//
//===----------------------------------------------------------------------===//
//
-// This file defines several CodeGen-specific LLVM IR analysis utilties.
+// This file defines several CodeGen-specific LLVM IR analysis utilities.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/Analysis.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Target/TargetLowering.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
+#include "llvm/Transforms/Utils/GlobalStatus.h"
+
using namespace llvm;
-/// ComputeLinearIndex - Given an LLVM IR aggregate type and a sequence
-/// of insertvalue or extractvalue indices that identify a member, return
-/// the linearized index of the start of the member.
-///
+/// Compute the linearized index of a member in a nested aggregate/struct/array
+/// by recursing and accumulating CurIndex as long as there are indices in the
+/// index list.
unsigned llvm::ComputeLinearIndex(Type *Ty,
const unsigned *Indices,
const unsigned *IndicesEnd,
EI != EE; ++EI) {
if (Indices && *Indices == unsigned(EI - EB))
return ComputeLinearIndex(*EI, Indices+1, IndicesEnd, CurIndex);
- CurIndex = ComputeLinearIndex(*EI, 0, 0, CurIndex);
+ CurIndex = ComputeLinearIndex(*EI, nullptr, nullptr, CurIndex);
}
+ assert(!Indices && "Unexpected out of bound");
return CurIndex;
}
// Given an array type, recursively traverse the elements.
else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
Type *EltTy = ATy->getElementType();
- for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i) {
- if (Indices && *Indices == i)
- return ComputeLinearIndex(EltTy, Indices+1, IndicesEnd, CurIndex);
- CurIndex = ComputeLinearIndex(EltTy, 0, 0, CurIndex);
+ unsigned NumElts = ATy->getNumElements();
+ // Compute the Linear offset when jumping one element of the array
+ unsigned EltLinearOffset = ComputeLinearIndex(EltTy, nullptr, nullptr, 0);
+ if (Indices) {
+ assert(*Indices < NumElts && "Unexpected out of bound");
+ // If the indice is inside the array, compute the index to the requested
+ // elt and recurse inside the element with the end of the indices list
+ CurIndex += EltLinearOffset* *Indices;
+ return ComputeLinearIndex(EltTy, Indices+1, IndicesEnd, CurIndex);
}
+ CurIndex += EltLinearOffset*NumElts;
return CurIndex;
}
// We haven't found the type we're looking for, so keep searching.
/// If Offsets is non-null, it points to a vector to be filled in
/// with the in-memory offsets of each of the individual values.
///
-void llvm::ComputeValueVTs(const TargetLowering &TLI, Type *Ty,
- SmallVectorImpl<EVT> &ValueVTs,
+void llvm::ComputeValueVTs(const TargetLowering &TLI, const DataLayout &DL,
+ Type *Ty, SmallVectorImpl<EVT> &ValueVTs,
SmallVectorImpl<uint64_t> *Offsets,
uint64_t StartingOffset) {
// Given a struct type, recursively traverse the elements.
if (StructType *STy = dyn_cast<StructType>(Ty)) {
- const StructLayout *SL = TLI.getDataLayout()->getStructLayout(STy);
+ const StructLayout *SL = DL.getStructLayout(STy);
for (StructType::element_iterator EB = STy->element_begin(),
EI = EB,
EE = STy->element_end();
EI != EE; ++EI)
- ComputeValueVTs(TLI, *EI, ValueVTs, Offsets,
+ ComputeValueVTs(TLI, DL, *EI, ValueVTs, Offsets,
StartingOffset + SL->getElementOffset(EI - EB));
return;
}
// Given an array type, recursively traverse the elements.
if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
Type *EltTy = ATy->getElementType();
- uint64_t EltSize = TLI.getDataLayout()->getTypeAllocSize(EltTy);
+ uint64_t EltSize = DL.getTypeAllocSize(EltTy);
for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i)
- ComputeValueVTs(TLI, EltTy, ValueVTs, Offsets,
+ ComputeValueVTs(TLI, DL, EltTy, ValueVTs, Offsets,
StartingOffset + i * EltSize);
return;
}
if (Ty->isVoidTy())
return;
// Base case: we can get an EVT for this LLVM IR type.
- ValueVTs.push_back(TLI.getValueType(Ty));
+ ValueVTs.push_back(TLI.getValueType(DL, Ty));
if (Offsets)
Offsets->push_back(StartingOffset);
}
/// ExtractTypeInfo - Returns the type info, possibly bitcast, encoded in V.
-GlobalVariable *llvm::ExtractTypeInfo(Value *V) {
+GlobalValue *llvm::ExtractTypeInfo(Value *V) {
V = V->stripPointerCasts();
- GlobalVariable *GV = dyn_cast<GlobalVariable>(V);
+ GlobalValue *GV = dyn_cast<GlobalValue>(V);
+ GlobalVariable *Var = dyn_cast<GlobalVariable>(V);
- if (GV && GV->getName() == "llvm.eh.catch.all.value") {
- assert(GV->hasInitializer() &&
+ if (Var && Var->getName() == "llvm.eh.catch.all.value") {
+ assert(Var->hasInitializer() &&
"The EH catch-all value must have an initializer");
- Value *Init = GV->getInitializer();
- GV = dyn_cast<GlobalVariable>(Init);
+ Value *Init = Var->getInitializer();
+ GV = dyn_cast<GlobalValue>(Init);
if (!GV) V = cast<ConstantPointerNull>(Init);
}
}
static bool isNoopBitcast(Type *T1, Type *T2,
- const TargetLowering& TLI) {
+ const TargetLoweringBase& TLI) {
return T1 == T2 || (T1->isPointerTy() && T2->isPointerTy()) ||
(isa<VectorType>(T1) && isa<VectorType>(T2) &&
TLI.isTypeLegal(EVT::getEVT(T1)) && TLI.isTypeLegal(EVT::getEVT(T2)));
}
-/// sameNoopInput - Return true if V1 == V2, else if either V1 or V2 is a noop
-/// (i.e., lowers to no machine code), look through it (and any transitive noop
-/// operands to it) and check if it has the same noop input value. This is
-/// used to determine if a tail call can be formed.
-static bool sameNoopInput(const Value *V1, const Value *V2,
- SmallVectorImpl<unsigned> &Els1,
- SmallVectorImpl<unsigned> &Els2,
- const TargetLowering &TLI) {
- using std::swap;
- bool swapParity = false;
- bool equalEls = Els1 == Els2;
+/// Look through operations that will be free to find the earliest source of
+/// this value.
+///
+/// @param ValLoc If V has aggegate type, we will be interested in a particular
+/// scalar component. This records its address; the reverse of this list gives a
+/// sequence of indices appropriate for an extractvalue to locate the important
+/// value. This value is updated during the function and on exit will indicate
+/// similar information for the Value returned.
+///
+/// @param DataBits If this function looks through truncate instructions, this
+/// will record the smallest size attained.
+static const Value *getNoopInput(const Value *V,
+ SmallVectorImpl<unsigned> &ValLoc,
+ unsigned &DataBits,
+ const TargetLoweringBase &TLI,
+ const DataLayout &DL) {
while (true) {
- if ((equalEls && V1 == V2) || isa<UndefValue>(V1) || isa<UndefValue>(V2)) {
- if (swapParity)
- // Revert to original Els1 and Els2 to avoid confusing recursive calls
- swap(Els1, Els2);
- return true;
- }
-
// Try to look through V1; if V1 is not an instruction, it can't be looked
// through.
- const Instruction *I = dyn_cast<Instruction>(V1);
- const Value *NoopInput = 0;
- if (I != 0 && I->getNumOperands() > 0) {
- Value *Op = I->getOperand(0);
- if (isa<TruncInst>(I)) {
- // Look through truly no-op truncates.
- if (TLI.isTruncateFree(Op->getType(), I->getType()))
- NoopInput = Op;
- } else if (isa<BitCastInst>(I)) {
- // Look through truly no-op bitcasts.
- if (isNoopBitcast(Op->getType(), I->getType(), TLI))
- NoopInput = Op;
- } else if (isa<GetElementPtrInst>(I)) {
- // Look through getelementptr
- if (cast<GetElementPtrInst>(I)->hasAllZeroIndices())
- NoopInput = Op;
- } else if (isa<IntToPtrInst>(I)) {
- // Look through inttoptr.
- // Make sure this isn't a truncating or extending cast. We could
- // support this eventually, but don't bother for now.
- if (!isa<VectorType>(I->getType()) &&
- TLI.getPointerTy().getSizeInBits() ==
+ const Instruction *I = dyn_cast<Instruction>(V);
+ if (!I || I->getNumOperands() == 0) return V;
+ const Value *NoopInput = nullptr;
+
+ Value *Op = I->getOperand(0);
+ if (isa<BitCastInst>(I)) {
+ // Look through truly no-op bitcasts.
+ if (isNoopBitcast(Op->getType(), I->getType(), TLI))
+ NoopInput = Op;
+ } else if (isa<GetElementPtrInst>(I)) {
+ // Look through getelementptr
+ if (cast<GetElementPtrInst>(I)->hasAllZeroIndices())
+ NoopInput = Op;
+ } else if (isa<IntToPtrInst>(I)) {
+ // Look through inttoptr.
+ // Make sure this isn't a truncating or extending cast. We could
+ // support this eventually, but don't bother for now.
+ if (!isa<VectorType>(I->getType()) &&
+ DL.getPointerSizeInBits() ==
cast<IntegerType>(Op->getType())->getBitWidth())
- NoopInput = Op;
-
} else if (isa<PtrToIntInst>(I)) {
- // Look through ptrtoint.
- // Make sure this isn't a truncating or extending cast. We could
- // support this eventually, but don't bother for now.
- if (!isa<VectorType>(I->getType()) &&
- TLI.getPointerTy().getSizeInBits() ==
+ NoopInput = Op;
+ } else if (isa<PtrToIntInst>(I)) {
+ // Look through ptrtoint.
+ // Make sure this isn't a truncating or extending cast. We could
+ // support this eventually, but don't bother for now.
+ if (!isa<VectorType>(I->getType()) &&
+ DL.getPointerSizeInBits() ==
cast<IntegerType>(I->getType())->getBitWidth())
- NoopInput = Op;
- } else if (isa<CallInst>(I)) {
- // Look through call
- for (User::const_op_iterator i = I->op_begin(),
- // Skip Callee
- e = I->op_end() - 1;
- i != e; ++i) {
- unsigned attrInd = i - I->op_begin() + 1;
- if (cast<CallInst>(I)->paramHasAttr(attrInd, Attribute::Returned) &&
- isNoopBitcast((*i)->getType(), I->getType(), TLI)) {
- NoopInput = *i;
- break;
- }
+ NoopInput = Op;
+ } else if (isa<TruncInst>(I) &&
+ TLI.allowTruncateForTailCall(Op->getType(), I->getType())) {
+ DataBits = std::min(DataBits, I->getType()->getPrimitiveSizeInBits());
+ NoopInput = Op;
+ } else if (isa<CallInst>(I)) {
+ // Look through call (skipping callee)
+ for (User::const_op_iterator i = I->op_begin(), e = I->op_end() - 1;
+ i != e; ++i) {
+ unsigned attrInd = i - I->op_begin() + 1;
+ if (cast<CallInst>(I)->paramHasAttr(attrInd, Attribute::Returned) &&
+ isNoopBitcast((*i)->getType(), I->getType(), TLI)) {
+ NoopInput = *i;
+ break;
}
- } else if (isa<InvokeInst>(I)) {
- // Look through invoke
- for (User::const_op_iterator i = I->op_begin(),
- // Skip BB, BB, Callee
- e = I->op_end() - 3;
- i != e; ++i) {
- unsigned attrInd = i - I->op_begin() + 1;
- if (cast<InvokeInst>(I)->paramHasAttr(attrInd, Attribute::Returned) &&
- isNoopBitcast((*i)->getType(), I->getType(), TLI)) {
- NoopInput = *i;
- break;
- }
+ }
+ } else if (isa<InvokeInst>(I)) {
+ // Look through invoke (skipping BB, BB, Callee)
+ for (User::const_op_iterator i = I->op_begin(), e = I->op_end() - 3;
+ i != e; ++i) {
+ unsigned attrInd = i - I->op_begin() + 1;
+ if (cast<InvokeInst>(I)->paramHasAttr(attrInd, Attribute::Returned) &&
+ isNoopBitcast((*i)->getType(), I->getType(), TLI)) {
+ NoopInput = *i;
+ break;
}
}
+ } else if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(V)) {
+ // Value may come from either the aggregate or the scalar
+ ArrayRef<unsigned> InsertLoc = IVI->getIndices();
+ if (ValLoc.size() >= InsertLoc.size() &&
+ std::equal(InsertLoc.begin(), InsertLoc.end(), ValLoc.rbegin())) {
+ // The type being inserted is a nested sub-type of the aggregate; we
+ // have to remove those initial indices to get the location we're
+ // interested in for the operand.
+ ValLoc.resize(ValLoc.size() - InsertLoc.size());
+ NoopInput = IVI->getInsertedValueOperand();
+ } else {
+ // The struct we're inserting into has the value we're interested in, no
+ // change of address.
+ NoopInput = Op;
+ }
+ } else if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(V)) {
+ // The part we're interested in will inevitably be some sub-section of the
+ // previous aggregate. Combine the two paths to obtain the true address of
+ // our element.
+ ArrayRef<unsigned> ExtractLoc = EVI->getIndices();
+ ValLoc.append(ExtractLoc.rbegin(), ExtractLoc.rend());
+ NoopInput = Op;
}
+ // Terminate if we couldn't find anything to look through.
+ if (!NoopInput)
+ return V;
- if (NoopInput) {
- V1 = NoopInput;
- continue;
- }
+ V = NoopInput;
+ }
+}
+
+/// Return true if this scalar return value only has bits discarded on its path
+/// from the "tail call" to the "ret". This includes the obvious noop
+/// instructions handled by getNoopInput above as well as free truncations (or
+/// extensions prior to the call).
+static bool slotOnlyDiscardsData(const Value *RetVal, const Value *CallVal,
+ SmallVectorImpl<unsigned> &RetIndices,
+ SmallVectorImpl<unsigned> &CallIndices,
+ bool AllowDifferingSizes,
+ const TargetLoweringBase &TLI,
+ const DataLayout &DL) {
+
+ // Trace the sub-value needed by the return value as far back up the graph as
+ // possible, in the hope that it will intersect with the value produced by the
+ // call. In the simple case with no "returned" attribute, the hope is actually
+ // that we end up back at the tail call instruction itself.
+ unsigned BitsRequired = UINT_MAX;
+ RetVal = getNoopInput(RetVal, RetIndices, BitsRequired, TLI, DL);
+
+ // If this slot in the value returned is undef, it doesn't matter what the
+ // call puts there, it'll be fine.
+ if (isa<UndefValue>(RetVal))
+ return true;
+
+ // Now do a similar search up through the graph to find where the value
+ // actually returned by the "tail call" comes from. In the simple case without
+ // a "returned" attribute, the search will be blocked immediately and the loop
+ // a Noop.
+ unsigned BitsProvided = UINT_MAX;
+ CallVal = getNoopInput(CallVal, CallIndices, BitsProvided, TLI, DL);
+
+ // There's no hope if we can't actually trace them to (the same part of!) the
+ // same value.
+ if (CallVal != RetVal || CallIndices != RetIndices)
+ return false;
+
+ // However, intervening truncates may have made the call non-tail. Make sure
+ // all the bits that are needed by the "ret" have been provided by the "tail
+ // call". FIXME: with sufficiently cunning bit-tracking, we could look through
+ // extensions too.
+ if (BitsProvided < BitsRequired ||
+ (!AllowDifferingSizes && BitsProvided != BitsRequired))
+ return false;
- // If we already swapped, avoid infinite loop
- if (swapParity)
- break;
+ return true;
+}
+
+/// For an aggregate type, determine whether a given index is within bounds or
+/// not.
+static bool indexReallyValid(CompositeType *T, unsigned Idx) {
+ if (ArrayType *AT = dyn_cast<ArrayType>(T))
+ return Idx < AT->getNumElements();
+
+ return Idx < cast<StructType>(T)->getNumElements();
+}
- // Otherwise, swap V1<->V2, Els1<->Els2
- swap(V1, V2);
- swap(Els1, Els2);
- swapParity = !swapParity;
+/// Move the given iterators to the next leaf type in depth first traversal.
+///
+/// Performs a depth-first traversal of the type as specified by its arguments,
+/// stopping at the next leaf node (which may be a legitimate scalar type or an
+/// empty struct or array).
+///
+/// @param SubTypes List of the partial components making up the type from
+/// outermost to innermost non-empty aggregate. The element currently
+/// represented is SubTypes.back()->getTypeAtIndex(Path.back() - 1).
+///
+/// @param Path Set of extractvalue indices leading from the outermost type
+/// (SubTypes[0]) to the leaf node currently represented.
+///
+/// @returns true if a new type was found, false otherwise. Calling this
+/// function again on a finished iterator will repeatedly return
+/// false. SubTypes.back()->getTypeAtIndex(Path.back()) is either an empty
+/// aggregate or a non-aggregate
+static bool advanceToNextLeafType(SmallVectorImpl<CompositeType *> &SubTypes,
+ SmallVectorImpl<unsigned> &Path) {
+ // First march back up the tree until we can successfully increment one of the
+ // coordinates in Path.
+ while (!Path.empty() && !indexReallyValid(SubTypes.back(), Path.back() + 1)) {
+ Path.pop_back();
+ SubTypes.pop_back();
}
- for (unsigned n = 0; n < 2; ++n) {
- if (isa<InsertValueInst>(V1)) {
- if (isa<StructType>(V1->getType())) {
- // Look through insertvalue
- unsigned i, e;
- for (i = 0, e = cast<StructType>(V1->getType())->getNumElements();
- i != e; ++i) {
- const Value *InScalar = FindInsertedValue(const_cast<Value*>(V1), i);
- if (InScalar == 0)
- break;
- Els1.push_back(i);
- if (!sameNoopInput(InScalar, V2, Els1, Els2, TLI)) {
- Els1.pop_back();
- break;
- }
- Els1.pop_back();
- }
- if (i == e) {
- if (swapParity)
- swap(Els1, Els2);
- return true;
- }
- }
- } else if (!Els1.empty() && isa<ExtractValueInst>(V1)) {
- const ExtractValueInst *EVI = cast<ExtractValueInst>(V1);
- unsigned i = Els1.back();
- // If the scalar value being inserted is an extractvalue of the right
- // index from the call, then everything is good.
- if (isa<StructType>(EVI->getOperand(0)->getType()) &&
- EVI->getNumIndices() == 1 && EVI->getIndices()[0] == i) {
- // Look through extractvalue
- Els1.pop_back();
- if (sameNoopInput(EVI->getOperand(0), V2, Els1, Els2, TLI)) {
- Els1.push_back(i);
- if (swapParity)
- swap(Els1, Els2);
- return true;
- }
- Els1.push_back(i);
- }
- }
+ // If we reached the top, then the iterator is done.
+ if (Path.empty())
+ return false;
+
+ // We know there's *some* valid leaf now, so march back down the tree picking
+ // out the left-most element at each node.
+ ++Path.back();
+ Type *DeeperType = SubTypes.back()->getTypeAtIndex(Path.back());
+ while (DeeperType->isAggregateType()) {
+ CompositeType *CT = cast<CompositeType>(DeeperType);
+ if (!indexReallyValid(CT, 0))
+ return true;
+
+ SubTypes.push_back(CT);
+ Path.push_back(0);
- swap(V1, V2);
- swap(Els1, Els2);
- swapParity = !swapParity;
+ DeeperType = CT->getTypeAtIndex(0U);
}
- if (swapParity)
- swap(Els1, Els2);
- return false;
+ return true;
}
+/// Find the first non-empty, scalar-like type in Next and setup the iterator
+/// components.
+///
+/// Assuming Next is an aggregate of some kind, this function will traverse the
+/// tree from left to right (i.e. depth-first) looking for the first
+/// non-aggregate type which will play a role in function return.
+///
+/// For example, if Next was {[0 x i64], {{}, i32, {}}, i32} then we would setup
+/// Path as [1, 1] and SubTypes as [Next, {{}, i32, {}}] to represent the first
+/// i32 in that type.
+static bool firstRealType(Type *Next,
+ SmallVectorImpl<CompositeType *> &SubTypes,
+ SmallVectorImpl<unsigned> &Path) {
+ // First initialise the iterator components to the first "leaf" node
+ // (i.e. node with no valid sub-type at any index, so {} does count as a leaf
+ // despite nominally being an aggregate).
+ while (Next->isAggregateType() &&
+ indexReallyValid(cast<CompositeType>(Next), 0)) {
+ SubTypes.push_back(cast<CompositeType>(Next));
+ Path.push_back(0);
+ Next = cast<CompositeType>(Next)->getTypeAtIndex(0U);
+ }
+
+ // If there's no Path now, Next was originally scalar already (or empty
+ // leaf). We're done.
+ if (Path.empty())
+ return true;
+
+ // Otherwise, use normal iteration to keep looking through the tree until we
+ // find a non-aggregate type.
+ while (SubTypes.back()->getTypeAtIndex(Path.back())->isAggregateType()) {
+ if (!advanceToNextLeafType(SubTypes, Path))
+ return false;
+ }
+
+ return true;
+}
+
+/// Set the iterator data-structures to the next non-empty, non-aggregate
+/// subtype.
+static bool nextRealType(SmallVectorImpl<CompositeType *> &SubTypes,
+ SmallVectorImpl<unsigned> &Path) {
+ do {
+ if (!advanceToNextLeafType(SubTypes, Path))
+ return false;
+
+ assert(!Path.empty() && "found a leaf but didn't set the path?");
+ } while (SubTypes.back()->getTypeAtIndex(Path.back())->isAggregateType());
+
+ return true;
+}
+
+
/// Test if the given instruction is in a position to be optimized
/// with a tail-call. This roughly means that it's in a block with
/// a return and there's nothing that needs to be scheduled
/// between it and the return.
///
/// This function only tests target-independent requirements.
-bool llvm::isInTailCallPosition(ImmutableCallSite CS,
- const TargetLowering &TLI) {
+bool llvm::isInTailCallPosition(ImmutableCallSite CS, const TargetMachine &TM) {
const Instruction *I = CS.getInstruction();
const BasicBlock *ExitBB = I->getParent();
const TerminatorInst *Term = ExitBB->getTerminator();
// longjmp on x86), it can end up causing miscompilation that has not
// been fully understood.
if (!Ret &&
- (!TLI.getTargetMachine().Options.GuaranteedTailCallOpt ||
- !isa<UnreachableInst>(Term)))
+ (!TM.Options.GuaranteedTailCallOpt || !isa<UnreachableInst>(Term)))
return false;
// If I will have a chain, make sure no other instruction that will have a
// chain interposes between I and the return.
if (I->mayHaveSideEffects() || I->mayReadFromMemory() ||
!isSafeToSpeculativelyExecute(I))
- for (BasicBlock::const_iterator BBI = prior(prior(ExitBB->end())); ;
- --BBI) {
+ for (BasicBlock::const_iterator BBI = std::prev(ExitBB->end(), 2);; --BBI) {
if (&*BBI == I)
break;
// Debug info intrinsics do not get in the way of tail call optimization.
return false;
}
+ const Function *F = ExitBB->getParent();
+ return returnTypeIsEligibleForTailCall(
+ F, I, Ret, *TM.getSubtargetImpl(*F)->getTargetLowering());
+}
+
+bool llvm::returnTypeIsEligibleForTailCall(const Function *F,
+ const Instruction *I,
+ const ReturnInst *Ret,
+ const TargetLoweringBase &TLI) {
// If the block ends with a void return or unreachable, it doesn't matter
// what the call's return type is.
if (!Ret || Ret->getNumOperands() == 0) return true;
// return type is.
if (isa<UndefValue>(Ret->getOperand(0))) return true;
- // Conservatively require the attributes of the call to match those of
- // the return. Ignore noalias because it doesn't affect the call sequence.
- const Function *F = ExitBB->getParent();
- AttributeSet CallerAttrs = F->getAttributes();
- if (AttrBuilder(CallerAttrs, AttributeSet::ReturnIndex).
- removeAttribute(Attribute::NoAlias) !=
- AttrBuilder(CallerAttrs, AttributeSet::ReturnIndex).
- removeAttribute(Attribute::NoAlias))
+ // Make sure the attributes attached to each return are compatible.
+ AttrBuilder CallerAttrs(F->getAttributes(),
+ AttributeSet::ReturnIndex);
+ AttrBuilder CalleeAttrs(cast<CallInst>(I)->getAttributes(),
+ AttributeSet::ReturnIndex);
+
+ // Noalias is completely benign as far as calling convention goes, it
+ // shouldn't affect whether the call is a tail call.
+ CallerAttrs = CallerAttrs.removeAttribute(Attribute::NoAlias);
+ CalleeAttrs = CalleeAttrs.removeAttribute(Attribute::NoAlias);
+
+ bool AllowDifferingSizes = true;
+ if (CallerAttrs.contains(Attribute::ZExt)) {
+ if (!CalleeAttrs.contains(Attribute::ZExt))
+ return false;
+
+ AllowDifferingSizes = false;
+ CallerAttrs.removeAttribute(Attribute::ZExt);
+ CalleeAttrs.removeAttribute(Attribute::ZExt);
+ } else if (CallerAttrs.contains(Attribute::SExt)) {
+ if (!CalleeAttrs.contains(Attribute::SExt))
+ return false;
+
+ AllowDifferingSizes = false;
+ CallerAttrs.removeAttribute(Attribute::SExt);
+ CalleeAttrs.removeAttribute(Attribute::SExt);
+ }
+
+ // If they're still different, there's some facet we don't understand
+ // (currently only "inreg", but in future who knows). It may be OK but the
+ // only safe option is to reject the tail call.
+ if (CallerAttrs != CalleeAttrs)
+ return false;
+
+ const Value *RetVal = Ret->getOperand(0), *CallVal = I;
+ SmallVector<unsigned, 4> RetPath, CallPath;
+ SmallVector<CompositeType *, 4> RetSubTypes, CallSubTypes;
+
+ bool RetEmpty = !firstRealType(RetVal->getType(), RetSubTypes, RetPath);
+ bool CallEmpty = !firstRealType(CallVal->getType(), CallSubTypes, CallPath);
+
+ // Nothing's actually returned, it doesn't matter what the callee put there
+ // it's a valid tail call.
+ if (RetEmpty)
+ return true;
+
+ // Iterate pairwise through each of the value types making up the tail call
+ // and the corresponding return. For each one we want to know whether it's
+ // essentially going directly from the tail call to the ret, via operations
+ // that end up not generating any code.
+ //
+ // We allow a certain amount of covariance here. For example it's permitted
+ // for the tail call to define more bits than the ret actually cares about
+ // (e.g. via a truncate).
+ do {
+ if (CallEmpty) {
+ // We've exhausted the values produced by the tail call instruction, the
+ // rest are essentially undef. The type doesn't really matter, but we need
+ // *something*.
+ Type *SlotType = RetSubTypes.back()->getTypeAtIndex(RetPath.back());
+ CallVal = UndefValue::get(SlotType);
+ }
+
+ // The manipulations performed when we're looking through an insertvalue or
+ // an extractvalue would happen at the front of the RetPath list, so since
+ // we have to copy it anyway it's more efficient to create a reversed copy.
+ SmallVector<unsigned, 4> TmpRetPath(RetPath.rbegin(), RetPath.rend());
+ SmallVector<unsigned, 4> TmpCallPath(CallPath.rbegin(), CallPath.rend());
+
+ // Finally, we can check whether the value produced by the tail call at this
+ // index is compatible with the value we return.
+ if (!slotOnlyDiscardsData(RetVal, CallVal, TmpRetPath, TmpCallPath,
+ AllowDifferingSizes, TLI,
+ F->getParent()->getDataLayout()))
+ return false;
+
+ CallEmpty = !nextRealType(CallSubTypes, CallPath);
+ } while(nextRealType(RetSubTypes, RetPath));
+
+ return true;
+}
+
+bool llvm::canBeOmittedFromSymbolTable(const GlobalValue *GV) {
+ if (!GV->hasLinkOnceODRLinkage())
+ return false;
+
+ if (GV->hasUnnamedAddr())
+ return true;
+
+ // If it is a non constant variable, it needs to be uniqued across shared
+ // objects.
+ if (const GlobalVariable *Var = dyn_cast<GlobalVariable>(GV)) {
+ if (!Var->isConstant())
+ return false;
+ }
+
+ // An alias can point to a variable. We could try to resolve the alias to
+ // decide, but for now just don't hide them.
+ if (isa<GlobalAlias>(GV))
return false;
- // It's not safe to eliminate the sign / zero extension of the return value.
- if (CallerAttrs.hasAttribute(AttributeSet::ReturnIndex, Attribute::ZExt) ||
- CallerAttrs.hasAttribute(AttributeSet::ReturnIndex, Attribute::SExt))
+ GlobalStatus GS;
+ if (GlobalStatus::analyzeGlobal(GV, GS))
return false;
- // Otherwise, make sure the return value and I have the same value
- SmallVector<unsigned, 4> Els1, Els2;
- return sameNoopInput(Ret->getOperand(0), I, Els1, Els2, TLI);
+ return !GS.IsCompared;
}
projects / oota-llvm.git / blobdiff