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[InstCombine] fold icmp of select with constants and invertible op #147182

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[InstCombine] fold icmp of select with constants and invertible op #147182

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65c071f
[Precommit] fold icmp of select with constants and invertible op
Acthinks Jul 5, 2025
e633e7e
[InstCombine] fold icmp of select with constants and invertible op
Acthinks Jul 4, 2025
528aa2b
get the right Pred
Acthinks Jul 6, 2025
bca4a72
use foldICmpEqualityWithOffset
Acthinks Jul 10, 2025
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8 changes: 8 additions & 0 deletions llvm/lib/Analysis/InstructionSimplify.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2557,6 +2557,14 @@ static Value *simplifyXorInst(Value *Op0, Value *Op1, const SimplifyQuery &Q,
return X;
}

// (xor (or disjoint X, Y), Y) -> X
{
Value *X;
if (match(Op0, m_c_DisjointOr(m_Value(X), m_Specific(Op1))) ||
match(Op1, m_c_DisjointOr(m_Value(X), m_Specific(Op0))))
return X;
}

return nullptr;
}

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18 changes: 18 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
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Expand Up @@ -5866,6 +5866,24 @@ static void collectOffsetOp(Value *V, SmallVectorImpl<OffsetOp> &Offsets,
Offsets.emplace_back(Instruction::Xor, Inst->getOperand(1));
Offsets.emplace_back(Instruction::Xor, Inst->getOperand(0));
break;
case Instruction::Or:
if (cast<PossiblyDisjointInst>(Inst)->isDisjoint())
Offsets.emplace_back(Instruction::Xor, Inst->getOperand(1));
Offsets.emplace_back(Instruction::Xor, Inst->getOperand(0));
break;
case Instruction::Shl:
if (auto *OBO = cast<OverflowingBinaryOperator>(Inst)) {
if (OBO->hasNoSignedWrap())
Offsets.emplace_back(Instruction::AShr, Inst->getOperand(1));
else if (OBO->hasNoUnsignedWrap())
Offsets.emplace_back(Instruction::LShr, Inst->getOperand(1));
}
break;
case Instruction::AShr:
case Instruction::LShr:
if (auto *PEO = cast<PossiblyExactOperator>(Inst); PEO && PEO->isExact())
Offsets.emplace_back(Instruction::Shl, Inst->getOperand(1));
break;
case Instruction::Select:
if (AllowRecursion) {
collectOffsetOp(Inst->getOperand(1), Offsets, /*AllowRecursion=*/false);
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60 changes: 60 additions & 0 deletions llvm/test/Transforms/InstCombine/icmp-select.ll
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Expand Up @@ -836,3 +836,63 @@ define i1 @discr_eq_constantexpr(ptr %p) {
%cmp = icmp eq i64 %sub, -1
ret i1 %cmp
}

define i1 @or_disjoint_eq(i8 %a, i1 %cond) {
; CHECK-LABEL: @or_disjoint_eq(
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[COND:%.*]], i8 8, i8 4
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[A:%.*]], [[TMP1]]
; CHECK-NEXT: ret i1 [[CMP]]
;
%or = or disjoint i8 %a, 3
%sel = select i1 %cond, i8 11, i8 7
%cmp = icmp eq i8 %or, %sel
ret i1 %cmp
}

define i1 @shl_nsw_eq(i8 %a, i1 %cond) {
; CHECK-LABEL: @shl_nsw_eq(
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[COND:%.*]], i8 1, i8 2
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[A:%.*]], [[TMP1]]
; CHECK-NEXT: ret i1 [[CMP]]
;
%a_shl = shl nsw i8 %a, 3
%sel = select i1 %cond, i8 8, i8 16
%cmp = icmp eq i8 %a_shl, %sel
ret i1 %cmp
}

define i1 @shl_nuw_eq(i8 %a, i1 %cond) {
; CHECK-LABEL: @shl_nuw_eq(
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[COND:%.*]], i8 1, i8 4
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[A:%.*]], [[TMP1]]
; CHECK-NEXT: ret i1 [[CMP]]
;
%a_shl = shl nuw i8 %a, 3
%sel = select i1 %cond, i8 8, i8 32
%cmp = icmp eq i8 %a_shl, %sel
ret i1 %cmp
}

define i1 @ashr_exact_eq(i8 %a, i1 %cond) {
; CHECK-LABEL: @ashr_exact_eq(
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[COND:%.*]], i8 48, i8 16
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[A:%.*]], [[TMP1]]
; CHECK-NEXT: ret i1 [[CMP]]
;
%a_shl = ashr exact i8 %a, 2
%sel = select i1 %cond, i8 12, i8 4
%cmp = icmp eq i8 %a_shl, %sel
ret i1 %cmp
}

define i1 @lshr_exact_eq(i8 %a, i1 %cond) {
; CHECK-LABEL: @lshr_exact_eq(
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[COND:%.*]], i8 48, i8 16
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[A:%.*]], [[TMP1]]
; CHECK-NEXT: ret i1 [[CMP]]
;
%a_shl = lshr exact i8 %a, 2
%sel = select i1 %cond, i8 12, i8 4
%cmp = icmp eq i8 %a_shl, %sel
ret i1 %cmp
}
18 changes: 18 additions & 0 deletions llvm/test/Transforms/InstSimplify/xor.ll
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Expand Up @@ -301,3 +301,21 @@ define <2 x i4> @xor_or_and_not_poison_elt(<2 x i4> %a, <2 x i4> %b) {
%r = xor <2 x i4> %or, %and
ret <2 x i4> %r
}

define i8 @xor_or_disjoint(i8 %a, i8 %b) {
; CHECK-LABEL: @xor_or_disjoint(
; CHECK-NEXT: ret i8 [[B:%.*]]
;
%or = or disjoint i8 %a, %b
%xor = xor i8 %or, %a
ret i8 %xor
}

define i8 @xor_or_disjoint_c(i8 %a, i8 %b) {
; CHECK-LABEL: @xor_or_disjoint_c(
; CHECK-NEXT: ret i8 [[B:%.*]]
;
%or = or disjoint i8 %b, %a
%xor = xor i8 %a, %or
ret i8 %xor
}
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