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[KnownBits] Introduce anyext instead of passing a flag into zext 

Summary:
This was a very odd API, where you had to pass a flag into a zext
function to say whether the extended bits really were zero or not. All
callers passed in a literal true or false.

I think it's much clearer to make the function name reflect the
operation being performed on the value we're tracking (rather than on
the KnownBits Zero and One fields), so zext means the value is being
zero extended and new function anyext means the value is being extended
with unknown bits.

NFC.

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D74482
This commit is contained in:
Jay Foad 2020-02-12 13:27:28 +00:00
parent 137415ad28
commit 32aac25637
11 changed files with 52 additions and 44 deletions
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47
llvm/include/llvm/Support/KnownBits.h
View File

@ -122,39 +122,48 @@ public:
return ~Zero;
}
/// Truncate the underlying known Zero and One bits. This is equivalent
/// to truncating the value we're tracking.
/// Return known bits for a truncation of the value we're tracking.
KnownBits trunc(unsigned BitWidth) const {
return KnownBits(Zero.trunc(BitWidth), One.trunc(BitWidth));
}
/// Extends the underlying known Zero and One bits.
/// By setting ExtendedBitsAreKnownZero=true this will be equivalent to
/// zero extending the value we're tracking.
/// With ExtendedBitsAreKnownZero=false the extended bits are set to unknown.
KnownBits zext(unsigned BitWidth, bool ExtendedBitsAreKnownZero) const {
/// Return known bits for an "any" extension of the value we're tracking,
/// where we don't know anything about the extended bits.
KnownBits anyext(unsigned BitWidth) const {
return KnownBits(Zero.zext(BitWidth), One.zext(BitWidth));
}
/// Return known bits for a zero extension of the value we're tracking.
KnownBits zext(unsigned BitWidth) const {
unsigned OldBitWidth = getBitWidth();
APInt NewZero = Zero.zext(BitWidth);
if (ExtendedBitsAreKnownZero)
NewZero.setBitsFrom(OldBitWidth);
NewZero.setBitsFrom(OldBitWidth);
return KnownBits(NewZero, One.zext(BitWidth));
}
/// Sign extends the underlying known Zero and One bits. This is equivalent
/// to sign extending the value we're tracking.
/// Return known bits for a sign extension of the value we're tracking.
KnownBits sext(unsigned BitWidth) const {
return KnownBits(Zero.sext(BitWidth), One.sext(BitWidth));
}
/// Extends or truncates the underlying known Zero and One bits. When
/// extending the extended bits can either be set as known zero (if
/// ExtendedBitsAreKnownZero=true) or as unknown (if
/// ExtendedBitsAreKnownZero=false).
KnownBits zextOrTrunc(unsigned BitWidth,
bool ExtendedBitsAreKnownZero) const {
/// Return known bits for an "any" extension or truncation of the value we're
/// tracking.
KnownBits anyextOrTrunc(unsigned BitWidth) const {
if (BitWidth > getBitWidth())
return zext(BitWidth, ExtendedBitsAreKnownZero);
return KnownBits(Zero.zextOrTrunc(BitWidth), One.zextOrTrunc(BitWidth));
return anyext(BitWidth);
if (BitWidth < getBitWidth())
return trunc(BitWidth);
return *this;
}
/// Return known bits for a zero extension or truncation of the value we're
/// tracking.
KnownBits zextOrTrunc(unsigned BitWidth) const {
if (BitWidth > getBitWidth())
return zext(BitWidth);
if (BitWidth < getBitWidth())
return trunc(BitWidth);
return *this;
}
/// Return a KnownBits with the extracted bits

2
llvm/lib/Analysis/ScalarEvolution.cpp
View File

@ -5736,7 +5736,7 @@ ScalarEvolution::getRangeRef(const SCEV *S,
// For a SCEVUnknown, ask ValueTracking.
KnownBits Known = computeKnownBits(U->getValue(), DL, 0, &AC, nullptr, &DT);
if (Known.getBitWidth() != BitWidth)
Known = Known.zextOrTrunc(BitWidth, true);
Known = Known.zextOrTrunc(BitWidth);
// If Known does not result in full-set, intersect with it.
if (Known.getMinValue() != Known.getMaxValue() + 1)
ConservativeResult = ConservativeResult.intersectWith(

4
llvm/lib/Analysis/ValueTracking.cpp
View File

@ -1254,9 +1254,9 @@ static void computeKnownBitsFromOperator(const Operator *I,
Q.DL.getTypeSizeInBits(ScalarTy);
assert(SrcBitWidth && "SrcBitWidth can't be zero");
Known = Known.zextOrTrunc(SrcBitWidth, false);
Known = Known.anyextOrTrunc(SrcBitWidth);
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
Known = Known.zextOrTrunc(BitWidth, true /* ExtendedBitsAreKnownZero */);
Known = Known.zextOrTrunc(BitWidth);
break;
}
case Instruction::BitCast: {

6
llvm/lib/CodeGen/GlobalISel/GISelKnownBits.cpp
View File

@ -294,7 +294,7 @@ void GISelKnownBits::computeKnownBitsImpl(Register R, KnownBits &Known,
case TargetOpcode::G_ANYEXT: {
computeKnownBitsImpl(MI.getOperand(1).getReg(), Known, DemandedElts,
Depth + 1);
Known = Known.zext(BitWidth, true /* ExtendedBitsAreKnownZero */);
Known = Known.zext(BitWidth);
break;
}
case TargetOpcode::G_LOAD: {
@ -360,9 +360,9 @@ void GISelKnownBits::computeKnownBitsImpl(Register R, KnownBits &Known,
? DL.getIndexSizeInBits(SrcTy.getAddressSpace())
: SrcTy.getSizeInBits();
assert(SrcBitWidth && "SrcBitWidth can't be zero");
Known = Known.zextOrTrunc(SrcBitWidth, true);
Known = Known.zextOrTrunc(SrcBitWidth);
computeKnownBitsImpl(SrcReg, Known, DemandedElts, Depth + 1);
Known = Known.zextOrTrunc(BitWidth, true);
Known = Known.zextOrTrunc(BitWidth);
if (BitWidth > SrcBitWidth)
Known.Zero.setBitsFrom(SrcBitWidth);
break;

2
llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
View File

@ -407,7 +407,7 @@ FunctionLoweringInfo::GetLiveOutRegInfo(unsigned Reg, unsigned BitWidth) {
if (BitWidth > LOI->Known.getBitWidth()) {
LOI->NumSignBits = 1;
LOI->Known = LOI->Known.zext(BitWidth, false /* => any extend */);
LOI->Known = LOI->Known.anyext(BitWidth);
}
return LOI;

10
llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
View File

@ -3061,12 +3061,12 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
EVT InVT = Op.getOperand(0).getValueType();
APInt InDemandedElts = DemandedElts.zextOrSelf(InVT.getVectorNumElements());
Known = computeKnownBits(Op.getOperand(0), InDemandedElts, Depth + 1);
Known = Known.zext(BitWidth, true /* ExtendedBitsAreKnownZero */);
Known = Known.zext(BitWidth);
break;
}
case ISD::ZERO_EXTEND: {
Known = computeKnownBits(Op.getOperand(0), DemandedElts, Depth + 1);
Known = Known.zext(BitWidth, true /* ExtendedBitsAreKnownZero */);
Known = Known.zext(BitWidth);
break;
}
case ISD::SIGN_EXTEND_VECTOR_INREG: {
@ -3089,12 +3089,12 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
EVT InVT = Op.getOperand(0).getValueType();
APInt InDemandedElts = DemandedElts.zextOrSelf(InVT.getVectorNumElements());
Known = computeKnownBits(Op.getOperand(0), InDemandedElts, Depth + 1);
Known = Known.zext(BitWidth, false /* ExtendedBitsAreKnownZero */);
Known = Known.anyext(BitWidth);
break;
}
case ISD::ANY_EXTEND: {
Known = computeKnownBits(Op.getOperand(0), DemandedElts, Depth + 1);
Known = Known.zext(BitWidth, false /* ExtendedBitsAreKnownZero */);
Known = Known.anyext(BitWidth);
break;
}
case ISD::TRUNCATE: {
@ -3257,7 +3257,7 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
Known = computeKnownBits(InVec, DemandedSrcElts, Depth + 1);
if (BitWidth > EltBitWidth)
Known = Known.zext(BitWidth, false /* => any extend */);
Known = Known.anyext(BitWidth);
break;
}
case ISD::INSERT_VECTOR_ELT: {

10
llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
View File

@ -864,7 +864,7 @@ bool TargetLowering::SimplifyDemandedBits(
APInt SrcDemandedBits = DemandedBits.zextOrSelf(SrcBitWidth);
if (SimplifyDemandedBits(Src, SrcDemandedBits, SrcKnown, TLO, Depth + 1))
return true;
Known = SrcKnown.zextOrTrunc(BitWidth, false);
Known = SrcKnown.anyextOrTrunc(BitWidth);
break;
}
case ISD::BUILD_VECTOR:
@ -910,7 +910,7 @@ bool TargetLowering::SimplifyDemandedBits(
if (SimplifyDemandedBits(Scl, DemandedSclBits, KnownScl, TLO, Depth + 1))
return true;
Known = KnownScl.zextOrTrunc(BitWidth, false);
Known = KnownScl.anyextOrTrunc(BitWidth);
KnownBits KnownVec;
if (SimplifyDemandedBits(Vec, DemandedBits, DemandedVecElts, KnownVec, TLO,
@ -1765,7 +1765,7 @@ bool TargetLowering::SimplifyDemandedBits(
return true;
assert(!Known.hasConflict() && "Bits known to be one AND zero?");
assert(Known.getBitWidth() == InBits && "Src width has changed?");
Known = Known.zext(BitWidth, true /* ExtendedBitsAreKnownZero */);
Known = Known.zext(BitWidth);
break;
}
case ISD::SIGN_EXTEND:
@ -1838,7 +1838,7 @@ bool TargetLowering::SimplifyDemandedBits(
return true;
assert(!Known.hasConflict() && "Bits known to be one AND zero?");
assert(Known.getBitWidth() == InBits && "Src width has changed?");
Known = Known.zext(BitWidth, false /* => any extend */);
Known = Known.anyext(BitWidth);
// Attempt to avoid multi-use ops if we don't need anything from them.
if (SDValue NewSrc = SimplifyMultipleUseDemandedBits(
@ -1952,7 +1952,7 @@ bool TargetLowering::SimplifyDemandedBits(
Known = Known2;
if (BitWidth > EltBitWidth)
Known = Known.zext(BitWidth, false /* => any extend */);
Known = Known.anyext(BitWidth);
break;
}
case ISD::BITCAST: {

2
llvm/lib/Target/ARM/ARMISelLowering.cpp
View File

@ -15853,7 +15853,7 @@ void ARMTargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
if (Op.getOpcode() == ARMISD::VGETLANEs)
Known = Known.sext(DstSz);
else {
Known = Known.zext(DstSz, true /* extended bits are known zero */);
Known = Known.zext(DstSz);
}
assert(DstSz == Known.getBitWidth());
break;

4
llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
View File

@ -6607,7 +6607,7 @@ SystemZTargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
APInt SrcDemE = getDemandedSrcElements(Op, DemandedElts, 0);
Known = DAG.computeKnownBits(SrcOp, SrcDemE, Depth + 1);
if (IsLogical) {
Known = Known.zext(BitWidth, true);
Known = Known.zext(BitWidth);
} else
Known = Known.sext(BitWidth);
break;
@ -6636,7 +6636,7 @@ SystemZTargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
// Known has the width of the source operand(s). Adjust if needed to match
// the passed bitwidth.
if (Known.getBitWidth() != BitWidth)
Known = Known.zextOrTrunc(BitWidth, false);
Known = Known.anyextOrTrunc(BitWidth);
}
static unsigned computeNumSignBitsBinOp(SDValue Op, const APInt &DemandedElts,

6
llvm/lib/Target/X86/X86ISelLowering.cpp
View File

@ -32945,7 +32945,7 @@ void X86TargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
APInt DemandedElt = APInt::getOneBitSet(SrcVT.getVectorNumElements(),
Op.getConstantOperandVal(1));
Known = DAG.computeKnownBits(Src, DemandedElt, Depth + 1);
Known = Known.zextOrTrunc(BitWidth, false);
Known = Known.anyextOrTrunc(BitWidth);
Known.Zero.setBitsFrom(SrcVT.getScalarSizeInBits());
break;
}
@ -33059,7 +33059,7 @@ void X86TargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
if ((Shift + Length) <= BitWidth) {
Known = DAG.computeKnownBits(Op0, Depth + 1);
Known = Known.extractBits(Length, Shift);
Known = Known.zextOrTrunc(BitWidth, true /* ExtBitsAreKnownZero */);
Known = Known.zextOrTrunc(BitWidth);
}
}
break;
@ -36484,7 +36484,7 @@ bool X86TargetLowering::SimplifyDemandedBitsForTargetNode(
return TLO.CombineTo(
Op, TLO.DAG.getNode(Opc, SDLoc(Op), VT, V, Op.getOperand(1)));
Known = KnownVec.zext(BitWidth, true);
Known = KnownVec.zext(BitWidth);
return false;
}
break;

3
llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
View File

@ -396,8 +396,7 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
if (SimplifyDemandedBits(I, 0, InputDemandedMask, InputKnown, Depth + 1))
return I;
assert(InputKnown.getBitWidth() == SrcBitWidth && "Src width changed?");
Known = InputKnown.zextOrTrunc(BitWidth,
true /* ExtendedBitsAreKnownZero */);
Known = InputKnown.zextOrTrunc(BitWidth);
assert(!Known.hasConflict() && "Bits known to be one AND zero?");
break;
}