1 //===-- Analysis.cpp - CodeGen LLVM IR Analysis Utilities -----------------===//
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 defines several CodeGen-specific LLVM IR analysis utilities.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/CodeGen/Analysis.h"
15 #include "llvm/Analysis/ValueTracking.h"
16 #include "llvm/CodeGen/MachineFunction.h"
17 #include "llvm/CodeGen/SelectionDAG.h"
18 #include "llvm/IR/DataLayout.h"
19 #include "llvm/IR/DerivedTypes.h"
20 #include "llvm/IR/Function.h"
21 #include "llvm/IR/Instructions.h"
22 #include "llvm/IR/IntrinsicInst.h"
23 #include "llvm/IR/LLVMContext.h"
24 #include "llvm/IR/Module.h"
25 #include "llvm/Support/ErrorHandling.h"
26 #include "llvm/Support/MathExtras.h"
27 #include "llvm/Target/TargetLowering.h"
28 #include "llvm/Target/TargetSubtargetInfo.h"
29 #include "llvm/Transforms/Utils/GlobalStatus.h"
33 /// Compute the linearized index of a member in a nested aggregate/struct/array
34 /// by recursing and accumulating CurIndex as long as there are indices in the
36 unsigned llvm::ComputeLinearIndex(Type *Ty,
37 const unsigned *Indices,
38 const unsigned *IndicesEnd,
40 // Base case: We're done.
41 if (Indices && Indices == IndicesEnd)
44 // Given a struct type, recursively traverse the elements.
45 if (StructType *STy = dyn_cast<StructType>(Ty)) {
46 for (StructType::element_iterator EB = STy->element_begin(),
48 EE = STy->element_end();
50 if (Indices && *Indices == unsigned(EI - EB))
51 return ComputeLinearIndex(*EI, Indices+1, IndicesEnd, CurIndex);
52 CurIndex = ComputeLinearIndex(*EI, nullptr, nullptr, CurIndex);
54 assert(!Indices && "Unexpected out of bound");
57 // Given an array type, recursively traverse the elements.
58 else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
59 Type *EltTy = ATy->getElementType();
60 unsigned NumElts = ATy->getNumElements();
61 // Compute the Linear offset when jumping one element of the array
62 unsigned EltLinearOffset = ComputeLinearIndex(EltTy, nullptr, nullptr, 0);
64 assert(*Indices < NumElts && "Unexpected out of bound");
65 // If the indice is inside the array, compute the index to the requested
66 // elt and recurse inside the element with the end of the indices list
67 CurIndex += EltLinearOffset* *Indices;
68 return ComputeLinearIndex(EltTy, Indices+1, IndicesEnd, CurIndex);
70 CurIndex += EltLinearOffset*NumElts;
73 // We haven't found the type we're looking for, so keep searching.
77 /// ComputeValueVTs - Given an LLVM IR type, compute a sequence of
78 /// EVTs that represent all the individual underlying
79 /// non-aggregate types that comprise it.
81 /// If Offsets is non-null, it points to a vector to be filled in
82 /// with the in-memory offsets of each of the individual values.
84 void llvm::ComputeValueVTs(const TargetLowering &TLI, Type *Ty,
85 SmallVectorImpl<EVT> &ValueVTs,
86 SmallVectorImpl<uint64_t> *Offsets,
87 uint64_t StartingOffset) {
88 // Given a struct type, recursively traverse the elements.
89 if (StructType *STy = dyn_cast<StructType>(Ty)) {
90 const StructLayout *SL = TLI.getDataLayout()->getStructLayout(STy);
91 for (StructType::element_iterator EB = STy->element_begin(),
93 EE = STy->element_end();
95 ComputeValueVTs(TLI, *EI, ValueVTs, Offsets,
96 StartingOffset + SL->getElementOffset(EI - EB));
99 // Given an array type, recursively traverse the elements.
100 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
101 Type *EltTy = ATy->getElementType();
102 uint64_t EltSize = TLI.getDataLayout()->getTypeAllocSize(EltTy);
103 for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i)
104 ComputeValueVTs(TLI, EltTy, ValueVTs, Offsets,
105 StartingOffset + i * EltSize);
108 // Interpret void as zero return values.
111 // Base case: we can get an EVT for this LLVM IR type.
112 ValueVTs.push_back(TLI.getValueType(Ty));
114 Offsets->push_back(StartingOffset);
117 /// ExtractTypeInfo - Returns the type info, possibly bitcast, encoded in V.
118 GlobalValue *llvm::ExtractTypeInfo(Value *V) {
119 V = V->stripPointerCasts();
120 GlobalValue *GV = dyn_cast<GlobalValue>(V);
121 GlobalVariable *Var = dyn_cast<GlobalVariable>(V);
123 if (Var && Var->getName() == "llvm.eh.catch.all.value") {
124 assert(Var->hasInitializer() &&
125 "The EH catch-all value must have an initializer");
126 Value *Init = Var->getInitializer();
127 GV = dyn_cast<GlobalValue>(Init);
128 if (!GV) V = cast<ConstantPointerNull>(Init);
131 assert((GV || isa<ConstantPointerNull>(V)) &&
132 "TypeInfo must be a global variable or NULL");
136 /// hasInlineAsmMemConstraint - Return true if the inline asm instruction being
137 /// processed uses a memory 'm' constraint.
139 llvm::hasInlineAsmMemConstraint(InlineAsm::ConstraintInfoVector &CInfos,
140 const TargetLowering &TLI) {
141 for (unsigned i = 0, e = CInfos.size(); i != e; ++i) {
142 InlineAsm::ConstraintInfo &CI = CInfos[i];
143 for (unsigned j = 0, ee = CI.Codes.size(); j != ee; ++j) {
144 TargetLowering::ConstraintType CType = TLI.getConstraintType(CI.Codes[j]);
145 if (CType == TargetLowering::C_Memory)
149 // Indirect operand accesses access memory.
157 /// getFCmpCondCode - Return the ISD condition code corresponding to
158 /// the given LLVM IR floating-point condition code. This includes
159 /// consideration of global floating-point math flags.
161 ISD::CondCode llvm::getFCmpCondCode(FCmpInst::Predicate Pred) {
163 case FCmpInst::FCMP_FALSE: return ISD::SETFALSE;
164 case FCmpInst::FCMP_OEQ: return ISD::SETOEQ;
165 case FCmpInst::FCMP_OGT: return ISD::SETOGT;
166 case FCmpInst::FCMP_OGE: return ISD::SETOGE;
167 case FCmpInst::FCMP_OLT: return ISD::SETOLT;
168 case FCmpInst::FCMP_OLE: return ISD::SETOLE;
169 case FCmpInst::FCMP_ONE: return ISD::SETONE;
170 case FCmpInst::FCMP_ORD: return ISD::SETO;
171 case FCmpInst::FCMP_UNO: return ISD::SETUO;
172 case FCmpInst::FCMP_UEQ: return ISD::SETUEQ;
173 case FCmpInst::FCMP_UGT: return ISD::SETUGT;
174 case FCmpInst::FCMP_UGE: return ISD::SETUGE;
175 case FCmpInst::FCMP_ULT: return ISD::SETULT;
176 case FCmpInst::FCMP_ULE: return ISD::SETULE;
177 case FCmpInst::FCMP_UNE: return ISD::SETUNE;
178 case FCmpInst::FCMP_TRUE: return ISD::SETTRUE;
179 default: llvm_unreachable("Invalid FCmp predicate opcode!");
183 ISD::CondCode llvm::getFCmpCodeWithoutNaN(ISD::CondCode CC) {
185 case ISD::SETOEQ: case ISD::SETUEQ: return ISD::SETEQ;
186 case ISD::SETONE: case ISD::SETUNE: return ISD::SETNE;
187 case ISD::SETOLT: case ISD::SETULT: return ISD::SETLT;
188 case ISD::SETOLE: case ISD::SETULE: return ISD::SETLE;
189 case ISD::SETOGT: case ISD::SETUGT: return ISD::SETGT;
190 case ISD::SETOGE: case ISD::SETUGE: return ISD::SETGE;
195 /// getICmpCondCode - Return the ISD condition code corresponding to
196 /// the given LLVM IR integer condition code.
198 ISD::CondCode llvm::getICmpCondCode(ICmpInst::Predicate Pred) {
200 case ICmpInst::ICMP_EQ: return ISD::SETEQ;
201 case ICmpInst::ICMP_NE: return ISD::SETNE;
202 case ICmpInst::ICMP_SLE: return ISD::SETLE;
203 case ICmpInst::ICMP_ULE: return ISD::SETULE;
204 case ICmpInst::ICMP_SGE: return ISD::SETGE;
205 case ICmpInst::ICMP_UGE: return ISD::SETUGE;
206 case ICmpInst::ICMP_SLT: return ISD::SETLT;
207 case ICmpInst::ICMP_ULT: return ISD::SETULT;
208 case ICmpInst::ICMP_SGT: return ISD::SETGT;
209 case ICmpInst::ICMP_UGT: return ISD::SETUGT;
211 llvm_unreachable("Invalid ICmp predicate opcode!");
215 static bool isNoopBitcast(Type *T1, Type *T2,
216 const TargetLoweringBase& TLI) {
217 return T1 == T2 || (T1->isPointerTy() && T2->isPointerTy()) ||
218 (isa<VectorType>(T1) && isa<VectorType>(T2) &&
219 TLI.isTypeLegal(EVT::getEVT(T1)) && TLI.isTypeLegal(EVT::getEVT(T2)));
222 /// Look through operations that will be free to find the earliest source of
225 /// @param ValLoc If V has aggegate type, we will be interested in a particular
226 /// scalar component. This records its address; the reverse of this list gives a
227 /// sequence of indices appropriate for an extractvalue to locate the important
228 /// value. This value is updated during the function and on exit will indicate
229 /// similar information for the Value returned.
231 /// @param DataBits If this function looks through truncate instructions, this
232 /// will record the smallest size attained.
233 static const Value *getNoopInput(const Value *V,
234 SmallVectorImpl<unsigned> &ValLoc,
236 const TargetLoweringBase &TLI) {
238 // Try to look through V1; if V1 is not an instruction, it can't be looked
240 const Instruction *I = dyn_cast<Instruction>(V);
241 if (!I || I->getNumOperands() == 0) return V;
242 const Value *NoopInput = nullptr;
244 Value *Op = I->getOperand(0);
245 if (isa<BitCastInst>(I)) {
246 // Look through truly no-op bitcasts.
247 if (isNoopBitcast(Op->getType(), I->getType(), TLI))
249 } else if (isa<GetElementPtrInst>(I)) {
250 // Look through getelementptr
251 if (cast<GetElementPtrInst>(I)->hasAllZeroIndices())
253 } else if (isa<IntToPtrInst>(I)) {
254 // Look through inttoptr.
255 // Make sure this isn't a truncating or extending cast. We could
256 // support this eventually, but don't bother for now.
257 if (!isa<VectorType>(I->getType()) &&
258 TLI.getPointerTy().getSizeInBits() ==
259 cast<IntegerType>(Op->getType())->getBitWidth())
261 } else if (isa<PtrToIntInst>(I)) {
262 // Look through ptrtoint.
263 // Make sure this isn't a truncating or extending cast. We could
264 // support this eventually, but don't bother for now.
265 if (!isa<VectorType>(I->getType()) &&
266 TLI.getPointerTy().getSizeInBits() ==
267 cast<IntegerType>(I->getType())->getBitWidth())
269 } else if (isa<TruncInst>(I) &&
270 TLI.allowTruncateForTailCall(Op->getType(), I->getType())) {
271 DataBits = std::min(DataBits, I->getType()->getPrimitiveSizeInBits());
273 } else if (isa<CallInst>(I)) {
274 // Look through call (skipping callee)
275 for (User::const_op_iterator i = I->op_begin(), e = I->op_end() - 1;
277 unsigned attrInd = i - I->op_begin() + 1;
278 if (cast<CallInst>(I)->paramHasAttr(attrInd, Attribute::Returned) &&
279 isNoopBitcast((*i)->getType(), I->getType(), TLI)) {
284 } else if (isa<InvokeInst>(I)) {
285 // Look through invoke (skipping BB, BB, Callee)
286 for (User::const_op_iterator i = I->op_begin(), e = I->op_end() - 3;
288 unsigned attrInd = i - I->op_begin() + 1;
289 if (cast<InvokeInst>(I)->paramHasAttr(attrInd, Attribute::Returned) &&
290 isNoopBitcast((*i)->getType(), I->getType(), TLI)) {
295 } else if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(V)) {
296 // Value may come from either the aggregate or the scalar
297 ArrayRef<unsigned> InsertLoc = IVI->getIndices();
298 if (std::equal(InsertLoc.rbegin(), InsertLoc.rend(),
300 // The type being inserted is a nested sub-type of the aggregate; we
301 // have to remove those initial indices to get the location we're
302 // interested in for the operand.
303 ValLoc.resize(ValLoc.size() - InsertLoc.size());
304 NoopInput = IVI->getInsertedValueOperand();
306 // The struct we're inserting into has the value we're interested in, no
307 // change of address.
310 } else if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(V)) {
311 // The part we're interested in will inevitably be some sub-section of the
312 // previous aggregate. Combine the two paths to obtain the true address of
314 ArrayRef<unsigned> ExtractLoc = EVI->getIndices();
315 std::copy(ExtractLoc.rbegin(), ExtractLoc.rend(),
316 std::back_inserter(ValLoc));
319 // Terminate if we couldn't find anything to look through.
327 /// Return true if this scalar return value only has bits discarded on its path
328 /// from the "tail call" to the "ret". This includes the obvious noop
329 /// instructions handled by getNoopInput above as well as free truncations (or
330 /// extensions prior to the call).
331 static bool slotOnlyDiscardsData(const Value *RetVal, const Value *CallVal,
332 SmallVectorImpl<unsigned> &RetIndices,
333 SmallVectorImpl<unsigned> &CallIndices,
334 bool AllowDifferingSizes,
335 const TargetLoweringBase &TLI) {
337 // Trace the sub-value needed by the return value as far back up the graph as
338 // possible, in the hope that it will intersect with the value produced by the
339 // call. In the simple case with no "returned" attribute, the hope is actually
340 // that we end up back at the tail call instruction itself.
341 unsigned BitsRequired = UINT_MAX;
342 RetVal = getNoopInput(RetVal, RetIndices, BitsRequired, TLI);
344 // If this slot in the value returned is undef, it doesn't matter what the
345 // call puts there, it'll be fine.
346 if (isa<UndefValue>(RetVal))
349 // Now do a similar search up through the graph to find where the value
350 // actually returned by the "tail call" comes from. In the simple case without
351 // a "returned" attribute, the search will be blocked immediately and the loop
353 unsigned BitsProvided = UINT_MAX;
354 CallVal = getNoopInput(CallVal, CallIndices, BitsProvided, TLI);
356 // There's no hope if we can't actually trace them to (the same part of!) the
358 if (CallVal != RetVal || CallIndices != RetIndices)
361 // However, intervening truncates may have made the call non-tail. Make sure
362 // all the bits that are needed by the "ret" have been provided by the "tail
363 // call". FIXME: with sufficiently cunning bit-tracking, we could look through
365 if (BitsProvided < BitsRequired ||
366 (!AllowDifferingSizes && BitsProvided != BitsRequired))
372 /// For an aggregate type, determine whether a given index is within bounds or
374 static bool indexReallyValid(CompositeType *T, unsigned Idx) {
375 if (ArrayType *AT = dyn_cast<ArrayType>(T))
376 return Idx < AT->getNumElements();
378 return Idx < cast<StructType>(T)->getNumElements();
381 /// Move the given iterators to the next leaf type in depth first traversal.
383 /// Performs a depth-first traversal of the type as specified by its arguments,
384 /// stopping at the next leaf node (which may be a legitimate scalar type or an
385 /// empty struct or array).
387 /// @param SubTypes List of the partial components making up the type from
388 /// outermost to innermost non-empty aggregate. The element currently
389 /// represented is SubTypes.back()->getTypeAtIndex(Path.back() - 1).
391 /// @param Path Set of extractvalue indices leading from the outermost type
392 /// (SubTypes[0]) to the leaf node currently represented.
394 /// @returns true if a new type was found, false otherwise. Calling this
395 /// function again on a finished iterator will repeatedly return
396 /// false. SubTypes.back()->getTypeAtIndex(Path.back()) is either an empty
397 /// aggregate or a non-aggregate
398 static bool advanceToNextLeafType(SmallVectorImpl<CompositeType *> &SubTypes,
399 SmallVectorImpl<unsigned> &Path) {
400 // First march back up the tree until we can successfully increment one of the
401 // coordinates in Path.
402 while (!Path.empty() && !indexReallyValid(SubTypes.back(), Path.back() + 1)) {
407 // If we reached the top, then the iterator is done.
411 // We know there's *some* valid leaf now, so march back down the tree picking
412 // out the left-most element at each node.
414 Type *DeeperType = SubTypes.back()->getTypeAtIndex(Path.back());
415 while (DeeperType->isAggregateType()) {
416 CompositeType *CT = cast<CompositeType>(DeeperType);
417 if (!indexReallyValid(CT, 0))
420 SubTypes.push_back(CT);
423 DeeperType = CT->getTypeAtIndex(0U);
429 /// Find the first non-empty, scalar-like type in Next and setup the iterator
432 /// Assuming Next is an aggregate of some kind, this function will traverse the
433 /// tree from left to right (i.e. depth-first) looking for the first
434 /// non-aggregate type which will play a role in function return.
436 /// For example, if Next was {[0 x i64], {{}, i32, {}}, i32} then we would setup
437 /// Path as [1, 1] and SubTypes as [Next, {{}, i32, {}}] to represent the first
438 /// i32 in that type.
439 static bool firstRealType(Type *Next,
440 SmallVectorImpl<CompositeType *> &SubTypes,
441 SmallVectorImpl<unsigned> &Path) {
442 // First initialise the iterator components to the first "leaf" node
443 // (i.e. node with no valid sub-type at any index, so {} does count as a leaf
444 // despite nominally being an aggregate).
445 while (Next->isAggregateType() &&
446 indexReallyValid(cast<CompositeType>(Next), 0)) {
447 SubTypes.push_back(cast<CompositeType>(Next));
449 Next = cast<CompositeType>(Next)->getTypeAtIndex(0U);
452 // If there's no Path now, Next was originally scalar already (or empty
453 // leaf). We're done.
457 // Otherwise, use normal iteration to keep looking through the tree until we
458 // find a non-aggregate type.
459 while (SubTypes.back()->getTypeAtIndex(Path.back())->isAggregateType()) {
460 if (!advanceToNextLeafType(SubTypes, Path))
467 /// Set the iterator data-structures to the next non-empty, non-aggregate
469 static bool nextRealType(SmallVectorImpl<CompositeType *> &SubTypes,
470 SmallVectorImpl<unsigned> &Path) {
472 if (!advanceToNextLeafType(SubTypes, Path))
475 assert(!Path.empty() && "found a leaf but didn't set the path?");
476 } while (SubTypes.back()->getTypeAtIndex(Path.back())->isAggregateType());
482 /// Test if the given instruction is in a position to be optimized
483 /// with a tail-call. This roughly means that it's in a block with
484 /// a return and there's nothing that needs to be scheduled
485 /// between it and the return.
487 /// This function only tests target-independent requirements.
488 bool llvm::isInTailCallPosition(ImmutableCallSite CS, const TargetMachine &TM) {
489 const Instruction *I = CS.getInstruction();
490 const BasicBlock *ExitBB = I->getParent();
491 const TerminatorInst *Term = ExitBB->getTerminator();
492 const ReturnInst *Ret = dyn_cast<ReturnInst>(Term);
494 // The block must end in a return statement or unreachable.
496 // FIXME: Decline tailcall if it's not guaranteed and if the block ends in
497 // an unreachable, for now. The way tailcall optimization is currently
498 // implemented means it will add an epilogue followed by a jump. That is
499 // not profitable. Also, if the callee is a special function (e.g.
500 // longjmp on x86), it can end up causing miscompilation that has not
501 // been fully understood.
503 (!TM.Options.GuaranteedTailCallOpt || !isa<UnreachableInst>(Term)))
506 // If I will have a chain, make sure no other instruction that will have a
507 // chain interposes between I and the return.
508 if (I->mayHaveSideEffects() || I->mayReadFromMemory() ||
509 !isSafeToSpeculativelyExecute(I))
510 for (BasicBlock::const_iterator BBI = std::prev(ExitBB->end(), 2);; --BBI) {
513 // Debug info intrinsics do not get in the way of tail call optimization.
514 if (isa<DbgInfoIntrinsic>(BBI))
516 if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() ||
517 !isSafeToSpeculativelyExecute(BBI))
521 const Function *F = ExitBB->getParent();
522 return returnTypeIsEligibleForTailCall(
523 F, I, Ret, *TM.getSubtargetImpl(*F)->getTargetLowering());
526 bool llvm::returnTypeIsEligibleForTailCall(const Function *F,
527 const Instruction *I,
528 const ReturnInst *Ret,
529 const TargetLoweringBase &TLI) {
530 // If the block ends with a void return or unreachable, it doesn't matter
531 // what the call's return type is.
532 if (!Ret || Ret->getNumOperands() == 0) return true;
534 // If the return value is undef, it doesn't matter what the call's
536 if (isa<UndefValue>(Ret->getOperand(0))) return true;
538 // Make sure the attributes attached to each return are compatible.
539 AttrBuilder CallerAttrs(F->getAttributes(),
540 AttributeSet::ReturnIndex);
541 AttrBuilder CalleeAttrs(cast<CallInst>(I)->getAttributes(),
542 AttributeSet::ReturnIndex);
544 // Noalias is completely benign as far as calling convention goes, it
545 // shouldn't affect whether the call is a tail call.
546 CallerAttrs = CallerAttrs.removeAttribute(Attribute::NoAlias);
547 CalleeAttrs = CalleeAttrs.removeAttribute(Attribute::NoAlias);
549 bool AllowDifferingSizes = true;
550 if (CallerAttrs.contains(Attribute::ZExt)) {
551 if (!CalleeAttrs.contains(Attribute::ZExt))
554 AllowDifferingSizes = false;
555 CallerAttrs.removeAttribute(Attribute::ZExt);
556 CalleeAttrs.removeAttribute(Attribute::ZExt);
557 } else if (CallerAttrs.contains(Attribute::SExt)) {
558 if (!CalleeAttrs.contains(Attribute::SExt))
561 AllowDifferingSizes = false;
562 CallerAttrs.removeAttribute(Attribute::SExt);
563 CalleeAttrs.removeAttribute(Attribute::SExt);
566 // If they're still different, there's some facet we don't understand
567 // (currently only "inreg", but in future who knows). It may be OK but the
568 // only safe option is to reject the tail call.
569 if (CallerAttrs != CalleeAttrs)
572 const Value *RetVal = Ret->getOperand(0), *CallVal = I;
573 SmallVector<unsigned, 4> RetPath, CallPath;
574 SmallVector<CompositeType *, 4> RetSubTypes, CallSubTypes;
576 bool RetEmpty = !firstRealType(RetVal->getType(), RetSubTypes, RetPath);
577 bool CallEmpty = !firstRealType(CallVal->getType(), CallSubTypes, CallPath);
579 // Nothing's actually returned, it doesn't matter what the callee put there
580 // it's a valid tail call.
584 // Iterate pairwise through each of the value types making up the tail call
585 // and the corresponding return. For each one we want to know whether it's
586 // essentially going directly from the tail call to the ret, via operations
587 // that end up not generating any code.
589 // We allow a certain amount of covariance here. For example it's permitted
590 // for the tail call to define more bits than the ret actually cares about
591 // (e.g. via a truncate).
594 // We've exhausted the values produced by the tail call instruction, the
595 // rest are essentially undef. The type doesn't really matter, but we need
597 Type *SlotType = RetSubTypes.back()->getTypeAtIndex(RetPath.back());
598 CallVal = UndefValue::get(SlotType);
601 // The manipulations performed when we're looking through an insertvalue or
602 // an extractvalue would happen at the front of the RetPath list, so since
603 // we have to copy it anyway it's more efficient to create a reversed copy.
605 SmallVector<unsigned, 4> TmpRetPath, TmpCallPath;
606 copy(RetPath.rbegin(), RetPath.rend(), std::back_inserter(TmpRetPath));
607 copy(CallPath.rbegin(), CallPath.rend(), std::back_inserter(TmpCallPath));
609 // Finally, we can check whether the value produced by the tail call at this
610 // index is compatible with the value we return.
611 if (!slotOnlyDiscardsData(RetVal, CallVal, TmpRetPath, TmpCallPath,
612 AllowDifferingSizes, TLI))
615 CallEmpty = !nextRealType(CallSubTypes, CallPath);
616 } while(nextRealType(RetSubTypes, RetPath));
621 bool llvm::canBeOmittedFromSymbolTable(const GlobalValue *GV) {
622 if (!GV->hasLinkOnceODRLinkage())
625 if (GV->hasUnnamedAddr())
628 // If it is a non constant variable, it needs to be uniqued across shared
630 if (const GlobalVariable *Var = dyn_cast<GlobalVariable>(GV)) {
631 if (!Var->isConstant())
635 // An alias can point to a variable. We could try to resolve the alias to
636 // decide, but for now just don't hide them.
637 if (isa<GlobalAlias>(GV))
641 if (GlobalStatus::analyzeGlobal(GV, GS))
644 return !GS.IsCompared;