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 /// ComputeLinearIndex - Given an LLVM IR aggregate type and a sequence
34 /// of insertvalue or extractvalue indices that identify a member, return
35 /// the linearized index of the start of the member.
37 unsigned llvm::ComputeLinearIndex(Type *Ty,
38 const unsigned *Indices,
39 const unsigned *IndicesEnd,
41 // Base case: We're done.
42 if (Indices && Indices == IndicesEnd)
45 // Given a struct type, recursively traverse the elements.
46 if (StructType *STy = dyn_cast<StructType>(Ty)) {
47 for (StructType::element_iterator EB = STy->element_begin(),
49 EE = STy->element_end();
51 if (Indices && *Indices == unsigned(EI - EB))
52 return ComputeLinearIndex(*EI, Indices+1, IndicesEnd, CurIndex);
53 CurIndex = ComputeLinearIndex(*EI, nullptr, nullptr, CurIndex);
57 // Given an array type, recursively traverse the elements.
58 else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
59 Type *EltTy = ATy->getElementType();
60 for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i) {
61 if (Indices && *Indices == i)
62 return ComputeLinearIndex(EltTy, Indices+1, IndicesEnd, CurIndex);
63 CurIndex = ComputeLinearIndex(EltTy, nullptr, nullptr, CurIndex);
67 // We haven't found the type we're looking for, so keep searching.
71 /// ComputeValueVTs - Given an LLVM IR type, compute a sequence of
72 /// EVTs that represent all the individual underlying
73 /// non-aggregate types that comprise it.
75 /// If Offsets is non-null, it points to a vector to be filled in
76 /// with the in-memory offsets of each of the individual values.
78 void llvm::ComputeValueVTs(const TargetLowering &TLI, Type *Ty,
79 SmallVectorImpl<EVT> &ValueVTs,
80 SmallVectorImpl<uint64_t> *Offsets,
81 uint64_t StartingOffset) {
82 // Given a struct type, recursively traverse the elements.
83 if (StructType *STy = dyn_cast<StructType>(Ty)) {
84 const StructLayout *SL = TLI.getDataLayout()->getStructLayout(STy);
85 for (StructType::element_iterator EB = STy->element_begin(),
87 EE = STy->element_end();
89 ComputeValueVTs(TLI, *EI, ValueVTs, Offsets,
90 StartingOffset + SL->getElementOffset(EI - EB));
93 // Given an array type, recursively traverse the elements.
94 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
95 Type *EltTy = ATy->getElementType();
96 uint64_t EltSize = TLI.getDataLayout()->getTypeAllocSize(EltTy);
97 for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i)
98 ComputeValueVTs(TLI, EltTy, ValueVTs, Offsets,
99 StartingOffset + i * EltSize);
102 // Interpret void as zero return values.
105 // Base case: we can get an EVT for this LLVM IR type.
106 ValueVTs.push_back(TLI.getValueType(Ty));
108 Offsets->push_back(StartingOffset);
111 /// ExtractTypeInfo - Returns the type info, possibly bitcast, encoded in V.
112 GlobalValue *llvm::ExtractTypeInfo(Value *V) {
113 V = V->stripPointerCasts();
114 GlobalValue *GV = dyn_cast<GlobalValue>(V);
115 GlobalVariable *Var = dyn_cast<GlobalVariable>(V);
117 if (Var && Var->getName() == "llvm.eh.catch.all.value") {
118 assert(Var->hasInitializer() &&
119 "The EH catch-all value must have an initializer");
120 Value *Init = Var->getInitializer();
121 GV = dyn_cast<GlobalValue>(Init);
122 if (!GV) V = cast<ConstantPointerNull>(Init);
125 assert((GV || isa<ConstantPointerNull>(V)) &&
126 "TypeInfo must be a global variable or NULL");
130 /// hasInlineAsmMemConstraint - Return true if the inline asm instruction being
131 /// processed uses a memory 'm' constraint.
133 llvm::hasInlineAsmMemConstraint(InlineAsm::ConstraintInfoVector &CInfos,
134 const TargetLowering &TLI) {
135 for (unsigned i = 0, e = CInfos.size(); i != e; ++i) {
136 InlineAsm::ConstraintInfo &CI = CInfos[i];
137 for (unsigned j = 0, ee = CI.Codes.size(); j != ee; ++j) {
138 TargetLowering::ConstraintType CType = TLI.getConstraintType(CI.Codes[j]);
139 if (CType == TargetLowering::C_Memory)
143 // Indirect operand accesses access memory.
151 /// getFCmpCondCode - Return the ISD condition code corresponding to
152 /// the given LLVM IR floating-point condition code. This includes
153 /// consideration of global floating-point math flags.
155 ISD::CondCode llvm::getFCmpCondCode(FCmpInst::Predicate Pred) {
157 case FCmpInst::FCMP_FALSE: return ISD::SETFALSE;
158 case FCmpInst::FCMP_OEQ: return ISD::SETOEQ;
159 case FCmpInst::FCMP_OGT: return ISD::SETOGT;
160 case FCmpInst::FCMP_OGE: return ISD::SETOGE;
161 case FCmpInst::FCMP_OLT: return ISD::SETOLT;
162 case FCmpInst::FCMP_OLE: return ISD::SETOLE;
163 case FCmpInst::FCMP_ONE: return ISD::SETONE;
164 case FCmpInst::FCMP_ORD: return ISD::SETO;
165 case FCmpInst::FCMP_UNO: return ISD::SETUO;
166 case FCmpInst::FCMP_UEQ: return ISD::SETUEQ;
167 case FCmpInst::FCMP_UGT: return ISD::SETUGT;
168 case FCmpInst::FCMP_UGE: return ISD::SETUGE;
169 case FCmpInst::FCMP_ULT: return ISD::SETULT;
170 case FCmpInst::FCMP_ULE: return ISD::SETULE;
171 case FCmpInst::FCMP_UNE: return ISD::SETUNE;
172 case FCmpInst::FCMP_TRUE: return ISD::SETTRUE;
173 default: llvm_unreachable("Invalid FCmp predicate opcode!");
177 ISD::CondCode llvm::getFCmpCodeWithoutNaN(ISD::CondCode CC) {
179 case ISD::SETOEQ: case ISD::SETUEQ: return ISD::SETEQ;
180 case ISD::SETONE: case ISD::SETUNE: return ISD::SETNE;
181 case ISD::SETOLT: case ISD::SETULT: return ISD::SETLT;
182 case ISD::SETOLE: case ISD::SETULE: return ISD::SETLE;
183 case ISD::SETOGT: case ISD::SETUGT: return ISD::SETGT;
184 case ISD::SETOGE: case ISD::SETUGE: return ISD::SETGE;
189 /// getICmpCondCode - Return the ISD condition code corresponding to
190 /// the given LLVM IR integer condition code.
192 ISD::CondCode llvm::getICmpCondCode(ICmpInst::Predicate Pred) {
194 case ICmpInst::ICMP_EQ: return ISD::SETEQ;
195 case ICmpInst::ICMP_NE: return ISD::SETNE;
196 case ICmpInst::ICMP_SLE: return ISD::SETLE;
197 case ICmpInst::ICMP_ULE: return ISD::SETULE;
198 case ICmpInst::ICMP_SGE: return ISD::SETGE;
199 case ICmpInst::ICMP_UGE: return ISD::SETUGE;
200 case ICmpInst::ICMP_SLT: return ISD::SETLT;
201 case ICmpInst::ICMP_ULT: return ISD::SETULT;
202 case ICmpInst::ICMP_SGT: return ISD::SETGT;
203 case ICmpInst::ICMP_UGT: return ISD::SETUGT;
205 llvm_unreachable("Invalid ICmp predicate opcode!");
209 static bool isNoopBitcast(Type *T1, Type *T2,
210 const TargetLoweringBase& TLI) {
211 return T1 == T2 || (T1->isPointerTy() && T2->isPointerTy()) ||
212 (isa<VectorType>(T1) && isa<VectorType>(T2) &&
213 TLI.isTypeLegal(EVT::getEVT(T1)) && TLI.isTypeLegal(EVT::getEVT(T2)));
216 /// Look through operations that will be free to find the earliest source of
219 /// @param ValLoc If V has aggegate type, we will be interested in a particular
220 /// scalar component. This records its address; the reverse of this list gives a
221 /// sequence of indices appropriate for an extractvalue to locate the important
222 /// value. This value is updated during the function and on exit will indicate
223 /// similar information for the Value returned.
225 /// @param DataBits If this function looks through truncate instructions, this
226 /// will record the smallest size attained.
227 static const Value *getNoopInput(const Value *V,
228 SmallVectorImpl<unsigned> &ValLoc,
230 const TargetLoweringBase &TLI) {
232 // Try to look through V1; if V1 is not an instruction, it can't be looked
234 const Instruction *I = dyn_cast<Instruction>(V);
235 if (!I || I->getNumOperands() == 0) return V;
236 const Value *NoopInput = nullptr;
238 Value *Op = I->getOperand(0);
239 if (isa<BitCastInst>(I)) {
240 // Look through truly no-op bitcasts.
241 if (isNoopBitcast(Op->getType(), I->getType(), TLI))
243 } else if (isa<GetElementPtrInst>(I)) {
244 // Look through getelementptr
245 if (cast<GetElementPtrInst>(I)->hasAllZeroIndices())
247 } else if (isa<IntToPtrInst>(I)) {
248 // Look through inttoptr.
249 // Make sure this isn't a truncating or extending cast. We could
250 // support this eventually, but don't bother for now.
251 if (!isa<VectorType>(I->getType()) &&
252 TLI.getPointerTy().getSizeInBits() ==
253 cast<IntegerType>(Op->getType())->getBitWidth())
255 } else if (isa<PtrToIntInst>(I)) {
256 // Look through ptrtoint.
257 // Make sure this isn't a truncating or extending cast. We could
258 // support this eventually, but don't bother for now.
259 if (!isa<VectorType>(I->getType()) &&
260 TLI.getPointerTy().getSizeInBits() ==
261 cast<IntegerType>(I->getType())->getBitWidth())
263 } else if (isa<TruncInst>(I) &&
264 TLI.allowTruncateForTailCall(Op->getType(), I->getType())) {
265 DataBits = std::min(DataBits, I->getType()->getPrimitiveSizeInBits());
267 } else if (isa<CallInst>(I)) {
268 // Look through call (skipping callee)
269 for (User::const_op_iterator i = I->op_begin(), e = I->op_end() - 1;
271 unsigned attrInd = i - I->op_begin() + 1;
272 if (cast<CallInst>(I)->paramHasAttr(attrInd, Attribute::Returned) &&
273 isNoopBitcast((*i)->getType(), I->getType(), TLI)) {
278 } else if (isa<InvokeInst>(I)) {
279 // Look through invoke (skipping BB, BB, Callee)
280 for (User::const_op_iterator i = I->op_begin(), e = I->op_end() - 3;
282 unsigned attrInd = i - I->op_begin() + 1;
283 if (cast<InvokeInst>(I)->paramHasAttr(attrInd, Attribute::Returned) &&
284 isNoopBitcast((*i)->getType(), I->getType(), TLI)) {
289 } else if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(V)) {
290 // Value may come from either the aggregate or the scalar
291 ArrayRef<unsigned> InsertLoc = IVI->getIndices();
292 if (std::equal(InsertLoc.rbegin(), InsertLoc.rend(),
294 // The type being inserted is a nested sub-type of the aggregate; we
295 // have to remove those initial indices to get the location we're
296 // interested in for the operand.
297 ValLoc.resize(ValLoc.size() - InsertLoc.size());
298 NoopInput = IVI->getInsertedValueOperand();
300 // The struct we're inserting into has the value we're interested in, no
301 // change of address.
304 } else if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(V)) {
305 // The part we're interested in will inevitably be some sub-section of the
306 // previous aggregate. Combine the two paths to obtain the true address of
308 ArrayRef<unsigned> ExtractLoc = EVI->getIndices();
309 std::copy(ExtractLoc.rbegin(), ExtractLoc.rend(),
310 std::back_inserter(ValLoc));
313 // Terminate if we couldn't find anything to look through.
321 /// Return true if this scalar return value only has bits discarded on its path
322 /// from the "tail call" to the "ret". This includes the obvious noop
323 /// instructions handled by getNoopInput above as well as free truncations (or
324 /// extensions prior to the call).
325 static bool slotOnlyDiscardsData(const Value *RetVal, const Value *CallVal,
326 SmallVectorImpl<unsigned> &RetIndices,
327 SmallVectorImpl<unsigned> &CallIndices,
328 bool AllowDifferingSizes,
329 const TargetLoweringBase &TLI) {
331 // Trace the sub-value needed by the return value as far back up the graph as
332 // possible, in the hope that it will intersect with the value produced by the
333 // call. In the simple case with no "returned" attribute, the hope is actually
334 // that we end up back at the tail call instruction itself.
335 unsigned BitsRequired = UINT_MAX;
336 RetVal = getNoopInput(RetVal, RetIndices, BitsRequired, TLI);
338 // If this slot in the value returned is undef, it doesn't matter what the
339 // call puts there, it'll be fine.
340 if (isa<UndefValue>(RetVal))
343 // Now do a similar search up through the graph to find where the value
344 // actually returned by the "tail call" comes from. In the simple case without
345 // a "returned" attribute, the search will be blocked immediately and the loop
347 unsigned BitsProvided = UINT_MAX;
348 CallVal = getNoopInput(CallVal, CallIndices, BitsProvided, TLI);
350 // There's no hope if we can't actually trace them to (the same part of!) the
352 if (CallVal != RetVal || CallIndices != RetIndices)
355 // However, intervening truncates may have made the call non-tail. Make sure
356 // all the bits that are needed by the "ret" have been provided by the "tail
357 // call". FIXME: with sufficiently cunning bit-tracking, we could look through
359 if (BitsProvided < BitsRequired ||
360 (!AllowDifferingSizes && BitsProvided != BitsRequired))
366 /// For an aggregate type, determine whether a given index is within bounds or
368 static bool indexReallyValid(CompositeType *T, unsigned Idx) {
369 if (ArrayType *AT = dyn_cast<ArrayType>(T))
370 return Idx < AT->getNumElements();
372 return Idx < cast<StructType>(T)->getNumElements();
375 /// Move the given iterators to the next leaf type in depth first traversal.
377 /// Performs a depth-first traversal of the type as specified by its arguments,
378 /// stopping at the next leaf node (which may be a legitimate scalar type or an
379 /// empty struct or array).
381 /// @param SubTypes List of the partial components making up the type from
382 /// outermost to innermost non-empty aggregate. The element currently
383 /// represented is SubTypes.back()->getTypeAtIndex(Path.back() - 1).
385 /// @param Path Set of extractvalue indices leading from the outermost type
386 /// (SubTypes[0]) to the leaf node currently represented.
388 /// @returns true if a new type was found, false otherwise. Calling this
389 /// function again on a finished iterator will repeatedly return
390 /// false. SubTypes.back()->getTypeAtIndex(Path.back()) is either an empty
391 /// aggregate or a non-aggregate
392 static bool advanceToNextLeafType(SmallVectorImpl<CompositeType *> &SubTypes,
393 SmallVectorImpl<unsigned> &Path) {
394 // First march back up the tree until we can successfully increment one of the
395 // coordinates in Path.
396 while (!Path.empty() && !indexReallyValid(SubTypes.back(), Path.back() + 1)) {
401 // If we reached the top, then the iterator is done.
405 // We know there's *some* valid leaf now, so march back down the tree picking
406 // out the left-most element at each node.
408 Type *DeeperType = SubTypes.back()->getTypeAtIndex(Path.back());
409 while (DeeperType->isAggregateType()) {
410 CompositeType *CT = cast<CompositeType>(DeeperType);
411 if (!indexReallyValid(CT, 0))
414 SubTypes.push_back(CT);
417 DeeperType = CT->getTypeAtIndex(0U);
423 /// Find the first non-empty, scalar-like type in Next and setup the iterator
426 /// Assuming Next is an aggregate of some kind, this function will traverse the
427 /// tree from left to right (i.e. depth-first) looking for the first
428 /// non-aggregate type which will play a role in function return.
430 /// For example, if Next was {[0 x i64], {{}, i32, {}}, i32} then we would setup
431 /// Path as [1, 1] and SubTypes as [Next, {{}, i32, {}}] to represent the first
432 /// i32 in that type.
433 static bool firstRealType(Type *Next,
434 SmallVectorImpl<CompositeType *> &SubTypes,
435 SmallVectorImpl<unsigned> &Path) {
436 // First initialise the iterator components to the first "leaf" node
437 // (i.e. node with no valid sub-type at any index, so {} does count as a leaf
438 // despite nominally being an aggregate).
439 while (Next->isAggregateType() &&
440 indexReallyValid(cast<CompositeType>(Next), 0)) {
441 SubTypes.push_back(cast<CompositeType>(Next));
443 Next = cast<CompositeType>(Next)->getTypeAtIndex(0U);
446 // If there's no Path now, Next was originally scalar already (or empty
447 // leaf). We're done.
451 // Otherwise, use normal iteration to keep looking through the tree until we
452 // find a non-aggregate type.
453 while (SubTypes.back()->getTypeAtIndex(Path.back())->isAggregateType()) {
454 if (!advanceToNextLeafType(SubTypes, Path))
461 /// Set the iterator data-structures to the next non-empty, non-aggregate
463 static bool nextRealType(SmallVectorImpl<CompositeType *> &SubTypes,
464 SmallVectorImpl<unsigned> &Path) {
466 if (!advanceToNextLeafType(SubTypes, Path))
469 assert(!Path.empty() && "found a leaf but didn't set the path?");
470 } while (SubTypes.back()->getTypeAtIndex(Path.back())->isAggregateType());
476 /// Test if the given instruction is in a position to be optimized
477 /// with a tail-call. This roughly means that it's in a block with
478 /// a return and there's nothing that needs to be scheduled
479 /// between it and the return.
481 /// This function only tests target-independent requirements.
482 bool llvm::isInTailCallPosition(ImmutableCallSite CS, const TargetMachine &TM) {
483 const Instruction *I = CS.getInstruction();
484 const BasicBlock *ExitBB = I->getParent();
485 const TerminatorInst *Term = ExitBB->getTerminator();
486 const ReturnInst *Ret = dyn_cast<ReturnInst>(Term);
488 // The block must end in a return statement or unreachable.
490 // FIXME: Decline tailcall if it's not guaranteed and if the block ends in
491 // an unreachable, for now. The way tailcall optimization is currently
492 // implemented means it will add an epilogue followed by a jump. That is
493 // not profitable. Also, if the callee is a special function (e.g.
494 // longjmp on x86), it can end up causing miscompilation that has not
495 // been fully understood.
497 (!TM.Options.GuaranteedTailCallOpt || !isa<UnreachableInst>(Term)))
500 // If I will have a chain, make sure no other instruction that will have a
501 // chain interposes between I and the return.
502 if (I->mayHaveSideEffects() || I->mayReadFromMemory() ||
503 !isSafeToSpeculativelyExecute(I))
504 for (BasicBlock::const_iterator BBI = std::prev(ExitBB->end(), 2);; --BBI) {
507 // Debug info intrinsics do not get in the way of tail call optimization.
508 if (isa<DbgInfoIntrinsic>(BBI))
510 if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() ||
511 !isSafeToSpeculativelyExecute(BBI))
515 return returnTypeIsEligibleForTailCall(
516 ExitBB->getParent(), I, Ret, *TM.getSubtargetImpl()->getTargetLowering());
519 bool llvm::returnTypeIsEligibleForTailCall(const Function *F,
520 const Instruction *I,
521 const ReturnInst *Ret,
522 const TargetLoweringBase &TLI) {
523 // If the block ends with a void return or unreachable, it doesn't matter
524 // what the call's return type is.
525 if (!Ret || Ret->getNumOperands() == 0) return true;
527 // If the return value is undef, it doesn't matter what the call's
529 if (isa<UndefValue>(Ret->getOperand(0))) return true;
531 // Make sure the attributes attached to each return are compatible.
532 AttrBuilder CallerAttrs(F->getAttributes(),
533 AttributeSet::ReturnIndex);
534 AttrBuilder CalleeAttrs(cast<CallInst>(I)->getAttributes(),
535 AttributeSet::ReturnIndex);
537 // Noalias is completely benign as far as calling convention goes, it
538 // shouldn't affect whether the call is a tail call.
539 CallerAttrs = CallerAttrs.removeAttribute(Attribute::NoAlias);
540 CalleeAttrs = CalleeAttrs.removeAttribute(Attribute::NoAlias);
542 bool AllowDifferingSizes = true;
543 if (CallerAttrs.contains(Attribute::ZExt)) {
544 if (!CalleeAttrs.contains(Attribute::ZExt))
547 AllowDifferingSizes = false;
548 CallerAttrs.removeAttribute(Attribute::ZExt);
549 CalleeAttrs.removeAttribute(Attribute::ZExt);
550 } else if (CallerAttrs.contains(Attribute::SExt)) {
551 if (!CalleeAttrs.contains(Attribute::SExt))
554 AllowDifferingSizes = false;
555 CallerAttrs.removeAttribute(Attribute::SExt);
556 CalleeAttrs.removeAttribute(Attribute::SExt);
559 // If they're still different, there's some facet we don't understand
560 // (currently only "inreg", but in future who knows). It may be OK but the
561 // only safe option is to reject the tail call.
562 if (CallerAttrs != CalleeAttrs)
565 const Value *RetVal = Ret->getOperand(0), *CallVal = I;
566 SmallVector<unsigned, 4> RetPath, CallPath;
567 SmallVector<CompositeType *, 4> RetSubTypes, CallSubTypes;
569 bool RetEmpty = !firstRealType(RetVal->getType(), RetSubTypes, RetPath);
570 bool CallEmpty = !firstRealType(CallVal->getType(), CallSubTypes, CallPath);
572 // Nothing's actually returned, it doesn't matter what the callee put there
573 // it's a valid tail call.
577 // Iterate pairwise through each of the value types making up the tail call
578 // and the corresponding return. For each one we want to know whether it's
579 // essentially going directly from the tail call to the ret, via operations
580 // that end up not generating any code.
582 // We allow a certain amount of covariance here. For example it's permitted
583 // for the tail call to define more bits than the ret actually cares about
584 // (e.g. via a truncate).
587 // We've exhausted the values produced by the tail call instruction, the
588 // rest are essentially undef. The type doesn't really matter, but we need
590 Type *SlotType = RetSubTypes.back()->getTypeAtIndex(RetPath.back());
591 CallVal = UndefValue::get(SlotType);
594 // The manipulations performed when we're looking through an insertvalue or
595 // an extractvalue would happen at the front of the RetPath list, so since
596 // we have to copy it anyway it's more efficient to create a reversed copy.
598 SmallVector<unsigned, 4> TmpRetPath, TmpCallPath;
599 copy(RetPath.rbegin(), RetPath.rend(), std::back_inserter(TmpRetPath));
600 copy(CallPath.rbegin(), CallPath.rend(), std::back_inserter(TmpCallPath));
602 // Finally, we can check whether the value produced by the tail call at this
603 // index is compatible with the value we return.
604 if (!slotOnlyDiscardsData(RetVal, CallVal, TmpRetPath, TmpCallPath,
605 AllowDifferingSizes, TLI))
608 CallEmpty = !nextRealType(CallSubTypes, CallPath);
609 } while(nextRealType(RetSubTypes, RetPath));
614 bool llvm::canBeOmittedFromSymbolTable(const GlobalValue *GV) {
615 if (!GV->hasLinkOnceODRLinkage())
618 if (GV->hasUnnamedAddr())
621 // If it is a non constant variable, it needs to be uniqued across shared
623 if (const GlobalVariable *Var = dyn_cast<GlobalVariable>(GV)) {
624 if (!Var->isConstant())
628 // An alias can point to a variable. We could try to resolve the alias to
629 // decide, but for now just don't hide them.
630 if (isa<GlobalAlias>(GV))
634 if (GlobalStatus::analyzeGlobal(GV, GS))
637 return !GS.IsCompared;