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[InstCombine] Teach foldSelectOpOp about samesign #122723

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Jan 14, 2025
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[InstCombine] Teach foldSelectOpOp about samesign #122723

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88a2db3
IC: pre-commit tests for samesign-getMatching
artagnon Jan 13, 2025
31c638d
IC: teach foldSelectOpOp about samesign
artagnon Jan 13, 2025
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8 changes: 4 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 @@ -428,10 +428,10 @@ Instruction *InstCombinerImpl::foldSelectOpOp(SelectInst &SI, Instruction *TI,
CmpPredicate TPred, FPred;
if (match(TI, m_ICmp(TPred, m_Value(), m_Value())) &&
match(FI, m_ICmp(FPred, m_Value(), m_Value()))) {
// FIXME: Use CmpPredicate::getMatching here.
CmpInst::Predicate T = TPred, F = FPred;
if (T == F || T == ICmpInst::getSwappedCmpPredicate(F)) {
bool Swapped = T != F;
bool Swapped = ICmpInst::isRelational(FPred) &&
CmpPredicate::getMatching(
TPred, ICmpInst::getSwappedCmpPredicate(FPred));
if (CmpPredicate::getMatching(TPred, FPred) || Swapped) {
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We use TPred below, instead of the matching predicate. Sorry for missing this obvious bug :(

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Thanks a lot for the investigation and test case: I was sick over the last few days, and couldn't do it myself :(
Will post a re-land shortly.

if (Value *MatchOp =
getCommonOp(TI, FI, ICmpInst::isEquality(TPred), Swapped)) {
Value *NewSel = Builder.CreateSelect(Cond, OtherOpT, OtherOpF,
Expand Down
96 changes: 96 additions & 0 deletions llvm/test/Transforms/InstCombine/select-cmp.ll
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Expand Up @@ -23,6 +23,18 @@ define i1 @icmp_ne_common_op00(i1 %c, i6 %x, i6 %y, i6 %z) {
ret i1 %r
}

define i1 @icmp_ne_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_ne_samesign_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp ne i6 [[X:%.*]], [[R_V]]
; CHECK-NEXT: ret i1 [[R]]
;
%cmp1 = icmp samesign ne i6 %x, %y
%cmp2 = icmp ne i6 %x, %z
%r = select i1 %c, i1 %cmp1, i1 %cmp2
ret i1 %r
}

define i1 @icmp_ne_common_op01(i1 %c, i3 %x, i3 %y, i3 %z) {
; CHECK-LABEL: @icmp_ne_common_op01(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i3 [[Y:%.*]], i3 [[Z:%.*]]
Expand Down Expand Up @@ -71,6 +83,18 @@ define i1 @icmp_eq_common_op00(i1 %c, i5 %x, i5 %y, i5 %z) {
ret i1 %r
}

define i1 @icmp_eq_samesign_common(i1 %c, i5 %x, i5 %y, i5 %z) {
; CHECK-LABEL: @icmp_eq_samesign_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i5 [[Y:%.*]], i5 [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp eq i5 [[X:%.*]], [[R_V]]
; CHECK-NEXT: ret i1 [[R]]
;
%cmp1 = icmp eq i5 %x, %y
%cmp2 = icmp samesign eq i5 %x, %z
%r = select i1 %c, i1 %cmp1, i1 %cmp2
ret i1 %r
}

define <5 x i1> @icmp_eq_common_op01(<5 x i1> %c, <5 x i7> %x, <5 x i7> %y, <5 x i7> %z) {
; CHECK-LABEL: @icmp_eq_common_op01(
; CHECK-NEXT: [[R_V:%.*]] = select <5 x i1> [[C:%.*]], <5 x i7> [[Y:%.*]], <5 x i7> [[Z:%.*]]
Expand Down Expand Up @@ -134,6 +158,18 @@ define i1 @icmp_slt_common(i1 %c, i6 %x, i6 %y, i6 %z) {
ret i1 %r
}

define i1 @icmp_slt_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_slt_samesign_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp ult i6 [[X:%.*]], [[R_V]]
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The bug is also visible in this test case.

; CHECK-NEXT: ret i1 [[R]]
;
%cmp1 = icmp samesign ult i6 %x, %y
%cmp2 = icmp slt i6 %x, %z
%r = select i1 %c, i1 %cmp1, i1 %cmp2
ret i1 %r
}

define i1 @icmp_sgt_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_sgt_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
Expand All @@ -146,6 +182,18 @@ define i1 @icmp_sgt_common(i1 %c, i6 %x, i6 %y, i6 %z) {
ret i1 %r
}

define i1 @icmp_sgt_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_sgt_samesign_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp ugt i6 [[X:%.*]], [[R_V]]
; CHECK-NEXT: ret i1 [[R]]
;
%cmp1 = icmp samesign ugt i6 %x, %y
%cmp2 = icmp sgt i6 %x, %z
%r = select i1 %c, i1 %cmp1, i1 %cmp2
ret i1 %r
}

define i1 @icmp_sle_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_sle_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
Expand All @@ -158,6 +206,18 @@ define i1 @icmp_sle_common(i1 %c, i6 %x, i6 %y, i6 %z) {
ret i1 %r
}

define i1 @icmp_sle_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_sle_samesign_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp sge i6 [[X:%.*]], [[R_V]]
; CHECK-NEXT: ret i1 [[R]]
;
%cmp1 = icmp sle i6 %y, %x
%cmp2 = icmp samesign ule i6 %z, %x
%r = select i1 %c, i1 %cmp1, i1 %cmp2
ret i1 %r
}

define i1 @icmp_sge_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_sge_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
Expand All @@ -170,6 +230,18 @@ define i1 @icmp_sge_common(i1 %c, i6 %x, i6 %y, i6 %z) {
ret i1 %r
}

define i1 @icmp_sge_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_sge_samesign_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp sle i6 [[X:%.*]], [[R_V]]
; CHECK-NEXT: ret i1 [[R]]
;
%cmp1 = icmp sge i6 %y, %x
%cmp2 = icmp samesign uge i6 %z, %x
%r = select i1 %c, i1 %cmp1, i1 %cmp2
ret i1 %r
}

define i1 @icmp_slt_sgt_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_slt_sgt_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
Expand All @@ -182,6 +254,18 @@ define i1 @icmp_slt_sgt_common(i1 %c, i6 %x, i6 %y, i6 %z) {
ret i1 %r
}

define i1 @icmp_slt_sgt_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_slt_sgt_samesign_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp ult i6 [[X:%.*]], [[R_V]]
; CHECK-NEXT: ret i1 [[R]]
;
%cmp1 = icmp samesign ult i6 %x, %y
%cmp2 = icmp sgt i6 %z, %x
%r = select i1 %c, i1 %cmp1, i1 %cmp2
ret i1 %r
}

define i1 @icmp_sle_sge_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_sle_sge_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
Expand All @@ -194,6 +278,18 @@ define i1 @icmp_sle_sge_common(i1 %c, i6 %x, i6 %y, i6 %z) {
ret i1 %r
}

define i1 @icmp_sle_sge_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_sle_sge_samesign_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp sge i6 [[X:%.*]], [[R_V]]
; CHECK-NEXT: ret i1 [[R]]
;
%cmp1 = icmp sle i6 %y, %x
%cmp2 = icmp samesign uge i6 %x, %z
%r = select i1 %c, i1 %cmp1, i1 %cmp2
ret i1 %r
}

define i1 @icmp_ult_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_ult_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
Expand Down
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