Add Quasi-Fused Multiply-Add/Subtract instructions

Author: Maratyszcza

proposals/simd/BinarySIMD.md

@@ -141,6 +141,8 @@ The `v8x16.shuffle` instruction has 16 bytes after `simdop`.
 | `f32x4.abs`                |    `0x95`| -                  |
 | `f32x4.neg`                |    `0x96`| -                  |
 | `f32x4.sqrt`               |    `0x97`| -                  |
+| `f32x4.qfma`               |    `0x98`| -                  |
+| `f32x4.qfms`               |    `0x99`| -                  |
 | `f32x4.add`                |    `0x9a`| -                  |
 | `f32x4.sub`                |    `0x9b`| -                  |
 | `f32x4.mul`                |    `0x9c`| -                  |
@@ -150,6 +152,8 @@ The `v8x16.shuffle` instruction has 16 bytes after `simdop`.
 | `f64x2.abs`                |    `0xa0`| -                  |
 | `f64x2.neg`                |    `0xa1`| -                  |
 | `f64x2.sqrt`               |    `0xa2`| -                  |
+| `f64x2.qfma`               |    `0xa3`| -                  |
+| `f64x2.qfms`               |    `0xa4`| -                  |
 | `f64x2.add`                |    `0xa5`| -                  |
 | `f64x2.sub`                |    `0xa6`| -                  |
 | `f64x2.mul`                |    `0xa7`| -                  |

proposals/simd/SIMD.md

@@ -778,6 +778,18 @@ Lane-wise IEEE `multiplication`.
 
 Lane-wise IEEE `squareRoot`.
 
+### Quasi-Fused Multiply-Add
+* `f32x4.qfma(a: v128, b: v128, c: v128) -> v128`
+* `f64x2.qfma(a: v128, b: v128, c: v128) -> v128`
+
+Lane-wise multiplication and addition (`a + b * c`), either with, or without intermediate rounding. WebAssembly implementation may execute this instruction as either IEEE Fused-Multiply-Add (FMA) or a combination of IEEE `multiplication` and IEEE `addition` operations, depending on availability and performance of FMA instruction on the target native platform. `qfma` instructions in a WebAssembly module must execute as either all fused, or all unfused operations.
+
+### Quasi-Fused Multiply-Subtract
+* `f32x4.qfms(a: v128, b: v128, c: v128) -> v128`
+* `f64x2.qfms(a: v128, b: v128, c: v128) -> v128`
+
+Lane-wise multiplication and subtraction (`a - b * c`), either with, or without intermediate rounding. WebAssembly implementation may execute this instruction as either IEEE Fused-Multiply-Subtract (FMS) or a combination of IEEE `multiplication` and IEEE `subtraction` operations, depending on availability and performance of FMS instruction on the target native platform. `qfms` instructions in a WebAssembly module must execute as either all fused, or all unfused operations.
+
 ## Conversions
 ### Integer to floating point
 * `f32x4.convert_i32x4_s(a: v128) -> v128`