InlineFunction.cpp revision ece2c04d532d46405c085769d03173b392813eb3
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, don't convert it to an invoke. 73 if (CI->isNoUnwind()) 74 continue; 75 76 // Convert this function call into an invoke instruction. 77 // First, split the basic block. 78 BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc"); 79 80 // Next, create the new invoke instruction, inserting it at the end 81 // of the old basic block. 82 SmallVector<Value*, 8> InvokeArgs(CI->op_begin()+1, CI->op_end()); 83 InvokeInst *II = 84 new InvokeInst(CI->getCalledValue(), Split, InvokeDest, 85 InvokeArgs.begin(), InvokeArgs.end(), 86 CI->getName(), BB->getTerminator()); 87 II->setCallingConv(CI->getCallingConv()); 88 II->setParamAttrs(CI->getParamAttrs()); 89 90 // Make sure that anything using the call now uses the invoke! 91 CI->replaceAllUsesWith(II); 92 93 // Delete the unconditional branch inserted by splitBasicBlock 94 BB->getInstList().pop_back(); 95 Split->getInstList().pop_front(); // Delete the original call 96 97 // Update any PHI nodes in the exceptional block to indicate that 98 // there is now a new entry in them. 99 unsigned i = 0; 100 for (BasicBlock::iterator I = InvokeDest->begin(); 101 isa<PHINode>(I); ++I, ++i) { 102 PHINode *PN = cast<PHINode>(I); 103 PN->addIncoming(InvokeDestPHIValues[i], BB); 104 } 105 106 // This basic block is now complete, start scanning the next one. 107 break; 108 } 109 } 110 111 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 112 // An UnwindInst requires special handling when it gets inlined into an 113 // invoke site. Once this happens, we know that the unwind would cause 114 // a control transfer to the invoke exception destination, so we can 115 // transform it into a direct branch to the exception destination. 116 new BranchInst(InvokeDest, UI); 117 118 // Delete the unwind instruction! 119 UI->getParent()->getInstList().pop_back(); 120 121 // Update any PHI nodes in the exceptional block to indicate that 122 // there is now a new entry in them. 123 unsigned i = 0; 124 for (BasicBlock::iterator I = InvokeDest->begin(); 125 isa<PHINode>(I); ++I, ++i) { 126 PHINode *PN = cast<PHINode>(I); 127 PN->addIncoming(InvokeDestPHIValues[i], BB); 128 } 129 } 130 } 131 } 132 133 // Now that everything is happy, we have one final detail. The PHI nodes in 134 // the exception destination block still have entries due to the original 135 // invoke instruction. Eliminate these entries (which might even delete the 136 // PHI node) now. 137 InvokeDest->removePredecessor(II->getParent()); 138} 139 140/// UpdateCallGraphAfterInlining - Once we have cloned code over from a callee 141/// into the caller, update the specified callgraph to reflect the changes we 142/// made. Note that it's possible that not all code was copied over, so only 143/// some edges of the callgraph will be remain. 144static void UpdateCallGraphAfterInlining(const Function *Caller, 145 const Function *Callee, 146 Function::iterator FirstNewBlock, 147 DenseMap<const Value*, Value*> &ValueMap, 148 CallGraph &CG) { 149 // Update the call graph by deleting the edge from Callee to Caller 150 CallGraphNode *CalleeNode = CG[Callee]; 151 CallGraphNode *CallerNode = CG[Caller]; 152 CallerNode->removeCallEdgeTo(CalleeNode); 153 154 // Since we inlined some uninlined call sites in the callee into the caller, 155 // add edges from the caller to all of the callees of the callee. 156 for (CallGraphNode::iterator I = CalleeNode->begin(), 157 E = CalleeNode->end(); I != E; ++I) { 158 const Instruction *OrigCall = I->first.getInstruction(); 159 160 DenseMap<const Value*, Value*>::iterator VMI = ValueMap.find(OrigCall); 161 // Only copy the edge if the call was inlined! 162 if (VMI != ValueMap.end() && VMI->second) { 163 // If the call was inlined, but then constant folded, there is no edge to 164 // add. Check for this case. 165 if (Instruction *NewCall = dyn_cast<Instruction>(VMI->second)) 166 CallerNode->addCalledFunction(CallSite::get(NewCall), I->second); 167 } 168 } 169} 170 171 172// InlineFunction - This function inlines the called function into the basic 173// block of the caller. This returns false if it is not possible to inline this 174// call. The program is still in a well defined state if this occurs though. 175// 176// Note that this only does one level of inlining. For example, if the 177// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now 178// exists in the instruction stream. Similiarly this will inline a recursive 179// function by one level. 180// 181bool llvm::InlineFunction(CallSite CS, CallGraph *CG, const TargetData *TD) { 182 Instruction *TheCall = CS.getInstruction(); 183 assert(TheCall->getParent() && TheCall->getParent()->getParent() && 184 "Instruction not in function!"); 185 186 const Function *CalledFunc = CS.getCalledFunction(); 187 if (CalledFunc == 0 || // Can't inline external function or indirect 188 CalledFunc->isDeclaration() || // call, or call to a vararg function! 189 CalledFunc->getFunctionType()->isVarArg()) return false; 190 191 192 // If the call to the callee is a non-tail call, we must clear the 'tail' 193 // flags on any calls that we inline. 194 bool MustClearTailCallFlags = 195 isa<CallInst>(TheCall) && !cast<CallInst>(TheCall)->isTailCall(); 196 197 BasicBlock *OrigBB = TheCall->getParent(); 198 Function *Caller = OrigBB->getParent(); 199 200 // Get an iterator to the last basic block in the function, which will have 201 // the new function inlined after it. 202 // 203 Function::iterator LastBlock = &Caller->back(); 204 205 // Make sure to capture all of the return instructions from the cloned 206 // function. 207 std::vector<ReturnInst*> Returns; 208 ClonedCodeInfo InlinedFunctionInfo; 209 Function::iterator FirstNewBlock; 210 211 { // Scope to destroy ValueMap after cloning. 212 DenseMap<const Value*, Value*> ValueMap; 213 214 // Calculate the vector of arguments to pass into the function cloner, which 215 // matches up the formal to the actual argument values. 216 assert(std::distance(CalledFunc->arg_begin(), CalledFunc->arg_end()) == 217 std::distance(CS.arg_begin(), CS.arg_end()) && 218 "No varargs calls can be inlined!"); 219 CallSite::arg_iterator AI = CS.arg_begin(); 220 for (Function::const_arg_iterator I = CalledFunc->arg_begin(), 221 E = CalledFunc->arg_end(); I != E; ++I, ++AI) 222 ValueMap[I] = *AI; 223 224 // We want the inliner to prune the code as it copies. We would LOVE to 225 // have no dead or constant instructions leftover after inlining occurs 226 // (which can happen, e.g., because an argument was constant), but we'll be 227 // happy with whatever the cloner can do. 228 CloneAndPruneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i", 229 &InlinedFunctionInfo, TD); 230 231 // Remember the first block that is newly cloned over. 232 FirstNewBlock = LastBlock; ++FirstNewBlock; 233 234 // Update the callgraph if requested. 235 if (CG) 236 UpdateCallGraphAfterInlining(Caller, CalledFunc, FirstNewBlock, ValueMap, 237 *CG); 238 } 239 240 // If there are any alloca instructions in the block that used to be the entry 241 // block for the callee, move them to the entry block of the caller. First 242 // calculate which instruction they should be inserted before. We insert the 243 // instructions at the end of the current alloca list. 244 // 245 { 246 BasicBlock::iterator InsertPoint = Caller->begin()->begin(); 247 for (BasicBlock::iterator I = FirstNewBlock->begin(), 248 E = FirstNewBlock->end(); I != E; ) 249 if (AllocaInst *AI = dyn_cast<AllocaInst>(I++)) { 250 // If the alloca is now dead, remove it. This often occurs due to code 251 // specialization. 252 if (AI->use_empty()) { 253 AI->eraseFromParent(); 254 continue; 255 } 256 257 if (isa<Constant>(AI->getArraySize())) { 258 // Scan for the block of allocas that we can move over, and move them 259 // all at once. 260 while (isa<AllocaInst>(I) && 261 isa<Constant>(cast<AllocaInst>(I)->getArraySize())) 262 ++I; 263 264 // Transfer all of the allocas over in a block. Using splice means 265 // that the instructions aren't removed from the symbol table, then 266 // reinserted. 267 Caller->getEntryBlock().getInstList().splice( 268 InsertPoint, 269 FirstNewBlock->getInstList(), 270 AI, I); 271 } 272 } 273 } 274 275 // If the inlined code contained dynamic alloca instructions, wrap the inlined 276 // code with llvm.stacksave/llvm.stackrestore intrinsics. 277 if (InlinedFunctionInfo.ContainsDynamicAllocas) { 278 Module *M = Caller->getParent(); 279 const Type *BytePtr = PointerType::get(Type::Int8Ty); 280 // Get the two intrinsics we care about. 281 Constant *StackSave, *StackRestore; 282 StackSave = M->getOrInsertFunction("llvm.stacksave", BytePtr, NULL); 283 StackRestore = M->getOrInsertFunction("llvm.stackrestore", Type::VoidTy, 284 BytePtr, NULL); 285 286 // If we are preserving the callgraph, add edges to the stacksave/restore 287 // functions for the calls we insert. 288 CallGraphNode *StackSaveCGN = 0, *StackRestoreCGN = 0, *CallerNode = 0; 289 if (CG) { 290 // We know that StackSave/StackRestore are Function*'s, because they are 291 // intrinsics which must have the right types. 292 StackSaveCGN = CG->getOrInsertFunction(cast<Function>(StackSave)); 293 StackRestoreCGN = CG->getOrInsertFunction(cast<Function>(StackRestore)); 294 CallerNode = (*CG)[Caller]; 295 } 296 297 // Insert the llvm.stacksave. 298 CallInst *SavedPtr = new CallInst(StackSave, "savedstack", 299 FirstNewBlock->begin()); 300 if (CG) CallerNode->addCalledFunction(SavedPtr, StackSaveCGN); 301 302 // Insert a call to llvm.stackrestore before any return instructions in the 303 // inlined function. 304 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 305 CallInst *CI = new CallInst(StackRestore, SavedPtr, "", Returns[i]); 306 if (CG) CallerNode->addCalledFunction(CI, StackRestoreCGN); 307 } 308 309 // Count the number of StackRestore calls we insert. 310 unsigned NumStackRestores = Returns.size(); 311 312 // If we are inlining an invoke instruction, insert restores before each 313 // unwind. These unwinds will be rewritten into branches later. 314 if (InlinedFunctionInfo.ContainsUnwinds && isa<InvokeInst>(TheCall)) { 315 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 316 BB != E; ++BB) 317 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 318 new CallInst(StackRestore, SavedPtr, "", UI); 319 ++NumStackRestores; 320 } 321 } 322 } 323 324 // If we are inlining tail call instruction through a call site that isn't 325 // marked 'tail', we must remove the tail marker for any calls in the inlined 326 // code. 327 if (MustClearTailCallFlags && InlinedFunctionInfo.ContainsCalls) { 328 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 329 BB != E; ++BB) 330 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) 331 if (CallInst *CI = dyn_cast<CallInst>(I)) 332 CI->setTailCall(false); 333 } 334 335 // If we are inlining for an invoke instruction, we must make sure to rewrite 336 // any inlined 'unwind' instructions into branches to the invoke exception 337 // destination, and call instructions into invoke instructions. 338 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 339 HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo); 340 341 // If we cloned in _exactly one_ basic block, and if that block ends in a 342 // return instruction, we splice the body of the inlined callee directly into 343 // the calling basic block. 344 if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) { 345 // Move all of the instructions right before the call. 346 OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(), 347 FirstNewBlock->begin(), FirstNewBlock->end()); 348 // Remove the cloned basic block. 349 Caller->getBasicBlockList().pop_back(); 350 351 // If the call site was an invoke instruction, add a branch to the normal 352 // destination. 353 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 354 new BranchInst(II->getNormalDest(), TheCall); 355 356 // If the return instruction returned a value, replace uses of the call with 357 // uses of the returned value. 358 if (!TheCall->use_empty()) 359 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue()); 360 361 // Since we are now done with the Call/Invoke, we can delete it. 362 TheCall->getParent()->getInstList().erase(TheCall); 363 364 // Since we are now done with the return instruction, delete it also. 365 Returns[0]->getParent()->getInstList().erase(Returns[0]); 366 367 // We are now done with the inlining. 368 return true; 369 } 370 371 // Otherwise, we have the normal case, of more than one block to inline or 372 // multiple return sites. 373 374 // We want to clone the entire callee function into the hole between the 375 // "starter" and "ender" blocks. How we accomplish this depends on whether 376 // this is an invoke instruction or a call instruction. 377 BasicBlock *AfterCallBB; 378 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) { 379 380 // Add an unconditional branch to make this look like the CallInst case... 381 BranchInst *NewBr = new BranchInst(II->getNormalDest(), TheCall); 382 383 // Split the basic block. This guarantees that no PHI nodes will have to be 384 // updated due to new incoming edges, and make the invoke case more 385 // symmetric to the call case. 386 AfterCallBB = OrigBB->splitBasicBlock(NewBr, 387 CalledFunc->getName()+".exit"); 388 389 } else { // It's a call 390 // If this is a call instruction, we need to split the basic block that 391 // the call lives in. 392 // 393 AfterCallBB = OrigBB->splitBasicBlock(TheCall, 394 CalledFunc->getName()+".exit"); 395 } 396 397 // Change the branch that used to go to AfterCallBB to branch to the first 398 // basic block of the inlined function. 399 // 400 TerminatorInst *Br = OrigBB->getTerminator(); 401 assert(Br && Br->getOpcode() == Instruction::Br && 402 "splitBasicBlock broken!"); 403 Br->setOperand(0, FirstNewBlock); 404 405 406 // Now that the function is correct, make it a little bit nicer. In 407 // particular, move the basic blocks inserted from the end of the function 408 // into the space made by splitting the source basic block. 409 // 410 Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(), 411 FirstNewBlock, Caller->end()); 412 413 // Handle all of the return instructions that we just cloned in, and eliminate 414 // any users of the original call/invoke instruction. 415 if (Returns.size() > 1) { 416 // The PHI node should go at the front of the new basic block to merge all 417 // possible incoming values. 418 // 419 PHINode *PHI = 0; 420 if (!TheCall->use_empty()) { 421 PHI = new PHINode(CalledFunc->getReturnType(), 422 TheCall->getName(), AfterCallBB->begin()); 423 424 // Anything that used the result of the function call should now use the 425 // PHI node as their operand. 426 // 427 TheCall->replaceAllUsesWith(PHI); 428 } 429 430 // Loop over all of the return instructions, turning them into unconditional 431 // branches to the merge point now, and adding entries to the PHI node as 432 // appropriate. 433 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 434 ReturnInst *RI = Returns[i]; 435 436 if (PHI) { 437 assert(RI->getReturnValue() && "Ret should have value!"); 438 assert(RI->getReturnValue()->getType() == PHI->getType() && 439 "Ret value not consistent in function!"); 440 PHI->addIncoming(RI->getReturnValue(), RI->getParent()); 441 } 442 443 // Add a branch to the merge point where the PHI node lives if it exists. 444 new BranchInst(AfterCallBB, RI); 445 446 // Delete the return instruction now 447 RI->getParent()->getInstList().erase(RI); 448 } 449 450 } else if (!Returns.empty()) { 451 // Otherwise, if there is exactly one return value, just replace anything 452 // using the return value of the call with the computed value. 453 if (!TheCall->use_empty()) 454 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue()); 455 456 // Splice the code from the return block into the block that it will return 457 // to, which contains the code that was after the call. 458 BasicBlock *ReturnBB = Returns[0]->getParent(); 459 AfterCallBB->getInstList().splice(AfterCallBB->begin(), 460 ReturnBB->getInstList()); 461 462 // Update PHI nodes that use the ReturnBB to use the AfterCallBB. 463 ReturnBB->replaceAllUsesWith(AfterCallBB); 464 465 // Delete the return instruction now and empty ReturnBB now. 466 Returns[0]->eraseFromParent(); 467 ReturnBB->eraseFromParent(); 468 } else if (!TheCall->use_empty()) { 469 // No returns, but something is using the return value of the call. Just 470 // nuke the result. 471 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType())); 472 } 473 474 // Since we are now done with the Call/Invoke, we can delete it. 475 TheCall->eraseFromParent(); 476 477 // We should always be able to fold the entry block of the function into the 478 // single predecessor of the block... 479 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!"); 480 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0); 481 482 // Splice the code entry block into calling block, right before the 483 // unconditional branch. 484 OrigBB->getInstList().splice(Br, CalleeEntry->getInstList()); 485 CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes 486 487 // Remove the unconditional branch. 488 OrigBB->getInstList().erase(Br); 489 490 // Now we can remove the CalleeEntry block, which is now empty. 491 Caller->getBasicBlockList().erase(CalleeEntry); 492 493 return true; 494} 495