Implement Extractlane, UaddSat, and UsubSat for Cranelift interpreter (#3188)

* Implement `Extractlane`, `UaddSat`, and `UsubSat` for Cranelift interpreter

Implemented the `Extractlane`, `UaddSat`, and `UsubSat` opcodes for the interpreter,
and added helper functions for working with SIMD vectors (`extractlanes`, `vectorizelanes`,
and `binary_arith`).

Copyright (c) 2021, Arm Limited

* Re-use tests + constrict Vector assert

- Re-use interpreter tests as runtests where supported.
- Constrict Vector assertion.
- Code style adjustments following feedback.

Copyright (c) 2021, Arm Limited

* Runtest `i32x4` vectors on AArch64; add `i64x2` tests

Copyright (c) 2021, Arm Limited

* Add `simd-` prefix to test filenames

Copyright (c) 2021, Arm Limited

* Return aliased `SmallVec` from `extractlanes`

Using a `SmallVec<[i128; 4]>` allows larger-width 128-bit vectors
(`i32x4`, `i64x2`, ...) to not cause heap allocations.

Copyright (c) 2021, Arm Limited

* Accept slice to `vectorizelanes` rather than `Vec`

Copyright (c) 2021, Arm Limited

cranelift/interpreter/src/value.rs

@@ -22,6 +22,7 @@ pub trait Value: Clone + From<DataValue> {
     fn bool(b: bool, ty: Type) -> ValueResult<Self>;
     fn into_bool(self) -> ValueResult<bool>;
     fn vector(v: [u8; 16], ty: Type) -> ValueResult<Self>;
+    fn into_array(&self) -> ValueResult<[u8; 16]>;
     fn convert(self, kind: ValueConversionKind) -> ValueResult<Self>;
     fn concat(self, other: Self) -> ValueResult<Self>;
 
@@ -47,6 +48,10 @@ pub trait Value: Clone + From<DataValue> {
     fn div(self, other: Self) -> ValueResult<Self>;
     fn rem(self, other: Self) -> ValueResult<Self>;
 
+    // Saturating arithmetic.
+    fn add_sat(self, other: Self) -> ValueResult<Self>;
+    fn sub_sat(self, other: Self) -> ValueResult<Self>;
+
     // Bitwise.
     fn shl(self, other: Self) -> ValueResult<Self>;
     fn ushr(self, other: Self) -> ValueResult<Self>;
@@ -80,6 +85,7 @@ pub enum ValueTypeClass {
     Integer,
     Boolean,
     Float,
+    Vector,
 }
 
 impl Display for ValueTypeClass {
@@ -88,6 +94,7 @@ impl Display for ValueTypeClass {
             ValueTypeClass::Integer => write!(f, "integer"),
             ValueTypeClass::Boolean => write!(f, "boolean"),
             ValueTypeClass::Float => write!(f, "float"),
+            ValueTypeClass::Vector => write!(f, "vector"),
         }
     }
 }
@@ -225,8 +232,16 @@ impl Value for DataValue {
         }
     }
 
-    fn vector(_v: [u8; 16], _ty: Type) -> ValueResult<Self> {
-        unimplemented!()
+    fn vector(v: [u8; 16], ty: Type) -> ValueResult<Self> {
+        assert!(ty.is_vector() && ty.bytes() == 16);
+        Ok(DataValue::V128(v))
+    }
+
+    fn into_array(&self) -> ValueResult<[u8; 16]> {
+        match *self {
+            DataValue::V128(v) => Ok(v),
+            _ => Err(ValueError::InvalidType(ValueTypeClass::Vector, self.ty())),
+        }
     }
 
     fn convert(self, kind: ValueConversionKind) -> ValueResult<Self> {
@@ -380,6 +395,14 @@ impl Value for DataValue {
         binary_match!(%(&self, &other); [I8, I16, I32, I64])
     }
 
+    fn add_sat(self, other: Self) -> ValueResult<Self> {
+        binary_match!(saturating_add(self, &other); [I8, I16, I32, I64, I128, U8, U16, U32, U64, U128])
+    }
+
+    fn sub_sat(self, other: Self) -> ValueResult<Self> {
+        binary_match!(saturating_sub(self, &other); [I8, I16, I32, I64, I128, U8, U16, U32, U64, U128])
+    }
+
     fn shl(self, other: Self) -> ValueResult<Self> {
         binary_match!(<<(&self, &other); [I8, I16, I32, I64])
     }