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| author | Dan Gohman <sunfish@mozilla.com> | 2020-02-26 18:30:43 -0800 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2020-02-26 18:30:43 -0800 |
| commit | ccbac15a287fa2af4a3db882d950db442011a7b1 (patch) | |
| tree | 65a9bf05926713284bc5c6ee313f52b56d76bebc /BinaryEncoding.md | |
| parent | d4e7f960c5e3f3788531147e4ea4ed23eb507c02 (diff) | |
| download | nanowasm-design-ccbac15a287fa2af4a3db882d950db442011a7b1.tar.gz | |
Define non-trapping float-to-int conversions. (#1089)
* Define non-trapping float-to-int conversions.
This also introduces the concept of prefix bytes, and defines the "numeric" prefix
byte, used for encodin the new conversion instructions.
* Add feature markers.
* Add the feature marker in more places.
* Rename "numeric" to "misc".
See https://github.com/WebAssembly/nontrapping-float-to-int-conversions/issues/5.
* Rename opcodes.
See https://github.com/WebAssembly/spec/issues/884#issuecomment-426433329.
Diffstat (limited to 'BinaryEncoding.md')
| -rw-r--r-- | BinaryEncoding.md | 28 |
1 files changed, 22 insertions, 6 deletions
diff --git a/BinaryEncoding.md b/BinaryEncoding.md index f0ec70f..6edacc8 100644 --- a/BinaryEncoding.md +++ b/BinaryEncoding.md @@ -57,12 +57,20 @@ Note: Currently, the only sizes used are `varint7`, `varint32` and `varint64`. ## Instruction Opcodes -In the MVP, the opcodes of [instructions](Semantics.md) are all encoded in a -single byte since there are fewer than 256 opcodes. Future features like -[SIMD][future simd] and [atomics][future threads] -will bring the total count above 256 and so an extension scheme will be -necessary, designating one or more single-byte values as prefixes for multi-byte -opcodes. +The opcodes for many common instructions are encoded in a single byte. + +The opcodes for some families of instructions are encoded as a *prefix byte* +followed by an LEB128 value. Prefix byte values are allocated starting at `0xfe` +and counting downwards. + +### Prefix Bytes + +| Opcode | Name | Description | +| ------ | -------- | ----------- | +| `0xff` | reserved | Reserved for unknown future language evolution :milky_way: | +| `0xfe` | threads | Expected to be used for [atomics :unicorn:][future threads] | +| `0xfd` | simd | Expected to be used for [SIMD :unicorn:][future simd] | +| `0xfc` | misc | Miscellaneous operations :bowling: | ## Language Types @@ -802,6 +810,14 @@ for [future :unicorn:][future multiple tables] use and must be 0 in the MVP. | `f64.convert_s/i64` | `0xb9` | | | | `f64.convert_u/i64` | `0xba` | | | | `f64.promote/f32` | `0xbb` | | | +| `i32.trunc_sat_f32_s` | `0xfc` `0x00` | | :bowling: saturating form of `i32.trunc_f32_s` | +| `i32.trunc_sat_f32_u` | `0xfc` `0x01` | | :bowling: saturating form of `i32.trunc_f32_u` | +| `i32.trunc_sat_f64_s` | `0xfc` `0x02` | | :bowling: saturating form of `i32.trunc_f64_s` | +| `i32.trunc_sat_f64_u` | `0xfc` `0x03` | | :bowling: saturating form of `i32.trunc_f64_u` | +| `i64.trunc_sat_f32_s` | `0xfc` `0x04` | | :bowling: saturating form of `i64.trunc_f32_s` | +| `i64.trunc_sat_f32_u` | `0xfc` `0x05` | | :bowling: saturating form of `i64.trunc_f32_u` | +| `i64.trunc_sat_f64_s` | `0xfc` `0x06` | | :bowling: saturating form of `i64.trunc_f64_s` | +| `i64.trunc_sat_f64_u` | `0xfc` `0x07` | | :bowling: saturating form of `i64.trunc_f64_u` | ## Reinterpretations ([described here](Semantics.md#datatype-conversions-truncations-reinterpretations-promotions-and-demotions)) |