[llvm] [DAG] computeKnownFPClass - add ISD::FNEG handling + test coverage (PR #190325)

[Simon Pilgrim via llvm-commits]

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@@ -0,0 +1,60 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 6
+; RUN: llc < %s -mtriple=riscv64 -mattr=+v,+f,+d | FileCheck %s
+
+declare i1 @llvm.is.fpclass.f32(float, i32)
+declare <4 x i1> @llvm.is.fpclass.vf32(<4 x float>, i32)
+
+define i1 @fneg_const_not_inf() nounwind {
+; CHECK-LABEL: fneg_const_not_inf:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    li a0, 0
+; CHECK-NEXT:    ret
+  %n = fneg float 1.0
+  %r = call i1 @llvm.is.fpclass.f32(float %n, i32 512) ; +inf
+  ret i1 %r
+}
+
+define i1 @fneg_mask_not_nan(i32 %a) nounwind {
+; CHECK-LABEL: fneg_mask_not_nan:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    li a0, 0
+; CHECK-NEXT:    ret
+  %m = and i32 %a, u0x007fffff
+  %x = bitcast i32 %m to float
+  %n = fneg float %x
+  %r = call i1 @llvm.is.fpclass.f32(float %n, i32 3) ; nan
+  ret i1 %r
+}
+
+define i1 @fneg_shift_not_inf(i32 %x) nounwind {
+; CHECK-LABEL: fneg_shift_not_inf:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    li a0, 0
+; CHECK-NEXT:    ret
+  %shl = shl i32 %x, 2
+  %shr = lshr i32 %shl, 2
+  %y = bitcast i32 %shr to float
+
+  %n = fneg float %y
+  %r = call i1 @llvm.is.fpclass.f32(float %n, i32 512) ; +inf
+  ret i1 %r
+}
+
+define <4 x i1> @fneg_vec_not_inf(<4 x i32> %vecbits) nounwind {
+; CHECK-LABEL: fneg_vec_not_inf:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    lui a0, 262144
+; CHECK-NEXT:    addi a0, a0, -1
+; CHECK-NEXT:    vsetivli zero, 4, e32, m1, ta, ma
+; CHECK-NEXT:    vand.vx v8, v8, a0
+; CHECK-NEXT:    vfneg.v v8, v8
+; CHECK-NEXT:    vfclass.v v8, v8
+; CHECK-NEXT:    vand.vi v8, v8, 14
+; CHECK-NEXT:    vmsne.vi v0, v8, 0
+; CHECK-NEXT:    ret
+  %masked = and <4 x i32> %vecbits, <i32 u0x3fffffff, i32 u0x3fffffff, i32 u0x3fffffff, i32 u0x3fffffff>
----------------
RKSimon wrote:

```suggestion
  %masked = and <4 x i32> %vecbits, splat (i32 u0x3fffffff)
```

https://github.com/llvm/llvm-project/pull/190325