[clang] [CIR][NEON] Add lowering for `vnegd_s64` and `vnegh_f16` (PR #180597)

[Henrich Lauko via cfe-commits]

================
@@ -375,19 +389,18 @@ class CIRGenBuilderTy : public cir::CIRBaseBuilderTy {
     llvm_unreachable("negation for the given type is NYI");
   }
 
-  cir::IsFPClassOp createIsFPClass(mlir::Location loc, mlir::Value src,
-                                   cir::FPClassTest flags) {
-    return cir::IsFPClassOp::create(*this, loc, src, flags);
-  }
+  mlir::Value createFNeg(mlir::Value value) {
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xlauko wrote:

Maybe add defensive constrain:

```
assert(mlir::isa<cir::CIRFPTypeInterface>(value.getType()))
```

https://github.com/llvm/llvm-project/pull/180597