Add support for vector in DataValueExt::int() (#6844)

* Add support for vector in DataValueExt::int()

Fixes #6827

* Replace `if` with `match`

* Enable interpreter test for simd ineg

Issue #6827

* Format code with `cargo fmt`

and also improve comment

cranelift/filetests/filetests/runtests/simd-ineg.clif

@@ -1,3 +1,4 @@
+test interpret
 test run
 target aarch64
 target s390x

cranelift/interpreter/src/value.rs

@@ -263,7 +263,14 @@ macro_rules! bitop {
 
 impl DataValueExt for DataValue {
     fn int(n: i128, ty: Type) -> ValueResult<Self> {
-        if ty.is_int() && !ty.is_vector() {
+        if ty.is_vector() {
+            // match ensures graceful failure since read_from_slice_ne()
+            // panics on anything other than 8 and 16 bytes
+            match ty.bytes() {
+                8 | 16 => Ok(DataValue::read_from_slice_ne(&n.to_ne_bytes(), ty)),
+                _ => Err(ValueError::InvalidType(ValueTypeClass::Vector, ty)),
+            }
+        } else if ty.is_int() {
             DataValue::from_integer(n, ty).map_err(|_| ValueError::InvalidValue(ty))
         } else {
             Err(ValueError::InvalidType(ValueTypeClass::Integer, ty))