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[InstCombine] Fold sub of umin to usub.sat 

We were handling sub of umax, but not the conjugated umin case.

https://alive2.llvm.org/ce/z/4fdZfy
https://alive2.llvm.org/ce/z/BhUQBM
This commit is contained in:
Nikita Popov 2022-02-23 11:56:34 +01:00
parent 4b5261e10f
commit e2f627e5e3
2 changed files with 23 additions and 16 deletions
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11
llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
View File

@ -2187,12 +2187,23 @@ Instruction *InstCombinerImpl::visitSub(BinaryOperator &I) {
return replaceInstUsesWith(
I, Builder.CreateIntrinsic(Intrinsic::usub_sat, {Ty}, {X, Op1}));
// Op0 - umin(X, Op0) --> usub.sat(Op0, X)
if (match(Op1, m_OneUse(m_c_UMin(m_Value(X), m_Specific(Op0)))))
return replaceInstUsesWith(
I, Builder.CreateIntrinsic(Intrinsic::usub_sat, {Ty}, {Op0, X}));
// Op0 - umax(X, Op0) --> 0 - usub.sat(X, Op0)
if (match(Op1, m_OneUse(m_c_UMax(m_Value(X), m_Specific(Op0))))) {
Value *USub = Builder.CreateIntrinsic(Intrinsic::usub_sat, {Ty}, {X, Op0});
return BinaryOperator::CreateNeg(USub);
}
// umin(X, Op1) - Op1 --> 0 - usub.sat(Op1, X)
if (match(Op0, m_OneUse(m_c_UMin(m_Value(X), m_Specific(Op1))))) {
Value *USub = Builder.CreateIntrinsic(Intrinsic::usub_sat, {Ty}, {Op1, X});
return BinaryOperator::CreateNeg(USub);
}
// C - ctpop(X) => ctpop(~X) if C is bitwidth
if (match(Op0, m_SpecificInt(Ty->getScalarSizeInBits())) &&
match(Op1, m_OneUse(m_Intrinsic<Intrinsic::ctpop>(m_Value(X)))))

28
llvm/test/Transforms/InstCombine/sub-minmax.ll
View File

@ -39,9 +39,8 @@ define i32 @na_minus_max_na_b(i32 %A, i32 %B) {
define i5 @sub_umin(i5 %a, i5 %b) {
; CHECK-LABEL: @sub_umin(
; CHECK-NEXT: [[UMIN:%.*]] = call i5 @llvm.umin.i5(i5 [[A:%.*]], i5 [[B:%.*]])
; CHECK-NEXT: [[R:%.*]] = sub i5 [[A]], [[UMIN]]
; CHECK-NEXT: ret i5 [[R]]
; CHECK-NEXT: [[TMP1:%.*]] = call i5 @llvm.usub.sat.i5(i5 [[A:%.*]], i5 [[B:%.*]])
; CHECK-NEXT: ret i5 [[TMP1]]
;
%umin = call i5 @llvm.umin.i5(i5 %a, i5 %b)
%r = sub i5 %a, %umin
@ -50,9 +49,8 @@ define i5 @sub_umin(i5 %a, i5 %b) {
define <2 x i8> @sub_umin_commute_vec(<2 x i8> %a, <2 x i8> %b) {
; CHECK-LABEL: @sub_umin_commute_vec(
; CHECK-NEXT: [[UMIN:%.*]] = call <2 x i8> @llvm.umin.v2i8(<2 x i8> [[B:%.*]], <2 x i8> [[A:%.*]])
; CHECK-NEXT: [[R:%.*]] = sub <2 x i8> [[B]], [[UMIN]]
; CHECK-NEXT: ret <2 x i8> [[R]]
; CHECK-NEXT: [[TMP1:%.*]] = call <2 x i8> @llvm.usub.sat.v2i8(<2 x i8> [[B:%.*]], <2 x i8> [[A:%.*]])
; CHECK-NEXT: ret <2 x i8> [[TMP1]]
;
%umin = call <2 x i8> @llvm.umin.v2i8(<2 x i8> %b, <2 x i8> %a)
%r = sub <2 x i8> %b, %umin
@ -569,9 +567,8 @@ define i8 @umax_sub_op1_use(i8 %x, i8 %y) {
define i8 @umin_sub_op1(i8 %x, i8 %y) {
; CHECK-LABEL: @umin_sub_op1(
; CHECK-NEXT: [[U:%.*]] = call i8 @llvm.umin.i8(i8 [[Y:%.*]], i8 [[X:%.*]])
; CHECK-NEXT: [[R:%.*]] = sub i8 [[Y]], [[U]]
; CHECK-NEXT: ret i8 [[R]]
; CHECK-NEXT: [[TMP1:%.*]] = call i8 @llvm.usub.sat.i8(i8 [[Y:%.*]], i8 [[X:%.*]])
; CHECK-NEXT: ret i8 [[TMP1]]
;
%u = call i8 @llvm.umin.i8(i8 %y, i8 %x)
%r = sub i8 %y, %u
@ -580,9 +577,8 @@ define i8 @umin_sub_op1(i8 %x, i8 %y) {
define i8 @umin_sub_op1_commute(i8 %x, i8 %y) {
; CHECK-LABEL: @umin_sub_op1_commute(
; CHECK-NEXT: [[U:%.*]] = call i8 @llvm.umin.i8(i8 [[X:%.*]], i8 [[Y:%.*]])
; CHECK-NEXT: [[R:%.*]] = sub i8 [[Y]], [[U]]
; CHECK-NEXT: ret i8 [[R]]
; CHECK-NEXT: [[TMP1:%.*]] = call i8 @llvm.usub.sat.i8(i8 [[Y:%.*]], i8 [[X:%.*]])
; CHECK-NEXT: ret i8 [[TMP1]]
;
%u = call i8 @llvm.umin.i8(i8 %x, i8 %y)
%r = sub i8 %y, %u
@ -591,8 +587,8 @@ define i8 @umin_sub_op1_commute(i8 %x, i8 %y) {
define i8 @umin_sub_op0(i8 %x, i8 %y) {
; CHECK-LABEL: @umin_sub_op0(
; CHECK-NEXT: [[U:%.*]] = call i8 @llvm.umin.i8(i8 [[Y:%.*]], i8 [[X:%.*]])
; CHECK-NEXT: [[R:%.*]] = sub i8 [[U]], [[Y]]
; CHECK-NEXT: [[TMP1:%.*]] = call i8 @llvm.usub.sat.i8(i8 [[Y:%.*]], i8 [[X:%.*]])
; CHECK-NEXT: [[R:%.*]] = sub i8 0, [[TMP1]]
; CHECK-NEXT: ret i8 [[R]]
;
%u = call i8 @llvm.umin.i8(i8 %y, i8 %x)
@ -602,8 +598,8 @@ define i8 @umin_sub_op0(i8 %x, i8 %y) {
define i8 @umin_sub_op0_commute(i8 %x, i8 %y) {
; CHECK-LABEL: @umin_sub_op0_commute(
; CHECK-NEXT: [[U:%.*]] = call i8 @llvm.umin.i8(i8 [[X:%.*]], i8 [[Y:%.*]])
; CHECK-NEXT: [[R:%.*]] = sub i8 [[U]], [[Y]]
; CHECK-NEXT: [[TMP1:%.*]] = call i8 @llvm.usub.sat.i8(i8 [[Y:%.*]], i8 [[X:%.*]])
; CHECK-NEXT: [[R:%.*]] = sub i8 0, [[TMP1]]
; CHECK-NEXT: ret i8 [[R]]
;
%u = call i8 @llvm.umin.i8(i8 %x, i8 %y)