[InstCombine] Fold fneg over select #89947
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@llvm/pr-subscribers-llvm-transforms Author: Yingwei Zheng (dtcxzyw) ChangesAs we folds fabs over select in #86390, this patch folds fneg over select to make sure nabs idioms are generated. Alive2 for FMF propagation: https://alive2.llvm.org/ce/z/-h6Vuo Full diff: https://github.com/llvm/llvm-project/pull/89947.diff 3 Files Affected:
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index 88b7e496897e1f..ea2cdadc84f143 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -2781,6 +2781,16 @@ Instruction *InstCombinerImpl::visitFNeg(UnaryOperator &I) {
propagateSelectFMF(NewSel, P == X);
return NewSel;
}
+
+ // -(Cond ? X : C) --> Cond ? -X : -C
+ // -(Cond ? C : Y) --> Cond ? -C : -Y
+ if (match(X, m_ImmConstant()) || match(Y, m_ImmConstant())) {
+ Value *NegX = Builder.CreateFNegFMF(X, &I, X->getName() + ".neg");
+ Value *NegY = Builder.CreateFNegFMF(Y, &I, Y->getName() + ".neg");
+ SelectInst *NewSel = SelectInst::Create(Cond, NegX, NegY);
+ propagateSelectFMF(NewSel, /*CommonOperand=*/true);
+ return NewSel;
+ }
}
// fneg (copysign x, y) -> copysign x, (fneg y)
diff --git a/llvm/test/Transforms/InstCombine/fneg.ll b/llvm/test/Transforms/InstCombine/fneg.ll
index 7c9289c447113f..3c4088832feaaa 100644
--- a/llvm/test/Transforms/InstCombine/fneg.ll
+++ b/llvm/test/Transforms/InstCombine/fneg.ll
@@ -980,7 +980,7 @@ define float @fneg_ldexp_contract(float %x, i32 %n) {
define float @fneg_ldexp_metadata(float %x, i32 %n) {
; CHECK-LABEL: @fneg_ldexp_metadata(
; CHECK-NEXT: [[TMP1:%.*]] = fneg float [[X:%.*]]
-; CHECK-NEXT: [[NEG:%.*]] = call float @llvm.ldexp.f32.i32(float [[TMP1]], i32 [[N:%.*]]), !arst !0
+; CHECK-NEXT: [[NEG:%.*]] = call float @llvm.ldexp.f32.i32(float [[TMP1]], i32 [[N:%.*]]), !arst [[META0:![0-9]+]]
; CHECK-NEXT: ret float [[NEG]]
;
%ldexp = call float @llvm.ldexp.f32.i32(float %x, i32 %n), !arst !0
@@ -988,4 +988,125 @@ define float @fneg_ldexp_metadata(float %x, i32 %n) {
ret float %neg
}
+define float @test_fneg_select_constants(i1 %cond) {
+; CHECK-LABEL: @test_fneg_select_constants(
+; CHECK-NEXT: [[NEG:%.*]] = select i1 [[COND:%.*]], float -0.000000e+00, float 0.000000e+00
+; CHECK-NEXT: ret float [[NEG]]
+;
+ %sel1 = select i1 %cond, float 0.0, float -0.0
+ %neg = fneg float %sel1
+ ret float %neg
+}
+
+define <2 x float> @test_fneg_vec(<2 x i1> %cond) {
+; CHECK-LABEL: @test_fneg_vec(
+; CHECK-NEXT: [[NEG:%.*]] = select <2 x i1> [[COND:%.*]], <2 x float> <float -0.000000e+00, float 0.000000e+00>, <2 x float> <float 0.000000e+00, float -0.000000e+00>
+; CHECK-NEXT: ret <2 x float> [[NEG]]
+;
+ %sel1 = select <2 x i1> %cond, <2 x float> <float 0.0, float -0.0>, <2 x float> <float -0.0, float 0.0>
+ %neg = fneg <2 x float> %sel1
+ ret <2 x float> %neg
+}
+
+define float @test_fneg_select_var_constant(i1 %cond, float %x) {
+; CHECK-LABEL: @test_fneg_select_var_constant(
+; CHECK-NEXT: [[X_NEG:%.*]] = fneg float [[X:%.*]]
+; CHECK-NEXT: [[NEG:%.*]] = select i1 [[COND:%.*]], float [[X_NEG]], float 0.000000e+00
+; CHECK-NEXT: ret float [[NEG]]
+;
+ %sel1 = select i1 %cond, float %x, float -0.0
+ %neg = fneg float %sel1
+ ret float %neg
+}
+
+; nsz can be preserved.
+
+define float @test_fneg_select_var_constant_fmf1(i1 %cond, float %x) {
+; CHECK-LABEL: @test_fneg_select_var_constant_fmf1(
+; CHECK-NEXT: [[X_NEG:%.*]] = fneg float [[X:%.*]]
+; CHECK-NEXT: [[NEG:%.*]] = select nnan ninf nsz i1 [[COND:%.*]], float [[X_NEG]], float -1.000000e+00
+; CHECK-NEXT: ret float [[NEG]]
+;
+ %sel1 = select nnan ninf nsz i1 %cond, float %x, float 1.0
+ %neg = fneg float %sel1
+ ret float %neg
+}
+
+define float @test_fneg_select_var_constant_fmf2(i1 %cond, float %x) {
+; CHECK-LABEL: @test_fneg_select_var_constant_fmf2(
+; CHECK-NEXT: [[X_NEG:%.*]] = fneg nnan ninf nsz float [[X:%.*]]
+; CHECK-NEXT: [[NEG:%.*]] = select nnan ninf nsz i1 [[COND:%.*]], float [[X_NEG]], float -1.000000e+00
+; CHECK-NEXT: ret float [[NEG]]
+;
+ %sel1 = select i1 %cond, float %x, float 1.0
+ %neg = fneg nnan ninf nsz float %sel1
+ ret float %neg
+}
+
+define float @test_fneg_select_constant_var(i1 %cond, float %x) {
+; CHECK-LABEL: @test_fneg_select_constant_var(
+; CHECK-NEXT: [[X_NEG:%.*]] = fneg float [[X:%.*]]
+; CHECK-NEXT: [[NEG:%.*]] = select i1 [[COND:%.*]], float -0.000000e+00, float [[X_NEG]]
+; CHECK-NEXT: ret float [[NEG]]
+;
+ %sel1 = select i1 %cond, float 0.0, float %x
+ %neg = fneg float %sel1
+ ret float %neg
+}
+
+; Make sure nabs is generated.
+
+define float @test_fneg_select_abs(i1 %cond, float %x) {
+; CHECK-LABEL: @test_fneg_select_abs(
+; CHECK-NEXT: [[ABSX:%.*]] = call float @llvm.fabs.f32(float [[X:%.*]])
+; CHECK-NEXT: [[ABSX_NEG:%.*]] = fneg float [[ABSX]]
+; CHECK-NEXT: [[NEG:%.*]] = select i1 [[COND:%.*]], float -0.000000e+00, float [[ABSX_NEG]]
+; CHECK-NEXT: ret float [[NEG]]
+;
+ %absx = call float @llvm.fabs.f32(float %x)
+ %sel1 = select i1 %cond, float 0.0, float %absx
+ %neg = fneg float %sel1
+ ret float %neg
+}
+
+define float @test_fneg_fabs_select(i1 %cond, float %x) {
+; CHECK-LABEL: @test_fneg_fabs_select(
+; CHECK-NEXT: [[TMP1:%.*]] = call float @llvm.fabs.f32(float [[X:%.*]])
+; CHECK-NEXT: [[DOTNEG:%.*]] = fneg float [[TMP1]]
+; CHECK-NEXT: [[NEG:%.*]] = select i1 [[COND:%.*]], float -0.000000e+00, float [[DOTNEG]]
+; CHECK-NEXT: ret float [[NEG]]
+;
+ %sel1 = select i1 %cond, float 0.0, float %x
+ %abs = call float @llvm.fabs.f32(float %sel1)
+ %neg = fneg float %abs
+ ret float %neg
+}
+
+define float @test_fneg_select_constant_var_multiuse(i1 %cond, float %x) {
+; CHECK-LABEL: @test_fneg_select_constant_var_multiuse(
+; CHECK-NEXT: [[SEL1:%.*]] = select i1 [[COND:%.*]], float 0.000000e+00, float [[X:%.*]]
+; CHECK-NEXT: call void @use(float [[SEL1]])
+; CHECK-NEXT: [[NEG:%.*]] = fneg float [[SEL1]]
+; CHECK-NEXT: ret float [[NEG]]
+;
+ %sel1 = select i1 %cond, float 0.0, float %x
+ call void @use(float %sel1)
+ %neg = fneg float %sel1
+ ret float %neg
+}
+
+; Don't break fmax idioms.
+
+define float @test_fneg_select_maxnum(float %x) {
+; CHECK-LABEL: @test_fneg_select_maxnum(
+; CHECK-NEXT: [[SEL1:%.*]] = call nnan nsz float @llvm.maxnum.f32(float [[X:%.*]], float 1.000000e+00)
+; CHECK-NEXT: [[NEG:%.*]] = fneg float [[SEL1]]
+; CHECK-NEXT: ret float [[NEG]]
+;
+ %cmp1 = fcmp ogt float %x, 1.0
+ %sel1 = select nnan nsz i1 %cmp1, float %x, float 1.0
+ %neg = fneg float %sel1
+ ret float %neg
+}
+
!0 = !{}
diff --git a/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass.ll b/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass.ll
index a7d01b4f824db0..e4fb7764ba9e53 100644
--- a/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass.ll
+++ b/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass.ll
@@ -364,8 +364,8 @@ define nofpclass(inf) float @ret_nofpclass_inf__select_chain_inf_nan_1(i1 %cond,
define nofpclass(inf) float @ret_nofpclass_inf__fabs_select_ninf_rhs(i1 %cond, float %x) {
; CHECK-LABEL: define nofpclass(inf) float @ret_nofpclass_inf__fabs_select_ninf_rhs
; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]]) {
-; CHECK-NEXT: [[FABS:%.*]] = call float @llvm.fabs.f32(float [[X]])
-; CHECK-NEXT: ret float [[FABS]]
+; CHECK-NEXT: [[TMP1:%.*]] = call float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT: ret float [[TMP1]]
;
%select = select i1 %cond, float %x, float 0xFFF0000000000000
%fabs = call float @llvm.fabs.f32(float %select)
@@ -376,8 +376,8 @@ define nofpclass(inf) float @ret_nofpclass_inf__fabs_select_ninf_rhs(i1 %cond, f
define nofpclass(inf) float @ret_nofpclass_inf__fabs_select_pinf_rhs(i1 %cond, float %x) {
; CHECK-LABEL: define nofpclass(inf) float @ret_nofpclass_inf__fabs_select_pinf_rhs
; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]]) {
-; CHECK-NEXT: [[FABS:%.*]] = call float @llvm.fabs.f32(float [[X]])
-; CHECK-NEXT: ret float [[FABS]]
+; CHECK-NEXT: [[TMP1:%.*]] = call float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT: ret float [[TMP1]]
;
%select = select i1 %cond, float %x, float 0x7FF0000000000000
%fabs = call float @llvm.fabs.f32(float %select)
@@ -400,8 +400,8 @@ define nofpclass(ninf nnorm nsub nzero) float @ret_nofpclass_no_negatives__fabs_
define nofpclass(pinf pnorm psub pzero) float @ret_nofpclass_no_positives__fabs_select_pinf_rhs(i1 %cond, float %x) {
; CHECK-LABEL: define nofpclass(pinf pzero psub pnorm) float @ret_nofpclass_no_positives__fabs_select_pinf_rhs
; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]]) {
-; CHECK-NEXT: [[FABS:%.*]] = call float @llvm.fabs.f32(float [[X]])
-; CHECK-NEXT: ret float [[FABS]]
+; CHECK-NEXT: [[TMP1:%.*]] = call float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT: ret float [[TMP1]]
;
%select = select i1 %cond, float %x, float 0x7FF0000000000000
%fabs = call float @llvm.fabs.f32(float %select)
@@ -435,8 +435,8 @@ define nofpclass(nan pinf pnorm psub pzero) float @ret_nofpclass_no_positives_na
define nofpclass(inf) float @ret_nofpclass_inf__fneg_select_ninf_rhs(i1 %cond, float %x) {
; CHECK-LABEL: define nofpclass(inf) float @ret_nofpclass_inf__fneg_select_ninf_rhs
; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]]) {
-; CHECK-NEXT: [[FNEG:%.*]] = fneg float [[X]]
-; CHECK-NEXT: ret float [[FNEG]]
+; CHECK-NEXT: [[X_NEG:%.*]] = fneg float [[X]]
+; CHECK-NEXT: ret float [[X_NEG]]
;
%select = select i1 %cond, float %x, float 0xFFF0000000000000
%fneg = fneg float %select
@@ -447,8 +447,8 @@ define nofpclass(inf) float @ret_nofpclass_inf__fneg_select_ninf_rhs(i1 %cond, f
define nofpclass(inf nnorm nsub nzero) float @ret_nofpclass_nonegatives_noinf___fneg_select_pinf_rhs(i1 %cond, float %x) {
; CHECK-LABEL: define nofpclass(inf nzero nsub nnorm) float @ret_nofpclass_nonegatives_noinf___fneg_select_pinf_rhs
; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]]) {
-; CHECK-NEXT: [[FNEG:%.*]] = fneg float [[X]]
-; CHECK-NEXT: ret float [[FNEG]]
+; CHECK-NEXT: [[X_NEG:%.*]] = fneg float [[X]]
+; CHECK-NEXT: ret float [[X_NEG]]
;
%select = select i1 %cond, float %x, float 0x7FF0000000000000
%fneg = fneg float %select
@@ -459,8 +459,8 @@ define nofpclass(inf nnorm nsub nzero) float @ret_nofpclass_nonegatives_noinf___
define nofpclass(inf nnorm nsub nzero) float @ret_nofpclass_nonegatives_noinf___fneg_select_ninf_lhs(i1 %cond, float %x) {
; CHECK-LABEL: define nofpclass(inf nzero nsub nnorm) float @ret_nofpclass_nonegatives_noinf___fneg_select_ninf_lhs
; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]]) {
-; CHECK-NEXT: [[FNEG:%.*]] = fneg float [[X]]
-; CHECK-NEXT: ret float [[FNEG]]
+; CHECK-NEXT: [[X_NEG:%.*]] = fneg float [[X]]
+; CHECK-NEXT: ret float [[X_NEG]]
;
%select = select i1 %cond, float 0xFFF0000000000000, float %x
%fneg = fneg float %select
@@ -470,8 +470,8 @@ define nofpclass(inf nnorm nsub nzero) float @ret_nofpclass_nonegatives_noinf___
define nofpclass(pzero psub pnorm pinf) float @ret_nofpclass_nopositives___fneg_select_pinf_rhs(i1 %cond, float %x) {
; CHECK-LABEL: define nofpclass(pinf pzero psub pnorm) float @ret_nofpclass_nopositives___fneg_select_pinf_rhs
; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]]) {
-; CHECK-NEXT: [[SELECT:%.*]] = select i1 [[COND]], float [[X]], float 0x7FF0000000000000
-; CHECK-NEXT: [[FNEG:%.*]] = fneg float [[SELECT]]
+; CHECK-NEXT: [[X_NEG:%.*]] = fneg float [[X]]
+; CHECK-NEXT: [[FNEG:%.*]] = select i1 [[COND]], float [[X_NEG]], float 0xFFF0000000000000
; CHECK-NEXT: ret float [[FNEG]]
;
%select = select i1 %cond, float %x, float 0x7FF0000000000000
@@ -483,9 +483,9 @@ define nofpclass(pzero psub pnorm pinf) float @ret_nofpclass_nopositives___fneg_
define nofpclass(inf) float @ret_nofpclass_inf__fneg_fabs_select_pinf_rhs(i1 %cond, float %x) {
; CHECK-LABEL: define nofpclass(inf) float @ret_nofpclass_inf__fneg_fabs_select_pinf_rhs
; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]]) {
-; CHECK-NEXT: [[FABS:%.*]] = call float @llvm.fabs.f32(float [[X]])
-; CHECK-NEXT: [[FNEG:%.*]] = fneg float [[FABS]]
-; CHECK-NEXT: ret float [[FNEG]]
+; CHECK-NEXT: [[TMP1:%.*]] = call float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT: [[DOTNEG:%.*]] = fneg float [[TMP1]]
+; CHECK-NEXT: ret float [[DOTNEG]]
;
%select = select i1 %cond, float %x, float 0x7FF0000000000000
%fabs = call float @llvm.fabs.f32(float %select)
@@ -497,9 +497,9 @@ define nofpclass(inf) float @ret_nofpclass_inf__fneg_fabs_select_pinf_rhs(i1 %co
define nofpclass(ninf nnorm nsub nzero) float @ret_nofpclass_nonegatives__fneg_fabs_select_pinf_rhs(i1 %cond, float %x) {
; CHECK-LABEL: define nofpclass(ninf nzero nsub nnorm) float @ret_nofpclass_nonegatives__fneg_fabs_select_pinf_rhs
; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]]) {
-; CHECK-NEXT: [[FABS:%.*]] = call float @llvm.fabs.f32(float [[X]])
-; CHECK-NEXT: [[FNEG:%.*]] = fneg float [[FABS]]
-; CHECK-NEXT: ret float [[FNEG]]
+; CHECK-NEXT: [[TMP1:%.*]] = call float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT: [[DOTNEG:%.*]] = fneg float [[TMP1]]
+; CHECK-NEXT: ret float [[DOTNEG]]
;
%select = select i1 %cond, float %x, float 0x7FF0000000000000
%fabs = call float @llvm.fabs.f32(float %select)
@@ -535,8 +535,8 @@ define nofpclass(inf) float @ret_nofpclass_inf__copysign_unknown_select_pinf_rhs
define nofpclass(inf) float @ret_nofpclass_inf__copysign_positive_select_pinf_rhs(i1 %cond, float %x) {
; CHECK-LABEL: define nofpclass(inf) float @ret_nofpclass_inf__copysign_positive_select_pinf_rhs
; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]]) {
-; CHECK-NEXT: [[COPYSIGN:%.*]] = call float @llvm.fabs.f32(float [[X]])
-; CHECK-NEXT: ret float [[COPYSIGN]]
+; CHECK-NEXT: [[TMP1:%.*]] = call float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT: ret float [[TMP1]]
;
%select = select i1 %cond, float %x, float 0x7FF0000000000000
%copysign = call float @llvm.copysign.f32(float %select, float 1.0)
@@ -547,8 +547,8 @@ define nofpclass(inf) float @ret_nofpclass_inf__copysign_negative_select_pinf_rh
; CHECK-LABEL: define nofpclass(inf) float @ret_nofpclass_inf__copysign_negative_select_pinf_rhs
; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]]) {
; CHECK-NEXT: [[TMP1:%.*]] = call float @llvm.fabs.f32(float [[X]])
-; CHECK-NEXT: [[COPYSIGN:%.*]] = fneg float [[TMP1]]
-; CHECK-NEXT: ret float [[COPYSIGN]]
+; CHECK-NEXT: [[DOTNEG:%.*]] = fneg float [[TMP1]]
+; CHECK-NEXT: ret float [[DOTNEG]]
;
%select = select i1 %cond, float %x, float 0x7FF0000000000000
%copysign = call float @llvm.copysign.f32(float %select, float -1.0)
@@ -627,8 +627,8 @@ define nofpclass(nan ninf nnorm nsub nzero) float @ret_nofpclass_nonegatives_non
define nofpclass(pinf pnorm psub pzero) float @ret_nofpclass_nopositives__copysign_fabs_select_pinf_rhs(i1 %cond, float %x, float %sign) {
; CHECK-LABEL: define nofpclass(pinf pzero psub pnorm) float @ret_nofpclass_nopositives__copysign_fabs_select_pinf_rhs
; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]], float [[SIGN:%.*]]) {
-; CHECK-NEXT: [[COPYSIGN:%.*]] = call float @llvm.fabs.f32(float [[X]])
-; CHECK-NEXT: ret float [[COPYSIGN]]
+; CHECK-NEXT: [[TMP1:%.*]] = call float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT: ret float [[TMP1]]
;
%select = select i1 %cond, float %x, float 0x7FF0000000000000
%fabs.sign = call float @llvm.fabs.f32(float %sign)
@@ -678,9 +678,9 @@ define nofpclass(ninf nnorm nsub nzero) float @ret_nofpclass_no_negatives__copys
define nofpclass(pinf pnorm psub pzero) float @ret_nofpclass_no_positives__copysign_unknown_select_pinf_rhs(i1 %cond, float %x, float %unknown.sign) {
; CHECK-LABEL: define nofpclass(pinf pzero psub pnorm) float @ret_nofpclass_no_positives__copysign_unknown_select_pinf_rhs
; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]], float [[UNKNOWN_SIGN:%.*]]) {
-; CHECK-NEXT: [[TMP2:%.*]] = call float @llvm.fabs.f32(float [[X]])
-; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[COND]], float [[TMP2]], float 0x7FF0000000000000
-; CHECK-NEXT: [[COPYSIGN:%.*]] = fneg float [[TMP1]]
+; CHECK-NEXT: [[TMP1:%.*]] = call float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT: [[DOTNEG:%.*]] = fneg float [[TMP1]]
+; CHECK-NEXT: [[COPYSIGN:%.*]] = select i1 [[COND]], float [[DOTNEG]], float 0xFFF0000000000000
; CHECK-NEXT: ret float [[COPYSIGN]]
;
%select = select i1 %cond, float %x, float 0x7FF0000000000000
@@ -705,9 +705,9 @@ define nofpclass(nan ninf nnorm nsub nzero) float @ret_nofpclass_no_negatives_no
define nofpclass(nan pinf pnorm psub pzero) float @ret_nofpclass_no_positives_nonan__copysign_unknown_select_pinf_rhs(i1 %cond, float %x, float %unknown.sign) {
; CHECK-LABEL: define nofpclass(nan pinf pzero psub pnorm) float @ret_nofpclass_no_positives_nonan__copysign_unknown_select_pinf_rhs
; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]], float [[UNKNOWN_SIGN:%.*]]) {
-; CHECK-NEXT: [[TMP2:%.*]] = call float @llvm.fabs.f32(float [[X]])
-; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[COND]], float [[TMP2]], float 0x7FF0000000000000
-; CHECK-NEXT: [[COPYSIGN:%.*]] = fneg float [[TMP1]]
+; CHECK-NEXT: [[TMP1:%.*]] = call float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT: [[DOTNEG:%.*]] = fneg float [[TMP1]]
+; CHECK-NEXT: [[COPYSIGN:%.*]] = select i1 [[COND]], float [[DOTNEG]], float 0xFFF0000000000000
; CHECK-NEXT: ret float [[COPYSIGN]]
;
%select = select i1 %cond, float %x, float 0x7FF0000000000000
|
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| SelectInst *NewSel = SelectInst::Create(Cond, NegX, NegY); | ||
| propagateSelectFMF(NewSel, /*CommonOperand=*/true); | ||
| return NewSel; | ||
| } |
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Can we use FoldOpIntoSelect here instead?
There was a problem hiding this comment.
No. FoldOpIntoSelect doesn't propagate FMF flags from fneg to select.
See #86390. nsz flag is not always safe to be propagated. So they would be better to be handled separately.
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As we folds fabs over select in #86390, this patch folds fneg over select to make sure nabs idioms are generated.
Addresses #86390 (comment).
Alive2 for FMF propagation: https://alive2.llvm.org/ce/z/-h6Vuo