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, const DataLayout &DL,
85 Type *Ty, 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 = DL.getStructLayout(STy);
91 for (StructType::element_iterator EB = STy->element_begin(),
93 EE = STy->element_end();
95 ComputeValueVTs(TLI, DL, *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 = DL.getTypeAllocSize(EltTy);
103 for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i)
104 ComputeValueVTs(TLI, DL, 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(DL, 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,
237 const DataLayout &DL) {
239 // Try to look through V1; if V1 is not an instruction, it can't be looked
241 const Instruction *I = dyn_cast<Instruction>(V);
242 if (!I || I->getNumOperands() == 0) return V;
243 const Value *NoopInput = nullptr;
245 Value *Op = I->getOperand(0);
246 if (isa<BitCastInst>(I)) {
247 // Look through truly no-op bitcasts.
248 if (isNoopBitcast(Op->getType(), I->getType(), TLI))
250 } else if (isa<GetElementPtrInst>(I)) {
251 // Look through getelementptr
252 if (cast<GetElementPtrInst>(I)->hasAllZeroIndices())
254 } else if (isa<IntToPtrInst>(I)) {
255 // Look through inttoptr.
256 // Make sure this isn't a truncating or extending cast. We could
257 // support this eventually, but don't bother for now.
258 if (!isa<VectorType>(I->getType()) &&
259 DL.getPointerSizeInBits() ==
260 cast<IntegerType>(Op->getType())->getBitWidth())
262 } else if (isa<PtrToIntInst>(I)) {
263 // Look through ptrtoint.
264 // Make sure this isn't a truncating or extending cast. We could
265 // support this eventually, but don't bother for now.
266 if (!isa<VectorType>(I->getType()) &&
267 DL.getPointerSizeInBits() ==
268 cast<IntegerType>(I->getType())->getBitWidth())
270 } else if (isa<TruncInst>(I) &&
271 TLI.allowTruncateForTailCall(Op->getType(), I->getType())) {
272 DataBits = std::min(DataBits, I->getType()->getPrimitiveSizeInBits());
274 } else if (isa<CallInst>(I)) {
275 // Look through call (skipping callee)
276 for (User::const_op_iterator i = I->op_begin(), e = I->op_end() - 1;
278 unsigned attrInd = i - I->op_begin() + 1;
279 if (cast<CallInst>(I)->paramHasAttr(attrInd, Attribute::Returned) &&
280 isNoopBitcast((*i)->getType(), I->getType(), TLI)) {
285 } else if (isa<InvokeInst>(I)) {
286 // Look through invoke (skipping BB, BB, Callee)
287 for (User::const_op_iterator i = I->op_begin(), e = I->op_end() - 3;
289 unsigned attrInd = i - I->op_begin() + 1;
290 if (cast<InvokeInst>(I)->paramHasAttr(attrInd, Attribute::Returned) &&
291 isNoopBitcast((*i)->getType(), I->getType(), TLI)) {
296 } else if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(V)) {
297 // Value may come from either the aggregate or the scalar
298 ArrayRef<unsigned> InsertLoc = IVI->getIndices();
299 if (ValLoc.size() >= InsertLoc.size() &&
300 std::equal(InsertLoc.begin(), InsertLoc.end(), ValLoc.rbegin())) {
301 // The type being inserted is a nested sub-type of the aggregate; we
302 // have to remove those initial indices to get the location we're
303 // interested in for the operand.
304 ValLoc.resize(ValLoc.size() - InsertLoc.size());
305 NoopInput = IVI->getInsertedValueOperand();
307 // The struct we're inserting into has the value we're interested in, no
308 // change of address.
311 } else if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(V)) {
312 // The part we're interested in will inevitably be some sub-section of the
313 // previous aggregate. Combine the two paths to obtain the true address of
315 ArrayRef<unsigned> ExtractLoc = EVI->getIndices();
316 ValLoc.append(ExtractLoc.rbegin(), ExtractLoc.rend());
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,
336 const DataLayout &DL) {
338 // Trace the sub-value needed by the return value as far back up the graph as
339 // possible, in the hope that it will intersect with the value produced by the
340 // call. In the simple case with no "returned" attribute, the hope is actually
341 // that we end up back at the tail call instruction itself.
342 unsigned BitsRequired = UINT_MAX;
343 RetVal = getNoopInput(RetVal, RetIndices, BitsRequired, TLI, DL);
345 // If this slot in the value returned is undef, it doesn't matter what the
346 // call puts there, it'll be fine.
347 if (isa<UndefValue>(RetVal))
350 // Now do a similar search up through the graph to find where the value
351 // actually returned by the "tail call" comes from. In the simple case without
352 // a "returned" attribute, the search will be blocked immediately and the loop
354 unsigned BitsProvided = UINT_MAX;
355 CallVal = getNoopInput(CallVal, CallIndices, BitsProvided, TLI, DL);
357 // There's no hope if we can't actually trace them to (the same part of!) the
359 if (CallVal != RetVal || CallIndices != RetIndices)
362 // However, intervening truncates may have made the call non-tail. Make sure
363 // all the bits that are needed by the "ret" have been provided by the "tail
364 // call". FIXME: with sufficiently cunning bit-tracking, we could look through
366 if (BitsProvided < BitsRequired ||
367 (!AllowDifferingSizes && BitsProvided != BitsRequired))
373 /// For an aggregate type, determine whether a given index is within bounds or
375 static bool indexReallyValid(CompositeType *T, unsigned Idx) {
376 if (ArrayType *AT = dyn_cast<ArrayType>(T))
377 return Idx < AT->getNumElements();
379 return Idx < cast<StructType>(T)->getNumElements();
382 /// Move the given iterators to the next leaf type in depth first traversal.
384 /// Performs a depth-first traversal of the type as specified by its arguments,
385 /// stopping at the next leaf node (which may be a legitimate scalar type or an
386 /// empty struct or array).
388 /// @param SubTypes List of the partial components making up the type from
389 /// outermost to innermost non-empty aggregate. The element currently
390 /// represented is SubTypes.back()->getTypeAtIndex(Path.back() - 1).
392 /// @param Path Set of extractvalue indices leading from the outermost type
393 /// (SubTypes[0]) to the leaf node currently represented.
395 /// @returns true if a new type was found, false otherwise. Calling this
396 /// function again on a finished iterator will repeatedly return
397 /// false. SubTypes.back()->getTypeAtIndex(Path.back()) is either an empty
398 /// aggregate or a non-aggregate
399 static bool advanceToNextLeafType(SmallVectorImpl<CompositeType *> &SubTypes,
400 SmallVectorImpl<unsigned> &Path) {
401 // First march back up the tree until we can successfully increment one of the
402 // coordinates in Path.
403 while (!Path.empty() && !indexReallyValid(SubTypes.back(), Path.back() + 1)) {
408 // If we reached the top, then the iterator is done.
412 // We know there's *some* valid leaf now, so march back down the tree picking
413 // out the left-most element at each node.
415 Type *DeeperType = SubTypes.back()->getTypeAtIndex(Path.back());
416 while (DeeperType->isAggregateType()) {
417 CompositeType *CT = cast<CompositeType>(DeeperType);
418 if (!indexReallyValid(CT, 0))
421 SubTypes.push_back(CT);
424 DeeperType = CT->getTypeAtIndex(0U);
430 /// Find the first non-empty, scalar-like type in Next and setup the iterator
433 /// Assuming Next is an aggregate of some kind, this function will traverse the
434 /// tree from left to right (i.e. depth-first) looking for the first
435 /// non-aggregate type which will play a role in function return.
437 /// For example, if Next was {[0 x i64], {{}, i32, {}}, i32} then we would setup
438 /// Path as [1, 1] and SubTypes as [Next, {{}, i32, {}}] to represent the first
439 /// i32 in that type.
440 static bool firstRealType(Type *Next,
441 SmallVectorImpl<CompositeType *> &SubTypes,
442 SmallVectorImpl<unsigned> &Path) {
443 // First initialise the iterator components to the first "leaf" node
444 // (i.e. node with no valid sub-type at any index, so {} does count as a leaf
445 // despite nominally being an aggregate).
446 while (Next->isAggregateType() &&
447 indexReallyValid(cast<CompositeType>(Next), 0)) {
448 SubTypes.push_back(cast<CompositeType>(Next));
450 Next = cast<CompositeType>(Next)->getTypeAtIndex(0U);
453 // If there's no Path now, Next was originally scalar already (or empty
454 // leaf). We're done.
458 // Otherwise, use normal iteration to keep looking through the tree until we
459 // find a non-aggregate type.
460 while (SubTypes.back()->getTypeAtIndex(Path.back())->isAggregateType()) {
461 if (!advanceToNextLeafType(SubTypes, Path))
468 /// Set the iterator data-structures to the next non-empty, non-aggregate
470 static bool nextRealType(SmallVectorImpl<CompositeType *> &SubTypes,
471 SmallVectorImpl<unsigned> &Path) {
473 if (!advanceToNextLeafType(SubTypes, Path))
476 assert(!Path.empty() && "found a leaf but didn't set the path?");
477 } while (SubTypes.back()->getTypeAtIndex(Path.back())->isAggregateType());
483 /// Test if the given instruction is in a position to be optimized
484 /// with a tail-call. This roughly means that it's in a block with
485 /// a return and there's nothing that needs to be scheduled
486 /// between it and the return.
488 /// This function only tests target-independent requirements.
489 bool llvm::isInTailCallPosition(ImmutableCallSite CS, const TargetMachine &TM) {
490 const Instruction *I = CS.getInstruction();
491 const BasicBlock *ExitBB = I->getParent();
492 const TerminatorInst *Term = ExitBB->getTerminator();
493 const ReturnInst *Ret = dyn_cast<ReturnInst>(Term);
495 // The block must end in a return statement or unreachable.
497 // FIXME: Decline tailcall if it's not guaranteed and if the block ends in
498 // an unreachable, for now. The way tailcall optimization is currently
499 // implemented means it will add an epilogue followed by a jump. That is
500 // not profitable. Also, if the callee is a special function (e.g.
501 // longjmp on x86), it can end up causing miscompilation that has not
502 // been fully understood.
504 (!TM.Options.GuaranteedTailCallOpt || !isa<UnreachableInst>(Term)))
507 // If I will have a chain, make sure no other instruction that will have a
508 // chain interposes between I and the return.
509 if (I->mayHaveSideEffects() || I->mayReadFromMemory() ||
510 !isSafeToSpeculativelyExecute(I))
511 for (BasicBlock::const_iterator BBI = std::prev(ExitBB->end(), 2);; --BBI) {
514 // Debug info intrinsics do not get in the way of tail call optimization.
515 if (isa<DbgInfoIntrinsic>(BBI))
517 if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() ||
518 !isSafeToSpeculativelyExecute(BBI))
522 const Function *F = ExitBB->getParent();
523 return returnTypeIsEligibleForTailCall(
524 F, I, Ret, *TM.getSubtargetImpl(*F)->getTargetLowering());
527 bool llvm::returnTypeIsEligibleForTailCall(const Function *F,
528 const Instruction *I,
529 const ReturnInst *Ret,
530 const TargetLoweringBase &TLI) {
531 // If the block ends with a void return or unreachable, it doesn't matter
532 // what the call's return type is.
533 if (!Ret || Ret->getNumOperands() == 0) return true;
535 // If the return value is undef, it doesn't matter what the call's
537 if (isa<UndefValue>(Ret->getOperand(0))) return true;
539 // Make sure the attributes attached to each return are compatible.
540 AttrBuilder CallerAttrs(F->getAttributes(),
541 AttributeSet::ReturnIndex);
542 AttrBuilder CalleeAttrs(cast<CallInst>(I)->getAttributes(),
543 AttributeSet::ReturnIndex);
545 // Noalias is completely benign as far as calling convention goes, it
546 // shouldn't affect whether the call is a tail call.
547 CallerAttrs = CallerAttrs.removeAttribute(Attribute::NoAlias);
548 CalleeAttrs = CalleeAttrs.removeAttribute(Attribute::NoAlias);
550 bool AllowDifferingSizes = true;
551 if (CallerAttrs.contains(Attribute::ZExt)) {
552 if (!CalleeAttrs.contains(Attribute::ZExt))
555 AllowDifferingSizes = false;
556 CallerAttrs.removeAttribute(Attribute::ZExt);
557 CalleeAttrs.removeAttribute(Attribute::ZExt);
558 } else if (CallerAttrs.contains(Attribute::SExt)) {
559 if (!CalleeAttrs.contains(Attribute::SExt))
562 AllowDifferingSizes = false;
563 CallerAttrs.removeAttribute(Attribute::SExt);
564 CalleeAttrs.removeAttribute(Attribute::SExt);
567 // If they're still different, there's some facet we don't understand
568 // (currently only "inreg", but in future who knows). It may be OK but the
569 // only safe option is to reject the tail call.
570 if (CallerAttrs != CalleeAttrs)
573 const Value *RetVal = Ret->getOperand(0), *CallVal = I;
574 SmallVector<unsigned, 4> RetPath, CallPath;
575 SmallVector<CompositeType *, 4> RetSubTypes, CallSubTypes;
577 bool RetEmpty = !firstRealType(RetVal->getType(), RetSubTypes, RetPath);
578 bool CallEmpty = !firstRealType(CallVal->getType(), CallSubTypes, CallPath);
580 // Nothing's actually returned, it doesn't matter what the callee put there
581 // it's a valid tail call.
585 // Iterate pairwise through each of the value types making up the tail call
586 // and the corresponding return. For each one we want to know whether it's
587 // essentially going directly from the tail call to the ret, via operations
588 // that end up not generating any code.
590 // We allow a certain amount of covariance here. For example it's permitted
591 // for the tail call to define more bits than the ret actually cares about
592 // (e.g. via a truncate).
595 // We've exhausted the values produced by the tail call instruction, the
596 // rest are essentially undef. The type doesn't really matter, but we need
598 Type *SlotType = RetSubTypes.back()->getTypeAtIndex(RetPath.back());
599 CallVal = UndefValue::get(SlotType);
602 // The manipulations performed when we're looking through an insertvalue or
603 // an extractvalue would happen at the front of the RetPath list, so since
604 // we have to copy it anyway it's more efficient to create a reversed copy.
605 SmallVector<unsigned, 4> TmpRetPath(RetPath.rbegin(), RetPath.rend());
606 SmallVector<unsigned, 4> TmpCallPath(CallPath.rbegin(), CallPath.rend());
608 // Finally, we can check whether the value produced by the tail call at this
609 // index is compatible with the value we return.
610 if (!slotOnlyDiscardsData(RetVal, CallVal, TmpRetPath, TmpCallPath,
611 AllowDifferingSizes, TLI,
612 F->getParent()->getDataLayout()))
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;