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[InstCombine] Fold (x == A) || (x & -Pow2) == A + 1 into range check #153842

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[InstCombine] Fold (x == A) || (x & -Pow2) == A + 1 into range check #153842

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pedroclobo Aug 15, 2025
434c092
[InstCombine] Fold `(x == A) || (x & -Pow2) == A + 1` into range check
pedroclobo Aug 15, 2025
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43 changes: 39 additions & 4 deletions llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1338,16 +1338,51 @@ Value *InstCombinerImpl::foldAndOrOfICmpsUsingRanges(ICmpInst *ICmp1,
V2 = X;
}

// Look through and with a negative power of 2 mask on V1 or V2. This
// detects idioms of the form `(x == A) || ((x & Mask) == A + 1)` where A + 1
// is aligned to the mask and A + 1 >= |Mask|. This pattern corresponds to a
// contiguous range check, which can be folded into an addition and compare.
// The same applies for `(x != A) && ((x & Mask) != A + 1)`.
auto AreContiguousRangePredicates = [](CmpPredicate Pred1, CmpPredicate Pred2,
bool IsAnd) {
if (IsAnd)
return Pred1 == ICmpInst::ICMP_NE && Pred2 == ICmpInst::ICMP_NE;
return Pred1 == ICmpInst::ICMP_EQ && Pred2 == ICmpInst::ICMP_EQ;
};
const APInt *Mask1 = nullptr, *Mask2 = nullptr;
bool MatchedAnd1 = false, MatchedAnd2 = false;
if (V1 != V2 && AreContiguousRangePredicates(Pred1, Pred2, IsAnd)) {
Value *X;
if (match(V1, m_OneUse(m_And(m_Value(X), m_NegatedPower2(Mask1)))) &&
C1->getBitWidth() == C2->getBitWidth() && *C1 == *C2 + 1 &&
C1->uge(Mask1->abs()) && C1->isPowerOf2()) {
MatchedAnd1 = true;
V1 = X;
}
if (match(V2, m_OneUse(m_And(m_Value(X), m_NegatedPower2(Mask2)))) &&
C1->getBitWidth() == C2->getBitWidth() && *C2 == *C1 + 1 &&
C2->uge(Mask2->abs()) && C2->isPowerOf2()) {
MatchedAnd2 = true;
V2 = X;
}
}

if (V1 != V2)
return nullptr;

ConstantRange CR1 = ConstantRange::makeExactICmpRegion(
IsAnd ? ICmpInst::getInverseCmpPredicate(Pred1) : Pred1, *C1);
ConstantRange CR1 =
MatchedAnd1
? ConstantRange(*C1, *C1 - *Mask1)
: ConstantRange::makeExactICmpRegion(
IsAnd ? ICmpInst::getInverseCmpPredicate(Pred1) : Pred1, *C1);
if (Offset1)
CR1 = CR1.subtract(*Offset1);

ConstantRange CR2 = ConstantRange::makeExactICmpRegion(
IsAnd ? ICmpInst::getInverseCmpPredicate(Pred2) : Pred2, *C2);
ConstantRange CR2 =
MatchedAnd2
? ConstantRange(*C2, *C2 - *Mask2)
: ConstantRange::makeExactICmpRegion(
IsAnd ? ICmpInst::getInverseCmpPredicate(Pred2) : Pred2, *C2);
if (Offset2)
CR2 = CR2.subtract(*Offset2);

Expand Down
195 changes: 195 additions & 0 deletions llvm/test/Transforms/InstCombine/and-or-icmps.ll
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Expand Up @@ -3491,3 +3491,198 @@ define i1 @and_icmp_eq_with_binary_range_operands(i8 range(i8 0, 2) %x, i8 range
%ret = and i1 %icmp1, %icmp2
ret i1 %ret
}

define i1 @or_icmp_eq_and_pow2(i32 %x) {
; CHECK-LABEL: @or_icmp_eq_and_pow2(
; CHECK-NEXT: [[TMP1:%.*]] = add i32 [[X:%.*]], -127
; CHECK-NEXT: [[RET:%.*]] = icmp ult i32 [[TMP1]], 33
; CHECK-NEXT: ret i1 [[RET]]
;
%icmp1 = icmp eq i32 %x, 127
%and = and i32 %x, -32
%icmp2 = icmp eq i32 %and, 128
%ret = or i1 %icmp1, %icmp2
ret i1 %ret
}

define i1 @or_icmp_eq_and_pow2_mask_equal_to_icmp(i32 %x) {
; CHECK-LABEL: @or_icmp_eq_and_pow2_mask_equal_to_icmp(
; CHECK-NEXT: [[TMP1:%.*]] = add i32 [[X:%.*]], -63
; CHECK-NEXT: [[RET:%.*]] = icmp ult i32 [[TMP1]], 65
; CHECK-NEXT: ret i1 [[RET]]
;
%icmp1 = icmp eq i32 %x, 63
%and = and i32 %x, -64
%icmp2 = icmp eq i32 %and, 64
%ret = or i1 %icmp1, %icmp2
ret i1 %ret
}

define i1 @and_icmp_ne_and_pow2(i32 %x) {
; CHECK-LABEL: @and_icmp_ne_and_pow2(
; CHECK-NEXT: [[TMP1:%.*]] = add i32 [[X:%.*]], -160
; CHECK-NEXT: [[RET:%.*]] = icmp ult i32 [[TMP1]], -33
; CHECK-NEXT: ret i1 [[RET]]
;
%icmp1 = icmp ne i32 %x, 127
%and = and i32 %x, -32
%icmp2 = icmp ne i32 %and, 128
%ret = and i1 %icmp1, %icmp2
ret i1 %ret
}

define i1 @and_icmp_ne_and_pow2_mask_equal_to_icmp(i32 %x) {
; CHECK-LABEL: @and_icmp_ne_and_pow2_mask_equal_to_icmp(
; CHECK-NEXT: [[TMP1:%.*]] = add i32 [[X:%.*]], -128
; CHECK-NEXT: [[RET:%.*]] = icmp ult i32 [[TMP1]], -65
; CHECK-NEXT: ret i1 [[RET]]
;
%icmp1 = icmp ne i32 %x, 63
%and = and i32 %x, -64
%icmp2 = icmp ne i32 %and, 64
%ret = and i1 %icmp1, %icmp2
ret i1 %ret
}

define i1 @or_icmp_eq_and_pow2_commute(i32 %x) {
; CHECK-LABEL: @or_icmp_eq_and_pow2_commute(
; CHECK-NEXT: [[TMP1:%.*]] = add i32 [[X:%.*]], -127
; CHECK-NEXT: [[TMP4:%.*]] = icmp ult i32 [[TMP1]], 33
; CHECK-NEXT: ret i1 [[TMP4]]
;
%and = and i32 %x, -32
%icmp1 = icmp eq i32 %and, 128
%icmp2 = icmp eq i32 %x, 127
%ret = or i1 %icmp1, %icmp2
ret i1 %ret
}

define i1 @and_icmp_ne_and_pow2_commute(i32 %x) {
; CHECK-LABEL: @and_icmp_ne_and_pow2_commute(
; CHECK-NEXT: [[TMP1:%.*]] = add i32 [[X:%.*]], -160
; CHECK-NEXT: [[RET:%.*]] = icmp ult i32 [[TMP1]], -33
; CHECK-NEXT: ret i1 [[RET]]
;
%and = and i32 %x, -32
%icmp1 = icmp ne i32 %and, 128
%icmp2 = icmp ne i32 %x, 127
%ret = and i1 %icmp1, %icmp2
ret i1 %ret
}

define i1 @neg_or_icmp_eq_and_pow2_multi_use(i32 %x) {
; CHECK-LABEL: @neg_or_icmp_eq_and_pow2_multi_use(
; CHECK-NEXT: [[ICMP1:%.*]] = icmp eq i32 [[X:%.*]], 127
; CHECK-NEXT: [[AND:%.*]] = and i32 [[X]], -32
; CHECK-NEXT: call void @use32(i32 [[AND]])
; CHECK-NEXT: [[ICMP2:%.*]] = icmp eq i32 [[AND]], 128
; CHECK-NEXT: [[RET:%.*]] = or i1 [[ICMP1]], [[ICMP2]]
; CHECK-NEXT: ret i1 [[RET]]
;
%icmp1 = icmp eq i32 %x, 127
%and = and i32 %x, -32
call void @use32(i32 %and)
%icmp2 = icmp eq i32 %and, 128
%ret = or i1 %icmp1, %icmp2
ret i1 %ret
}

define i1 @neg_and_icmp_eq_and_pow2(i32 %x) {
; CHECK-LABEL: @neg_and_icmp_eq_and_pow2(
; CHECK-NEXT: ret i1 false
;
%icmp1 = icmp eq i32 %x, 127
%and = and i32 %x, -32
%icmp2 = icmp eq i32 %and, 128
%ret = and i1 %icmp1, %icmp2
ret i1 %ret
}

define i1 @neg_or_icmp_eq_and_non_pow2_mask(i32 %x) {
; CHECK-LABEL: @neg_or_icmp_eq_and_non_pow2_mask(
; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i32 [[X:%.*]], 127
; CHECK-NEXT: [[TMP2:%.*]] = and i32 [[X]], -33
; CHECK-NEXT: [[TMP3:%.*]] = icmp eq i32 [[TMP2]], 128
; CHECK-NEXT: [[TMP4:%.*]] = or i1 [[TMP1]], [[TMP3]]
; CHECK-NEXT: ret i1 [[TMP4]]
;
%icmp1 = icmp eq i32 %x, 127
%and = and i32 %x, -33
%icmp2 = icmp eq i32 %and, 128
%ret = or i1 %icmp1, %icmp2
ret i1 %ret
}

define i1 @neg_and_icmp_ne_and_non_pow2_icmp(i32 %x) {
; CHECK-LABEL: @neg_and_icmp_ne_and_non_pow2_icmp(
; CHECK-NEXT: [[ICMP1:%.*]] = icmp ne i32 [[X:%.*]], 127
; CHECK-NEXT: [[AND:%.*]] = and i32 [[X]], -33
; CHECK-NEXT: [[ICMP2:%.*]] = icmp ne i32 [[AND]], 128
; CHECK-NEXT: [[RET:%.*]] = and i1 [[ICMP1]], [[ICMP2]]
; CHECK-NEXT: ret i1 [[RET]]
;
%icmp1 = icmp ne i32 %x, 127
%and = and i32 %x, -33
%icmp2 = icmp ne i32 %and, 128
%ret = and i1 %icmp1, %icmp2
ret i1 %ret
}

define i1 @neg_or_icmp_eq_and_const_less_than_mask(i32 %x) {
; CHECK-LABEL: @neg_or_icmp_eq_and_const_less_than_mask(
; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i32 [[X:%.*]], 15
; CHECK-NEXT: ret i1 [[TMP1]]
;
%icmp1 = icmp eq i32 %x, 15
%and = and i32 %x, -32
%icmp2 = icmp eq i32 %and, 16
%ret = or i1 %icmp1, %icmp2
ret i1 %ret
}

define i1 @neg_and_icmp_ne_and_pow2_disjoint(i32 %x) {
; CHECK-LABEL: @neg_and_icmp_ne_and_pow2_disjoint(
; CHECK-NEXT: [[ICMP1:%.*]] = icmp ne i32 [[X:%.*]], 126
; CHECK-NEXT: [[AND:%.*]] = and i32 [[X]], -32
; CHECK-NEXT: [[ICMP2:%.*]] = icmp ne i32 [[AND]], 128
; CHECK-NEXT: [[RET:%.*]] = and i1 [[ICMP1]], [[ICMP2]]
; CHECK-NEXT: ret i1 [[RET]]
;
%icmp1 = icmp ne i32 %x, 126
%and = and i32 %x, -32
%icmp2 = icmp ne i32 %and, 128
%ret = and i1 %icmp1, %icmp2
ret i1 %ret
}

define i1 @neg_or_icmp_eq_double_and_pow2(i32 %x) {
; CHECK-LABEL: @neg_or_icmp_eq_double_and_pow2(
; CHECK-NEXT: [[TMP1:%.*]] = and i32 [[X:%.*]], -16
; CHECK-NEXT: [[TMP2:%.*]] = icmp eq i32 [[TMP1]], 64
; CHECK-NEXT: [[AND2:%.*]] = and i32 [[X]], -32
; CHECK-NEXT: [[TMP4:%.*]] = icmp eq i32 [[AND2]], 128
; CHECK-NEXT: [[TMP5:%.*]] = or i1 [[TMP2]], [[TMP4]]
; CHECK-NEXT: ret i1 [[TMP5]]
;
%and1 = and i32 %x, -16
%icmp1 = icmp eq i32 %and1, 64
%and2 = and i32 %x, -32
%icmp2 = icmp eq i32 %and2, 128
%ret = or i1 %icmp1, %icmp2
ret i1 %ret
}

define i1 @neg_select_icmp_eq_and_pow2(i32 %x) {
; CHECK-LABEL: @neg_select_icmp_eq_and_pow2(
; CHECK-NEXT: [[ICMP1:%.*]] = icmp sgt i32 [[X:%.*]], 127
; CHECK-NEXT: [[AND:%.*]] = and i32 [[X]], -32
; CHECK-NEXT: [[ICMP2:%.*]] = icmp eq i32 [[AND]], 128
; CHECK-NEXT: [[TMP1:%.*]] = and i1 [[ICMP1]], [[ICMP2]]
; CHECK-NEXT: ret i1 [[TMP1]]
;
%icmp1 = icmp sgt i32 %x, 127
%and = and i32 %x, -32
%icmp2 = icmp eq i32 %and, 128
%1 = select i1 %icmp1, i1 %icmp2, i1 false
ret i1 %1
}