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+//===-- Analysis.cpp - CodeGen LLVM IR Analysis Utilities -----------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines several CodeGen-specific LLVM IR analysis utilties.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/Analysis.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Target/TargetLowering.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.
+///
+unsigned llvm::ComputeLinearIndex(Type *Ty,
+ const unsigned *Indices,
+ const unsigned *IndicesEnd,
+ unsigned CurIndex) {
+ // Base case: We're done.
+ if (Indices && Indices == IndicesEnd)
+ return CurIndex;
+
+ // Given a struct type, recursively traverse the elements.
+ if (StructType *STy = dyn_cast<StructType>(Ty)) {
+ for (StructType::element_iterator EB = STy->element_begin(),
+ EI = EB,
+ EE = STy->element_end();
+ EI != EE; ++EI) {
+ if (Indices && *Indices == unsigned(EI - EB))
+ return ComputeLinearIndex(*EI, Indices+1, IndicesEnd, CurIndex);
+ CurIndex = ComputeLinearIndex(*EI, 0, 0, CurIndex);
+ }
+ 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);
+ }
+ return CurIndex;
+ }
+ // We haven't found the type we're looking for, so keep searching.
+ return CurIndex + 1;
+}
+
+/// ComputeValueVTs - Given an LLVM IR type, compute a sequence of
+/// EVTs that represent all the individual underlying
+/// non-aggregate types that comprise it.
+///
+/// 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,
+ 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);
+ for (StructType::element_iterator EB = STy->element_begin(),
+ EI = EB,
+ EE = STy->element_end();
+ EI != EE; ++EI)
+ ComputeValueVTs(TLI, *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);
+ for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i)
+ ComputeValueVTs(TLI, EltTy, ValueVTs, Offsets,
+ StartingOffset + i * EltSize);
+ return;
+ }
+ // Interpret void as zero return values.
+ if (Ty->isVoidTy())
+ return;
+ // Base case: we can get an EVT for this LLVM IR type.
+ ValueVTs.push_back(TLI.getValueType(Ty));
+ if (Offsets)
+ Offsets->push_back(StartingOffset);
+}
+
+/// ExtractTypeInfo - Returns the type info, possibly bitcast, encoded in V.
+GlobalVariable *llvm::ExtractTypeInfo(Value *V) {
+ V = V->stripPointerCasts();
+ GlobalVariable *GV = dyn_cast<GlobalVariable>(V);
+
+ if (GV && GV->getName() == "llvm.eh.catch.all.value") {
+ assert(GV->hasInitializer() &&
+ "The EH catch-all value must have an initializer");
+ Value *Init = GV->getInitializer();
+ GV = dyn_cast<GlobalVariable>(Init);
+ if (!GV) V = cast<ConstantPointerNull>(Init);
+ }
+
+ assert((GV || isa<ConstantPointerNull>(V)) &&
+ "TypeInfo must be a global variable or NULL");
+ return GV;
+}
+
+/// hasInlineAsmMemConstraint - Return true if the inline asm instruction being
+/// processed uses a memory 'm' constraint.
+bool
+llvm::hasInlineAsmMemConstraint(InlineAsm::ConstraintInfoVector &CInfos,
+ const TargetLowering &TLI) {
+ for (unsigned i = 0, e = CInfos.size(); i != e; ++i) {
+ InlineAsm::ConstraintInfo &CI = CInfos[i];
+ for (unsigned j = 0, ee = CI.Codes.size(); j != ee; ++j) {
+ TargetLowering::ConstraintType CType = TLI.getConstraintType(CI.Codes[j]);
+ if (CType == TargetLowering::C_Memory)
+ return true;
+ }
+
+ // Indirect operand accesses access memory.
+ if (CI.isIndirect)
+ return true;
+ }
+
+ return false;
+}
+
+/// getFCmpCondCode - Return the ISD condition code corresponding to
+/// the given LLVM IR floating-point condition code. This includes
+/// consideration of global floating-point math flags.
+///
+ISD::CondCode llvm::getFCmpCondCode(FCmpInst::Predicate Pred) {
+ switch (Pred) {
+ case FCmpInst::FCMP_FALSE: return ISD::SETFALSE;
+ case FCmpInst::FCMP_OEQ: return ISD::SETOEQ;
+ case FCmpInst::FCMP_OGT: return ISD::SETOGT;
+ case FCmpInst::FCMP_OGE: return ISD::SETOGE;
+ case FCmpInst::FCMP_OLT: return ISD::SETOLT;
+ case FCmpInst::FCMP_OLE: return ISD::SETOLE;
+ case FCmpInst::FCMP_ONE: return ISD::SETONE;
+ case FCmpInst::FCMP_ORD: return ISD::SETO;
+ case FCmpInst::FCMP_UNO: return ISD::SETUO;
+ case FCmpInst::FCMP_UEQ: return ISD::SETUEQ;
+ case FCmpInst::FCMP_UGT: return ISD::SETUGT;
+ case FCmpInst::FCMP_UGE: return ISD::SETUGE;
+ case FCmpInst::FCMP_ULT: return ISD::SETULT;
+ case FCmpInst::FCMP_ULE: return ISD::SETULE;
+ case FCmpInst::FCMP_UNE: return ISD::SETUNE;
+ case FCmpInst::FCMP_TRUE: return ISD::SETTRUE;
+ default: llvm_unreachable("Invalid FCmp predicate opcode!");
+ }
+}
+
+ISD::CondCode llvm::getFCmpCodeWithoutNaN(ISD::CondCode CC) {
+ switch (CC) {
+ case ISD::SETOEQ: case ISD::SETUEQ: return ISD::SETEQ;
+ case ISD::SETONE: case ISD::SETUNE: return ISD::SETNE;
+ case ISD::SETOLT: case ISD::SETULT: return ISD::SETLT;
+ case ISD::SETOLE: case ISD::SETULE: return ISD::SETLE;
+ case ISD::SETOGT: case ISD::SETUGT: return ISD::SETGT;
+ case ISD::SETOGE: case ISD::SETUGE: return ISD::SETGE;
+ default: return CC;
+ }
+}
+
+/// getICmpCondCode - Return the ISD condition code corresponding to
+/// the given LLVM IR integer condition code.
+///
+ISD::CondCode llvm::getICmpCondCode(ICmpInst::Predicate Pred) {
+ switch (Pred) {
+ case ICmpInst::ICMP_EQ: return ISD::SETEQ;
+ case ICmpInst::ICMP_NE: return ISD::SETNE;
+ case ICmpInst::ICMP_SLE: return ISD::SETLE;
+ case ICmpInst::ICMP_ULE: return ISD::SETULE;
+ case ICmpInst::ICMP_SGE: return ISD::SETGE;
+ case ICmpInst::ICMP_UGE: return ISD::SETUGE;
+ case ICmpInst::ICMP_SLT: return ISD::SETLT;
+ case ICmpInst::ICMP_ULT: return ISD::SETULT;
+ case ICmpInst::ICMP_SGT: return ISD::SETGT;
+ case ICmpInst::ICMP_UGT: return ISD::SETUGT;
+ default:
+ llvm_unreachable("Invalid ICmp predicate opcode!");
+ }
+}
+
+static bool isNoopBitcast(Type *T1, Type *T2,
+ 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)));
+}
+
+/// 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) {
+ while (true) {
+ // Try to look through V1; if V1 is not an instruction, it can't be looked
+ // through.
+ const Instruction *I = dyn_cast<Instruction>(V);
+ if (!I || I->getNumOperands() == 0) return V;
+ const Value *NoopInput = 0;
+
+ 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()) &&
+ TLI.getPointerTy().getSizeInBits() ==
+ 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() ==
+ cast<IntegerType>(I->getType())->getBitWidth())
+ 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 (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 (std::equal(InsertLoc.rbegin(), InsertLoc.rend(),
+ 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();
+ std::copy(ExtractLoc.rbegin(), ExtractLoc.rend(),
+ std::back_inserter(ValLoc));
+ NoopInput = Op;
+ }
+ // Terminate if we couldn't find anything to look through.
+ if (!NoopInput)
+ return V;
+
+ 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) {
+
+ // 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);
+
+ // 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);
+
+ // 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;
+
+ 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();
+}
+
+/// 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();
+ }
+
+ // 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);
+
+ DeeperType = CT->getTypeAtIndex(0U);
+ }
+
+ 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) {
+ const Instruction *I = CS.getInstruction();
+ const BasicBlock *ExitBB = I->getParent();
+ const TerminatorInst *Term = ExitBB->getTerminator();
+ const ReturnInst *Ret = dyn_cast<ReturnInst>(Term);
+
+ // The block must end in a return statement or unreachable.
+ //
+ // FIXME: Decline tailcall if it's not guaranteed and if the block ends in
+ // an unreachable, for now. The way tailcall optimization is currently
+ // implemented means it will add an epilogue followed by a jump. That is
+ // not profitable. Also, if the callee is a special function (e.g.
+ // longjmp on x86), it can end up causing miscompilation that has not
+ // been fully understood.
+ if (!Ret &&
+ (!TLI.getTargetMachine().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) {
+ if (&*BBI == I)
+ break;
+ // Debug info intrinsics do not get in the way of tail call optimization.
+ if (isa<DbgInfoIntrinsic>(BBI))
+ continue;
+ if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() ||
+ !isSafeToSpeculativelyExecute(BBI))
+ return false;
+ }
+
+ return returnTypeIsEligibleForTailCall(ExitBB->getParent(), I, Ret, TLI);
+}
+
+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;
+
+ // If the return value is undef, it doesn't matter what the call's
+ // return type is.
+ if (isa<UndefValue>(Ret->getOperand(0))) return true;
+
+ // 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.
+ using std::copy;
+ SmallVector<unsigned, 4> TmpRetPath, TmpCallPath;
+ copy(RetPath.rbegin(), RetPath.rend(), std::back_inserter(TmpRetPath));
+ copy(CallPath.rbegin(), CallPath.rend(), std::back_inserter(TmpCallPath));
+
+ // 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))
+ return false;
+
+ CallEmpty = !nextRealType(CallSubTypes, CallPath);
+ } while(nextRealType(RetSubTypes, RetPath));
+
+ return true;
+}
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