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[InstCombine] smin(smax(X, -1), 1) -> scmp(X, 0) and smax(smin(X, 1), -1) -> scmp(X, 0) #145736

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[InstCombine] smin(smax(X, -1), 1) -> scmp(X, 0) and smax(smin(X, 1), -1) -> scmp(X, 0) #145736

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b16eb26
[InstCombine] Pre-commit tests (NFC)
AZero13 Jun 25, 2025
a876476
[InstCombine] smin(smax(X, -1), 1) -> scmp(X, 0) and smax(smin(X, 1),…
AZero13 Jun 25, 2025
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15 changes: 15 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1972,6 +1972,21 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
return BinaryOperator::CreateOr(I0, I1);
}

// smin(smax(X, -1), 1) -> scmp(X, 0)
// smax(smin(X, 1), -1) -> scmp(X, 0)
// At this point, smax(smin(X, 1), -1) is changed to smin(smax(X, -1)
// And i1's have been changed to and/ors
// So we only need to check for smin
if (IID == Intrinsic::smin) {
if (match(I0, m_OneUse(m_SMax(m_Value(X), m_AllOnes()))) &&
match(I1, m_One())) {
Value *Zero = ConstantInt::get(X->getType(), 0);
return replaceInstUsesWith(
CI,
Builder.CreateIntrinsic(II->getType(), Intrinsic::scmp, {X, Zero}));
}
}

if (IID == Intrinsic::smax || IID == Intrinsic::smin) {
// smax (neg nsw X), (neg nsw Y) --> neg nsw (smin X, Y)
// smin (neg nsw X), (neg nsw Y) --> neg nsw (smax X, Y)
Expand Down
114 changes: 93 additions & 21 deletions llvm/test/Transforms/InstCombine/compare-3way.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@

declare void @use(i32)

; These 18 exercise all combinations of signed comparison
; These exercise all combinations of signed comparison
; for each of the three values produced by your typical
; 3way compare function (-1, 0, 1)

Expand Down Expand Up @@ -81,8 +81,8 @@ unreached:
define void @test_low_sle(i64 %a, i64 %b) {
; CHECK-LABEL: define void @test_low_sle
; CHECK-SAME: (i64 [[A:%.*]], i64 [[B:%.*]]) {
; CHECK-NEXT: [[TMP1:%.*]] = icmp slt i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[TMP1]], label [[UNREACHED:%.*]], label [[NORMAL:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[CMP]], label [[UNREACHED:%.*]], label [[NORMAL:%.*]]
; CHECK: normal:
; CHECK-NEXT: ret void
; CHECK: unreached:
Expand All @@ -105,8 +105,8 @@ unreached:
define void @test_low_ne(i64 %a, i64 %b) {
; CHECK-LABEL: define void @test_low_ne
; CHECK-SAME: (i64 [[A:%.*]], i64 [[B:%.*]]) {
; CHECK-NEXT: [[TMP1:%.*]] = icmp slt i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[TMP1]], label [[NORMAL:%.*]], label [[UNREACHED:%.*]]
; CHECK-NEXT: [[CMP_NOT:%.*]] = icmp slt i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[CMP_NOT]], label [[NORMAL:%.*]], label [[UNREACHED:%.*]]
; CHECK: normal:
; CHECK-NEXT: ret void
; CHECK: unreached:
Expand All @@ -130,8 +130,8 @@ unreached:
define void @test_low_eq(i64 %a, i64 %b) {
; CHECK-LABEL: define void @test_low_eq
; CHECK-SAME: (i64 [[A:%.*]], i64 [[B:%.*]]) {
; CHECK-NEXT: [[TMP1:%.*]] = icmp slt i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[TMP1]], label [[UNREACHED:%.*]], label [[NORMAL:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[CMP]], label [[UNREACHED:%.*]], label [[NORMAL:%.*]]
; CHECK: normal:
; CHECK-NEXT: ret void
; CHECK: unreached:
Expand All @@ -154,8 +154,8 @@ unreached:
define void @test_mid_sgt(i64 %a, i64 %b) {
; CHECK-LABEL: define void @test_mid_sgt
; CHECK-SAME: (i64 [[A:%.*]], i64 [[B:%.*]]) {
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[TMP1]], label [[UNREACHED:%.*]], label [[NORMAL:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[CMP]], label [[UNREACHED:%.*]], label [[NORMAL:%.*]]
; CHECK: normal:
; CHECK-NEXT: ret void
; CHECK: unreached:
Expand All @@ -178,8 +178,8 @@ unreached:
define void @test_mid_slt(i64 %a, i64 %b) {
; CHECK-LABEL: define void @test_mid_slt
; CHECK-SAME: (i64 [[A:%.*]], i64 [[B:%.*]]) {
; CHECK-NEXT: [[TMP1:%.*]] = icmp slt i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[TMP1]], label [[UNREACHED:%.*]], label [[NORMAL:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[CMP]], label [[UNREACHED:%.*]], label [[NORMAL:%.*]]
; CHECK: normal:
; CHECK-NEXT: ret void
; CHECK: unreached:
Expand Down Expand Up @@ -252,8 +252,8 @@ unreached:
define void @test_mid_ne(i64 %a, i64 %b) {
; CHECK-LABEL: define void @test_mid_ne
; CHECK-SAME: (i64 [[A:%.*]], i64 [[B:%.*]]) {
; CHECK-NEXT: [[EQ:%.*]] = icmp eq i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[EQ]], label [[NORMAL:%.*]], label [[UNREACHED:%.*]]
; CHECK-NEXT: [[CMP_NOT:%.*]] = icmp eq i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[CMP_NOT]], label [[NORMAL:%.*]], label [[UNREACHED:%.*]]
; CHECK: normal:
; CHECK-NEXT: ret void
; CHECK: unreached:
Expand All @@ -277,8 +277,8 @@ unreached:
define void @test_mid_eq(i64 %a, i64 %b) {
; CHECK-LABEL: define void @test_mid_eq
; CHECK-SAME: (i64 [[A:%.*]], i64 [[B:%.*]]) {
; CHECK-NEXT: [[EQ:%.*]] = icmp eq i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[EQ]], label [[UNREACHED:%.*]], label [[NORMAL:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[CMP]], label [[UNREACHED:%.*]], label [[NORMAL:%.*]]
; CHECK: normal:
; CHECK-NEXT: ret void
; CHECK: unreached:
Expand Down Expand Up @@ -348,8 +348,8 @@ unreached:
define void @test_high_sge(i64 %a, i64 %b) {
; CHECK-LABEL: define void @test_high_sge
; CHECK-SAME: (i64 [[A:%.*]], i64 [[B:%.*]]) {
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[TMP1]], label [[UNREACHED:%.*]], label [[NORMAL:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[CMP]], label [[UNREACHED:%.*]], label [[NORMAL:%.*]]
; CHECK: normal:
; CHECK-NEXT: ret void
; CHECK: unreached:
Expand Down Expand Up @@ -396,8 +396,8 @@ unreached:
define void @test_high_ne(i64 %a, i64 %b) {
; CHECK-LABEL: define void @test_high_ne
; CHECK-SAME: (i64 [[A:%.*]], i64 [[B:%.*]]) {
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[TMP1]], label [[NORMAL:%.*]], label [[UNREACHED:%.*]]
; CHECK-NEXT: [[CMP_NOT:%.*]] = icmp sgt i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[CMP_NOT]], label [[NORMAL:%.*]], label [[UNREACHED:%.*]]
; CHECK: normal:
; CHECK-NEXT: ret void
; CHECK: unreached:
Expand All @@ -421,8 +421,8 @@ unreached:
define void @test_high_eq(i64 %a, i64 %b) {
; CHECK-LABEL: define void @test_high_eq
; CHECK-SAME: (i64 [[A:%.*]], i64 [[B:%.*]]) {
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[TMP1]], label [[UNREACHED:%.*]], label [[NORMAL:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i64 [[A]], [[B]]
; CHECK-NEXT: br i1 [[CMP]], label [[UNREACHED:%.*]], label [[NORMAL:%.*]]
; CHECK: normal:
; CHECK-NEXT: ret void
; CHECK: unreached:
Expand Down Expand Up @@ -560,3 +560,75 @@ unreached:
call void @use(i32 %result)
ret void
}

define i32 @smax_smin_to_scmp(i32 %x) {
; CHECK-LABEL: define i32 @smax_smin_to_scmp
; CHECK-SAME: (i32 [[X:%.*]]) {
; CHECK-NEXT: [[COND5:%.*]] = call i32 @llvm.scmp.i32.i32(i32 [[X]], i32 0)
; CHECK-NEXT: ret i32 [[COND5]]
;
%cond = call i32 @llvm.smax.i32(i32 %x, i32 -1)
%cond5 = call i32 @llvm.smin.i32(i32 %cond, i32 1)
ret i32 %cond5
}

define i16 @smax_smin_to_scmp_i16(i16 %x) {
; CHECK-LABEL: define i16 @smax_smin_to_scmp_i16
; CHECK-SAME: (i16 [[X:%.*]]) {
; CHECK-NEXT: [[COND5:%.*]] = call i16 @llvm.scmp.i16.i16(i16 [[X]], i16 0)
; CHECK-NEXT: ret i16 [[COND5]]
;
%cond = call i16 @llvm.smax.i16(i16 %x, i16 -1)
%cond5 = call i16 @llvm.smin.i16(i16 %cond, i16 1)
ret i16 %cond5
}

; Test the reversed pattern: smax(smin(X, 1), -1) -> scmp(X, 0)
define i32 @smin_smax_to_scmp(i32 %x) {
; CHECK-LABEL: define i32 @smin_smax_to_scmp
; CHECK-SAME: (i32 [[X:%.*]]) {
; CHECK-NEXT: [[COND5:%.*]] = call i32 @llvm.scmp.i32.i32(i32 [[X]], i32 0)
; CHECK-NEXT: ret i32 [[COND5]]
;
%cond = call i32 @llvm.smin.i32(i32 %x, i32 1)
%cond5 = call i32 @llvm.smax.i32(i32 %cond, i32 -1)
ret i32 %cond5
}

define i32 @test_max_min_neg(i32 %x) {
; CHECK-LABEL: define i32 @test_max_min_neg
; CHECK-SAME: (i32 [[X:%.*]]) {
; CHECK-NEXT: [[COND:%.*]] = call i32 @llvm.smax.i32(i32 [[X]], i32 -2)
; CHECK-NEXT: [[COND5:%.*]] = call i32 @llvm.smin.i32(i32 [[COND]], i32 1)
; CHECK-NEXT: ret i32 [[COND5]]
;
%cond = call i32 @llvm.smax.i32(i32 %x, i32 -2)
%cond5 = call i32 @llvm.smin.i32(i32 %cond, i32 1)
ret i32 %cond5
}

define i32 @test_max_min_neg_2(i32 %x) {
; CHECK-LABEL: define i32 @test_max_min_neg_2
; CHECK-SAME: (i32 [[X:%.*]]) {
; CHECK-NEXT: [[COND:%.*]] = call i32 @llvm.smax.i32(i32 [[X]], i32 -1)
; CHECK-NEXT: [[COND5:%.*]] = call i32 @llvm.smin.i32(i32 [[COND]], i32 2)
; CHECK-NEXT: ret i32 [[COND5]]
;
%cond = call i32 @llvm.smax.i32(i32 %x, i32 -1)
%cond5 = call i32 @llvm.smin.i32(i32 %cond, i32 2)
ret i32 %cond5
}

define i32 @test_multiple_uses(i32 %x) {
; CHECK-LABEL: define i32 @test_multiple_uses
; CHECK-SAME: (i32 [[X:%.*]]) {
; CHECK-NEXT: [[COND:%.*]] = call i32 @llvm.smax.i32(i32 [[X]], i32 -1)
; CHECK-NEXT: [[COND5:%.*]] = call i32 @llvm.smin.i32(i32 [[COND]], i32 1)
; CHECK-NEXT: [[SUM:%.*]] = add i32 [[COND]], [[COND5]]
; CHECK-NEXT: ret i32 [[SUM]]
;
%cond = call i32 @llvm.smax.i32(i32 %x, i32 -1)
%cond5 = call i32 @llvm.smin.i32(i32 %cond, i32 1)
%sum = add i32 %cond, %cond5
ret i32 %sum
}