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/Analysis/InstructionSimplify.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, InlineFunctionInfo &IFI) {
33 return InlineFunction(CallSite(CI), IFI);
35 bool llvm::InlineFunction(InvokeInst *II, InlineFunctionInfo &IFI) {
36 return InlineFunction(CallSite(II), IFI);
40 /// HandleCallsInBlockInlinedThroughInvoke - When we inline a basic block into
41 /// an invoke, we have to turn all of the calls that can throw into
42 /// invokes. This function analyze BB to see if there are any calls, and if so,
43 /// it rewrites them to be invokes that jump to InvokeDest and fills in the PHI
44 /// nodes in that block with the values specified in InvokeDestPHIValues.
46 static void HandleCallsInBlockInlinedThroughInvoke(BasicBlock *BB,
47 BasicBlock *InvokeDest,
48 const SmallVectorImpl<Value*> &InvokeDestPHIValues) {
49 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) {
50 Instruction *I = BBI++;
52 // We only need to check for function calls: inlined invoke
53 // instructions require no special handling.
54 CallInst *CI = dyn_cast<CallInst>(I);
55 if (CI == 0) continue;
57 // If this call cannot unwind, don't convert it to an invoke.
58 if (CI->doesNotThrow())
61 // Convert this function call into an invoke instruction.
62 // First, split the basic block.
63 BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc");
65 // Next, create the new invoke instruction, inserting it at the end
66 // of the old basic block.
67 ImmutableCallSite CS(CI);
68 SmallVector<Value*, 8> InvokeArgs(CS.arg_begin(), CS.arg_end());
70 InvokeInst::Create(CI->getCalledValue(), Split, InvokeDest,
71 InvokeArgs.begin(), InvokeArgs.end(),
72 CI->getName(), BB->getTerminator());
73 II->setCallingConv(CI->getCallingConv());
74 II->setAttributes(CI->getAttributes());
76 // Make sure that anything using the call now uses the invoke! This also
77 // updates the CallGraph if present, because it uses a WeakVH.
78 CI->replaceAllUsesWith(II);
80 // Delete the unconditional branch inserted by splitBasicBlock
81 BB->getInstList().pop_back();
82 Split->getInstList().pop_front(); // Delete the original call
84 // Update any PHI nodes in the exceptional block to indicate that
85 // there is now a new entry in them.
87 for (BasicBlock::iterator I = InvokeDest->begin();
88 isa<PHINode>(I); ++I, ++i)
89 cast<PHINode>(I)->addIncoming(InvokeDestPHIValues[i], BB);
91 // This basic block is now complete, the caller will continue scanning the
98 /// HandleInlinedInvoke - If we inlined an invoke site, we need to convert calls
99 /// in the body of the inlined function into invokes and turn unwind
100 /// instructions into branches to the invoke unwind dest.
102 /// II is the invoke instruction being inlined. FirstNewBlock is the first
103 /// block of the inlined code (the last block is the end of the function),
104 /// and InlineCodeInfo is information about the code that got inlined.
105 static void HandleInlinedInvoke(InvokeInst *II, BasicBlock *FirstNewBlock,
106 ClonedCodeInfo &InlinedCodeInfo) {
107 BasicBlock *InvokeDest = II->getUnwindDest();
108 SmallVector<Value*, 8> InvokeDestPHIValues;
110 // If there are PHI nodes in the unwind destination block, we need to
111 // keep track of which values came into them from this invoke, then remove
112 // the entry for this block.
113 BasicBlock *InvokeBlock = II->getParent();
114 for (BasicBlock::iterator I = InvokeDest->begin(); isa<PHINode>(I); ++I) {
115 PHINode *PN = cast<PHINode>(I);
116 // Save the value to use for this edge.
117 InvokeDestPHIValues.push_back(PN->getIncomingValueForBlock(InvokeBlock));
120 Function *Caller = FirstNewBlock->getParent();
122 // The inlined code is currently at the end of the function, scan from the
123 // start of the inlined code to its end, checking for stuff we need to
124 // rewrite. If the code doesn't have calls or unwinds, we know there is
125 // nothing to rewrite.
126 if (!InlinedCodeInfo.ContainsCalls && !InlinedCodeInfo.ContainsUnwinds) {
127 // Now that everything is happy, we have one final detail. The PHI nodes in
128 // the exception destination block still have entries due to the original
129 // invoke instruction. Eliminate these entries (which might even delete the
131 InvokeDest->removePredecessor(II->getParent());
135 for (Function::iterator BB = FirstNewBlock, E = Caller->end(); BB != E; ++BB){
136 if (InlinedCodeInfo.ContainsCalls)
137 HandleCallsInBlockInlinedThroughInvoke(BB, InvokeDest,
138 InvokeDestPHIValues);
140 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
141 // An UnwindInst requires special handling when it gets inlined into an
142 // invoke site. Once this happens, we know that the unwind would cause
143 // a control transfer to the invoke exception destination, so we can
144 // transform it into a direct branch to the exception destination.
145 BranchInst::Create(InvokeDest, UI);
147 // Delete the unwind instruction!
148 UI->eraseFromParent();
150 // Update any PHI nodes in the exceptional block to indicate that
151 // there is now a new entry in them.
153 for (BasicBlock::iterator I = InvokeDest->begin();
154 isa<PHINode>(I); ++I, ++i) {
155 PHINode *PN = cast<PHINode>(I);
156 PN->addIncoming(InvokeDestPHIValues[i], BB);
161 // Now that everything is happy, we have one final detail. The PHI nodes in
162 // the exception destination block still have entries due to the original
163 // invoke instruction. Eliminate these entries (which might even delete the
165 InvokeDest->removePredecessor(II->getParent());
168 /// UpdateCallGraphAfterInlining - Once we have cloned code over from a callee
169 /// into the caller, update the specified callgraph to reflect the changes we
170 /// made. Note that it's possible that not all code was copied over, so only
171 /// some edges of the callgraph may remain.
172 static void UpdateCallGraphAfterInlining(CallSite CS,
173 Function::iterator FirstNewBlock,
174 ValueToValueMapTy &VMap,
175 InlineFunctionInfo &IFI) {
176 CallGraph &CG = *IFI.CG;
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 ValueToValueMapTy::iterator VMI = VMap.find(OrigCall);
198 // Only copy the edge if the call was inlined!
199 if (VMI == VMap.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 Instruction *NewCall = dyn_cast<Instruction>(VMI->second);
205 if (NewCall == 0) continue;
207 // Remember that this call site got inlined for the client of
209 IFI.InlinedCalls.push_back(NewCall);
211 // It's possible that inlining the callsite will cause it to go from an
212 // indirect to a direct call by resolving a function pointer. If this
213 // happens, set the callee of the new call site to a more precise
214 // destination. This can also happen if the call graph node of the caller
215 // was just unnecessarily imprecise.
216 if (I->second->getFunction() == 0)
217 if (Function *F = CallSite(NewCall).getCalledFunction()) {
218 // Indirect call site resolved to direct call.
219 CallerNode->addCalledFunction(CallSite(NewCall), CG[F]);
224 CallerNode->addCalledFunction(CallSite(NewCall), I->second);
227 // Update the call graph by deleting the edge from Callee to Caller. We must
228 // do this after the loop above in case Caller and Callee are the same.
229 CallerNode->removeCallEdgeFor(CS);
232 // InlineFunction - This function inlines the called function into the basic
233 // block of the caller. This returns false if it is not possible to inline this
234 // call. The program is still in a well defined state if this occurs though.
236 // Note that this only does one level of inlining. For example, if the
237 // instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
238 // exists in the instruction stream. Similiarly this will inline a recursive
239 // function by one level.
241 bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI) {
242 Instruction *TheCall = CS.getInstruction();
243 LLVMContext &Context = TheCall->getContext();
244 assert(TheCall->getParent() && TheCall->getParent()->getParent() &&
245 "Instruction not in function!");
247 // If IFI has any state in it, zap it before we fill it in.
250 const Function *CalledFunc = CS.getCalledFunction();
251 if (CalledFunc == 0 || // Can't inline external function or indirect
252 CalledFunc->isDeclaration() || // call, or call to a vararg function!
253 CalledFunc->getFunctionType()->isVarArg()) return false;
256 // If the call to the callee is not a tail call, we must clear the 'tail'
257 // flags on any calls that we inline.
258 bool MustClearTailCallFlags =
259 !(isa<CallInst>(TheCall) && cast<CallInst>(TheCall)->isTailCall());
261 // If the call to the callee cannot throw, set the 'nounwind' flag on any
262 // calls that we inline.
263 bool MarkNoUnwind = CS.doesNotThrow();
265 BasicBlock *OrigBB = TheCall->getParent();
266 Function *Caller = OrigBB->getParent();
268 // GC poses two hazards to inlining, which only occur when the callee has GC:
269 // 1. If the caller has no GC, then the callee's GC must be propagated to the
271 // 2. If the caller has a differing GC, it is invalid to inline.
272 if (CalledFunc->hasGC()) {
273 if (!Caller->hasGC())
274 Caller->setGC(CalledFunc->getGC());
275 else if (CalledFunc->getGC() != Caller->getGC())
279 // Get an iterator to the last basic block in the function, which will have
280 // the new function inlined after it.
282 Function::iterator LastBlock = &Caller->back();
284 // Make sure to capture all of the return instructions from the cloned
286 SmallVector<ReturnInst*, 8> Returns;
287 ClonedCodeInfo InlinedFunctionInfo;
288 Function::iterator FirstNewBlock;
290 { // Scope to destroy VMap after cloning.
291 ValueToValueMapTy VMap;
293 assert(CalledFunc->arg_size() == CS.arg_size() &&
294 "No varargs calls can be inlined!");
296 // Calculate the vector of arguments to pass into the function cloner, which
297 // matches up the formal to the actual argument values.
298 CallSite::arg_iterator AI = CS.arg_begin();
300 for (Function::const_arg_iterator I = CalledFunc->arg_begin(),
301 E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) {
302 Value *ActualArg = *AI;
304 // When byval arguments actually inlined, we need to make the copy implied
305 // by them explicit. However, we don't do this if the callee is readonly
306 // or readnone, because the copy would be unneeded: the callee doesn't
307 // modify the struct.
308 if (CalledFunc->paramHasAttr(ArgNo+1, Attribute::ByVal) &&
309 !CalledFunc->onlyReadsMemory()) {
310 const Type *AggTy = cast<PointerType>(I->getType())->getElementType();
311 const Type *VoidPtrTy =
312 Type::getInt8PtrTy(Context);
314 // Create the alloca. If we have TargetData, use nice alignment.
316 if (IFI.TD) Align = IFI.TD->getPrefTypeAlignment(AggTy);
317 Value *NewAlloca = new AllocaInst(AggTy, 0, Align,
319 &*Caller->begin()->begin());
321 const Type *Tys[3] = {VoidPtrTy, VoidPtrTy, Type::getInt64Ty(Context)};
322 Function *MemCpyFn = Intrinsic::getDeclaration(Caller->getParent(),
325 Value *DestCast = new BitCastInst(NewAlloca, VoidPtrTy, "tmp", TheCall);
326 Value *SrcCast = new BitCastInst(*AI, VoidPtrTy, "tmp", TheCall);
330 Size = ConstantExpr::getSizeOf(AggTy);
332 Size = ConstantInt::get(Type::getInt64Ty(Context),
333 IFI.TD->getTypeStoreSize(AggTy));
335 // Always generate a memcpy of alignment 1 here because we don't know
336 // the alignment of the src pointer. Other optimizations can infer
338 Value *CallArgs[] = {
339 DestCast, SrcCast, Size,
340 ConstantInt::get(Type::getInt32Ty(Context), 1),
341 ConstantInt::getFalse(Context) // isVolatile
343 CallInst *TheMemCpy =
344 CallInst::Create(MemCpyFn, CallArgs, CallArgs+5, "", TheCall);
346 // If we have a call graph, update it.
347 if (CallGraph *CG = IFI.CG) {
348 CallGraphNode *MemCpyCGN = CG->getOrInsertFunction(MemCpyFn);
349 CallGraphNode *CallerNode = (*CG)[Caller];
350 CallerNode->addCalledFunction(TheMemCpy, MemCpyCGN);
353 // Uses of the argument in the function should use our new alloca
355 ActualArg = NewAlloca;
357 // Calls that we inline may use the new alloca, so we need to clear
358 // their 'tail' flags.
359 MustClearTailCallFlags = true;
365 // We want the inliner to prune the code as it copies. We would LOVE to
366 // have no dead or constant instructions leftover after inlining occurs
367 // (which can happen, e.g., because an argument was constant), but we'll be
368 // happy with whatever the cloner can do.
369 CloneAndPruneFunctionInto(Caller, CalledFunc, VMap,
370 /*ModuleLevelChanges=*/false, Returns, ".i",
371 &InlinedFunctionInfo, IFI.TD, TheCall);
373 // Remember the first block that is newly cloned over.
374 FirstNewBlock = LastBlock; ++FirstNewBlock;
376 // Update the callgraph if requested.
378 UpdateCallGraphAfterInlining(CS, FirstNewBlock, VMap, IFI);
381 // If there are any alloca instructions in the block that used to be the entry
382 // block for the callee, move them to the entry block of the caller. First
383 // calculate which instruction they should be inserted before. We insert the
384 // instructions at the end of the current alloca list.
387 BasicBlock::iterator InsertPoint = Caller->begin()->begin();
388 for (BasicBlock::iterator I = FirstNewBlock->begin(),
389 E = FirstNewBlock->end(); I != E; ) {
390 AllocaInst *AI = dyn_cast<AllocaInst>(I++);
391 if (AI == 0) continue;
393 // If the alloca is now dead, remove it. This often occurs due to code
395 if (AI->use_empty()) {
396 AI->eraseFromParent();
400 if (!isa<Constant>(AI->getArraySize()))
403 // Keep track of the static allocas that we inline into the caller if the
404 // StaticAllocas pointer is non-null.
405 IFI.StaticAllocas.push_back(AI);
407 // Scan for the block of allocas that we can move over, and move them
409 while (isa<AllocaInst>(I) &&
410 isa<Constant>(cast<AllocaInst>(I)->getArraySize())) {
411 IFI.StaticAllocas.push_back(cast<AllocaInst>(I));
415 // Transfer all of the allocas over in a block. Using splice means
416 // that the instructions aren't removed from the symbol table, then
418 Caller->getEntryBlock().getInstList().splice(InsertPoint,
419 FirstNewBlock->getInstList(),
424 // If the inlined code contained dynamic alloca instructions, wrap the inlined
425 // code with llvm.stacksave/llvm.stackrestore intrinsics.
426 if (InlinedFunctionInfo.ContainsDynamicAllocas) {
427 Module *M = Caller->getParent();
428 // Get the two intrinsics we care about.
429 Function *StackSave = Intrinsic::getDeclaration(M, Intrinsic::stacksave);
430 Function *StackRestore=Intrinsic::getDeclaration(M,Intrinsic::stackrestore);
432 // If we are preserving the callgraph, add edges to the stacksave/restore
433 // functions for the calls we insert.
434 CallGraphNode *StackSaveCGN = 0, *StackRestoreCGN = 0, *CallerNode = 0;
435 if (CallGraph *CG = IFI.CG) {
436 StackSaveCGN = CG->getOrInsertFunction(StackSave);
437 StackRestoreCGN = CG->getOrInsertFunction(StackRestore);
438 CallerNode = (*CG)[Caller];
441 // Insert the llvm.stacksave.
442 CallInst *SavedPtr = CallInst::Create(StackSave, "savedstack",
443 FirstNewBlock->begin());
444 if (IFI.CG) CallerNode->addCalledFunction(SavedPtr, StackSaveCGN);
446 // Insert a call to llvm.stackrestore before any return instructions in the
448 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
449 CallInst *CI = CallInst::Create(StackRestore, SavedPtr, "", Returns[i]);
450 if (IFI.CG) CallerNode->addCalledFunction(CI, StackRestoreCGN);
453 // Count the number of StackRestore calls we insert.
454 unsigned NumStackRestores = Returns.size();
456 // If we are inlining an invoke instruction, insert restores before each
457 // unwind. These unwinds will be rewritten into branches later.
458 if (InlinedFunctionInfo.ContainsUnwinds && isa<InvokeInst>(TheCall)) {
459 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
461 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
462 CallInst *CI = CallInst::Create(StackRestore, SavedPtr, "", UI);
463 if (IFI.CG) CallerNode->addCalledFunction(CI, StackRestoreCGN);
469 // If we are inlining tail call instruction through a call site that isn't
470 // marked 'tail', we must remove the tail marker for any calls in the inlined
471 // code. Also, calls inlined through a 'nounwind' call site should be marked
473 if (InlinedFunctionInfo.ContainsCalls &&
474 (MustClearTailCallFlags || MarkNoUnwind)) {
475 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
477 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
478 if (CallInst *CI = dyn_cast<CallInst>(I)) {
479 if (MustClearTailCallFlags)
480 CI->setTailCall(false);
482 CI->setDoesNotThrow();
486 // If we are inlining through a 'nounwind' call site then any inlined 'unwind'
487 // instructions are unreachable.
488 if (InlinedFunctionInfo.ContainsUnwinds && MarkNoUnwind)
489 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
491 TerminatorInst *Term = BB->getTerminator();
492 if (isa<UnwindInst>(Term)) {
493 new UnreachableInst(Context, Term);
494 BB->getInstList().erase(Term);
498 // If we are inlining for an invoke instruction, we must make sure to rewrite
499 // any inlined 'unwind' instructions into branches to the invoke exception
500 // destination, and call instructions into invoke instructions.
501 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
502 HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo);
504 // If we cloned in _exactly one_ basic block, and if that block ends in a
505 // return instruction, we splice the body of the inlined callee directly into
506 // the calling basic block.
507 if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) {
508 // Move all of the instructions right before the call.
509 OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(),
510 FirstNewBlock->begin(), FirstNewBlock->end());
511 // Remove the cloned basic block.
512 Caller->getBasicBlockList().pop_back();
514 // If the call site was an invoke instruction, add a branch to the normal
516 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
517 BranchInst::Create(II->getNormalDest(), TheCall);
519 // If the return instruction returned a value, replace uses of the call with
520 // uses of the returned value.
521 if (!TheCall->use_empty()) {
522 ReturnInst *R = Returns[0];
523 if (TheCall == R->getReturnValue())
524 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
526 TheCall->replaceAllUsesWith(R->getReturnValue());
528 // Since we are now done with the Call/Invoke, we can delete it.
529 TheCall->eraseFromParent();
531 // Since we are now done with the return instruction, delete it also.
532 Returns[0]->eraseFromParent();
534 // We are now done with the inlining.
538 // Otherwise, we have the normal case, of more than one block to inline or
539 // multiple return sites.
541 // We want to clone the entire callee function into the hole between the
542 // "starter" and "ender" blocks. How we accomplish this depends on whether
543 // this is an invoke instruction or a call instruction.
544 BasicBlock *AfterCallBB;
545 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
547 // Add an unconditional branch to make this look like the CallInst case...
548 BranchInst *NewBr = BranchInst::Create(II->getNormalDest(), TheCall);
550 // Split the basic block. This guarantees that no PHI nodes will have to be
551 // updated due to new incoming edges, and make the invoke case more
552 // symmetric to the call case.
553 AfterCallBB = OrigBB->splitBasicBlock(NewBr,
554 CalledFunc->getName()+".exit");
556 } else { // It's a call
557 // If this is a call instruction, we need to split the basic block that
558 // the call lives in.
560 AfterCallBB = OrigBB->splitBasicBlock(TheCall,
561 CalledFunc->getName()+".exit");
564 // Change the branch that used to go to AfterCallBB to branch to the first
565 // basic block of the inlined function.
567 TerminatorInst *Br = OrigBB->getTerminator();
568 assert(Br && Br->getOpcode() == Instruction::Br &&
569 "splitBasicBlock broken!");
570 Br->setOperand(0, FirstNewBlock);
573 // Now that the function is correct, make it a little bit nicer. In
574 // particular, move the basic blocks inserted from the end of the function
575 // into the space made by splitting the source basic block.
576 Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(),
577 FirstNewBlock, Caller->end());
579 // Handle all of the return instructions that we just cloned in, and eliminate
580 // any users of the original call/invoke instruction.
581 const Type *RTy = CalledFunc->getReturnType();
584 if (Returns.size() > 1) {
585 // The PHI node should go at the front of the new basic block to merge all
586 // possible incoming values.
587 if (!TheCall->use_empty()) {
588 PHI = PHINode::Create(RTy, TheCall->getName(),
589 AfterCallBB->begin());
590 // Anything that used the result of the function call should now use the
591 // PHI node as their operand.
592 TheCall->replaceAllUsesWith(PHI);
595 // Loop over all of the return instructions adding entries to the PHI node
598 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
599 ReturnInst *RI = Returns[i];
600 assert(RI->getReturnValue()->getType() == PHI->getType() &&
601 "Ret value not consistent in function!");
602 PHI->addIncoming(RI->getReturnValue(), RI->getParent());
607 // Add a branch to the merge points and remove return instructions.
608 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
609 ReturnInst *RI = Returns[i];
610 BranchInst::Create(AfterCallBB, RI);
611 RI->eraseFromParent();
613 } else if (!Returns.empty()) {
614 // Otherwise, if there is exactly one return value, just replace anything
615 // using the return value of the call with the computed value.
616 if (!TheCall->use_empty()) {
617 if (TheCall == Returns[0]->getReturnValue())
618 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
620 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue());
623 // Splice the code from the return block into the block that it will return
624 // to, which contains the code that was after the call.
625 BasicBlock *ReturnBB = Returns[0]->getParent();
626 AfterCallBB->getInstList().splice(AfterCallBB->begin(),
627 ReturnBB->getInstList());
629 // Update PHI nodes that use the ReturnBB to use the AfterCallBB.
630 ReturnBB->replaceAllUsesWith(AfterCallBB);
632 // Delete the return instruction now and empty ReturnBB now.
633 Returns[0]->eraseFromParent();
634 ReturnBB->eraseFromParent();
635 } else if (!TheCall->use_empty()) {
636 // No returns, but something is using the return value of the call. Just
638 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
641 // Since we are now done with the Call/Invoke, we can delete it.
642 TheCall->eraseFromParent();
644 // We should always be able to fold the entry block of the function into the
645 // single predecessor of the block...
646 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!");
647 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0);
649 // Splice the code entry block into calling block, right before the
650 // unconditional branch.
651 OrigBB->getInstList().splice(Br, CalleeEntry->getInstList());
652 CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes
654 // Remove the unconditional branch.
655 OrigBB->getInstList().erase(Br);
657 // Now we can remove the CalleeEntry block, which is now empty.
658 Caller->getBasicBlockList().erase(CalleeEntry);
660 // If we inserted a phi node, check to see if it has a single value (e.g. all
661 // the entries are the same or undef). If so, remove the PHI so it doesn't
662 // block other optimizations.
664 if (Value *V = SimplifyInstruction(PHI, IFI.TD)) {
665 PHI->replaceAllUsesWith(V);
666 PHI->eraseFromParent();