1 //===- InlineFunction.cpp - Code to perform function inlining -------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements inlining of a function into a call site, resolving
11 // parameters and the return value as appropriate.
13 //===----------------------------------------------------------------------===//
15 #include "llvm/Transforms/Utils/Cloning.h"
16 #include "llvm/Constants.h"
17 #include "llvm/DerivedTypes.h"
18 #include "llvm/LLVMContext.h"
19 #include "llvm/Module.h"
20 #include "llvm/Instructions.h"
21 #include "llvm/IntrinsicInst.h"
22 #include "llvm/Intrinsics.h"
23 #include "llvm/Attributes.h"
24 #include "llvm/Analysis/CallGraph.h"
25 #include "llvm/Analysis/DebugInfo.h"
26 #include "llvm/Target/TargetData.h"
27 #include "llvm/ADT/SmallVector.h"
28 #include "llvm/ADT/StringExtras.h"
29 #include "llvm/Support/CallSite.h"
32 bool llvm::InlineFunction(CallInst *CI, CallGraph *CG, const TargetData *TD,
33 SmallVectorImpl<AllocaInst*> *StaticAllocas) {
34 return InlineFunction(CallSite(CI), CG, TD, StaticAllocas);
36 bool llvm::InlineFunction(InvokeInst *II, CallGraph *CG, const TargetData *TD,
37 SmallVectorImpl<AllocaInst*> *StaticAllocas) {
38 return InlineFunction(CallSite(II), CG, TD, StaticAllocas);
42 /// HandleCallsInBlockInlinedThroughInvoke - When we inline a basic block into
43 /// an invoke, we have to turn all of the calls that can throw into
44 /// invokes. This function analyze BB to see if there are any calls, and if so,
45 /// it rewrites them to be invokes that jump to InvokeDest and fills in the PHI
46 /// nodes in that block with the values specified in InvokeDestPHIValues.
48 static void HandleCallsInBlockInlinedThroughInvoke(BasicBlock *BB,
49 BasicBlock *InvokeDest,
50 const SmallVectorImpl<Value*> &InvokeDestPHIValues) {
51 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) {
52 Instruction *I = BBI++;
54 // We only need to check for function calls: inlined invoke
55 // instructions require no special handling.
56 CallInst *CI = dyn_cast<CallInst>(I);
57 if (CI == 0) continue;
59 // If this call cannot unwind, don't convert it to an invoke.
60 if (CI->doesNotThrow())
63 // Convert this function call into an invoke instruction.
64 // First, split the basic block.
65 BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc");
67 // Next, create the new invoke instruction, inserting it at the end
68 // of the old basic block.
69 SmallVector<Value*, 8> InvokeArgs(CI->op_begin()+1, CI->op_end());
71 InvokeInst::Create(CI->getCalledValue(), Split, InvokeDest,
72 InvokeArgs.begin(), InvokeArgs.end(),
73 CI->getName(), BB->getTerminator());
74 II->setCallingConv(CI->getCallingConv());
75 II->setAttributes(CI->getAttributes());
77 // Make sure that anything using the call now uses the invoke! This also
78 // updates the CallGraph if present.
79 CI->replaceAllUsesWith(II);
81 // Delete the unconditional branch inserted by splitBasicBlock
82 BB->getInstList().pop_back();
83 Split->getInstList().pop_front(); // Delete the original call
85 // Update any PHI nodes in the exceptional block to indicate that
86 // there is now a new entry in them.
88 for (BasicBlock::iterator I = InvokeDest->begin();
89 isa<PHINode>(I); ++I, ++i)
90 cast<PHINode>(I)->addIncoming(InvokeDestPHIValues[i], BB);
92 // This basic block is now complete, the caller will continue scanning the
99 /// HandleInlinedInvoke - If we inlined an invoke site, we need to convert calls
100 /// in the body of the inlined function into invokes and turn unwind
101 /// instructions into branches to the invoke unwind dest.
103 /// II is the invoke instruction being inlined. FirstNewBlock is the first
104 /// block of the inlined code (the last block is the end of the function),
105 /// and InlineCodeInfo is information about the code that got inlined.
106 static void HandleInlinedInvoke(InvokeInst *II, BasicBlock *FirstNewBlock,
107 ClonedCodeInfo &InlinedCodeInfo) {
108 BasicBlock *InvokeDest = II->getUnwindDest();
109 SmallVector<Value*, 8> InvokeDestPHIValues;
111 // If there are PHI nodes in the unwind destination block, we need to
112 // keep track of which values came into them from this invoke, then remove
113 // the entry for this block.
114 BasicBlock *InvokeBlock = II->getParent();
115 for (BasicBlock::iterator I = InvokeDest->begin(); isa<PHINode>(I); ++I) {
116 PHINode *PN = cast<PHINode>(I);
117 // Save the value to use for this edge.
118 InvokeDestPHIValues.push_back(PN->getIncomingValueForBlock(InvokeBlock));
121 Function *Caller = FirstNewBlock->getParent();
123 // The inlined code is currently at the end of the function, scan from the
124 // start of the inlined code to its end, checking for stuff we need to
125 // rewrite. If the code doesn't have calls or unwinds, we know there is
126 // nothing to rewrite.
127 if (!InlinedCodeInfo.ContainsCalls && !InlinedCodeInfo.ContainsUnwinds) {
128 // Now that everything is happy, we have one final detail. The PHI nodes in
129 // the exception destination block still have entries due to the original
130 // invoke instruction. Eliminate these entries (which might even delete the
132 InvokeDest->removePredecessor(II->getParent());
136 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); BB != E; ++BB){
137 if (InlinedCodeInfo.ContainsCalls)
138 HandleCallsInBlockInlinedThroughInvoke(BB, InvokeDest,
139 InvokeDestPHIValues);
141 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
142 // An UnwindInst requires special handling when it gets inlined into an
143 // invoke site. Once this happens, we know that the unwind would cause
144 // a control transfer to the invoke exception destination, so we can
145 // transform it into a direct branch to the exception destination.
146 BranchInst::Create(InvokeDest, UI);
148 // Delete the unwind instruction!
149 UI->eraseFromParent();
151 // Update any PHI nodes in the exceptional block to indicate that
152 // there is now a new entry in them.
154 for (BasicBlock::iterator I = InvokeDest->begin();
155 isa<PHINode>(I); ++I, ++i) {
156 PHINode *PN = cast<PHINode>(I);
157 PN->addIncoming(InvokeDestPHIValues[i], BB);
162 // Now that everything is happy, we have one final detail. The PHI nodes in
163 // the exception destination block still have entries due to the original
164 // invoke instruction. Eliminate these entries (which might even delete the
166 InvokeDest->removePredecessor(II->getParent());
169 /// UpdateCallGraphAfterInlining - Once we have cloned code over from a callee
170 /// into the caller, update the specified callgraph to reflect the changes we
171 /// made. Note that it's possible that not all code was copied over, so only
172 /// some edges of the callgraph may remain.
173 static void UpdateCallGraphAfterInlining(CallSite CS,
174 Function::iterator FirstNewBlock,
175 DenseMap<const Value*, Value*> &ValueMap,
177 const Function *Caller = CS.getInstruction()->getParent()->getParent();
178 const Function *Callee = CS.getCalledFunction();
179 CallGraphNode *CalleeNode = CG[Callee];
180 CallGraphNode *CallerNode = CG[Caller];
182 // Since we inlined some uninlined call sites in the callee into the caller,
183 // add edges from the caller to all of the callees of the callee.
184 CallGraphNode::iterator I = CalleeNode->begin(), E = CalleeNode->end();
186 // Consider the case where CalleeNode == CallerNode.
187 CallGraphNode::CalledFunctionsVector CallCache;
188 if (CalleeNode == CallerNode) {
189 CallCache.assign(I, E);
190 I = CallCache.begin();
194 for (; I != E; ++I) {
195 const Value *OrigCall = I->first;
197 DenseMap<const Value*, Value*>::iterator VMI = ValueMap.find(OrigCall);
198 // Only copy the edge if the call was inlined!
199 if (VMI == ValueMap.end() || VMI->second == 0)
202 // If the call was inlined, but then constant folded, there is no edge to
203 // add. Check for this case.
204 if (Instruction *NewCall = dyn_cast<Instruction>(VMI->second))
205 CallerNode->addCalledFunction(CallSite::get(NewCall), I->second);
208 // Update the call graph by deleting the edge from Callee to Caller. We must
209 // do this after the loop above in case Caller and Callee are the same.
210 CallerNode->removeCallEdgeFor(CS);
213 // InlineFunction - This function inlines the called function into the basic
214 // block of the caller. This returns false if it is not possible to inline this
215 // call. The program is still in a well defined state if this occurs though.
217 // Note that this only does one level of inlining. For example, if the
218 // instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
219 // exists in the instruction stream. Similiarly this will inline a recursive
220 // function by one level.
222 bool llvm::InlineFunction(CallSite CS, CallGraph *CG, const TargetData *TD,
223 SmallVectorImpl<AllocaInst*> *StaticAllocas) {
224 Instruction *TheCall = CS.getInstruction();
225 LLVMContext &Context = TheCall->getContext();
226 assert(TheCall->getParent() && TheCall->getParent()->getParent() &&
227 "Instruction not in function!");
229 const Function *CalledFunc = CS.getCalledFunction();
230 if (CalledFunc == 0 || // Can't inline external function or indirect
231 CalledFunc->isDeclaration() || // call, or call to a vararg function!
232 CalledFunc->getFunctionType()->isVarArg()) return false;
235 // If the call to the callee is not a tail call, we must clear the 'tail'
236 // flags on any calls that we inline.
237 bool MustClearTailCallFlags =
238 !(isa<CallInst>(TheCall) && cast<CallInst>(TheCall)->isTailCall());
240 // If the call to the callee cannot throw, set the 'nounwind' flag on any
241 // calls that we inline.
242 bool MarkNoUnwind = CS.doesNotThrow();
244 BasicBlock *OrigBB = TheCall->getParent();
245 Function *Caller = OrigBB->getParent();
247 // GC poses two hazards to inlining, which only occur when the callee has GC:
248 // 1. If the caller has no GC, then the callee's GC must be propagated to the
250 // 2. If the caller has a differing GC, it is invalid to inline.
251 if (CalledFunc->hasGC()) {
252 if (!Caller->hasGC())
253 Caller->setGC(CalledFunc->getGC());
254 else if (CalledFunc->getGC() != Caller->getGC())
258 // Get an iterator to the last basic block in the function, which will have
259 // the new function inlined after it.
261 Function::iterator LastBlock = &Caller->back();
263 // Make sure to capture all of the return instructions from the cloned
265 SmallVector<ReturnInst*, 8> Returns;
266 ClonedCodeInfo InlinedFunctionInfo;
267 Function::iterator FirstNewBlock;
269 { // Scope to destroy ValueMap after cloning.
270 DenseMap<const Value*, Value*> ValueMap;
272 assert(CalledFunc->arg_size() == CS.arg_size() &&
273 "No varargs calls can be inlined!");
275 // Calculate the vector of arguments to pass into the function cloner, which
276 // matches up the formal to the actual argument values.
277 CallSite::arg_iterator AI = CS.arg_begin();
279 for (Function::const_arg_iterator I = CalledFunc->arg_begin(),
280 E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) {
281 Value *ActualArg = *AI;
283 // When byval arguments actually inlined, we need to make the copy implied
284 // by them explicit. However, we don't do this if the callee is readonly
285 // or readnone, because the copy would be unneeded: the callee doesn't
286 // modify the struct.
287 if (CalledFunc->paramHasAttr(ArgNo+1, Attribute::ByVal) &&
288 !CalledFunc->onlyReadsMemory()) {
289 const Type *AggTy = cast<PointerType>(I->getType())->getElementType();
290 const Type *VoidPtrTy =
291 Type::getInt8PtrTy(Context);
293 // Create the alloca. If we have TargetData, use nice alignment.
295 if (TD) Align = TD->getPrefTypeAlignment(AggTy);
296 Value *NewAlloca = new AllocaInst(AggTy, 0, Align,
298 &*Caller->begin()->begin());
300 const Type *Tys[3] = {VoidPtrTy, VoidPtrTy, Type::getInt64Ty(Context)};
301 Function *MemCpyFn = Intrinsic::getDeclaration(Caller->getParent(),
304 Value *DestCast = new BitCastInst(NewAlloca, VoidPtrTy, "tmp", TheCall);
305 Value *SrcCast = new BitCastInst(*AI, VoidPtrTy, "tmp", TheCall);
309 Size = ConstantExpr::getSizeOf(AggTy);
311 Size = ConstantInt::get(Type::getInt64Ty(Context),
312 TD->getTypeStoreSize(AggTy));
314 // Always generate a memcpy of alignment 1 here because we don't know
315 // the alignment of the src pointer. Other optimizations can infer
317 Value *CallArgs[] = {
318 DestCast, SrcCast, Size,
319 ConstantInt::get(Type::getInt32Ty(Context), 1),
320 ConstantInt::get(Type::getInt1Ty(Context), 0)
322 CallInst *TheMemCpy =
323 CallInst::Create(MemCpyFn, CallArgs, CallArgs+5, "", TheCall);
325 // If we have a call graph, update it.
327 CallGraphNode *MemCpyCGN = CG->getOrInsertFunction(MemCpyFn);
328 CallGraphNode *CallerNode = (*CG)[Caller];
329 CallerNode->addCalledFunction(TheMemCpy, MemCpyCGN);
332 // Uses of the argument in the function should use our new alloca
334 ActualArg = NewAlloca;
337 ValueMap[I] = ActualArg;
340 // We want the inliner to prune the code as it copies. We would LOVE to
341 // have no dead or constant instructions leftover after inlining occurs
342 // (which can happen, e.g., because an argument was constant), but we'll be
343 // happy with whatever the cloner can do.
344 CloneAndPruneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i",
345 &InlinedFunctionInfo, TD, TheCall);
347 // Remember the first block that is newly cloned over.
348 FirstNewBlock = LastBlock; ++FirstNewBlock;
350 // Update the callgraph if requested.
352 UpdateCallGraphAfterInlining(CS, FirstNewBlock, ValueMap, *CG);
355 // If there are any alloca instructions in the block that used to be the entry
356 // block for the callee, move them to the entry block of the caller. First
357 // calculate which instruction they should be inserted before. We insert the
358 // instructions at the end of the current alloca list.
361 BasicBlock::iterator InsertPoint = Caller->begin()->begin();
362 for (BasicBlock::iterator I = FirstNewBlock->begin(),
363 E = FirstNewBlock->end(); I != E; ) {
364 AllocaInst *AI = dyn_cast<AllocaInst>(I++);
365 if (AI == 0) continue;
367 // If the alloca is now dead, remove it. This often occurs due to code
369 if (AI->use_empty()) {
370 AI->eraseFromParent();
374 if (!isa<Constant>(AI->getArraySize()))
377 // Keep track of the static allocas that we inline into the caller if the
378 // StaticAllocas pointer is non-null.
379 if (StaticAllocas) StaticAllocas->push_back(AI);
381 // Scan for the block of allocas that we can move over, and move them
383 while (isa<AllocaInst>(I) &&
384 isa<Constant>(cast<AllocaInst>(I)->getArraySize())) {
385 if (StaticAllocas) StaticAllocas->push_back(cast<AllocaInst>(I));
389 // Transfer all of the allocas over in a block. Using splice means
390 // that the instructions aren't removed from the symbol table, then
392 Caller->getEntryBlock().getInstList().splice(InsertPoint,
393 FirstNewBlock->getInstList(),
398 // If the inlined code contained dynamic alloca instructions, wrap the inlined
399 // code with llvm.stacksave/llvm.stackrestore intrinsics.
400 if (InlinedFunctionInfo.ContainsDynamicAllocas) {
401 Module *M = Caller->getParent();
402 // Get the two intrinsics we care about.
403 Function *StackSave = Intrinsic::getDeclaration(M, Intrinsic::stacksave);
404 Function *StackRestore=Intrinsic::getDeclaration(M,Intrinsic::stackrestore);
406 // If we are preserving the callgraph, add edges to the stacksave/restore
407 // functions for the calls we insert.
408 CallGraphNode *StackSaveCGN = 0, *StackRestoreCGN = 0, *CallerNode = 0;
410 StackSaveCGN = CG->getOrInsertFunction(StackSave);
411 StackRestoreCGN = CG->getOrInsertFunction(StackRestore);
412 CallerNode = (*CG)[Caller];
415 // Insert the llvm.stacksave.
416 CallInst *SavedPtr = CallInst::Create(StackSave, "savedstack",
417 FirstNewBlock->begin());
418 if (CG) CallerNode->addCalledFunction(SavedPtr, StackSaveCGN);
420 // Insert a call to llvm.stackrestore before any return instructions in the
422 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
423 CallInst *CI = CallInst::Create(StackRestore, SavedPtr, "", Returns[i]);
424 if (CG) CallerNode->addCalledFunction(CI, StackRestoreCGN);
427 // Count the number of StackRestore calls we insert.
428 unsigned NumStackRestores = Returns.size();
430 // If we are inlining an invoke instruction, insert restores before each
431 // unwind. These unwinds will be rewritten into branches later.
432 if (InlinedFunctionInfo.ContainsUnwinds && isa<InvokeInst>(TheCall)) {
433 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
435 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
436 CallInst *CI = CallInst::Create(StackRestore, SavedPtr, "", UI);
437 if (CG) CallerNode->addCalledFunction(CI, StackRestoreCGN);
443 // If we are inlining tail call instruction through a call site that isn't
444 // marked 'tail', we must remove the tail marker for any calls in the inlined
445 // code. Also, calls inlined through a 'nounwind' call site should be marked
447 if (InlinedFunctionInfo.ContainsCalls &&
448 (MustClearTailCallFlags || MarkNoUnwind)) {
449 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
451 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
452 if (CallInst *CI = dyn_cast<CallInst>(I)) {
453 if (MustClearTailCallFlags)
454 CI->setTailCall(false);
456 CI->setDoesNotThrow();
460 // If we are inlining through a 'nounwind' call site then any inlined 'unwind'
461 // instructions are unreachable.
462 if (InlinedFunctionInfo.ContainsUnwinds && MarkNoUnwind)
463 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
465 TerminatorInst *Term = BB->getTerminator();
466 if (isa<UnwindInst>(Term)) {
467 new UnreachableInst(Context, Term);
468 BB->getInstList().erase(Term);
472 // If we are inlining for an invoke instruction, we must make sure to rewrite
473 // any inlined 'unwind' instructions into branches to the invoke exception
474 // destination, and call instructions into invoke instructions.
475 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
476 HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo);
478 // If we cloned in _exactly one_ basic block, and if that block ends in a
479 // return instruction, we splice the body of the inlined callee directly into
480 // the calling basic block.
481 if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) {
482 // Move all of the instructions right before the call.
483 OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(),
484 FirstNewBlock->begin(), FirstNewBlock->end());
485 // Remove the cloned basic block.
486 Caller->getBasicBlockList().pop_back();
488 // If the call site was an invoke instruction, add a branch to the normal
490 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
491 BranchInst::Create(II->getNormalDest(), TheCall);
493 // If the return instruction returned a value, replace uses of the call with
494 // uses of the returned value.
495 if (!TheCall->use_empty()) {
496 ReturnInst *R = Returns[0];
497 if (TheCall == R->getReturnValue())
498 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
500 TheCall->replaceAllUsesWith(R->getReturnValue());
502 // Since we are now done with the Call/Invoke, we can delete it.
503 TheCall->eraseFromParent();
505 // Since we are now done with the return instruction, delete it also.
506 Returns[0]->eraseFromParent();
508 // We are now done with the inlining.
512 // Otherwise, we have the normal case, of more than one block to inline or
513 // multiple return sites.
515 // We want to clone the entire callee function into the hole between the
516 // "starter" and "ender" blocks. How we accomplish this depends on whether
517 // this is an invoke instruction or a call instruction.
518 BasicBlock *AfterCallBB;
519 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
521 // Add an unconditional branch to make this look like the CallInst case...
522 BranchInst *NewBr = BranchInst::Create(II->getNormalDest(), TheCall);
524 // Split the basic block. This guarantees that no PHI nodes will have to be
525 // updated due to new incoming edges, and make the invoke case more
526 // symmetric to the call case.
527 AfterCallBB = OrigBB->splitBasicBlock(NewBr,
528 CalledFunc->getName()+".exit");
530 } else { // It's a call
531 // If this is a call instruction, we need to split the basic block that
532 // the call lives in.
534 AfterCallBB = OrigBB->splitBasicBlock(TheCall,
535 CalledFunc->getName()+".exit");
538 // Change the branch that used to go to AfterCallBB to branch to the first
539 // basic block of the inlined function.
541 TerminatorInst *Br = OrigBB->getTerminator();
542 assert(Br && Br->getOpcode() == Instruction::Br &&
543 "splitBasicBlock broken!");
544 Br->setOperand(0, FirstNewBlock);
547 // Now that the function is correct, make it a little bit nicer. In
548 // particular, move the basic blocks inserted from the end of the function
549 // into the space made by splitting the source basic block.
550 Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(),
551 FirstNewBlock, Caller->end());
553 // Handle all of the return instructions that we just cloned in, and eliminate
554 // any users of the original call/invoke instruction.
555 const Type *RTy = CalledFunc->getReturnType();
557 if (Returns.size() > 1) {
558 // The PHI node should go at the front of the new basic block to merge all
559 // possible incoming values.
561 if (!TheCall->use_empty()) {
562 PHI = PHINode::Create(RTy, TheCall->getName(),
563 AfterCallBB->begin());
564 // Anything that used the result of the function call should now use the
565 // PHI node as their operand.
566 TheCall->replaceAllUsesWith(PHI);
569 // Loop over all of the return instructions adding entries to the PHI node
572 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
573 ReturnInst *RI = Returns[i];
574 assert(RI->getReturnValue()->getType() == PHI->getType() &&
575 "Ret value not consistent in function!");
576 PHI->addIncoming(RI->getReturnValue(), RI->getParent());
579 // Now that we inserted the PHI, check to see if it has a single value
580 // (e.g. all the entries are the same or undef). If so, remove the PHI so
581 // it doesn't block other optimizations.
582 if (Value *V = PHI->hasConstantValue()) {
583 PHI->replaceAllUsesWith(V);
584 PHI->eraseFromParent();
589 // Add a branch to the merge points and remove return instructions.
590 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
591 ReturnInst *RI = Returns[i];
592 BranchInst::Create(AfterCallBB, RI);
593 RI->eraseFromParent();
595 } else if (!Returns.empty()) {
596 // Otherwise, if there is exactly one return value, just replace anything
597 // using the return value of the call with the computed value.
598 if (!TheCall->use_empty()) {
599 if (TheCall == Returns[0]->getReturnValue())
600 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
602 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue());
605 // Splice the code from the return block into the block that it will return
606 // to, which contains the code that was after the call.
607 BasicBlock *ReturnBB = Returns[0]->getParent();
608 AfterCallBB->getInstList().splice(AfterCallBB->begin(),
609 ReturnBB->getInstList());
611 // Update PHI nodes that use the ReturnBB to use the AfterCallBB.
612 ReturnBB->replaceAllUsesWith(AfterCallBB);
614 // Delete the return instruction now and empty ReturnBB now.
615 Returns[0]->eraseFromParent();
616 ReturnBB->eraseFromParent();
617 } else if (!TheCall->use_empty()) {
618 // No returns, but something is using the return value of the call. Just
620 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
623 // Since we are now done with the Call/Invoke, we can delete it.
624 TheCall->eraseFromParent();
626 // We should always be able to fold the entry block of the function into the
627 // single predecessor of the block...
628 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!");
629 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0);
631 // Splice the code entry block into calling block, right before the
632 // unconditional branch.
633 OrigBB->getInstList().splice(Br, CalleeEntry->getInstList());
634 CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes
636 // Remove the unconditional branch.
637 OrigBB->getInstList().erase(Br);
639 // Now we can remove the CalleeEntry block, which is now empty.
640 Caller->getBasicBlockList().erase(CalleeEntry);