*> Returns; 209 ClonedCodeInfo InlinedFunctionInfo; 210 Function::iterator FirstNewBlock; 211 212 { // Scope to destroy ValueMap after cloning. 213 DenseMap<const Value*, Value*> ValueMap; 214 215 // Calculate the vector of arguments to pass into the function cloner, which 216 // matches up the formal to the actual argument values. 217 assert(std::distance(CalledFunc->arg_begin(), CalledFunc->arg_end()) == 218 std::distance(CS.arg_begin(), CS.arg_end()) && 219 "No varargs calls can be inlined!"); 220 CallSite::arg_iterator AI = CS.arg_begin(); 221 for (Function::const_arg_iterator I = CalledFunc->arg_begin(), 222 E = CalledFunc->arg_end(); I != E; ++I, ++AI) 223 ValueMap[I] = *AI; 224 225 // We want the inliner to prune the code as it copies. We would LOVE to 226 // have no dead or constant instructions leftover after inlining occurs 227 // (which can happen, e.g., because an argument was constant), but we'll be 228 // happy with whatever the cloner can do. 229 CloneAndPruneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i", 230 &InlinedFunctionInfo, TD); 231 232 // Remember the first block that is newly cloned over. 233 FirstNewBlock = LastBlock; ++FirstNewBlock; 234 235 // Update the callgraph if requested. 236 if (CG) 237 UpdateCallGraphAfterInlining(Caller, CalledFunc, FirstNewBlock, ValueMap, 238 *CG); 239 } 240 241 // If there are any alloca instructions in the block that used to be the entry 242 // block for the callee, move them to the entry block of the caller. First 243 // calculate which instruction they should be inserted before. We insert the 244 // instructions at the end of the current alloca list. 245 // 246 { 247 BasicBlock::iterator InsertPoint = Caller->begin()->begin(); 248 for (BasicBlock::iterator I = FirstNewBlock->begin(), 249 E = FirstNewBlock->end(); I != E; ) 250 if (AllocaInst *AI = dyn_cast<AllocaInst>(I++)) { 251 // If the alloca is now dead, remove it. This often occurs due to code 252 // specialization. 253 if (AI->use_empty()) { 254 AI->eraseFromParent(); 255 continue; 256 } 257 258 if (isa<Constant>(AI->getArraySize())) { 259 // Scan for the block of allocas that we can move over, and move them 260 // all at once. 261 while (isa<AllocaInst>(I) && 262 isa<Constant>(cast<AllocaInst>(I)->getArraySize())) 263 ++I; 264 265 // Transfer all of the allocas over in a block. Using splice means 266 // that the instructions aren't removed from the symbol table, then 267 // reinserted. 268 Caller->getEntryBlock().getInstList().splice( 269 InsertPoint, 270 FirstNewBlock->getInstList(), 271 AI, I); 272 } 273 } 274 } 275 276 // If the inlined code contained dynamic alloca instructions, wrap the inlined 277 // code with llvm.stacksave/llvm.stackrestore intrinsics. 278 if (InlinedFunctionInfo.ContainsDynamicAllocas) { 279 Module *M = Caller->getParent(); 280 const Type *BytePtr = PointerType::getUnqual(Type::Int8Ty); 281 // Get the two intrinsics we care about. 282 Constant *StackSave, *StackRestore; 283 StackSave = M->getOrInsertFunction("llvm.stacksave", BytePtr, NULL); 284 StackRestore = M->getOrInsertFunction("llvm.stackrestore", Type::VoidTy, 285 BytePtr, NULL); 286 287 // If we are preserving the callgraph, add edges to the stacksave/restore 288 // functions for the calls we insert. 289 CallGraphNode *StackSaveCGN = 0, *StackRestoreCGN = 0, *CallerNode = 0; 290 if (CG) { 291 // We know that StackSave/StackRestore are Function*'s, because they are 292 // intrinsics which must have the right types. 293 StackSaveCGN = CG->getOrInsertFunction(cast<Function>(StackSave)); 294 StackRestoreCGN = CG->getOrInsertFunction(cast<Function>(StackRestore)); 295 CallerNode = (*CG)[Caller]; 296 } 297 298 // Insert the llvm.stacksave. 299 CallInst *SavedPtr = new CallInst(StackSave, "savedstack", 300 FirstNewBlock->begin()); 301 if (CG) CallerNode->addCalledFunction(SavedPtr, StackSaveCGN); 302 303 // Insert a call to llvm.stackrestore before any return instructions in the 304 // inlined function. 305 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 306 CallInst *CI = new CallInst(StackRestore, SavedPtr, "", Returns[i]); 307 if (CG) CallerNode->addCalledFunction(CI, StackRestoreCGN); 308 } 309 310 // Count the number of StackRestore calls we insert. 311 unsigned NumStackRestores = Returns.size(); 312 313 // If we are inlining an invoke instruction, insert restores before each 314 // unwind. These unwinds will be rewritten into branches later. 315 if (InlinedFunctionInfo.ContainsUnwinds && isa<InvokeInst>(TheCall)) { 316 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 317 BB != E; ++BB) 318 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 319 new CallInst(StackRestore, SavedPtr, "", UI); 320 ++NumStackRestores; 321 } 322 } 323 } 324 325 // If we are inlining tail call instruction through a call site that isn't 326 // marked 'tail', we must remove the tail marker for any calls in the inlined 327 // code. 328 if (MustClearTailCallFlags && InlinedFunctionInfo.ContainsCalls) { 329 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 330 BB != E; ++BB) 331 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) 332 if (CallInst *CI = dyn_cast<CallInst>(I)) 333 CI->setTailCall(false); 334 } 335 336 // If we are inlining for an invoke instruction, we must make sure to rewrite 337 // any inlined 'unwind' instructions into branches to the invoke exception 338 // destination, and call instructions into invoke instructions. 339 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 340 HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo); 341 342 // If we cloned in _exactly one_ basic block, and if that block ends in a 343 // return instruction, we splice the body of the inlined callee directly into 344 // the calling basic block. 345 if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) { 346 // Move all of the instructions right before the call. 347 OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(), 348 FirstNewBlock->begin(), FirstNewBlock->end()); 349 // Remove the cloned basic block. 350 Caller->getBasicBlockList().pop_back(); 351 352 // If the call site was an invoke instruction, add a branch to the normal 353 // destination. 354 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 355 new BranchInst(II->getNormalDest(), TheCall); 356 357 // If the return instruction returned a value, replace uses of the call with 358 // uses of the returned value. 359 if (!TheCall->use_empty()) 360 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue()); 361 362 // Since we are now done with the Call/Invoke, we can delete it. 363 TheCall->getParent()->getInstList().erase(TheCall); 364 365 // Since we are now done with the return instruction, delete it also. 366 Returns[0]->getParent()->getInstList().erase(Returns[0]); 367 368 // We are now done with the inlining. 369 return true; 370 } 371 372 // Otherwise, we have the normal case, of more than one block to inline or 373 // multiple return sites. 374 375 // We want to clone the entire callee function into the hole between the 376 // "starter" and "ender" blocks. How we accomplish this depends on whether 377 // this is an invoke instruction or a call instruction. 378 BasicBlock *AfterCallBB; 379 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) { 380 381 // Add an unconditional branch to make this look like the CallInst case... 382 BranchInst *NewBr = new BranchInst(II->getNormalDest(), TheCall); 383 384 // Split the basic block. This guarantees that no PHI nodes will have to be 385 // updated due to new incoming edges, and make the invoke case more 386 // symmetric to the call case. 387 AfterCallBB = OrigBB->splitBasicBlock(NewBr, 388 CalledFunc->getName()+".exit"); 389 390 } else { // It's a call 391 // If this is a call instruction, we need to split the basic block that 392 // the call lives in. 393 // 394 AfterCallBB = OrigBB->splitBasicBlock(TheCall, 395 CalledFunc->getName()+".exit"); 396 } 397 398 // Change the branch that used to go to AfterCallBB to branch to the first 399 // basic block of the inlined function. 400 // 401 TerminatorInst *Br = OrigBB->getTerminator(); 402 assert(Br && Br->getOpcode() == Instruction::Br && 403 "splitBasicBlock broken!"); 404 Br->setOperand(0, FirstNewBlock); 405 406 407 // Now that the function is correct, make it a little bit nicer. In 408 // particular, move the basic blocks inserted from the end of the function 409 // into the space made by splitting the source basic block. 410 // 411 Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(), 412 FirstNewBlock, Caller->end()); 413 414 // Handle all of the return instructions that we just cloned in, and eliminate 415 // any users of the original call/invoke instruction. 416 if (Returns.size() > 1) { 417 // The PHI node should go at the front of the new basic block to merge all 418 // possible incoming values. 419 // 420 PHINode *PHI = 0; 421 if (!TheCall->use_empty()) { 422 PHI = new PHINode(CalledFunc->getReturnType(), 423 TheCall->getName(), AfterCallBB->begin()); 424 425 // Anything that used the result of the function call should now use the 426 // PHI node as their operand. 427 // 428 TheCall->replaceAllUsesWith(PHI); 429 } 430 431 // Loop over all of the return instructions, turning them into unconditional 432 // branches to the merge point now, and adding entries to the PHI node as 433 // appropriate. 434 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 435 ReturnInst *RI = Returns[i]; 436 437 if (PHI) { 438 assert(RI->getReturnValue() && "Ret should have value!"); 439 assert(RI->getReturnValue()->getType() == PHI->getType() && 440 "Ret value not consistent in function!"); 441 PHI->addIncoming(RI->getReturnValue(), RI->getParent()); 442 } 443 444 // Add a branch to the merge point where the PHI node lives if it exists. 445 new BranchInst(AfterCallBB, RI); 446 447 // Delete the return instruction now 448 RI->getParent()->getInstList().erase(RI); 449 } 450 451 } else if (!Returns.empty()) { 452 // Otherwise, if there is exactly one return value, just replace anything 453 // using the return value of the call with the computed value. 454 if (!TheCall->use_empty()) 455 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue()); 456 457 // Splice the code from the return block into the block that it will return 458 // to, which contains the code that was after the call. 459 BasicBlock *ReturnBB = Returns[0]->getParent(); 460 AfterCallBB->getInstList().splice(AfterCallBB->begin(), 461 ReturnBB->getInstList()); 462 463 // Update PHI nodes that use the ReturnBB to use the AfterCallBB. 464 ReturnBB->replaceAllUsesWith(AfterCallBB); 465 466 // Delete the return instruction now and empty ReturnBB now. 467 Returns[0]->eraseFromParent(); 468 ReturnBB->eraseFromParent(); 469 } else if (!TheCall->use_empty()) { 470 // No returns, but something is using the return value of the call. Just 471 // nuke the result. 472 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType())); 473 } 474 475 // Since we are now done with the Call/Invoke, we can delete it. 476 TheCall->eraseFromParent(); 477 478 // We should always be able to fold the entry block of the function into the 479 // single predecessor of the block... 480 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!"); 481 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0); 482 483 // Splice the code entry block into calling block, right before the 484 // unconditional branch. 485 OrigBB->getInstList().splice(Br, CalleeEntry->getInstList()); 486 CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes 487 488 // Remove the unconditional branch. 489 OrigBB->getInstList().erase(Br); 490 491 // Now we can remove the CalleeEntry block, which is now empty. 492 Caller->getBasicBlockList().erase(CalleeEntry); 493 494 return true; 495} 496