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[InstCombine] Fold icmp spred (mul nsw X, Z), (mul nsw Y, Z) into icmp spred X, Y #110630

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Oct 1, 2024
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[InstCombine] Fold icmp spred (mul nsw X, Z), (mul nsw Y, Z) into icmp spred X, Y #110630

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2c014e9
[InstCombine] Add pre-commit tests. NFC.
dtcxzyw Oct 1, 2024
df173c3
[InstCombine] Fold `icmp spred (mul nsw X, Z), (mul nsw Y, Z)` into `…
dtcxzyw Oct 1, 2024
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67 changes: 38 additions & 29 deletions llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5273,37 +5273,46 @@ Instruction *InstCombinerImpl::foldICmpBinOp(ICmpInst &I,

{
// Try to remove shared multiplier from comparison:
// X * Z u{lt/le/gt/ge}/eq/ne Y * Z
// X * Z pred Y * Z
Value *X, *Y, *Z;
if (Pred == ICmpInst::getUnsignedPredicate(Pred) &&
((match(Op0, m_Mul(m_Value(X), m_Value(Z))) &&
match(Op1, m_c_Mul(m_Specific(Z), m_Value(Y)))) ||
(match(Op0, m_Mul(m_Value(Z), m_Value(X))) &&
match(Op1, m_c_Mul(m_Specific(Z), m_Value(Y)))))) {
bool NonZero;
if (ICmpInst::isEquality(Pred)) {
// If X != Y, fold (X *nw Z) eq/ne (Y *nw Z) -> Z eq/ne 0
if (((Op0HasNSW && Op1HasNSW) || (Op0HasNUW && Op1HasNUW)) &&
isKnownNonEqual(X, Y, DL, &AC, &I, &DT))
return new ICmpInst(Pred, Z, Constant::getNullValue(Z->getType()));

KnownBits ZKnown = computeKnownBits(Z, 0, &I);
// if Z % 2 != 0
// X * Z eq/ne Y * Z -> X eq/ne Y
if (ZKnown.countMaxTrailingZeros() == 0)
return new ICmpInst(Pred, X, Y);
NonZero = !ZKnown.One.isZero() || isKnownNonZero(Z, Q);
// if Z != 0 and nsw(X * Z) and nsw(Y * Z)
// X * Z eq/ne Y * Z -> X eq/ne Y
if (NonZero && BO0 && BO1 && Op0HasNSW && Op1HasNSW)
if ((match(Op0, m_Mul(m_Value(X), m_Value(Z))) &&
match(Op1, m_c_Mul(m_Specific(Z), m_Value(Y)))) ||
(match(Op0, m_Mul(m_Value(Z), m_Value(X))) &&
match(Op1, m_c_Mul(m_Specific(Z), m_Value(Y))))) {
if (ICmpInst::isSigned(Pred)) {
if (Op0HasNSW && Op1HasNSW) {
KnownBits ZKnown = computeKnownBits(Z, 0, &I);
if (ZKnown.isStrictlyPositive())
return new ICmpInst(Pred, X, Y);
if (ZKnown.isNegative())
return new ICmpInst(ICmpInst::getSwappedPredicate(Pred), X, Y);
}
} else {
bool NonZero;
if (ICmpInst::isEquality(Pred)) {
// If X != Y, fold (X *nw Z) eq/ne (Y *nw Z) -> Z eq/ne 0
if (((Op0HasNSW && Op1HasNSW) || (Op0HasNUW && Op1HasNUW)) &&
isKnownNonEqual(X, Y, DL, &AC, &I, &DT))
return new ICmpInst(Pred, Z, Constant::getNullValue(Z->getType()));

KnownBits ZKnown = computeKnownBits(Z, 0, &I);
// if Z % 2 != 0
// X * Z eq/ne Y * Z -> X eq/ne Y
if (ZKnown.countMaxTrailingZeros() == 0)
return new ICmpInst(Pred, X, Y);
NonZero = !ZKnown.One.isZero() || isKnownNonZero(Z, Q);
// if Z != 0 and nsw(X * Z) and nsw(Y * Z)
// X * Z eq/ne Y * Z -> X eq/ne Y
if (NonZero && BO0 && BO1 && Op0HasNSW && Op1HasNSW)
return new ICmpInst(Pred, X, Y);
} else
NonZero = isKnownNonZero(Z, Q);

// If Z != 0 and nuw(X * Z) and nuw(Y * Z)
// X * Z u{lt/le/gt/ge}/eq/ne Y * Z -> X u{lt/le/gt/ge}/eq/ne Y
if (NonZero && BO0 && BO1 && Op0HasNUW && Op1HasNUW)
return new ICmpInst(Pred, X, Y);
} else
NonZero = isKnownNonZero(Z, Q);

// If Z != 0 and nuw(X * Z) and nuw(Y * Z)
// X * Z u{lt/le/gt/ge}/eq/ne Y * Z -> X u{lt/le/gt/ge}/eq/ne Y
if (NonZero && BO0 && BO1 && Op0HasNUW && Op1HasNUW)
return new ICmpInst(Pred, X, Y);
}
}
}

Expand Down
134 changes: 134 additions & 0 deletions llvm/test/Transforms/InstCombine/icmp-mul.ll
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Expand Up @@ -1330,3 +1330,137 @@ entry:
%cmp = icmp ult i8 %mul1, %mul2
ret i1 %cmp
}

define i1 @icmp_mul_nsw_slt(i8 %x, i8 %y) {
; CHECK-LABEL: @icmp_mul_nsw_slt(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: ret i1 [[CMP]]
;
entry:
%mul1 = mul nsw i8 %x, 7
%mul2 = mul nsw i8 %y, 7
%cmp = icmp slt i8 %mul1, %mul2
ret i1 %cmp
}

define i1 @icmp_mul_nsw_sle(i8 %x, i8 %y) {
; CHECK-LABEL: @icmp_mul_nsw_sle(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[CMP:%.*]] = icmp sle i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: ret i1 [[CMP]]
;
entry:
%mul1 = mul nsw i8 %x, 7
%mul2 = mul nsw i8 %y, 7
%cmp = icmp sle i8 %mul1, %mul2
ret i1 %cmp
}

define i1 @icmp_mul_nsw_sgt(i8 %x, i8 %y) {
; CHECK-LABEL: @icmp_mul_nsw_sgt(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: ret i1 [[CMP]]
;
entry:
%mul1 = mul nsw i8 %x, 7
%mul2 = mul nsw i8 %y, 7
%cmp = icmp sgt i8 %mul1, %mul2
ret i1 %cmp
}

define i1 @icmp_mul_nsw_sge(i8 %x, i8 %y) {
; CHECK-LABEL: @icmp_mul_nsw_sge(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[CMP:%.*]] = icmp sge i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: ret i1 [[CMP]]
;
entry:
%mul1 = mul nsw i8 %x, 7
%mul2 = mul nsw i8 %y, 7
%cmp = icmp sge i8 %mul1, %mul2
ret i1 %cmp
}

define i1 @icmp_mul_nsw_slt_neg(i8 %x, i8 %y) {
; CHECK-LABEL: @icmp_mul_nsw_slt_neg(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: ret i1 [[CMP]]
;
entry:
%mul1 = mul nsw i8 %x, -7
%mul2 = mul nsw i8 %y, -7
%cmp = icmp slt i8 %mul1, %mul2
ret i1 %cmp
}

define i1 @icmp_mul_nsw_slt_neg_var(i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @icmp_mul_nsw_slt_neg_var(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[COND:%.*]] = icmp slt i8 [[Z:%.*]], 0
; CHECK-NEXT: call void @llvm.assume(i1 [[COND]])
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: ret i1 [[CMP]]
;
entry:
%cond = icmp slt i8 %z, 0
call void @llvm.assume(i1 %cond)
%mul1 = mul nsw i8 %x, %z
%mul2 = mul nsw i8 %y, %z
%cmp = icmp slt i8 %mul1, %mul2
ret i1 %cmp
}

; Negative tests

define i1 @icmp_mul_nonsw_slt(i8 %x, i8 %y) {
; CHECK-LABEL: @icmp_mul_nonsw_slt(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[MUL1:%.*]] = mul i8 [[X:%.*]], 7
; CHECK-NEXT: [[MUL2:%.*]] = mul nsw i8 [[Y:%.*]], 7
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[MUL1]], [[MUL2]]
; CHECK-NEXT: ret i1 [[CMP]]
;
entry:
%mul1 = mul i8 %x, 7
%mul2 = mul nsw i8 %y, 7
%cmp = icmp slt i8 %mul1, %mul2
ret i1 %cmp
}

define i1 @icmp_mul_nsw_slt_unknown_sign(i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @icmp_mul_nsw_slt_unknown_sign(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[MUL1:%.*]] = mul nsw i8 [[X:%.*]], [[Z:%.*]]
; CHECK-NEXT: [[MUL2:%.*]] = mul nsw i8 [[Y:%.*]], [[Z]]
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[MUL1]], [[MUL2]]
; CHECK-NEXT: ret i1 [[CMP]]
;
entry:
%mul1 = mul nsw i8 %x, %z
%mul2 = mul nsw i8 %y, %z
%cmp = icmp slt i8 %mul1, %mul2
ret i1 %cmp
}

define i1 @icmp_mul_nsw_slt_may_be_zero(i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @icmp_mul_nsw_slt_may_be_zero(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[COND:%.*]] = icmp sgt i8 [[Z:%.*]], -1
; CHECK-NEXT: call void @llvm.assume(i1 [[COND]])
; CHECK-NEXT: [[MUL1:%.*]] = mul nsw i8 [[X:%.*]], [[Z]]
; CHECK-NEXT: [[MUL2:%.*]] = mul nsw i8 [[Y:%.*]], [[Z]]
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[MUL1]], [[MUL2]]
; CHECK-NEXT: ret i1 [[CMP]]
;
entry:
%cond = icmp sgt i8 %z, -1
call void @llvm.assume(i1 %cond)

%mul1 = mul nsw i8 %x, %z
%mul2 = mul nsw i8 %y, %z
%cmp = icmp slt i8 %mul1, %mul2
ret i1 %cmp
}
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