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[ValueTracking] Update computeKnownBitsFromShiftOperator callbacks to take KnownBits shift amount. NFCI. 

We were creating this internally, but will need to support general KnownBits amounts as part of D90479.
This commit is contained in:
Simon Pilgrim 2020-11-12 16:56:40 +00:00
parent 40a42f9f3f
commit f72d350bfb
1 changed files with 12 additions and 14 deletions
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26
llvm/lib/Analysis/ValueTracking.cpp
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@ -987,14 +987,14 @@ static void computeKnownBitsFromAssume(const Value *V, KnownBits &Known,
static void computeKnownBitsFromShiftOperator(
const Operator *I, const APInt &DemandedElts, KnownBits &Known,
KnownBits &Known2, unsigned Depth, const Query &Q,
function_ref<KnownBits(const KnownBits &, unsigned)> KF) {
function_ref<KnownBits(const KnownBits &, const KnownBits &)> KF) {
unsigned BitWidth = Known.getBitWidth();
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
if (Known.isConstant()) {
unsigned ShiftAmt = Known.getConstant().getLimitedValue(BitWidth - 1);
Known = KF(Known2, ShiftAmt);
Known = KF(Known2, KnownBits::makeConstant(APInt(32, ShiftAmt)));
// If the known bits conflict, this must be an overflowing left shift, so
// the shift result is poison. We can return anything we want. Choose 0 for
@ -1058,7 +1058,8 @@ static void computeKnownBitsFromShiftOperator(
continue;
}
Known = KnownBits::commonBits(Known, KF(Known2, ShiftAmt));
Known = KnownBits::commonBits(
Known, KF(Known2, KnownBits::makeConstant(APInt(32, ShiftAmt))));
}
// If the known bits conflict, the result is poison. Return a 0 and hope the
@ -1222,15 +1223,14 @@ static void computeKnownBitsFromOperator(const Operator *I,
}
case Instruction::Shl: {
bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
auto KF = [NSW](const KnownBits &KnownShiftVal, unsigned ShiftAmt) {
KnownBits KnownShiftAmt = KnownBits::makeConstant(APInt(32, ShiftAmt));
KnownBits Result = KnownBits::shl(KnownShiftVal, KnownShiftAmt);
auto KF = [NSW](const KnownBits &KnownVal, const KnownBits &KnownAmt) {
KnownBits Result = KnownBits::shl(KnownVal, KnownAmt);
// If this shift has "nsw" keyword, then the result is either a poison
// value or has the same sign bit as the first operand.
if (NSW) {
if (KnownShiftVal.Zero.isSignBitSet())
if (KnownVal.Zero.isSignBitSet())
Result.Zero.setSignBit();
if (KnownShiftVal.One.isSignBitSet())
if (KnownVal.One.isSignBitSet())
Result.One.setSignBit();
}
return Result;
@ -1240,18 +1240,16 @@ static void computeKnownBitsFromOperator(const Operator *I,
break;
}
case Instruction::LShr: {
auto KF = [](const KnownBits &KnownShiftVal, unsigned ShiftAmt) {
KnownBits KnownShiftAmt = KnownBits::makeConstant(APInt(32, ShiftAmt));
return KnownBits::lshr(KnownShiftVal, KnownShiftAmt);
auto KF = [](const KnownBits &KnownVal, const KnownBits &KnownAmt) {
return KnownBits::lshr(KnownVal, KnownAmt);
};
computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
KF);
break;
}
case Instruction::AShr: {
auto KF = [](const KnownBits &KnownShiftVal, unsigned ShiftAmt) {
KnownBits KnownShiftAmt = KnownBits::makeConstant(APInt(32, ShiftAmt));
return KnownBits::ashr(KnownShiftVal, KnownShiftAmt);
auto KF = [](const KnownBits &KnownVal, const KnownBits &KnownAmt) {
return KnownBits::ashr(KnownVal, KnownAmt);
};
computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
KF);