Skip to content

[NFC][ValueTracking] Hoist the matching of RHS constant #125818

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Feb 5, 2025
Merged

[NFC][ValueTracking] Hoist the matching of RHS constant #125818

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
66 changes: 33 additions & 33 deletions llvm/lib/Analysis/ValueTracking.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -683,28 +683,30 @@ static void computeKnownBitsFromCmp(const Value *V, CmpInst::Predicate Pred,

Value *Y;
const APInt *Mask, *C;
if (!match(RHS, m_APInt(C)))
return;

uint64_t ShAmt;
switch (Pred) {
case ICmpInst::ICMP_EQ:
// assume(V = C)
if (match(LHS, m_V) && match(RHS, m_APInt(C))) {
if (match(LHS, m_V)) {
Known = Known.unionWith(KnownBits::makeConstant(*C));
// assume(V & Mask = C)
} else if (match(LHS, m_c_And(m_V, m_Value(Y))) &&
match(RHS, m_APInt(C))) {
} else if (match(LHS, m_c_And(m_V, m_Value(Y)))) {
// For one bits in Mask, we can propagate bits from C to V.
Known.One |= *C;
if (match(Y, m_APInt(Mask)))
Known.Zero |= ~*C & *Mask;
// assume(V | Mask = C)
} else if (match(LHS, m_c_Or(m_V, m_Value(Y))) && match(RHS, m_APInt(C))) {
} else if (match(LHS, m_c_Or(m_V, m_Value(Y)))) {
// For zero bits in Mask, we can propagate bits from C to V.
Known.Zero |= ~*C;
if (match(Y, m_APInt(Mask)))
Known.One |= *C & ~*Mask;
// assume(V << ShAmt = C)
} else if (match(LHS, m_Shl(m_V, m_ConstantInt(ShAmt))) &&
match(RHS, m_APInt(C)) && ShAmt < BitWidth) {
ShAmt < BitWidth) {
// For those bits in C that are known, we can propagate them to known
// bits in V shifted to the right by ShAmt.
KnownBits RHSKnown = KnownBits::makeConstant(*C);
Expand All @@ -713,7 +715,7 @@ static void computeKnownBitsFromCmp(const Value *V, CmpInst::Predicate Pred,
Known = Known.unionWith(RHSKnown);
// assume(V >> ShAmt = C)
} else if (match(LHS, m_Shr(m_V, m_ConstantInt(ShAmt))) &&
match(RHS, m_APInt(C)) && ShAmt < BitWidth) {
ShAmt < BitWidth) {
KnownBits RHSKnown = KnownBits::makeConstant(*C);
// For those bits in RHS that are known, we can propagate them to known
// bits in V shifted to the right by C.
Expand All @@ -724,38 +726,36 @@ static void computeKnownBitsFromCmp(const Value *V, CmpInst::Predicate Pred,
case ICmpInst::ICMP_NE: {
// assume (V & B != 0) where B is a power of 2
const APInt *BPow2;
if (match(LHS, m_And(m_V, m_Power2(BPow2))) && match(RHS, m_Zero()))
if (C->isZero() && match(LHS, m_And(m_V, m_Power2(BPow2))))
Known.One |= *BPow2;
break;
}
default:
if (match(RHS, m_APInt(C))) {
const APInt *Offset = nullptr;
if (match(LHS, m_CombineOr(m_V, m_AddLike(m_V, m_APInt(Offset))))) {
ConstantRange LHSRange = ConstantRange::makeAllowedICmpRegion(Pred, *C);
if (Offset)
LHSRange = LHSRange.sub(*Offset);
Known = Known.unionWith(LHSRange.toKnownBits());
}
if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE) {
// X & Y u> C -> X u> C && Y u> C
// X nuw- Y u> C -> X u> C
if (match(LHS, m_c_And(m_V, m_Value())) ||
match(LHS, m_NUWSub(m_V, m_Value())))
Known.One.setHighBits(
(*C + (Pred == ICmpInst::ICMP_UGT)).countLeadingOnes());
}
if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) {
// X | Y u< C -> X u< C && Y u< C
// X nuw+ Y u< C -> X u< C && Y u< C
if (match(LHS, m_c_Or(m_V, m_Value())) ||
match(LHS, m_c_NUWAdd(m_V, m_Value()))) {
Known.Zero.setHighBits(
(*C - (Pred == ICmpInst::ICMP_ULT)).countLeadingZeros());
}
default: {
const APInt *Offset = nullptr;
if (match(LHS, m_CombineOr(m_V, m_AddLike(m_V, m_APInt(Offset))))) {
ConstantRange LHSRange = ConstantRange::makeAllowedICmpRegion(Pred, *C);
if (Offset)
LHSRange = LHSRange.sub(*Offset);
Known = Known.unionWith(LHSRange.toKnownBits());
}
if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE) {
// X & Y u> C -> X u> C && Y u> C
// X nuw- Y u> C -> X u> C
if (match(LHS, m_c_And(m_V, m_Value())) ||
match(LHS, m_NUWSub(m_V, m_Value())))
Known.One.setHighBits(
(*C + (Pred == ICmpInst::ICMP_UGT)).countLeadingOnes());
}
if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) {
// X | Y u< C -> X u< C && Y u< C
// X nuw+ Y u< C -> X u< C && Y u< C
if (match(LHS, m_c_Or(m_V, m_Value())) ||
match(LHS, m_c_NUWAdd(m_V, m_Value()))) {
Known.Zero.setHighBits(
(*C - (Pred == ICmpInst::ICMP_ULT)).countLeadingZeros());
}
}
break;
} break;
}
}

Expand Down