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 ImmutableCallSite CS(CI);
67 SmallVector<Value*, 8> InvokeArgs(CS.arg_begin(), CS.arg_end());
69 InvokeInst::Create(CI->getCalledValue(), Split, InvokeDest,
70 InvokeArgs.begin(), InvokeArgs.end(),
71 CI->getName(), BB->getTerminator());
72 II->setCallingConv(CI->getCallingConv());
73 II->setAttributes(CI->getAttributes());
75 // Make sure that anything using the call now uses the invoke! This also
76 // updates the CallGraph if present, because it uses a WeakVH.
77 CI->replaceAllUsesWith(II);
79 // Delete the unconditional branch inserted by splitBasicBlock
80 BB->getInstList().pop_back();
81 Split->getInstList().pop_front(); // Delete the original call
83 // Update any PHI nodes in the exceptional block to indicate that
84 // there is now a new entry in them.
86 for (BasicBlock::iterator I = InvokeDest->begin();
87 isa<PHINode>(I); ++I, ++i)
88 cast<PHINode>(I)->addIncoming(InvokeDestPHIValues[i], BB);
90 // This basic block is now complete, the caller will continue scanning the
97 /// HandleInlinedInvoke - If we inlined an invoke site, we need to convert calls
98 /// in the body of the inlined function into invokes and turn unwind
99 /// instructions into branches to the invoke unwind dest.
101 /// II is the invoke instruction being inlined. FirstNewBlock is the first
102 /// block of the inlined code (the last block is the end of the function),
103 /// and InlineCodeInfo is information about the code that got inlined.
104 static void HandleInlinedInvoke(InvokeInst *II, BasicBlock *FirstNewBlock,
105 ClonedCodeInfo &InlinedCodeInfo) {
106 BasicBlock *InvokeDest = II->getUnwindDest();
107 SmallVector<Value*, 8> InvokeDestPHIValues;
109 // If there are PHI nodes in the unwind destination block, we need to
110 // keep track of which values came into them from this invoke, then remove
111 // the entry for this block.
112 BasicBlock *InvokeBlock = II->getParent();
113 for (BasicBlock::iterator I = InvokeDest->begin(); isa<PHINode>(I); ++I) {
114 PHINode *PN = cast<PHINode>(I);
115 // Save the value to use for this edge.
116 InvokeDestPHIValues.push_back(PN->getIncomingValueForBlock(InvokeBlock));
119 Function *Caller = FirstNewBlock->getParent();
121 // The inlined code is currently at the end of the function, scan from the
122 // start of the inlined code to its end, checking for stuff we need to
123 // rewrite. If the code doesn't have calls or unwinds, we know there is
124 // nothing to rewrite.
125 if (!InlinedCodeInfo.ContainsCalls && !InlinedCodeInfo.ContainsUnwinds) {
126 // Now that everything is happy, we have one final detail. The PHI nodes in
127 // the exception destination block still have entries due to the original
128 // invoke instruction. Eliminate these entries (which might even delete the
130 InvokeDest->removePredecessor(II->getParent());
134 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); BB != E; ++BB){
135 if (InlinedCodeInfo.ContainsCalls)
136 HandleCallsInBlockInlinedThroughInvoke(BB, InvokeDest,
137 InvokeDestPHIValues);
139 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
140 // An UnwindInst requires special handling when it gets inlined into an
141 // invoke site. Once this happens, we know that the unwind would cause
142 // a control transfer to the invoke exception destination, so we can
143 // transform it into a direct branch to the exception destination.
144 BranchInst::Create(InvokeDest, UI);
146 // Delete the unwind instruction!
147 UI->eraseFromParent();
149 // Update any PHI nodes in the exceptional block to indicate that
150 // there is now a new entry in them.
152 for (BasicBlock::iterator I = InvokeDest->begin();
153 isa<PHINode>(I); ++I, ++i) {
154 PHINode *PN = cast<PHINode>(I);
155 PN->addIncoming(InvokeDestPHIValues[i], BB);
160 // Now that everything is happy, we have one final detail. The PHI nodes in
161 // the exception destination block still have entries due to the original
162 // invoke instruction. Eliminate these entries (which might even delete the
164 InvokeDest->removePredecessor(II->getParent());
167 /// UpdateCallGraphAfterInlining - Once we have cloned code over from a callee
168 /// into the caller, update the specified callgraph to reflect the changes we
169 /// made. Note that it's possible that not all code was copied over, so only
170 /// some edges of the callgraph may remain.
171 static void UpdateCallGraphAfterInlining(CallSite CS,
172 Function::iterator FirstNewBlock,
173 ValueMap<const Value*, Value*> &VMap,
174 InlineFunctionInfo &IFI) {
175 CallGraph &CG = *IFI.CG;
176 const Function *Caller = CS.getInstruction()->getParent()->getParent();
177 const Function *Callee = CS.getCalledFunction();
178 CallGraphNode *CalleeNode = CG[Callee];
179 CallGraphNode *CallerNode = CG[Caller];
181 // Since we inlined some uninlined call sites in the callee into the caller,
182 // add edges from the caller to all of the callees of the callee.
183 CallGraphNode::iterator I = CalleeNode->begin(), E = CalleeNode->end();
185 // Consider the case where CalleeNode == CallerNode.
186 CallGraphNode::CalledFunctionsVector CallCache;
187 if (CalleeNode == CallerNode) {
188 CallCache.assign(I, E);
189 I = CallCache.begin();
193 for (; I != E; ++I) {
194 const Value *OrigCall = I->first;
196 ValueMap<const Value*, Value*>::iterator VMI = VMap.find(OrigCall);
197 // Only copy the edge if the call was inlined!
198 if (VMI == VMap.end() || VMI->second == 0)
201 // If the call was inlined, but then constant folded, there is no edge to
202 // add. Check for this case.
203 Instruction *NewCall = dyn_cast<Instruction>(VMI->second);
204 if (NewCall == 0) continue;
206 // Remember that this call site got inlined for the client of
208 IFI.InlinedCalls.push_back(NewCall);
210 // It's possible that inlining the callsite will cause it to go from an
211 // indirect to a direct call by resolving a function pointer. If this
212 // happens, set the callee of the new call site to a more precise
213 // destination. This can also happen if the call graph node of the caller
214 // was just unnecessarily imprecise.
215 if (I->second->getFunction() == 0)
216 if (Function *F = CallSite(NewCall).getCalledFunction()) {
217 // Indirect call site resolved to direct call.
218 CallerNode->addCalledFunction(CallSite(NewCall), CG[F]);
223 CallerNode->addCalledFunction(CallSite(NewCall), I->second);
226 // Update the call graph by deleting the edge from Callee to Caller. We must
227 // do this after the loop above in case Caller and Callee are the same.
228 CallerNode->removeCallEdgeFor(CS);
231 // InlineFunction - This function inlines the called function into the basic
232 // block of the caller. This returns false if it is not possible to inline this
233 // call. The program is still in a well defined state if this occurs though.
235 // Note that this only does one level of inlining. For example, if the
236 // instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
237 // exists in the instruction stream. Similiarly this will inline a recursive
238 // function by one level.
240 bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI) {
241 Instruction *TheCall = CS.getInstruction();
242 LLVMContext &Context = TheCall->getContext();
243 assert(TheCall->getParent() && TheCall->getParent()->getParent() &&
244 "Instruction not in function!");
246 // If IFI has any state in it, zap it before we fill it in.
249 const Function *CalledFunc = CS.getCalledFunction();
250 if (CalledFunc == 0 || // Can't inline external function or indirect
251 CalledFunc->isDeclaration() || // call, or call to a vararg function!
252 CalledFunc->getFunctionType()->isVarArg()) return false;
255 // If the call to the callee is not a tail call, we must clear the 'tail'
256 // flags on any calls that we inline.
257 bool MustClearTailCallFlags =
258 !(isa<CallInst>(TheCall) && cast<CallInst>(TheCall)->isTailCall());
260 // If the call to the callee cannot throw, set the 'nounwind' flag on any
261 // calls that we inline.
262 bool MarkNoUnwind = CS.doesNotThrow();
264 BasicBlock *OrigBB = TheCall->getParent();
265 Function *Caller = OrigBB->getParent();
267 // GC poses two hazards to inlining, which only occur when the callee has GC:
268 // 1. If the caller has no GC, then the callee's GC must be propagated to the
270 // 2. If the caller has a differing GC, it is invalid to inline.
271 if (CalledFunc->hasGC()) {
272 if (!Caller->hasGC())
273 Caller->setGC(CalledFunc->getGC());
274 else if (CalledFunc->getGC() != Caller->getGC())
278 // Get an iterator to the last basic block in the function, which will have
279 // the new function inlined after it.
281 Function::iterator LastBlock = &Caller->back();
283 // Make sure to capture all of the return instructions from the cloned
285 SmallVector<ReturnInst*, 8> Returns;
286 ClonedCodeInfo InlinedFunctionInfo;
287 Function::iterator FirstNewBlock;
289 { // Scope to destroy VMap after cloning.
290 ValueMap<const Value*, Value*> VMap;
292 assert(CalledFunc->arg_size() == CS.arg_size() &&
293 "No varargs calls can be inlined!");
295 // Calculate the vector of arguments to pass into the function cloner, which
296 // matches up the formal to the actual argument values.
297 CallSite::arg_iterator AI = CS.arg_begin();
299 for (Function::const_arg_iterator I = CalledFunc->arg_begin(),
300 E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) {
301 Value *ActualArg = *AI;
303 // When byval arguments actually inlined, we need to make the copy implied
304 // by them explicit. However, we don't do this if the callee is readonly
305 // or readnone, because the copy would be unneeded: the callee doesn't
306 // modify the struct.
307 if (CalledFunc->paramHasAttr(ArgNo+1, Attribute::ByVal) &&
308 !CalledFunc->onlyReadsMemory()) {
309 const Type *AggTy = cast<PointerType>(I->getType())->getElementType();
310 const Type *VoidPtrTy =
311 Type::getInt8PtrTy(Context);
313 // Create the alloca. If we have TargetData, use nice alignment.
315 if (IFI.TD) Align = IFI.TD->getPrefTypeAlignment(AggTy);
316 Value *NewAlloca = new AllocaInst(AggTy, 0, Align,
318 &*Caller->begin()->begin());
320 const Type *Tys[3] = {VoidPtrTy, VoidPtrTy, Type::getInt64Ty(Context)};
321 Function *MemCpyFn = Intrinsic::getDeclaration(Caller->getParent(),
324 Value *DestCast = new BitCastInst(NewAlloca, VoidPtrTy, "tmp", TheCall);
325 Value *SrcCast = new BitCastInst(*AI, VoidPtrTy, "tmp", TheCall);
329 Size = ConstantExpr::getSizeOf(AggTy);
331 Size = ConstantInt::get(Type::getInt64Ty(Context),
332 IFI.TD->getTypeStoreSize(AggTy));
334 // Always generate a memcpy of alignment 1 here because we don't know
335 // the alignment of the src pointer. Other optimizations can infer
337 Value *CallArgs[] = {
338 DestCast, SrcCast, Size,
339 ConstantInt::get(Type::getInt32Ty(Context), 1),
340 ConstantInt::get(Type::getInt1Ty(Context), 0)
342 CallInst *TheMemCpy =
343 CallInst::Create(MemCpyFn, CallArgs, CallArgs+5, "", TheCall);
345 // If we have a call graph, update it.
346 if (CallGraph *CG = IFI.CG) {
347 CallGraphNode *MemCpyCGN = CG->getOrInsertFunction(MemCpyFn);
348 CallGraphNode *CallerNode = (*CG)[Caller];
349 CallerNode->addCalledFunction(TheMemCpy, MemCpyCGN);
352 // Uses of the argument in the function should use our new alloca
354 ActualArg = NewAlloca;
356 // Calls that we inline may use the new alloca, so we need to clear
357 // their 'tail' flags.
358 MustClearTailCallFlags = true;
364 // We want the inliner to prune the code as it copies. We would LOVE to
365 // have no dead or constant instructions leftover after inlining occurs
366 // (which can happen, e.g., because an argument was constant), but we'll be
367 // happy with whatever the cloner can do.
368 CloneAndPruneFunctionInto(Caller, CalledFunc, VMap, Returns, ".i",
369 &InlinedFunctionInfo, IFI.TD, TheCall);
371 // Remember the first block that is newly cloned over.
372 FirstNewBlock = LastBlock; ++FirstNewBlock;
374 // Update the callgraph if requested.
376 UpdateCallGraphAfterInlining(CS, FirstNewBlock, VMap, IFI);
379 // If there are any alloca instructions in the block that used to be the entry
380 // block for the callee, move them to the entry block of the caller. First
381 // calculate which instruction they should be inserted before. We insert the
382 // instructions at the end of the current alloca list.
385 BasicBlock::iterator InsertPoint = Caller->begin()->begin();
386 for (BasicBlock::iterator I = FirstNewBlock->begin(),
387 E = FirstNewBlock->end(); I != E; ) {
388 AllocaInst *AI = dyn_cast<AllocaInst>(I++);
389 if (AI == 0) continue;
391 // If the alloca is now dead, remove it. This often occurs due to code
393 if (AI->use_empty()) {
394 AI->eraseFromParent();
398 if (!isa<Constant>(AI->getArraySize()))
401 // Keep track of the static allocas that we inline into the caller if the
402 // StaticAllocas pointer is non-null.
403 IFI.StaticAllocas.push_back(AI);
405 // Scan for the block of allocas that we can move over, and move them
407 while (isa<AllocaInst>(I) &&
408 isa<Constant>(cast<AllocaInst>(I)->getArraySize())) {
409 IFI.StaticAllocas.push_back(cast<AllocaInst>(I));
413 // Transfer all of the allocas over in a block. Using splice means
414 // that the instructions aren't removed from the symbol table, then
416 Caller->getEntryBlock().getInstList().splice(InsertPoint,
417 FirstNewBlock->getInstList(),
422 // If the inlined code contained dynamic alloca instructions, wrap the inlined
423 // code with llvm.stacksave/llvm.stackrestore intrinsics.
424 if (InlinedFunctionInfo.ContainsDynamicAllocas) {
425 Module *M = Caller->getParent();
426 // Get the two intrinsics we care about.
427 Function *StackSave = Intrinsic::getDeclaration(M, Intrinsic::stacksave);
428 Function *StackRestore=Intrinsic::getDeclaration(M,Intrinsic::stackrestore);
430 // If we are preserving the callgraph, add edges to the stacksave/restore
431 // functions for the calls we insert.
432 CallGraphNode *StackSaveCGN = 0, *StackRestoreCGN = 0, *CallerNode = 0;
433 if (CallGraph *CG = IFI.CG) {
434 StackSaveCGN = CG->getOrInsertFunction(StackSave);
435 StackRestoreCGN = CG->getOrInsertFunction(StackRestore);
436 CallerNode = (*CG)[Caller];
439 // Insert the llvm.stacksave.
440 CallInst *SavedPtr = CallInst::Create(StackSave, "savedstack",
441 FirstNewBlock->begin());
442 if (IFI.CG) CallerNode->addCalledFunction(SavedPtr, StackSaveCGN);
444 // Insert a call to llvm.stackrestore before any return instructions in the
446 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
447 CallInst *CI = CallInst::Create(StackRestore, SavedPtr, "", Returns[i]);
448 if (IFI.CG) CallerNode->addCalledFunction(CI, StackRestoreCGN);
451 // Count the number of StackRestore calls we insert.
452 unsigned NumStackRestores = Returns.size();
454 // If we are inlining an invoke instruction, insert restores before each
455 // unwind. These unwinds will be rewritten into branches later.
456 if (InlinedFunctionInfo.ContainsUnwinds && isa<InvokeInst>(TheCall)) {
457 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
459 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
460 CallInst *CI = CallInst::Create(StackRestore, SavedPtr, "", UI);
461 if (IFI.CG) CallerNode->addCalledFunction(CI, StackRestoreCGN);
467 // If we are inlining tail call instruction through a call site that isn't
468 // marked 'tail', we must remove the tail marker for any calls in the inlined
469 // code. Also, calls inlined through a 'nounwind' call site should be marked
471 if (InlinedFunctionInfo.ContainsCalls &&
472 (MustClearTailCallFlags || MarkNoUnwind)) {
473 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
475 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
476 if (CallInst *CI = dyn_cast<CallInst>(I)) {
477 if (MustClearTailCallFlags)
478 CI->setTailCall(false);
480 CI->setDoesNotThrow();
484 // If we are inlining through a 'nounwind' call site then any inlined 'unwind'
485 // instructions are unreachable.
486 if (InlinedFunctionInfo.ContainsUnwinds && MarkNoUnwind)
487 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
489 TerminatorInst *Term = BB->getTerminator();
490 if (isa<UnwindInst>(Term)) {
491 new UnreachableInst(Context, Term);
492 BB->getInstList().erase(Term);
496 // If we are inlining for an invoke instruction, we must make sure to rewrite
497 // any inlined 'unwind' instructions into branches to the invoke exception
498 // destination, and call instructions into invoke instructions.
499 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
500 HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo);
502 // If we cloned in _exactly one_ basic block, and if that block ends in a
503 // return instruction, we splice the body of the inlined callee directly into
504 // the calling basic block.
505 if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) {
506 // Move all of the instructions right before the call.
507 OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(),
508 FirstNewBlock->begin(), FirstNewBlock->end());
509 // Remove the cloned basic block.
510 Caller->getBasicBlockList().pop_back();
512 // If the call site was an invoke instruction, add a branch to the normal
514 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
515 BranchInst::Create(II->getNormalDest(), TheCall);
517 // If the return instruction returned a value, replace uses of the call with
518 // uses of the returned value.
519 if (!TheCall->use_empty()) {
520 ReturnInst *R = Returns[0];
521 if (TheCall == R->getReturnValue())
522 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
524 TheCall->replaceAllUsesWith(R->getReturnValue());
526 // Since we are now done with the Call/Invoke, we can delete it.
527 TheCall->eraseFromParent();
529 // Since we are now done with the return instruction, delete it also.
530 Returns[0]->eraseFromParent();
532 // We are now done with the inlining.
536 // Otherwise, we have the normal case, of more than one block to inline or
537 // multiple return sites.
539 // We want to clone the entire callee function into the hole between the
540 // "starter" and "ender" blocks. How we accomplish this depends on whether
541 // this is an invoke instruction or a call instruction.
542 BasicBlock *AfterCallBB;
543 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
545 // Add an unconditional branch to make this look like the CallInst case...
546 BranchInst *NewBr = BranchInst::Create(II->getNormalDest(), TheCall);
548 // Split the basic block. This guarantees that no PHI nodes will have to be
549 // updated due to new incoming edges, and make the invoke case more
550 // symmetric to the call case.
551 AfterCallBB = OrigBB->splitBasicBlock(NewBr,
552 CalledFunc->getName()+".exit");
554 } else { // It's a call
555 // If this is a call instruction, we need to split the basic block that
556 // the call lives in.
558 AfterCallBB = OrigBB->splitBasicBlock(TheCall,
559 CalledFunc->getName()+".exit");
562 // Change the branch that used to go to AfterCallBB to branch to the first
563 // basic block of the inlined function.
565 TerminatorInst *Br = OrigBB->getTerminator();
566 assert(Br && Br->getOpcode() == Instruction::Br &&
567 "splitBasicBlock broken!");
568 Br->setOperand(0, FirstNewBlock);
571 // Now that the function is correct, make it a little bit nicer. In
572 // particular, move the basic blocks inserted from the end of the function
573 // into the space made by splitting the source basic block.
574 Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(),
575 FirstNewBlock, Caller->end());
577 // Handle all of the return instructions that we just cloned in, and eliminate
578 // any users of the original call/invoke instruction.
579 const Type *RTy = CalledFunc->getReturnType();
581 if (Returns.size() > 1) {
582 // The PHI node should go at the front of the new basic block to merge all
583 // possible incoming values.
585 if (!TheCall->use_empty()) {
586 PHI = PHINode::Create(RTy, TheCall->getName(),
587 AfterCallBB->begin());
588 // Anything that used the result of the function call should now use the
589 // PHI node as their operand.
590 TheCall->replaceAllUsesWith(PHI);
593 // Loop over all of the return instructions adding entries to the PHI node
596 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
597 ReturnInst *RI = Returns[i];
598 assert(RI->getReturnValue()->getType() == PHI->getType() &&
599 "Ret value not consistent in function!");
600 PHI->addIncoming(RI->getReturnValue(), RI->getParent());
603 // Now that we inserted the PHI, check to see if it has a single value
604 // (e.g. all the entries are the same or undef). If so, remove the PHI so
605 // it doesn't block other optimizations.
606 if (Value *V = PHI->hasConstantValue()) {
607 PHI->replaceAllUsesWith(V);
608 PHI->eraseFromParent();
613 // Add a branch to the merge points and remove return instructions.
614 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
615 ReturnInst *RI = Returns[i];
616 BranchInst::Create(AfterCallBB, RI);
617 RI->eraseFromParent();
619 } else if (!Returns.empty()) {
620 // Otherwise, if there is exactly one return value, just replace anything
621 // using the return value of the call with the computed value.
622 if (!TheCall->use_empty()) {
623 if (TheCall == Returns[0]->getReturnValue())
624 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
626 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue());
629 // Splice the code from the return block into the block that it will return
630 // to, which contains the code that was after the call.
631 BasicBlock *ReturnBB = Returns[0]->getParent();
632 AfterCallBB->getInstList().splice(AfterCallBB->begin(),
633 ReturnBB->getInstList());
635 // Update PHI nodes that use the ReturnBB to use the AfterCallBB.
636 ReturnBB->replaceAllUsesWith(AfterCallBB);
638 // Delete the return instruction now and empty ReturnBB now.
639 Returns[0]->eraseFromParent();
640 ReturnBB->eraseFromParent();
641 } else if (!TheCall->use_empty()) {
642 // No returns, but something is using the return value of the call. Just
644 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
647 // Since we are now done with the Call/Invoke, we can delete it.
648 TheCall->eraseFromParent();
650 // We should always be able to fold the entry block of the function into the
651 // single predecessor of the block...
652 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!");
653 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0);
655 // Splice the code entry block into calling block, right before the
656 // unconditional branch.
657 OrigBB->getInstList().splice(Br, CalleeEntry->getInstList());
658 CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes
660 // Remove the unconditional branch.
661 OrigBB->getInstList().erase(Br);
663 // Now we can remove the CalleeEntry block, which is now empty.
664 Caller->getBasicBlockList().erase(CalleeEntry);