| //===- InstCombineCasts.cpp -----------------------------------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements the visit functions for cast operations. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "InstCombine.h" |
| #include "llvm/Analysis/ConstantFolding.h" |
| #include "llvm/Target/TargetData.h" |
| #include "llvm/Support/PatternMatch.h" |
| using namespace llvm; |
| using namespace PatternMatch; |
| |
| /// DecomposeSimpleLinearExpr - Analyze 'Val', seeing if it is a simple linear |
| /// expression. If so, decompose it, returning some value X, such that Val is |
| /// X*Scale+Offset. |
| /// |
| static Value *DecomposeSimpleLinearExpr(Value *Val, unsigned &Scale, |
| uint64_t &Offset) { |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(Val)) { |
| Offset = CI->getZExtValue(); |
| Scale = 0; |
| return ConstantInt::get(Val->getType(), 0); |
| } |
| |
| if (BinaryOperator *I = dyn_cast<BinaryOperator>(Val)) { |
| // Cannot look past anything that might overflow. |
| OverflowingBinaryOperator *OBI = dyn_cast<OverflowingBinaryOperator>(Val); |
| if (OBI && !OBI->hasNoUnsignedWrap()) { |
| Scale = 1; |
| Offset = 0; |
| return Val; |
| } |
| |
| if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) { |
| if (I->getOpcode() == Instruction::Shl) { |
| // This is a value scaled by '1 << the shift amt'. |
| Scale = UINT64_C(1) << RHS->getZExtValue(); |
| Offset = 0; |
| return I->getOperand(0); |
| } |
| |
| if (I->getOpcode() == Instruction::Mul) { |
| // This value is scaled by 'RHS'. |
| Scale = RHS->getZExtValue(); |
| Offset = 0; |
| return I->getOperand(0); |
| } |
| |
| if (I->getOpcode() == Instruction::Add) { |
| // We have X+C. Check to see if we really have (X*C2)+C1, |
| // where C1 is divisible by C2. |
| unsigned SubScale; |
| Value *SubVal = |
| DecomposeSimpleLinearExpr(I->getOperand(0), SubScale, Offset); |
| Offset += RHS->getZExtValue(); |
| Scale = SubScale; |
| return SubVal; |
| } |
| } |
| } |
| |
| // Otherwise, we can't look past this. |
| Scale = 1; |
| Offset = 0; |
| return Val; |
| } |
| |
| /// PromoteCastOfAllocation - If we find a cast of an allocation instruction, |
| /// try to eliminate the cast by moving the type information into the alloc. |
| Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI, |
| AllocaInst &AI) { |
| // This requires TargetData to get the alloca alignment and size information. |
| if (!TD) return 0; |
| |
| PointerType *PTy = cast<PointerType>(CI.getType()); |
| |
| BuilderTy AllocaBuilder(*Builder); |
| AllocaBuilder.SetInsertPoint(AI.getParent(), &AI); |
| |
| // Get the type really allocated and the type casted to. |
| Type *AllocElTy = AI.getAllocatedType(); |
| Type *CastElTy = PTy->getElementType(); |
| if (!AllocElTy->isSized() || !CastElTy->isSized()) return 0; |
| |
| unsigned AllocElTyAlign = TD->getABITypeAlignment(AllocElTy); |
| unsigned CastElTyAlign = TD->getABITypeAlignment(CastElTy); |
| if (CastElTyAlign < AllocElTyAlign) return 0; |
| |
| // If the allocation has multiple uses, only promote it if we are strictly |
| // increasing the alignment of the resultant allocation. If we keep it the |
| // same, we open the door to infinite loops of various kinds. |
| if (!AI.hasOneUse() && CastElTyAlign == AllocElTyAlign) return 0; |
| |
| uint64_t AllocElTySize = TD->getTypeAllocSize(AllocElTy); |
| uint64_t CastElTySize = TD->getTypeAllocSize(CastElTy); |
| if (CastElTySize == 0 || AllocElTySize == 0) return 0; |
| |
| // See if we can satisfy the modulus by pulling a scale out of the array |
| // size argument. |
| unsigned ArraySizeScale; |
| uint64_t ArrayOffset; |
| Value *NumElements = // See if the array size is a decomposable linear expr. |
| DecomposeSimpleLinearExpr(AI.getOperand(0), ArraySizeScale, ArrayOffset); |
| |
| // If we can now satisfy the modulus, by using a non-1 scale, we really can |
| // do the xform. |
| if ((AllocElTySize*ArraySizeScale) % CastElTySize != 0 || |
| (AllocElTySize*ArrayOffset ) % CastElTySize != 0) return 0; |
| |
| unsigned Scale = (AllocElTySize*ArraySizeScale)/CastElTySize; |
| Value *Amt = 0; |
| if (Scale == 1) { |
| Amt = NumElements; |
| } else { |
| Amt = ConstantInt::get(AI.getArraySize()->getType(), Scale); |
| // Insert before the alloca, not before the cast. |
| Amt = AllocaBuilder.CreateMul(Amt, NumElements, "tmp"); |
| } |
| |
| if (uint64_t Offset = (AllocElTySize*ArrayOffset)/CastElTySize) { |
| Value *Off = ConstantInt::get(AI.getArraySize()->getType(), |
| Offset, true); |
| Amt = AllocaBuilder.CreateAdd(Amt, Off, "tmp"); |
| } |
| |
| AllocaInst *New = AllocaBuilder.CreateAlloca(CastElTy, Amt); |
| New->setAlignment(AI.getAlignment()); |
| New->takeName(&AI); |
| |
| // If the allocation has multiple real uses, insert a cast and change all |
| // things that used it to use the new cast. This will also hack on CI, but it |
| // will die soon. |
| if (!AI.hasOneUse()) { |
| // New is the allocation instruction, pointer typed. AI is the original |
| // allocation instruction, also pointer typed. Thus, cast to use is BitCast. |
| Value *NewCast = AllocaBuilder.CreateBitCast(New, AI.getType(), "tmpcast"); |
| ReplaceInstUsesWith(AI, NewCast); |
| } |
| return ReplaceInstUsesWith(CI, New); |
| } |
| |
| |
| |
| /// EvaluateInDifferentType - Given an expression that |
| /// CanEvaluateTruncated or CanEvaluateSExtd returns true for, actually |
| /// insert the code to evaluate the expression. |
| Value *InstCombiner::EvaluateInDifferentType(Value *V, Type *Ty, |
| bool isSigned) { |
| if (Constant *C = dyn_cast<Constant>(V)) { |
| C = ConstantExpr::getIntegerCast(C, Ty, isSigned /*Sext or ZExt*/); |
| // If we got a constantexpr back, try to simplify it with TD info. |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) |
| C = ConstantFoldConstantExpression(CE, TD); |
| return C; |
| } |
| |
| // Otherwise, it must be an instruction. |
| Instruction *I = cast<Instruction>(V); |
| Instruction *Res = 0; |
| unsigned Opc = I->getOpcode(); |
| switch (Opc) { |
| case Instruction::Add: |
| case Instruction::Sub: |
| case Instruction::Mul: |
| case Instruction::And: |
| case Instruction::Or: |
| case Instruction::Xor: |
| case Instruction::AShr: |
| case Instruction::LShr: |
| case Instruction::Shl: |
| case Instruction::UDiv: |
| case Instruction::URem: { |
| Value *LHS = EvaluateInDifferentType(I->getOperand(0), Ty, isSigned); |
| Value *RHS = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned); |
| Res = BinaryOperator::Create((Instruction::BinaryOps)Opc, LHS, RHS); |
| break; |
| } |
| case Instruction::Trunc: |
| case Instruction::ZExt: |
| case Instruction::SExt: |
| // If the source type of the cast is the type we're trying for then we can |
| // just return the source. There's no need to insert it because it is not |
| // new. |
| if (I->getOperand(0)->getType() == Ty) |
| return I->getOperand(0); |
| |
| // Otherwise, must be the same type of cast, so just reinsert a new one. |
| // This also handles the case of zext(trunc(x)) -> zext(x). |
| Res = CastInst::CreateIntegerCast(I->getOperand(0), Ty, |
| Opc == Instruction::SExt); |
| break; |
| case Instruction::Select: { |
| Value *True = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned); |
| Value *False = EvaluateInDifferentType(I->getOperand(2), Ty, isSigned); |
| Res = SelectInst::Create(I->getOperand(0), True, False); |
| break; |
| } |
| case Instruction::PHI: { |
| PHINode *OPN = cast<PHINode>(I); |
| PHINode *NPN = PHINode::Create(Ty, OPN->getNumIncomingValues()); |
| for (unsigned i = 0, e = OPN->getNumIncomingValues(); i != e; ++i) { |
| Value *V =EvaluateInDifferentType(OPN->getIncomingValue(i), Ty, isSigned); |
| NPN->addIncoming(V, OPN->getIncomingBlock(i)); |
| } |
| Res = NPN; |
| break; |
| } |
| default: |
| // TODO: Can handle more cases here. |
| llvm_unreachable("Unreachable!"); |
| break; |
| } |
| |
| Res->takeName(I); |
| return InsertNewInstWith(Res, *I); |
| } |
| |
| |
| /// This function is a wrapper around CastInst::isEliminableCastPair. It |
| /// simply extracts arguments and returns what that function returns. |
| static Instruction::CastOps |
| isEliminableCastPair( |
| const CastInst *CI, ///< The first cast instruction |
| unsigned opcode, ///< The opcode of the second cast instruction |
| Type *DstTy, ///< The target type for the second cast instruction |
| TargetData *TD ///< The target data for pointer size |
| ) { |
| |
| Type *SrcTy = CI->getOperand(0)->getType(); // A from above |
| Type *MidTy = CI->getType(); // B from above |
| |
| // Get the opcodes of the two Cast instructions |
| Instruction::CastOps firstOp = Instruction::CastOps(CI->getOpcode()); |
| Instruction::CastOps secondOp = Instruction::CastOps(opcode); |
| |
| unsigned Res = CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, |
| DstTy, |
| TD ? TD->getIntPtrType(CI->getContext()) : 0); |
| |
| // We don't want to form an inttoptr or ptrtoint that converts to an integer |
| // type that differs from the pointer size. |
| if ((Res == Instruction::IntToPtr && |
| (!TD || SrcTy != TD->getIntPtrType(CI->getContext()))) || |
| (Res == Instruction::PtrToInt && |
| (!TD || DstTy != TD->getIntPtrType(CI->getContext())))) |
| Res = 0; |
| |
| return Instruction::CastOps(Res); |
| } |
| |
| /// ShouldOptimizeCast - Return true if the cast from "V to Ty" actually |
| /// results in any code being generated and is interesting to optimize out. If |
| /// the cast can be eliminated by some other simple transformation, we prefer |
| /// to do the simplification first. |
| bool InstCombiner::ShouldOptimizeCast(Instruction::CastOps opc, const Value *V, |
| Type *Ty) { |
| // Noop casts and casts of constants should be eliminated trivially. |
| if (V->getType() == Ty || isa<Constant>(V)) return false; |
| |
| // If this is another cast that can be eliminated, we prefer to have it |
| // eliminated. |
| if (const CastInst *CI = dyn_cast<CastInst>(V)) |
| if (isEliminableCastPair(CI, opc, Ty, TD)) |
| return false; |
| |
| // If this is a vector sext from a compare, then we don't want to break the |
| // idiom where each element of the extended vector is either zero or all ones. |
| if (opc == Instruction::SExt && isa<CmpInst>(V) && Ty->isVectorTy()) |
| return false; |
| |
| return true; |
| } |
| |
| |
| /// @brief Implement the transforms common to all CastInst visitors. |
| Instruction *InstCombiner::commonCastTransforms(CastInst &CI) { |
| Value *Src = CI.getOperand(0); |
| |
| // Many cases of "cast of a cast" are eliminable. If it's eliminable we just |
| // eliminate it now. |
| if (CastInst *CSrc = dyn_cast<CastInst>(Src)) { // A->B->C cast |
| if (Instruction::CastOps opc = |
| isEliminableCastPair(CSrc, CI.getOpcode(), CI.getType(), TD)) { |
| // The first cast (CSrc) is eliminable so we need to fix up or replace |
| // the second cast (CI). CSrc will then have a good chance of being dead. |
| return CastInst::Create(opc, CSrc->getOperand(0), CI.getType()); |
| } |
| } |
| |
| // If we are casting a select then fold the cast into the select |
| if (SelectInst *SI = dyn_cast<SelectInst>(Src)) |
| if (Instruction *NV = FoldOpIntoSelect(CI, SI)) |
| return NV; |
| |
| // If we are casting a PHI then fold the cast into the PHI |
| if (isa<PHINode>(Src)) { |
| // We don't do this if this would create a PHI node with an illegal type if |
| // it is currently legal. |
| if (!Src->getType()->isIntegerTy() || |
| !CI.getType()->isIntegerTy() || |
| ShouldChangeType(CI.getType(), Src->getType())) |
| if (Instruction *NV = FoldOpIntoPhi(CI)) |
| return NV; |
| } |
| |
| return 0; |
| } |
| |
| /// CanEvaluateTruncated - Return true if we can evaluate the specified |
| /// expression tree as type Ty instead of its larger type, and arrive with the |
| /// same value. This is used by code that tries to eliminate truncates. |
| /// |
| /// Ty will always be a type smaller than V. We should return true if trunc(V) |
| /// can be computed by computing V in the smaller type. If V is an instruction, |
| /// then trunc(inst(x,y)) can be computed as inst(trunc(x),trunc(y)), which only |
| /// makes sense if x and y can be efficiently truncated. |
| /// |
| /// This function works on both vectors and scalars. |
| /// |
| static bool CanEvaluateTruncated(Value *V, Type *Ty) { |
| // We can always evaluate constants in another type. |
| if (isa<Constant>(V)) |
| return true; |
| |
| Instruction *I = dyn_cast<Instruction>(V); |
| if (!I) return false; |
| |
| Type *OrigTy = V->getType(); |
| |
| // If this is an extension from the dest type, we can eliminate it, even if it |
| // has multiple uses. |
| if ((isa<ZExtInst>(I) || isa<SExtInst>(I)) && |
| I->getOperand(0)->getType() == Ty) |
| return true; |
| |
| // We can't extend or shrink something that has multiple uses: doing so would |
| // require duplicating the instruction in general, which isn't profitable. |
| if (!I->hasOneUse()) return false; |
| |
| unsigned Opc = I->getOpcode(); |
| switch (Opc) { |
| case Instruction::Add: |
| case Instruction::Sub: |
| case Instruction::Mul: |
| case Instruction::And: |
| case Instruction::Or: |
| case Instruction::Xor: |
| // These operators can all arbitrarily be extended or truncated. |
| return CanEvaluateTruncated(I->getOperand(0), Ty) && |
| CanEvaluateTruncated(I->getOperand(1), Ty); |
| |
| case Instruction::UDiv: |
| case Instruction::URem: { |
| // UDiv and URem can be truncated if all the truncated bits are zero. |
| uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits(); |
| uint32_t BitWidth = Ty->getScalarSizeInBits(); |
| if (BitWidth < OrigBitWidth) { |
| APInt Mask = APInt::getHighBitsSet(OrigBitWidth, OrigBitWidth-BitWidth); |
| if (MaskedValueIsZero(I->getOperand(0), Mask) && |
| MaskedValueIsZero(I->getOperand(1), Mask)) { |
| return CanEvaluateTruncated(I->getOperand(0), Ty) && |
| CanEvaluateTruncated(I->getOperand(1), Ty); |
| } |
| } |
| break; |
| } |
| case Instruction::Shl: |
| // If we are truncating the result of this SHL, and if it's a shift of a |
| // constant amount, we can always perform a SHL in a smaller type. |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) { |
| uint32_t BitWidth = Ty->getScalarSizeInBits(); |
| if (CI->getLimitedValue(BitWidth) < BitWidth) |
| return CanEvaluateTruncated(I->getOperand(0), Ty); |
| } |
| break; |
| case Instruction::LShr: |
| // If this is a truncate of a logical shr, we can truncate it to a smaller |
| // lshr iff we know that the bits we would otherwise be shifting in are |
| // already zeros. |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) { |
| uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits(); |
| uint32_t BitWidth = Ty->getScalarSizeInBits(); |
| if (MaskedValueIsZero(I->getOperand(0), |
| APInt::getHighBitsSet(OrigBitWidth, OrigBitWidth-BitWidth)) && |
| CI->getLimitedValue(BitWidth) < BitWidth) { |
| return CanEvaluateTruncated(I->getOperand(0), Ty); |
| } |
| } |
| break; |
| case Instruction::Trunc: |
| // trunc(trunc(x)) -> trunc(x) |
| return true; |
| case Instruction::ZExt: |
| case Instruction::SExt: |
| // trunc(ext(x)) -> ext(x) if the source type is smaller than the new dest |
| // trunc(ext(x)) -> trunc(x) if the source type is larger than the new dest |
| return true; |
| case Instruction::Select: { |
| SelectInst *SI = cast<SelectInst>(I); |
| return CanEvaluateTruncated(SI->getTrueValue(), Ty) && |
| CanEvaluateTruncated(SI->getFalseValue(), Ty); |
| } |
| case Instruction::PHI: { |
| // We can change a phi if we can change all operands. Note that we never |
| // get into trouble with cyclic PHIs here because we only consider |
| // instructions with a single use. |
| PHINode *PN = cast<PHINode>(I); |
| for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) |
| if (!CanEvaluateTruncated(PN->getIncomingValue(i), Ty)) |
| return false; |
| return true; |
| } |
| default: |
| // TODO: Can handle more cases here. |
| break; |
| } |
| |
| return false; |
| } |
| |
| Instruction *InstCombiner::visitTrunc(TruncInst &CI) { |
| if (Instruction *Result = commonCastTransforms(CI)) |
| return Result; |
| |
| // See if we can simplify any instructions used by the input whose sole |
| // purpose is to compute bits we don't care about. |
| if (SimplifyDemandedInstructionBits(CI)) |
| return &CI; |
| |
| Value *Src = CI.getOperand(0); |
| Type *DestTy = CI.getType(), *SrcTy = Src->getType(); |
| |
| // Attempt to truncate the entire input expression tree to the destination |
| // type. Only do this if the dest type is a simple type, don't convert the |
| // expression tree to something weird like i93 unless the source is also |
| // strange. |
| if ((DestTy->isVectorTy() || ShouldChangeType(SrcTy, DestTy)) && |
| CanEvaluateTruncated(Src, DestTy)) { |
| |
| // If this cast is a truncate, evaluting in a different type always |
| // eliminates the cast, so it is always a win. |
| DEBUG(dbgs() << "ICE: EvaluateInDifferentType converting expression type" |
| " to avoid cast: " << CI << '\n'); |
| Value *Res = EvaluateInDifferentType(Src, DestTy, false); |
| assert(Res->getType() == DestTy); |
| return ReplaceInstUsesWith(CI, Res); |
| } |
| |
| // Canonicalize trunc x to i1 -> (icmp ne (and x, 1), 0), likewise for vector. |
| if (DestTy->getScalarSizeInBits() == 1) { |
| Constant *One = ConstantInt::get(Src->getType(), 1); |
| Src = Builder->CreateAnd(Src, One, "tmp"); |
| Value *Zero = Constant::getNullValue(Src->getType()); |
| return new ICmpInst(ICmpInst::ICMP_NE, Src, Zero); |
| } |
| |
| // Transform trunc(lshr (zext A), Cst) to eliminate one type conversion. |
| Value *A = 0; ConstantInt *Cst = 0; |
| if (Src->hasOneUse() && |
| match(Src, m_LShr(m_ZExt(m_Value(A)), m_ConstantInt(Cst)))) { |
| // We have three types to worry about here, the type of A, the source of |
| // the truncate (MidSize), and the destination of the truncate. We know that |
| // ASize < MidSize and MidSize > ResultSize, but don't know the relation |
| // between ASize and ResultSize. |
| unsigned ASize = A->getType()->getPrimitiveSizeInBits(); |
| |
| // If the shift amount is larger than the size of A, then the result is |
| // known to be zero because all the input bits got shifted out. |
| if (Cst->getZExtValue() >= ASize) |
| return ReplaceInstUsesWith(CI, Constant::getNullValue(CI.getType())); |
| |
| // Since we're doing an lshr and a zero extend, and know that the shift |
| // amount is smaller than ASize, it is always safe to do the shift in A's |
| // type, then zero extend or truncate to the result. |
| Value *Shift = Builder->CreateLShr(A, Cst->getZExtValue()); |
| Shift->takeName(Src); |
| return CastInst::CreateIntegerCast(Shift, CI.getType(), false); |
| } |
| |
| // Transform "trunc (and X, cst)" -> "and (trunc X), cst" so long as the dest |
| // type isn't non-native. |
| if (Src->hasOneUse() && isa<IntegerType>(Src->getType()) && |
| ShouldChangeType(Src->getType(), CI.getType()) && |
| match(Src, m_And(m_Value(A), m_ConstantInt(Cst)))) { |
| Value *NewTrunc = Builder->CreateTrunc(A, CI.getType(), A->getName()+".tr"); |
| return BinaryOperator::CreateAnd(NewTrunc, |
| ConstantExpr::getTrunc(Cst, CI.getType())); |
| } |
| |
| return 0; |
| } |
| |
| /// transformZExtICmp - Transform (zext icmp) to bitwise / integer operations |
| /// in order to eliminate the icmp. |
| Instruction *InstCombiner::transformZExtICmp(ICmpInst *ICI, Instruction &CI, |
| bool DoXform) { |
| // If we are just checking for a icmp eq of a single bit and zext'ing it |
| // to an integer, then shift the bit to the appropriate place and then |
| // cast to integer to avoid the comparison. |
| if (ConstantInt *Op1C = dyn_cast<ConstantInt>(ICI->getOperand(1))) { |
| const APInt &Op1CV = Op1C->getValue(); |
| |
| // zext (x <s 0) to i32 --> x>>u31 true if signbit set. |
| // zext (x >s -1) to i32 --> (x>>u31)^1 true if signbit clear. |
| if ((ICI->getPredicate() == ICmpInst::ICMP_SLT && Op1CV == 0) || |
| (ICI->getPredicate() == ICmpInst::ICMP_SGT &&Op1CV.isAllOnesValue())) { |
| if (!DoXform) return ICI; |
| |
| Value *In = ICI->getOperand(0); |
| Value *Sh = ConstantInt::get(In->getType(), |
| In->getType()->getScalarSizeInBits()-1); |
| In = Builder->CreateLShr(In, Sh, In->getName()+".lobit"); |
| if (In->getType() != CI.getType()) |
| In = Builder->CreateIntCast(In, CI.getType(), false/*ZExt*/, "tmp"); |
| |
| if (ICI->getPredicate() == ICmpInst::ICMP_SGT) { |
| Constant *One = ConstantInt::get(In->getType(), 1); |
| In = Builder->CreateXor(In, One, In->getName()+".not"); |
| } |
| |
| return ReplaceInstUsesWith(CI, In); |
| } |
| |
| |
| |
| // zext (X == 0) to i32 --> X^1 iff X has only the low bit set. |
| // zext (X == 0) to i32 --> (X>>1)^1 iff X has only the 2nd bit set. |
| // zext (X == 1) to i32 --> X iff X has only the low bit set. |
| // zext (X == 2) to i32 --> X>>1 iff X has only the 2nd bit set. |
| // zext (X != 0) to i32 --> X iff X has only the low bit set. |
| // zext (X != 0) to i32 --> X>>1 iff X has only the 2nd bit set. |
| // zext (X != 1) to i32 --> X^1 iff X has only the low bit set. |
| // zext (X != 2) to i32 --> (X>>1)^1 iff X has only the 2nd bit set. |
| if ((Op1CV == 0 || Op1CV.isPowerOf2()) && |
| // This only works for EQ and NE |
| ICI->isEquality()) { |
| // If Op1C some other power of two, convert: |
| uint32_t BitWidth = Op1C->getType()->getBitWidth(); |
| APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0); |
| APInt TypeMask(APInt::getAllOnesValue(BitWidth)); |
| ComputeMaskedBits(ICI->getOperand(0), TypeMask, KnownZero, KnownOne); |
| |
| APInt KnownZeroMask(~KnownZero); |
| if (KnownZeroMask.isPowerOf2()) { // Exactly 1 possible 1? |
| if (!DoXform) return ICI; |
| |
| bool isNE = ICI->getPredicate() == ICmpInst::ICMP_NE; |
| if (Op1CV != 0 && (Op1CV != KnownZeroMask)) { |
| // (X&4) == 2 --> false |
| // (X&4) != 2 --> true |
| Constant *Res = ConstantInt::get(Type::getInt1Ty(CI.getContext()), |
| isNE); |
| Res = ConstantExpr::getZExt(Res, CI.getType()); |
| return ReplaceInstUsesWith(CI, Res); |
| } |
| |
| uint32_t ShiftAmt = KnownZeroMask.logBase2(); |
| Value *In = ICI->getOperand(0); |
| if (ShiftAmt) { |
| // Perform a logical shr by shiftamt. |
| // Insert the shift to put the result in the low bit. |
| In = Builder->CreateLShr(In, ConstantInt::get(In->getType(),ShiftAmt), |
| In->getName()+".lobit"); |
| } |
| |
| if ((Op1CV != 0) == isNE) { // Toggle the low bit. |
| Constant *One = ConstantInt::get(In->getType(), 1); |
| In = Builder->CreateXor(In, One, "tmp"); |
| } |
| |
| if (CI.getType() == In->getType()) |
| return ReplaceInstUsesWith(CI, In); |
| return CastInst::CreateIntegerCast(In, CI.getType(), false/*ZExt*/); |
| } |
| } |
| } |
| |
| // icmp ne A, B is equal to xor A, B when A and B only really have one bit. |
| // It is also profitable to transform icmp eq into not(xor(A, B)) because that |
| // may lead to additional simplifications. |
| if (ICI->isEquality() && CI.getType() == ICI->getOperand(0)->getType()) { |
| if (IntegerType *ITy = dyn_cast<IntegerType>(CI.getType())) { |
| uint32_t BitWidth = ITy->getBitWidth(); |
| Value *LHS = ICI->getOperand(0); |
| Value *RHS = ICI->getOperand(1); |
| |
| APInt KnownZeroLHS(BitWidth, 0), KnownOneLHS(BitWidth, 0); |
| APInt KnownZeroRHS(BitWidth, 0), KnownOneRHS(BitWidth, 0); |
| APInt TypeMask(APInt::getAllOnesValue(BitWidth)); |
| ComputeMaskedBits(LHS, TypeMask, KnownZeroLHS, KnownOneLHS); |
| ComputeMaskedBits(RHS, TypeMask, KnownZeroRHS, KnownOneRHS); |
| |
| if (KnownZeroLHS == KnownZeroRHS && KnownOneLHS == KnownOneRHS) { |
| APInt KnownBits = KnownZeroLHS | KnownOneLHS; |
| APInt UnknownBit = ~KnownBits; |
| if (UnknownBit.countPopulation() == 1) { |
| if (!DoXform) return ICI; |
| |
| Value *Result = Builder->CreateXor(LHS, RHS); |
| |
| // Mask off any bits that are set and won't be shifted away. |
| if (KnownOneLHS.uge(UnknownBit)) |
| Result = Builder->CreateAnd(Result, |
| ConstantInt::get(ITy, UnknownBit)); |
| |
| // Shift the bit we're testing down to the lsb. |
| Result = Builder->CreateLShr( |
| Result, ConstantInt::get(ITy, UnknownBit.countTrailingZeros())); |
| |
| if (ICI->getPredicate() == ICmpInst::ICMP_EQ) |
| Result = Builder->CreateXor(Result, ConstantInt::get(ITy, 1)); |
| Result->takeName(ICI); |
| return ReplaceInstUsesWith(CI, Result); |
| } |
| } |
| } |
| } |
| |
| return 0; |
| } |
| |
| /// CanEvaluateZExtd - Determine if the specified value can be computed in the |
| /// specified wider type and produce the same low bits. If not, return false. |
| /// |
| /// If this function returns true, it can also return a non-zero number of bits |
| /// (in BitsToClear) which indicates that the value it computes is correct for |
| /// the zero extend, but that the additional BitsToClear bits need to be zero'd |
| /// out. For example, to promote something like: |
| /// |
| /// %B = trunc i64 %A to i32 |
| /// %C = lshr i32 %B, 8 |
| /// %E = zext i32 %C to i64 |
| /// |
| /// CanEvaluateZExtd for the 'lshr' will return true, and BitsToClear will be |
| /// set to 8 to indicate that the promoted value needs to have bits 24-31 |
| /// cleared in addition to bits 32-63. Since an 'and' will be generated to |
| /// clear the top bits anyway, doing this has no extra cost. |
| /// |
| /// This function works on both vectors and scalars. |
| static bool CanEvaluateZExtd(Value *V, Type *Ty, unsigned &BitsToClear) { |
| BitsToClear = 0; |
| if (isa<Constant>(V)) |
| return true; |
| |
| Instruction *I = dyn_cast<Instruction>(V); |
| if (!I) return false; |
| |
| // If the input is a truncate from the destination type, we can trivially |
| // eliminate it, even if it has multiple uses. |
| // FIXME: This is currently disabled until codegen can handle this without |
| // pessimizing code, PR5997. |
| if (0 && isa<TruncInst>(I) && I->getOperand(0)->getType() == Ty) |
| return true; |
| |
| // We can't extend or shrink something that has multiple uses: doing so would |
| // require duplicating the instruction in general, which isn't profitable. |
| if (!I->hasOneUse()) return false; |
| |
| unsigned Opc = I->getOpcode(), Tmp; |
| switch (Opc) { |
| case Instruction::ZExt: // zext(zext(x)) -> zext(x). |
| case Instruction::SExt: // zext(sext(x)) -> sext(x). |
| case Instruction::Trunc: // zext(trunc(x)) -> trunc(x) or zext(x) |
| return true; |
| case Instruction::And: |
| case Instruction::Or: |
| case Instruction::Xor: |
| case Instruction::Add: |
| case Instruction::Sub: |
| case Instruction::Mul: |
| case Instruction::Shl: |
| if (!CanEvaluateZExtd(I->getOperand(0), Ty, BitsToClear) || |
| !CanEvaluateZExtd(I->getOperand(1), Ty, Tmp)) |
| return false; |
| // These can all be promoted if neither operand has 'bits to clear'. |
| if (BitsToClear == 0 && Tmp == 0) |
| return true; |
| |
| // If the operation is an AND/OR/XOR and the bits to clear are zero in the |
| // other side, BitsToClear is ok. |
| if (Tmp == 0 && |
| (Opc == Instruction::And || Opc == Instruction::Or || |
| Opc == Instruction::Xor)) { |
| // We use MaskedValueIsZero here for generality, but the case we care |
| // about the most is constant RHS. |
| unsigned VSize = V->getType()->getScalarSizeInBits(); |
| if (MaskedValueIsZero(I->getOperand(1), |
| APInt::getHighBitsSet(VSize, BitsToClear))) |
| return true; |
| } |
| |
| // Otherwise, we don't know how to analyze this BitsToClear case yet. |
| return false; |
| |
| case Instruction::LShr: |
| // We can promote lshr(x, cst) if we can promote x. This requires the |
| // ultimate 'and' to clear out the high zero bits we're clearing out though. |
| if (ConstantInt *Amt = dyn_cast<ConstantInt>(I->getOperand(1))) { |
| if (!CanEvaluateZExtd(I->getOperand(0), Ty, BitsToClear)) |
| return false; |
| BitsToClear += Amt->getZExtValue(); |
| if (BitsToClear > V->getType()->getScalarSizeInBits()) |
| BitsToClear = V->getType()->getScalarSizeInBits(); |
| return true; |
| } |
| // Cannot promote variable LSHR. |
| return false; |
| case Instruction::Select: |
| if (!CanEvaluateZExtd(I->getOperand(1), Ty, Tmp) || |
| !CanEvaluateZExtd(I->getOperand(2), Ty, BitsToClear) || |
| // TODO: If important, we could handle the case when the BitsToClear are |
| // known zero in the disagreeing side. |
| Tmp != BitsToClear) |
| return false; |
| return true; |
| |
| case Instruction::PHI: { |
| // We can change a phi if we can change all operands. Note that we never |
| // get into trouble with cyclic PHIs here because we only consider |
| // instructions with a single use. |
| PHINode *PN = cast<PHINode>(I); |
| if (!CanEvaluateZExtd(PN->getIncomingValue(0), Ty, BitsToClear)) |
| return false; |
| for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) |
| if (!CanEvaluateZExtd(PN->getIncomingValue(i), Ty, Tmp) || |
| // TODO: If important, we could handle the case when the BitsToClear |
| // are known zero in the disagreeing input. |
| Tmp != BitsToClear) |
| return false; |
| return true; |
| } |
| default: |
| // TODO: Can handle more cases here. |
| return false; |
| } |
| } |
| |
| Instruction *InstCombiner::visitZExt(ZExtInst &CI) { |
| // If this zero extend is only used by a truncate, let the truncate by |
| // eliminated before we try to optimize this zext. |
| if (CI.hasOneUse() && isa<TruncInst>(CI.use_back())) |
| return 0; |
| |
| // If one of the common conversion will work, do it. |
| if (Instruction *Result = commonCastTransforms(CI)) |
| return Result; |
| |
| // See if we can simplify any instructions used by the input whose sole |
| // purpose is to compute bits we don't care about. |
| if (SimplifyDemandedInstructionBits(CI)) |
| return &CI; |
| |
| Value *Src = CI.getOperand(0); |
| Type *SrcTy = Src->getType(), *DestTy = CI.getType(); |
| |
| // Attempt to extend the entire input expression tree to the destination |
| // type. Only do this if the dest type is a simple type, don't convert the |
| // expression tree to something weird like i93 unless the source is also |
| // strange. |
| unsigned BitsToClear; |
| if ((DestTy->isVectorTy() || ShouldChangeType(SrcTy, DestTy)) && |
| CanEvaluateZExtd(Src, DestTy, BitsToClear)) { |
| assert(BitsToClear < SrcTy->getScalarSizeInBits() && |
| "Unreasonable BitsToClear"); |
| |
| // Okay, we can transform this! Insert the new expression now. |
| DEBUG(dbgs() << "ICE: EvaluateInDifferentType converting expression type" |
| " to avoid zero extend: " << CI); |
| Value *Res = EvaluateInDifferentType(Src, DestTy, false); |
| assert(Res->getType() == DestTy); |
| |
| uint32_t SrcBitsKept = SrcTy->getScalarSizeInBits()-BitsToClear; |
| uint32_t DestBitSize = DestTy->getScalarSizeInBits(); |
| |
| // If the high bits are already filled with zeros, just replace this |
| // cast with the result. |
| if (MaskedValueIsZero(Res, APInt::getHighBitsSet(DestBitSize, |
| DestBitSize-SrcBitsKept))) |
| return ReplaceInstUsesWith(CI, Res); |
| |
| // We need to emit an AND to clear the high bits. |
| Constant *C = ConstantInt::get(Res->getType(), |
| APInt::getLowBitsSet(DestBitSize, SrcBitsKept)); |
| return BinaryOperator::CreateAnd(Res, C); |
| } |
| |
| // If this is a TRUNC followed by a ZEXT then we are dealing with integral |
| // types and if the sizes are just right we can convert this into a logical |
| // 'and' which will be much cheaper than the pair of casts. |
| if (TruncInst *CSrc = dyn_cast<TruncInst>(Src)) { // A->B->C cast |
| // TODO: Subsume this into EvaluateInDifferentType. |
| |
| // Get the sizes of the types involved. We know that the intermediate type |
| // will be smaller than A or C, but don't know the relation between A and C. |
| Value *A = CSrc->getOperand(0); |
| unsigned SrcSize = A->getType()->getScalarSizeInBits(); |
| unsigned MidSize = CSrc->getType()->getScalarSizeInBits(); |
| unsigned DstSize = CI.getType()->getScalarSizeInBits(); |
| // If we're actually extending zero bits, then if |
| // SrcSize < DstSize: zext(a & mask) |
| // SrcSize == DstSize: a & mask |
| // SrcSize > DstSize: trunc(a) & mask |
| if (SrcSize < DstSize) { |
| APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize)); |
| Constant *AndConst = ConstantInt::get(A->getType(), AndValue); |
| Value *And = Builder->CreateAnd(A, AndConst, CSrc->getName()+".mask"); |
| return new ZExtInst(And, CI.getType()); |
| } |
| |
| if (SrcSize == DstSize) { |
| APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize)); |
| return BinaryOperator::CreateAnd(A, ConstantInt::get(A->getType(), |
| AndValue)); |
| } |
| if (SrcSize > DstSize) { |
| Value *Trunc = Builder->CreateTrunc(A, CI.getType(), "tmp"); |
| APInt AndValue(APInt::getLowBitsSet(DstSize, MidSize)); |
| return BinaryOperator::CreateAnd(Trunc, |
| ConstantInt::get(Trunc->getType(), |
| AndValue)); |
| } |
| } |
| |
| if (ICmpInst *ICI = dyn_cast<ICmpInst>(Src)) |
| return transformZExtICmp(ICI, CI); |
| |
| BinaryOperator *SrcI = dyn_cast<BinaryOperator>(Src); |
| if (SrcI && SrcI->getOpcode() == Instruction::Or) { |
| // zext (or icmp, icmp) --> or (zext icmp), (zext icmp) if at least one |
| // of the (zext icmp) will be transformed. |
| ICmpInst *LHS = dyn_cast<ICmpInst>(SrcI->getOperand(0)); |
| ICmpInst *RHS = dyn_cast<ICmpInst>(SrcI->getOperand(1)); |
| if (LHS && RHS && LHS->hasOneUse() && RHS->hasOneUse() && |
| (transformZExtICmp(LHS, CI, false) || |
| transformZExtICmp(RHS, CI, false))) { |
| Value *LCast = Builder->CreateZExt(LHS, CI.getType(), LHS->getName()); |
| Value *RCast = Builder->CreateZExt(RHS, CI.getType(), RHS->getName()); |
| return BinaryOperator::Create(Instruction::Or, LCast, RCast); |
| } |
| } |
| |
| // zext(trunc(t) & C) -> (t & zext(C)). |
| if (SrcI && SrcI->getOpcode() == Instruction::And && SrcI->hasOneUse()) |
| if (ConstantInt *C = dyn_cast<ConstantInt>(SrcI->getOperand(1))) |
| if (TruncInst *TI = dyn_cast<TruncInst>(SrcI->getOperand(0))) { |
| Value *TI0 = TI->getOperand(0); |
| if (TI0->getType() == CI.getType()) |
| return |
| BinaryOperator::CreateAnd(TI0, |
| ConstantExpr::getZExt(C, CI.getType())); |
| } |
| |
| // zext((trunc(t) & C) ^ C) -> ((t & zext(C)) ^ zext(C)). |
| if (SrcI && SrcI->getOpcode() == Instruction::Xor && SrcI->hasOneUse()) |
| if (ConstantInt *C = dyn_cast<ConstantInt>(SrcI->getOperand(1))) |
| if (BinaryOperator *And = dyn_cast<BinaryOperator>(SrcI->getOperand(0))) |
| if (And->getOpcode() == Instruction::And && And->hasOneUse() && |
| And->getOperand(1) == C) |
| if (TruncInst *TI = dyn_cast<TruncInst>(And->getOperand(0))) { |
| Value *TI0 = TI->getOperand(0); |
| if (TI0->getType() == CI.getType()) { |
| Constant *ZC = ConstantExpr::getZExt(C, CI.getType()); |
| Value *NewAnd = Builder->CreateAnd(TI0, ZC, "tmp"); |
| return BinaryOperator::CreateXor(NewAnd, ZC); |
| } |
| } |
| |
| // zext (xor i1 X, true) to i32 --> xor (zext i1 X to i32), 1 |
| Value *X; |
| if (SrcI && SrcI->hasOneUse() && SrcI->getType()->isIntegerTy(1) && |
| match(SrcI, m_Not(m_Value(X))) && |
| (!X->hasOneUse() || !isa<CmpInst>(X))) { |
| Value *New = Builder->CreateZExt(X, CI.getType()); |
| return BinaryOperator::CreateXor(New, ConstantInt::get(CI.getType(), 1)); |
| } |
| |
| return 0; |
| } |
| |
| /// transformSExtICmp - Transform (sext icmp) to bitwise / integer operations |
| /// in order to eliminate the icmp. |
| Instruction *InstCombiner::transformSExtICmp(ICmpInst *ICI, Instruction &CI) { |
| Value *Op0 = ICI->getOperand(0), *Op1 = ICI->getOperand(1); |
| ICmpInst::Predicate Pred = ICI->getPredicate(); |
| |
| if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) { |
| // (x <s 0) ? -1 : 0 -> ashr x, 31 -> all ones if negative |
| // (x >s -1) ? -1 : 0 -> not (ashr x, 31) -> all ones if positive |
| if ((Pred == ICmpInst::ICMP_SLT && Op1C->isZero()) || |
| (Pred == ICmpInst::ICMP_SGT && Op1C->isAllOnesValue())) { |
| |
| Value *Sh = ConstantInt::get(Op0->getType(), |
| Op0->getType()->getScalarSizeInBits()-1); |
| Value *In = Builder->CreateAShr(Op0, Sh, Op0->getName()+".lobit"); |
| if (In->getType() != CI.getType()) |
| In = Builder->CreateIntCast(In, CI.getType(), true/*SExt*/, "tmp"); |
| |
| if (Pred == ICmpInst::ICMP_SGT) |
| In = Builder->CreateNot(In, In->getName()+".not"); |
| return ReplaceInstUsesWith(CI, In); |
| } |
| |
| // If we know that only one bit of the LHS of the icmp can be set and we |
| // have an equality comparison with zero or a power of 2, we can transform |
| // the icmp and sext into bitwise/integer operations. |
| if (ICI->hasOneUse() && |
| ICI->isEquality() && (Op1C->isZero() || Op1C->getValue().isPowerOf2())){ |
| unsigned BitWidth = Op1C->getType()->getBitWidth(); |
| APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0); |
| APInt TypeMask(APInt::getAllOnesValue(BitWidth)); |
| ComputeMaskedBits(Op0, TypeMask, KnownZero, KnownOne); |
| |
| APInt KnownZeroMask(~KnownZero); |
| if (KnownZeroMask.isPowerOf2()) { |
| Value *In = ICI->getOperand(0); |
| |
| // If the icmp tests for a known zero bit we can constant fold it. |
| if (!Op1C->isZero() && Op1C->getValue() != KnownZeroMask) { |
| Value *V = Pred == ICmpInst::ICMP_NE ? |
| ConstantInt::getAllOnesValue(CI.getType()) : |
| ConstantInt::getNullValue(CI.getType()); |
| return ReplaceInstUsesWith(CI, V); |
| } |
| |
| if (!Op1C->isZero() == (Pred == ICmpInst::ICMP_NE)) { |
| // sext ((x & 2^n) == 0) -> (x >> n) - 1 |
| // sext ((x & 2^n) != 2^n) -> (x >> n) - 1 |
| unsigned ShiftAmt = KnownZeroMask.countTrailingZeros(); |
| // Perform a right shift to place the desired bit in the LSB. |
| if (ShiftAmt) |
| In = Builder->CreateLShr(In, |
| ConstantInt::get(In->getType(), ShiftAmt)); |
| |
| // At this point "In" is either 1 or 0. Subtract 1 to turn |
| // {1, 0} -> {0, -1}. |
| In = Builder->CreateAdd(In, |
| ConstantInt::getAllOnesValue(In->getType()), |
| "sext"); |
| } else { |
| // sext ((x & 2^n) != 0) -> (x << bitwidth-n) a>> bitwidth-1 |
| // sext ((x & 2^n) == 2^n) -> (x << bitwidth-n) a>> bitwidth-1 |
| unsigned ShiftAmt = KnownZeroMask.countLeadingZeros(); |
| // Perform a left shift to place the desired bit in the MSB. |
| if (ShiftAmt) |
| In = Builder->CreateShl(In, |
| ConstantInt::get(In->getType(), ShiftAmt)); |
| |
| // Distribute the bit over the whole bit width. |
| In = Builder->CreateAShr(In, ConstantInt::get(In->getType(), |
| BitWidth - 1), "sext"); |
| } |
| |
| if (CI.getType() == In->getType()) |
| return ReplaceInstUsesWith(CI, In); |
| return CastInst::CreateIntegerCast(In, CI.getType(), true/*SExt*/); |
| } |
| } |
| } |
| |
| // vector (x <s 0) ? -1 : 0 -> ashr x, 31 -> all ones if signed. |
| if (VectorType *VTy = dyn_cast<VectorType>(CI.getType())) { |
| if (Pred == ICmpInst::ICMP_SLT && match(Op1, m_Zero()) && |
| Op0->getType() == CI.getType()) { |
| Type *EltTy = VTy->getElementType(); |
| |
| // splat the shift constant to a constant vector. |
| Constant *VSh = ConstantInt::get(VTy, EltTy->getScalarSizeInBits()-1); |
| Value *In = Builder->CreateAShr(Op0, VSh, Op0->getName()+".lobit"); |
| return ReplaceInstUsesWith(CI, In); |
| } |
| } |
| |
| return 0; |
| } |
| |
| /// CanEvaluateSExtd - Return true if we can take the specified value |
| /// and return it as type Ty without inserting any new casts and without |
| /// changing the value of the common low bits. This is used by code that tries |
| /// to promote integer operations to a wider types will allow us to eliminate |
| /// the extension. |
| /// |
| /// This function works on both vectors and scalars. |
| /// |
| static bool CanEvaluateSExtd(Value *V, Type *Ty) { |
| assert(V->getType()->getScalarSizeInBits() < Ty->getScalarSizeInBits() && |
| "Can't sign extend type to a smaller type"); |
| // If this is a constant, it can be trivially promoted. |
| if (isa<Constant>(V)) |
| return true; |
| |
| Instruction *I = dyn_cast<Instruction>(V); |
| if (!I) return false; |
| |
| // If this is a truncate from the dest type, we can trivially eliminate it, |
| // even if it has multiple uses. |
| // FIXME: This is currently disabled until codegen can handle this without |
| // pessimizing code, PR5997. |
| if (0 && isa<TruncInst>(I) && I->getOperand(0)->getType() == Ty) |
| return true; |
| |
| // We can't extend or shrink something that has multiple uses: doing so would |
| // require duplicating the instruction in general, which isn't profitable. |
| if (!I->hasOneUse()) return false; |
| |
| switch (I->getOpcode()) { |
| case Instruction::SExt: // sext(sext(x)) -> sext(x) |
| case Instruction::ZExt: // sext(zext(x)) -> zext(x) |
| case Instruction::Trunc: // sext(trunc(x)) -> trunc(x) or sext(x) |
| return true; |
| case Instruction::And: |
| case Instruction::Or: |
| case Instruction::Xor: |
| case Instruction::Add: |
| case Instruction::Sub: |
| case Instruction::Mul: |
| // These operators can all arbitrarily be extended if their inputs can. |
| return CanEvaluateSExtd(I->getOperand(0), Ty) && |
| CanEvaluateSExtd(I->getOperand(1), Ty); |
| |
| //case Instruction::Shl: TODO |
| //case Instruction::LShr: TODO |
| |
| case Instruction::Select: |
| return CanEvaluateSExtd(I->getOperand(1), Ty) && |
| CanEvaluateSExtd(I->getOperand(2), Ty); |
| |
| case Instruction::PHI: { |
| // We can change a phi if we can change all operands. Note that we never |
| // get into trouble with cyclic PHIs here because we only consider |
| // instructions with a single use. |
| PHINode *PN = cast<PHINode>(I); |
| for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) |
| if (!CanEvaluateSExtd(PN->getIncomingValue(i), Ty)) return false; |
| return true; |
| } |
| default: |
| // TODO: Can handle more cases here. |
| break; |
| } |
| |
| return false; |
| } |
| |
| Instruction *InstCombiner::visitSExt(SExtInst &CI) { |
| // If this sign extend is only used by a truncate, let the truncate by |
| // eliminated before we try to optimize this zext. |
| if (CI.hasOneUse() && isa<TruncInst>(CI.use_back())) |
| return 0; |
| |
| if (Instruction *I = commonCastTransforms(CI)) |
| return I; |
| |
| // See if we can simplify any instructions used by the input whose sole |
| // purpose is to compute bits we don't care about. |
| if (SimplifyDemandedInstructionBits(CI)) |
| return &CI; |
| |
| Value *Src = CI.getOperand(0); |
| Type *SrcTy = Src->getType(), *DestTy = CI.getType(); |
| |
| // Attempt to extend the entire input expression tree to the destination |
| // type. Only do this if the dest type is a simple type, don't convert the |
| // expression tree to something weird like i93 unless the source is also |
| // strange. |
| if ((DestTy->isVectorTy() || ShouldChangeType(SrcTy, DestTy)) && |
| CanEvaluateSExtd(Src, DestTy)) { |
| // Okay, we can transform this! Insert the new expression now. |
| DEBUG(dbgs() << "ICE: EvaluateInDifferentType converting expression type" |
| " to avoid sign extend: " << CI); |
| Value *Res = EvaluateInDifferentType(Src, DestTy, true); |
| assert(Res->getType() == DestTy); |
| |
| uint32_t SrcBitSize = SrcTy->getScalarSizeInBits(); |
| uint32_t DestBitSize = DestTy->getScalarSizeInBits(); |
| |
| // If the high bits are already filled with sign bit, just replace this |
| // cast with the result. |
| if (ComputeNumSignBits(Res) > DestBitSize - SrcBitSize) |
| return ReplaceInstUsesWith(CI, Res); |
| |
| // We need to emit a shl + ashr to do the sign extend. |
| Value *ShAmt = ConstantInt::get(DestTy, DestBitSize-SrcBitSize); |
| return BinaryOperator::CreateAShr(Builder->CreateShl(Res, ShAmt, "sext"), |
| ShAmt); |
| } |
| |
| // If this input is a trunc from our destination, then turn sext(trunc(x)) |
| // into shifts. |
| if (TruncInst *TI = dyn_cast<TruncInst>(Src)) |
| if (TI->hasOneUse() && TI->getOperand(0)->getType() == DestTy) { |
| uint32_t SrcBitSize = SrcTy->getScalarSizeInBits(); |
| uint32_t DestBitSize = DestTy->getScalarSizeInBits(); |
| |
| // We need to emit a shl + ashr to do the sign extend. |
| Value *ShAmt = ConstantInt::get(DestTy, DestBitSize-SrcBitSize); |
| Value *Res = Builder->CreateShl(TI->getOperand(0), ShAmt, "sext"); |
| return BinaryOperator::CreateAShr(Res, ShAmt); |
| } |
| |
| if (ICmpInst *ICI = dyn_cast<ICmpInst>(Src)) |
| return transformSExtICmp(ICI, CI); |
| |
| // If the input is a shl/ashr pair of a same constant, then this is a sign |
| // extension from a smaller value. If we could trust arbitrary bitwidth |
| // integers, we could turn this into a truncate to the smaller bit and then |
| // use a sext for the whole extension. Since we don't, look deeper and check |
| // for a truncate. If the source and dest are the same type, eliminate the |
| // trunc and extend and just do shifts. For example, turn: |
| // %a = trunc i32 %i to i8 |
| // %b = shl i8 %a, 6 |
| // %c = ashr i8 %b, 6 |
| // %d = sext i8 %c to i32 |
| // into: |
| // %a = shl i32 %i, 30 |
| // %d = ashr i32 %a, 30 |
| Value *A = 0; |
| // TODO: Eventually this could be subsumed by EvaluateInDifferentType. |
| ConstantInt *BA = 0, *CA = 0; |
| if (match(Src, m_AShr(m_Shl(m_Trunc(m_Value(A)), m_ConstantInt(BA)), |
| m_ConstantInt(CA))) && |
| BA == CA && A->getType() == CI.getType()) { |
| unsigned MidSize = Src->getType()->getScalarSizeInBits(); |
| unsigned SrcDstSize = CI.getType()->getScalarSizeInBits(); |
| unsigned ShAmt = CA->getZExtValue()+SrcDstSize-MidSize; |
| Constant *ShAmtV = ConstantInt::get(CI.getType(), ShAmt); |
| A = Builder->CreateShl(A, ShAmtV, CI.getName()); |
| return BinaryOperator::CreateAShr(A, ShAmtV); |
| } |
| |
| return 0; |
| } |
| |
| |
| /// FitsInFPType - Return a Constant* for the specified FP constant if it fits |
| /// in the specified FP type without changing its value. |
| static Constant *FitsInFPType(ConstantFP *CFP, const fltSemantics &Sem) { |
| bool losesInfo; |
| APFloat F = CFP->getValueAPF(); |
| (void)F.convert(Sem, APFloat::rmNearestTiesToEven, &losesInfo); |
| if (!losesInfo) |
| return ConstantFP::get(CFP->getContext(), F); |
| return 0; |
| } |
| |
| /// LookThroughFPExtensions - If this is an fp extension instruction, look |
| /// through it until we get the source value. |
| static Value *LookThroughFPExtensions(Value *V) { |
| if (Instruction *I = dyn_cast<Instruction>(V)) |
| if (I->getOpcode() == Instruction::FPExt) |
| return LookThroughFPExtensions(I->getOperand(0)); |
| |
| // If this value is a constant, return the constant in the smallest FP type |
| // that can accurately represent it. This allows us to turn |
| // (float)((double)X+2.0) into x+2.0f. |
| if (ConstantFP *CFP = dyn_cast<ConstantFP>(V)) { |
| if (CFP->getType() == Type::getPPC_FP128Ty(V->getContext())) |
| return V; // No constant folding of this. |
| // See if the value can be truncated to float and then reextended. |
| if (Value *V = FitsInFPType(CFP, APFloat::IEEEsingle)) |
| return V; |
| if (CFP->getType()->isDoubleTy()) |
| return V; // Won't shrink. |
| if (Value *V = FitsInFPType(CFP, APFloat::IEEEdouble)) |
| return V; |
| // Don't try to shrink to various long double types. |
| } |
| |
| return V; |
| } |
| |
| Instruction *InstCombiner::visitFPTrunc(FPTruncInst &CI) { |
| if (Instruction *I = commonCastTransforms(CI)) |
| return I; |
| |
| // If we have fptrunc(fadd (fpextend x), (fpextend y)), where x and y are |
| // smaller than the destination type, we can eliminate the truncate by doing |
| // the add as the smaller type. This applies to fadd/fsub/fmul/fdiv as well |
| // as many builtins (sqrt, etc). |
| BinaryOperator *OpI = dyn_cast<BinaryOperator>(CI.getOperand(0)); |
| if (OpI && OpI->hasOneUse()) { |
| switch (OpI->getOpcode()) { |
| default: break; |
| case Instruction::FAdd: |
| case Instruction::FSub: |
| case Instruction::FMul: |
| case Instruction::FDiv: |
| case Instruction::FRem: |
| Type *SrcTy = OpI->getType(); |
| Value *LHSTrunc = LookThroughFPExtensions(OpI->getOperand(0)); |
| Value *RHSTrunc = LookThroughFPExtensions(OpI->getOperand(1)); |
| if (LHSTrunc->getType() != SrcTy && |
| RHSTrunc->getType() != SrcTy) { |
| unsigned DstSize = CI.getType()->getScalarSizeInBits(); |
| // If the source types were both smaller than the destination type of |
| // the cast, do this xform. |
| if (LHSTrunc->getType()->getScalarSizeInBits() <= DstSize && |
| RHSTrunc->getType()->getScalarSizeInBits() <= DstSize) { |
| LHSTrunc = Builder->CreateFPExt(LHSTrunc, CI.getType()); |
| RHSTrunc = Builder->CreateFPExt(RHSTrunc, CI.getType()); |
| return BinaryOperator::Create(OpI->getOpcode(), LHSTrunc, RHSTrunc); |
| } |
| } |
| break; |
| } |
| } |
| |
| // Fold (fptrunc (sqrt (fpext x))) -> (sqrtf x) |
| // NOTE: This should be disabled by -fno-builtin-sqrt if we ever support it. |
| CallInst *Call = dyn_cast<CallInst>(CI.getOperand(0)); |
| if (Call && Call->getCalledFunction() && |
| Call->getCalledFunction()->getName() == "sqrt" && |
| Call->getNumArgOperands() == 1 && |
| Call->hasOneUse()) { |
| CastInst *Arg = dyn_cast<CastInst>(Call->getArgOperand(0)); |
| if (Arg && Arg->getOpcode() == Instruction::FPExt && |
| CI.getType()->isFloatTy() && |
| Call->getType()->isDoubleTy() && |
| Arg->getType()->isDoubleTy() && |
| Arg->getOperand(0)->getType()->isFloatTy()) { |
| Function *Callee = Call->getCalledFunction(); |
| Module *M = CI.getParent()->getParent()->getParent(); |
| Constant *SqrtfFunc = M->getOrInsertFunction("sqrtf", |
| Callee->getAttributes(), |
| Builder->getFloatTy(), |
| Builder->getFloatTy(), |
| NULL); |
| CallInst *ret = CallInst::Create(SqrtfFunc, Arg->getOperand(0), |
| "sqrtfcall"); |
| ret->setAttributes(Callee->getAttributes()); |
| |
| |
| // Remove the old Call. With -fmath-errno, it won't get marked readnone. |
| ReplaceInstUsesWith(*Call, UndefValue::get(Call->getType())); |
| EraseInstFromFunction(*Call); |
| return ret; |
| } |
| } |
| |
| return 0; |
| } |
| |
| Instruction *InstCombiner::visitFPExt(CastInst &CI) { |
| return commonCastTransforms(CI); |
| } |
| |
| Instruction *InstCombiner::visitFPToUI(FPToUIInst &FI) { |
| Instruction *OpI = dyn_cast<Instruction>(FI.getOperand(0)); |
| if (OpI == 0) |
| return commonCastTransforms(FI); |
| |
| // fptoui(uitofp(X)) --> X |
| // fptoui(sitofp(X)) --> X |
| // This is safe if the intermediate type has enough bits in its mantissa to |
| // accurately represent all values of X. For example, do not do this with |
| // i64->float->i64. This is also safe for sitofp case, because any negative |
| // 'X' value would cause an undefined result for the fptoui. |
| if ((isa<UIToFPInst>(OpI) || isa<SIToFPInst>(OpI)) && |
| OpI->getOperand(0)->getType() == FI.getType() && |
| (int)FI.getType()->getScalarSizeInBits() < /*extra bit for sign */ |
| OpI->getType()->getFPMantissaWidth()) |
| return ReplaceInstUsesWith(FI, OpI->getOperand(0)); |
| |
| return commonCastTransforms(FI); |
| } |
| |
| Instruction *InstCombiner::visitFPToSI(FPToSIInst &FI) { |
| Instruction *OpI = dyn_cast<Instruction>(FI.getOperand(0)); |
| if (OpI == 0) |
| return commonCastTransforms(FI); |
| |
| // fptosi(sitofp(X)) --> X |
| // fptosi(uitofp(X)) --> X |
| // This is safe if the intermediate type has enough bits in its mantissa to |
| // accurately represent all values of X. For example, do not do this with |
| // i64->float->i64. This is also safe for sitofp case, because any negative |
| // 'X' value would cause an undefined result for the fptoui. |
| if ((isa<UIToFPInst>(OpI) || isa<SIToFPInst>(OpI)) && |
| OpI->getOperand(0)->getType() == FI.getType() && |
| (int)FI.getType()->getScalarSizeInBits() <= |
| OpI->getType()->getFPMantissaWidth()) |
| return ReplaceInstUsesWith(FI, OpI->getOperand(0)); |
| |
| return commonCastTransforms(FI); |
| } |
| |
| Instruction *InstCombiner::visitUIToFP(CastInst &CI) { |
| return commonCastTransforms(CI); |
| } |
| |
| Instruction *InstCombiner::visitSIToFP(CastInst &CI) { |
| return commonCastTransforms(CI); |
| } |
| |
| Instruction *InstCombiner::visitIntToPtr(IntToPtrInst &CI) { |
| // If the source integer type is not the intptr_t type for this target, do a |
| // trunc or zext to the intptr_t type, then inttoptr of it. This allows the |
| // cast to be exposed to other transforms. |
| if (TD) { |
| if (CI.getOperand(0)->getType()->getScalarSizeInBits() > |
| TD->getPointerSizeInBits()) { |
| Value *P = Builder->CreateTrunc(CI.getOperand(0), |
| TD->getIntPtrType(CI.getContext()), "tmp"); |
| return new IntToPtrInst(P, CI.getType()); |
| } |
| if (CI.getOperand(0)->getType()->getScalarSizeInBits() < |
| TD->getPointerSizeInBits()) { |
| Value *P = Builder->CreateZExt(CI.getOperand(0), |
| TD->getIntPtrType(CI.getContext()), "tmp"); |
| return new IntToPtrInst(P, CI.getType()); |
| } |
| } |
| |
| if (Instruction *I = commonCastTransforms(CI)) |
| return I; |
| |
| return 0; |
| } |
| |
| /// @brief Implement the transforms for cast of pointer (bitcast/ptrtoint) |
| Instruction *InstCombiner::commonPointerCastTransforms(CastInst &CI) { |
| Value *Src = CI.getOperand(0); |
| |
| if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) { |
| // If casting the result of a getelementptr instruction with no offset, turn |
| // this into a cast of the original pointer! |
| if (GEP->hasAllZeroIndices()) { |
| // Changing the cast operand is usually not a good idea but it is safe |
| // here because the pointer operand is being replaced with another |
| // pointer operand so the opcode doesn't need to change. |
| Worklist.Add(GEP); |
| CI.setOperand(0, GEP->getOperand(0)); |
| return &CI; |
| } |
| |
| // If the GEP has a single use, and the base pointer is a bitcast, and the |
| // GEP computes a constant offset, see if we can convert these three |
| // instructions into fewer. This typically happens with unions and other |
| // non-type-safe code. |
| if (TD && GEP->hasOneUse() && isa<BitCastInst>(GEP->getOperand(0)) && |
| GEP->hasAllConstantIndices()) { |
| // We are guaranteed to get a constant from EmitGEPOffset. |
| ConstantInt *OffsetV = cast<ConstantInt>(EmitGEPOffset(GEP)); |
| int64_t Offset = OffsetV->getSExtValue(); |
| |
| // Get the base pointer input of the bitcast, and the type it points to. |
| Value *OrigBase = cast<BitCastInst>(GEP->getOperand(0))->getOperand(0); |
| Type *GEPIdxTy = |
| cast<PointerType>(OrigBase->getType())->getElementType(); |
| SmallVector<Value*, 8> NewIndices; |
| if (FindElementAtOffset(GEPIdxTy, Offset, NewIndices)) { |
| // If we were able to index down into an element, create the GEP |
| // and bitcast the result. This eliminates one bitcast, potentially |
| // two. |
| Value *NGEP = cast<GEPOperator>(GEP)->isInBounds() ? |
| Builder->CreateInBoundsGEP(OrigBase, NewIndices) : |
| Builder->CreateGEP(OrigBase, NewIndices); |
| NGEP->takeName(GEP); |
| |
| if (isa<BitCastInst>(CI)) |
| return new BitCastInst(NGEP, CI.getType()); |
| assert(isa<PtrToIntInst>(CI)); |
| return new PtrToIntInst(NGEP, CI.getType()); |
| } |
| } |
| } |
| |
| return commonCastTransforms(CI); |
| } |
| |
| Instruction *InstCombiner::visitPtrToInt(PtrToIntInst &CI) { |
| // If the destination integer type is not the intptr_t type for this target, |
| // do a ptrtoint to intptr_t then do a trunc or zext. This allows the cast |
| // to be exposed to other transforms. |
| if (TD) { |
| if (CI.getType()->getScalarSizeInBits() < TD->getPointerSizeInBits()) { |
| Value *P = Builder->CreatePtrToInt(CI.getOperand(0), |
| TD->getIntPtrType(CI.getContext()), |
| "tmp"); |
| return new TruncInst(P, CI.getType()); |
| } |
| if (CI.getType()->getScalarSizeInBits() > TD->getPointerSizeInBits()) { |
| Value *P = Builder->CreatePtrToInt(CI.getOperand(0), |
| TD->getIntPtrType(CI.getContext()), |
| "tmp"); |
| return new ZExtInst(P, CI.getType()); |
| } |
| } |
| |
| return commonPointerCastTransforms(CI); |
| } |
| |
| /// OptimizeVectorResize - This input value (which is known to have vector type) |
| /// is being zero extended or truncated to the specified vector type. Try to |
| /// replace it with a shuffle (and vector/vector bitcast) if possible. |
| /// |
| /// The source and destination vector types may have different element types. |
| static Instruction *OptimizeVectorResize(Value *InVal, VectorType *DestTy, |
| InstCombiner &IC) { |
| // We can only do this optimization if the output is a multiple of the input |
| // element size, or the input is a multiple of the output element size. |
| // Convert the input type to have the same element type as the output. |
| VectorType *SrcTy = cast<VectorType>(InVal->getType()); |
| |
| if (SrcTy->getElementType() != DestTy->getElementType()) { |
| // The input types don't need to be identical, but for now they must be the |
| // same size. There is no specific reason we couldn't handle things like |
| // <4 x i16> -> <4 x i32> by bitcasting to <2 x i32> but haven't gotten |
| // there yet. |
| if (SrcTy->getElementType()->getPrimitiveSizeInBits() != |
| DestTy->getElementType()->getPrimitiveSizeInBits()) |
| return 0; |
| |
| SrcTy = VectorType::get(DestTy->getElementType(), SrcTy->getNumElements()); |
| InVal = IC.Builder->CreateBitCast(InVal, SrcTy); |
| } |
| |
| // Now that the element types match, get the shuffle mask and RHS of the |
| // shuffle to use, which depends on whether we're increasing or decreasing the |
| // size of the input. |
| SmallVector<Constant*, 16> ShuffleMask; |
| Value *V2; |
| IntegerType *Int32Ty = Type::getInt32Ty(SrcTy->getContext()); |
| |
| if (SrcTy->getNumElements() > DestTy->getNumElements()) { |
| // If we're shrinking the number of elements, just shuffle in the low |
| // elements from the input and use undef as the second shuffle input. |
| V2 = UndefValue::get(SrcTy); |
| for (unsigned i = 0, e = DestTy->getNumElements(); i != e; ++i) |
| ShuffleMask.push_back(ConstantInt::get(Int32Ty, i)); |
| |
| } else { |
| // If we're increasing the number of elements, shuffle in all of the |
| // elements from InVal and fill the rest of the result elements with zeros |
| // from a constant zero. |
| V2 = Constant::getNullValue(SrcTy); |
| unsigned SrcElts = SrcTy->getNumElements(); |
| for (unsigned i = 0, e = SrcElts; i != e; ++i) |
| ShuffleMask.push_back(ConstantInt::get(Int32Ty, i)); |
| |
| // The excess elements reference the first element of the zero input. |
| ShuffleMask.append(DestTy->getNumElements()-SrcElts, |
| ConstantInt::get(Int32Ty, SrcElts)); |
| } |
| |
| return new ShuffleVectorInst(InVal, V2, ConstantVector::get(ShuffleMask)); |
| } |
| |
| static bool isMultipleOfTypeSize(unsigned Value, Type *Ty) { |
| return Value % Ty->getPrimitiveSizeInBits() == 0; |
| } |
| |
| static unsigned getTypeSizeIndex(unsigned Value, Type *Ty) { |
| return Value / Ty->getPrimitiveSizeInBits(); |
| } |
| |
| /// CollectInsertionElements - V is a value which is inserted into a vector of |
| /// VecEltTy. Look through the value to see if we can decompose it into |
| /// insertions into the vector. See the example in the comment for |
| /// OptimizeIntegerToVectorInsertions for the pattern this handles. |
| /// The type of V is always a non-zero multiple of VecEltTy's size. |
| /// |
| /// This returns false if the pattern can't be matched or true if it can, |
| /// filling in Elements with the elements found here. |
| static bool CollectInsertionElements(Value *V, unsigned ElementIndex, |
| SmallVectorImpl<Value*> &Elements, |
| Type *VecEltTy) { |
| // Undef values never contribute useful bits to the result. |
| if (isa<UndefValue>(V)) return true; |
| |
| // If we got down to a value of the right type, we win, try inserting into the |
| // right element. |
| if (V->getType() == VecEltTy) { |
| // Inserting null doesn't actually insert any elements. |
| if (Constant *C = dyn_cast<Constant>(V)) |
| if (C->isNullValue()) |
| return true; |
| |
| // Fail if multiple elements are inserted into this slot. |
| if (ElementIndex >= Elements.size() || Elements[ElementIndex] != 0) |
| return false; |
| |
| Elements[ElementIndex] = V; |
| return true; |
| } |
| |
| if (Constant *C = dyn_cast<Constant>(V)) { |
| // Figure out the # elements this provides, and bitcast it or slice it up |
| // as required. |
| unsigned NumElts = getTypeSizeIndex(C->getType()->getPrimitiveSizeInBits(), |
| VecEltTy); |
| // If the constant is the size of a vector element, we just need to bitcast |
| // it to the right type so it gets properly inserted. |
| if (NumElts == 1) |
| return CollectInsertionElements(ConstantExpr::getBitCast(C, VecEltTy), |
| ElementIndex, Elements, VecEltTy); |
| |
| // Okay, this is a constant that covers multiple elements. Slice it up into |
| // pieces and insert each element-sized piece into the vector. |
| if (!isa<IntegerType>(C->getType())) |
| C = ConstantExpr::getBitCast(C, IntegerType::get(V->getContext(), |
| C->getType()->getPrimitiveSizeInBits())); |
| unsigned ElementSize = VecEltTy->getPrimitiveSizeInBits(); |
| Type *ElementIntTy = IntegerType::get(C->getContext(), ElementSize); |
| |
| for (unsigned i = 0; i != NumElts; ++i) { |
| Constant *Piece = ConstantExpr::getLShr(C, ConstantInt::get(C->getType(), |
| i*ElementSize)); |
| Piece = ConstantExpr::getTrunc(Piece, ElementIntTy); |
| if (!CollectInsertionElements(Piece, ElementIndex+i, Elements, VecEltTy)) |
| return false; |
| } |
| return true; |
| } |
| |
| if (!V->hasOneUse()) return false; |
| |
| Instruction *I = dyn_cast<Instruction>(V); |
| if (I == 0) return false; |
| switch (I->getOpcode()) { |
| default: return false; // Unhandled case. |
| case Instruction::BitCast: |
| return CollectInsertionElements(I->getOperand(0), ElementIndex, |
| Elements, VecEltTy); |
| case Instruction::ZExt: |
| if (!isMultipleOfTypeSize( |
| I->getOperand(0)->getType()->getPrimitiveSizeInBits(), |
| VecEltTy)) |
| return false; |
| return CollectInsertionElements(I->getOperand(0), ElementIndex, |
| Elements, VecEltTy); |
| case Instruction::Or: |
| return CollectInsertionElements(I->getOperand(0), ElementIndex, |
| Elements, VecEltTy) && |
| CollectInsertionElements(I->getOperand(1), ElementIndex, |
| Elements, VecEltTy); |
| case Instruction::Shl: { |
| // Must be shifting by a constant that is a multiple of the element size. |
| ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1)); |
| if (CI == 0) return false; |
| if (!isMultipleOfTypeSize(CI->getZExtValue(), VecEltTy)) return false; |
| unsigned IndexShift = getTypeSizeIndex(CI->getZExtValue(), VecEltTy); |
| |
| return CollectInsertionElements(I->getOperand(0), ElementIndex+IndexShift, |
| Elements, VecEltTy); |
| } |
| |
| } |
| } |
| |
| |
| /// OptimizeIntegerToVectorInsertions - If the input is an 'or' instruction, we |
| /// may be doing shifts and ors to assemble the elements of the vector manually. |
| /// Try to rip the code out and replace it with insertelements. This is to |
| /// optimize code like this: |
| /// |
| /// %tmp37 = bitcast float %inc to i32 |
| /// %tmp38 = zext i32 %tmp37 to i64 |
| /// %tmp31 = bitcast float %inc5 to i32 |
| /// %tmp32 = zext i32 %tmp31 to i64 |
| /// %tmp33 = shl i64 %tmp32, 32 |
| /// %ins35 = or i64 %tmp33, %tmp38 |
| /// %tmp43 = bitcast i64 %ins35 to <2 x float> |
| /// |
| /// Into two insertelements that do "buildvector{%inc, %inc5}". |
| static Value *OptimizeIntegerToVectorInsertions(BitCastInst &CI, |
| InstCombiner &IC) { |
| VectorType *DestVecTy = cast<VectorType>(CI.getType()); |
| Value *IntInput = CI.getOperand(0); |
| |
| SmallVector<Value*, 8> Elements(DestVecTy->getNumElements()); |
| if (!CollectInsertionElements(IntInput, 0, Elements, |
| DestVecTy->getElementType())) |
| return 0; |
| |
| // If we succeeded, we know that all of the element are specified by Elements |
| // or are zero if Elements has a null entry. Recast this as a set of |
| // insertions. |
| Value *Result = Constant::getNullValue(CI.getType()); |
| for (unsigned i = 0, e = Elements.size(); i != e; ++i) { |
| if (Elements[i] == 0) continue; // Unset element. |
| |
| Result = IC.Builder->CreateInsertElement(Result, Elements[i], |
| IC.Builder->getInt32(i)); |
| } |
| |
| return Result; |
| } |
| |
| |
| /// OptimizeIntToFloatBitCast - See if we can optimize an integer->float/double |
| /// bitcast. The various long double bitcasts can't get in here. |
| static Instruction *OptimizeIntToFloatBitCast(BitCastInst &CI,InstCombiner &IC){ |
| Value *Src = CI.getOperand(0); |
| Type *DestTy = CI.getType(); |
| |
| // If this is a bitcast from int to float, check to see if the int is an |
| // extraction from a vector. |
| Value *VecInput = 0; |
| // bitcast(trunc(bitcast(somevector))) |
| if (match(Src, m_Trunc(m_BitCast(m_Value(VecInput)))) && |
| isa<VectorType>(VecInput->getType())) { |
| VectorType *VecTy = cast<VectorType>(VecInput->getType()); |
| unsigned DestWidth = DestTy->getPrimitiveSizeInBits(); |
| |
| if (VecTy->getPrimitiveSizeInBits() % DestWidth == 0) { |
| // If the element type of the vector doesn't match the result type, |
| // bitcast it to be a vector type we can extract from. |
| if (VecTy->getElementType() != DestTy) { |
| VecTy = VectorType::get(DestTy, |
| VecTy->getPrimitiveSizeInBits() / DestWidth); |
| VecInput = IC.Builder->CreateBitCast(VecInput, VecTy); |
| } |
| |
| return ExtractElementInst::Create(VecInput, IC.Builder->getInt32(0)); |
| } |
| } |
| |
| // bitcast(trunc(lshr(bitcast(somevector), cst)) |
| ConstantInt *ShAmt = 0; |
| if (match(Src, m_Trunc(m_LShr(m_BitCast(m_Value(VecInput)), |
| m_ConstantInt(ShAmt)))) && |
| isa<VectorType>(VecInput->getType())) { |
| VectorType *VecTy = cast<VectorType>(VecInput->getType()); |
| unsigned DestWidth = DestTy->getPrimitiveSizeInBits(); |
| if (VecTy->getPrimitiveSizeInBits() % DestWidth == 0 && |
| ShAmt->getZExtValue() % DestWidth == 0) { |
| // If the element type of the vector doesn't match the result type, |
| // bitcast it to be a vector type we can extract from. |
| if (VecTy->getElementType() != DestTy) { |
| VecTy = VectorType::get(DestTy, |
| VecTy->getPrimitiveSizeInBits() / DestWidth); |
| VecInput = IC.Builder->CreateBitCast(VecInput, VecTy); |
| } |
| |
| unsigned Elt = ShAmt->getZExtValue() / DestWidth; |
| return ExtractElementInst::Create(VecInput, IC.Builder->getInt32(Elt)); |
| } |
| } |
| return 0; |
| } |
| |
| Instruction *InstCombiner::visitBitCast(BitCastInst &CI) { |
| // If the operands are integer typed then apply the integer transforms, |
| // otherwise just apply the common ones. |
| Value *Src = CI.getOperand(0); |
| Type *SrcTy = Src->getType(); |
| Type *DestTy = CI.getType(); |
| |
| // Get rid of casts from one type to the same type. These are useless and can |
| // be replaced by the operand. |
| if (DestTy == Src->getType()) |
| return ReplaceInstUsesWith(CI, Src); |
| |
| if (PointerType *DstPTy = dyn_cast<PointerType>(DestTy)) { |
| PointerType *SrcPTy = cast<PointerType>(SrcTy); |
| Type *DstElTy = DstPTy->getElementType(); |
| Type *SrcElTy = SrcPTy->getElementType(); |
| |
| // If the address spaces don't match, don't eliminate the bitcast, which is |
| // required for changing types. |
| if (SrcPTy->getAddressSpace() != DstPTy->getAddressSpace()) |
| return 0; |
| |
| // If we are casting a alloca to a pointer to a type of the same |
| // size, rewrite the allocation instruction to allocate the "right" type. |
| // There is no need to modify malloc calls because it is their bitcast that |
| // needs to be cleaned up. |
| if (AllocaInst *AI = dyn_cast<AllocaInst>(Src)) |
| if (Instruction *V = PromoteCastOfAllocation(CI, *AI)) |
| return V; |
| |
| // If the source and destination are pointers, and this cast is equivalent |
| // to a getelementptr X, 0, 0, 0... turn it into the appropriate gep. |
| // This can enhance SROA and other transforms that want type-safe pointers. |
| Constant *ZeroUInt = |
| Constant::getNullValue(Type::getInt32Ty(CI.getContext())); |
| unsigned NumZeros = 0; |
| while (SrcElTy != DstElTy && |
| isa<CompositeType>(SrcElTy) && !SrcElTy->isPointerTy() && |
| SrcElTy->getNumContainedTypes() /* not "{}" */) { |
| SrcElTy = cast<CompositeType>(SrcElTy)->getTypeAtIndex(ZeroUInt); |
| ++NumZeros; |
| } |
| |
| // If we found a path from the src to dest, create the getelementptr now. |
| if (SrcElTy == DstElTy) { |
| SmallVector<Value*, 8> Idxs(NumZeros+1, ZeroUInt); |
| return GetElementPtrInst::CreateInBounds(Src, Idxs); |
| } |
| } |
| |
| // Try to optimize int -> float bitcasts. |
| if ((DestTy->isFloatTy() || DestTy->isDoubleTy()) && isa<IntegerType>(SrcTy)) |
| if (Instruction *I = OptimizeIntToFloatBitCast(CI, *this)) |
| return I; |
| |
| if (VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) { |
| if (DestVTy->getNumElements() == 1 && !SrcTy->isVectorTy()) { |
| Value *Elem = Builder->CreateBitCast(Src, DestVTy->getElementType()); |
| return InsertElementInst::Create(UndefValue::get(DestTy), Elem, |
| Constant::getNullValue(Type::getInt32Ty(CI.getContext()))); |
| // FIXME: Canonicalize bitcast(insertelement) -> insertelement(bitcast) |
| } |
| |
| if (isa<IntegerType>(SrcTy)) { |
| // If this is a cast from an integer to vector, check to see if the input |
| // is a trunc or zext of a bitcast from vector. If so, we can replace all |
| // the casts with a shuffle and (potentially) a bitcast. |
| if (isa<TruncInst>(Src) || isa<ZExtInst>(Src)) { |
| CastInst *SrcCast = cast<CastInst>(Src); |
| if (BitCastInst *BCIn = dyn_cast<BitCastInst>(SrcCast->getOperand(0))) |
| if (isa<VectorType>(BCIn->getOperand(0)->getType())) |
| if (Instruction *I = OptimizeVectorResize(BCIn->getOperand(0), |
| cast<VectorType>(DestTy), *this)) |
| return I; |
| } |
| |
| // If the input is an 'or' instruction, we may be doing shifts and ors to |
| // assemble the elements of the vector manually. Try to rip the code out |
| // and replace it with insertelements. |
| if (Value *V = OptimizeIntegerToVectorInsertions(CI, *this)) |
| return ReplaceInstUsesWith(CI, V); |
| } |
| } |
| |
| if (VectorType *SrcVTy = dyn_cast<VectorType>(SrcTy)) { |
| if (SrcVTy->getNumElements() == 1 && !DestTy->isVectorTy()) { |
| Value *Elem = |
| Builder->CreateExtractElement(Src, |
| Constant::getNullValue(Type::getInt32Ty(CI.getContext()))); |
| return CastInst::Create(Instruction::BitCast, Elem, DestTy); |
| } |
| } |
| |
| if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(Src)) { |
| // Okay, we have (bitcast (shuffle ..)). Check to see if this is |
| // a bitcast to a vector with the same # elts. |
| if (SVI->hasOneUse() && DestTy->isVectorTy() && |
| cast<VectorType>(DestTy)->getNumElements() == |
| SVI->getType()->getNumElements() && |
| SVI->getType()->getNumElements() == |
| cast<VectorType>(SVI->getOperand(0)->getType())->getNumElements()) { |
| BitCastInst *Tmp; |
| // If either of the operands is a cast from CI.getType(), then |
| // evaluating the shuffle in the casted destination's type will allow |
| // us to eliminate at least one cast. |
| if (((Tmp = dyn_cast<BitCastInst>(SVI->getOperand(0))) && |
| Tmp->getOperand(0)->getType() == DestTy) || |
| ((Tmp = dyn_cast<BitCastInst>(SVI->getOperand(1))) && |
| Tmp->getOperand(0)->getType() == DestTy)) { |
| Value *LHS = Builder->CreateBitCast(SVI->getOperand(0), DestTy); |
| Value *RHS = Builder->CreateBitCast(SVI->getOperand(1), DestTy); |
| // Return a new shuffle vector. Use the same element ID's, as we |
| // know the vector types match #elts. |
| return new ShuffleVectorInst(LHS, RHS, SVI->getOperand(2)); |
| } |
| } |
| } |
| |
| if (SrcTy->isPointerTy()) |
| return commonPointerCastTransforms(CI); |
| return commonCastTransforms(CI); |
| } |