//===-- 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 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/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(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, nullptr, nullptr, CurIndex); } return CurIndex; } // Given an array type, recursively traverse the elements. else if (ArrayType *ATy = dyn_cast(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, nullptr, nullptr, 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 &ValueVTs, SmallVectorImpl *Offsets, uint64_t StartingOffset) { // Given a struct type, recursively traverse the elements. if (StructType *STy = dyn_cast(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(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(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(Init); if (!GV) V = cast(Init); } assert((GV || isa(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(T1) && isa(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 &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(V); if (!I || I->getNumOperands() == 0) return V; const Value *NoopInput = nullptr; Value *Op = I->getOperand(0); if (isa(I)) { // Look through truly no-op bitcasts. if (isNoopBitcast(Op->getType(), I->getType(), TLI)) NoopInput = Op; } else if (isa(I)) { // Look through getelementptr if (cast(I)->hasAllZeroIndices()) NoopInput = Op; } else if (isa(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(I->getType()) && TLI.getPointerTy().getSizeInBits() == cast(Op->getType())->getBitWidth()) NoopInput = Op; } else if (isa(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(I->getType()) && TLI.getPointerTy().getSizeInBits() == cast(I->getType())->getBitWidth()) NoopInput = Op; } else if (isa(I) && TLI.allowTruncateForTailCall(Op->getType(), I->getType())) { DataBits = std::min(DataBits, I->getType()->getPrimitiveSizeInBits()); NoopInput = Op; } else if (isa(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(I)->paramHasAttr(attrInd, Attribute::Returned) && isNoopBitcast((*i)->getType(), I->getType(), TLI)) { NoopInput = *i; break; } } } else if (isa(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(I)->paramHasAttr(attrInd, Attribute::Returned) && isNoopBitcast((*i)->getType(), I->getType(), TLI)) { NoopInput = *i; break; } } } else if (const InsertValueInst *IVI = dyn_cast(V)) { // Value may come from either the aggregate or the scalar ArrayRef 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(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 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 &RetIndices, SmallVectorImpl &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(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(T)) return Idx < AT->getNumElements(); return Idx < cast(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 &SubTypes, SmallVectorImpl &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(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 &SubTypes, SmallVectorImpl &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(Next), 0)) { SubTypes.push_back(cast(Next)); Path.push_back(0); Next = cast(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 &SubTypes, SmallVectorImpl &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 TargetMachine &TM) { const Instruction *I = CS.getInstruction(); const BasicBlock *ExitBB = I->getParent(); const TerminatorInst *Term = ExitBB->getTerminator(); const ReturnInst *Ret = dyn_cast(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 && (!TM.Options.GuaranteedTailCallOpt || !isa(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 = std::prev(ExitBB->end(), 2);; --BBI) { if (&*BBI == I) break; // Debug info intrinsics do not get in the way of tail call optimization. if (isa(BBI)) continue; if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() || !isSafeToSpeculativelyExecute(BBI)) return false; } return returnTypeIsEligibleForTailCall(ExitBB->getParent(), I, Ret, *TM.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; // If the return value is undef, it doesn't matter what the call's // return type is. if (isa(Ret->getOperand(0))) return true; // Make sure the attributes attached to each return are compatible. AttrBuilder CallerAttrs(F->getAttributes(), AttributeSet::ReturnIndex); AttrBuilder CalleeAttrs(cast(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 RetPath, CallPath; SmallVector 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 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; }