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/Module.h"
19 #include "llvm/Instructions.h"
20 #include "llvm/IntrinsicInst.h"
21 #include "llvm/Intrinsics.h"
22 #include "llvm/Attributes.h"
23 #include "llvm/Analysis/CallGraph.h"
24 #include "llvm/Analysis/DebugInfo.h"
25 #include "llvm/Target/TargetData.h"
26 #include "llvm/ADT/SmallVector.h"
27 #include "llvm/ADT/StringExtras.h"
28 #include "llvm/Support/CallSite.h"
31 bool llvm::InlineFunction(CallInst *CI, InlineFunctionInfo &IFI) {
32 return InlineFunction(CallSite(CI), IFI);
34 bool llvm::InlineFunction(InvokeInst *II, InlineFunctionInfo &IFI) {
35 return InlineFunction(CallSite(II), IFI);
39 /// HandleCallsInBlockInlinedThroughInvoke - When we inline a basic block into
40 /// an invoke, we have to turn all of the calls that can throw into
41 /// invokes. This function analyze BB to see if there are any calls, and if so,
42 /// it rewrites them to be invokes that jump to InvokeDest and fills in the PHI
43 /// nodes in that block with the values specified in InvokeDestPHIValues.
45 static void HandleCallsInBlockInlinedThroughInvoke(BasicBlock *BB,
46 BasicBlock *InvokeDest,
47 const SmallVectorImpl<Value*> &InvokeDestPHIValues) {
48 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) {
49 Instruction *I = BBI++;
51 // We only need to check for function calls: inlined invoke
52 // instructions require no special handling.
53 CallInst *CI = dyn_cast<CallInst>(I);
54 if (CI == 0) continue;
56 // If this call cannot unwind, don't convert it to an invoke.
57 if (CI->doesNotThrow())
60 // Convert this function call into an invoke instruction.
61 // First, split the basic block.
62 BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc");
64 // Next, create the new invoke instruction, inserting it at the end
65 // of the old basic block.
66 SmallVector<Value*, 8> InvokeArgs(CI->op_begin()+1, CI->op_end());
68 InvokeInst::Create(CI->getCalledValue(), Split, InvokeDest,
69 InvokeArgs.begin(), InvokeArgs.end(),
70 CI->getName(), BB->getTerminator());
71 II->setCallingConv(CI->getCallingConv());
72 II->setAttributes(CI->getAttributes());
74 // Make sure that anything using the call now uses the invoke! This also
75 // updates the CallGraph if present.
76 CI->replaceAllUsesWith(II);
78 // Delete the unconditional branch inserted by splitBasicBlock
79 BB->getInstList().pop_back();
80 Split->getInstList().pop_front(); // Delete the original call
82 // Update any PHI nodes in the exceptional block to indicate that
83 // there is now a new entry in them.
85 for (BasicBlock::iterator I = InvokeDest->begin();
86 isa<PHINode>(I); ++I, ++i)
87 cast<PHINode>(I)->addIncoming(InvokeDestPHIValues[i], BB);
89 // This basic block is now complete, the caller will continue scanning the
96 /// HandleInlinedInvoke - If we inlined an invoke site, we need to convert calls
97 /// in the body of the inlined function into invokes and turn unwind
98 /// instructions into branches to the invoke unwind dest.
100 /// II is the invoke instruction being inlined. FirstNewBlock is the first
101 /// block of the inlined code (the last block is the end of the function),
102 /// and InlineCodeInfo is information about the code that got inlined.
103 static void HandleInlinedInvoke(InvokeInst *II, BasicBlock *FirstNewBlock,
104 ClonedCodeInfo &InlinedCodeInfo) {
105 BasicBlock *InvokeDest = II->getUnwindDest();
106 SmallVector<Value*, 8> InvokeDestPHIValues;
108 // If there are PHI nodes in the unwind destination block, we need to
109 // keep track of which values came into them from this invoke, then remove
110 // the entry for this block.
111 BasicBlock *InvokeBlock = II->getParent();
112 for (BasicBlock::iterator I = InvokeDest->begin(); isa<PHINode>(I); ++I) {
113 PHINode *PN = cast<PHINode>(I);
114 // Save the value to use for this edge.
115 InvokeDestPHIValues.push_back(PN->getIncomingValueForBlock(InvokeBlock));
118 Function *Caller = FirstNewBlock->getParent();
120 // The inlined code is currently at the end of the function, scan from the
121 // start of the inlined code to its end, checking for stuff we need to
122 // rewrite. If the code doesn't have calls or unwinds, we know there is
123 // nothing to rewrite.
124 if (!InlinedCodeInfo.ContainsCalls && !InlinedCodeInfo.ContainsUnwinds) {
125 // Now that everything is happy, we have one final detail. The PHI nodes in
126 // the exception destination block still have entries due to the original
127 // invoke instruction. Eliminate these entries (which might even delete the
129 InvokeDest->removePredecessor(II->getParent());
133 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); BB != E; ++BB){
134 if (InlinedCodeInfo.ContainsCalls)
135 HandleCallsInBlockInlinedThroughInvoke(BB, InvokeDest,
136 InvokeDestPHIValues);
138 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
139 // An UnwindInst requires special handling when it gets inlined into an
140 // invoke site. Once this happens, we know that the unwind would cause
141 // a control transfer to the invoke exception destination, so we can
142 // transform it into a direct branch to the exception destination.
143 BranchInst::Create(InvokeDest, UI);
145 // Delete the unwind instruction!
146 UI->eraseFromParent();
148 // Update any PHI nodes in the exceptional block to indicate that
149 // there is now a new entry in them.
151 for (BasicBlock::iterator I = InvokeDest->begin();
152 isa<PHINode>(I); ++I, ++i) {
153 PHINode *PN = cast<PHINode>(I);
154 PN->addIncoming(InvokeDestPHIValues[i], BB);
159 // Now that everything is happy, we have one final detail. The PHI nodes in
160 // the exception destination block still have entries due to the original
161 // invoke instruction. Eliminate these entries (which might even delete the
163 InvokeDest->removePredecessor(II->getParent());
166 /// UpdateCallGraphAfterInlining - Once we have cloned code over from a callee
167 /// into the caller, update the specified callgraph to reflect the changes we
168 /// made. Note that it's possible that not all code was copied over, so only
169 /// some edges of the callgraph may remain.
170 static void UpdateCallGraphAfterInlining(CallSite CS,
171 Function::iterator FirstNewBlock,
172 DenseMap<const Value*, Value*> &ValueMap,
174 const Function *Caller = CS.getInstruction()->getParent()->getParent();
175 const Function *Callee = CS.getCalledFunction();
176 CallGraphNode *CalleeNode = CG[Callee];
177 CallGraphNode *CallerNode = CG[Caller];
179 // Since we inlined some uninlined call sites in the callee into the caller,
180 // add edges from the caller to all of the callees of the callee.
181 CallGraphNode::iterator I = CalleeNode->begin(), E = CalleeNode->end();
183 // Consider the case where CalleeNode == CallerNode.
184 CallGraphNode::CalledFunctionsVector CallCache;
185 if (CalleeNode == CallerNode) {
186 CallCache.assign(I, E);
187 I = CallCache.begin();
191 for (; I != E; ++I) {
192 const Value *OrigCall = I->first;
194 DenseMap<const Value*, Value*>::iterator VMI = ValueMap.find(OrigCall);
195 // Only copy the edge if the call was inlined!
196 if (VMI == ValueMap.end() || VMI->second == 0)
199 // If the call was inlined, but then constant folded, there is no edge to
200 // add. Check for this case.
201 Instruction *NewCall = dyn_cast<Instruction>(VMI->second);
202 if (NewCall == 0) continue;
204 // It's possible that inlining the callsite will cause it to go from an
205 // indirect to a direct call by resolving a function pointer. If this
206 // happens, set the callee of the new call site to a more precise
207 // destination. This can also happen if the call graph node of the caller
208 // was just unnecessarily imprecise.
209 if (I->second->getFunction() == 0)
210 if (Function *F = CallSite(NewCall).getCalledFunction()) {
211 // Indirect call site resolved to direct call.
212 CallerNode->addCalledFunction(CallSite::get(NewCall), CG[F]);
216 CallerNode->addCalledFunction(CallSite::get(NewCall), I->second);
219 // Update the call graph by deleting the edge from Callee to Caller. We must
220 // do this after the loop above in case Caller and Callee are the same.
221 CallerNode->removeCallEdgeFor(CS);
224 // InlineFunction - This function inlines the called function into the basic
225 // block of the caller. This returns false if it is not possible to inline this
226 // call. The program is still in a well defined state if this occurs though.
228 // Note that this only does one level of inlining. For example, if the
229 // instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
230 // exists in the instruction stream. Similiarly this will inline a recursive
231 // function by one level.
233 bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI) {
234 Instruction *TheCall = CS.getInstruction();
235 LLVMContext &Context = TheCall->getContext();
236 assert(TheCall->getParent() && TheCall->getParent()->getParent() &&
237 "Instruction not in function!");
239 // If IFI has any state in it, zap it before we fill it in.
242 const Function *CalledFunc = CS.getCalledFunction();
243 if (CalledFunc == 0 || // Can't inline external function or indirect
244 CalledFunc->isDeclaration() || // call, or call to a vararg function!
245 CalledFunc->getFunctionType()->isVarArg()) return false;
248 // If the call to the callee is not a tail call, we must clear the 'tail'
249 // flags on any calls that we inline.
250 bool MustClearTailCallFlags =
251 !(isa<CallInst>(TheCall) && cast<CallInst>(TheCall)->isTailCall());
253 // If the call to the callee cannot throw, set the 'nounwind' flag on any
254 // calls that we inline.
255 bool MarkNoUnwind = CS.doesNotThrow();
257 BasicBlock *OrigBB = TheCall->getParent();
258 Function *Caller = OrigBB->getParent();
260 // GC poses two hazards to inlining, which only occur when the callee has GC:
261 // 1. If the caller has no GC, then the callee's GC must be propagated to the
263 // 2. If the caller has a differing GC, it is invalid to inline.
264 if (CalledFunc->hasGC()) {
265 if (!Caller->hasGC())
266 Caller->setGC(CalledFunc->getGC());
267 else if (CalledFunc->getGC() != Caller->getGC())
271 // Get an iterator to the last basic block in the function, which will have
272 // the new function inlined after it.
274 Function::iterator LastBlock = &Caller->back();
276 // Make sure to capture all of the return instructions from the cloned
278 SmallVector<ReturnInst*, 8> Returns;
279 ClonedCodeInfo InlinedFunctionInfo;
280 Function::iterator FirstNewBlock;
282 { // Scope to destroy ValueMap after cloning.
283 DenseMap<const Value*, Value*> ValueMap;
285 assert(CalledFunc->arg_size() == CS.arg_size() &&
286 "No varargs calls can be inlined!");
288 // Calculate the vector of arguments to pass into the function cloner, which
289 // matches up the formal to the actual argument values.
290 CallSite::arg_iterator AI = CS.arg_begin();
292 for (Function::const_arg_iterator I = CalledFunc->arg_begin(),
293 E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) {
294 Value *ActualArg = *AI;
296 // When byval arguments actually inlined, we need to make the copy implied
297 // by them explicit. However, we don't do this if the callee is readonly
298 // or readnone, because the copy would be unneeded: the callee doesn't
299 // modify the struct.
300 if (CalledFunc->paramHasAttr(ArgNo+1, Attribute::ByVal) &&
301 !CalledFunc->onlyReadsMemory()) {
302 const Type *AggTy = cast<PointerType>(I->getType())->getElementType();
303 const Type *VoidPtrTy =
304 Type::getInt8PtrTy(Context);
306 // Create the alloca. If we have TargetData, use nice alignment.
308 if (IFI.TD) Align = IFI.TD->getPrefTypeAlignment(AggTy);
309 Value *NewAlloca = new AllocaInst(AggTy, 0, Align,
311 &*Caller->begin()->begin());
313 const Type *Tys[3] = {VoidPtrTy, VoidPtrTy, Type::getInt64Ty(Context)};
314 Function *MemCpyFn = Intrinsic::getDeclaration(Caller->getParent(),
317 Value *DestCast = new BitCastInst(NewAlloca, VoidPtrTy, "tmp", TheCall);
318 Value *SrcCast = new BitCastInst(*AI, VoidPtrTy, "tmp", TheCall);
322 Size = ConstantExpr::getSizeOf(AggTy);
324 Size = ConstantInt::get(Type::getInt64Ty(Context),
325 IFI.TD->getTypeStoreSize(AggTy));
327 // Always generate a memcpy of alignment 1 here because we don't know
328 // the alignment of the src pointer. Other optimizations can infer
330 Value *CallArgs[] = {
331 DestCast, SrcCast, Size,
332 ConstantInt::get(Type::getInt32Ty(Context), 1),
333 ConstantInt::get(Type::getInt1Ty(Context), 0)
335 CallInst *TheMemCpy =
336 CallInst::Create(MemCpyFn, CallArgs, CallArgs+5, "", TheCall);
338 // If we have a call graph, update it.
339 if (CallGraph *CG = IFI.CG) {
340 CallGraphNode *MemCpyCGN = CG->getOrInsertFunction(MemCpyFn);
341 CallGraphNode *CallerNode = (*CG)[Caller];
342 CallerNode->addCalledFunction(TheMemCpy, MemCpyCGN);
345 // Uses of the argument in the function should use our new alloca
347 ActualArg = NewAlloca;
350 ValueMap[I] = ActualArg;
353 // We want the inliner to prune the code as it copies. We would LOVE to
354 // have no dead or constant instructions leftover after inlining occurs
355 // (which can happen, e.g., because an argument was constant), but we'll be
356 // happy with whatever the cloner can do.
357 CloneAndPruneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i",
358 &InlinedFunctionInfo, IFI.TD, TheCall);
360 // Remember the first block that is newly cloned over.
361 FirstNewBlock = LastBlock; ++FirstNewBlock;
363 // Update the callgraph if requested.
365 UpdateCallGraphAfterInlining(CS, FirstNewBlock, ValueMap, *IFI.CG);
368 // If there are any alloca instructions in the block that used to be the entry
369 // block for the callee, move them to the entry block of the caller. First
370 // calculate which instruction they should be inserted before. We insert the
371 // instructions at the end of the current alloca list.
374 BasicBlock::iterator InsertPoint = Caller->begin()->begin();
375 for (BasicBlock::iterator I = FirstNewBlock->begin(),
376 E = FirstNewBlock->end(); I != E; ) {
377 AllocaInst *AI = dyn_cast<AllocaInst>(I++);
378 if (AI == 0) continue;
380 // If the alloca is now dead, remove it. This often occurs due to code
382 if (AI->use_empty()) {
383 AI->eraseFromParent();
387 if (!isa<Constant>(AI->getArraySize()))
390 // Keep track of the static allocas that we inline into the caller if the
391 // StaticAllocas pointer is non-null.
392 IFI.StaticAllocas.push_back(AI);
394 // Scan for the block of allocas that we can move over, and move them
396 while (isa<AllocaInst>(I) &&
397 isa<Constant>(cast<AllocaInst>(I)->getArraySize())) {
398 IFI.StaticAllocas.push_back(cast<AllocaInst>(I));
402 // Transfer all of the allocas over in a block. Using splice means
403 // that the instructions aren't removed from the symbol table, then
405 Caller->getEntryBlock().getInstList().splice(InsertPoint,
406 FirstNewBlock->getInstList(),
411 // If the inlined code contained dynamic alloca instructions, wrap the inlined
412 // code with llvm.stacksave/llvm.stackrestore intrinsics.
413 if (InlinedFunctionInfo.ContainsDynamicAllocas) {
414 Module *M = Caller->getParent();
415 // Get the two intrinsics we care about.
416 Function *StackSave = Intrinsic::getDeclaration(M, Intrinsic::stacksave);
417 Function *StackRestore=Intrinsic::getDeclaration(M,Intrinsic::stackrestore);
419 // If we are preserving the callgraph, add edges to the stacksave/restore
420 // functions for the calls we insert.
421 CallGraphNode *StackSaveCGN = 0, *StackRestoreCGN = 0, *CallerNode = 0;
422 if (CallGraph *CG = IFI.CG) {
423 StackSaveCGN = CG->getOrInsertFunction(StackSave);
424 StackRestoreCGN = CG->getOrInsertFunction(StackRestore);
425 CallerNode = (*CG)[Caller];
428 // Insert the llvm.stacksave.
429 CallInst *SavedPtr = CallInst::Create(StackSave, "savedstack",
430 FirstNewBlock->begin());
431 if (IFI.CG) CallerNode->addCalledFunction(SavedPtr, StackSaveCGN);
433 // Insert a call to llvm.stackrestore before any return instructions in the
435 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
436 CallInst *CI = CallInst::Create(StackRestore, SavedPtr, "", Returns[i]);
437 if (IFI.CG) CallerNode->addCalledFunction(CI, StackRestoreCGN);
440 // Count the number of StackRestore calls we insert.
441 unsigned NumStackRestores = Returns.size();
443 // If we are inlining an invoke instruction, insert restores before each
444 // unwind. These unwinds will be rewritten into branches later.
445 if (InlinedFunctionInfo.ContainsUnwinds && isa<InvokeInst>(TheCall)) {
446 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
448 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
449 CallInst *CI = CallInst::Create(StackRestore, SavedPtr, "", UI);
450 if (IFI.CG) CallerNode->addCalledFunction(CI, StackRestoreCGN);
456 // If we are inlining tail call instruction through a call site that isn't
457 // marked 'tail', we must remove the tail marker for any calls in the inlined
458 // code. Also, calls inlined through a 'nounwind' call site should be marked
460 if (InlinedFunctionInfo.ContainsCalls &&
461 (MustClearTailCallFlags || MarkNoUnwind)) {
462 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
464 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
465 if (CallInst *CI = dyn_cast<CallInst>(I)) {
466 if (MustClearTailCallFlags)
467 CI->setTailCall(false);
469 CI->setDoesNotThrow();
473 // If we are inlining through a 'nounwind' call site then any inlined 'unwind'
474 // instructions are unreachable.
475 if (InlinedFunctionInfo.ContainsUnwinds && MarkNoUnwind)
476 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
478 TerminatorInst *Term = BB->getTerminator();
479 if (isa<UnwindInst>(Term)) {
480 new UnreachableInst(Context, Term);
481 BB->getInstList().erase(Term);
485 // If we are inlining for an invoke instruction, we must make sure to rewrite
486 // any inlined 'unwind' instructions into branches to the invoke exception
487 // destination, and call instructions into invoke instructions.
488 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
489 HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo);
491 // If we cloned in _exactly one_ basic block, and if that block ends in a
492 // return instruction, we splice the body of the inlined callee directly into
493 // the calling basic block.
494 if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) {
495 // Move all of the instructions right before the call.
496 OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(),
497 FirstNewBlock->begin(), FirstNewBlock->end());
498 // Remove the cloned basic block.
499 Caller->getBasicBlockList().pop_back();
501 // If the call site was an invoke instruction, add a branch to the normal
503 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
504 BranchInst::Create(II->getNormalDest(), TheCall);
506 // If the return instruction returned a value, replace uses of the call with
507 // uses of the returned value.
508 if (!TheCall->use_empty()) {
509 ReturnInst *R = Returns[0];
510 if (TheCall == R->getReturnValue())
511 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
513 TheCall->replaceAllUsesWith(R->getReturnValue());
515 // Since we are now done with the Call/Invoke, we can delete it.
516 TheCall->eraseFromParent();
518 // Since we are now done with the return instruction, delete it also.
519 Returns[0]->eraseFromParent();
521 // We are now done with the inlining.
525 // Otherwise, we have the normal case, of more than one block to inline or
526 // multiple return sites.
528 // We want to clone the entire callee function into the hole between the
529 // "starter" and "ender" blocks. How we accomplish this depends on whether
530 // this is an invoke instruction or a call instruction.
531 BasicBlock *AfterCallBB;
532 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
534 // Add an unconditional branch to make this look like the CallInst case...
535 BranchInst *NewBr = BranchInst::Create(II->getNormalDest(), TheCall);
537 // Split the basic block. This guarantees that no PHI nodes will have to be
538 // updated due to new incoming edges, and make the invoke case more
539 // symmetric to the call case.
540 AfterCallBB = OrigBB->splitBasicBlock(NewBr,
541 CalledFunc->getName()+".exit");
543 } else { // It's a call
544 // If this is a call instruction, we need to split the basic block that
545 // the call lives in.
547 AfterCallBB = OrigBB->splitBasicBlock(TheCall,
548 CalledFunc->getName()+".exit");
551 // Change the branch that used to go to AfterCallBB to branch to the first
552 // basic block of the inlined function.
554 TerminatorInst *Br = OrigBB->getTerminator();
555 assert(Br && Br->getOpcode() == Instruction::Br &&
556 "splitBasicBlock broken!");
557 Br->setOperand(0, FirstNewBlock);
560 // Now that the function is correct, make it a little bit nicer. In
561 // particular, move the basic blocks inserted from the end of the function
562 // into the space made by splitting the source basic block.
563 Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(),
564 FirstNewBlock, Caller->end());
566 // Handle all of the return instructions that we just cloned in, and eliminate
567 // any users of the original call/invoke instruction.
568 const Type *RTy = CalledFunc->getReturnType();
570 if (Returns.size() > 1) {
571 // The PHI node should go at the front of the new basic block to merge all
572 // possible incoming values.
574 if (!TheCall->use_empty()) {
575 PHI = PHINode::Create(RTy, TheCall->getName(),
576 AfterCallBB->begin());
577 // Anything that used the result of the function call should now use the
578 // PHI node as their operand.
579 TheCall->replaceAllUsesWith(PHI);
582 // Loop over all of the return instructions adding entries to the PHI node
585 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
586 ReturnInst *RI = Returns[i];
587 assert(RI->getReturnValue()->getType() == PHI->getType() &&
588 "Ret value not consistent in function!");
589 PHI->addIncoming(RI->getReturnValue(), RI->getParent());
592 // Now that we inserted the PHI, check to see if it has a single value
593 // (e.g. all the entries are the same or undef). If so, remove the PHI so
594 // it doesn't block other optimizations.
595 if (Value *V = PHI->hasConstantValue()) {
596 PHI->replaceAllUsesWith(V);
597 PHI->eraseFromParent();
602 // Add a branch to the merge points and remove return instructions.
603 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
604 ReturnInst *RI = Returns[i];
605 BranchInst::Create(AfterCallBB, RI);
606 RI->eraseFromParent();
608 } else if (!Returns.empty()) {
609 // Otherwise, if there is exactly one return value, just replace anything
610 // using the return value of the call with the computed value.
611 if (!TheCall->use_empty()) {
612 if (TheCall == Returns[0]->getReturnValue())
613 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
615 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue());
618 // Splice the code from the return block into the block that it will return
619 // to, which contains the code that was after the call.
620 BasicBlock *ReturnBB = Returns[0]->getParent();
621 AfterCallBB->getInstList().splice(AfterCallBB->begin(),
622 ReturnBB->getInstList());
624 // Update PHI nodes that use the ReturnBB to use the AfterCallBB.
625 ReturnBB->replaceAllUsesWith(AfterCallBB);
627 // Delete the return instruction now and empty ReturnBB now.
628 Returns[0]->eraseFromParent();
629 ReturnBB->eraseFromParent();
630 } else if (!TheCall->use_empty()) {
631 // No returns, but something is using the return value of the call. Just
633 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
636 // Since we are now done with the Call/Invoke, we can delete it.
637 TheCall->eraseFromParent();
639 // We should always be able to fold the entry block of the function into the
640 // single predecessor of the block...
641 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!");
642 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0);
644 // Splice the code entry block into calling block, right before the
645 // unconditional branch.
646 OrigBB->getInstList().splice(Br, CalleeEntry->getInstList());
647 CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes
649 // Remove the unconditional branch.
650 OrigBB->getInstList().erase(Br);
652 // Now we can remove the CalleeEntry block, which is now empty.
653 Caller->getBasicBlockList().erase(CalleeEntry);