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1 //===- InlineFunction.cpp - Code to perform function inlining -------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements inlining of a function into a call site, resolving
11 // parameters and the return value as appropriate.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/Transforms/Utils/Cloning.h"
16 #include "llvm/ADT/SmallVector.h"
17 #include "llvm/ADT/StringExtras.h"
18 #include "llvm/Analysis/CallGraph.h"
19 #include "llvm/Analysis/InstructionSimplify.h"
20 #include "llvm/IR/Attributes.h"
21 #include "llvm/IR/CallSite.h"
22 #include "llvm/IR/CFG.h"
23 #include "llvm/IR/Constants.h"
24 #include "llvm/IR/DataLayout.h"
25 #include "llvm/IR/DebugInfo.h"
26 #include "llvm/IR/DerivedTypes.h"
27 #include "llvm/IR/IRBuilder.h"
28 #include "llvm/IR/Instructions.h"
29 #include "llvm/IR/IntrinsicInst.h"
30 #include "llvm/IR/Intrinsics.h"
31 #include "llvm/IR/Module.h"
32 #include "llvm/Transforms/Utils/Local.h"
33 using namespace llvm;
34 
InlineFunction(CallInst * CI,InlineFunctionInfo & IFI,bool InsertLifetime)35 bool llvm::InlineFunction(CallInst *CI, InlineFunctionInfo &IFI,
36                           bool InsertLifetime) {
37   return InlineFunction(CallSite(CI), IFI, InsertLifetime);
38 }
InlineFunction(InvokeInst * II,InlineFunctionInfo & IFI,bool InsertLifetime)39 bool llvm::InlineFunction(InvokeInst *II, InlineFunctionInfo &IFI,
40                           bool InsertLifetime) {
41   return InlineFunction(CallSite(II), IFI, InsertLifetime);
42 }
43 
44 namespace {
45   /// A class for recording information about inlining through an invoke.
46   class InvokeInliningInfo {
47     BasicBlock *OuterResumeDest; ///< Destination of the invoke's unwind.
48     BasicBlock *InnerResumeDest; ///< Destination for the callee's resume.
49     LandingPadInst *CallerLPad;  ///< LandingPadInst associated with the invoke.
50     PHINode *InnerEHValuesPHI;   ///< PHI for EH values from landingpad insts.
51     SmallVector<Value*, 8> UnwindDestPHIValues;
52 
53   public:
InvokeInliningInfo(InvokeInst * II)54     InvokeInliningInfo(InvokeInst *II)
55       : OuterResumeDest(II->getUnwindDest()), InnerResumeDest(nullptr),
56         CallerLPad(nullptr), InnerEHValuesPHI(nullptr) {
57       // If there are PHI nodes in the unwind destination block, we need to keep
58       // track of which values came into them from the invoke before removing
59       // the edge from this block.
60       llvm::BasicBlock *InvokeBB = II->getParent();
61       BasicBlock::iterator I = OuterResumeDest->begin();
62       for (; isa<PHINode>(I); ++I) {
63         // Save the value to use for this edge.
64         PHINode *PHI = cast<PHINode>(I);
65         UnwindDestPHIValues.push_back(PHI->getIncomingValueForBlock(InvokeBB));
66       }
67 
68       CallerLPad = cast<LandingPadInst>(I);
69     }
70 
71     /// getOuterResumeDest - The outer unwind destination is the target of
72     /// unwind edges introduced for calls within the inlined function.
getOuterResumeDest() const73     BasicBlock *getOuterResumeDest() const {
74       return OuterResumeDest;
75     }
76 
77     BasicBlock *getInnerResumeDest();
78 
getLandingPadInst() const79     LandingPadInst *getLandingPadInst() const { return CallerLPad; }
80 
81     /// forwardResume - Forward the 'resume' instruction to the caller's landing
82     /// pad block. When the landing pad block has only one predecessor, this is
83     /// a simple branch. When there is more than one predecessor, we need to
84     /// split the landing pad block after the landingpad instruction and jump
85     /// to there.
86     void forwardResume(ResumeInst *RI,
87                        SmallPtrSet<LandingPadInst*, 16> &InlinedLPads);
88 
89     /// addIncomingPHIValuesFor - Add incoming-PHI values to the unwind
90     /// destination block for the given basic block, using the values for the
91     /// original invoke's source block.
addIncomingPHIValuesFor(BasicBlock * BB) const92     void addIncomingPHIValuesFor(BasicBlock *BB) const {
93       addIncomingPHIValuesForInto(BB, OuterResumeDest);
94     }
95 
addIncomingPHIValuesForInto(BasicBlock * src,BasicBlock * dest) const96     void addIncomingPHIValuesForInto(BasicBlock *src, BasicBlock *dest) const {
97       BasicBlock::iterator I = dest->begin();
98       for (unsigned i = 0, e = UnwindDestPHIValues.size(); i != e; ++i, ++I) {
99         PHINode *phi = cast<PHINode>(I);
100         phi->addIncoming(UnwindDestPHIValues[i], src);
101       }
102     }
103   };
104 }
105 
106 /// getInnerResumeDest - Get or create a target for the branch from ResumeInsts.
getInnerResumeDest()107 BasicBlock *InvokeInliningInfo::getInnerResumeDest() {
108   if (InnerResumeDest) return InnerResumeDest;
109 
110   // Split the landing pad.
111   BasicBlock::iterator SplitPoint = CallerLPad; ++SplitPoint;
112   InnerResumeDest =
113     OuterResumeDest->splitBasicBlock(SplitPoint,
114                                      OuterResumeDest->getName() + ".body");
115 
116   // The number of incoming edges we expect to the inner landing pad.
117   const unsigned PHICapacity = 2;
118 
119   // Create corresponding new PHIs for all the PHIs in the outer landing pad.
120   BasicBlock::iterator InsertPoint = InnerResumeDest->begin();
121   BasicBlock::iterator I = OuterResumeDest->begin();
122   for (unsigned i = 0, e = UnwindDestPHIValues.size(); i != e; ++i, ++I) {
123     PHINode *OuterPHI = cast<PHINode>(I);
124     PHINode *InnerPHI = PHINode::Create(OuterPHI->getType(), PHICapacity,
125                                         OuterPHI->getName() + ".lpad-body",
126                                         InsertPoint);
127     OuterPHI->replaceAllUsesWith(InnerPHI);
128     InnerPHI->addIncoming(OuterPHI, OuterResumeDest);
129   }
130 
131   // Create a PHI for the exception values.
132   InnerEHValuesPHI = PHINode::Create(CallerLPad->getType(), PHICapacity,
133                                      "eh.lpad-body", InsertPoint);
134   CallerLPad->replaceAllUsesWith(InnerEHValuesPHI);
135   InnerEHValuesPHI->addIncoming(CallerLPad, OuterResumeDest);
136 
137   // All done.
138   return InnerResumeDest;
139 }
140 
141 /// forwardResume - Forward the 'resume' instruction to the caller's landing pad
142 /// block. When the landing pad block has only one predecessor, this is a simple
143 /// branch. When there is more than one predecessor, we need to split the
144 /// landing pad block after the landingpad instruction and jump to there.
forwardResume(ResumeInst * RI,SmallPtrSet<LandingPadInst *,16> & InlinedLPads)145 void InvokeInliningInfo::forwardResume(ResumeInst *RI,
146                                SmallPtrSet<LandingPadInst*, 16> &InlinedLPads) {
147   BasicBlock *Dest = getInnerResumeDest();
148   BasicBlock *Src = RI->getParent();
149 
150   BranchInst::Create(Dest, Src);
151 
152   // Update the PHIs in the destination. They were inserted in an order which
153   // makes this work.
154   addIncomingPHIValuesForInto(Src, Dest);
155 
156   InnerEHValuesPHI->addIncoming(RI->getOperand(0), Src);
157   RI->eraseFromParent();
158 }
159 
160 /// HandleCallsInBlockInlinedThroughInvoke - When we inline a basic block into
161 /// an invoke, we have to turn all of the calls that can throw into
162 /// invokes.  This function analyze BB to see if there are any calls, and if so,
163 /// it rewrites them to be invokes that jump to InvokeDest and fills in the PHI
164 /// nodes in that block with the values specified in InvokeDestPHIValues.
HandleCallsInBlockInlinedThroughInvoke(BasicBlock * BB,InvokeInliningInfo & Invoke)165 static void HandleCallsInBlockInlinedThroughInvoke(BasicBlock *BB,
166                                                    InvokeInliningInfo &Invoke) {
167   for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) {
168     Instruction *I = BBI++;
169 
170     // We only need to check for function calls: inlined invoke
171     // instructions require no special handling.
172     CallInst *CI = dyn_cast<CallInst>(I);
173 
174     // If this call cannot unwind, don't convert it to an invoke.
175     // Inline asm calls cannot throw.
176     if (!CI || CI->doesNotThrow() || isa<InlineAsm>(CI->getCalledValue()))
177       continue;
178 
179     // Convert this function call into an invoke instruction.  First, split the
180     // basic block.
181     BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc");
182 
183     // Delete the unconditional branch inserted by splitBasicBlock
184     BB->getInstList().pop_back();
185 
186     // Create the new invoke instruction.
187     ImmutableCallSite CS(CI);
188     SmallVector<Value*, 8> InvokeArgs(CS.arg_begin(), CS.arg_end());
189     InvokeInst *II = InvokeInst::Create(CI->getCalledValue(), Split,
190                                         Invoke.getOuterResumeDest(),
191                                         InvokeArgs, CI->getName(), BB);
192     II->setDebugLoc(CI->getDebugLoc());
193     II->setCallingConv(CI->getCallingConv());
194     II->setAttributes(CI->getAttributes());
195 
196     // Make sure that anything using the call now uses the invoke!  This also
197     // updates the CallGraph if present, because it uses a WeakVH.
198     CI->replaceAllUsesWith(II);
199 
200     // Delete the original call
201     Split->getInstList().pop_front();
202 
203     // Update any PHI nodes in the exceptional block to indicate that there is
204     // now a new entry in them.
205     Invoke.addIncomingPHIValuesFor(BB);
206     return;
207   }
208 }
209 
210 /// HandleInlinedInvoke - If we inlined an invoke site, we need to convert calls
211 /// in the body of the inlined function into invokes.
212 ///
213 /// II is the invoke instruction being inlined.  FirstNewBlock is the first
214 /// block of the inlined code (the last block is the end of the function),
215 /// and InlineCodeInfo is information about the code that got inlined.
HandleInlinedInvoke(InvokeInst * II,BasicBlock * FirstNewBlock,ClonedCodeInfo & InlinedCodeInfo)216 static void HandleInlinedInvoke(InvokeInst *II, BasicBlock *FirstNewBlock,
217                                 ClonedCodeInfo &InlinedCodeInfo) {
218   BasicBlock *InvokeDest = II->getUnwindDest();
219 
220   Function *Caller = FirstNewBlock->getParent();
221 
222   // The inlined code is currently at the end of the function, scan from the
223   // start of the inlined code to its end, checking for stuff we need to
224   // rewrite.
225   InvokeInliningInfo Invoke(II);
226 
227   // Get all of the inlined landing pad instructions.
228   SmallPtrSet<LandingPadInst*, 16> InlinedLPads;
229   for (Function::iterator I = FirstNewBlock, E = Caller->end(); I != E; ++I)
230     if (InvokeInst *II = dyn_cast<InvokeInst>(I->getTerminator()))
231       InlinedLPads.insert(II->getLandingPadInst());
232 
233   // Append the clauses from the outer landing pad instruction into the inlined
234   // landing pad instructions.
235   LandingPadInst *OuterLPad = Invoke.getLandingPadInst();
236   for (SmallPtrSet<LandingPadInst*, 16>::iterator I = InlinedLPads.begin(),
237          E = InlinedLPads.end(); I != E; ++I) {
238     LandingPadInst *InlinedLPad = *I;
239     unsigned OuterNum = OuterLPad->getNumClauses();
240     InlinedLPad->reserveClauses(OuterNum);
241     for (unsigned OuterIdx = 0; OuterIdx != OuterNum; ++OuterIdx)
242       InlinedLPad->addClause(OuterLPad->getClause(OuterIdx));
243     if (OuterLPad->isCleanup())
244       InlinedLPad->setCleanup(true);
245   }
246 
247   for (Function::iterator BB = FirstNewBlock, E = Caller->end(); BB != E; ++BB){
248     if (InlinedCodeInfo.ContainsCalls)
249       HandleCallsInBlockInlinedThroughInvoke(BB, Invoke);
250 
251     // Forward any resumes that are remaining here.
252     if (ResumeInst *RI = dyn_cast<ResumeInst>(BB->getTerminator()))
253       Invoke.forwardResume(RI, InlinedLPads);
254   }
255 
256   // Now that everything is happy, we have one final detail.  The PHI nodes in
257   // the exception destination block still have entries due to the original
258   // invoke instruction. Eliminate these entries (which might even delete the
259   // PHI node) now.
260   InvokeDest->removePredecessor(II->getParent());
261 }
262 
263 /// UpdateCallGraphAfterInlining - Once we have cloned code over from a callee
264 /// into the caller, update the specified callgraph to reflect the changes we
265 /// made.  Note that it's possible that not all code was copied over, so only
266 /// some edges of the callgraph may remain.
UpdateCallGraphAfterInlining(CallSite CS,Function::iterator FirstNewBlock,ValueToValueMapTy & VMap,InlineFunctionInfo & IFI)267 static void UpdateCallGraphAfterInlining(CallSite CS,
268                                          Function::iterator FirstNewBlock,
269                                          ValueToValueMapTy &VMap,
270                                          InlineFunctionInfo &IFI) {
271   CallGraph &CG = *IFI.CG;
272   const Function *Caller = CS.getInstruction()->getParent()->getParent();
273   const Function *Callee = CS.getCalledFunction();
274   CallGraphNode *CalleeNode = CG[Callee];
275   CallGraphNode *CallerNode = CG[Caller];
276 
277   // Since we inlined some uninlined call sites in the callee into the caller,
278   // add edges from the caller to all of the callees of the callee.
279   CallGraphNode::iterator I = CalleeNode->begin(), E = CalleeNode->end();
280 
281   // Consider the case where CalleeNode == CallerNode.
282   CallGraphNode::CalledFunctionsVector CallCache;
283   if (CalleeNode == CallerNode) {
284     CallCache.assign(I, E);
285     I = CallCache.begin();
286     E = CallCache.end();
287   }
288 
289   for (; I != E; ++I) {
290     const Value *OrigCall = I->first;
291 
292     ValueToValueMapTy::iterator VMI = VMap.find(OrigCall);
293     // Only copy the edge if the call was inlined!
294     if (VMI == VMap.end() || VMI->second == nullptr)
295       continue;
296 
297     // If the call was inlined, but then constant folded, there is no edge to
298     // add.  Check for this case.
299     Instruction *NewCall = dyn_cast<Instruction>(VMI->second);
300     if (!NewCall) continue;
301 
302     // Remember that this call site got inlined for the client of
303     // InlineFunction.
304     IFI.InlinedCalls.push_back(NewCall);
305 
306     // It's possible that inlining the callsite will cause it to go from an
307     // indirect to a direct call by resolving a function pointer.  If this
308     // happens, set the callee of the new call site to a more precise
309     // destination.  This can also happen if the call graph node of the caller
310     // was just unnecessarily imprecise.
311     if (!I->second->getFunction())
312       if (Function *F = CallSite(NewCall).getCalledFunction()) {
313         // Indirect call site resolved to direct call.
314         CallerNode->addCalledFunction(CallSite(NewCall), CG[F]);
315 
316         continue;
317       }
318 
319     CallerNode->addCalledFunction(CallSite(NewCall), I->second);
320   }
321 
322   // Update the call graph by deleting the edge from Callee to Caller.  We must
323   // do this after the loop above in case Caller and Callee are the same.
324   CallerNode->removeCallEdgeFor(CS);
325 }
326 
HandleByValArgumentInit(Value * Dst,Value * Src,Module * M,BasicBlock * InsertBlock,InlineFunctionInfo & IFI)327 static void HandleByValArgumentInit(Value *Dst, Value *Src, Module *M,
328                                     BasicBlock *InsertBlock,
329                                     InlineFunctionInfo &IFI) {
330   LLVMContext &Context = Src->getContext();
331   Type *VoidPtrTy = Type::getInt8PtrTy(Context);
332   Type *AggTy = cast<PointerType>(Src->getType())->getElementType();
333   Type *Tys[3] = { VoidPtrTy, VoidPtrTy, Type::getInt64Ty(Context) };
334   Function *MemCpyFn = Intrinsic::getDeclaration(M, Intrinsic::memcpy, Tys);
335   IRBuilder<> builder(InsertBlock->begin());
336   Value *DstCast = builder.CreateBitCast(Dst, VoidPtrTy, "tmp");
337   Value *SrcCast = builder.CreateBitCast(Src, VoidPtrTy, "tmp");
338 
339   Value *Size;
340   if (IFI.DL == nullptr)
341     Size = ConstantExpr::getSizeOf(AggTy);
342   else
343     Size = ConstantInt::get(Type::getInt64Ty(Context),
344                             IFI.DL->getTypeStoreSize(AggTy));
345 
346   // Always generate a memcpy of alignment 1 here because we don't know
347   // the alignment of the src pointer.  Other optimizations can infer
348   // better alignment.
349   Value *CallArgs[] = {
350     DstCast, SrcCast, Size,
351     ConstantInt::get(Type::getInt32Ty(Context), 1),
352     ConstantInt::getFalse(Context) // isVolatile
353   };
354   builder.CreateCall(MemCpyFn, CallArgs);
355 }
356 
357 /// HandleByValArgument - When inlining a call site that has a byval argument,
358 /// we have to make the implicit memcpy explicit by adding it.
HandleByValArgument(Value * Arg,Instruction * TheCall,const Function * CalledFunc,InlineFunctionInfo & IFI,unsigned ByValAlignment)359 static Value *HandleByValArgument(Value *Arg, Instruction *TheCall,
360                                   const Function *CalledFunc,
361                                   InlineFunctionInfo &IFI,
362                                   unsigned ByValAlignment) {
363   PointerType *ArgTy = cast<PointerType>(Arg->getType());
364   Type *AggTy = ArgTy->getElementType();
365 
366   // If the called function is readonly, then it could not mutate the caller's
367   // copy of the byval'd memory.  In this case, it is safe to elide the copy and
368   // temporary.
369   if (CalledFunc->onlyReadsMemory()) {
370     // If the byval argument has a specified alignment that is greater than the
371     // passed in pointer, then we either have to round up the input pointer or
372     // give up on this transformation.
373     if (ByValAlignment <= 1)  // 0 = unspecified, 1 = no particular alignment.
374       return Arg;
375 
376     // If the pointer is already known to be sufficiently aligned, or if we can
377     // round it up to a larger alignment, then we don't need a temporary.
378     if (getOrEnforceKnownAlignment(Arg, ByValAlignment,
379                                    IFI.DL) >= ByValAlignment)
380       return Arg;
381 
382     // Otherwise, we have to make a memcpy to get a safe alignment.  This is bad
383     // for code quality, but rarely happens and is required for correctness.
384   }
385 
386   // Create the alloca.  If we have DataLayout, use nice alignment.
387   unsigned Align = 1;
388   if (IFI.DL)
389     Align = IFI.DL->getPrefTypeAlignment(AggTy);
390 
391   // If the byval had an alignment specified, we *must* use at least that
392   // alignment, as it is required by the byval argument (and uses of the
393   // pointer inside the callee).
394   Align = std::max(Align, ByValAlignment);
395 
396   Function *Caller = TheCall->getParent()->getParent();
397 
398   Value *NewAlloca = new AllocaInst(AggTy, nullptr, Align, Arg->getName(),
399                                     &*Caller->begin()->begin());
400   IFI.StaticAllocas.push_back(cast<AllocaInst>(NewAlloca));
401 
402   // Uses of the argument in the function should use our new alloca
403   // instead.
404   return NewAlloca;
405 }
406 
407 // isUsedByLifetimeMarker - Check whether this Value is used by a lifetime
408 // intrinsic.
isUsedByLifetimeMarker(Value * V)409 static bool isUsedByLifetimeMarker(Value *V) {
410   for (User *U : V->users()) {
411     if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U)) {
412       switch (II->getIntrinsicID()) {
413       default: break;
414       case Intrinsic::lifetime_start:
415       case Intrinsic::lifetime_end:
416         return true;
417       }
418     }
419   }
420   return false;
421 }
422 
423 // hasLifetimeMarkers - Check whether the given alloca already has
424 // lifetime.start or lifetime.end intrinsics.
hasLifetimeMarkers(AllocaInst * AI)425 static bool hasLifetimeMarkers(AllocaInst *AI) {
426   Type *Ty = AI->getType();
427   Type *Int8PtrTy = Type::getInt8PtrTy(Ty->getContext(),
428                                        Ty->getPointerAddressSpace());
429   if (Ty == Int8PtrTy)
430     return isUsedByLifetimeMarker(AI);
431 
432   // Do a scan to find all the casts to i8*.
433   for (User *U : AI->users()) {
434     if (U->getType() != Int8PtrTy) continue;
435     if (U->stripPointerCasts() != AI) continue;
436     if (isUsedByLifetimeMarker(U))
437       return true;
438   }
439   return false;
440 }
441 
442 /// updateInlinedAtInfo - Helper function used by fixupLineNumbers to
443 /// recursively update InlinedAtEntry of a DebugLoc.
updateInlinedAtInfo(const DebugLoc & DL,const DebugLoc & InlinedAtDL,LLVMContext & Ctx)444 static DebugLoc updateInlinedAtInfo(const DebugLoc &DL,
445                                     const DebugLoc &InlinedAtDL,
446                                     LLVMContext &Ctx) {
447   if (MDNode *IA = DL.getInlinedAt(Ctx)) {
448     DebugLoc NewInlinedAtDL
449       = updateInlinedAtInfo(DebugLoc::getFromDILocation(IA), InlinedAtDL, Ctx);
450     return DebugLoc::get(DL.getLine(), DL.getCol(), DL.getScope(Ctx),
451                          NewInlinedAtDL.getAsMDNode(Ctx));
452   }
453 
454   return DebugLoc::get(DL.getLine(), DL.getCol(), DL.getScope(Ctx),
455                        InlinedAtDL.getAsMDNode(Ctx));
456 }
457 
458 /// fixupLineNumbers - Update inlined instructions' line numbers to
459 /// to encode location where these instructions are inlined.
fixupLineNumbers(Function * Fn,Function::iterator FI,Instruction * TheCall)460 static void fixupLineNumbers(Function *Fn, Function::iterator FI,
461                              Instruction *TheCall) {
462   DebugLoc TheCallDL = TheCall->getDebugLoc();
463   if (TheCallDL.isUnknown())
464     return;
465 
466   for (; FI != Fn->end(); ++FI) {
467     for (BasicBlock::iterator BI = FI->begin(), BE = FI->end();
468          BI != BE; ++BI) {
469       DebugLoc DL = BI->getDebugLoc();
470       if (DL.isUnknown()) {
471         // If the inlined instruction has no line number, make it look as if it
472         // originates from the call location. This is important for
473         // ((__always_inline__, __nodebug__)) functions which must use caller
474         // location for all instructions in their function body.
475         BI->setDebugLoc(TheCallDL);
476       } else {
477         BI->setDebugLoc(updateInlinedAtInfo(DL, TheCallDL, BI->getContext()));
478         if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(BI)) {
479           LLVMContext &Ctx = BI->getContext();
480           MDNode *InlinedAt = BI->getDebugLoc().getInlinedAt(Ctx);
481           DVI->setOperand(2, createInlinedVariable(DVI->getVariable(),
482                                                    InlinedAt, Ctx));
483         }
484       }
485     }
486   }
487 }
488 
489 /// Returns a musttail call instruction if one immediately precedes the given
490 /// return instruction with an optional bitcast instruction between them.
getPrecedingMustTailCall(ReturnInst * RI)491 static CallInst *getPrecedingMustTailCall(ReturnInst *RI) {
492   Instruction *Prev = RI->getPrevNode();
493   if (!Prev)
494     return nullptr;
495 
496   if (Value *RV = RI->getReturnValue()) {
497     if (RV != Prev)
498       return nullptr;
499 
500     // Look through the optional bitcast.
501     if (auto *BI = dyn_cast<BitCastInst>(Prev)) {
502       RV = BI->getOperand(0);
503       Prev = BI->getPrevNode();
504       if (!Prev || RV != Prev)
505         return nullptr;
506     }
507   }
508 
509   if (auto *CI = dyn_cast<CallInst>(Prev)) {
510     if (CI->isMustTailCall())
511       return CI;
512   }
513   return nullptr;
514 }
515 
516 /// InlineFunction - This function inlines the called function into the basic
517 /// block of the caller.  This returns false if it is not possible to inline
518 /// this call.  The program is still in a well defined state if this occurs
519 /// though.
520 ///
521 /// Note that this only does one level of inlining.  For example, if the
522 /// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
523 /// exists in the instruction stream.  Similarly this will inline a recursive
524 /// function by one level.
InlineFunction(CallSite CS,InlineFunctionInfo & IFI,bool InsertLifetime)525 bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
526                           bool InsertLifetime) {
527   Instruction *TheCall = CS.getInstruction();
528   assert(TheCall->getParent() && TheCall->getParent()->getParent() &&
529          "Instruction not in function!");
530 
531   // If IFI has any state in it, zap it before we fill it in.
532   IFI.reset();
533 
534   const Function *CalledFunc = CS.getCalledFunction();
535   if (!CalledFunc ||              // Can't inline external function or indirect
536       CalledFunc->isDeclaration() || // call, or call to a vararg function!
537       CalledFunc->getFunctionType()->isVarArg()) return false;
538 
539   // If the call to the callee cannot throw, set the 'nounwind' flag on any
540   // calls that we inline.
541   bool MarkNoUnwind = CS.doesNotThrow();
542 
543   BasicBlock *OrigBB = TheCall->getParent();
544   Function *Caller = OrigBB->getParent();
545 
546   // GC poses two hazards to inlining, which only occur when the callee has GC:
547   //  1. If the caller has no GC, then the callee's GC must be propagated to the
548   //     caller.
549   //  2. If the caller has a differing GC, it is invalid to inline.
550   if (CalledFunc->hasGC()) {
551     if (!Caller->hasGC())
552       Caller->setGC(CalledFunc->getGC());
553     else if (CalledFunc->getGC() != Caller->getGC())
554       return false;
555   }
556 
557   // Get the personality function from the callee if it contains a landing pad.
558   Value *CalleePersonality = nullptr;
559   for (Function::const_iterator I = CalledFunc->begin(), E = CalledFunc->end();
560        I != E; ++I)
561     if (const InvokeInst *II = dyn_cast<InvokeInst>(I->getTerminator())) {
562       const BasicBlock *BB = II->getUnwindDest();
563       const LandingPadInst *LP = BB->getLandingPadInst();
564       CalleePersonality = LP->getPersonalityFn();
565       break;
566     }
567 
568   // Find the personality function used by the landing pads of the caller. If it
569   // exists, then check to see that it matches the personality function used in
570   // the callee.
571   if (CalleePersonality) {
572     for (Function::const_iterator I = Caller->begin(), E = Caller->end();
573          I != E; ++I)
574       if (const InvokeInst *II = dyn_cast<InvokeInst>(I->getTerminator())) {
575         const BasicBlock *BB = II->getUnwindDest();
576         const LandingPadInst *LP = BB->getLandingPadInst();
577 
578         // If the personality functions match, then we can perform the
579         // inlining. Otherwise, we can't inline.
580         // TODO: This isn't 100% true. Some personality functions are proper
581         //       supersets of others and can be used in place of the other.
582         if (LP->getPersonalityFn() != CalleePersonality)
583           return false;
584 
585         break;
586       }
587   }
588 
589   // Get an iterator to the last basic block in the function, which will have
590   // the new function inlined after it.
591   Function::iterator LastBlock = &Caller->back();
592 
593   // Make sure to capture all of the return instructions from the cloned
594   // function.
595   SmallVector<ReturnInst*, 8> Returns;
596   ClonedCodeInfo InlinedFunctionInfo;
597   Function::iterator FirstNewBlock;
598 
599   { // Scope to destroy VMap after cloning.
600     ValueToValueMapTy VMap;
601     // Keep a list of pair (dst, src) to emit byval initializations.
602     SmallVector<std::pair<Value*, Value*>, 4> ByValInit;
603 
604     assert(CalledFunc->arg_size() == CS.arg_size() &&
605            "No varargs calls can be inlined!");
606 
607     // Calculate the vector of arguments to pass into the function cloner, which
608     // matches up the formal to the actual argument values.
609     CallSite::arg_iterator AI = CS.arg_begin();
610     unsigned ArgNo = 0;
611     for (Function::const_arg_iterator I = CalledFunc->arg_begin(),
612          E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) {
613       Value *ActualArg = *AI;
614 
615       // When byval arguments actually inlined, we need to make the copy implied
616       // by them explicit.  However, we don't do this if the callee is readonly
617       // or readnone, because the copy would be unneeded: the callee doesn't
618       // modify the struct.
619       if (CS.isByValArgument(ArgNo)) {
620         ActualArg = HandleByValArgument(ActualArg, TheCall, CalledFunc, IFI,
621                                         CalledFunc->getParamAlignment(ArgNo+1));
622         if (ActualArg != *AI)
623           ByValInit.push_back(std::make_pair(ActualArg, (Value*) *AI));
624       }
625 
626       VMap[I] = ActualArg;
627     }
628 
629     // We want the inliner to prune the code as it copies.  We would LOVE to
630     // have no dead or constant instructions leftover after inlining occurs
631     // (which can happen, e.g., because an argument was constant), but we'll be
632     // happy with whatever the cloner can do.
633     CloneAndPruneFunctionInto(Caller, CalledFunc, VMap,
634                               /*ModuleLevelChanges=*/false, Returns, ".i",
635                               &InlinedFunctionInfo, IFI.DL, TheCall);
636 
637     // Remember the first block that is newly cloned over.
638     FirstNewBlock = LastBlock; ++FirstNewBlock;
639 
640     // Inject byval arguments initialization.
641     for (std::pair<Value*, Value*> &Init : ByValInit)
642       HandleByValArgumentInit(Init.first, Init.second, Caller->getParent(),
643                               FirstNewBlock, IFI);
644 
645     // Update the callgraph if requested.
646     if (IFI.CG)
647       UpdateCallGraphAfterInlining(CS, FirstNewBlock, VMap, IFI);
648 
649     // Update inlined instructions' line number information.
650     fixupLineNumbers(Caller, FirstNewBlock, TheCall);
651   }
652 
653   // If there are any alloca instructions in the block that used to be the entry
654   // block for the callee, move them to the entry block of the caller.  First
655   // calculate which instruction they should be inserted before.  We insert the
656   // instructions at the end of the current alloca list.
657   {
658     BasicBlock::iterator InsertPoint = Caller->begin()->begin();
659     for (BasicBlock::iterator I = FirstNewBlock->begin(),
660          E = FirstNewBlock->end(); I != E; ) {
661       AllocaInst *AI = dyn_cast<AllocaInst>(I++);
662       if (!AI) continue;
663 
664       // If the alloca is now dead, remove it.  This often occurs due to code
665       // specialization.
666       if (AI->use_empty()) {
667         AI->eraseFromParent();
668         continue;
669       }
670 
671       if (!isa<Constant>(AI->getArraySize()))
672         continue;
673 
674       // Keep track of the static allocas that we inline into the caller.
675       IFI.StaticAllocas.push_back(AI);
676 
677       // Scan for the block of allocas that we can move over, and move them
678       // all at once.
679       while (isa<AllocaInst>(I) &&
680              isa<Constant>(cast<AllocaInst>(I)->getArraySize())) {
681         IFI.StaticAllocas.push_back(cast<AllocaInst>(I));
682         ++I;
683       }
684 
685       // Transfer all of the allocas over in a block.  Using splice means
686       // that the instructions aren't removed from the symbol table, then
687       // reinserted.
688       Caller->getEntryBlock().getInstList().splice(InsertPoint,
689                                                    FirstNewBlock->getInstList(),
690                                                    AI, I);
691     }
692   }
693 
694   bool InlinedMustTailCalls = false;
695   if (InlinedFunctionInfo.ContainsCalls) {
696     CallInst::TailCallKind CallSiteTailKind = CallInst::TCK_None;
697     if (CallInst *CI = dyn_cast<CallInst>(TheCall))
698       CallSiteTailKind = CI->getTailCallKind();
699 
700     for (Function::iterator BB = FirstNewBlock, E = Caller->end(); BB != E;
701          ++BB) {
702       for (Instruction &I : *BB) {
703         CallInst *CI = dyn_cast<CallInst>(&I);
704         if (!CI)
705           continue;
706 
707         // We need to reduce the strength of any inlined tail calls.  For
708         // musttail, we have to avoid introducing potential unbounded stack
709         // growth.  For example, if functions 'f' and 'g' are mutually recursive
710         // with musttail, we can inline 'g' into 'f' so long as we preserve
711         // musttail on the cloned call to 'f'.  If either the inlined call site
712         // or the cloned call site is *not* musttail, the program already has
713         // one frame of stack growth, so it's safe to remove musttail.  Here is
714         // a table of example transformations:
715         //
716         //    f -> musttail g -> musttail f  ==>  f -> musttail f
717         //    f -> musttail g ->     tail f  ==>  f ->     tail f
718         //    f ->          g -> musttail f  ==>  f ->          f
719         //    f ->          g ->     tail f  ==>  f ->          f
720         CallInst::TailCallKind ChildTCK = CI->getTailCallKind();
721         ChildTCK = std::min(CallSiteTailKind, ChildTCK);
722         CI->setTailCallKind(ChildTCK);
723         InlinedMustTailCalls |= CI->isMustTailCall();
724 
725         // Calls inlined through a 'nounwind' call site should be marked
726         // 'nounwind'.
727         if (MarkNoUnwind)
728           CI->setDoesNotThrow();
729       }
730     }
731   }
732 
733   // Leave lifetime markers for the static alloca's, scoping them to the
734   // function we just inlined.
735   if (InsertLifetime && !IFI.StaticAllocas.empty()) {
736     IRBuilder<> builder(FirstNewBlock->begin());
737     for (unsigned ai = 0, ae = IFI.StaticAllocas.size(); ai != ae; ++ai) {
738       AllocaInst *AI = IFI.StaticAllocas[ai];
739 
740       // If the alloca is already scoped to something smaller than the whole
741       // function then there's no need to add redundant, less accurate markers.
742       if (hasLifetimeMarkers(AI))
743         continue;
744 
745       // Try to determine the size of the allocation.
746       ConstantInt *AllocaSize = nullptr;
747       if (ConstantInt *AIArraySize =
748           dyn_cast<ConstantInt>(AI->getArraySize())) {
749         if (IFI.DL) {
750           Type *AllocaType = AI->getAllocatedType();
751           uint64_t AllocaTypeSize = IFI.DL->getTypeAllocSize(AllocaType);
752           uint64_t AllocaArraySize = AIArraySize->getLimitedValue();
753           assert(AllocaArraySize > 0 && "array size of AllocaInst is zero");
754           // Check that array size doesn't saturate uint64_t and doesn't
755           // overflow when it's multiplied by type size.
756           if (AllocaArraySize != ~0ULL &&
757               UINT64_MAX / AllocaArraySize >= AllocaTypeSize) {
758             AllocaSize = ConstantInt::get(Type::getInt64Ty(AI->getContext()),
759                                           AllocaArraySize * AllocaTypeSize);
760           }
761         }
762       }
763 
764       builder.CreateLifetimeStart(AI, AllocaSize);
765       for (ReturnInst *RI : Returns) {
766         // Don't insert llvm.lifetime.end calls between a musttail call and a
767         // return.  The return kills all local allocas.
768         if (InlinedMustTailCalls && getPrecedingMustTailCall(RI))
769           continue;
770         IRBuilder<>(RI).CreateLifetimeEnd(AI, AllocaSize);
771       }
772     }
773   }
774 
775   // If the inlined code contained dynamic alloca instructions, wrap the inlined
776   // code with llvm.stacksave/llvm.stackrestore intrinsics.
777   if (InlinedFunctionInfo.ContainsDynamicAllocas) {
778     Module *M = Caller->getParent();
779     // Get the two intrinsics we care about.
780     Function *StackSave = Intrinsic::getDeclaration(M, Intrinsic::stacksave);
781     Function *StackRestore=Intrinsic::getDeclaration(M,Intrinsic::stackrestore);
782 
783     // Insert the llvm.stacksave.
784     CallInst *SavedPtr = IRBuilder<>(FirstNewBlock, FirstNewBlock->begin())
785       .CreateCall(StackSave, "savedstack");
786 
787     // Insert a call to llvm.stackrestore before any return instructions in the
788     // inlined function.
789     for (ReturnInst *RI : Returns) {
790       // Don't insert llvm.stackrestore calls between a musttail call and a
791       // return.  The return will restore the stack pointer.
792       if (InlinedMustTailCalls && getPrecedingMustTailCall(RI))
793         continue;
794       IRBuilder<>(RI).CreateCall(StackRestore, SavedPtr);
795     }
796   }
797 
798   // If we are inlining for an invoke instruction, we must make sure to rewrite
799   // any call instructions into invoke instructions.
800   if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
801     HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo);
802 
803   // Handle any inlined musttail call sites.  In order for a new call site to be
804   // musttail, the source of the clone and the inlined call site must have been
805   // musttail.  Therefore it's safe to return without merging control into the
806   // phi below.
807   if (InlinedMustTailCalls) {
808     // Check if we need to bitcast the result of any musttail calls.
809     Type *NewRetTy = Caller->getReturnType();
810     bool NeedBitCast = !TheCall->use_empty() && TheCall->getType() != NewRetTy;
811 
812     // Handle the returns preceded by musttail calls separately.
813     SmallVector<ReturnInst *, 8> NormalReturns;
814     for (ReturnInst *RI : Returns) {
815       CallInst *ReturnedMustTail = getPrecedingMustTailCall(RI);
816       if (!ReturnedMustTail) {
817         NormalReturns.push_back(RI);
818         continue;
819       }
820       if (!NeedBitCast)
821         continue;
822 
823       // Delete the old return and any preceding bitcast.
824       BasicBlock *CurBB = RI->getParent();
825       auto *OldCast = dyn_cast_or_null<BitCastInst>(RI->getReturnValue());
826       RI->eraseFromParent();
827       if (OldCast)
828         OldCast->eraseFromParent();
829 
830       // Insert a new bitcast and return with the right type.
831       IRBuilder<> Builder(CurBB);
832       Builder.CreateRet(Builder.CreateBitCast(ReturnedMustTail, NewRetTy));
833     }
834 
835     // Leave behind the normal returns so we can merge control flow.
836     std::swap(Returns, NormalReturns);
837   }
838 
839   // If we cloned in _exactly one_ basic block, and if that block ends in a
840   // return instruction, we splice the body of the inlined callee directly into
841   // the calling basic block.
842   if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) {
843     // Move all of the instructions right before the call.
844     OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(),
845                                  FirstNewBlock->begin(), FirstNewBlock->end());
846     // Remove the cloned basic block.
847     Caller->getBasicBlockList().pop_back();
848 
849     // If the call site was an invoke instruction, add a branch to the normal
850     // destination.
851     if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
852       BranchInst *NewBr = BranchInst::Create(II->getNormalDest(), TheCall);
853       NewBr->setDebugLoc(Returns[0]->getDebugLoc());
854     }
855 
856     // If the return instruction returned a value, replace uses of the call with
857     // uses of the returned value.
858     if (!TheCall->use_empty()) {
859       ReturnInst *R = Returns[0];
860       if (TheCall == R->getReturnValue())
861         TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
862       else
863         TheCall->replaceAllUsesWith(R->getReturnValue());
864     }
865     // Since we are now done with the Call/Invoke, we can delete it.
866     TheCall->eraseFromParent();
867 
868     // Since we are now done with the return instruction, delete it also.
869     Returns[0]->eraseFromParent();
870 
871     // We are now done with the inlining.
872     return true;
873   }
874 
875   // Otherwise, we have the normal case, of more than one block to inline or
876   // multiple return sites.
877 
878   // We want to clone the entire callee function into the hole between the
879   // "starter" and "ender" blocks.  How we accomplish this depends on whether
880   // this is an invoke instruction or a call instruction.
881   BasicBlock *AfterCallBB;
882   BranchInst *CreatedBranchToNormalDest = nullptr;
883   if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
884 
885     // Add an unconditional branch to make this look like the CallInst case...
886     CreatedBranchToNormalDest = BranchInst::Create(II->getNormalDest(), TheCall);
887 
888     // Split the basic block.  This guarantees that no PHI nodes will have to be
889     // updated due to new incoming edges, and make the invoke case more
890     // symmetric to the call case.
891     AfterCallBB = OrigBB->splitBasicBlock(CreatedBranchToNormalDest,
892                                           CalledFunc->getName()+".exit");
893 
894   } else {  // It's a call
895     // If this is a call instruction, we need to split the basic block that
896     // the call lives in.
897     //
898     AfterCallBB = OrigBB->splitBasicBlock(TheCall,
899                                           CalledFunc->getName()+".exit");
900   }
901 
902   // Change the branch that used to go to AfterCallBB to branch to the first
903   // basic block of the inlined function.
904   //
905   TerminatorInst *Br = OrigBB->getTerminator();
906   assert(Br && Br->getOpcode() == Instruction::Br &&
907          "splitBasicBlock broken!");
908   Br->setOperand(0, FirstNewBlock);
909 
910 
911   // Now that the function is correct, make it a little bit nicer.  In
912   // particular, move the basic blocks inserted from the end of the function
913   // into the space made by splitting the source basic block.
914   Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(),
915                                      FirstNewBlock, Caller->end());
916 
917   // Handle all of the return instructions that we just cloned in, and eliminate
918   // any users of the original call/invoke instruction.
919   Type *RTy = CalledFunc->getReturnType();
920 
921   PHINode *PHI = nullptr;
922   if (Returns.size() > 1) {
923     // The PHI node should go at the front of the new basic block to merge all
924     // possible incoming values.
925     if (!TheCall->use_empty()) {
926       PHI = PHINode::Create(RTy, Returns.size(), TheCall->getName(),
927                             AfterCallBB->begin());
928       // Anything that used the result of the function call should now use the
929       // PHI node as their operand.
930       TheCall->replaceAllUsesWith(PHI);
931     }
932 
933     // Loop over all of the return instructions adding entries to the PHI node
934     // as appropriate.
935     if (PHI) {
936       for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
937         ReturnInst *RI = Returns[i];
938         assert(RI->getReturnValue()->getType() == PHI->getType() &&
939                "Ret value not consistent in function!");
940         PHI->addIncoming(RI->getReturnValue(), RI->getParent());
941       }
942     }
943 
944 
945     // Add a branch to the merge points and remove return instructions.
946     DebugLoc Loc;
947     for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
948       ReturnInst *RI = Returns[i];
949       BranchInst* BI = BranchInst::Create(AfterCallBB, RI);
950       Loc = RI->getDebugLoc();
951       BI->setDebugLoc(Loc);
952       RI->eraseFromParent();
953     }
954     // We need to set the debug location to *somewhere* inside the
955     // inlined function. The line number may be nonsensical, but the
956     // instruction will at least be associated with the right
957     // function.
958     if (CreatedBranchToNormalDest)
959       CreatedBranchToNormalDest->setDebugLoc(Loc);
960   } else if (!Returns.empty()) {
961     // Otherwise, if there is exactly one return value, just replace anything
962     // using the return value of the call with the computed value.
963     if (!TheCall->use_empty()) {
964       if (TheCall == Returns[0]->getReturnValue())
965         TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
966       else
967         TheCall->replaceAllUsesWith(Returns[0]->getReturnValue());
968     }
969 
970     // Update PHI nodes that use the ReturnBB to use the AfterCallBB.
971     BasicBlock *ReturnBB = Returns[0]->getParent();
972     ReturnBB->replaceAllUsesWith(AfterCallBB);
973 
974     // Splice the code from the return block into the block that it will return
975     // to, which contains the code that was after the call.
976     AfterCallBB->getInstList().splice(AfterCallBB->begin(),
977                                       ReturnBB->getInstList());
978 
979     if (CreatedBranchToNormalDest)
980       CreatedBranchToNormalDest->setDebugLoc(Returns[0]->getDebugLoc());
981 
982     // Delete the return instruction now and empty ReturnBB now.
983     Returns[0]->eraseFromParent();
984     ReturnBB->eraseFromParent();
985   } else if (!TheCall->use_empty()) {
986     // No returns, but something is using the return value of the call.  Just
987     // nuke the result.
988     TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
989   }
990 
991   // Since we are now done with the Call/Invoke, we can delete it.
992   TheCall->eraseFromParent();
993 
994   // If we inlined any musttail calls and the original return is now
995   // unreachable, delete it.  It can only contain a bitcast and ret.
996   if (InlinedMustTailCalls && pred_begin(AfterCallBB) == pred_end(AfterCallBB))
997     AfterCallBB->eraseFromParent();
998 
999   // We should always be able to fold the entry block of the function into the
1000   // single predecessor of the block...
1001   assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!");
1002   BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0);
1003 
1004   // Splice the code entry block into calling block, right before the
1005   // unconditional branch.
1006   CalleeEntry->replaceAllUsesWith(OrigBB);  // Update PHI nodes
1007   OrigBB->getInstList().splice(Br, CalleeEntry->getInstList());
1008 
1009   // Remove the unconditional branch.
1010   OrigBB->getInstList().erase(Br);
1011 
1012   // Now we can remove the CalleeEntry block, which is now empty.
1013   Caller->getBasicBlockList().erase(CalleeEntry);
1014 
1015   // If we inserted a phi node, check to see if it has a single value (e.g. all
1016   // the entries are the same or undef).  If so, remove the PHI so it doesn't
1017   // block other optimizations.
1018   if (PHI) {
1019     if (Value *V = SimplifyInstruction(PHI, IFI.DL)) {
1020       PHI->replaceAllUsesWith(V);
1021       PHI->eraseFromParent();
1022     }
1023   }
1024 
1025   return true;
1026 }
1027