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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 /Semantics.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 'Semantics.md')
| -rw-r--r-- | Semantics.md | 23 |
1 files changed, 22 insertions, 1 deletions
diff --git a/Semantics.md b/Semantics.md index aa0ed9f..ae6db70 100644 --- a/Semantics.md +++ b/Semantics.md @@ -35,6 +35,14 @@ detailed in this document. [:unicorn:][future general] = Planned [future][future general] feature +## Post-MVP Features + +Some features were added post-MVP. These are indicated with the following symbols: + +| Symbol | Feature | +| ---------- | ------- | +| :bowling: | Saturating float to int conversions | + ## Traps Some operators may *trap* under some conditions, as noted below. In the MVP, @@ -640,6 +648,14 @@ is NaN, and *ordered* otherwise. * `f64.convert_u/i32`: convert an unsigned 32-bit integer to a 64-bit float * `f64.convert_u/i64`: convert an unsigned 64-bit integer to a 64-bit float * `f64.reinterpret/i64`: reinterpret the bits of a 64-bit integer as a 64-bit float + * `i32.trunc_sat_f32_s`: :bowling: truncate a 32-bit float to a signed 32-bit integer with saturation + * `i32.trunc_sat_f64_s`: :bowling: truncate a 64-bit float to a signed 32-bit integer with saturation + * `i32.trunc_sat_f32_u`: :bowling: truncate a 32-bit float to an unsigned 32-bit integer with saturation + * `i32.trunc_sat_f64_u`: :bowling: truncate a 64-bit float to an unsigned 32-bit integer with saturation + * `i64.trunc_sat_f32_s`: :bowling: truncate a 32-bit float to a signed 64-bit integer with saturation + * `i64.trunc_sat_f64_s`: :bowling: truncate a 64-bit float to a signed 64-bit integer with saturation + * `i64.trunc_sat_f32_u`: :bowling: truncate a 32-bit float to an unsigned 64-bit integer with saturation + * `i64.trunc_sat_f64_u`: :bowling: truncate a 64-bit float to an unsigned 64-bit integer with saturation Wrapping and extension of integer values always succeed. Promotion and demotion of floating point values always succeed. @@ -665,7 +681,12 @@ round-to-nearest ties-to-even rounding. Truncation from floating point to integer where IEEE 754-2008 would specify an invalid operator exception (e.g. when the floating point value is NaN or -outside the range which rounds to an integer in range) traps. +outside the range which rounds to an integer in range) is handled as follows: + - For instructions with no exceptional behavior specified, a trap is produced. + - :bowling: For instructions containing `_sat`, no trap is produced, and: + - If the floating-point value is positive, the maximum integer value is returned. + - If the floating-point value is negative, the minimum integer value is returned. + - If the floating-point value is NaN, zero is returned. ## Type-parametric operators |