InlineFunction.cpp revision f0c3354d998507515ab39e26b5292ea0ceb06aef
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->doesNotThrow()) 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 // If the call to the callee cannot throw, set the 'nounwind' flag on any 198 // calls that we inline. 199 bool MarkNoUnwind = CS.doesNotThrow(); 200 201 BasicBlock *OrigBB = TheCall->getParent(); 202 Function *Caller = OrigBB->getParent(); 203 204 // Get an iterator to the last basic block in the function, which will have 205 // the new function inlined after it. 206 // 207 Function::iterator LastBlock = &Caller->back(); 208 209 // Make sure to capture all of the return instructions from the cloned 210 // function. 211 std::vector<ReturnInst*> Returns; 212 ClonedCodeInfo InlinedFunctionInfo; 213 Function::iterator FirstNewBlock; 214 215 { // Scope to destroy ValueMap after cloning. 216 DenseMap<const Value*, Value*> ValueMap; 217 218 // Calculate the vector of arguments to pass into the function cloner, which 219 // matches up the formal to the actual argument values. 220 assert(std::distance(CalledFunc->arg_begin(), CalledFunc->arg_end()) == 221 std::distance(CS.arg_begin(), CS.arg_end()) && 222 "No varargs calls can be inlined!"); 223 CallSite::arg_iterator AI = CS.arg_begin(); 224 for (Function::const_arg_iterator I = CalledFunc->arg_begin(), 225 E = CalledFunc->arg_end(); I != E; ++I, ++AI) 226 ValueMap[I] = *AI; 227 228 // We want the inliner to prune the code as it copies. We would LOVE to 229 // have no dead or constant instructions leftover after inlining occurs 230 // (which can happen, e.g., because an argument was constant), but we'll be 231 // happy with whatever the cloner can do. 232 CloneAndPruneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i", 233 &InlinedFunctionInfo, TD); 234 235 // Remember the first block that is newly cloned over. 236 FirstNewBlock = LastBlock; ++FirstNewBlock; 237 238 // Update the callgraph if requested. 239 if (CG) 240 UpdateCallGraphAfterInlining(Caller, CalledFunc, FirstNewBlock, ValueMap, 241 *CG); 242 } 243 244 // If there are any alloca instructions in the block that used to be the entry 245 // block for the callee, move them to the entry block of the caller. First 246 // calculate which instruction they should be inserted before. We insert the 247 // instructions at the end of the current alloca list. 248 // 249 { 250 BasicBlock::iterator InsertPoint = Caller->begin()->begin(); 251 for (BasicBlock::iterator I = FirstNewBlock->begin(), 252 E = FirstNewBlock->end(); I != E; ) 253 if (AllocaInst *AI = dyn_cast<AllocaInst>(I++)) { 254 // If the alloca is now dead, remove it. This often occurs due to code 255 // specialization. 256 if (AI->use_empty()) { 257 AI->eraseFromParent(); 258 continue; 259 } 260 261 if (isa<Constant>(AI->getArraySize())) { 262 // Scan for the block of allocas that we can move over, and move them 263 // all at once. 264 while (isa<AllocaInst>(I) && 265 isa<Constant>(cast<AllocaInst>(I)->getArraySize())) 266 ++I; 267 268 // Transfer all of the allocas over in a block. Using splice means 269 // that the instructions aren't removed from the symbol table, then 270 // reinserted. 271 Caller->getEntryBlock().getInstList().splice( 272 InsertPoint, 273 FirstNewBlock->getInstList(), 274 AI, I); 275 } 276 } 277 } 278 279 // If the inlined code contained dynamic alloca instructions, wrap the inlined 280 // code with llvm.stacksave/llvm.stackrestore intrinsics. 281 if (InlinedFunctionInfo.ContainsDynamicAllocas) { 282 Module *M = Caller->getParent(); 283 const Type *BytePtr = PointerType::getUnqual(Type::Int8Ty); 284 // Get the two intrinsics we care about. 285 Constant *StackSave, *StackRestore; 286 StackSave = M->getOrInsertFunction("llvm.stacksave", BytePtr, NULL); 287 StackRestore = M->getOrInsertFunction("llvm.stackrestore", Type::VoidTy, 288 BytePtr, NULL); 289 290 // If we are preserving the callgraph, add edges to the stacksave/restore 291 // functions for the calls we insert. 292 CallGraphNode *StackSaveCGN = 0, *StackRestoreCGN = 0, *CallerNode = 0; 293 if (CG) { 294 // We know that StackSave/StackRestore are Function*'s, because they are 295 // intrinsics which must have the right types. 296 StackSaveCGN = CG->getOrInsertFunction(cast<Function>(StackSave)); 297 StackRestoreCGN = CG->getOrInsertFunction(cast<Function>(StackRestore)); 298 CallerNode = (*CG)[Caller]; 299 } 300 301 // Insert the llvm.stacksave. 302 CallInst *SavedPtr = new CallInst(StackSave, "savedstack", 303 FirstNewBlock->begin()); 304 if (CG) CallerNode->addCalledFunction(SavedPtr, StackSaveCGN); 305 306 // Insert a call to llvm.stackrestore before any return instructions in the 307 // inlined function. 308 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 309 CallInst *CI = new CallInst(StackRestore, SavedPtr, "", Returns[i]); 310 if (CG) CallerNode->addCalledFunction(CI, StackRestoreCGN); 311 } 312 313 // Count the number of StackRestore calls we insert. 314 unsigned NumStackRestores = Returns.size(); 315 316 // If we are inlining an invoke instruction, insert restores before each 317 // unwind. These unwinds will be rewritten into branches later. 318 if (InlinedFunctionInfo.ContainsUnwinds && isa<InvokeInst>(TheCall)) { 319 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 320 BB != E; ++BB) 321 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 322 new CallInst(StackRestore, SavedPtr, "", UI); 323 ++NumStackRestores; 324 } 325 } 326 } 327 328 // If we are inlining tail call instruction through a call site that isn't 329 // marked 'tail', we must remove the tail marker for any calls in the inlined 330 // code. Also, calls inlined through a 'nounwind' call site should be marked 331 // 'nounwind'. 332 if (InlinedFunctionInfo.ContainsCalls && 333 (MustClearTailCallFlags || MarkNoUnwind)) { 334 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 335 BB != E; ++BB) 336 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) 337 if (CallInst *CI = dyn_cast<CallInst>(I)) { 338 if (MustClearTailCallFlags) 339 CI->setTailCall(false); 340 if (MarkNoUnwind) 341 CI->setDoesNotThrow(); 342 } 343 } 344 345 // If we are inlining through a 'nounwind' call site then any inlined 'unwind' 346 // instructions are unreachable. 347 if (InlinedFunctionInfo.ContainsUnwinds && MarkNoUnwind) 348 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 349 BB != E; ++BB) { 350 TerminatorInst *Term = BB->getTerminator(); 351 if (isa<UnwindInst>(Term)) { 352 new UnreachableInst(Term); 353 BB->getInstList().erase(Term); 354 } 355 } 356 357 // If we are inlining for an invoke instruction, we must make sure to rewrite 358 // any inlined 'unwind' instructions into branches to the invoke exception 359 // destination, and call instructions into invoke instructions. 360 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 361 HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo); 362 363 // If we cloned in _exactly one_ basic block, and if that block ends in a 364 // return instruction, we splice the body of the inlined callee directly into 365 // the calling basic block. 366 if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) { 367 // Move all of the instructions right before the call. 368 OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(), 369 FirstNewBlock->begin(), FirstNewBlock->end()); 370 // Remove the cloned basic block. 371 Caller->getBasicBlockList().pop_back(); 372 373 // If the call site was an invoke instruction, add a branch to the normal 374 // destination. 375 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 376 new BranchInst(II->getNormalDest(), TheCall); 377 378 // If the return instruction returned a value, replace uses of the call with 379 // uses of the returned value. 380 if (!TheCall->use_empty()) 381 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue()); 382 383 // Since we are now done with the Call/Invoke, we can delete it. 384 TheCall->getParent()->getInstList().erase(TheCall); 385 386 // Since we are now done with the return instruction, delete it also. 387 Returns[0]->getParent()->getInstList().erase(Returns[0]); 388 389 // We are now done with the inlining. 390 return true; 391 } 392 393 // Otherwise, we have the normal case, of more than one block to inline or 394 // multiple return sites. 395 396 // We want to clone the entire callee function into the hole between the 397 // "starter" and "ender" blocks. How we accomplish this depends on whether 398 // this is an invoke instruction or a call instruction. 399 BasicBlock *AfterCallBB; 400 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) { 401 402 // Add an unconditional branch to make this look like the CallInst case... 403 BranchInst *NewBr = new BranchInst(II->getNormalDest(), TheCall); 404 405 // Split the basic block. This guarantees that no PHI nodes will have to be 406 // updated due to new incoming edges, and make the invoke case more 407 // symmetric to the call case. 408 AfterCallBB = OrigBB->splitBasicBlock(NewBr, 409 CalledFunc->getName()+".exit"); 410 411 } else { // It's a call 412 // If this is a call instruction, we need to split the basic block that 413 // the call lives in. 414 // 415 AfterCallBB = OrigBB->splitBasicBlock(TheCall, 416 CalledFunc->getName()+".exit"); 417 } 418 419 // Change the branch that used to go to AfterCallBB to branch to the first 420 // basic block of the inlined function. 421 // 422 TerminatorInst *Br = OrigBB->getTerminator(); 423 assert(Br && Br->getOpcode() == Instruction::Br && 424 "splitBasicBlock broken!"); 425 Br->setOperand(0, FirstNewBlock); 426 427 428 // Now that the function is correct, make it a little bit nicer. In 429 // particular, move the basic blocks inserted from the end of the function 430 // into the space made by splitting the source basic block. 431 // 432 Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(), 433 FirstNewBlock, Caller->end()); 434 435 // Handle all of the return instructions that we just cloned in, and eliminate 436 // any users of the original call/invoke instruction. 437 if (Returns.size() > 1) { 438 // The PHI node should go at the front of the new basic block to merge all 439 // possible incoming values. 440 // 441 PHINode *PHI = 0; 442 if (!TheCall->use_empty()) { 443 PHI = new PHINode(CalledFunc->getReturnType(), 444 TheCall->getName(), AfterCallBB->begin()); 445 446 // Anything that used the result of the function call should now use the 447 // PHI node as their operand. 448 // 449 TheCall->replaceAllUsesWith(PHI); 450 } 451 452 // Loop over all of the return instructions, turning them into unconditional 453 // branches to the merge point now, and adding entries to the PHI node as 454 // appropriate. 455 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 456 ReturnInst *RI = Returns[i]; 457 458 if (PHI) { 459 assert(RI->getReturnValue() && "Ret should have value!"); 460 assert(RI->getReturnValue()->getType() == PHI->getType() && 461 "Ret value not consistent in function!"); 462 PHI->addIncoming(RI->getReturnValue(), RI->getParent()); 463 } 464 465 // Add a branch to the merge point where the PHI node lives if it exists. 466 new BranchInst(AfterCallBB, RI); 467 468 // Delete the return instruction now 469 RI->getParent()->getInstList().erase(RI); 470 } 471 472 } else if (!Returns.empty()) { 473 // Otherwise, if there is exactly one return value, just replace anything 474 // using the return value of the call with the computed value. 475 if (!TheCall->use_empty()) 476 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue()); 477 478 // Splice the code from the return block into the block that it will return 479 // to, which contains the code that was after the call. 480 BasicBlock *ReturnBB = Returns[0]->getParent(); 481 AfterCallBB->getInstList().splice(AfterCallBB->begin(), 482 ReturnBB->getInstList()); 483 484 // Update PHI nodes that use the ReturnBB to use the AfterCallBB. 485 ReturnBB->replaceAllUsesWith(AfterCallBB); 486 487 // Delete the return instruction now and empty ReturnBB now. 488 Returns[0]->eraseFromParent(); 489 ReturnBB->eraseFromParent(); 490 } else if (!TheCall->use_empty()) { 491 // No returns, but something is using the return value of the call. Just 492 // nuke the result. 493 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType())); 494 } 495 496 // Since we are now done with the Call/Invoke, we can delete it. 497 TheCall->eraseFromParent(); 498 499 // We should always be able to fold the entry block of the function into the 500 // single predecessor of the block... 501 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!"); 502 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0); 503 504 // Splice the code entry block into calling block, right before the 505 // unconditional branch. 506 OrigBB->getInstList().splice(Br, CalleeEntry->getInstList()); 507 CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes 508 509 // Remove the unconditional branch. 510 OrigBB->getInstList().erase(Br); 511 512 // Now we can remove the CalleeEntry block, which is now empty. 513 Caller->getBasicBlockList().erase(CalleeEntry); 514 515 return true; 516} 517