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Teach InstCombine's ComputeMaskedBits to handle pointer expressions

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in addition to integer expressions. Rewrite GetOrEnforceKnownAlignment
as a ComputeMaskedBits problem, moving all of its special alignment
knowledge to ComputeMaskedBits as low-zero-bits knowledge.

Also, teach ComputeMaskedBits a few basic things about Mul and PHI
instructions.

This improves ComputeMaskedBits-based simplifications in a few cases,
but more noticeably it significantly improves instcombine's alignment
detection for loads, stores, and memory intrinsics.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@49492 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2008-04-10 18:43:06 +00:00
parent 172b70c62a
commit eee962e1ce
3 changed files with 376 additions and 144 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

447
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -372,6 +372,15 @@ namespace {
Value *EvaluateInDifferentType(Value *V, const Type *Ty, bool isSigned);
void ComputeMaskedBits(Value *V, const APInt &Mask, APInt& KnownZero,
APInt& KnownOne, unsigned Depth = 0);
bool MaskedValueIsZero(Value *V, const APInt& Mask, unsigned Depth = 0);
bool CanEvaluateInDifferentType(Value *V, const IntegerType *Ty,
unsigned CastOpc,
int &NumCastsRemoved);
unsigned GetOrEnforceKnownAlignment(Value *V,
unsigned PrefAlign = 0);
};
char InstCombiner::ID = 0;
@ -580,6 +589,17 @@ static User *dyn_castGetElementPtr(Value *V) {
return false;
}
/// getOpcode - If this is an Instruction or a ConstantExpr, return the
/// opcode value. Otherwise return UserOp1.
static unsigned getOpcode(User *U) {
if (Instruction *I = dyn_cast<Instruction>(U))
return I->getOpcode();
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U))
return CE->getOpcode();
// Use UserOp1 to mean there's no opcode.
return Instruction::UserOp1;
}
/// AddOne - Add one to a ConstantInt
static ConstantInt *AddOne(ConstantInt *C) {
APInt Val(C->getValue());
@ -639,12 +659,17 @@ static bool MultiplyOverflows(ConstantInt *C1, ConstantInt *C2, bool sign) {
/// optimized based on the contradictory assumption that it is non-zero.
/// Because instcombine aggressively folds operations with undef args anyway,
/// this won't lose us code quality.
static void ComputeMaskedBits(Value *V, const APInt &Mask, APInt& KnownZero,
APInt& KnownOne, unsigned Depth = 0) {
void InstCombiner::ComputeMaskedBits(Value *V, const APInt &Mask,
APInt& KnownZero, APInt& KnownOne,
unsigned Depth) {
assert(V && "No Value?");
assert(Depth <= 6 && "Limit Search Depth");
uint32_t BitWidth = Mask.getBitWidth();
assert(cast<IntegerType>(V->getType())->getBitWidth() == BitWidth &&
assert((V->getType()->isInteger() || isa<PointerType>(V->getType())) &&
"Not integer or pointer type!");
assert((!TD || TD->getTypeSizeInBits(V->getType()) == BitWidth) &&
(!isa<IntegerType>(V->getType()) ||
V->getType()->getPrimitiveSizeInBits() == BitWidth) &&
KnownZero.getBitWidth() == BitWidth &&
KnownOne.getBitWidth() == BitWidth &&
"V, Mask, KnownOne and KnownZero should have same BitWidth");
@ -654,17 +679,37 @@ static void ComputeMaskedBits(Value *V, const APInt &Mask, APInt& KnownZero,
KnownZero = ~KnownOne & Mask;
return;
}
// Null is all-zeros.
if (isa<ConstantPointerNull>(V)) {
KnownOne.clear();
KnownZero = Mask;
return;
}
// The address of an aligned GlobalValue has trailing zeros.
if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
unsigned Align = GV->getAlignment();
if (Align == 0 && TD && GV->getType()->getElementType()->isSized())
Align = TD->getPrefTypeAlignment(GV->getType()->getElementType());
if (Align > 0)
KnownZero = Mask & APInt::getLowBitsSet(BitWidth,
CountTrailingZeros_32(Align));
else
KnownZero.clear();
KnownOne.clear();
return;
}
if (Depth == 6 || Mask == 0)
return; // Limit search depth.
Instruction *I = dyn_cast<Instruction>(V);
User *I = dyn_cast<User>(V);
if (!I) return;
KnownZero.clear(); KnownOne.clear(); // Don't know anything.
APInt KnownZero2(KnownZero), KnownOne2(KnownOne);
switch (I->getOpcode()) {
switch (getOpcode(I)) {
default: break;
case Instruction::And: {
// If either the LHS or the RHS are Zero, the result is zero.
ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
@ -705,6 +750,24 @@ static void ComputeMaskedBits(Value *V, const APInt &Mask, APInt& KnownZero,
KnownZero = KnownZeroOut;
return;
}
case Instruction::Mul: {
APInt Mask2 = APInt::getAllOnesValue(BitWidth);
ComputeMaskedBits(I->getOperand(1), Mask2, KnownZero, KnownOne, Depth+1);
ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
// If low bits are zero in either operand, output low known-0 bits.
// More trickiness is possible, but this is sufficient for the
// interesting case of alignment computation.
KnownOne.clear();
unsigned TrailZ = KnownZero.countTrailingOnes() +
KnownZero2.countTrailingOnes();
TrailZ = std::min(TrailZ, BitWidth);
KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ);
KnownZero &= Mask;
return;
}
case Instruction::Select:
ComputeMaskedBits(I->getOperand(2), Mask, KnownZero, KnownOne, Depth+1);
ComputeMaskedBits(I->getOperand(1), Mask, KnownZero2, KnownOne2, Depth+1);
@ -720,48 +783,40 @@ static void ComputeMaskedBits(Value *V, const APInt &Mask, APInt& KnownZero,
case Instruction::FPToUI:
case Instruction::FPToSI:
case Instruction::SIToFP:
case Instruction::PtrToInt:
case Instruction::UIToFP:
return; // Can't work with floating point.
case Instruction::PtrToInt:
case Instruction::IntToPtr:
return; // Can't work with floating point or pointers
// We can't handle these if we don't know the pointer size.
if (!TD) return;
// Fall through and handle them the same as zext/trunc.
case Instruction::ZExt:
case Instruction::Trunc: {
// All these have integer operands
uint32_t SrcBitWidth =
cast<IntegerType>(I->getOperand(0)->getType())->getBitWidth();
const Type *SrcTy = I->getOperand(0)->getType();
uint32_t SrcBitWidth = TD ?
TD->getTypeSizeInBits(SrcTy) :
SrcTy->getPrimitiveSizeInBits();
APInt MaskIn(Mask);
MaskIn.zext(SrcBitWidth);
KnownZero.zext(SrcBitWidth);
KnownOne.zext(SrcBitWidth);
MaskIn.zextOrTrunc(SrcBitWidth);
KnownZero.zextOrTrunc(SrcBitWidth);
KnownOne.zextOrTrunc(SrcBitWidth);
ComputeMaskedBits(I->getOperand(0), MaskIn, KnownZero, KnownOne, Depth+1);
KnownZero.trunc(BitWidth);
KnownOne.trunc(BitWidth);
KnownZero.zextOrTrunc(BitWidth);
KnownOne.zextOrTrunc(BitWidth);
// Any top bits are known to be zero.
if (BitWidth > SrcBitWidth)
KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth);
return;
}
case Instruction::BitCast: {
const Type *SrcTy = I->getOperand(0)->getType();
if (SrcTy->isInteger()) {
if (SrcTy->isInteger() || isa<PointerType>(SrcTy)) {
ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
return;
}
break;
}
case Instruction::ZExt: {
// Compute the bits in the result that are not present in the input.
const IntegerType *SrcTy = cast<IntegerType>(I->getOperand(0)->getType());
uint32_t SrcBitWidth = SrcTy->getBitWidth();
APInt MaskIn(Mask);
MaskIn.trunc(SrcBitWidth);
KnownZero.trunc(SrcBitWidth);
KnownOne.trunc(SrcBitWidth);
ComputeMaskedBits(I->getOperand(0), MaskIn, KnownZero, KnownOne, Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
// The top bits are known to be zero.
KnownZero.zext(BitWidth);
KnownOne.zext(BitWidth);
KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth);
return;
}
case Instruction::SExt: {
// Compute the bits in the result that are not present in the input.
const IntegerType *SrcTy = cast<IntegerType>(I->getOperand(0)->getType());
@ -835,6 +890,32 @@ static void ComputeMaskedBits(Value *V, const APInt &Mask, APInt& KnownZero,
return;
}
break;
case Instruction::Sub: {
if (ConstantInt *CLHS = dyn_cast<ConstantInt>(I->getOperand(0))) {
// We know that the top bits of C-X are clear if X contains less bits
// than C (i.e. no wrap-around can happen). For example, 20-X is
// positive if we can prove that X is >= 0 and < 16.
if (!CLHS->getValue().isNegative()) {
unsigned NLZ = (CLHS->getValue()+1).countLeadingZeros();
// NLZ can't be BitWidth with no sign bit
APInt MaskV = APInt::getHighBitsSet(BitWidth, NLZ+1);
ComputeMaskedBits(I->getOperand(1), MaskV, KnownZero, KnownOne, Depth+1);
// If all of the MaskV bits are known to be zero, then we know the output
// top bits are zero, because we now know that the output is from [0-C].
if ((KnownZero & MaskV) == MaskV) {
unsigned NLZ2 = CLHS->getValue().countLeadingZeros();
// Top bits known zero.
KnownZero = APInt::getHighBitsSet(BitWidth, NLZ2) & Mask;
KnownOne = APInt(BitWidth, 0); // No one bits known.
} else {
KnownZero = KnownOne = APInt(BitWidth, 0); // Otherwise, nothing known.
}
return;
}
}
}
// fall through
case Instruction::Add: {
// If either the LHS or the RHS are Zero, the result is zero.
ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
@ -852,33 +933,6 @@ static void ComputeMaskedBits(Value *V, const APInt &Mask, APInt& KnownZero,
KnownOne = APInt(BitWidth, 0);
return;
}
case Instruction::Sub: {
ConstantInt *CLHS = dyn_cast<ConstantInt>(I->getOperand(0));
if (!CLHS) break;
// We know that the top bits of C-X are clear if X contains less bits
// than C (i.e. no wrap-around can happen). For example, 20-X is
// positive if we can prove that X is >= 0 and < 16.
if (CLHS->getValue().isNegative())
break;
unsigned NLZ = (CLHS->getValue()+1).countLeadingZeros();
// NLZ can't be BitWidth with no sign bit
APInt MaskV = APInt::getHighBitsSet(BitWidth, NLZ+1);
ComputeMaskedBits(I->getOperand(1), MaskV, KnownZero, KnownOne, Depth+1);
// If all of the MaskV bits are known to be zero, then we know the output
// top bits are zero, because we now know that the output is from [0-C].
if ((KnownZero & MaskV) == MaskV) {
unsigned NLZ2 = CLHS->getValue().countLeadingZeros();
// Top bits known zero.
KnownZero = APInt::getHighBitsSet(BitWidth, NLZ2) & Mask;
KnownOne = APInt(BitWidth, 0); // No one bits known.
} else {
KnownZero = KnownOne = APInt(BitWidth, 0); // Otherwise, nothing known.
}
return;
}
case Instruction::SRem:
if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) {
APInt RA = Rem->getValue();
@ -923,13 +977,124 @@ static void ComputeMaskedBits(Value *V, const APInt &Mask, APInt& KnownZero,
assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
}
break;
case Instruction::Alloca:
case Instruction::Malloc: {
AllocationInst *AI = cast<AllocationInst>(V);
unsigned Align = AI->getAlignment();
if (Align == 0 && TD) {
if (isa<AllocaInst>(AI))
Align = TD->getPrefTypeAlignment(AI->getType()->getElementType());
else if (isa<MallocInst>(AI)) {
// Malloc returns maximally aligned memory.
Align = TD->getABITypeAlignment(AI->getType()->getElementType());
Align =
std::max(Align,
(unsigned)TD->getABITypeAlignment(Type::DoubleTy));
Align =
std::max(Align,
(unsigned)TD->getABITypeAlignment(Type::Int64Ty));
}
}
if (Align > 0)
KnownZero = Mask & APInt::getLowBitsSet(BitWidth,
CountTrailingZeros_32(Align));
break;
}
case Instruction::GetElementPtr: {
// Analyze all of the subscripts of this getelementptr instruction
// to determine if we can prove known low zero bits.
APInt LocalMask = APInt::getAllOnesValue(BitWidth);
APInt LocalKnownZero(BitWidth, 0), LocalKnownOne(BitWidth, 0);
ComputeMaskedBits(I->getOperand(0), LocalMask,
LocalKnownZero, LocalKnownOne, Depth+1);
unsigned TrailZ = LocalKnownZero.countTrailingOnes();
gep_type_iterator GTI = gep_type_begin(I);
for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i, ++GTI) {
Value *Index = I->getOperand(i);
if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
// Handle struct member offset arithmetic.
if (!TD) return;
const StructLayout *SL = TD->getStructLayout(STy);
unsigned Idx = cast<ConstantInt>(Index)->getZExtValue();
uint64_t Offset = SL->getElementOffset(Idx);
TrailZ = std::min(TrailZ,
CountTrailingZeros_64(Offset));
} else {
// Handle array index arithmetic.
const Type *IndexedTy = GTI.getIndexedType();
if (!IndexedTy->isSized()) return;
unsigned GEPOpiBits = Index->getType()->getPrimitiveSizeInBits();
uint64_t TypeSize = TD ? TD->getABITypeSize(IndexedTy) : 1;
LocalMask = APInt::getAllOnesValue(GEPOpiBits);
LocalKnownZero = LocalKnownOne = APInt(GEPOpiBits, 0);
ComputeMaskedBits(Index, LocalMask,
LocalKnownZero, LocalKnownOne, Depth+1);
TrailZ = std::min(TrailZ,
CountTrailingZeros_64(TypeSize) +
LocalKnownZero.countTrailingOnes());
}
}
KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ) & Mask;
break;
}
case Instruction::PHI: {
PHINode *P = cast<PHINode>(I);
// Handle the case of a simple two-predecessor recurrence PHI.
// There's a lot more that could theoretically be done here, but
// this is sufficient to catch some interesting cases.
if (P->getNumIncomingValues() == 2) {
for (unsigned i = 0; i != 2; ++i) {
Value *L = P->getIncomingValue(i);
Value *R = P->getIncomingValue(!i);
User *LU = dyn_cast<User>(L);
unsigned Opcode = LU ? getOpcode(LU) : (unsigned)Instruction::UserOp1;
// Check for operations that have the property that if
// both their operands have low zero bits, the result
// will have low zero bits.
if (Opcode == Instruction::Add ||
Opcode == Instruction::Sub ||
Opcode == Instruction::And ||
Opcode == Instruction::Or ||
Opcode == Instruction::Mul) {
Value *LL = LU->getOperand(0);
Value *LR = LU->getOperand(1);
// Find a recurrence.
if (LL == I)
L = LR;
else if (LR == I)
L = LL;
else
break;
// Ok, we have a PHI of the form L op= R. Check for low
// zero bits.
APInt Mask2 = APInt::getAllOnesValue(BitWidth);
ComputeMaskedBits(R, Mask2, KnownZero2, KnownOne2, Depth+1);
Mask2 = APInt::getLowBitsSet(BitWidth,
KnownZero2.countTrailingOnes());
KnownOne2.clear();
KnownZero2.clear();
ComputeMaskedBits(L, Mask2, KnownZero2, KnownOne2, Depth+1);
KnownZero = Mask &
APInt::getLowBitsSet(BitWidth,
KnownZero2.countTrailingOnes());
break;
}
}
}
break;
}
}
}
/// MaskedValueIsZero - Return true if 'V & Mask' is known to be zero. We use
/// this predicate to simplify operations downstream. Mask is known to be zero
/// for bits that V cannot have.
static bool MaskedValueIsZero(Value *V, const APInt& Mask, unsigned Depth = 0) {
bool InstCombiner::MaskedValueIsZero(Value *V, const APInt& Mask,
unsigned Depth) {
APInt KnownZero(Mask.getBitWidth(), 0), KnownOne(Mask.getBitWidth(), 0);
ComputeMaskedBits(V, Mask, KnownZero, KnownOne, Depth);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
@ -6695,8 +6860,9 @@ Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI,
///
/// This is a truncation operation if Ty is smaller than V->getType(), or an
/// extension operation if Ty is larger.
static bool CanEvaluateInDifferentType(Value *V, const IntegerType *Ty,
unsigned CastOpc, int &NumCastsRemoved) {
bool InstCombiner::CanEvaluateInDifferentType(Value *V, const IntegerType *Ty,
unsigned CastOpc,
int &NumCastsRemoved) {
// We can always evaluate constants in another type.
if (isa<ConstantInt>(V))
return true;
@ -8062,94 +8228,83 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
return 0;
}
/// GetOrEnforceKnownAlignment - If the specified pointer has an alignment that
/// we can determine, return it, otherwise return 0. If PrefAlign is specified,
/// and it is more than the alignment of the ultimate object, see if we can
/// increase the alignment of the ultimate object, making this check succeed.
static unsigned GetOrEnforceKnownAlignment(Value *V, TargetData *TD,
unsigned PrefAlign = 0) {
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
unsigned Align = GV->getAlignment();
if (Align == 0 && TD && GV->getType()->getElementType()->isSized())
Align = TD->getPrefTypeAlignment(GV->getType()->getElementType());
/// EnforceKnownAlignment - If the specified pointer points to an object that
/// we control, modify the object's alignment to PrefAlign. This isn't
/// often possible though. If alignment is important, a more reliable approach
/// is to simply align all global variables and allocation instructions to
/// their preferred alignment from the beginning.
///
static unsigned EnforceKnownAlignment(Value *V,
unsigned Align, unsigned PrefAlign) {
// If there is a large requested alignment and we can, bump up the alignment
// of the global.
if (PrefAlign > Align && GV->hasInitializer()) {
GV->setAlignment(PrefAlign);
Align = PrefAlign;
}
return Align;
} else if (AllocationInst *AI = dyn_cast<AllocationInst>(V)) {
unsigned Align = AI->getAlignment();
if (Align == 0 && TD) {
if (isa<AllocaInst>(AI))
Align = TD->getPrefTypeAlignment(AI->getType()->getElementType());
else if (isa<MallocInst>(AI)) {
// Malloc returns maximally aligned memory.
Align = TD->getABITypeAlignment(AI->getType()->getElementType());
Align =
std::max(Align,
(unsigned)TD->getABITypeAlignment(Type::DoubleTy));
Align =
std::max(Align,
(unsigned)TD->getABITypeAlignment(Type::Int64Ty));
}
}
// If there is a requested alignment and if this is an alloca, round up. We
// don't do this for malloc, because some systems can't respect the request.
if (PrefAlign > Align && isa<AllocaInst>(AI)) {
AI->setAlignment(PrefAlign);
Align = PrefAlign;
}
return Align;
} else if (isa<BitCastInst>(V) ||
(isa<ConstantExpr>(V) &&
cast<ConstantExpr>(V)->getOpcode() == Instruction::BitCast)) {
return GetOrEnforceKnownAlignment(cast<User>(V)->getOperand(0),
TD, PrefAlign);
} else if (User *GEPI = dyn_castGetElementPtr(V)) {
User *U = dyn_cast<User>(V);
if (!U) return Align;
switch (getOpcode(U)) {
default: break;
case Instruction::BitCast:
return EnforceKnownAlignment(U->getOperand(0), Align, PrefAlign);
case Instruction::GetElementPtr: {
// If all indexes are zero, it is just the alignment of the base pointer.
bool AllZeroOperands = true;
for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
if (!isa<Constant>(GEPI->getOperand(i)) ||
!cast<Constant>(GEPI->getOperand(i))->isNullValue()) {
for (unsigned i = 1, e = U->getNumOperands(); i != e; ++i)
if (!isa<Constant>(U->getOperand(i)) ||
!cast<Constant>(U->getOperand(i))->isNullValue()) {
AllZeroOperands = false;
break;
}
if (AllZeroOperands) {
// Treat this like a bitcast.
return GetOrEnforceKnownAlignment(GEPI->getOperand(0), TD, PrefAlign);
return EnforceKnownAlignment(U->getOperand(0), Align, PrefAlign);
}
unsigned BaseAlignment = GetOrEnforceKnownAlignment(GEPI->getOperand(0),TD);
if (BaseAlignment == 0) return 0;
// Otherwise, if the base alignment is >= the alignment we expect for the
// base pointer type, then we know that the resultant pointer is aligned at
// least as much as its type requires.
if (!TD) return 0;
const Type *BasePtrTy = GEPI->getOperand(0)->getType();
const PointerType *PtrTy = cast<PointerType>(BasePtrTy);
unsigned Align = TD->getABITypeAlignment(PtrTy->getElementType());
if (Align <= BaseAlignment) {
const Type *GEPTy = GEPI->getType();
const PointerType *GEPPtrTy = cast<PointerType>(GEPTy);
Align = std::min(Align, (unsigned)
TD->getABITypeAlignment(GEPPtrTy->getElementType()));
return Align;
}
return 0;
break;
}
return 0;
}
if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
// If there is a large requested alignment and we can, bump up the alignment
// of the global.
if (!GV->isDeclaration()) {
GV->setAlignment(PrefAlign);
Align = PrefAlign;
}
} else if (AllocationInst *AI = dyn_cast<AllocationInst>(V)) {
// If there is a requested alignment and if this is an alloca, round up. We
// don't do this for malloc, because some systems can't respect the request.
if (isa<AllocaInst>(AI)) {
AI->setAlignment(PrefAlign);
Align = PrefAlign;
}
}
return Align;
}
/// GetOrEnforceKnownAlignment - If the specified pointer has an alignment that
/// we can determine, return it, otherwise return 0. If PrefAlign is specified,
/// and it is more than the alignment of the ultimate object, see if we can
/// increase the alignment of the ultimate object, making this check succeed.
unsigned InstCombiner::GetOrEnforceKnownAlignment(Value *V,
unsigned PrefAlign) {
unsigned BitWidth = TD ? TD->getTypeSizeInBits(V->getType()) :
sizeof(PrefAlign) * CHAR_BIT;
APInt Mask = APInt::getAllOnesValue(BitWidth);
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
ComputeMaskedBits(V, Mask, KnownZero, KnownOne);
unsigned TrailZ = KnownZero.countTrailingOnes();
unsigned Align = 1u << std::min(BitWidth - 1, TrailZ);
if (PrefAlign > Align)
Align = EnforceKnownAlignment(V, Align, PrefAlign);
// We don't need to make any adjustment.
return Align;
}
Instruction *InstCombiner::SimplifyMemTransfer(MemIntrinsic *MI) {
unsigned DstAlign = GetOrEnforceKnownAlignment(MI->getOperand(1), TD);
unsigned SrcAlign = GetOrEnforceKnownAlignment(MI->getOperand(2), TD);
unsigned DstAlign = GetOrEnforceKnownAlignment(MI->getOperand(1));
unsigned SrcAlign = GetOrEnforceKnownAlignment(MI->getOperand(2));
unsigned MinAlign = std::min(DstAlign, SrcAlign);
unsigned CopyAlign = MI->getAlignment()->getZExtValue();
@ -8270,7 +8425,7 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
if (Instruction *I = SimplifyMemTransfer(MI))
return I;
} else if (isa<MemSetInst>(MI)) {
unsigned Alignment = GetOrEnforceKnownAlignment(MI->getDest(), TD);
unsigned Alignment = GetOrEnforceKnownAlignment(MI->getDest());
if (MI->getAlignment()->getZExtValue() < Alignment) {
MI->setAlignment(ConstantInt::get(Type::Int32Ty, Alignment));
Changed = true;
@ -8288,7 +8443,7 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
case Intrinsic::x86_sse2_loadu_dq:
// Turn PPC lvx -> load if the pointer is known aligned.
// Turn X86 loadups -> load if the pointer is known aligned.
if (GetOrEnforceKnownAlignment(II->getOperand(1), TD, 16) >= 16) {
if (GetOrEnforceKnownAlignment(II->getOperand(1), 16) >= 16) {
Value *Ptr = InsertBitCastBefore(II->getOperand(1),
PointerType::getUnqual(II->getType()),
CI);
@ -8298,7 +8453,7 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
case Intrinsic::ppc_altivec_stvx:
case Intrinsic::ppc_altivec_stvxl:
// Turn stvx -> store if the pointer is known aligned.
if (GetOrEnforceKnownAlignment(II->getOperand(2), TD, 16) >= 16) {
if (GetOrEnforceKnownAlignment(II->getOperand(2), 16) >= 16) {
const Type *OpPtrTy =
PointerType::getUnqual(II->getOperand(1)->getType());
Value *Ptr = InsertBitCastBefore(II->getOperand(2), OpPtrTy, CI);
@ -8310,7 +8465,7 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
case Intrinsic::x86_sse2_storeu_dq:
case Intrinsic::x86_sse2_storel_dq:
// Turn X86 storeu -> store if the pointer is known aligned.
if (GetOrEnforceKnownAlignment(II->getOperand(1), TD, 16) >= 16) {
if (GetOrEnforceKnownAlignment(II->getOperand(1), 16) >= 16) {
const Type *OpPtrTy =
PointerType::getUnqual(II->getOperand(2)->getType());
Value *Ptr = InsertBitCastBefore(II->getOperand(1), OpPtrTy, CI);
@ -9762,8 +9917,10 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
Value *Op = LI.getOperand(0);
// Attempt to improve the alignment.
unsigned KnownAlign = GetOrEnforceKnownAlignment(Op, TD);
if (KnownAlign > LI.getAlignment())
unsigned KnownAlign = GetOrEnforceKnownAlignment(Op);
if (KnownAlign >
(LI.getAlignment() == 0 ? TD->getABITypeAlignment(LI.getType()) :
LI.getAlignment()))
LI.setAlignment(KnownAlign);
// load (cast X) --> cast (load X) iff safe
@ -9980,8 +10137,10 @@ Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
}
// Attempt to improve the alignment.
unsigned KnownAlign = GetOrEnforceKnownAlignment(Ptr, TD);
if (KnownAlign > SI.getAlignment())
unsigned KnownAlign = GetOrEnforceKnownAlignment(Ptr);
if (KnownAlign >
(SI.getAlignment() == 0 ? TD->getABITypeAlignment(Val->getType()) :
SI.getAlignment()))
SI.setAlignment(KnownAlign);
// Do really simple DSE, to catch cases where there are several consequtive

43
test/Transforms/InstCombine/align-2d-gep.ll Normal file
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@ -0,0 +1,43 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {align 16} | count 1
; A multi-dimensional array in a nested loop doing vector stores that
; aren't yet aligned. Instcombine can understand the addressing in the
; Nice case to prove 16 byte alignment. In the Awkward case, the inner
; array dimension is not even, so the stores to it won't always be
; aligned. Instcombine should prove alignment in exactly one of the two
; stores.
@Nice = global [1001 x [20000 x double]] zeroinitializer, align 32
@Awkward = global [1001 x [20001 x double]] zeroinitializer, align 32
define void @foo() nounwind {
entry:
br label %bb7.outer
bb7.outer:
%i = phi i64 [ 0, %entry ], [ %indvar.next26, %bb11 ]
br label %bb1
bb1:
%j = phi i64 [ 0, %bb7.outer ], [ %indvar.next, %bb1 ]
%t4 = getelementptr [1001 x [20000 x double]]* @Nice, i64 0, i64 %i, i64 %j
%q = bitcast double* %t4 to <2 x double>*
store <2 x double><double 0.0, double 0.0>, <2 x double>* %q, align 8
%s4 = getelementptr [1001 x [20001 x double]]* @Awkward, i64 0, i64 %i, i64 %j
%r = bitcast double* %s4 to <2 x double>*
store <2 x double><double 0.0, double 0.0>, <2 x double>* %r, align 8
%indvar.next = add i64 %j, 2
%exitcond = icmp eq i64 %indvar.next, 557
br i1 %exitcond, label %bb11, label %bb1
bb11:
%indvar.next26 = add i64 %i, 1
%exitcond27 = icmp eq i64 %indvar.next26, 991
br i1 %exitcond27, label %return.split, label %bb7.outer
return.split:
ret void
}

30
test/Transforms/InstCombine/align-addr.ll Normal file
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@ -0,0 +1,30 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {align 16} | count 1
; Instcombine should be able to prove vector alignment in the
; presence of a few mild address computation tricks.
define void @foo(i8* %b, i64 %n, i64 %u, i64 %y) nounwind {
entry:
%c = ptrtoint i8* %b to i64
%d = and i64 %c, -16
%e = inttoptr i64 %d to double*
%v = mul i64 %u, 2
%z = and i64 %y, -2
%t1421 = icmp eq i64 %n, 0
br i1 %t1421, label %return, label %bb
bb:
%i = phi i64 [ %indvar.next, %bb ], [ 20, %entry ]
%j = mul i64 %i, %v
%h = add i64 %j, %z
%t8 = getelementptr double* %e, i64 %h
%p = bitcast double* %t8 to <2 x double>*
store <2 x double><double 0.0, double 0.0>, <2 x double>* %p, align 8
%indvar.next = add i64 %i, 1
%exitcond = icmp eq i64 %indvar.next, %n
br i1 %exitcond, label %return, label %bb
return:
ret void
}