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[InstCombine] Fold an unsigned icmp of ucmp/scmp with a constant to an icmp of the original arguments #104471

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Merged
merged 3 commits into from
Aug 16, 2024
Merged

[InstCombine] Fold an unsigned icmp of ucmp/scmp with a constant to an icmp of the original arguments #104471

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3e5bf9c
Precommit tests
Poseydon42 Aug 15, 2024
5792dea
Implement the fold
Poseydon42 Aug 15, 2024
5aea576
Remove unnecessary condition for fold
Poseydon42 Aug 15, 2024
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10 changes: 10 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4018,6 +4018,16 @@ foldICmpOfCmpIntrinsicWithConstant(ICmpInst::Predicate Pred, IntrinsicInst *I,
NewPredicate = ICmpInst::ICMP_ULE;
break;

case ICmpInst::ICMP_ULT:
if (C.ugt(1))
NewPredicate = ICmpInst::ICMP_UGE;
break;

case ICmpInst::ICMP_UGT:
if (!C.isZero() && !C.isAllOnes())
NewPredicate = ICmpInst::ICMP_ULT;
break;

default:
break;
}
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25 changes: 25 additions & 0 deletions llvm/test/Transforms/InstCombine/scmp.ll
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Expand Up @@ -157,6 +157,31 @@ define i1 @scmp_sle_neg_1(i32 %x, i32 %y) {
ret i1 %2
}

; scmp(x, y) u< C => x s>= y when C u> 1 and C != -1
define i1 @scmp_ult_positive_const_gt_than_1_lt_than_umax(i32 %x, i32 %y) {
; CHECK-LABEL: define i1 @scmp_ult_positive_const_gt_than_1_lt_than_umax(
; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
; CHECK-NEXT: [[TMP1:%.*]] = icmp sge i32 [[X]], [[Y]]
; CHECK-NEXT: ret i1 [[TMP1]]
;
%1 = call i8 @llvm.scmp(i32 %x, i32 %y)
%2 = icmp ult i8 %1, 4
ret i1 %2
}

; scmp(x, y) s> C => x s< y when C != 0 and C != -1
define i1 @ucmp_ugt_const_not_0_or_neg1(i32 %x, i32 %y) {
; CHECK-LABEL: define i1 @ucmp_ugt_const_not_0_or_neg1(
; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
; CHECK-NEXT: [[TMP2:%.*]] = icmp slt i32 [[X]], [[Y]]
; CHECK-NEXT: ret i1 [[TMP2]]
;
%1 = call i8 @llvm.scmp(i32 %x, i32 %y)
%2 = icmp ugt i8 %1, 12
ret i1 %2
}


; ========== Fold -scmp(x, y) => scmp(y, x) ==========
define i8 @scmp_negated(i32 %x, i32 %y) {
; CHECK-LABEL: define i8 @scmp_negated(
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24 changes: 24 additions & 0 deletions llvm/test/Transforms/InstCombine/ucmp.ll
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Expand Up @@ -157,6 +157,30 @@ define i1 @ucmp_sle_neg_1(i32 %x, i32 %y) {
ret i1 %2
}

; ucmp(x, y) u< C => x u>= y when C u> 1 and C != -1
define i1 @ucmp_ult_positive_const_gt_than_1_lt_than_umax(i32 %x, i32 %y) {
; CHECK-LABEL: define i1 @ucmp_ult_positive_const_gt_than_1_lt_than_umax(
; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
; CHECK-NEXT: [[TMP1:%.*]] = icmp uge i32 [[X]], [[Y]]
; CHECK-NEXT: ret i1 [[TMP1]]
;
%1 = call i8 @llvm.ucmp(i32 %x, i32 %y)
%2 = icmp ult i8 %1, 4
ret i1 %2
}

; ucmp(x, y) u> C => x u< y when C != 0 and C != -1
define i1 @ucmp_ugt_const_not_0_or_neg1(i32 %x, i32 %y) {
; CHECK-LABEL: define i1 @ucmp_ugt_const_not_0_or_neg1(
; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
; CHECK-NEXT: [[TMP2:%.*]] = icmp ult i32 [[X]], [[Y]]
; CHECK-NEXT: ret i1 [[TMP2]]
;
%1 = call i8 @llvm.ucmp(i32 %x, i32 %y)
%2 = icmp ugt i8 %1, 12
ret i1 %2
}

; ========== Fold -ucmp(x, y) => ucmp(y, x) ==========
define i8 @ucmp_negated(i32 %x, i32 %y) {
; CHECK-LABEL: define i8 @ucmp_negated(
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