#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/MemoryBuiltins.h"
+#include "llvm/IR/CallSite.h"
#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/PatternMatch.h"
+#include "llvm/Support/Debug.h"
#include "llvm/Support/MathExtras.h"
#include <cstring>
using namespace llvm;
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::computeKnownBits(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.
+ // If an initial sequence of bits in the result is not needed, the
+ // corresponding bits in the operands are not needed.
APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0);
llvm::computeKnownBits(Op0, LHSKnownZero, LHSKnownOne, TD, Depth+1);
- assert((LHSKnownZero & LHSKnownOne) == 0 &&
- "Bits known to be one AND zero?");
- unsigned LHSKnownZeroOut = LHSKnownZero.countTrailingOnes();
-
llvm::computeKnownBits(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;
+
+ // Carry in a 1 for a subtract, rather than a 0.
+ APInt CarryIn(BitWidth, 0);
+ if (!Add) {
+ // Sum = LHS + ~RHS + 1
+ std::swap(KnownZero2, KnownOne2);
+ CarryIn.setBit(0);
}
+ APInt PossibleSumZero = ~LHSKnownZero + ~KnownZero2 + CarryIn;
+ APInt PossibleSumOne = LHSKnownOne + KnownOne2 + CarryIn;
+
+ // Compute known bits of the carry.
+ APInt CarryKnownZero = ~(PossibleSumZero ^ LHSKnownZero ^ KnownZero2);
+ APInt CarryKnownOne = PossibleSumOne ^ LHSKnownOne ^ KnownOne2;
+
+ // Compute set of known bits (where all three relevant bits are known).
+ APInt LHSKnown = LHSKnownZero | LHSKnownOne;
+ APInt RHSKnown = KnownZero2 | KnownOne2;
+ APInt CarryKnown = CarryKnownZero | CarryKnownOne;
+ APInt Known = LHSKnown & RHSKnown & CarryKnown;
+
+ assert((PossibleSumZero & Known) == (PossibleSumOne & Known) &&
+ "known bits of sum differ");
+
+ // Compute known bits of the result.
+ KnownZero = ~PossibleSumOne & Known;
+ KnownOne = PossibleSumOne & Known;
+
// Are we still trying to solve for the sign bit?
- if (!KnownZero.isNegative() && !KnownOne.isNegative()) {
+ if (!Known.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);
- }
+ // Adding two non-negative numbers, or subtracting a negative number from
+ // a non-negative one, can't wrap into negative.
+ if (LHSKnownZero.isNegative() && KnownZero2.isNegative())
+ KnownZero |= APInt::getSignBit(BitWidth);
+ // Adding two negative numbers, or subtracting a non-negative number from
+ // a negative one, can't wrap into non-negative.
+ else if (LHSKnownOne.isNegative() && KnownOne2.isNegative())
+ KnownOne |= APInt::getSignBit(BitWidth);
}
}
}
unsigned BitWidth = KnownZero.getBitWidth();
computeKnownBits(Op1, KnownZero, KnownOne, TD, Depth+1);
computeKnownBits(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;
KnownOne.setBit(BitWidth - 1);
}
-void llvm::computeKnownBitsLoad(const MDNode &Ranges, APInt &KnownZero) {
+void llvm::computeKnownBitsFromRangeMetadata(const MDNode &Ranges,
+ APInt &KnownZero) {
unsigned BitWidth = KnownZero.getBitWidth();
unsigned NumRanges = Ranges.getNumOperands() / 2;
assert(NumRanges >= 1);
KnownZero = APInt::getHighBitsSet(BitWidth, MinLeadingZeros);
}
+
/// Determine which bits of V are known to be either zero or one and return
/// them in the KnownZero/KnownOne bit sets.
///
}
if (Argument *A = dyn_cast<Argument>(V)) {
- unsigned Align = 0;
+ unsigned Align = A->getType()->isPointerTy() ? A->getParamAlignment() : 0;
- if (A->hasByValOrInAllocaAttr()) {
- // Get alignment information off byval/inalloca arguments if specified in
- // the IR.
- Align = A->getParamAlignment();
- } else if (TD && A->hasStructRetAttr()) {
+ if (!Align && 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())
default: break;
case Instruction::Load:
if (MDNode *MD = cast<LoadInst>(I)->getMetadata(LLVMContext::MD_range))
- computeKnownBitsLoad(*MD, KnownZero);
- return;
+ computeKnownBitsFromRangeMetadata(*MD, KnownZero);
+ break;
case Instruction::And: {
// If either the LHS or the RHS are Zero, the result is zero.
computeKnownBits(I->getOperand(1), KnownZero, KnownOne, TD, Depth+1);
computeKnownBits(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.
KnownZero |= KnownZero2;
- return;
+ break;
}
case Instruction::Or: {
computeKnownBits(I->getOperand(1), KnownZero, KnownOne, TD, Depth+1);
computeKnownBits(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.
KnownOne |= KnownOne2;
- return;
+ break;
}
case Instruction::Xor: {
computeKnownBits(I->getOperand(1), KnownZero, KnownOne, TD, Depth+1);
computeKnownBits(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.
KnownOne = (KnownZero & KnownOne2) | (KnownOne & KnownZero2);
KnownZero = KnownZeroOut;
- return;
+ break;
}
case Instruction::Mul: {
bool NSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap();
LeadZ + BitWidth - RHSUnknownLeadingOnes - 1);
KnownZero = APInt::getHighBitsSet(BitWidth, LeadZ);
- return;
+ break;
}
case Instruction::Select:
computeKnownBits(I->getOperand(2), KnownZero, KnownOne, TD, Depth+1);
computeKnownBits(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?");
// Only known if known in both the LHS and RHS.
KnownOne &= KnownOne2;
KnownZero &= KnownZero2;
- return;
+ break;
case Instruction::FPTrunc:
case Instruction::FPExt:
case Instruction::FPToUI:
case Instruction::FPToSI:
case Instruction::SIToFP:
case Instruction::UIToFP:
- return; // Can't work with floating point.
+ break; // Can't work with floating point.
case Instruction::PtrToInt:
case Instruction::IntToPtr:
+ case Instruction::AddrSpaceCast: // Pointers could be different sizes.
// We can't handle these if we don't know the pointer size.
- if (!TD) return;
+ if (!TD) break;
// FALL THROUGH and handle them the same as zext/trunc.
case Instruction::ZExt:
case Instruction::Trunc: {
SrcBitWidth = TD->getTypeSizeInBits(SrcTy->getScalarType());
} else {
SrcBitWidth = SrcTy->getScalarSizeInBits();
- if (!SrcBitWidth) return;
+ if (!SrcBitWidth) break;
}
assert(SrcBitWidth && "SrcBitWidth can't be zero");
// Any top bits are known to be zero.
if (BitWidth > SrcBitWidth)
KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth);
- return;
+ break;
}
case Instruction::BitCast: {
Type *SrcTy = I->getOperand(0)->getType();
// (bitcast i64 %x to <2 x i32>)
!I->getType()->isVectorTy()) {
computeKnownBits(I->getOperand(0), KnownZero, KnownOne, TD, Depth+1);
- return;
+ break;
}
break;
}
KnownZero = KnownZero.trunc(SrcBitWidth);
KnownOne = KnownOne.trunc(SrcBitWidth);
computeKnownBits(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);
KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth);
else if (KnownOne[SrcBitWidth-1]) // Input sign bit known set
KnownOne |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth);
- return;
+ break;
}
case Instruction::Shl:
// (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);
computeKnownBits(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
- return;
+ break;
}
break;
case Instruction::LShr:
// Unsigned shift right.
computeKnownBits(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.
KnownZero |= APInt::getHighBitsSet(BitWidth, ShiftAmt);
- return;
+ break;
}
break;
case Instruction::AShr:
// Signed shift right.
computeKnownBits(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);
KnownZero |= HighBits;
else if (KnownOne[BitWidth-ShiftAmt-1]) // New bits are known one.
KnownOne |= HighBits;
- return;
+ break;
}
break;
case Instruction::Sub: {
APInt LowBits = (RA - 1);
computeKnownBits(I->getOperand(0), KnownZero, KnownOne, TD,
Depth+1);
- assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
KnownZero |= ~LowBits;
KnownOne &= LowBits;
break;
Value *Index = I->getOperand(i);
if (StructType *STy = dyn_cast<StructType>(*GTI)) {
// Handle struct member offset arithmetic.
- if (!TD)
- return;
+ if (!TD) {
+ TrailZ = 0;
+ break;
+ }
// Handle case when index is vector zeroinitializer
Constant *CIndex = cast<Constant>(Index);
} else {
// Handle array index arithmetic.
Type *IndexedTy = GTI.getIndexedType();
- if (!IndexedTy->isSized()) return;
+ if (!IndexedTy->isSized()) {
+ TrailZ = 0;
+ break;
+ }
unsigned GEPOpiBits = Index->getType()->getScalarSizeInBits();
uint64_t TypeSize = TD ? TD->getTypeAllocSize(IndexedTy) : 1;
LocalKnownZero = LocalKnownOne = APInt(GEPOpiBits, 0);
// Unreachable blocks may have zero-operand PHI nodes.
if (P->getNumIncomingValues() == 0)
- return;
+ break;
// Otherwise take the unions of the known bit sets of the operands,
// taking conservative care to avoid excessive recursion.
break;
}
case Instruction::Call:
+ case Instruction::Invoke:
+ if (MDNode *MD = cast<Instruction>(I)->getMetadata(LLVMContext::MD_range))
+ computeKnownBitsFromRangeMetadata(*MD, KnownZero);
+ // If a range metadata is attached to this IntrinsicInst, intersect the
+ // explicit range specified by the metadata and the implicit range of
+ // the intrinsic.
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
switch (II->getIntrinsicID()) {
default: break;
// 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);
+ KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - LowBits);
break;
}
case Intrinsic::ctpop: {
unsigned LowBits = Log2_32(BitWidth)+1;
- KnownZero = APInt::getHighBitsSet(BitWidth, BitWidth - LowBits);
+ KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - LowBits);
break;
}
case Intrinsic::x86_sse42_crc32_64_64:
- KnownZero = APInt::getHighBitsSet(64, 32);
+ KnownZero |= APInt::getHighBitsSet(64, 32);
break;
}
}
}
}
}
+
+ assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
}
/// ComputeSignBit - Determine whether the sign bit is known to be zero or
const DataLayout *TD, unsigned Depth) {
APInt KnownZero(Mask.getBitWidth(), 0), KnownOne(Mask.getBitWidth(), 0);
computeKnownBits(V, KnownZero, KnownOne, TD, Depth);
- assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
return (KnownZero & Mask) == Mask;
}
}
Ptr = GEP->getPointerOperand();
- } else if (Operator::getOpcode(Ptr) == Instruction::BitCast) {
+ } else if (Operator::getOpcode(Ptr) == Instruction::BitCast ||
+ Operator::getOpcode(Ptr) == Instruction::AddrSpaceCast) {
Ptr = cast<Operator>(Ptr)->getOperand(0);
} else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(Ptr)) {
if (GA->mayBeOverridden())
/// GetStringLengthH - If we can compute the length of the string pointed to by
/// the specified pointer, return 'len+1'. If we can't, return 0.
-static uint64_t GetStringLengthH(Value *V, SmallPtrSet<PHINode*, 32> &PHIs) {
+static uint64_t GetStringLengthH(Value *V, SmallPtrSetImpl<PHINode*> &PHIs) {
// Look through noop bitcast instructions.
V = V->stripPointerCasts();
for (unsigned Count = 0; MaxLookup == 0 || Count < MaxLookup; ++Count) {
if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
V = GEP->getPointerOperand();
- } else if (Operator::getOpcode(V) == Instruction::BitCast) {
+ } else if (Operator::getOpcode(V) == Instruction::BitCast ||
+ Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
V = cast<Operator>(V)->getOperand(0);
} else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
if (GA->mayBeOverridden())
return true;
case Instruction::UDiv:
case Instruction::URem:
- // x / y is undefined if y == 0, but calcuations like x / 3 are safe.
+ // x / y is undefined if y == 0, but calculations like x / 3 are safe.
return isKnownNonZero(Inst->getOperand(1), TD);
case Instruction::SDiv:
case Instruction::SRem: {
// 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();
+ return LI->getPointerOperand()->isDereferenceablePointer(TD);
}
case Instruction::Call: {
if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
switch (II->getIntrinsicID()) {
- // These synthetic intrinsics have no side-effects, and just mark
+ // 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...
// Alloca never returns null, malloc might.
if (isa<AllocaInst>(V)) return true;
- // A byval or inalloca argument is never null.
+ // A byval, inalloca, or nonnull argument is never null.
if (const Argument *A = dyn_cast<Argument>(V))
- return A->hasByValOrInAllocaAttr();
+ return A->hasByValOrInAllocaAttr() || A->hasNonNullAttr();
// Global values are not null unless extern weak.
if (const GlobalValue *GV = dyn_cast<GlobalValue>(V))
return !GV->hasExternalWeakLinkage();
+ if (ImmutableCallSite CS = V)
+ if (CS.isReturnNonNull())
+ return true;
+
// operator new never returns null.
if (isOperatorNewLikeFn(V, TLI, /*LookThroughBitCast=*/true))
return true;
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