InlineFunction.cpp revision 95c3e48f9557adb6064d580684bb14cacec2f826
1//===- InlineFunction.cpp - Code to perform function inlining -------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// 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// The code in this file for handling inlines through invoke 14// instructions preserves semantics only under some assumptions about 15// the behavior of unwinders which correspond to gcc-style libUnwind 16// exception personality functions. Eventually the IR will be 17// improved to make this unnecessary, but until then, this code is 18// marked [LIBUNWIND]. 19// 20//===----------------------------------------------------------------------===// 21 22#include "llvm/Transforms/Utils/Cloning.h" 23#include "llvm/Constants.h" 24#include "llvm/DerivedTypes.h" 25#include "llvm/Module.h" 26#include "llvm/Instructions.h" 27#include "llvm/IntrinsicInst.h" 28#include "llvm/Intrinsics.h" 29#include "llvm/Attributes.h" 30#include "llvm/Analysis/CallGraph.h" 31#include "llvm/Analysis/DebugInfo.h" 32#include "llvm/Analysis/InstructionSimplify.h" 33#include "llvm/Target/TargetData.h" 34#include "llvm/Transforms/Utils/Local.h" 35#include "llvm/ADT/SmallVector.h" 36#include "llvm/ADT/StringExtras.h" 37#include "llvm/Support/CallSite.h" 38#include "llvm/Support/IRBuilder.h" 39using namespace llvm; 40 41bool llvm::InlineFunction(CallInst *CI, InlineFunctionInfo &IFI) { 42 return InlineFunction(CallSite(CI), IFI); 43} 44bool llvm::InlineFunction(InvokeInst *II, InlineFunctionInfo &IFI) { 45 return InlineFunction(CallSite(II), IFI); 46} 47 48/// [LIBUNWIND] Look for an llvm.eh.exception call in the given block. 49static EHExceptionInst *findExceptionInBlock(BasicBlock *bb) { 50 for (BasicBlock::iterator i = bb->begin(), e = bb->end(); i != e; i++) { 51 EHExceptionInst *exn = dyn_cast<EHExceptionInst>(i); 52 if (exn) return exn; 53 } 54 55 return 0; 56} 57 58/// [LIBUNWIND] Look for the 'best' llvm.eh.selector instruction for 59/// the given llvm.eh.exception call. 60static EHSelectorInst *findSelectorForException(EHExceptionInst *exn) { 61 BasicBlock *exnBlock = exn->getParent(); 62 63 EHSelectorInst *outOfBlockSelector = 0; 64 for (Instruction::use_iterator 65 ui = exn->use_begin(), ue = exn->use_end(); ui != ue; ++ui) { 66 EHSelectorInst *sel = dyn_cast<EHSelectorInst>(*ui); 67 if (!sel) continue; 68 69 // Immediately accept an eh.selector in the same block as the 70 // excepton call. 71 if (sel->getParent() == exnBlock) return sel; 72 73 // Otherwise, use the first selector we see. 74 if (!outOfBlockSelector) outOfBlockSelector = sel; 75 } 76 77 return outOfBlockSelector; 78} 79 80/// [LIBUNWIND] Find the (possibly absent) call to @llvm.eh.selector 81/// in the given landing pad. In principle, llvm.eh.exception is 82/// required to be in the landing pad; in practice, SplitCriticalEdge 83/// can break that invariant, and then inlining can break it further. 84/// There's a real need for a reliable solution here, but until that 85/// happens, we have some fragile workarounds here. 86static EHSelectorInst *findSelectorForLandingPad(BasicBlock *lpad) { 87 // Look for an exception call in the actual landing pad. 88 EHExceptionInst *exn = findExceptionInBlock(lpad); 89 if (exn) return findSelectorForException(exn); 90 91 // Okay, if that failed, look for one in an obvious successor. If 92 // we find one, we'll fix the IR by moving things back to the 93 // landing pad. 94 95 bool dominates = true; // does the lpad dominate the exn call 96 BasicBlock *nonDominated = 0; // if not, the first non-dominated block 97 BasicBlock *lastDominated = 0; // and the block which branched to it 98 99 BasicBlock *exnBlock = lpad; 100 101 // We need to protect against lpads that lead into infinite loops. 102 SmallPtrSet<BasicBlock*,4> visited; 103 visited.insert(exnBlock); 104 105 do { 106 // We're not going to apply this hack to anything more complicated 107 // than a series of unconditional branches, so if the block 108 // doesn't terminate in an unconditional branch, just fail. More 109 // complicated cases can arise when, say, sinking a call into a 110 // split unwind edge and then inlining it; but that can do almost 111 // *anything* to the CFG, including leaving the selector 112 // completely unreachable. The only way to fix that properly is 113 // to (1) prohibit transforms which move the exception or selector 114 // values away from the landing pad, e.g. by producing them with 115 // instructions that are pinned to an edge like a phi, or 116 // producing them with not-really-instructions, and (2) making 117 // transforms which split edges deal with that. 118 BranchInst *branch = dyn_cast<BranchInst>(&exnBlock->back()); 119 if (!branch || branch->isConditional()) return 0; 120 121 BasicBlock *successor = branch->getSuccessor(0); 122 123 // Fail if we found an infinite loop. 124 if (!visited.insert(successor)) return 0; 125 126 // If the successor isn't dominated by exnBlock: 127 if (!successor->getSinglePredecessor()) { 128 // We don't want to have to deal with threading the exception 129 // through multiple levels of phi, so give up if we've already 130 // followed a non-dominating edge. 131 if (!dominates) return 0; 132 133 // Otherwise, remember this as a non-dominating edge. 134 dominates = false; 135 nonDominated = successor; 136 lastDominated = exnBlock; 137 } 138 139 exnBlock = successor; 140 141 // Can we stop here? 142 exn = findExceptionInBlock(exnBlock); 143 } while (!exn); 144 145 // Look for a selector call for the exception we found. 146 EHSelectorInst *selector = findSelectorForException(exn); 147 if (!selector) return 0; 148 149 // The easy case is when the landing pad still dominates the 150 // exception call, in which case we can just move both calls back to 151 // the landing pad. 152 if (dominates) { 153 selector->moveBefore(lpad->getFirstNonPHI()); 154 exn->moveBefore(selector); 155 return selector; 156 } 157 158 // Otherwise, we have to split at the first non-dominating block. 159 // The CFG looks basically like this: 160 // lpad: 161 // phis_0 162 // insnsAndBranches_1 163 // br label %nonDominated 164 // nonDominated: 165 // phis_2 166 // insns_3 167 // %exn = call i8* @llvm.eh.exception() 168 // insnsAndBranches_4 169 // %selector = call @llvm.eh.selector(i8* %exn, ... 170 // We need to turn this into: 171 // lpad: 172 // phis_0 173 // %exn0 = call i8* @llvm.eh.exception() 174 // %selector0 = call @llvm.eh.selector(i8* %exn0, ... 175 // insnsAndBranches_1 176 // br label %split // from lastDominated 177 // nonDominated: 178 // phis_2 (without edge from lastDominated) 179 // %exn1 = call i8* @llvm.eh.exception() 180 // %selector1 = call i8* @llvm.eh.selector(i8* %exn1, ... 181 // br label %split 182 // split: 183 // phis_2 (edge from lastDominated, edge from split) 184 // %exn = phi ... 185 // %selector = phi ... 186 // insns_3 187 // insnsAndBranches_4 188 189 assert(nonDominated); 190 assert(lastDominated); 191 192 // First, make clones of the intrinsics to go in lpad. 193 EHExceptionInst *lpadExn = cast<EHExceptionInst>(exn->clone()); 194 EHSelectorInst *lpadSelector = cast<EHSelectorInst>(selector->clone()); 195 lpadSelector->setArgOperand(0, lpadExn); 196 lpadSelector->insertBefore(lpad->getFirstNonPHI()); 197 lpadExn->insertBefore(lpadSelector); 198 199 // Split the non-dominated block. 200 BasicBlock *split = 201 nonDominated->splitBasicBlock(nonDominated->getFirstNonPHI(), 202 nonDominated->getName() + ".lpad-fix"); 203 204 // Redirect the last dominated branch there. 205 cast<BranchInst>(lastDominated->back()).setSuccessor(0, split); 206 207 // Move the existing intrinsics to the end of the old block. 208 selector->moveBefore(&nonDominated->back()); 209 exn->moveBefore(selector); 210 211 Instruction *splitIP = &split->front(); 212 213 // For all the phis in nonDominated, make a new phi in split to join 214 // that phi with the edge from lastDominated. 215 for (BasicBlock::iterator 216 i = nonDominated->begin(), e = nonDominated->end(); i != e; ++i) { 217 PHINode *phi = dyn_cast<PHINode>(i); 218 if (!phi) break; 219 220 PHINode *splitPhi = PHINode::Create(phi->getType(), 2, phi->getName(), 221 splitIP); 222 phi->replaceAllUsesWith(splitPhi); 223 splitPhi->addIncoming(phi, nonDominated); 224 splitPhi->addIncoming(phi->removeIncomingValue(lastDominated), 225 lastDominated); 226 } 227 228 // Make new phis for the exception and selector. 229 PHINode *exnPhi = PHINode::Create(exn->getType(), 2, "", splitIP); 230 exn->replaceAllUsesWith(exnPhi); 231 selector->setArgOperand(0, exn); // except for this use 232 exnPhi->addIncoming(exn, nonDominated); 233 exnPhi->addIncoming(lpadExn, lastDominated); 234 235 PHINode *selectorPhi = PHINode::Create(selector->getType(), 2, "", splitIP); 236 selector->replaceAllUsesWith(selectorPhi); 237 selectorPhi->addIncoming(selector, nonDominated); 238 selectorPhi->addIncoming(lpadSelector, lastDominated); 239 240 return lpadSelector; 241} 242 243namespace { 244 /// A class for recording information about inlining through an invoke. 245 class InvokeInliningInfo { 246 BasicBlock *OuterUnwindDest; 247 EHSelectorInst *OuterSelector; 248 BasicBlock *InnerUnwindDest; 249 PHINode *InnerExceptionPHI; 250 PHINode *InnerSelectorPHI; 251 SmallVector<Value*, 8> UnwindDestPHIValues; 252 253 public: 254 InvokeInliningInfo(InvokeInst *II) : 255 OuterUnwindDest(II->getUnwindDest()), OuterSelector(0), 256 InnerUnwindDest(0), InnerExceptionPHI(0), InnerSelectorPHI(0) { 257 258 // If there are PHI nodes in the unwind destination block, we 259 // need to keep track of which values came into them from the 260 // invoke before removing the edge from this block. 261 llvm::BasicBlock *invokeBB = II->getParent(); 262 for (BasicBlock::iterator I = OuterUnwindDest->begin(); 263 isa<PHINode>(I); ++I) { 264 // Save the value to use for this edge. 265 PHINode *phi = cast<PHINode>(I); 266 UnwindDestPHIValues.push_back(phi->getIncomingValueForBlock(invokeBB)); 267 } 268 } 269 270 /// The outer unwind destination is the target of unwind edges 271 /// introduced for calls within the inlined function. 272 BasicBlock *getOuterUnwindDest() const { 273 return OuterUnwindDest; 274 } 275 276 EHSelectorInst *getOuterSelector() { 277 if (!OuterSelector) 278 OuterSelector = findSelectorForLandingPad(OuterUnwindDest); 279 return OuterSelector; 280 } 281 282 BasicBlock *getInnerUnwindDest(); 283 284 bool forwardEHResume(CallInst *call, BasicBlock *src); 285 286 /// Add incoming-PHI values to the unwind destination block for 287 /// the given basic block, using the values for the original 288 /// invoke's source block. 289 void addIncomingPHIValuesFor(BasicBlock *BB) const { 290 addIncomingPHIValuesForInto(BB, OuterUnwindDest); 291 } 292 293 void addIncomingPHIValuesForInto(BasicBlock *src, BasicBlock *dest) const { 294 BasicBlock::iterator I = dest->begin(); 295 for (unsigned i = 0, e = UnwindDestPHIValues.size(); i != e; ++i, ++I) { 296 PHINode *phi = cast<PHINode>(I); 297 phi->addIncoming(UnwindDestPHIValues[i], src); 298 } 299 } 300 }; 301} 302 303/// Get or create a target for the branch out of rewritten calls to 304/// llvm.eh.resume. 305BasicBlock *InvokeInliningInfo::getInnerUnwindDest() { 306 if (InnerUnwindDest) return InnerUnwindDest; 307 308 // Find and hoist the llvm.eh.exception and llvm.eh.selector calls 309 // in the outer landing pad to immediately following the phis. 310 EHSelectorInst *selector = getOuterSelector(); 311 if (!selector) return 0; 312 313 // The call to llvm.eh.exception *must* be in the landing pad. 314 Instruction *exn = cast<Instruction>(selector->getArgOperand(0)); 315 assert(exn->getParent() == OuterUnwindDest); 316 317 // TODO: recognize when we've already done this, so that we don't 318 // get a linear number of these when inlining calls into lots of 319 // invokes with the same landing pad. 320 321 // Do the hoisting. 322 Instruction *splitPoint = exn->getParent()->getFirstNonPHI(); 323 assert(splitPoint != selector && "selector-on-exception dominance broken!"); 324 if (splitPoint == exn) { 325 selector->removeFromParent(); 326 selector->insertAfter(exn); 327 splitPoint = selector->getNextNode(); 328 } else { 329 exn->moveBefore(splitPoint); 330 selector->moveBefore(splitPoint); 331 } 332 333 // Split the landing pad. 334 InnerUnwindDest = OuterUnwindDest->splitBasicBlock(splitPoint, 335 OuterUnwindDest->getName() + ".body"); 336 337 // The number of incoming edges we expect to the inner landing pad. 338 const unsigned phiCapacity = 2; 339 340 // Create corresponding new phis for all the phis in the outer landing pad. 341 BasicBlock::iterator insertPoint = InnerUnwindDest->begin(); 342 BasicBlock::iterator I = OuterUnwindDest->begin(); 343 for (unsigned i = 0, e = UnwindDestPHIValues.size(); i != e; ++i, ++I) { 344 PHINode *outerPhi = cast<PHINode>(I); 345 PHINode *innerPhi = PHINode::Create(outerPhi->getType(), phiCapacity, 346 outerPhi->getName() + ".lpad-body", 347 insertPoint); 348 outerPhi->replaceAllUsesWith(innerPhi); 349 innerPhi->addIncoming(outerPhi, OuterUnwindDest); 350 } 351 352 // Create a phi for the exception value... 353 InnerExceptionPHI = PHINode::Create(exn->getType(), phiCapacity, 354 "exn.lpad-body", insertPoint); 355 exn->replaceAllUsesWith(InnerExceptionPHI); 356 selector->setArgOperand(0, exn); // restore this use 357 InnerExceptionPHI->addIncoming(exn, OuterUnwindDest); 358 359 // ...and the selector. 360 InnerSelectorPHI = PHINode::Create(selector->getType(), phiCapacity, 361 "selector.lpad-body", insertPoint); 362 selector->replaceAllUsesWith(InnerSelectorPHI); 363 InnerSelectorPHI->addIncoming(selector, OuterUnwindDest); 364 365 // All done. 366 return InnerUnwindDest; 367} 368 369/// [LIBUNWIND] Try to forward the given call, which logically occurs 370/// at the end of the given block, as a branch to the inner unwind 371/// block. Returns true if the call was forwarded. 372bool InvokeInliningInfo::forwardEHResume(CallInst *call, BasicBlock *src) { 373 // First, check whether this is a call to the intrinsic. 374 Function *fn = dyn_cast<Function>(call->getCalledValue()); 375 if (!fn || fn->getName() != "llvm.eh.resume") 376 return false; 377 378 // At this point, we need to return true on all paths, because 379 // otherwise we'll construct an invoke of the intrinsic, which is 380 // not well-formed. 381 382 // Try to find or make an inner unwind dest, which will fail if we 383 // can't find a selector call for the outer unwind dest. 384 BasicBlock *dest = getInnerUnwindDest(); 385 bool hasSelector = (dest != 0); 386 387 // If we failed, just use the outer unwind dest, dropping the 388 // exception and selector on the floor. 389 if (!hasSelector) 390 dest = OuterUnwindDest; 391 392 // Make a branch. 393 BranchInst::Create(dest, src); 394 395 // Update the phis in the destination. They were inserted in an 396 // order which makes this work. 397 addIncomingPHIValuesForInto(src, dest); 398 399 if (hasSelector) { 400 InnerExceptionPHI->addIncoming(call->getArgOperand(0), src); 401 InnerSelectorPHI->addIncoming(call->getArgOperand(1), src); 402 } 403 404 return true; 405} 406 407/// [LIBUNWIND] Check whether this selector is "only cleanups": 408/// call i32 @llvm.eh.selector(blah, blah, i32 0) 409static bool isCleanupOnlySelector(EHSelectorInst *selector) { 410 if (selector->getNumArgOperands() != 3) return false; 411 ConstantInt *val = dyn_cast<ConstantInt>(selector->getArgOperand(2)); 412 return (val && val->isZero()); 413} 414 415/// HandleCallsInBlockInlinedThroughInvoke - When we inline a basic block into 416/// an invoke, we have to turn all of the calls that can throw into 417/// invokes. This function analyze BB to see if there are any calls, and if so, 418/// it rewrites them to be invokes that jump to InvokeDest and fills in the PHI 419/// nodes in that block with the values specified in InvokeDestPHIValues. 420/// 421/// Returns true to indicate that the next block should be skipped. 422static bool HandleCallsInBlockInlinedThroughInvoke(BasicBlock *BB, 423 InvokeInliningInfo &Invoke) { 424 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) { 425 Instruction *I = BBI++; 426 427 // We only need to check for function calls: inlined invoke 428 // instructions require no special handling. 429 CallInst *CI = dyn_cast<CallInst>(I); 430 if (CI == 0) continue; 431 432 // LIBUNWIND: merge selector instructions. 433 if (EHSelectorInst *Inner = dyn_cast<EHSelectorInst>(CI)) { 434 EHSelectorInst *Outer = Invoke.getOuterSelector(); 435 if (!Outer) continue; 436 437 bool innerIsOnlyCleanup = isCleanupOnlySelector(Inner); 438 bool outerIsOnlyCleanup = isCleanupOnlySelector(Outer); 439 440 // If both selectors contain only cleanups, we don't need to do 441 // anything. TODO: this is really just a very specific instance 442 // of a much more general optimization. 443 if (innerIsOnlyCleanup && outerIsOnlyCleanup) continue; 444 445 // Otherwise, we just append the outer selector to the inner selector. 446 SmallVector<Value*, 16> NewSelector; 447 for (unsigned i = 0, e = Inner->getNumArgOperands(); i != e; ++i) 448 NewSelector.push_back(Inner->getArgOperand(i)); 449 for (unsigned i = 2, e = Outer->getNumArgOperands(); i != e; ++i) 450 NewSelector.push_back(Outer->getArgOperand(i)); 451 452 CallInst *NewInner = 453 IRBuilder<>(Inner).CreateCall(Inner->getCalledValue(), 454 NewSelector.begin(), 455 NewSelector.end()); 456 // No need to copy attributes, calling convention, etc. 457 NewInner->takeName(Inner); 458 Inner->replaceAllUsesWith(NewInner); 459 Inner->eraseFromParent(); 460 continue; 461 } 462 463 // If this call cannot unwind, don't convert it to an invoke. 464 if (CI->doesNotThrow()) 465 continue; 466 467 // Convert this function call into an invoke instruction. 468 // First, split the basic block. 469 BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc"); 470 471 // Delete the unconditional branch inserted by splitBasicBlock 472 BB->getInstList().pop_back(); 473 474 // LIBUNWIND: If this is a call to @llvm.eh.resume, just branch 475 // directly to the new landing pad. 476 if (Invoke.forwardEHResume(CI, BB)) { 477 // TODO: 'Split' is now unreachable; clean it up. 478 479 // We want to leave the original call intact so that the call 480 // graph and other structures won't get misled. We also have to 481 // avoid processing the next block, or we'll iterate here forever. 482 return true; 483 } 484 485 // Otherwise, create the new invoke instruction. 486 ImmutableCallSite CS(CI); 487 SmallVector<Value*, 8> InvokeArgs(CS.arg_begin(), CS.arg_end()); 488 InvokeInst *II = 489 InvokeInst::Create(CI->getCalledValue(), Split, 490 Invoke.getOuterUnwindDest(), 491 InvokeArgs.begin(), InvokeArgs.end(), 492 CI->getName(), BB); 493 II->setCallingConv(CI->getCallingConv()); 494 II->setAttributes(CI->getAttributes()); 495 496 // Make sure that anything using the call now uses the invoke! This also 497 // updates the CallGraph if present, because it uses a WeakVH. 498 CI->replaceAllUsesWith(II); 499 500 Split->getInstList().pop_front(); // Delete the original call 501 502 // Update any PHI nodes in the exceptional block to indicate that 503 // there is now a new entry in them. 504 Invoke.addIncomingPHIValuesFor(BB); 505 return false; 506 } 507 508 return false; 509} 510 511 512/// HandleInlinedInvoke - If we inlined an invoke site, we need to convert calls 513/// in the body of the inlined function into invokes and turn unwind 514/// instructions into branches to the invoke unwind dest. 515/// 516/// II is the invoke instruction being inlined. FirstNewBlock is the first 517/// block of the inlined code (the last block is the end of the function), 518/// and InlineCodeInfo is information about the code that got inlined. 519static void HandleInlinedInvoke(InvokeInst *II, BasicBlock *FirstNewBlock, 520 ClonedCodeInfo &InlinedCodeInfo) { 521 BasicBlock *InvokeDest = II->getUnwindDest(); 522 523 Function *Caller = FirstNewBlock->getParent(); 524 525 // The inlined code is currently at the end of the function, scan from the 526 // start of the inlined code to its end, checking for stuff we need to 527 // rewrite. If the code doesn't have calls or unwinds, we know there is 528 // nothing to rewrite. 529 if (!InlinedCodeInfo.ContainsCalls && !InlinedCodeInfo.ContainsUnwinds) { 530 // Now that everything is happy, we have one final detail. The PHI nodes in 531 // the exception destination block still have entries due to the original 532 // invoke instruction. Eliminate these entries (which might even delete the 533 // PHI node) now. 534 InvokeDest->removePredecessor(II->getParent()); 535 return; 536 } 537 538 InvokeInliningInfo Invoke(II); 539 540 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); BB != E; ++BB){ 541 if (InlinedCodeInfo.ContainsCalls) 542 if (HandleCallsInBlockInlinedThroughInvoke(BB, Invoke)) { 543 // Honor a request to skip the next block. We don't need to 544 // consider UnwindInsts in this case either. 545 ++BB; 546 continue; 547 } 548 549 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 550 // An UnwindInst requires special handling when it gets inlined into an 551 // invoke site. Once this happens, we know that the unwind would cause 552 // a control transfer to the invoke exception destination, so we can 553 // transform it into a direct branch to the exception destination. 554 BranchInst::Create(InvokeDest, UI); 555 556 // Delete the unwind instruction! 557 UI->eraseFromParent(); 558 559 // Update any PHI nodes in the exceptional block to indicate that 560 // there is now a new entry in them. 561 Invoke.addIncomingPHIValuesFor(BB); 562 } 563 } 564 565 // Now that everything is happy, we have one final detail. The PHI nodes in 566 // the exception destination block still have entries due to the original 567 // invoke instruction. Eliminate these entries (which might even delete the 568 // PHI node) now. 569 InvokeDest->removePredecessor(II->getParent()); 570} 571 572/// UpdateCallGraphAfterInlining - Once we have cloned code over from a callee 573/// into the caller, update the specified callgraph to reflect the changes we 574/// made. Note that it's possible that not all code was copied over, so only 575/// some edges of the callgraph may remain. 576static void UpdateCallGraphAfterInlining(CallSite CS, 577 Function::iterator FirstNewBlock, 578 ValueToValueMapTy &VMap, 579 InlineFunctionInfo &IFI) { 580 CallGraph &CG = *IFI.CG; 581 const Function *Caller = CS.getInstruction()->getParent()->getParent(); 582 const Function *Callee = CS.getCalledFunction(); 583 CallGraphNode *CalleeNode = CG[Callee]; 584 CallGraphNode *CallerNode = CG[Caller]; 585 586 // Since we inlined some uninlined call sites in the callee into the caller, 587 // add edges from the caller to all of the callees of the callee. 588 CallGraphNode::iterator I = CalleeNode->begin(), E = CalleeNode->end(); 589 590 // Consider the case where CalleeNode == CallerNode. 591 CallGraphNode::CalledFunctionsVector CallCache; 592 if (CalleeNode == CallerNode) { 593 CallCache.assign(I, E); 594 I = CallCache.begin(); 595 E = CallCache.end(); 596 } 597 598 for (; I != E; ++I) { 599 const Value *OrigCall = I->first; 600 601 ValueToValueMapTy::iterator VMI = VMap.find(OrigCall); 602 // Only copy the edge if the call was inlined! 603 if (VMI == VMap.end() || VMI->second == 0) 604 continue; 605 606 // If the call was inlined, but then constant folded, there is no edge to 607 // add. Check for this case. 608 Instruction *NewCall = dyn_cast<Instruction>(VMI->second); 609 if (NewCall == 0) continue; 610 611 // Remember that this call site got inlined for the client of 612 // InlineFunction. 613 IFI.InlinedCalls.push_back(NewCall); 614 615 // It's possible that inlining the callsite will cause it to go from an 616 // indirect to a direct call by resolving a function pointer. If this 617 // happens, set the callee of the new call site to a more precise 618 // destination. This can also happen if the call graph node of the caller 619 // was just unnecessarily imprecise. 620 if (I->second->getFunction() == 0) 621 if (Function *F = CallSite(NewCall).getCalledFunction()) { 622 // Indirect call site resolved to direct call. 623 CallerNode->addCalledFunction(CallSite(NewCall), CG[F]); 624 625 continue; 626 } 627 628 CallerNode->addCalledFunction(CallSite(NewCall), I->second); 629 } 630 631 // Update the call graph by deleting the edge from Callee to Caller. We must 632 // do this after the loop above in case Caller and Callee are the same. 633 CallerNode->removeCallEdgeFor(CS); 634} 635 636/// HandleByValArgument - When inlining a call site that has a byval argument, 637/// we have to make the implicit memcpy explicit by adding it. 638static Value *HandleByValArgument(Value *Arg, Instruction *TheCall, 639 const Function *CalledFunc, 640 InlineFunctionInfo &IFI, 641 unsigned ByValAlignment) { 642 const Type *AggTy = cast<PointerType>(Arg->getType())->getElementType(); 643 644 // If the called function is readonly, then it could not mutate the caller's 645 // copy of the byval'd memory. In this case, it is safe to elide the copy and 646 // temporary. 647 if (CalledFunc->onlyReadsMemory()) { 648 // If the byval argument has a specified alignment that is greater than the 649 // passed in pointer, then we either have to round up the input pointer or 650 // give up on this transformation. 651 if (ByValAlignment <= 1) // 0 = unspecified, 1 = no particular alignment. 652 return Arg; 653 654 // If the pointer is already known to be sufficiently aligned, or if we can 655 // round it up to a larger alignment, then we don't need a temporary. 656 if (getOrEnforceKnownAlignment(Arg, ByValAlignment, 657 IFI.TD) >= ByValAlignment) 658 return Arg; 659 660 // Otherwise, we have to make a memcpy to get a safe alignment. This is bad 661 // for code quality, but rarely happens and is required for correctness. 662 } 663 664 LLVMContext &Context = Arg->getContext(); 665 666 const Type *VoidPtrTy = Type::getInt8PtrTy(Context); 667 668 // Create the alloca. If we have TargetData, use nice alignment. 669 unsigned Align = 1; 670 if (IFI.TD) 671 Align = IFI.TD->getPrefTypeAlignment(AggTy); 672 673 // If the byval had an alignment specified, we *must* use at least that 674 // alignment, as it is required by the byval argument (and uses of the 675 // pointer inside the callee). 676 Align = std::max(Align, ByValAlignment); 677 678 Function *Caller = TheCall->getParent()->getParent(); 679 680 Value *NewAlloca = new AllocaInst(AggTy, 0, Align, Arg->getName(), 681 &*Caller->begin()->begin()); 682 // Emit a memcpy. 683 const Type *Tys[3] = {VoidPtrTy, VoidPtrTy, Type::getInt64Ty(Context)}; 684 Function *MemCpyFn = Intrinsic::getDeclaration(Caller->getParent(), 685 Intrinsic::memcpy, 686 Tys, 3); 687 Value *DestCast = new BitCastInst(NewAlloca, VoidPtrTy, "tmp", TheCall); 688 Value *SrcCast = new BitCastInst(Arg, VoidPtrTy, "tmp", TheCall); 689 690 Value *Size; 691 if (IFI.TD == 0) 692 Size = ConstantExpr::getSizeOf(AggTy); 693 else 694 Size = ConstantInt::get(Type::getInt64Ty(Context), 695 IFI.TD->getTypeStoreSize(AggTy)); 696 697 // Always generate a memcpy of alignment 1 here because we don't know 698 // the alignment of the src pointer. Other optimizations can infer 699 // better alignment. 700 Value *CallArgs[] = { 701 DestCast, SrcCast, Size, 702 ConstantInt::get(Type::getInt32Ty(Context), 1), 703 ConstantInt::getFalse(Context) // isVolatile 704 }; 705 IRBuilder<>(TheCall).CreateCall(MemCpyFn, CallArgs, CallArgs+5); 706 707 // Uses of the argument in the function should use our new alloca 708 // instead. 709 return NewAlloca; 710} 711 712// isUsedByLifetimeMarker - Check whether this Value is used by a lifetime 713// intrinsic. 714static bool isUsedByLifetimeMarker(Value *V) { 715 for (Value::use_iterator UI = V->use_begin(), UE = V->use_end(); UI != UE; 716 ++UI) { 717 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(*UI)) { 718 switch (II->getIntrinsicID()) { 719 default: break; 720 case Intrinsic::lifetime_start: 721 case Intrinsic::lifetime_end: 722 return true; 723 } 724 } 725 } 726 return false; 727} 728 729// hasLifetimeMarkers - Check whether the given alloca already has 730// lifetime.start or lifetime.end intrinsics. 731static bool hasLifetimeMarkers(AllocaInst *AI) { 732 const Type *Int8PtrTy = Type::getInt8PtrTy(AI->getType()->getContext()); 733 if (AI->getType() == Int8PtrTy) 734 return isUsedByLifetimeMarker(AI); 735 736 // Do a scan to find all the casts to i8*. 737 for (Value::use_iterator I = AI->use_begin(), E = AI->use_end(); I != E; 738 ++I) { 739 if (I->getType() != Int8PtrTy) continue; 740 if (I->stripPointerCasts() != AI) continue; 741 if (isUsedByLifetimeMarker(*I)) 742 return true; 743 } 744 return false; 745} 746 747// InlineFunction - This function inlines the called function into the basic 748// block of the caller. This returns false if it is not possible to inline this 749// call. The program is still in a well defined state if this occurs though. 750// 751// Note that this only does one level of inlining. For example, if the 752// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now 753// exists in the instruction stream. Similarly this will inline a recursive 754// function by one level. 755// 756bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI) { 757 Instruction *TheCall = CS.getInstruction(); 758 LLVMContext &Context = TheCall->getContext(); 759 assert(TheCall->getParent() && TheCall->getParent()->getParent() && 760 "Instruction not in function!"); 761 762 // If IFI has any state in it, zap it before we fill it in. 763 IFI.reset(); 764 765 const Function *CalledFunc = CS.getCalledFunction(); 766 if (CalledFunc == 0 || // Can't inline external function or indirect 767 CalledFunc->isDeclaration() || // call, or call to a vararg function! 768 CalledFunc->getFunctionType()->isVarArg()) return false; 769 770 // If the call to the callee is not a tail call, we must clear the 'tail' 771 // flags on any calls that we inline. 772 bool MustClearTailCallFlags = 773 !(isa<CallInst>(TheCall) && cast<CallInst>(TheCall)->isTailCall()); 774 775 // If the call to the callee cannot throw, set the 'nounwind' flag on any 776 // calls that we inline. 777 bool MarkNoUnwind = CS.doesNotThrow(); 778 779 BasicBlock *OrigBB = TheCall->getParent(); 780 Function *Caller = OrigBB->getParent(); 781 782 // GC poses two hazards to inlining, which only occur when the callee has GC: 783 // 1. If the caller has no GC, then the callee's GC must be propagated to the 784 // caller. 785 // 2. If the caller has a differing GC, it is invalid to inline. 786 if (CalledFunc->hasGC()) { 787 if (!Caller->hasGC()) 788 Caller->setGC(CalledFunc->getGC()); 789 else if (CalledFunc->getGC() != Caller->getGC()) 790 return false; 791 } 792 793 // Get an iterator to the last basic block in the function, which will have 794 // the new function inlined after it. 795 // 796 Function::iterator LastBlock = &Caller->back(); 797 798 // Make sure to capture all of the return instructions from the cloned 799 // function. 800 SmallVector<ReturnInst*, 8> Returns; 801 ClonedCodeInfo InlinedFunctionInfo; 802 Function::iterator FirstNewBlock; 803 804 { // Scope to destroy VMap after cloning. 805 ValueToValueMapTy VMap; 806 807 assert(CalledFunc->arg_size() == CS.arg_size() && 808 "No varargs calls can be inlined!"); 809 810 // Calculate the vector of arguments to pass into the function cloner, which 811 // matches up the formal to the actual argument values. 812 CallSite::arg_iterator AI = CS.arg_begin(); 813 unsigned ArgNo = 0; 814 for (Function::const_arg_iterator I = CalledFunc->arg_begin(), 815 E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) { 816 Value *ActualArg = *AI; 817 818 // When byval arguments actually inlined, we need to make the copy implied 819 // by them explicit. However, we don't do this if the callee is readonly 820 // or readnone, because the copy would be unneeded: the callee doesn't 821 // modify the struct. 822 if (CalledFunc->paramHasAttr(ArgNo+1, Attribute::ByVal)) { 823 ActualArg = HandleByValArgument(ActualArg, TheCall, CalledFunc, IFI, 824 CalledFunc->getParamAlignment(ArgNo+1)); 825 826 // Calls that we inline may use the new alloca, so we need to clear 827 // their 'tail' flags if HandleByValArgument introduced a new alloca and 828 // the callee has calls. 829 MustClearTailCallFlags |= ActualArg != *AI; 830 } 831 832 VMap[I] = ActualArg; 833 } 834 835 // We want the inliner to prune the code as it copies. We would LOVE to 836 // have no dead or constant instructions leftover after inlining occurs 837 // (which can happen, e.g., because an argument was constant), but we'll be 838 // happy with whatever the cloner can do. 839 CloneAndPruneFunctionInto(Caller, CalledFunc, VMap, 840 /*ModuleLevelChanges=*/false, Returns, ".i", 841 &InlinedFunctionInfo, IFI.TD, TheCall); 842 843 // Remember the first block that is newly cloned over. 844 FirstNewBlock = LastBlock; ++FirstNewBlock; 845 846 // Update the callgraph if requested. 847 if (IFI.CG) 848 UpdateCallGraphAfterInlining(CS, FirstNewBlock, VMap, IFI); 849 } 850 851 // If there are any alloca instructions in the block that used to be the entry 852 // block for the callee, move them to the entry block of the caller. First 853 // calculate which instruction they should be inserted before. We insert the 854 // instructions at the end of the current alloca list. 855 // 856 { 857 BasicBlock::iterator InsertPoint = Caller->begin()->begin(); 858 for (BasicBlock::iterator I = FirstNewBlock->begin(), 859 E = FirstNewBlock->end(); I != E; ) { 860 AllocaInst *AI = dyn_cast<AllocaInst>(I++); 861 if (AI == 0) continue; 862 863 // If the alloca is now dead, remove it. This often occurs due to code 864 // specialization. 865 if (AI->use_empty()) { 866 AI->eraseFromParent(); 867 continue; 868 } 869 870 if (!isa<Constant>(AI->getArraySize())) 871 continue; 872 873 // Keep track of the static allocas that we inline into the caller. 874 IFI.StaticAllocas.push_back(AI); 875 876 // Scan for the block of allocas that we can move over, and move them 877 // all at once. 878 while (isa<AllocaInst>(I) && 879 isa<Constant>(cast<AllocaInst>(I)->getArraySize())) { 880 IFI.StaticAllocas.push_back(cast<AllocaInst>(I)); 881 ++I; 882 } 883 884 // Transfer all of the allocas over in a block. Using splice means 885 // that the instructions aren't removed from the symbol table, then 886 // reinserted. 887 Caller->getEntryBlock().getInstList().splice(InsertPoint, 888 FirstNewBlock->getInstList(), 889 AI, I); 890 } 891 } 892 893 // Leave lifetime markers for the static alloca's, scoping them to the 894 // function we just inlined. 895 if (!IFI.StaticAllocas.empty()) { 896 IRBuilder<> builder(FirstNewBlock->begin()); 897 for (unsigned ai = 0, ae = IFI.StaticAllocas.size(); ai != ae; ++ai) { 898 AllocaInst *AI = IFI.StaticAllocas[ai]; 899 900 // If the alloca is already scoped to something smaller than the whole 901 // function then there's no need to add redundant, less accurate markers. 902 if (hasLifetimeMarkers(AI)) 903 continue; 904 905 builder.CreateLifetimeStart(AI); 906 for (unsigned ri = 0, re = Returns.size(); ri != re; ++ri) { 907 IRBuilder<> builder(Returns[ri]); 908 builder.CreateLifetimeEnd(AI); 909 } 910 } 911 } 912 913 // If the inlined code contained dynamic alloca instructions, wrap the inlined 914 // code with llvm.stacksave/llvm.stackrestore intrinsics. 915 if (InlinedFunctionInfo.ContainsDynamicAllocas) { 916 Module *M = Caller->getParent(); 917 // Get the two intrinsics we care about. 918 Function *StackSave = Intrinsic::getDeclaration(M, Intrinsic::stacksave); 919 Function *StackRestore=Intrinsic::getDeclaration(M,Intrinsic::stackrestore); 920 921 // Insert the llvm.stacksave. 922 CallInst *SavedPtr = IRBuilder<>(FirstNewBlock, FirstNewBlock->begin()) 923 .CreateCall(StackSave, "savedstack"); 924 925 // Insert a call to llvm.stackrestore before any return instructions in the 926 // inlined function. 927 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 928 IRBuilder<>(Returns[i]).CreateCall(StackRestore, SavedPtr); 929 } 930 931 // Count the number of StackRestore calls we insert. 932 unsigned NumStackRestores = Returns.size(); 933 934 // If we are inlining an invoke instruction, insert restores before each 935 // unwind. These unwinds will be rewritten into branches later. 936 if (InlinedFunctionInfo.ContainsUnwinds && isa<InvokeInst>(TheCall)) { 937 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 938 BB != E; ++BB) 939 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) { 940 IRBuilder<>(UI).CreateCall(StackRestore, SavedPtr); 941 ++NumStackRestores; 942 } 943 } 944 } 945 946 // If we are inlining tail call instruction through a call site that isn't 947 // marked 'tail', we must remove the tail marker for any calls in the inlined 948 // code. Also, calls inlined through a 'nounwind' call site should be marked 949 // 'nounwind'. 950 if (InlinedFunctionInfo.ContainsCalls && 951 (MustClearTailCallFlags || MarkNoUnwind)) { 952 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 953 BB != E; ++BB) 954 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) 955 if (CallInst *CI = dyn_cast<CallInst>(I)) { 956 if (MustClearTailCallFlags) 957 CI->setTailCall(false); 958 if (MarkNoUnwind) 959 CI->setDoesNotThrow(); 960 } 961 } 962 963 // If we are inlining through a 'nounwind' call site then any inlined 'unwind' 964 // instructions are unreachable. 965 if (InlinedFunctionInfo.ContainsUnwinds && MarkNoUnwind) 966 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); 967 BB != E; ++BB) { 968 TerminatorInst *Term = BB->getTerminator(); 969 if (isa<UnwindInst>(Term)) { 970 new UnreachableInst(Context, Term); 971 BB->getInstList().erase(Term); 972 } 973 } 974 975 // If we are inlining for an invoke instruction, we must make sure to rewrite 976 // any inlined 'unwind' instructions into branches to the invoke exception 977 // destination, and call instructions into invoke instructions. 978 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 979 HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo); 980 981 // If we cloned in _exactly one_ basic block, and if that block ends in a 982 // return instruction, we splice the body of the inlined callee directly into 983 // the calling basic block. 984 if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) { 985 // Move all of the instructions right before the call. 986 OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(), 987 FirstNewBlock->begin(), FirstNewBlock->end()); 988 // Remove the cloned basic block. 989 Caller->getBasicBlockList().pop_back(); 990 991 // If the call site was an invoke instruction, add a branch to the normal 992 // destination. 993 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) 994 BranchInst::Create(II->getNormalDest(), TheCall); 995 996 // If the return instruction returned a value, replace uses of the call with 997 // uses of the returned value. 998 if (!TheCall->use_empty()) { 999 ReturnInst *R = Returns[0]; 1000 if (TheCall == R->getReturnValue()) 1001 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType())); 1002 else 1003 TheCall->replaceAllUsesWith(R->getReturnValue()); 1004 } 1005 // Since we are now done with the Call/Invoke, we can delete it. 1006 TheCall->eraseFromParent(); 1007 1008 // Since we are now done with the return instruction, delete it also. 1009 Returns[0]->eraseFromParent(); 1010 1011 // We are now done with the inlining. 1012 return true; 1013 } 1014 1015 // Otherwise, we have the normal case, of more than one block to inline or 1016 // multiple return sites. 1017 1018 // We want to clone the entire callee function into the hole between the 1019 // "starter" and "ender" blocks. How we accomplish this depends on whether 1020 // this is an invoke instruction or a call instruction. 1021 BasicBlock *AfterCallBB; 1022 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) { 1023 1024 // Add an unconditional branch to make this look like the CallInst case... 1025 BranchInst *NewBr = BranchInst::Create(II->getNormalDest(), TheCall); 1026 1027 // Split the basic block. This guarantees that no PHI nodes will have to be 1028 // updated due to new incoming edges, and make the invoke case more 1029 // symmetric to the call case. 1030 AfterCallBB = OrigBB->splitBasicBlock(NewBr, 1031 CalledFunc->getName()+".exit"); 1032 1033 } else { // It's a call 1034 // If this is a call instruction, we need to split the basic block that 1035 // the call lives in. 1036 // 1037 AfterCallBB = OrigBB->splitBasicBlock(TheCall, 1038 CalledFunc->getName()+".exit"); 1039 } 1040 1041 // Change the branch that used to go to AfterCallBB to branch to the first 1042 // basic block of the inlined function. 1043 // 1044 TerminatorInst *Br = OrigBB->getTerminator(); 1045 assert(Br && Br->getOpcode() == Instruction::Br && 1046 "splitBasicBlock broken!"); 1047 Br->setOperand(0, FirstNewBlock); 1048 1049 1050 // Now that the function is correct, make it a little bit nicer. In 1051 // particular, move the basic blocks inserted from the end of the function 1052 // into the space made by splitting the source basic block. 1053 Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(), 1054 FirstNewBlock, Caller->end()); 1055 1056 // Handle all of the return instructions that we just cloned in, and eliminate 1057 // any users of the original call/invoke instruction. 1058 const Type *RTy = CalledFunc->getReturnType(); 1059 1060 PHINode *PHI = 0; 1061 if (Returns.size() > 1) { 1062 // The PHI node should go at the front of the new basic block to merge all 1063 // possible incoming values. 1064 if (!TheCall->use_empty()) { 1065 PHI = PHINode::Create(RTy, Returns.size(), TheCall->getName(), 1066 AfterCallBB->begin()); 1067 // Anything that used the result of the function call should now use the 1068 // PHI node as their operand. 1069 TheCall->replaceAllUsesWith(PHI); 1070 } 1071 1072 // Loop over all of the return instructions adding entries to the PHI node 1073 // as appropriate. 1074 if (PHI) { 1075 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 1076 ReturnInst *RI = Returns[i]; 1077 assert(RI->getReturnValue()->getType() == PHI->getType() && 1078 "Ret value not consistent in function!"); 1079 PHI->addIncoming(RI->getReturnValue(), RI->getParent()); 1080 } 1081 } 1082 1083 1084 // Add a branch to the merge points and remove return instructions. 1085 for (unsigned i = 0, e = Returns.size(); i != e; ++i) { 1086 ReturnInst *RI = Returns[i]; 1087 BranchInst::Create(AfterCallBB, RI); 1088 RI->eraseFromParent(); 1089 } 1090 } else if (!Returns.empty()) { 1091 // Otherwise, if there is exactly one return value, just replace anything 1092 // using the return value of the call with the computed value. 1093 if (!TheCall->use_empty()) { 1094 if (TheCall == Returns[0]->getReturnValue()) 1095 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType())); 1096 else 1097 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue()); 1098 } 1099 1100 // Update PHI nodes that use the ReturnBB to use the AfterCallBB. 1101 BasicBlock *ReturnBB = Returns[0]->getParent(); 1102 ReturnBB->replaceAllUsesWith(AfterCallBB); 1103 1104 // Splice the code from the return block into the block that it will return 1105 // to, which contains the code that was after the call. 1106 AfterCallBB->getInstList().splice(AfterCallBB->begin(), 1107 ReturnBB->getInstList()); 1108 1109 // Delete the return instruction now and empty ReturnBB now. 1110 Returns[0]->eraseFromParent(); 1111 ReturnBB->eraseFromParent(); 1112 } else if (!TheCall->use_empty()) { 1113 // No returns, but something is using the return value of the call. Just 1114 // nuke the result. 1115 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType())); 1116 } 1117 1118 // Since we are now done with the Call/Invoke, we can delete it. 1119 TheCall->eraseFromParent(); 1120 1121 // We should always be able to fold the entry block of the function into the 1122 // single predecessor of the block... 1123 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!"); 1124 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0); 1125 1126 // Splice the code entry block into calling block, right before the 1127 // unconditional branch. 1128 CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes 1129 OrigBB->getInstList().splice(Br, CalleeEntry->getInstList()); 1130 1131 // Remove the unconditional branch. 1132 OrigBB->getInstList().erase(Br); 1133 1134 // Now we can remove the CalleeEntry block, which is now empty. 1135 Caller->getBasicBlockList().erase(CalleeEntry); 1136 1137 // If we inserted a phi node, check to see if it has a single value (e.g. all 1138 // the entries are the same or undef). If so, remove the PHI so it doesn't 1139 // block other optimizations. 1140 if (PHI) 1141 if (Value *V = SimplifyInstruction(PHI, IFI.TD)) { 1142 PHI->replaceAllUsesWith(V); 1143 PHI->eraseFromParent(); 1144 } 1145 1146 return true; 1147} 1148