i64x4.widen_(low/high)_i32x8_(s/u) instructions

Author: Maratyszcza

proposals/simd/BinarySIMD.md

@@ -188,6 +188,10 @@ For example, `ImmLaneIdx16` is a byte with values in the range 0-15 (inclusive).
 | `i64x2.add`                |    `0xce`| -                  |
 | `i64x2.sub`                |    `0xd1`| -                  |
 | `i64x2.mul`                |    `0xd5`| -                  |
+| `i64x2.widen_low_i32x4_s`  |     `TBD`| -                  |
+| `i64x2.widen_high_i32x4_s` |     `TBD`| -                  |
+| `i64x2.widen_low_i32x4_u`  |     `TBD`| -                  |
+| `i64x2.widen_high_i32x4_u` |     `TBD`| -                  |
 | `f32x4.ceil`               |    `0xd8`| -                  |
 | `f32x4.floor`              |    `0xd9`| -                  |
 | `f32x4.trunc`              |    `0xda`| -                  |

proposals/simd/ImplementationStatus.md

@@ -156,6 +156,10 @@
 | `i64x2.add`                |               `-msimd128` | :heavy_check_mark: |                    |                    | :heavy_check_mark: |
 | `i64x2.sub`                |               `-msimd128` | :heavy_check_mark: |                    |                    | :heavy_check_mark: |
 | `i64x2.mul`                |               `-msimd128` | :heavy_check_mark: |                    |                    | :heavy_check_mark: |
+| `i64x2.widen_low_i32x4_s`  |                           |                    |                    |                    |                    |
+| `i64x2.widen_high_i32x4_s` |                           |                    |                    |                    |                    |
+| `i64x2.widen_low_i32x4_u`  |                           |                    |                    |                    |                    |
+| `i64x2.widen_high_i32x4_u` |                           |                    |                    |                    |                    |
 | `f32x4.abs`                |               `-msimd128` | :heavy_check_mark: |                    |                    | :heavy_check_mark: |
 | `f32x4.neg`                |               `-msimd128` | :heavy_check_mark: |                    |                    | :heavy_check_mark: |
 | `f32x4.sqrt`               |               `-msimd128` | :heavy_check_mark: |                    |                    | :heavy_check_mark: |

proposals/simd/SIMD.md

@@ -996,6 +996,10 @@ def S.narrow_T_u(a, b):
 * `i32x4.widen_high_i16x8_s(a: v128) -> v128`
 * `i32x4.widen_low_i16x8_u(a: v128) -> v128`
 * `i32x4.widen_high_i16x8_u(a: v128) -> v128`
+* `i64x2.widen_low_i32x4_s(a: v128) -> v128`
+* `i64x2.widen_high_i32x4_s(a: v128) -> v128`
+* `i64x2.widen_low_i32x4_u(a: v128) -> v128`
+* `i64x2.widen_high_i32x4_u(a: v128) -> v128`
 
 Converts low or high half of the smaller lane vector to a larger lane vector,
 sign extended or zero (unsigned) extended.