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[InstCombine] fold icmp + select pattern by distributive laws
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`C ? (Y != X) : (Z != X) --> (C ? Y : Z) != X`
`C ? (Y == X) : (Z == X) --> (C ? Y : Z) == X`

https://alive2.llvm.org/ce/z/-frXfs

Reviewed By: spatel

Differential Revision: https://reviews.llvm.org/D139076
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@bcl5980
bcl5980 committed Dec 2, 2022
1 parent 7cf5581 commit e719550
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Showing 2 changed files with 32 additions and 26 deletions.
14 changes: 14 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
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Expand Up @@ -378,6 +378,20 @@ Instruction *InstCombinerImpl::foldSelectOpOp(SelectInst &SI, Instruction *TI,
}
}
}

// icmp eq/ne with a common operand also can have the common operand
// pulled after the select.
ICmpInst::Predicate TPred, FPred;
if (match(TI, m_ICmp(TPred, m_Value(), m_Value())) &&
match(FI, m_ICmp(FPred, m_Value(), m_Value()))) {
if (TPred == FPred && ICmpInst::isEquality(TPred)) {
if (Value *MatchOp = getCommonOp(TI, FI, true)) {
Value *NewSel = Builder.CreateSelect(Cond, OtherOpT, OtherOpF,
SI.getName() + ".v", &SI);
return new ICmpInst(TPred, NewSel, MatchOp);
}
}
}
}

// Only handle binary operators (including two-operand getelementptr) with
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44 changes: 18 additions & 26 deletions llvm/test/Transforms/InstCombine/select-cmp.ll
View file
Expand Up @@ -13,9 +13,8 @@ define i1 @f(i1 %cond, i32 %x, i32 %x2) {

define i1 @icmp_ne_common_op00(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_ne_common_op00(
; CHECK-NEXT: [[CMP1:%.*]] = icmp ne i6 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp ne i6 [[X]], [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = select i1 [[C:%.*]], i1 [[CMP1]], i1 [[CMP2]]
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp ne i6 [[R_V]], [[X:%.*]]
; CHECK-NEXT: ret i1 [[R]]
;
%cmp1 = icmp ne i6 %x, %y
Expand All @@ -26,9 +25,8 @@ define i1 @icmp_ne_common_op00(i1 %c, i6 %x, i6 %y, i6 %z) {

define i1 @icmp_ne_common_op01(i1 %c, i3 %x, i3 %y, i3 %z) {
; CHECK-LABEL: @icmp_ne_common_op01(
; CHECK-NEXT: [[CMP1:%.*]] = icmp ne i3 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp ne i3 [[Z:%.*]], [[X]]
; CHECK-NEXT: [[R:%.*]] = select i1 [[C:%.*]], i1 [[CMP1]], i1 [[CMP2]]
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i3 [[Y:%.*]], i3 [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp ne i3 [[R_V]], [[X:%.*]]
; CHECK-NEXT: ret i1 [[R]]
;
%cmp1 = icmp ne i3 %x, %y
Expand All @@ -39,9 +37,8 @@ define i1 @icmp_ne_common_op01(i1 %c, i3 %x, i3 %y, i3 %z) {

define i1 @icmp_ne_common_op10(i1 %c, i4 %x, i4 %y, i4 %z) {
; CHECK-LABEL: @icmp_ne_common_op10(
; CHECK-NEXT: [[CMP1:%.*]] = icmp ne i4 [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp ne i4 [[X]], [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = select i1 [[C:%.*]], i1 [[CMP1]], i1 [[CMP2]]
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i4 [[Y:%.*]], i4 [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp ne i4 [[R_V]], [[X:%.*]]
; CHECK-NEXT: ret i1 [[R]]
;
%cmp1 = icmp ne i4 %y, %x
Expand All @@ -52,9 +49,8 @@ define i1 @icmp_ne_common_op10(i1 %c, i4 %x, i4 %y, i4 %z) {

define <3 x i1> @icmp_ne_common_op11(<3 x i1> %c, <3 x i17> %x, <3 x i17> %y, <3 x i17> %z) {
; CHECK-LABEL: @icmp_ne_common_op11(
; CHECK-NEXT: [[CMP1:%.*]] = icmp ne <3 x i17> [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp ne <3 x i17> [[Z:%.*]], [[X]]
; CHECK-NEXT: [[R:%.*]] = select <3 x i1> [[C:%.*]], <3 x i1> [[CMP1]], <3 x i1> [[CMP2]]
; CHECK-NEXT: [[R_V:%.*]] = select <3 x i1> [[C:%.*]], <3 x i17> [[Y:%.*]], <3 x i17> [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp ne <3 x i17> [[R_V]], [[X:%.*]]
; CHECK-NEXT: ret <3 x i1> [[R]]
;
%cmp1 = icmp ne <3 x i17> %y, %x
Expand All @@ -65,9 +61,8 @@ define <3 x i1> @icmp_ne_common_op11(<3 x i1> %c, <3 x i17> %x, <3 x i17> %y, <3

define i1 @icmp_eq_common_op00(i1 %c, i5 %x, i5 %y, i5 %z) {
; CHECK-LABEL: @icmp_eq_common_op00(
; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i5 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i5 [[X]], [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = select i1 [[C:%.*]], i1 [[CMP1]], i1 [[CMP2]]
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i5 [[Y:%.*]], i5 [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp eq i5 [[R_V]], [[X:%.*]]
; CHECK-NEXT: ret i1 [[R]]
;
%cmp1 = icmp eq i5 %x, %y
Expand All @@ -78,9 +73,8 @@ define i1 @icmp_eq_common_op00(i1 %c, i5 %x, i5 %y, i5 %z) {

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: [[CMP1:%.*]] = icmp eq <5 x i7> [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp eq <5 x i7> [[Z:%.*]], [[X]]
; CHECK-NEXT: [[R:%.*]] = select <5 x i1> [[C:%.*]], <5 x i1> [[CMP1]], <5 x i1> [[CMP2]]
; CHECK-NEXT: [[R_V:%.*]] = select <5 x i1> [[C:%.*]], <5 x i7> [[Y:%.*]], <5 x i7> [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp eq <5 x i7> [[R_V]], [[X:%.*]]
; CHECK-NEXT: ret <5 x i1> [[R]]
;
%cmp1 = icmp eq <5 x i7> %x, %y
Expand All @@ -91,9 +85,8 @@ define <5 x i1> @icmp_eq_common_op01(<5 x i1> %c, <5 x i7> %x, <5 x i7> %y, <5 x

define i1 @icmp_eq_common_op10(i1 %c, i32 %x, i32 %y, i32 %z) {
; CHECK-LABEL: @icmp_eq_common_op10(
; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i32 [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i32 [[X]], [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = select i1 [[C:%.*]], i1 [[CMP1]], i1 [[CMP2]]
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i32 [[Y:%.*]], i32 [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp eq i32 [[R_V]], [[X:%.*]]
; CHECK-NEXT: ret i1 [[R]]
;
%cmp1 = icmp eq i32 %y, %x
Expand All @@ -104,9 +97,8 @@ define i1 @icmp_eq_common_op10(i1 %c, i32 %x, i32 %y, i32 %z) {

define i1 @icmp_eq_common_op11(i1 %c, i64 %x, i64 %y, i64 %z) {
; CHECK-LABEL: @icmp_eq_common_op11(
; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i64 [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i64 [[Z:%.*]], [[X]]
; CHECK-NEXT: [[R:%.*]] = select i1 [[C:%.*]], i1 [[CMP1]], i1 [[CMP2]]
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i64 [[Y:%.*]], i64 [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp eq i64 [[R_V]], [[X:%.*]]
; CHECK-NEXT: ret i1 [[R]]
;
%cmp1 = icmp eq i64 %y, %x
Expand All @@ -119,8 +111,8 @@ define i1 @icmp_common_one_use_1(i1 %c, i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @icmp_common_one_use_1(
; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i8 [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: call void @use(i1 [[CMP1]])
; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i8 [[Z:%.*]], [[X]]
; CHECK-NEXT: [[R:%.*]] = select i1 [[C:%.*]], i1 [[CMP1]], i1 [[CMP2]]
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i8 [[Y]], i8 [[Z:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[R_V]], [[X]]
; CHECK-NEXT: ret i1 [[R]]
;
%cmp1 = icmp eq i8 %y, %x
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