//===----------------------------------------------------------------------===//
#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Analysis/InstructionSimplify.h"
-#include "llvm/Constants.h"
-#include "llvm/Instructions.h"
-#include "llvm/GlobalVariable.h"
-#include "llvm/GlobalAlias.h"
-#include "llvm/IntrinsicInst.h"
-#include "llvm/LLVMContext.h"
-#include "llvm/Operator.h"
-#include "llvm/Target/TargetData.h"
-#include "llvm/Support/GetElementPtrTypeIterator.h"
+#include "llvm/Analysis/MemoryBuiltins.h"
+#include "llvm/IR/ConstantRange.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/GetElementPtrTypeIterator.h"
+#include "llvm/IR/GlobalAlias.h"
+#include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Metadata.h"
+#include "llvm/IR/Operator.h"
+#include "llvm/IR/PatternMatch.h"
#include "llvm/Support/MathExtras.h"
-#include "llvm/Support/PatternMatch.h"
-#include "llvm/ADT/SmallPtrSet.h"
#include <cstring>
using namespace llvm;
using namespace llvm::PatternMatch;
/// getBitWidth - Returns the bitwidth of the given scalar or pointer type (if
/// unknown returns 0). For vector types, returns the element type's bitwidth.
-static unsigned getBitWidth(Type *Ty, const TargetData *TD) {
+static unsigned getBitWidth(Type *Ty, const DataLayout *TD) {
if (unsigned BitWidth = Ty->getScalarSizeInBits())
return BitWidth;
- assert(isa<PointerType>(Ty) && "Expected a pointer type!");
- return TD ? TD->getPointerSizeInBits() : 0;
+
+ return TD ? TD->getPointerTypeSizeInBits(Ty) : 0;
+}
+
+static void ComputeMaskedBitsAddSub(bool Add, Value *Op0, Value *Op1, bool NSW,
+ APInt &KnownZero, APInt &KnownOne,
+ APInt &KnownZero2, APInt &KnownOne2,
+ const DataLayout *TD, unsigned Depth) {
+ if (!Add) {
+ if (ConstantInt *CLHS = dyn_cast<ConstantInt>(Op0)) {
+ // 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 BitWidth = KnownZero.getBitWidth();
+ unsigned NLZ = (CLHS->getValue()+1).countLeadingZeros();
+ // NLZ can't be BitWidth with no sign bit
+ APInt MaskV = APInt::getHighBitsSet(BitWidth, NLZ+1);
+ llvm::ComputeMaskedBits(Op1, KnownZero2, KnownOne2, TD, 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 ((KnownZero2 & MaskV) == MaskV) {
+ unsigned NLZ2 = CLHS->getValue().countLeadingZeros();
+ // Top bits known zero.
+ KnownZero = APInt::getHighBitsSet(BitWidth, NLZ2);
+ }
+ }
+ }
+ }
+
+ unsigned BitWidth = KnownZero.getBitWidth();
+
+ // If one of the operands has trailing zeros, then the bits that the
+ // other operand has in those bit positions will be preserved in the
+ // result. For an add, this works with either operand. For a subtract,
+ // this only works if the known zeros are in the right operand.
+ APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0);
+ llvm::ComputeMaskedBits(Op0, LHSKnownZero, LHSKnownOne, TD, Depth+1);
+ assert((LHSKnownZero & LHSKnownOne) == 0 &&
+ "Bits known to be one AND zero?");
+ unsigned LHSKnownZeroOut = LHSKnownZero.countTrailingOnes();
+
+ llvm::ComputeMaskedBits(Op1, KnownZero2, KnownOne2, TD, Depth+1);
+ assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
+ unsigned RHSKnownZeroOut = KnownZero2.countTrailingOnes();
+
+ // Determine which operand has more trailing zeros, and use that
+ // many bits from the other operand.
+ if (LHSKnownZeroOut > RHSKnownZeroOut) {
+ if (Add) {
+ APInt Mask = APInt::getLowBitsSet(BitWidth, LHSKnownZeroOut);
+ KnownZero |= KnownZero2 & Mask;
+ KnownOne |= KnownOne2 & Mask;
+ } else {
+ // If the known zeros are in the left operand for a subtract,
+ // fall back to the minimum known zeros in both operands.
+ KnownZero |= APInt::getLowBitsSet(BitWidth,
+ std::min(LHSKnownZeroOut,
+ RHSKnownZeroOut));
+ }
+ } else if (RHSKnownZeroOut >= LHSKnownZeroOut) {
+ APInt Mask = APInt::getLowBitsSet(BitWidth, RHSKnownZeroOut);
+ KnownZero |= LHSKnownZero & Mask;
+ KnownOne |= LHSKnownOne & Mask;
+ }
+
+ // Are we still trying to solve for the sign bit?
+ if (!KnownZero.isNegative() && !KnownOne.isNegative()) {
+ if (NSW) {
+ if (Add) {
+ // Adding two positive numbers can't wrap into negative
+ if (LHSKnownZero.isNegative() && KnownZero2.isNegative())
+ KnownZero |= APInt::getSignBit(BitWidth);
+ // and adding two negative numbers can't wrap into positive.
+ else if (LHSKnownOne.isNegative() && KnownOne2.isNegative())
+ KnownOne |= APInt::getSignBit(BitWidth);
+ } else {
+ // Subtracting a negative number from a positive one can't wrap
+ if (LHSKnownZero.isNegative() && KnownOne2.isNegative())
+ KnownZero |= APInt::getSignBit(BitWidth);
+ // neither can subtracting a positive number from a negative one.
+ else if (LHSKnownOne.isNegative() && KnownZero2.isNegative())
+ KnownOne |= APInt::getSignBit(BitWidth);
+ }
+ }
+ }
+}
+
+static void ComputeMaskedBitsMul(Value *Op0, Value *Op1, bool NSW,
+ APInt &KnownZero, APInt &KnownOne,
+ APInt &KnownZero2, APInt &KnownOne2,
+ const DataLayout *TD, unsigned Depth) {
+ unsigned BitWidth = KnownZero.getBitWidth();
+ ComputeMaskedBits(Op1, KnownZero, KnownOne, TD, Depth+1);
+ ComputeMaskedBits(Op0, KnownZero2, KnownOne2, TD, Depth+1);
+ assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
+ assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
+
+ bool isKnownNegative = false;
+ bool isKnownNonNegative = false;
+ // If the multiplication is known not to overflow, compute the sign bit.
+ if (NSW) {
+ if (Op0 == Op1) {
+ // The product of a number with itself is non-negative.
+ isKnownNonNegative = true;
+ } else {
+ bool isKnownNonNegativeOp1 = KnownZero.isNegative();
+ bool isKnownNonNegativeOp0 = KnownZero2.isNegative();
+ bool isKnownNegativeOp1 = KnownOne.isNegative();
+ bool isKnownNegativeOp0 = KnownOne2.isNegative();
+ // The product of two numbers with the same sign is non-negative.
+ isKnownNonNegative = (isKnownNegativeOp1 && isKnownNegativeOp0) ||
+ (isKnownNonNegativeOp1 && isKnownNonNegativeOp0);
+ // The product of a negative number and a non-negative number is either
+ // negative or zero.
+ if (!isKnownNonNegative)
+ isKnownNegative = (isKnownNegativeOp1 && isKnownNonNegativeOp0 &&
+ isKnownNonZero(Op0, TD, Depth)) ||
+ (isKnownNegativeOp0 && isKnownNonNegativeOp1 &&
+ isKnownNonZero(Op1, TD, Depth));
+ }
+ }
+
+ // If low bits are zero in either operand, output low known-0 bits.
+ // Also compute a conserative estimate for high known-0 bits.
+ // More trickiness is possible, but this is sufficient for the
+ // interesting case of alignment computation.
+ KnownOne.clearAllBits();
+ unsigned TrailZ = KnownZero.countTrailingOnes() +
+ KnownZero2.countTrailingOnes();
+ unsigned LeadZ = std::max(KnownZero.countLeadingOnes() +
+ KnownZero2.countLeadingOnes(),
+ BitWidth) - BitWidth;
+
+ TrailZ = std::min(TrailZ, BitWidth);
+ LeadZ = std::min(LeadZ, BitWidth);
+ KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ) |
+ APInt::getHighBitsSet(BitWidth, LeadZ);
+
+ // Only make use of no-wrap flags if we failed to compute the sign bit
+ // directly. This matters if the multiplication always overflows, in
+ // which case we prefer to follow the result of the direct computation,
+ // though as the program is invoking undefined behaviour we can choose
+ // whatever we like here.
+ if (isKnownNonNegative && !KnownOne.isNegative())
+ KnownZero.setBit(BitWidth - 1);
+ else if (isKnownNegative && !KnownZero.isNegative())
+ KnownOne.setBit(BitWidth - 1);
}
-/// ComputeMaskedBits - Determine which of the bits specified in Mask are
-/// known to be either zero or one and return them in the KnownZero/KnownOne
-/// bit sets. This code only analyzes bits in Mask, in order to short-circuit
-/// processing.
+void llvm::computeMaskedBitsLoad(const MDNode &Ranges, APInt &KnownZero) {
+ unsigned BitWidth = KnownZero.getBitWidth();
+ unsigned NumRanges = Ranges.getNumOperands() / 2;
+ assert(NumRanges >= 1);
+
+ // Use the high end of the ranges to find leading zeros.
+ unsigned MinLeadingZeros = BitWidth;
+ for (unsigned i = 0; i < NumRanges; ++i) {
+ ConstantInt *Lower = cast<ConstantInt>(Ranges.getOperand(2*i + 0));
+ ConstantInt *Upper = cast<ConstantInt>(Ranges.getOperand(2*i + 1));
+ ConstantRange Range(Lower->getValue(), Upper->getValue());
+ if (Range.isWrappedSet())
+ MinLeadingZeros = 0; // -1 has no zeros
+ unsigned LeadingZeros = (Upper->getValue() - 1).countLeadingZeros();
+ MinLeadingZeros = std::min(LeadingZeros, MinLeadingZeros);
+ }
+
+ KnownZero = APInt::getHighBitsSet(BitWidth, MinLeadingZeros);
+}
+/// ComputeMaskedBits - Determine which of the bits are known to be either zero
+/// or one and return them in the KnownZero/KnownOne bit sets.
+///
/// NOTE: we cannot consider 'undef' to be "IsZero" here. The problem is that
/// we cannot optimize based on the assumption that it is zero without changing
/// it to be an explicit zero. If we don't change it to zero, other code could
///
/// This function is defined on values with integer type, values with pointer
/// type (but only if TD is non-null), and vectors of integers. In the case
-/// where V is a vector, the mask, known zero, and known one values are the
+/// where V is a vector, known zero, and known one values are the
/// same width as the vector element, and the bit is set only if it is true
/// for all of the elements in the vector.
-void llvm::ComputeMaskedBits(Value *V, const APInt &Mask,
- APInt &KnownZero, APInt &KnownOne,
- const TargetData *TD, unsigned Depth) {
+void llvm::ComputeMaskedBits(Value *V, APInt &KnownZero, APInt &KnownOne,
+ const DataLayout *TD, unsigned Depth) {
assert(V && "No Value?");
assert(Depth <= MaxDepth && "Limit Search Depth");
- unsigned BitWidth = Mask.getBitWidth();
- assert((V->getType()->isIntOrIntVectorTy() || V->getType()->isPointerTy())
- && "Not integer or pointer type!");
+ unsigned BitWidth = KnownZero.getBitWidth();
+
+ assert((V->getType()->isIntOrIntVectorTy() ||
+ V->getType()->getScalarType()->isPointerTy()) &&
+ "Not integer or pointer type!");
assert((!TD ||
TD->getTypeSizeInBits(V->getType()->getScalarType()) == BitWidth) &&
(!V->getType()->isIntOrIntVectorTy() ||
V->getType()->getScalarSizeInBits() == BitWidth) &&
- KnownZero.getBitWidth() == BitWidth &&
+ KnownZero.getBitWidth() == BitWidth &&
KnownOne.getBitWidth() == BitWidth &&
"V, Mask, KnownOne and KnownZero should have same BitWidth");
if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
// We know all of the bits for a constant!
- KnownOne = CI->getValue() & Mask;
- KnownZero = ~KnownOne & Mask;
+ KnownOne = CI->getValue();
+ KnownZero = ~KnownOne;
return;
}
// Null and aggregate-zero are all-zeros.
if (isa<ConstantPointerNull>(V) ||
isa<ConstantAggregateZero>(V)) {
KnownOne.clearAllBits();
- KnownZero = Mask;
+ KnownZero = APInt::getAllOnesValue(BitWidth);
return;
}
// Handle a constant vector by taking the intersection of the known bits of
- // each element.
- if (ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
+ // each element. There is no real need to handle ConstantVector here, because
+ // we don't handle undef in any particularly useful way.
+ if (ConstantDataSequential *CDS = dyn_cast<ConstantDataSequential>(V)) {
+ // We know that CDS must be a vector of integers. Take the intersection of
+ // each element.
KnownZero.setAllBits(); KnownOne.setAllBits();
- for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) {
- APInt KnownZero2(BitWidth, 0), KnownOne2(BitWidth, 0);
- ComputeMaskedBits(CV->getOperand(i), Mask, KnownZero2, KnownOne2,
- TD, Depth);
- KnownZero &= KnownZero2;
- KnownOne &= KnownOne2;
+ APInt Elt(KnownZero.getBitWidth(), 0);
+ for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i) {
+ Elt = CDS->getElementAsInteger(i);
+ KnownZero &= ~Elt;
+ KnownOne &= Elt;
}
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()) {
- Type *ObjectType = GV->getType()->getElementType();
- // If the object is defined in the current Module, we'll be giving
- // it the preferred alignment. Otherwise, we have to assume that it
- // may only have the minimum ABI alignment.
- if (!GV->isDeclaration() && !GV->mayBeOverridden())
- Align = TD->getPrefTypeAlignment(ObjectType);
- else
- Align = TD->getABITypeAlignment(ObjectType);
+ if (Align == 0 && TD) {
+ if (GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV)) {
+ Type *ObjectType = GVar->getType()->getElementType();
+ if (ObjectType->isSized()) {
+ // If the object is defined in the current Module, we'll be giving
+ // it the preferred alignment. Otherwise, we have to assume that it
+ // may only have the minimum ABI alignment.
+ if (!GVar->isDeclaration() && !GVar->isWeakForLinker())
+ Align = TD->getPreferredAlignment(GVar);
+ else
+ Align = TD->getABITypeAlignment(ObjectType);
+ }
+ }
}
if (Align > 0)
- KnownZero = Mask & APInt::getLowBitsSet(BitWidth,
- CountTrailingZeros_32(Align));
+ KnownZero = APInt::getLowBitsSet(BitWidth,
+ countTrailingZeros(Align));
else
KnownZero.clearAllBits();
KnownOne.clearAllBits();
if (GA->mayBeOverridden()) {
KnownZero.clearAllBits(); KnownOne.clearAllBits();
} else {
- ComputeMaskedBits(GA->getAliasee(), Mask, KnownZero, KnownOne,
- TD, Depth+1);
+ ComputeMaskedBits(GA->getAliasee(), KnownZero, KnownOne, TD, Depth+1);
}
return;
}
-
+
if (Argument *A = dyn_cast<Argument>(V)) {
- // Get alignment information off byval arguments if specified in the IR.
- if (A->hasByValAttr())
- if (unsigned Align = A->getParamAlignment())
- KnownZero = Mask & APInt::getLowBitsSet(BitWidth,
- CountTrailingZeros_32(Align));
+ unsigned Align = 0;
+
+ if (A->hasByValOrInAllocaAttr()) {
+ // Get alignment information off byval/inalloca arguments if specified in
+ // the IR.
+ Align = A->getParamAlignment();
+ } else if (TD && A->hasStructRetAttr()) {
+ // An sret parameter has at least the ABI alignment of the return type.
+ Type *EltTy = cast<PointerType>(A->getType())->getElementType();
+ if (EltTy->isSized())
+ Align = TD->getABITypeAlignment(EltTy);
+ }
+
+ if (Align)
+ KnownZero = APInt::getLowBitsSet(BitWidth, countTrailingZeros(Align));
return;
}
// Start out not knowing anything.
KnownZero.clearAllBits(); KnownOne.clearAllBits();
- if (Depth == MaxDepth || Mask == 0)
+ if (Depth == MaxDepth)
return; // Limit search depth.
Operator *I = dyn_cast<Operator>(V);
APInt KnownZero2(KnownZero), KnownOne2(KnownOne);
switch (I->getOpcode()) {
default: break;
+ case Instruction::Load:
+ if (MDNode *MD = cast<LoadInst>(I)->getMetadata(LLVMContext::MD_range))
+ computeMaskedBitsLoad(*MD, KnownZero);
+ return;
case Instruction::And: {
// If either the LHS or the RHS are Zero, the result is zero.
- ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, TD, Depth+1);
- APInt Mask2(Mask & ~KnownZero);
- ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD,
- Depth+1);
- assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
- assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
-
+ ComputeMaskedBits(I->getOperand(1), KnownZero, KnownOne, TD, Depth+1);
+ ComputeMaskedBits(I->getOperand(0), KnownZero2, KnownOne2, TD, Depth+1);
+ assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
+ assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
+
// Output known-1 bits are only known if set in both the LHS & RHS.
KnownOne &= KnownOne2;
// Output known-0 are known to be clear if zero in either the LHS | RHS.
return;
}
case Instruction::Or: {
- ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, TD, Depth+1);
- APInt Mask2(Mask & ~KnownOne);
- ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD,
- Depth+1);
- assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
- assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
-
+ ComputeMaskedBits(I->getOperand(1), KnownZero, KnownOne, TD, Depth+1);
+ ComputeMaskedBits(I->getOperand(0), KnownZero2, KnownOne2, TD, Depth+1);
+ assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
+ assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
+
// Output known-0 bits are only known if clear in both the LHS & RHS.
KnownZero &= KnownZero2;
// Output known-1 are known to be set if set in either the LHS | RHS.
return;
}
case Instruction::Xor: {
- ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, TD, Depth+1);
- ComputeMaskedBits(I->getOperand(0), Mask, KnownZero2, KnownOne2, TD,
- Depth+1);
- assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
- assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
-
+ ComputeMaskedBits(I->getOperand(1), KnownZero, KnownOne, TD, Depth+1);
+ ComputeMaskedBits(I->getOperand(0), KnownZero2, KnownOne2, TD, Depth+1);
+ assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
+ assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
+
// Output known-0 bits are known if clear or set in both the LHS & RHS.
APInt KnownZeroOut = (KnownZero & KnownZero2) | (KnownOne & KnownOne2);
// Output known-1 are known to be set if set in only one of the LHS, RHS.
return;
}
case Instruction::Mul: {
- APInt Mask2 = APInt::getAllOnesValue(BitWidth);
- ComputeMaskedBits(I->getOperand(1), Mask2, KnownZero, KnownOne, TD,Depth+1);
- ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD,
- 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.
- // Also compute a conserative estimate for high known-0 bits.
- // More trickiness is possible, but this is sufficient for the
- // interesting case of alignment computation.
- KnownOne.clearAllBits();
- unsigned TrailZ = KnownZero.countTrailingOnes() +
- KnownZero2.countTrailingOnes();
- unsigned LeadZ = std::max(KnownZero.countLeadingOnes() +
- KnownZero2.countLeadingOnes(),
- BitWidth) - BitWidth;
-
- TrailZ = std::min(TrailZ, BitWidth);
- LeadZ = std::min(LeadZ, BitWidth);
- KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ) |
- APInt::getHighBitsSet(BitWidth, LeadZ);
- KnownZero &= Mask;
- return;
+ bool NSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap();
+ ComputeMaskedBitsMul(I->getOperand(0), I->getOperand(1), NSW,
+ KnownZero, KnownOne, KnownZero2, KnownOne2, TD, Depth);
+ break;
}
case Instruction::UDiv: {
// For the purposes of computing leading zeros we can conservatively
// treat a udiv as a logical right shift by the power of 2 known to
// be less than the denominator.
- APInt AllOnes = APInt::getAllOnesValue(BitWidth);
- ComputeMaskedBits(I->getOperand(0),
- AllOnes, KnownZero2, KnownOne2, TD, Depth+1);
+ ComputeMaskedBits(I->getOperand(0), KnownZero2, KnownOne2, TD, Depth+1);
unsigned LeadZ = KnownZero2.countLeadingOnes();
KnownOne2.clearAllBits();
KnownZero2.clearAllBits();
- ComputeMaskedBits(I->getOperand(1),
- AllOnes, KnownZero2, KnownOne2, TD, Depth+1);
+ ComputeMaskedBits(I->getOperand(1), KnownZero2, KnownOne2, TD, Depth+1);
unsigned RHSUnknownLeadingOnes = KnownOne2.countLeadingZeros();
if (RHSUnknownLeadingOnes != BitWidth)
LeadZ = std::min(BitWidth,
LeadZ + BitWidth - RHSUnknownLeadingOnes - 1);
- KnownZero = APInt::getHighBitsSet(BitWidth, LeadZ) & Mask;
+ KnownZero = APInt::getHighBitsSet(BitWidth, LeadZ);
return;
}
case Instruction::Select:
- ComputeMaskedBits(I->getOperand(2), Mask, KnownZero, KnownOne, TD, Depth+1);
- ComputeMaskedBits(I->getOperand(1), Mask, KnownZero2, KnownOne2, TD,
+ ComputeMaskedBits(I->getOperand(2), KnownZero, KnownOne, TD, Depth+1);
+ ComputeMaskedBits(I->getOperand(1), KnownZero2, KnownOne2, TD,
Depth+1);
- assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
- assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
+ assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
+ assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
// Only known if known in both the LHS and RHS.
KnownOne &= KnownOne2;
case Instruction::ZExt:
case Instruction::Trunc: {
Type *SrcTy = I->getOperand(0)->getType();
-
+
unsigned SrcBitWidth;
// Note that we handle pointer operands here because of inttoptr/ptrtoint
// which fall through here.
- if (SrcTy->isPointerTy())
- SrcBitWidth = TD->getTypeSizeInBits(SrcTy);
- else
+ if(TD) {
+ SrcBitWidth = TD->getTypeSizeInBits(SrcTy->getScalarType());
+ } else {
SrcBitWidth = SrcTy->getScalarSizeInBits();
-
- APInt MaskIn = Mask.zextOrTrunc(SrcBitWidth);
+ if (!SrcBitWidth) return;
+ }
+
+ assert(SrcBitWidth && "SrcBitWidth can't be zero");
KnownZero = KnownZero.zextOrTrunc(SrcBitWidth);
KnownOne = KnownOne.zextOrTrunc(SrcBitWidth);
- ComputeMaskedBits(I->getOperand(0), MaskIn, KnownZero, KnownOne, TD,
- Depth+1);
+ ComputeMaskedBits(I->getOperand(0), KnownZero, KnownOne, TD, Depth+1);
KnownZero = KnownZero.zextOrTrunc(BitWidth);
KnownOne = KnownOne.zextOrTrunc(BitWidth);
// Any top bits are known to be zero.
// TODO: For now, not handling conversions like:
// (bitcast i64 %x to <2 x i32>)
!I->getType()->isVectorTy()) {
- ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, TD,
- Depth+1);
+ ComputeMaskedBits(I->getOperand(0), KnownZero, KnownOne, TD, Depth+1);
return;
}
break;
case Instruction::SExt: {
// Compute the bits in the result that are not present in the input.
unsigned SrcBitWidth = I->getOperand(0)->getType()->getScalarSizeInBits();
-
- APInt MaskIn = Mask.trunc(SrcBitWidth);
+
KnownZero = KnownZero.trunc(SrcBitWidth);
KnownOne = KnownOne.trunc(SrcBitWidth);
- ComputeMaskedBits(I->getOperand(0), MaskIn, KnownZero, KnownOne, TD,
- Depth+1);
- assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
+ ComputeMaskedBits(I->getOperand(0), KnownZero, KnownOne, TD, Depth+1);
+ assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
KnownZero = KnownZero.zext(BitWidth);
KnownOne = KnownOne.zext(BitWidth);
// (shl X, C1) & C2 == 0 iff (X & C2 >>u C1) == 0
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
uint64_t ShiftAmt = SA->getLimitedValue(BitWidth);
- APInt Mask2(Mask.lshr(ShiftAmt));
- ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero, KnownOne, TD,
- Depth+1);
- assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
+ ComputeMaskedBits(I->getOperand(0), KnownZero, KnownOne, TD, Depth+1);
+ assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
KnownZero <<= ShiftAmt;
KnownOne <<= ShiftAmt;
KnownZero |= APInt::getLowBitsSet(BitWidth, ShiftAmt); // low bits known 0
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
// Compute the new bits that are at the top now.
uint64_t ShiftAmt = SA->getLimitedValue(BitWidth);
-
+
// Unsigned shift right.
- APInt Mask2(Mask.shl(ShiftAmt));
- ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero,KnownOne, TD,
- Depth+1);
- assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
+ ComputeMaskedBits(I->getOperand(0), KnownZero,KnownOne, TD, Depth+1);
+ assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
KnownZero = APIntOps::lshr(KnownZero, ShiftAmt);
KnownOne = APIntOps::lshr(KnownOne, ShiftAmt);
// high bits known zero.
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
// Compute the new bits that are at the top now.
uint64_t ShiftAmt = SA->getLimitedValue(BitWidth-1);
-
+
// Signed shift right.
- APInt Mask2(Mask.shl(ShiftAmt));
- ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero, KnownOne, TD,
- Depth+1);
- assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
+ ComputeMaskedBits(I->getOperand(0), KnownZero, KnownOne, TD, Depth+1);
+ assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
KnownZero = APIntOps::lshr(KnownZero, ShiftAmt);
KnownOne = APIntOps::lshr(KnownOne, ShiftAmt);
-
+
APInt HighBits(APInt::getHighBitsSet(BitWidth, ShiftAmt));
if (KnownZero[BitWidth-ShiftAmt-1]) // New bits are known zero.
KnownZero |= HighBits;
}
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, KnownZero2, KnownOne2,
- TD, 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 ((KnownZero2 & MaskV) == MaskV) {
- unsigned NLZ2 = CLHS->getValue().countLeadingZeros();
- // Top bits known zero.
- KnownZero = APInt::getHighBitsSet(BitWidth, NLZ2) & Mask;
- }
- }
- }
+ bool NSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap();
+ ComputeMaskedBitsAddSub(false, I->getOperand(0), I->getOperand(1), NSW,
+ KnownZero, KnownOne, KnownZero2, KnownOne2, TD,
+ Depth);
+ break;
}
- // fall through
case Instruction::Add: {
- // If one of the operands has trailing zeros, then the bits that the
- // other operand has in those bit positions will be preserved in the
- // result. For an add, this works with either operand. For a subtract,
- // this only works if the known zeros are in the right operand.
- APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0);
- APInt Mask2 = APInt::getLowBitsSet(BitWidth,
- BitWidth - Mask.countLeadingZeros());
- ComputeMaskedBits(I->getOperand(0), Mask2, LHSKnownZero, LHSKnownOne, TD,
- Depth+1);
- assert((LHSKnownZero & LHSKnownOne) == 0 &&
- "Bits known to be one AND zero?");
- unsigned LHSKnownZeroOut = LHSKnownZero.countTrailingOnes();
-
- ComputeMaskedBits(I->getOperand(1), Mask2, KnownZero2, KnownOne2, TD,
- Depth+1);
- assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
- unsigned RHSKnownZeroOut = KnownZero2.countTrailingOnes();
-
- // Determine which operand has more trailing zeros, and use that
- // many bits from the other operand.
- if (LHSKnownZeroOut > RHSKnownZeroOut) {
- if (I->getOpcode() == Instruction::Add) {
- APInt Mask = APInt::getLowBitsSet(BitWidth, LHSKnownZeroOut);
- KnownZero |= KnownZero2 & Mask;
- KnownOne |= KnownOne2 & Mask;
- } else {
- // If the known zeros are in the left operand for a subtract,
- // fall back to the minimum known zeros in both operands.
- KnownZero |= APInt::getLowBitsSet(BitWidth,
- std::min(LHSKnownZeroOut,
- RHSKnownZeroOut));
- }
- } else if (RHSKnownZeroOut >= LHSKnownZeroOut) {
- APInt Mask = APInt::getLowBitsSet(BitWidth, RHSKnownZeroOut);
- KnownZero |= LHSKnownZero & Mask;
- KnownOne |= LHSKnownOne & Mask;
- }
-
- // Are we still trying to solve for the sign bit?
- if (Mask.isNegative() && !KnownZero.isNegative() && !KnownOne.isNegative()){
- OverflowingBinaryOperator *OBO = cast<OverflowingBinaryOperator>(I);
- if (OBO->hasNoSignedWrap()) {
- if (I->getOpcode() == Instruction::Add) {
- // Adding two positive numbers can't wrap into negative
- if (LHSKnownZero.isNegative() && KnownZero2.isNegative())
- KnownZero |= APInt::getSignBit(BitWidth);
- // and adding two negative numbers can't wrap into positive.
- else if (LHSKnownOne.isNegative() && KnownOne2.isNegative())
- KnownOne |= APInt::getSignBit(BitWidth);
- } else {
- // Subtracting a negative number from a positive one can't wrap
- if (LHSKnownZero.isNegative() && KnownOne2.isNegative())
- KnownZero |= APInt::getSignBit(BitWidth);
- // neither can subtracting a positive number from a negative one.
- else if (LHSKnownOne.isNegative() && KnownZero2.isNegative())
- KnownOne |= APInt::getSignBit(BitWidth);
- }
- }
- }
-
- return;
+ bool NSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap();
+ ComputeMaskedBitsAddSub(true, I->getOperand(0), I->getOperand(1), NSW,
+ KnownZero, KnownOne, KnownZero2, KnownOne2, TD,
+ Depth);
+ break;
}
case Instruction::SRem:
if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) {
APInt RA = Rem->getValue().abs();
if (RA.isPowerOf2()) {
APInt LowBits = RA - 1;
- APInt Mask2 = LowBits | APInt::getSignBit(BitWidth);
- ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD,
- Depth+1);
+ ComputeMaskedBits(I->getOperand(0), KnownZero2, KnownOne2, TD, Depth+1);
// The low bits of the first operand are unchanged by the srem.
KnownZero = KnownZero2 & LowBits;
if (KnownOne2[BitWidth-1] && ((KnownOne2 & LowBits) != 0))
KnownOne |= ~LowBits;
- KnownZero &= Mask;
- KnownOne &= Mask;
-
- assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
+ assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
}
}
// The sign bit is the LHS's sign bit, except when the result of the
// remainder is zero.
- if (Mask.isNegative() && KnownZero.isNonNegative()) {
- APInt Mask2 = APInt::getSignBit(BitWidth);
+ if (KnownZero.isNonNegative()) {
APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0);
- ComputeMaskedBits(I->getOperand(0), Mask2, LHSKnownZero, LHSKnownOne, TD,
+ ComputeMaskedBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, TD,
Depth+1);
// If it's known zero, our sign bit is also zero.
if (LHSKnownZero.isNegative())
- KnownZero |= LHSKnownZero;
+ KnownZero.setBit(BitWidth - 1);
}
break;
APInt RA = Rem->getValue();
if (RA.isPowerOf2()) {
APInt LowBits = (RA - 1);
- APInt Mask2 = LowBits & Mask;
- KnownZero |= ~LowBits & Mask;
- ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero, KnownOne, TD,
+ ComputeMaskedBits(I->getOperand(0), KnownZero, KnownOne, TD,
Depth+1);
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
+ KnownZero |= ~LowBits;
+ KnownOne &= LowBits;
break;
}
}
// Since the result is less than or equal to either operand, any leading
// zero bits in either operand must also exist in the result.
- APInt AllOnes = APInt::getAllOnesValue(BitWidth);
- ComputeMaskedBits(I->getOperand(0), AllOnes, KnownZero, KnownOne,
- TD, Depth+1);
- ComputeMaskedBits(I->getOperand(1), AllOnes, KnownZero2, KnownOne2,
- TD, Depth+1);
+ ComputeMaskedBits(I->getOperand(0), KnownZero, KnownOne, TD, Depth+1);
+ ComputeMaskedBits(I->getOperand(1), KnownZero2, KnownOne2, TD, Depth+1);
unsigned Leaders = std::max(KnownZero.countLeadingOnes(),
KnownZero2.countLeadingOnes());
KnownOne.clearAllBits();
- KnownZero = APInt::getHighBitsSet(BitWidth, Leaders) & Mask;
+ KnownZero = APInt::getHighBitsSet(BitWidth, Leaders);
break;
}
unsigned Align = AI->getAlignment();
if (Align == 0 && TD)
Align = TD->getABITypeAlignment(AI->getType()->getElementType());
-
+
if (Align > 0)
- KnownZero = Mask & APInt::getLowBitsSet(BitWidth,
- CountTrailingZeros_32(Align));
+ KnownZero = APInt::getLowBitsSet(BitWidth, countTrailingZeros(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, TD, Depth+1);
+ ComputeMaskedBits(I->getOperand(0), LocalKnownZero, LocalKnownOne, TD,
+ Depth+1);
unsigned TrailZ = LocalKnownZero.countTrailingOnes();
gep_type_iterator GTI = gep_type_begin(I);
Value *Index = I->getOperand(i);
if (StructType *STy = dyn_cast<StructType>(*GTI)) {
// Handle struct member offset arithmetic.
- if (!TD) return;
- const StructLayout *SL = TD->getStructLayout(STy);
+ if (!TD)
+ return;
+
+ // Handle case when index is vector zeroinitializer
+ Constant *CIndex = cast<Constant>(Index);
+ if (CIndex->isZeroValue())
+ continue;
+
+ if (CIndex->getType()->isVectorTy())
+ Index = CIndex->getSplatValue();
+
unsigned Idx = cast<ConstantInt>(Index)->getZExtValue();
+ const StructLayout *SL = TD->getStructLayout(STy);
uint64_t Offset = SL->getElementOffset(Idx);
- TrailZ = std::min(TrailZ,
- CountTrailingZeros_64(Offset));
+ TrailZ = std::min<unsigned>(TrailZ,
+ countTrailingZeros(Offset));
} else {
// Handle array index arithmetic.
Type *IndexedTy = GTI.getIndexedType();
if (!IndexedTy->isSized()) return;
unsigned GEPOpiBits = Index->getType()->getScalarSizeInBits();
uint64_t TypeSize = TD ? TD->getTypeAllocSize(IndexedTy) : 1;
- LocalMask = APInt::getAllOnesValue(GEPOpiBits);
LocalKnownZero = LocalKnownOne = APInt(GEPOpiBits, 0);
- ComputeMaskedBits(Index, LocalMask,
- LocalKnownZero, LocalKnownOne, TD, Depth+1);
+ ComputeMaskedBits(Index, LocalKnownZero, LocalKnownOne, TD, Depth+1);
TrailZ = std::min(TrailZ,
- unsigned(CountTrailingZeros_64(TypeSize) +
+ unsigned(countTrailingZeros(TypeSize) +
LocalKnownZero.countTrailingOnes()));
}
}
-
- KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ) & Mask;
+
+ KnownZero = APInt::getLowBitsSet(BitWidth, TrailZ);
break;
}
case Instruction::PHI: {
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, TD, Depth+1);
- Mask2 = APInt::getLowBitsSet(BitWidth,
- KnownZero2.countTrailingOnes());
+ ComputeMaskedBits(R, KnownZero2, KnownOne2, TD, Depth+1);
// We need to take the minimum number of known bits
APInt KnownZero3(KnownZero), KnownOne3(KnownOne);
- ComputeMaskedBits(L, Mask2, KnownZero3, KnownOne3, TD, Depth+1);
+ ComputeMaskedBits(L, KnownZero3, KnownOne3, TD, Depth+1);
- KnownZero = Mask &
- APInt::getLowBitsSet(BitWidth,
+ KnownZero = APInt::getLowBitsSet(BitWidth,
std::min(KnownZero2.countTrailingOnes(),
KnownZero3.countTrailingOnes()));
break;
// taking conservative care to avoid excessive recursion.
if (Depth < MaxDepth - 1 && !KnownZero && !KnownOne) {
// Skip if every incoming value references to ourself.
- if (P->hasConstantValue() == P)
+ if (dyn_cast_or_null<UndefValue>(P->hasConstantValue()))
break;
KnownZero = APInt::getAllOnesValue(BitWidth);
KnownOne2 = APInt(BitWidth, 0);
// Recurse, but cap the recursion to one level, because we don't
// want to waste time spinning around in loops.
- ComputeMaskedBits(P->getIncomingValue(i), KnownZero | KnownOne,
- KnownZero2, KnownOne2, TD, MaxDepth-1);
+ ComputeMaskedBits(P->getIncomingValue(i), KnownZero2, KnownOne2, TD,
+ MaxDepth-1);
KnownZero &= KnownZero2;
KnownOne &= KnownOne2;
// If all bits have been ruled out, there's no need to check
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
switch (II->getIntrinsicID()) {
default: break;
- case Intrinsic::ctpop:
case Intrinsic::ctlz:
case Intrinsic::cttz: {
+ unsigned LowBits = Log2_32(BitWidth)+1;
+ // If this call is undefined for 0, the result will be less than 2^n.
+ if (II->getArgOperand(1) == ConstantInt::getTrue(II->getContext()))
+ LowBits -= 1;
+ KnownZero = APInt::getHighBitsSet(BitWidth, BitWidth - LowBits);
+ break;
+ }
+ case Intrinsic::ctpop: {
unsigned LowBits = Log2_32(BitWidth)+1;
KnownZero = APInt::getHighBitsSet(BitWidth, BitWidth - LowBits);
break;
}
- case Intrinsic::x86_sse42_crc32_64_8:
case Intrinsic::x86_sse42_crc32_64_64:
KnownZero = APInt::getHighBitsSet(64, 32);
break;
}
}
break;
+ case Instruction::ExtractValue:
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I->getOperand(0))) {
+ ExtractValueInst *EVI = cast<ExtractValueInst>(I);
+ if (EVI->getNumIndices() != 1) break;
+ if (EVI->getIndices()[0] == 0) {
+ switch (II->getIntrinsicID()) {
+ default: break;
+ case Intrinsic::uadd_with_overflow:
+ case Intrinsic::sadd_with_overflow:
+ ComputeMaskedBitsAddSub(true, II->getArgOperand(0),
+ II->getArgOperand(1), false, KnownZero,
+ KnownOne, KnownZero2, KnownOne2, TD, Depth);
+ break;
+ case Intrinsic::usub_with_overflow:
+ case Intrinsic::ssub_with_overflow:
+ ComputeMaskedBitsAddSub(false, II->getArgOperand(0),
+ II->getArgOperand(1), false, KnownZero,
+ KnownOne, KnownZero2, KnownOne2, TD, Depth);
+ break;
+ case Intrinsic::umul_with_overflow:
+ case Intrinsic::smul_with_overflow:
+ ComputeMaskedBitsMul(II->getArgOperand(0), II->getArgOperand(1),
+ false, KnownZero, KnownOne,
+ KnownZero2, KnownOne2, TD, Depth);
+ break;
+ }
+ }
+ }
}
}
/// ComputeSignBit - Determine whether the sign bit is known to be zero or
/// one. Convenience wrapper around ComputeMaskedBits.
void llvm::ComputeSignBit(Value *V, bool &KnownZero, bool &KnownOne,
- const TargetData *TD, unsigned Depth) {
+ const DataLayout *TD, unsigned Depth) {
unsigned BitWidth = getBitWidth(V->getType(), TD);
if (!BitWidth) {
KnownZero = false;
}
APInt ZeroBits(BitWidth, 0);
APInt OneBits(BitWidth, 0);
- ComputeMaskedBits(V, APInt::getSignBit(BitWidth), ZeroBits, OneBits, TD,
- Depth);
+ ComputeMaskedBits(V, ZeroBits, OneBits, TD, Depth);
KnownOne = OneBits[BitWidth - 1];
KnownZero = ZeroBits[BitWidth - 1];
}
-/// isPowerOfTwo - Return true if the given value is known to have exactly one
+/// isKnownToBeAPowerOfTwo - Return true if the given value is known to have exactly one
/// bit set when defined. For vectors return true if every element is known to
/// be a power of two when defined. Supports values with integer or pointer
/// types and vectors of integers.
-bool llvm::isPowerOfTwo(Value *V, const TargetData *TD, unsigned Depth) {
- if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
- return CI->getValue().isPowerOf2();
- // TODO: Handle vector constants.
+bool llvm::isKnownToBeAPowerOfTwo(Value *V, bool OrZero, unsigned Depth) {
+ if (Constant *C = dyn_cast<Constant>(V)) {
+ if (C->isNullValue())
+ return OrZero;
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(C))
+ return CI->getValue().isPowerOf2();
+ // TODO: Handle vector constants.
+ }
// 1 << X is clearly a power of two if the one is not shifted off the end. If
// it is shifted off the end then the result is undefined.
if (Depth++ == MaxDepth)
return false;
+ Value *X = 0, *Y = 0;
+ // A shift of a power of two is a power of two or zero.
+ if (OrZero && (match(V, m_Shl(m_Value(X), m_Value())) ||
+ match(V, m_Shr(m_Value(X), m_Value()))))
+ return isKnownToBeAPowerOfTwo(X, /*OrZero*/true, Depth);
+
if (ZExtInst *ZI = dyn_cast<ZExtInst>(V))
- return isPowerOfTwo(ZI->getOperand(0), TD, Depth);
+ return isKnownToBeAPowerOfTwo(ZI->getOperand(0), OrZero, Depth);
if (SelectInst *SI = dyn_cast<SelectInst>(V))
- return isPowerOfTwo(SI->getTrueValue(), TD, Depth) &&
- isPowerOfTwo(SI->getFalseValue(), TD, Depth);
+ return isKnownToBeAPowerOfTwo(SI->getTrueValue(), OrZero, Depth) &&
+ isKnownToBeAPowerOfTwo(SI->getFalseValue(), OrZero, Depth);
+
+ if (OrZero && match(V, m_And(m_Value(X), m_Value(Y)))) {
+ // A power of two and'd with anything is a power of two or zero.
+ if (isKnownToBeAPowerOfTwo(X, /*OrZero*/true, Depth) ||
+ isKnownToBeAPowerOfTwo(Y, /*OrZero*/true, Depth))
+ return true;
+ // X & (-X) is always a power of two or zero.
+ if (match(X, m_Neg(m_Specific(Y))) || match(Y, m_Neg(m_Specific(X))))
+ return true;
+ return false;
+ }
+
+ // Adding a power-of-two or zero to the same power-of-two or zero yields
+ // either the original power-of-two, a larger power-of-two or zero.
+ if (match(V, m_Add(m_Value(X), m_Value(Y)))) {
+ OverflowingBinaryOperator *VOBO = cast<OverflowingBinaryOperator>(V);
+ if (OrZero || VOBO->hasNoUnsignedWrap() || VOBO->hasNoSignedWrap()) {
+ if (match(X, m_And(m_Specific(Y), m_Value())) ||
+ match(X, m_And(m_Value(), m_Specific(Y))))
+ if (isKnownToBeAPowerOfTwo(Y, OrZero, Depth))
+ return true;
+ if (match(Y, m_And(m_Specific(X), m_Value())) ||
+ match(Y, m_And(m_Value(), m_Specific(X))))
+ if (isKnownToBeAPowerOfTwo(X, OrZero, Depth))
+ return true;
+
+ unsigned BitWidth = V->getType()->getScalarSizeInBits();
+ APInt LHSZeroBits(BitWidth, 0), LHSOneBits(BitWidth, 0);
+ ComputeMaskedBits(X, LHSZeroBits, LHSOneBits, 0, Depth);
+
+ APInt RHSZeroBits(BitWidth, 0), RHSOneBits(BitWidth, 0);
+ ComputeMaskedBits(Y, RHSZeroBits, RHSOneBits, 0, Depth);
+ // If i8 V is a power of two or zero:
+ // ZeroBits: 1 1 1 0 1 1 1 1
+ // ~ZeroBits: 0 0 0 1 0 0 0 0
+ if ((~(LHSZeroBits & RHSZeroBits)).isPowerOf2())
+ // If OrZero isn't set, we cannot give back a zero result.
+ // Make sure either the LHS or RHS has a bit set.
+ if (OrZero || RHSOneBits.getBoolValue() || LHSOneBits.getBoolValue())
+ return true;
+ }
+ }
// An exact divide or right shift can only shift off zero bits, so the result
// is a power of two only if the first operand is a power of two and not
// copying a sign bit (sdiv int_min, 2).
- if (match(V, m_LShr(m_Value(), m_Value())) ||
- match(V, m_UDiv(m_Value(), m_Value()))) {
- PossiblyExactOperator *PEO = cast<PossiblyExactOperator>(V);
- if (PEO->isExact())
- return isPowerOfTwo(PEO->getOperand(0), TD, Depth);
+ if (match(V, m_Exact(m_LShr(m_Value(), m_Value()))) ||
+ match(V, m_Exact(m_UDiv(m_Value(), m_Value())))) {
+ return isKnownToBeAPowerOfTwo(cast<Operator>(V)->getOperand(0), OrZero, Depth);
+ }
+
+ return false;
+}
+
+/// \brief Test whether a GEP's result is known to be non-null.
+///
+/// Uses properties inherent in a GEP to try to determine whether it is known
+/// to be non-null.
+///
+/// Currently this routine does not support vector GEPs.
+static bool isGEPKnownNonNull(GEPOperator *GEP, const DataLayout *DL,
+ unsigned Depth) {
+ if (!GEP->isInBounds() || GEP->getPointerAddressSpace() != 0)
+ return false;
+
+ // FIXME: Support vector-GEPs.
+ assert(GEP->getType()->isPointerTy() && "We only support plain pointer GEP");
+
+ // If the base pointer is non-null, we cannot walk to a null address with an
+ // inbounds GEP in address space zero.
+ if (isKnownNonZero(GEP->getPointerOperand(), DL, Depth))
+ return true;
+
+ // Past this, if we don't have DataLayout, we can't do much.
+ if (!DL)
+ return false;
+
+ // Walk the GEP operands and see if any operand introduces a non-zero offset.
+ // If so, then the GEP cannot produce a null pointer, as doing so would
+ // inherently violate the inbounds contract within address space zero.
+ for (gep_type_iterator GTI = gep_type_begin(GEP), GTE = gep_type_end(GEP);
+ GTI != GTE; ++GTI) {
+ // Struct types are easy -- they must always be indexed by a constant.
+ if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+ ConstantInt *OpC = cast<ConstantInt>(GTI.getOperand());
+ unsigned ElementIdx = OpC->getZExtValue();
+ const StructLayout *SL = DL->getStructLayout(STy);
+ uint64_t ElementOffset = SL->getElementOffset(ElementIdx);
+ if (ElementOffset > 0)
+ return true;
+ continue;
+ }
+
+ // If we have a zero-sized type, the index doesn't matter. Keep looping.
+ if (DL->getTypeAllocSize(GTI.getIndexedType()) == 0)
+ continue;
+
+ // Fast path the constant operand case both for efficiency and so we don't
+ // increment Depth when just zipping down an all-constant GEP.
+ if (ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand())) {
+ if (!OpC->isZero())
+ return true;
+ continue;
+ }
+
+ // We post-increment Depth here because while isKnownNonZero increments it
+ // as well, when we pop back up that increment won't persist. We don't want
+ // to recurse 10k times just because we have 10k GEP operands. We don't
+ // bail completely out because we want to handle constant GEPs regardless
+ // of depth.
+ if (Depth++ >= MaxDepth)
+ continue;
+
+ if (isKnownNonZero(GTI.getOperand(), DL, Depth))
+ return true;
}
return false;
/// when defined. For vectors return true if every element is known to be
/// non-zero when defined. Supports values with integer or pointer type and
/// vectors of integers.
-bool llvm::isKnownNonZero(Value *V, const TargetData *TD, unsigned Depth) {
+bool llvm::isKnownNonZero(Value *V, const DataLayout *TD, unsigned Depth) {
if (Constant *C = dyn_cast<Constant>(V)) {
if (C->isNullValue())
return false;
}
// The remaining tests are all recursive, so bail out if we hit the limit.
- if (Depth++ == MaxDepth)
+ if (Depth++ >= MaxDepth)
return false;
- unsigned BitWidth = getBitWidth(V->getType(), TD);
+ // Check for pointer simplifications.
+ if (V->getType()->isPointerTy()) {
+ if (isKnownNonNull(V))
+ return true;
+ if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
+ if (isGEPKnownNonNull(GEP, TD, Depth))
+ return true;
+ }
+
+ unsigned BitWidth = getBitWidth(V->getType()->getScalarType(), TD);
// X | Y != 0 if X != 0 or Y != 0.
Value *X = 0, *Y = 0;
// if the lowest bit is shifted off the end.
if (BitWidth && match(V, m_Shl(m_Value(X), m_Value(Y)))) {
// shl nuw can't remove any non-zero bits.
- BinaryOperator *BO = cast<BinaryOperator>(V);
+ OverflowingBinaryOperator *BO = cast<OverflowingBinaryOperator>(V);
if (BO->hasNoUnsignedWrap())
return isKnownNonZero(X, TD, Depth);
APInt KnownZero(BitWidth, 0);
APInt KnownOne(BitWidth, 0);
- ComputeMaskedBits(X, APInt(BitWidth, 1), KnownZero, KnownOne, TD, Depth);
+ ComputeMaskedBits(X, KnownZero, KnownOne, TD, Depth);
if (KnownOne[0])
return true;
}
// defined if the sign bit is shifted off the end.
else if (match(V, m_Shr(m_Value(X), m_Value(Y)))) {
// shr exact can only shift out zero bits.
- BinaryOperator *BO = cast<BinaryOperator>(V);
+ PossiblyExactOperator *BO = cast<PossiblyExactOperator>(V);
if (BO->isExact())
return isKnownNonZero(X, TD, Depth);
return true;
}
// div exact can only produce a zero if the dividend is zero.
- else if (match(V, m_IDiv(m_Value(X), m_Value()))) {
- BinaryOperator *BO = cast<BinaryOperator>(V);
- if (BO->isExact())
- return isKnownNonZero(X, TD, Depth);
+ else if (match(V, m_Exact(m_IDiv(m_Value(X), m_Value())))) {
+ return isKnownNonZero(X, TD, Depth);
}
// X + Y.
else if (match(V, m_Add(m_Value(X), m_Value(Y)))) {
APInt Mask = APInt::getSignedMaxValue(BitWidth);
// The sign bit of X is set. If some other bit is set then X is not equal
// to INT_MIN.
- ComputeMaskedBits(X, Mask, KnownZero, KnownOne, TD, Depth);
+ ComputeMaskedBits(X, KnownZero, KnownOne, TD, Depth);
if ((KnownOne & Mask) != 0)
return true;
// The sign bit of Y is set. If some other bit is set then Y is not equal
// to INT_MIN.
- ComputeMaskedBits(Y, Mask, KnownZero, KnownOne, TD, Depth);
+ ComputeMaskedBits(Y, KnownZero, KnownOne, TD, Depth);
if ((KnownOne & Mask) != 0)
return true;
}
// The sum of a non-negative number and a power of two is not zero.
- if (XKnownNonNegative && isPowerOfTwo(Y, TD, Depth))
+ if (XKnownNonNegative && isKnownToBeAPowerOfTwo(Y, /*OrZero*/false, Depth))
+ return true;
+ if (YKnownNonNegative && isKnownToBeAPowerOfTwo(X, /*OrZero*/false, Depth))
return true;
- if (YKnownNonNegative && isPowerOfTwo(X, TD, Depth))
+ }
+ // X * Y.
+ else if (match(V, m_Mul(m_Value(X), m_Value(Y)))) {
+ OverflowingBinaryOperator *BO = cast<OverflowingBinaryOperator>(V);
+ // If X and Y are non-zero then so is X * Y as long as the multiplication
+ // does not overflow.
+ if ((BO->hasNoSignedWrap() || BO->hasNoUnsignedWrap()) &&
+ isKnownNonZero(X, TD, Depth) && isKnownNonZero(Y, TD, Depth))
return true;
}
// (C ? X : Y) != 0 if X != 0 and Y != 0.
if (!BitWidth) return false;
APInt KnownZero(BitWidth, 0);
APInt KnownOne(BitWidth, 0);
- ComputeMaskedBits(V, APInt::getAllOnesValue(BitWidth), KnownZero, KnownOne,
- TD, Depth);
+ ComputeMaskedBits(V, KnownZero, KnownOne, TD, Depth);
return KnownOne != 0;
}
/// same width as the vector element, and the bit is set only if it is true
/// for all of the elements in the vector.
bool llvm::MaskedValueIsZero(Value *V, const APInt &Mask,
- const TargetData *TD, unsigned Depth) {
+ const DataLayout *TD, unsigned Depth) {
APInt KnownZero(Mask.getBitWidth(), 0), KnownOne(Mask.getBitWidth(), 0);
- ComputeMaskedBits(V, Mask, KnownZero, KnownOne, TD, Depth);
- assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
+ ComputeMaskedBits(V, KnownZero, KnownOne, TD, Depth);
+ assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
return (KnownZero & Mask) == Mask;
}
///
/// 'Op' must have a scalar integer type.
///
-unsigned llvm::ComputeNumSignBits(Value *V, const TargetData *TD,
+unsigned llvm::ComputeNumSignBits(Value *V, const DataLayout *TD,
unsigned Depth) {
assert((TD || V->getType()->isIntOrIntVectorTy()) &&
- "ComputeNumSignBits requires a TargetData object to operate "
+ "ComputeNumSignBits requires a DataLayout object to operate "
"on non-integer values!");
Type *Ty = V->getType();
unsigned TyBits = TD ? TD->getTypeSizeInBits(V->getType()->getScalarType()) :
if (Depth == 6)
return 1; // Limit search depth.
-
+
Operator *U = dyn_cast<Operator>(V);
switch (Operator::getOpcode(V)) {
default: break;
case Instruction::SExt:
Tmp = TyBits - U->getOperand(0)->getType()->getScalarSizeInBits();
return ComputeNumSignBits(U->getOperand(0), TD, Depth+1) + Tmp;
-
- case Instruction::AShr:
+
+ case Instruction::AShr: {
Tmp = ComputeNumSignBits(U->getOperand(0), TD, Depth+1);
- // ashr X, C -> adds C sign bits.
- if (ConstantInt *C = dyn_cast<ConstantInt>(U->getOperand(1))) {
- Tmp += C->getZExtValue();
+ // ashr X, C -> adds C sign bits. Vectors too.
+ const APInt *ShAmt;
+ if (match(U->getOperand(1), m_APInt(ShAmt))) {
+ Tmp += ShAmt->getZExtValue();
if (Tmp > TyBits) Tmp = TyBits;
}
- // vector ashr X, <C, C, C, C> -> adds C sign bits
- if (ConstantVector *C = dyn_cast<ConstantVector>(U->getOperand(1))) {
- if (ConstantInt *CI = dyn_cast_or_null<ConstantInt>(C->getSplatValue())) {
- Tmp += CI->getZExtValue();
- if (Tmp > TyBits) Tmp = TyBits;
- }
- }
return Tmp;
- case Instruction::Shl:
- if (ConstantInt *C = dyn_cast<ConstantInt>(U->getOperand(1))) {
+ }
+ case Instruction::Shl: {
+ const APInt *ShAmt;
+ if (match(U->getOperand(1), m_APInt(ShAmt))) {
// shl destroys sign bits.
Tmp = ComputeNumSignBits(U->getOperand(0), TD, Depth+1);
- if (C->getZExtValue() >= TyBits || // Bad shift.
- C->getZExtValue() >= Tmp) break; // Shifted all sign bits out.
- return Tmp - C->getZExtValue();
+ Tmp2 = ShAmt->getZExtValue();
+ if (Tmp2 >= TyBits || // Bad shift.
+ Tmp2 >= Tmp) break; // Shifted all sign bits out.
+ return Tmp - Tmp2;
}
break;
+ }
case Instruction::And:
case Instruction::Or:
case Instruction::Xor: // NOT is handled here.
if (Tmp == 1) return 1; // Early out.
Tmp2 = ComputeNumSignBits(U->getOperand(2), TD, Depth+1);
return std::min(Tmp, Tmp2);
-
+
case Instruction::Add:
// Add can have at most one carry bit. Thus we know that the output
// is, at worst, one more bit than the inputs.
Tmp = ComputeNumSignBits(U->getOperand(0), TD, Depth+1);
if (Tmp == 1) return 1; // Early out.
-
+
// Special case decrementing a value (ADD X, -1):
if (ConstantInt *CRHS = dyn_cast<ConstantInt>(U->getOperand(1)))
if (CRHS->isAllOnesValue()) {
APInt KnownZero(TyBits, 0), KnownOne(TyBits, 0);
- APInt Mask = APInt::getAllOnesValue(TyBits);
- ComputeMaskedBits(U->getOperand(0), Mask, KnownZero, KnownOne, TD,
- Depth+1);
-
+ ComputeMaskedBits(U->getOperand(0), KnownZero, KnownOne, TD, Depth+1);
+
// If the input is known to be 0 or 1, the output is 0/-1, which is all
// sign bits set.
- if ((KnownZero | APInt(TyBits, 1)) == Mask)
+ if ((KnownZero | APInt(TyBits, 1)).isAllOnesValue())
return TyBits;
-
+
// If we are subtracting one from a positive number, there is no carry
// out of the result.
if (KnownZero.isNegative())
return Tmp;
}
-
+
Tmp2 = ComputeNumSignBits(U->getOperand(1), TD, Depth+1);
if (Tmp2 == 1) return 1;
return std::min(Tmp, Tmp2)-1;
-
+
case Instruction::Sub:
Tmp2 = ComputeNumSignBits(U->getOperand(1), TD, Depth+1);
if (Tmp2 == 1) return 1;
-
+
// Handle NEG.
if (ConstantInt *CLHS = dyn_cast<ConstantInt>(U->getOperand(0)))
if (CLHS->isNullValue()) {
APInt KnownZero(TyBits, 0), KnownOne(TyBits, 0);
- APInt Mask = APInt::getAllOnesValue(TyBits);
- ComputeMaskedBits(U->getOperand(1), Mask, KnownZero, KnownOne,
- TD, Depth+1);
+ ComputeMaskedBits(U->getOperand(1), KnownZero, KnownOne, TD, Depth+1);
// If the input is known to be 0 or 1, the output is 0/-1, which is all
// sign bits set.
- if ((KnownZero | APInt(TyBits, 1)) == Mask)
+ if ((KnownZero | APInt(TyBits, 1)).isAllOnesValue())
return TyBits;
-
+
// If the input is known to be positive (the sign bit is known clear),
// the output of the NEG has the same number of sign bits as the input.
if (KnownZero.isNegative())
return Tmp2;
-
+
// Otherwise, we treat this like a SUB.
}
-
+
// Sub can have at most one carry bit. Thus we know that the output
// is, at worst, one more bit than the inputs.
Tmp = ComputeNumSignBits(U->getOperand(0), TD, Depth+1);
if (Tmp == 1) return 1; // Early out.
return std::min(Tmp, Tmp2)-1;
-
+
case Instruction::PHI: {
PHINode *PN = cast<PHINode>(U);
// Don't analyze large in-degree PHIs.
if (PN->getNumIncomingValues() > 4) break;
-
+
// Take the minimum of all incoming values. This can't infinitely loop
// because of our depth threshold.
Tmp = ComputeNumSignBits(PN->getIncomingValue(0), TD, Depth+1);
// case for targets like X86.
break;
}
-
+
// Finally, if we can prove that the top bits of the result are 0's or 1's,
// use this information.
APInt KnownZero(TyBits, 0), KnownOne(TyBits, 0);
- APInt Mask = APInt::getAllOnesValue(TyBits);
- ComputeMaskedBits(V, Mask, KnownZero, KnownOne, TD, Depth);
-
+ APInt Mask;
+ ComputeMaskedBits(V, KnownZero, KnownOne, TD, Depth);
+
if (KnownZero.isNegative()) { // sign bit is 0
Mask = KnownZero;
} else if (KnownOne.isNegative()) { // sign bit is 1;
// Nothing known.
return FirstAnswer;
}
-
+
// Okay, we know that the sign bit in Mask is set. Use CLZ to determine
// the number of identical bits in the top of the input value.
Mask = ~Mask;
if (Base == 0)
return false;
-
+
if (Base == 1) {
Multiple = V;
return true;
if (CI && CI->getZExtValue() % Base == 0) {
Multiple = ConstantInt::get(T, CI->getZExtValue() / Base);
- return true;
+ return true;
}
-
+
if (Depth == MaxDepth) return false; // Limit search depth.
-
+
Operator *I = dyn_cast<Operator>(V);
if (!I) return false;
if (ComputeMultiple(Op0, Base, Mul0, LookThroughSExt, Depth+1)) {
if (Constant *Op1C = dyn_cast<Constant>(Op1))
if (Constant *MulC = dyn_cast<Constant>(Mul0)) {
- if (Op1C->getType()->getPrimitiveSizeInBits() <
+ if (Op1C->getType()->getPrimitiveSizeInBits() <
MulC->getType()->getPrimitiveSizeInBits())
Op1C = ConstantExpr::getZExt(Op1C, MulC->getType());
- if (Op1C->getType()->getPrimitiveSizeInBits() >
+ if (Op1C->getType()->getPrimitiveSizeInBits() >
MulC->getType()->getPrimitiveSizeInBits())
MulC = ConstantExpr::getZExt(MulC, Op1C->getType());
-
+
// V == Base * (Mul0 * Op1), so return (Mul0 * Op1)
Multiple = ConstantExpr::getMul(MulC, Op1C);
return true;
if (ComputeMultiple(Op1, Base, Mul1, LookThroughSExt, Depth+1)) {
if (Constant *Op0C = dyn_cast<Constant>(Op0))
if (Constant *MulC = dyn_cast<Constant>(Mul1)) {
- if (Op0C->getType()->getPrimitiveSizeInBits() <
+ if (Op0C->getType()->getPrimitiveSizeInBits() <
MulC->getType()->getPrimitiveSizeInBits())
Op0C = ConstantExpr::getZExt(Op0C, MulC->getType());
- if (Op0C->getType()->getPrimitiveSizeInBits() >
+ if (Op0C->getType()->getPrimitiveSizeInBits() >
MulC->getType()->getPrimitiveSizeInBits())
MulC = ConstantExpr::getZExt(MulC, Op0C->getType());
-
+
// V == Base * (Mul1 * Op0), so return (Mul1 * Op0)
Multiple = ConstantExpr::getMul(MulC, Op0C);
return true;
return false;
}
-/// CannotBeNegativeZero - Return true if we can prove that the specified FP
+/// CannotBeNegativeZero - Return true if we can prove that the specified FP
/// value is never equal to -0.0.
///
/// NOTE: this function will need to be revisited when we support non-default
bool llvm::CannotBeNegativeZero(const Value *V, unsigned Depth) {
if (const ConstantFP *CFP = dyn_cast<ConstantFP>(V))
return !CFP->getValueAPF().isNegZero();
-
+
if (Depth == 6)
return 1; // Limit search depth.
const Operator *I = dyn_cast<Operator>(V);
if (I == 0) return false;
-
+
+ // Check if the nsz fast-math flag is set
+ if (const FPMathOperator *FPO = dyn_cast<FPMathOperator>(I))
+ if (FPO->hasNoSignedZeros())
+ return true;
+
// (add x, 0.0) is guaranteed to return +0.0, not -0.0.
- if (I->getOpcode() == Instruction::FAdd &&
- isa<ConstantFP>(I->getOperand(1)) &&
- cast<ConstantFP>(I->getOperand(1))->isNullValue())
- return true;
-
+ if (I->getOpcode() == Instruction::FAdd)
+ if (ConstantFP *CFP = dyn_cast<ConstantFP>(I->getOperand(1)))
+ if (CFP->isNullValue())
+ return true;
+
// sitofp and uitofp turn into +0.0 for zero.
if (isa<SIToFPInst>(I) || isa<UIToFPInst>(I))
return true;
-
+
if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
// sqrt(-0.0) = -0.0, no other negative results are possible.
if (II->getIntrinsicID() == Intrinsic::sqrt)
return CannotBeNegativeZero(II->getArgOperand(0), Depth+1);
-
+
if (const CallInst *CI = dyn_cast<CallInst>(I))
if (const Function *F = CI->getCalledFunction()) {
if (F->isDeclaration()) {
return CannotBeNegativeZero(CI->getArgOperand(0), Depth+1);
}
}
-
+
return false;
}
if (Constant *C = dyn_cast<Constant>(V))
if (C->isNullValue())
return Constant::getNullValue(Type::getInt8Ty(V->getContext()));
-
+
// Constant float and double values can be handled as integer values if the
- // corresponding integer value is "byteable". An important case is 0.0.
+ // corresponding integer value is "byteable". An important case is 0.0.
if (ConstantFP *CFP = dyn_cast<ConstantFP>(V)) {
if (CFP->getType()->isFloatTy())
V = ConstantExpr::getBitCast(CFP, Type::getInt32Ty(V->getContext()));
V = ConstantExpr::getBitCast(CFP, Type::getInt64Ty(V->getContext()));
// Don't handle long double formats, which have strange constraints.
}
-
- // We can handle constant integers that are power of two in size and a
+
+ // We can handle constant integers that are power of two in size and a
// multiple of 8 bits.
if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
unsigned Width = CI->getBitWidth();
Val2 = Val.lshr(NextWidth);
Val2 = Val2.trunc(Val.getBitWidth()/2);
Val = Val.trunc(Val.getBitWidth()/2);
-
+
// If the top/bottom halves aren't the same, reject it.
if (Val != Val2)
return 0;
return ConstantInt::get(V->getContext(), Val);
}
}
-
- // A ConstantArray is splatable if all its members are equal and also
- // splatable.
- if (ConstantArray *CA = dyn_cast<ConstantArray>(V)) {
- if (CA->getNumOperands() == 0)
- return 0;
-
- Value *Val = isBytewiseValue(CA->getOperand(0));
+
+ // A ConstantDataArray/Vector is splatable if all its members are equal and
+ // also splatable.
+ if (ConstantDataSequential *CA = dyn_cast<ConstantDataSequential>(V)) {
+ Value *Elt = CA->getElementAsConstant(0);
+ Value *Val = isBytewiseValue(Elt);
if (!Val)
return 0;
-
- for (unsigned I = 1, E = CA->getNumOperands(); I != E; ++I)
- if (CA->getOperand(I-1) != CA->getOperand(I))
+
+ for (unsigned I = 1, E = CA->getNumElements(); I != E; ++I)
+ if (CA->getElementAsConstant(I) != Elt)
return 0;
-
+
return Val;
}
-
+
// Conceptually, we could handle things like:
// %a = zext i8 %X to i16
// %b = shl i16 %a, 8
// struct. To is the result struct built so far, new insertvalue instructions
// build on that.
static Value *BuildSubAggregate(Value *From, Value* To, Type *IndexedType,
- SmallVector<unsigned, 10> &Idxs,
+ SmallVectorImpl<unsigned> &Idxs,
unsigned IdxSkip,
Instruction *InsertBefore) {
- llvm::StructType *STy = llvm::dyn_cast<llvm::StructType>(IndexedType);
+ llvm::StructType *STy = dyn_cast<llvm::StructType>(IndexedType);
if (STy) {
// Save the original To argument so we can modify it
Value *OrigTo = To;
// the struct's elements had a value that was inserted directly. In the latter
// case, perhaps we can't determine each of the subelements individually, but
// we might be able to find the complete struct somewhere.
-
+
// Find the value that is at that particular spot
Value *V = FindInsertedValue(From, Idxs);
return NULL;
// Insert the value in the new (sub) aggregrate
- return llvm::InsertValueInst::Create(To, V,
- ArrayRef<unsigned>(Idxs).slice(IdxSkip),
+ return llvm::InsertValueInst::Create(To, V, makeArrayRef(Idxs).slice(IdxSkip),
"tmp", InsertBefore);
}
Value *llvm::FindInsertedValue(Value *V, ArrayRef<unsigned> idx_range,
Instruction *InsertBefore) {
// Nothing to index? Just return V then (this is useful at the end of our
- // recursion)
+ // recursion).
if (idx_range.empty())
return V;
- // We have indices, so V should have an indexable type
- assert((V->getType()->isStructTy() || V->getType()->isArrayTy())
- && "Not looking at a struct or array?");
- assert(ExtractValueInst::getIndexedType(V->getType(), idx_range)
- && "Invalid indices for type?");
- CompositeType *PTy = cast<CompositeType>(V->getType());
-
- if (isa<UndefValue>(V))
- return UndefValue::get(ExtractValueInst::getIndexedType(PTy,
- idx_range));
- else if (isa<ConstantAggregateZero>(V))
- return Constant::getNullValue(ExtractValueInst::getIndexedType(PTy,
- idx_range));
- else if (Constant *C = dyn_cast<Constant>(V)) {
- if (isa<ConstantArray>(C) || isa<ConstantStruct>(C))
- // Recursively process this constant
- return FindInsertedValue(C->getOperand(idx_range[0]), idx_range.slice(1),
- InsertBefore);
- } else if (InsertValueInst *I = dyn_cast<InsertValueInst>(V)) {
+ // We have indices, so V should have an indexable type.
+ assert((V->getType()->isStructTy() || V->getType()->isArrayTy()) &&
+ "Not looking at a struct or array?");
+ assert(ExtractValueInst::getIndexedType(V->getType(), idx_range) &&
+ "Invalid indices for type?");
+
+ if (Constant *C = dyn_cast<Constant>(V)) {
+ C = C->getAggregateElement(idx_range[0]);
+ if (C == 0) return 0;
+ return FindInsertedValue(C, idx_range.slice(1), InsertBefore);
+ }
+
+ if (InsertValueInst *I = dyn_cast<InsertValueInst>(V)) {
// Loop the indices for the insertvalue instruction in parallel with the
// requested indices
const unsigned *req_idx = idx_range.begin();
for (const unsigned *i = I->idx_begin(), *e = I->idx_end();
i != e; ++i, ++req_idx) {
if (req_idx == idx_range.end()) {
- if (InsertBefore)
- // The requested index identifies a part of a nested aggregate. Handle
- // this specially. For example,
- // %A = insertvalue { i32, {i32, i32 } } undef, i32 10, 1, 0
- // %B = insertvalue { i32, {i32, i32 } } %A, i32 11, 1, 1
- // %C = extractvalue {i32, { i32, i32 } } %B, 1
- // This can be changed into
- // %A = insertvalue {i32, i32 } undef, i32 10, 0
- // %C = insertvalue {i32, i32 } %A, i32 11, 1
- // which allows the unused 0,0 element from the nested struct to be
- // removed.
- return BuildSubAggregate(V,
- ArrayRef<unsigned>(idx_range.begin(),
- req_idx),
- InsertBefore);
- else
- // We can't handle this without inserting insertvalues
+ // We can't handle this without inserting insertvalues
+ if (!InsertBefore)
return 0;
+
+ // The requested index identifies a part of a nested aggregate. Handle
+ // this specially. For example,
+ // %A = insertvalue { i32, {i32, i32 } } undef, i32 10, 1, 0
+ // %B = insertvalue { i32, {i32, i32 } } %A, i32 11, 1, 1
+ // %C = extractvalue {i32, { i32, i32 } } %B, 1
+ // This can be changed into
+ // %A = insertvalue {i32, i32 } undef, i32 10, 0
+ // %C = insertvalue {i32, i32 } %A, i32 11, 1
+ // which allows the unused 0,0 element from the nested struct to be
+ // removed.
+ return BuildSubAggregate(V, makeArrayRef(idx_range.begin(), req_idx),
+ InsertBefore);
}
-
+
// This insert value inserts something else than what we are looking for.
// See if the (aggregrate) value inserted into has the value we are
// looking for, then.
// requested (though possibly only partially). Now we recursively look at
// the inserted value, passing any remaining indices.
return FindInsertedValue(I->getInsertedValueOperand(),
- ArrayRef<unsigned>(req_idx, idx_range.end()),
+ makeArrayRef(req_idx, idx_range.end()),
InsertBefore);
- } else if (ExtractValueInst *I = dyn_cast<ExtractValueInst>(V)) {
+ }
+
+ if (ExtractValueInst *I = dyn_cast<ExtractValueInst>(V)) {
// If we're extracting a value from an aggregrate that was extracted from
// something else, we can extract from that something else directly instead.
// However, we will need to chain I's indices with the requested indices.
-
- // Calculate the number of indices required
+
+ // Calculate the number of indices required
unsigned size = I->getNumIndices() + idx_range.size();
// Allocate some space to put the new indices in
SmallVector<unsigned, 5> Idxs;
Idxs.reserve(size);
// Add indices from the extract value instruction
Idxs.append(I->idx_begin(), I->idx_end());
-
+
// Add requested indices
Idxs.append(idx_range.begin(), idx_range.end());
- assert(Idxs.size() == size
+ assert(Idxs.size() == size
&& "Number of indices added not correct?");
-
+
return FindInsertedValue(I->getAggregateOperand(), Idxs, InsertBefore);
}
// Otherwise, we don't know (such as, extracting from a function return value
/// it can be expressed as a base pointer plus a constant offset. Return the
/// base and offset to the caller.
Value *llvm::GetPointerBaseWithConstantOffset(Value *Ptr, int64_t &Offset,
- const TargetData &TD) {
- Operator *PtrOp = dyn_cast<Operator>(Ptr);
- if (PtrOp == 0) return Ptr;
-
- // Just look through bitcasts.
- if (PtrOp->getOpcode() == Instruction::BitCast)
- return GetPointerBaseWithConstantOffset(PtrOp->getOperand(0), Offset, TD);
-
- // If this is a GEP with constant indices, we can look through it.
- GEPOperator *GEP = dyn_cast<GEPOperator>(PtrOp);
- if (GEP == 0 || !GEP->hasAllConstantIndices()) return Ptr;
-
- gep_type_iterator GTI = gep_type_begin(GEP);
- for (User::op_iterator I = GEP->idx_begin(), E = GEP->idx_end(); I != E;
- ++I, ++GTI) {
- ConstantInt *OpC = cast<ConstantInt>(*I);
- if (OpC->isZero()) continue;
-
- // Handle a struct and array indices which add their offset to the pointer.
- if (StructType *STy = dyn_cast<StructType>(*GTI)) {
- Offset += TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
+ const DataLayout *DL) {
+ // Without DataLayout, conservatively assume 64-bit offsets, which is
+ // the widest we support.
+ unsigned BitWidth = DL ? DL->getPointerTypeSizeInBits(Ptr->getType()) : 64;
+ APInt ByteOffset(BitWidth, 0);
+ while (1) {
+ if (Ptr->getType()->isVectorTy())
+ break;
+
+ if (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) {
+ if (DL) {
+ APInt GEPOffset(BitWidth, 0);
+ if (!GEP->accumulateConstantOffset(*DL, GEPOffset))
+ break;
+
+ ByteOffset += GEPOffset;
+ }
+
+ Ptr = GEP->getPointerOperand();
+ } else if (Operator::getOpcode(Ptr) == Instruction::BitCast) {
+ Ptr = cast<Operator>(Ptr)->getOperand(0);
+ } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(Ptr)) {
+ if (GA->mayBeOverridden())
+ break;
+ Ptr = GA->getAliasee();
} else {
- uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType());
- Offset += OpC->getSExtValue()*Size;
+ break;
}
}
-
- // Re-sign extend from the pointer size if needed to get overflow edge cases
- // right.
- unsigned PtrSize = TD.getPointerSizeInBits();
- if (PtrSize < 64)
- Offset = (Offset << (64-PtrSize)) >> (64-PtrSize);
-
- return GetPointerBaseWithConstantOffset(GEP->getPointerOperand(), Offset, TD);
+ Offset = ByteOffset.getSExtValue();
+ return Ptr;
}
-/// GetConstantStringInfo - This function computes the length of a
+/// getConstantStringInfo - This function computes the length of a
/// null-terminated C string pointed to by V. If successful, it returns true
/// and returns the string in Str. If unsuccessful, it returns false.
-bool llvm::GetConstantStringInfo(const Value *V, std::string &Str,
- uint64_t Offset,
- bool StopAtNul) {
- // If V is NULL then return false;
- if (V == NULL) return false;
-
- // Look through bitcast instructions.
- if (const BitCastInst *BCI = dyn_cast<BitCastInst>(V))
- return GetConstantStringInfo(BCI->getOperand(0), Str, Offset, StopAtNul);
-
- // If the value is not a GEP instruction nor a constant expression with a
- // GEP instruction, then return false because ConstantArray can't occur
- // any other way
- const User *GEP = 0;
- if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(V)) {
- GEP = GEPI;
- } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
- if (CE->getOpcode() == Instruction::BitCast)
- return GetConstantStringInfo(CE->getOperand(0), Str, Offset, StopAtNul);
- if (CE->getOpcode() != Instruction::GetElementPtr)
- return false;
- GEP = CE;
- }
-
- if (GEP) {
+bool llvm::getConstantStringInfo(const Value *V, StringRef &Str,
+ uint64_t Offset, bool TrimAtNul) {
+ assert(V);
+
+ // Look through bitcast instructions and geps.
+ V = V->stripPointerCasts();
+
+ // If the value is a GEP instructionor constant expression, treat it as an
+ // offset.
+ if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
// Make sure the GEP has exactly three arguments.
if (GEP->getNumOperands() != 3)
return false;
-
+
// Make sure the index-ee is a pointer to array of i8.
PointerType *PT = cast<PointerType>(GEP->getOperand(0)->getType());
ArrayType *AT = dyn_cast<ArrayType>(PT->getElementType());
if (AT == 0 || !AT->getElementType()->isIntegerTy(8))
return false;
-
+
// Check to make sure that the first operand of the GEP is an integer and
// has value 0 so that we are sure we're indexing into the initializer.
const ConstantInt *FirstIdx = dyn_cast<ConstantInt>(GEP->getOperand(1));
if (FirstIdx == 0 || !FirstIdx->isZero())
return false;
-
+
// If the second index isn't a ConstantInt, then this is a variable index
// into the array. If this occurs, we can't say anything meaningful about
// the string.
StartIdx = CI->getZExtValue();
else
return false;
- return GetConstantStringInfo(GEP->getOperand(0), Str, StartIdx+Offset,
- StopAtNul);
+ return getConstantStringInfo(GEP->getOperand(0), Str, StartIdx+Offset);
}
-
+
// The GEP instruction, constant or instruction, must reference a global
// variable that is a constant and is initialized. The referenced constant
// initializer is the array that we'll use for optimization.
- const GlobalVariable* GV = dyn_cast<GlobalVariable>(V);
+ const GlobalVariable *GV = dyn_cast<GlobalVariable>(V);
if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer())
return false;
- const Constant *GlobalInit = GV->getInitializer();
-
- // Handle the ConstantAggregateZero case
- if (isa<ConstantAggregateZero>(GlobalInit)) {
+
+ // Handle the all-zeros case
+ if (GV->getInitializer()->isNullValue()) {
// This is a degenerate case. The initializer is constant zero so the
// length of the string must be zero.
- Str.clear();
+ Str = "";
return true;
}
-
+
// Must be a Constant Array
- const ConstantArray *Array = dyn_cast<ConstantArray>(GlobalInit);
- if (Array == 0 || !Array->getType()->getElementType()->isIntegerTy(8))
+ const ConstantDataArray *Array =
+ dyn_cast<ConstantDataArray>(GV->getInitializer());
+ if (Array == 0 || !Array->isString())
return false;
-
+
// Get the number of elements in the array
- uint64_t NumElts = Array->getType()->getNumElements();
-
+ uint64_t NumElts = Array->getType()->getArrayNumElements();
+
+ // Start out with the entire array in the StringRef.
+ Str = Array->getAsString();
+
if (Offset > NumElts)
return false;
-
- // Traverse the constant array from 'Offset' which is the place the GEP refers
- // to in the array.
- Str.reserve(NumElts-Offset);
- for (unsigned i = Offset; i != NumElts; ++i) {
- const Constant *Elt = Array->getOperand(i);
- const ConstantInt *CI = dyn_cast<ConstantInt>(Elt);
- if (!CI) // This array isn't suitable, non-int initializer.
- return false;
- if (StopAtNul && CI->isZero())
- return true; // we found end of string, success!
- Str += (char)CI->getZExtValue();
+
+ // Skip over 'offset' bytes.
+ Str = Str.substr(Offset);
+
+ if (TrimAtNul) {
+ // Trim off the \0 and anything after it. If the array is not nul
+ // terminated, we just return the whole end of string. The client may know
+ // some other way that the string is length-bound.
+ Str = Str.substr(0, Str.find('\0'));
}
-
- // The array isn't null terminated, but maybe this is a memcpy, not a strcpy.
return true;
}
/// the specified pointer, return 'len+1'. If we can't, return 0.
static uint64_t GetStringLengthH(Value *V, SmallPtrSet<PHINode*, 32> &PHIs) {
// Look through noop bitcast instructions.
- if (BitCastInst *BCI = dyn_cast<BitCastInst>(V))
- return GetStringLengthH(BCI->getOperand(0), PHIs);
+ V = V->stripPointerCasts();
// If this is a PHI node, there are two cases: either we have already seen it
// or we haven't.
return Len1;
}
- // If the value is not a GEP instruction nor a constant expression with a
- // GEP instruction, then return unknown.
- User *GEP = 0;
- if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(V)) {
- GEP = GEPI;
- } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
- if (CE->getOpcode() != Instruction::GetElementPtr)
- return 0;
- GEP = CE;
- } else {
- return 0;
- }
-
- // Make sure the GEP has exactly three arguments.
- if (GEP->getNumOperands() != 3)
- return 0;
-
- // Check to make sure that the first operand of the GEP is an integer and
- // has value 0 so that we are sure we're indexing into the initializer.
- if (ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(1))) {
- if (!Idx->isZero())
- return 0;
- } else
- return 0;
-
- // If the second index isn't a ConstantInt, then this is a variable index
- // into the array. If this occurs, we can't say anything meaningful about
- // the string.
- uint64_t StartIdx = 0;
- if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
- StartIdx = CI->getZExtValue();
- else
- return 0;
-
- // The GEP instruction, constant or instruction, must reference a global
- // variable that is a constant and is initialized. The referenced constant
- // initializer is the array that we'll use for optimization.
- GlobalVariable* GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
- if (!GV || !GV->isConstant() || !GV->hasInitializer() ||
- GV->mayBeOverridden())
+ // Otherwise, see if we can read the string.
+ StringRef StrData;
+ if (!getConstantStringInfo(V, StrData))
return 0;
- Constant *GlobalInit = GV->getInitializer();
-
- // Handle the ConstantAggregateZero case, which is a degenerate case. The
- // initializer is constant zero so the length of the string must be zero.
- if (isa<ConstantAggregateZero>(GlobalInit))
- return 1; // Len = 0 offset by 1.
-
- // Must be a Constant Array
- ConstantArray *Array = dyn_cast<ConstantArray>(GlobalInit);
- if (!Array || !Array->getType()->getElementType()->isIntegerTy(8))
- return false;
-
- // Get the number of elements in the array
- uint64_t NumElts = Array->getType()->getNumElements();
-
- // Traverse the constant array from StartIdx (derived above) which is
- // the place the GEP refers to in the array.
- for (unsigned i = StartIdx; i != NumElts; ++i) {
- Constant *Elt = Array->getOperand(i);
- ConstantInt *CI = dyn_cast<ConstantInt>(Elt);
- if (!CI) // This array isn't suitable, non-int initializer.
- return 0;
- if (CI->isZero())
- return i-StartIdx+1; // We found end of string, success!
- }
- return 0; // The array isn't null terminated, conservatively return 'unknown'.
+ return StrData.size()+1;
}
/// GetStringLength - If we can compute the length of the string pointed to by
}
Value *
-llvm::GetUnderlyingObject(Value *V, const TargetData *TD, unsigned MaxLookup) {
+llvm::GetUnderlyingObject(Value *V, const DataLayout *TD, unsigned MaxLookup) {
if (!V->getType()->isPointerTy())
return V;
for (unsigned Count = 0; MaxLookup == 0 || Count < MaxLookup; ++Count) {
return V;
}
+void
+llvm::GetUnderlyingObjects(Value *V,
+ SmallVectorImpl<Value *> &Objects,
+ const DataLayout *TD,
+ unsigned MaxLookup) {
+ SmallPtrSet<Value *, 4> Visited;
+ SmallVector<Value *, 4> Worklist;
+ Worklist.push_back(V);
+ do {
+ Value *P = Worklist.pop_back_val();
+ P = GetUnderlyingObject(P, TD, MaxLookup);
+
+ if (!Visited.insert(P))
+ continue;
+
+ if (SelectInst *SI = dyn_cast<SelectInst>(P)) {
+ Worklist.push_back(SI->getTrueValue());
+ Worklist.push_back(SI->getFalseValue());
+ continue;
+ }
+
+ if (PHINode *PN = dyn_cast<PHINode>(P)) {
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+ Worklist.push_back(PN->getIncomingValue(i));
+ continue;
+ }
+
+ Objects.push_back(P);
+ } while (!Worklist.empty());
+}
+
/// onlyUsedByLifetimeMarkers - Return true if the only users of this pointer
/// are lifetime markers.
///
bool llvm::onlyUsedByLifetimeMarkers(const Value *V) {
- for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
- UI != UE; ++UI) {
- const IntrinsicInst *II = dyn_cast<IntrinsicInst>(*UI);
+ for (const User *U : V->users()) {
+ const IntrinsicInst *II = dyn_cast<IntrinsicInst>(U);
if (!II) return false;
if (II->getIntrinsicID() != Intrinsic::lifetime_start &&
}
return true;
}
+
+bool llvm::isSafeToSpeculativelyExecute(const Value *V,
+ const DataLayout *TD) {
+ const Operator *Inst = dyn_cast<Operator>(V);
+ if (!Inst)
+ return false;
+
+ for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i)
+ if (Constant *C = dyn_cast<Constant>(Inst->getOperand(i)))
+ if (C->canTrap())
+ return false;
+
+ switch (Inst->getOpcode()) {
+ default:
+ return true;
+ case Instruction::UDiv:
+ case Instruction::URem:
+ // x / y is undefined if y == 0, but calcuations like x / 3 are safe.
+ return isKnownNonZero(Inst->getOperand(1), TD);
+ case Instruction::SDiv:
+ case Instruction::SRem: {
+ Value *Op = Inst->getOperand(1);
+ // x / y is undefined if y == 0
+ if (!isKnownNonZero(Op, TD))
+ return false;
+ // x / y might be undefined if y == -1
+ unsigned BitWidth = getBitWidth(Op->getType(), TD);
+ if (BitWidth == 0)
+ return false;
+ APInt KnownZero(BitWidth, 0);
+ APInt KnownOne(BitWidth, 0);
+ ComputeMaskedBits(Op, KnownZero, KnownOne, TD);
+ return !!KnownZero;
+ }
+ case Instruction::Load: {
+ const LoadInst *LI = cast<LoadInst>(Inst);
+ if (!LI->isUnordered() ||
+ // Speculative load may create a race that did not exist in the source.
+ LI->getParent()->getParent()->hasFnAttribute(Attribute::SanitizeThread))
+ return false;
+ return LI->getPointerOperand()->isDereferenceablePointer();
+ }
+ case Instruction::Call: {
+ if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
+ switch (II->getIntrinsicID()) {
+ // These synthetic intrinsics have no side-effects, and just mark
+ // information about their operands.
+ // FIXME: There are other no-op synthetic instructions that potentially
+ // should be considered at least *safe* to speculate...
+ case Intrinsic::dbg_declare:
+ case Intrinsic::dbg_value:
+ return true;
+
+ case Intrinsic::bswap:
+ case Intrinsic::ctlz:
+ case Intrinsic::ctpop:
+ case Intrinsic::cttz:
+ case Intrinsic::objectsize:
+ case Intrinsic::sadd_with_overflow:
+ case Intrinsic::smul_with_overflow:
+ case Intrinsic::ssub_with_overflow:
+ case Intrinsic::uadd_with_overflow:
+ case Intrinsic::umul_with_overflow:
+ case Intrinsic::usub_with_overflow:
+ return true;
+ // Sqrt should be OK, since the llvm sqrt intrinsic isn't defined to set
+ // errno like libm sqrt would.
+ case Intrinsic::sqrt:
+ case Intrinsic::fma:
+ case Intrinsic::fmuladd:
+ return true;
+ // TODO: some fp intrinsics are marked as having the same error handling
+ // as libm. They're safe to speculate when they won't error.
+ // TODO: are convert_{from,to}_fp16 safe?
+ // TODO: can we list target-specific intrinsics here?
+ default: break;
+ }
+ }
+ return false; // The called function could have undefined behavior or
+ // side-effects, even if marked readnone nounwind.
+ }
+ case Instruction::VAArg:
+ case Instruction::Alloca:
+ case Instruction::Invoke:
+ case Instruction::PHI:
+ case Instruction::Store:
+ case Instruction::Ret:
+ case Instruction::Br:
+ case Instruction::IndirectBr:
+ case Instruction::Switch:
+ case Instruction::Unreachable:
+ case Instruction::Fence:
+ case Instruction::LandingPad:
+ case Instruction::AtomicRMW:
+ case Instruction::AtomicCmpXchg:
+ case Instruction::Resume:
+ return false; // Misc instructions which have effects
+ }
+}
+
+/// isKnownNonNull - Return true if we know that the specified value is never
+/// null.
+bool llvm::isKnownNonNull(const Value *V, const TargetLibraryInfo *TLI) {
+ // Alloca never returns null, malloc might.
+ if (isa<AllocaInst>(V)) return true;
+
+ // A byval or inalloca argument is never null.
+ if (const Argument *A = dyn_cast<Argument>(V))
+ return A->hasByValOrInAllocaAttr();
+
+ // Global values are not null unless extern weak.
+ if (const GlobalValue *GV = dyn_cast<GlobalValue>(V))
+ return !GV->hasExternalWeakLinkage();
+
+ // operator new never returns null.
+ if (isOperatorNewLikeFn(V, TLI, /*LookThroughBitCast=*/true))
+ return true;
+
+ return false;
+}
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