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 return InlineFunction(CallSite(CI), CG, TD);
35 bool llvm::InlineFunction(InvokeInst *II, CallGraph *CG, const TargetData *TD) {
36 return InlineFunction(CallSite(II), CG, TD);
39 /// HandleInlinedInvoke - If we inlined an invoke site, we need to convert calls
40 /// in the body of the inlined function into invokes and turn unwind
41 /// instructions into branches to the invoke unwind dest.
43 /// II is the invoke instruction being inlined. FirstNewBlock is the first
44 /// block of the inlined code (the last block is the end of the function),
45 /// and InlineCodeInfo is information about the code that got inlined.
46 static void HandleInlinedInvoke(InvokeInst *II, BasicBlock *FirstNewBlock,
47 ClonedCodeInfo &InlinedCodeInfo,
49 BasicBlock *InvokeDest = II->getUnwindDest();
50 std::vector<Value*> InvokeDestPHIValues;
52 // If there are PHI nodes in the unwind destination block, we need to
53 // keep track of which values came into them from this invoke, then remove
54 // the entry for this block.
55 BasicBlock *InvokeBlock = II->getParent();
56 for (BasicBlock::iterator I = InvokeDest->begin(); isa<PHINode>(I); ++I) {
57 PHINode *PN = cast<PHINode>(I);
58 // Save the value to use for this edge.
59 InvokeDestPHIValues.push_back(PN->getIncomingValueForBlock(InvokeBlock));
62 Function *Caller = FirstNewBlock->getParent();
64 // The inlined code is currently at the end of the function, scan from the
65 // start of the inlined code to its end, checking for stuff we need to
67 if (InlinedCodeInfo.ContainsCalls || InlinedCodeInfo.ContainsUnwinds) {
68 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
70 if (InlinedCodeInfo.ContainsCalls) {
71 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ){
72 Instruction *I = BBI++;
74 // We only need to check for function calls: inlined invoke
75 // instructions require no special handling.
76 if (!isa<CallInst>(I)) continue;
77 CallInst *CI = cast<CallInst>(I);
79 // If this call cannot unwind, don't convert it to an invoke.
80 if (CI->doesNotThrow())
83 // Convert this function call into an invoke instruction.
84 // First, split the basic block.
85 BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc");
87 // Next, create the new invoke instruction, inserting it at the end
88 // of the old basic block.
89 SmallVector<Value*, 8> InvokeArgs(CI->op_begin()+1, CI->op_end());
91 InvokeInst::Create(CI->getCalledValue(), Split, InvokeDest,
92 InvokeArgs.begin(), InvokeArgs.end(),
93 CI->getName(), BB->getTerminator());
94 II->setCallingConv(CI->getCallingConv());
95 II->setAttributes(CI->getAttributes());
97 // Make sure that anything using the call now uses the invoke!
98 CI->replaceAllUsesWith(II);
100 // Update the callgraph.
102 // We should be able to do this:
103 // (*CG)[Caller]->replaceCallSite(CI, II);
104 // but that fails if the old call site isn't in the call graph,
105 // which, because of LLVM bug 3601, it sometimes isn't.
106 CallGraphNode *CGN = (*CG)[Caller];
107 for (CallGraphNode::iterator NI = CGN->begin(), NE = CGN->end();
109 if (NI->first == CI) {
116 // Delete the unconditional branch inserted by splitBasicBlock
117 BB->getInstList().pop_back();
118 Split->getInstList().pop_front(); // Delete the original call
120 // Update any PHI nodes in the exceptional block to indicate that
121 // there is now a new entry in them.
123 for (BasicBlock::iterator I = InvokeDest->begin();
124 isa<PHINode>(I); ++I, ++i) {
125 PHINode *PN = cast<PHINode>(I);
126 PN->addIncoming(InvokeDestPHIValues[i], BB);
129 // This basic block is now complete, start scanning the next one.
134 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
135 // An UnwindInst requires special handling when it gets inlined into an
136 // invoke site. Once this happens, we know that the unwind would cause
137 // a control transfer to the invoke exception destination, so we can
138 // transform it into a direct branch to the exception destination.
139 BranchInst::Create(InvokeDest, UI);
141 // Delete the unwind instruction!
142 UI->eraseFromParent();
144 // Update any PHI nodes in the exceptional block to indicate that
145 // there is now a new entry in them.
147 for (BasicBlock::iterator I = InvokeDest->begin();
148 isa<PHINode>(I); ++I, ++i) {
149 PHINode *PN = cast<PHINode>(I);
150 PN->addIncoming(InvokeDestPHIValues[i], BB);
156 // Now that everything is happy, we have one final detail. The PHI nodes in
157 // the exception destination block still have entries due to the original
158 // invoke instruction. Eliminate these entries (which might even delete the
160 InvokeDest->removePredecessor(II->getParent());
163 /// UpdateCallGraphAfterInlining - Once we have cloned code over from a callee
164 /// into the caller, update the specified callgraph to reflect the changes we
165 /// made. Note that it's possible that not all code was copied over, so only
166 /// some edges of the callgraph may remain.
167 static void UpdateCallGraphAfterInlining(CallSite CS,
168 Function::iterator FirstNewBlock,
169 DenseMap<const Value*, Value*> &ValueMap,
171 const Function *Caller = CS.getInstruction()->getParent()->getParent();
172 const Function *Callee = CS.getCalledFunction();
173 CallGraphNode *CalleeNode = CG[Callee];
174 CallGraphNode *CallerNode = CG[Caller];
176 // Since we inlined some uninlined call sites in the callee into the caller,
177 // add edges from the caller to all of the callees of the callee.
178 CallGraphNode::iterator I = CalleeNode->begin(), E = CalleeNode->end();
180 // Consider the case where CalleeNode == CallerNode.
181 CallGraphNode::CalledFunctionsVector CallCache;
182 if (CalleeNode == CallerNode) {
183 CallCache.assign(I, E);
184 I = CallCache.begin();
188 for (; I != E; ++I) {
189 const Instruction *OrigCall = I->first.getInstruction();
191 DenseMap<const Value*, Value*>::iterator VMI = ValueMap.find(OrigCall);
192 // Only copy the edge if the call was inlined!
193 if (VMI != ValueMap.end() && VMI->second) {
194 // If the call was inlined, but then constant folded, there is no edge to
195 // add. Check for this case.
196 if (Instruction *NewCall = dyn_cast<Instruction>(VMI->second))
197 CallerNode->addCalledFunction(CallSite::get(NewCall), I->second);
200 // Update the call graph by deleting the edge from Callee to Caller. We must
201 // do this after the loop above in case Caller and Callee are the same.
202 CallerNode->removeCallEdgeFor(CS);
205 /// findFnRegionEndMarker - This is a utility routine that is used by
206 /// InlineFunction. Return llvm.dbg.region.end intrinsic that corresponds
207 /// to the llvm.dbg.func.start of the function F. Otherwise return NULL.
208 static const DbgRegionEndInst *findFnRegionEndMarker(const Function *F) {
210 GlobalVariable *FnStart = NULL;
211 const DbgRegionEndInst *FnEnd = NULL;
212 for (Function::const_iterator FI = F->begin(), FE =F->end(); FI != FE; ++FI)
213 for (BasicBlock::const_iterator BI = FI->begin(), BE = FI->end(); BI != BE;
215 if (FnStart == NULL) {
216 if (const DbgFuncStartInst *FSI = dyn_cast<DbgFuncStartInst>(BI)) {
217 DISubprogram SP(cast<GlobalVariable>(FSI->getSubprogram()));
218 assert (SP.isNull() == false && "Invalid llvm.dbg.func.start");
220 FnStart = SP.getGV();
223 if (const DbgRegionEndInst *REI = dyn_cast<DbgRegionEndInst>(BI))
224 if (REI->getContext() == FnStart)
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, CallGraph *CG, const TargetData *TD) {
241 Instruction *TheCall = CS.getInstruction();
242 LLVMContext &Context = TheCall->getContext();
243 assert(TheCall->getParent() && TheCall->getParent()->getParent() &&
244 "Instruction not in function!");
246 const Function *CalledFunc = CS.getCalledFunction();
247 if (CalledFunc == 0 || // Can't inline external function or indirect
248 CalledFunc->isDeclaration() || // call, or call to a vararg function!
249 CalledFunc->getFunctionType()->isVarArg()) return false;
252 // If the call to the callee is not a tail call, we must clear the 'tail'
253 // flags on any calls that we inline.
254 bool MustClearTailCallFlags =
255 !(isa<CallInst>(TheCall) && cast<CallInst>(TheCall)->isTailCall());
257 // If the call to the callee cannot throw, set the 'nounwind' flag on any
258 // calls that we inline.
259 bool MarkNoUnwind = CS.doesNotThrow();
261 BasicBlock *OrigBB = TheCall->getParent();
262 Function *Caller = OrigBB->getParent();
264 // GC poses two hazards to inlining, which only occur when the callee has GC:
265 // 1. If the caller has no GC, then the callee's GC must be propagated to the
267 // 2. If the caller has a differing GC, it is invalid to inline.
268 if (CalledFunc->hasGC()) {
269 if (!Caller->hasGC())
270 Caller->setGC(CalledFunc->getGC());
271 else if (CalledFunc->getGC() != Caller->getGC())
275 // Get an iterator to the last basic block in the function, which will have
276 // the new function inlined after it.
278 Function::iterator LastBlock = &Caller->back();
280 // Make sure to capture all of the return instructions from the cloned
282 std::vector<ReturnInst*> Returns;
283 ClonedCodeInfo InlinedFunctionInfo;
284 Function::iterator FirstNewBlock;
286 { // Scope to destroy ValueMap after cloning.
287 DenseMap<const Value*, Value*> ValueMap;
289 assert(CalledFunc->arg_size() == CS.arg_size() &&
290 "No varargs calls can be inlined!");
292 // Calculate the vector of arguments to pass into the function cloner, which
293 // matches up the formal to the actual argument values.
294 CallSite::arg_iterator AI = CS.arg_begin();
296 for (Function::const_arg_iterator I = CalledFunc->arg_begin(),
297 E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) {
298 Value *ActualArg = *AI;
300 // When byval arguments actually inlined, we need to make the copy implied
301 // by them explicit. However, we don't do this if the callee is readonly
302 // or readnone, because the copy would be unneeded: the callee doesn't
303 // modify the struct.
304 if (CalledFunc->paramHasAttr(ArgNo+1, Attribute::ByVal) &&
305 !CalledFunc->onlyReadsMemory()) {
306 const Type *AggTy = cast<PointerType>(I->getType())->getElementType();
307 const Type *VoidPtrTy =
308 PointerType::getUnqual(Type::getInt8Ty(Context));
310 // Create the alloca. If we have TargetData, use nice alignment.
312 if (TD) Align = TD->getPrefTypeAlignment(AggTy);
313 Value *NewAlloca = new AllocaInst(AggTy, 0, Align,
315 &*Caller->begin()->begin());
317 const Type *Tys[] = { Type::getInt64Ty(Context) };
318 Function *MemCpyFn = Intrinsic::getDeclaration(Caller->getParent(),
321 Value *DestCast = new BitCastInst(NewAlloca, VoidPtrTy, "tmp", TheCall);
322 Value *SrcCast = new BitCastInst(*AI, VoidPtrTy, "tmp", TheCall);
326 Size = ConstantExpr::getSizeOf(AggTy);
328 Size = ConstantInt::get(Type::getInt64Ty(Context),
329 TD->getTypeStoreSize(AggTy));
331 // Always generate a memcpy of alignment 1 here because we don't know
332 // the alignment of the src pointer. Other optimizations can infer
334 Value *CallArgs[] = {
335 DestCast, SrcCast, Size,
336 ConstantInt::get(Type::getInt32Ty(Context), 1)
338 CallInst *TheMemCpy =
339 CallInst::Create(MemCpyFn, CallArgs, CallArgs+4, "", TheCall);
341 // If we have a call graph, update it.
343 CallGraphNode *MemCpyCGN = CG->getOrInsertFunction(MemCpyFn);
344 CallGraphNode *CallerNode = (*CG)[Caller];
345 CallerNode->addCalledFunction(TheMemCpy, MemCpyCGN);
348 // Uses of the argument in the function should use our new alloca
350 ActualArg = NewAlloca;
353 ValueMap[I] = ActualArg;
356 // Adjust llvm.dbg.region.end. If the CalledFunc has region end
357 // marker then clone that marker after next stop point at the
358 // call site. The function body cloner does not clone original
359 // region end marker from the CalledFunc. This will ensure that
360 // inlined function's scope ends at the right place.
361 const DbgRegionEndInst *DREI = findFnRegionEndMarker(CalledFunc);
363 for (BasicBlock::iterator BI = TheCall,
364 BE = TheCall->getParent()->end(); BI != BE; ++BI) {
365 if (DbgStopPointInst *DSPI = dyn_cast<DbgStopPointInst>(BI)) {
366 if (DbgRegionEndInst *NewDREI =
367 dyn_cast<DbgRegionEndInst>(DREI->clone(Context)))
368 NewDREI->insertAfter(DSPI);
374 // We want the inliner to prune the code as it copies. We would LOVE to
375 // have no dead or constant instructions leftover after inlining occurs
376 // (which can happen, e.g., because an argument was constant), but we'll be
377 // happy with whatever the cloner can do.
378 CloneAndPruneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i",
379 &InlinedFunctionInfo, TD);
381 // Remember the first block that is newly cloned over.
382 FirstNewBlock = LastBlock; ++FirstNewBlock;
384 // Update the callgraph if requested.
386 UpdateCallGraphAfterInlining(CS, FirstNewBlock, ValueMap, *CG);
389 // If there are any alloca instructions in the block that used to be the entry
390 // block for the callee, move them to the entry block of the caller. First
391 // calculate which instruction they should be inserted before. We insert the
392 // instructions at the end of the current alloca list.
395 BasicBlock::iterator InsertPoint = Caller->begin()->begin();
396 for (BasicBlock::iterator I = FirstNewBlock->begin(),
397 E = FirstNewBlock->end(); I != E; )
398 if (AllocaInst *AI = dyn_cast<AllocaInst>(I++)) {
399 // If the alloca is now dead, remove it. This often occurs due to code
401 if (AI->use_empty()) {
402 AI->eraseFromParent();
406 if (isa<Constant>(AI->getArraySize())) {
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()))
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(
418 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 Constant *StackSave, *StackRestore;
430 StackSave = Intrinsic::getDeclaration(M, Intrinsic::stacksave);
431 StackRestore = Intrinsic::getDeclaration(M, Intrinsic::stackrestore);
433 // If we are preserving the callgraph, add edges to the stacksave/restore
434 // functions for the calls we insert.
435 CallGraphNode *StackSaveCGN = 0, *StackRestoreCGN = 0, *CallerNode = 0;
437 // We know that StackSave/StackRestore are Function*'s, because they are
438 // intrinsics which must have the right types.
439 StackSaveCGN = CG->getOrInsertFunction(cast<Function>(StackSave));
440 StackRestoreCGN = CG->getOrInsertFunction(cast<Function>(StackRestore));
441 CallerNode = (*CG)[Caller];
444 // Insert the llvm.stacksave.
445 CallInst *SavedPtr = CallInst::Create(StackSave, "savedstack",
446 FirstNewBlock->begin());
447 if (CG) CallerNode->addCalledFunction(SavedPtr, StackSaveCGN);
449 // Insert a call to llvm.stackrestore before any return instructions in the
451 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
452 CallInst *CI = CallInst::Create(StackRestore, SavedPtr, "", Returns[i]);
453 if (CG) CallerNode->addCalledFunction(CI, StackRestoreCGN);
456 // Count the number of StackRestore calls we insert.
457 unsigned NumStackRestores = Returns.size();
459 // If we are inlining an invoke instruction, insert restores before each
460 // unwind. These unwinds will be rewritten into branches later.
461 if (InlinedFunctionInfo.ContainsUnwinds && isa<InvokeInst>(TheCall)) {
462 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
464 if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
465 CallInst::Create(StackRestore, SavedPtr, "", UI);
471 // If we are inlining tail call instruction through a call site that isn't
472 // marked 'tail', we must remove the tail marker for any calls in the inlined
473 // code. Also, calls inlined through a 'nounwind' call site should be marked
475 if (InlinedFunctionInfo.ContainsCalls &&
476 (MustClearTailCallFlags || MarkNoUnwind)) {
477 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
479 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
480 if (CallInst *CI = dyn_cast<CallInst>(I)) {
481 if (MustClearTailCallFlags)
482 CI->setTailCall(false);
484 CI->setDoesNotThrow();
488 // If we are inlining through a 'nounwind' call site then any inlined 'unwind'
489 // instructions are unreachable.
490 if (InlinedFunctionInfo.ContainsUnwinds && MarkNoUnwind)
491 for (Function::iterator BB = FirstNewBlock, E = Caller->end();
493 TerminatorInst *Term = BB->getTerminator();
494 if (isa<UnwindInst>(Term)) {
495 new UnreachableInst(Context, Term);
496 BB->getInstList().erase(Term);
500 // If we are inlining for an invoke instruction, we must make sure to rewrite
501 // any inlined 'unwind' instructions into branches to the invoke exception
502 // destination, and call instructions into invoke instructions.
503 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
504 HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo, CG);
506 // If we cloned in _exactly one_ basic block, and if that block ends in a
507 // return instruction, we splice the body of the inlined callee directly into
508 // the calling basic block.
509 if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) {
510 // Move all of the instructions right before the call.
511 OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(),
512 FirstNewBlock->begin(), FirstNewBlock->end());
513 // Remove the cloned basic block.
514 Caller->getBasicBlockList().pop_back();
516 // If the call site was an invoke instruction, add a branch to the normal
518 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
519 BranchInst::Create(II->getNormalDest(), TheCall);
521 // If the return instruction returned a value, replace uses of the call with
522 // uses of the returned value.
523 if (!TheCall->use_empty()) {
524 ReturnInst *R = Returns[0];
525 if (TheCall == R->getReturnValue())
526 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
528 TheCall->replaceAllUsesWith(R->getReturnValue());
530 // Since we are now done with the Call/Invoke, we can delete it.
531 TheCall->eraseFromParent();
533 // Since we are now done with the return instruction, delete it also.
534 Returns[0]->eraseFromParent();
536 // We are now done with the inlining.
540 // Otherwise, we have the normal case, of more than one block to inline or
541 // multiple return sites.
543 // We want to clone the entire callee function into the hole between the
544 // "starter" and "ender" blocks. How we accomplish this depends on whether
545 // this is an invoke instruction or a call instruction.
546 BasicBlock *AfterCallBB;
547 if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
549 // Add an unconditional branch to make this look like the CallInst case...
550 BranchInst *NewBr = BranchInst::Create(II->getNormalDest(), TheCall);
552 // Split the basic block. This guarantees that no PHI nodes will have to be
553 // updated due to new incoming edges, and make the invoke case more
554 // symmetric to the call case.
555 AfterCallBB = OrigBB->splitBasicBlock(NewBr,
556 CalledFunc->getName()+".exit");
558 } else { // It's a call
559 // If this is a call instruction, we need to split the basic block that
560 // the call lives in.
562 AfterCallBB = OrigBB->splitBasicBlock(TheCall,
563 CalledFunc->getName()+".exit");
566 // Change the branch that used to go to AfterCallBB to branch to the first
567 // basic block of the inlined function.
569 TerminatorInst *Br = OrigBB->getTerminator();
570 assert(Br && Br->getOpcode() == Instruction::Br &&
571 "splitBasicBlock broken!");
572 Br->setOperand(0, FirstNewBlock);
575 // Now that the function is correct, make it a little bit nicer. In
576 // particular, move the basic blocks inserted from the end of the function
577 // into the space made by splitting the source basic block.
578 Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(),
579 FirstNewBlock, Caller->end());
581 // Handle all of the return instructions that we just cloned in, and eliminate
582 // any users of the original call/invoke instruction.
583 const Type *RTy = CalledFunc->getReturnType();
585 if (Returns.size() > 1) {
586 // The PHI node should go at the front of the new basic block to merge all
587 // possible incoming values.
589 if (!TheCall->use_empty()) {
590 PHI = PHINode::Create(RTy, TheCall->getName(),
591 AfterCallBB->begin());
592 // Anything that used the result of the function call should now use the
593 // PHI node as their operand.
594 TheCall->replaceAllUsesWith(PHI);
597 // Loop over all of the return instructions adding entries to the PHI node
600 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
601 ReturnInst *RI = Returns[i];
602 assert(RI->getReturnValue()->getType() == PHI->getType() &&
603 "Ret value not consistent in function!");
604 PHI->addIncoming(RI->getReturnValue(), RI->getParent());
608 // Add a branch to the merge points and remove return instructions.
609 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
610 ReturnInst *RI = Returns[i];
611 BranchInst::Create(AfterCallBB, RI);
612 RI->eraseFromParent();
614 } else if (!Returns.empty()) {
615 // Otherwise, if there is exactly one return value, just replace anything
616 // using the return value of the call with the computed value.
617 if (!TheCall->use_empty()) {
618 if (TheCall == Returns[0]->getReturnValue())
619 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
621 TheCall->replaceAllUsesWith(Returns[0]->getReturnValue());
624 // Splice the code from the return block into the block that it will return
625 // to, which contains the code that was after the call.
626 BasicBlock *ReturnBB = Returns[0]->getParent();
627 AfterCallBB->getInstList().splice(AfterCallBB->begin(),
628 ReturnBB->getInstList());
630 // Update PHI nodes that use the ReturnBB to use the AfterCallBB.
631 ReturnBB->replaceAllUsesWith(AfterCallBB);
633 // Delete the return instruction now and empty ReturnBB now.
634 Returns[0]->eraseFromParent();
635 ReturnBB->eraseFromParent();
636 } else if (!TheCall->use_empty()) {
637 // No returns, but something is using the return value of the call. Just
639 TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
642 // Since we are now done with the Call/Invoke, we can delete it.
643 TheCall->eraseFromParent();
645 // We should always be able to fold the entry block of the function into the
646 // single predecessor of the block...
647 assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!");
648 BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0);
650 // Splice the code entry block into calling block, right before the
651 // unconditional branch.
652 OrigBB->getInstList().splice(Br, CalleeEntry->getInstList());
653 CalleeEntry->replaceAllUsesWith(OrigBB); // Update PHI nodes
655 // Remove the unconditional branch.
656 OrigBB->getInstList().erase(Br);
658 // Now we can remove the CalleeEntry block, which is now empty.
659 Caller->getBasicBlockList().erase(CalleeEntry);