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[InstCombine] Convert logical and/or with icmp samesign into bitwise ops #116983

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Nov 21, 2024
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[InstCombine] Convert logical and/or with icmp samesign into bitwise ops #116983

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3dec6fe
[InstCombine] Add pre-commit tests. NFC.
dtcxzyw Nov 20, 2024
25d7b61
[InstCombine] Convert logical and/or with icmp samesign into bitwise ops
dtcxzyw Nov 20, 2024
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41 changes: 37 additions & 4 deletions llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3115,6 +3115,39 @@ static Instruction *foldNestedSelects(SelectInst &OuterSelVal,
!IsAndVariant ? SelInner : InnerSel.FalseVal);
}

/// Return true if V is poison or \p Expected given that ValAssumedPoison is
/// already poison. For example, if ValAssumedPoison is `icmp samesign X, 10`
/// and V is `icmp ne X, 5`, impliesPoisonOrCond returns true.
static bool impliesPoisonOrCond(const Value *ValAssumedPoison, const Value *V,
bool Expected) {
if (impliesPoison(ValAssumedPoison, V))
return true;

// Handle the case that ValAssumedPoison is `icmp samesign pred X, C1` and V
// is `icmp pred X, C2`, where C1 is well-defined.
if (auto *ICmp = dyn_cast<ICmpInst>(ValAssumedPoison)) {
Value *LHS = ICmp->getOperand(0);
const APInt *RHSC1;
const APInt *RHSC2;
ICmpInst::Predicate Pred;
if (ICmp->hasSameSign() &&
match(ICmp->getOperand(1), m_APIntForbidPoison(RHSC1)) &&
match(V, m_ICmp(Pred, m_Specific(LHS), m_APIntAllowPoison(RHSC2)))) {
unsigned BitWidth = RHSC1->getBitWidth();
ConstantRange CRX =
RHSC1->isNonNegative()
? ConstantRange(APInt::getSignedMinValue(BitWidth),
APInt::getZero(BitWidth))
: ConstantRange(APInt::getZero(BitWidth),
APInt::getSignedMinValue(BitWidth));
return CRX.icmp(Expected ? Pred : ICmpInst::getInversePredicate(Pred),
*RHSC2);
}
}

return false;
}

Instruction *InstCombinerImpl::foldSelectOfBools(SelectInst &SI) {
Value *CondVal = SI.getCondition();
Value *TrueVal = SI.getTrueValue();
Expand All @@ -3136,13 +3169,13 @@ Instruction *InstCombinerImpl::foldSelectOfBools(SelectInst &SI) {
// checks whether folding it does not convert a well-defined value into
// poison.
if (match(TrueVal, m_One())) {
if (impliesPoison(FalseVal, CondVal)) {
if (impliesPoisonOrCond(FalseVal, CondVal, /*Expected=*/false)) {
// Change: A = select B, true, C --> A = or B, C
return BinaryOperator::CreateOr(CondVal, FalseVal);
}

if (match(CondVal, m_OneUse(m_Select(m_Value(A), m_One(), m_Value(B)))) &&
impliesPoison(FalseVal, B)) {
impliesPoisonOrCond(FalseVal, B, /*Expected=*/false)) {
// (A || B) || C --> A || (B | C)
return replaceInstUsesWith(
SI, Builder.CreateLogicalOr(A, Builder.CreateOr(B, FalseVal)));
Expand Down Expand Up @@ -3178,13 +3211,13 @@ Instruction *InstCombinerImpl::foldSelectOfBools(SelectInst &SI) {
}

if (match(FalseVal, m_Zero())) {
if (impliesPoison(TrueVal, CondVal)) {
if (impliesPoisonOrCond(TrueVal, CondVal, /*Expected=*/true)) {
// Change: A = select B, C, false --> A = and B, C
return BinaryOperator::CreateAnd(CondVal, TrueVal);
}

if (match(CondVal, m_OneUse(m_Select(m_Value(A), m_Value(B), m_Zero()))) &&
impliesPoison(TrueVal, B)) {
impliesPoisonOrCond(TrueVal, B, /*Expected=*/true)) {
// (A && B) && C --> A && (B & C)
return replaceInstUsesWith(
SI, Builder.CreateLogicalAnd(A, Builder.CreateAnd(B, TrueVal)));
Expand Down
118 changes: 118 additions & 0 deletions llvm/test/Transforms/InstCombine/logical-select.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -1521,3 +1521,121 @@ bb:
%and2 = or i1 %and1, %cmp
ret i1 %and2
}

define i1 @test_logical_and_icmp_samesign(i8 %x) {
; CHECK-LABEL: @test_logical_and_icmp_samesign(
; CHECK-NEXT: [[CMP1:%.*]] = icmp ne i8 [[X:%.*]], 9
; CHECK-NEXT: [[CMP2:%.*]] = icmp samesign ult i8 [[X]], 11
; CHECK-NEXT: [[AND:%.*]] = and i1 [[CMP1]], [[CMP2]]
; CHECK-NEXT: ret i1 [[AND]]
;
%cmp1 = icmp ne i8 %x, 9
%cmp2 = icmp samesign ult i8 %x, 11
%and = select i1 %cmp1, i1 %cmp2, i1 false
ret i1 %and
}

define i1 @test_logical_or_icmp_samesign(i8 %x) {
; CHECK-LABEL: @test_logical_or_icmp_samesign(
; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i8 [[X:%.*]], -9
; CHECK-NEXT: [[CMP2:%.*]] = icmp samesign ult i8 [[X]], -11
; CHECK-NEXT: [[OR:%.*]] = or i1 [[CMP1]], [[CMP2]]
; CHECK-NEXT: ret i1 [[OR]]
;
%cmp1 = icmp eq i8 %x, -9
%cmp2 = icmp samesign ult i8 %x, -11
%or = select i1 %cmp1, i1 true, i1 %cmp2
ret i1 %or
}

define i1 @test_double_logical_and_icmp_samesign1(i1 %cond, i32 %y) {
; CHECK-LABEL: @test_double_logical_and_icmp_samesign1(
; CHECK-NEXT: [[CMP2:%.*]] = icmp samesign ult i32 [[Y:%.*]], 4
; CHECK-NEXT: [[SEL2:%.*]] = select i1 [[SEL1:%.*]], i1 [[CMP2]], i1 false
; CHECK-NEXT: ret i1 [[SEL2]]
;
%cmp1 = icmp ne i32 %y, 5
%sel1 = select i1 %cond, i1 %cmp1, i1 false
%cmp2 = icmp samesign ult i32 %y, 4
%sel2 = select i1 %sel1, i1 %cmp2, i1 false
ret i1 %sel2
}

define i1 @test_double_logical_and_icmp_samesign2(i1 %cond, i32 %y) {
; CHECK-LABEL: @test_double_logical_and_icmp_samesign2(
; CHECK-NEXT: [[TMP1:%.*]] = add i32 [[Y:%.*]], -65536
; CHECK-NEXT: [[CMP2:%.*]] = icmp ult i32 [[TMP1]], 1048576
; CHECK-NEXT: [[SEL2:%.*]] = select i1 [[SEL1:%.*]], i1 [[CMP2]], i1 false
; CHECK-NEXT: ret i1 [[SEL2]]
;
%cmp1 = icmp samesign ugt i32 %y, 65535
%sel1 = select i1 %cond, i1 %cmp1, i1 false
%cmp2 = icmp samesign ult i32 %y, 1114112
%sel2 = select i1 %sel1, i1 %cmp2, i1 false
ret i1 %sel2
}

define <2 x i1> @test_logical_and_icmp_samesign_vec(<2 x i8> %x) {
; CHECK-LABEL: @test_logical_and_icmp_samesign_vec(
; CHECK-NEXT: [[CMP1:%.*]] = icmp ne <2 x i8> [[X:%.*]], splat (i8 9)
; CHECK-NEXT: [[CMP2:%.*]] = icmp samesign ult <2 x i8> [[X]], splat (i8 11)
; CHECK-NEXT: [[AND:%.*]] = and <2 x i1> [[CMP1]], [[CMP2]]
; CHECK-NEXT: ret <2 x i1> [[AND]]
;
%cmp1 = icmp ne <2 x i8> %x, splat(i8 9)
%cmp2 = icmp samesign ult <2 x i8> %x, splat(i8 11)
%and = select <2 x i1> %cmp1, <2 x i1> %cmp2, <2 x i1> zeroinitializer
ret <2 x i1> %and
}

define <2 x i1> @test_logical_and_icmp_samesign_vec_with_poison_cond(<2 x i8> %x) {
; CHECK-LABEL: @test_logical_and_icmp_samesign_vec_with_poison_cond(
; CHECK-NEXT: [[CMP1:%.*]] = icmp ne <2 x i8> [[X:%.*]], <i8 9, i8 poison>
; CHECK-NEXT: [[CMP2:%.*]] = icmp samesign ult <2 x i8> [[X]], splat (i8 11)
; CHECK-NEXT: [[AND:%.*]] = and <2 x i1> [[CMP1]], [[CMP2]]
; CHECK-NEXT: ret <2 x i1> [[AND]]
;
%cmp1 = icmp ne <2 x i8> %x, <i8 9, i8 poison>
%cmp2 = icmp samesign ult <2 x i8> %x, splat(i8 11)
%and = select <2 x i1> %cmp1, <2 x i1> %cmp2, <2 x i1> zeroinitializer
ret <2 x i1> %and
}

define i1 @test_logical_and_icmp_samesign_do_not_imply(i8 %x) {
; CHECK-LABEL: @test_logical_and_icmp_samesign_do_not_imply(
; CHECK-NEXT: [[AND:%.*]] = icmp ult i8 [[X:%.*]], 11
; CHECK-NEXT: ret i1 [[AND]]
;
%cmp1 = icmp ne i8 %x, -9
%cmp2 = icmp samesign ult i8 %x, 11
%and = select i1 %cmp1, i1 %cmp2, i1 false
ret i1 %and
}

define i1 @test_logical_and_icmp_no_samesign(i8 %x) {
; CHECK-LABEL: @test_logical_and_icmp_no_samesign(
; CHECK-NEXT: [[CMP1:%.*]] = icmp ne i8 [[X:%.*]], 9
; CHECK-NEXT: [[CMP2:%.*]] = icmp ult i8 [[X]], 11
; CHECK-NEXT: [[AND:%.*]] = and i1 [[CMP1]], [[CMP2]]
; CHECK-NEXT: ret i1 [[AND]]
;
%cmp1 = icmp ne i8 %x, 9
%cmp2 = icmp ult i8 %x, 11
%and = select i1 %cmp1, i1 %cmp2, i1 false
ret i1 %and
}

; Negative tests

define <2 x i1> @test_logical_and_icmp_samesign_vec_with_poison_tv(<2 x i8> %x) {
; CHECK-LABEL: @test_logical_and_icmp_samesign_vec_with_poison_tv(
; CHECK-NEXT: [[CMP1:%.*]] = icmp ne <2 x i8> [[X:%.*]], splat (i8 9)
; CHECK-NEXT: [[CMP2:%.*]] = icmp samesign ult <2 x i8> [[X]], <i8 11, i8 poison>
; CHECK-NEXT: [[AND:%.*]] = select <2 x i1> [[CMP1]], <2 x i1> [[CMP2]], <2 x i1> zeroinitializer
; CHECK-NEXT: ret <2 x i1> [[AND]]
;
%cmp1 = icmp ne <2 x i8> %x, splat(i8 9)
%cmp2 = icmp samesign ult <2 x i8> %x, <i8 11, i8 poison>
%and = select <2 x i1> %cmp1, <2 x i1> %cmp2, <2 x i1> zeroinitializer
ret <2 x i1> %and
}
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