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[KnownBits] Move ValueTracking/SelectionDAG UREM KnownBits handling to KnownBits::urem. NFCI.

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Both these have the same implementation - so move them to a single KnownBits copy.

GlobalISel will be able to use this as well with minimal effort.
This commit is contained in:
Simon Pilgrim 2020-11-05 14:29:13 +00:00
parent 0830936d52
commit 329a4a468b
5 changed files with 36 additions and 40 deletions
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3
include/llvm/Support/KnownBits.h
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@ -261,6 +261,9 @@ public:
/// Compute known bits for udiv(LHS, RHS).
static KnownBits udiv(const KnownBits &LHS, const KnownBits &RHS);
/// Compute known bits for urem(LHS, RHS).
static KnownBits urem(const KnownBits &LHS, const KnownBits &RHS);
/// Compute known bits for umax(LHS, RHS).
static KnownBits umax(const KnownBits &LHS, const KnownBits &RHS);

22
lib/Analysis/ValueTracking.cpp
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@ -1327,29 +1327,11 @@ static void computeKnownBitsFromOperator(const Operator *I,
Known.makeNonNegative();
break;
case Instruction::URem: {
if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) {
const APInt &RA = Rem->getValue();
if (RA.isPowerOf2()) {
APInt LowBits = (RA - 1);
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
Known.Zero |= ~LowBits;
Known.One &= 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.
case Instruction::URem:
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
unsigned Leaders =
std::max(Known.countMinLeadingZeros(), Known2.countMinLeadingZeros());
Known.resetAll();
Known.Zero.setHighBits(Leaders);
Known = KnownBits::urem(Known, Known2);
break;
}
case Instruction::Alloca:
Known.Zero.setLowBits(Log2(cast<AllocaInst>(I)->getAlign()));
break;

21
lib/CodeGen/SelectionDAG/SelectionDAG.cpp
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@ -3274,28 +3274,9 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
}
break;
case ISD::UREM: {
if (ConstantSDNode *Rem = isConstOrConstSplat(Op.getOperand(1))) {
const APInt &RA = Rem->getAPIntValue();
if (RA.isPowerOf2()) {
APInt LowBits = (RA - 1);
Known2 = computeKnownBits(Op.getOperand(0), DemandedElts, Depth + 1);
// The upper bits are all zero, the lower ones are unchanged.
Known.Zero = Known2.Zero | ~LowBits;
Known.One = Known2.One & 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.
Known = computeKnownBits(Op.getOperand(0), DemandedElts, Depth + 1);
Known2 = computeKnownBits(Op.getOperand(1), DemandedElts, Depth + 1);
uint32_t Leaders =
std::max(Known.countMinLeadingZeros(), Known2.countMinLeadingZeros());
Known.resetAll();
Known.Zero.setHighBits(Leaders);
Known = KnownBits::urem(Known, Known2);
break;
}
case ISD::EXTRACT_ELEMENT: {

21
lib/Support/KnownBits.cpp
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@ -324,6 +324,27 @@ KnownBits KnownBits::udiv(const KnownBits &LHS, const KnownBits &RHS) {
return Known;
}
KnownBits KnownBits::urem(const KnownBits &LHS, const KnownBits &RHS) {
unsigned BitWidth = LHS.getBitWidth();
assert(!LHS.hasConflict() && !RHS.hasConflict());
KnownBits Known(BitWidth);
if (RHS.isConstant() && RHS.getConstant().isPowerOf2()) {
// The upper bits are all zero, the lower ones are unchanged.
APInt LowBits = RHS.getConstant() - 1;
Known.Zero = LHS.Zero | ~LowBits;
Known.One = LHS.One & LowBits;
return Known;
}
// Since the result is less than or equal to either operand, any leading
// zero bits in either operand must also exist in the result.
uint32_t Leaders =
std::max(LHS.countMinLeadingZeros(), RHS.countMinLeadingZeros());
Known.Zero.setHighBits(Leaders);
return Known;
}
KnownBits &KnownBits::operator&=(const KnownBits &RHS) {
// Result bit is 0 if either operand bit is 0.
Zero |= RHS.Zero;

9
unittests/Support/KnownBitsTest.cpp
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@ -114,6 +114,7 @@ TEST(KnownBitsTest, BinaryExhaustive) {
KnownBits KnownSMin(KnownAnd);
KnownBits KnownMul(KnownAnd);
KnownBits KnownUDiv(KnownAnd);
KnownBits KnownURem(KnownAnd);
KnownBits KnownShl(KnownAnd);
KnownBits KnownLShr(KnownAnd);
KnownBits KnownAShr(KnownAnd);
@ -158,6 +159,10 @@ TEST(KnownBitsTest, BinaryExhaustive) {
Res = N1.udiv(N2);
KnownUDiv.One &= Res;
KnownUDiv.Zero &= ~Res;
Res = N1.urem(N2);
KnownURem.One &= Res;
KnownURem.Zero &= ~Res;
}
if (N2.ult(1ULL << N1.getBitWidth())) {
@ -218,6 +223,10 @@ TEST(KnownBitsTest, BinaryExhaustive) {
EXPECT_TRUE(ComputedUDiv.Zero.isSubsetOf(KnownUDiv.Zero));
EXPECT_TRUE(ComputedUDiv.One.isSubsetOf(KnownUDiv.One));
KnownBits ComputedURem = KnownBits::urem(Known1, Known2);
EXPECT_TRUE(ComputedURem.Zero.isSubsetOf(KnownURem.Zero));
EXPECT_TRUE(ComputedURem.One.isSubsetOf(KnownURem.One));
KnownBits ComputedShl = KnownBits::shl(Known1, Known2);
EXPECT_TRUE(ComputedShl.Zero.isSubsetOf(KnownShl.Zero));
EXPECT_TRUE(ComputedShl.One.isSubsetOf(KnownShl.One));