[llvm] [InstCombine] Ensure Safe Handling of Flags in foldFNegIntoConstant (PR #94148)

[Andy Kaylor via llvm-commits]

================
@@ -1109,4 +1109,96 @@ define float @test_fneg_select_maxnum(float %x) {
   ret float %neg
 }
 
+define float @test_fneg_ninf_mul_with_anyzero(float %a) {
+; CHECK-LABEL: @test_fneg_ninf_mul_with_anyzero(
+; CHECK-NEXT:    [[F:%.*]] = fmul float [[A:%.*]], -0.000000e+00
+; CHECK-NEXT:    ret float [[F]]
+;
+  %mul = fmul float %a, 0.0
+  %f = fneg ninf float %mul
+  ret float %f
+}
+
+define float @test_fsub_ninf_mul_with_anyzero(float %a) {
+; CHECK-LABEL: @test_fsub_ninf_mul_with_anyzero(
+; CHECK-NEXT:    [[F2:%.*]] = fmul nsz float [[A:%.*]], -0.000000e+00
+; CHECK-NEXT:    ret float [[F2]]
+;
+  %f1 = fmul nsz float %a, 0.000000
+  %f2 = fsub ninf float -0.000000, %f1
+  ret float %f2
+}
+
+define float @test_fneg_nnan_mul_with_anyzero(float %a) {
+; CHECK-LABEL: @test_fneg_nnan_mul_with_anyzero(
+; CHECK-NEXT:    [[TMP1:%.*]] = fneg nnan float [[A:%.*]]
+; CHECK-NEXT:    [[F2:%.*]] = call nnan float @llvm.copysign.f32(float 0.000000e+00, float [[TMP1]])
+; CHECK-NEXT:    ret float [[F2]]
+;
+  %f1 = fmul ninf float %a, 0.000000
+  %f2 = fneg nnan float %f1
+  ret float %f2
+}
+
+define float @test_fneg_nsz_mul_with_anyzero(float %a) {
+; CHECK-LABEL: @test_fneg_nsz_mul_with_anyzero(
+; CHECK-NEXT:    [[F2:%.*]] = fmul nsz float [[A:%.*]], -0.000000e+00
+; CHECK-NEXT:    ret float [[F2]]
+;
+  %f1 = fmul ninf float %a, 0.000000
+  %f2 = fneg nsz float %f1
+  ret float %f2
+}
+
+define float @test_fneg_ninf_mul_nnan_with_const(float %a) {
+; CHECK-LABEL: @test_fneg_ninf_mul_nnan_with_const(
+; CHECK-NEXT:    [[TMP1:%.*]] = fneg float [[A:%.*]]
+; CHECK-NEXT:    [[F2:%.*]] = call float @llvm.copysign.f32(float 0.000000e+00, float [[TMP1]])
+; CHECK-NEXT:    ret float [[F2]]
+;
+  %f1 = fmul nnan float %a, 0.000000
+  %f2 = fneg ninf float %f1
+  ret float %f2
+}
+
+define float @test_fneg_ninf_mul_nsz_with_const(float %a) {
+; CHECK-LABEL: @test_fneg_ninf_mul_nsz_with_const(
+; CHECK-NEXT:    [[F2:%.*]] = fmul nsz float [[A:%.*]], -0.000000e+00
+; CHECK-NEXT:    ret float [[F2]]
+;
+  %f1 = fmul nsz float %a, 0.000000
+  %f2 = fneg ninf float %f1
+  ret float %f2
+}
+
+define <2 x float> @test_fneg_ninf_mul_nnan_with_vec_const(<2 x float> %a) {
+; CHECK-LABEL: @test_fneg_ninf_mul_nnan_with_vec_const(
+; CHECK-NEXT:    [[F2:%.*]] = fmul nnan <2 x float> [[A:%.*]], <float -0.000000e+00, float 0.000000e+00>
+; CHECK-NEXT:    ret <2 x float> [[F2]]
+;
+  %f1 = fmul nnan <2 x float> %a, <float 0.000000, float -0.000000>
+  %f2 = fneg ninf <2 x float> %f1
+  ret <2 x float> %f2
+}
+
+define <2 x float> @test_fneg_ninf_mul_nsz_with_vec_const(<2 x float> %a) {
+; CHECK-LABEL: @test_fneg_ninf_mul_nsz_with_vec_const(
+; CHECK-NEXT:    [[F2:%.*]] = fmul nsz <2 x float> [[A:%.*]], <float -0.000000e+00, float 0.000000e+00>
+; CHECK-NEXT:    ret <2 x float> [[F2]]
+;
+  %f1 = fmul nsz <2 x float> %a, <float 0.000000, float -0.000000>
+  %f2 = fneg ninf <2 x float> %f1
+  ret <2 x float> %f2
+}
+
+define <2 x float> @test_fneg_nnan_ninf_mul_with_vec_const(<2 x float> %a) {
+; CHECK-LABEL: @test_fneg_nnan_ninf_mul_with_vec_const(
+; CHECK-NEXT:    [[F2:%.*]] = fmul nnan <2 x float> [[A:%.*]], <float -0.000000e+00, float 0.000000e+00>
+; CHECK-NEXT:    ret <2 x float> [[F2]]
+;
+  %f1 = fmul <2 x float> %a, <float 0.000000, float -0.000000>
+  %f2 = fneg nnan ninf <2 x float> %f1
+  ret <2 x float> %f2
+}
+
----------------
andykaylor wrote:

> ```llvm
> ; With nsz and reassoc: Y - ((X * 5) + Y) --> X * -5
> ```

That transformation should require `nnan` or isKnownNeverNaN(Y)

https://github.com/llvm/llvm-project/pull/94148