3 ms·

You can have an ISA sufficiently generic to run on any CPU, or one sufficiently specific to efficiently exploit SIMD on a particular CPU. Never both. That's why

You can have an ISA sufficiently generic to run on any CPU, or one sufficiently specific to efficiently exploit SIMD on a particular CPU. Never both. That's why some platforms provider higher-level operations, like element-wise multiplication of packed arrays. I can't see whether the actual WASM2 SIMD instructions are sufficiently generic because apparently I'm rate-limited on GitHub (???) and therefore can't see the spec.

flohofwoe 2y ago
https://web.archive.org/web/20250429065033/https://webassembly.github.io/spec/core/syntax/types.html https://web.archive.org/web/20250429065033/https://webassemb... Values are hardwired to 128 bits which can be i8x16/i16x8/i32x4/i64x2 or f32x4/f64x2, so that already limits the 'feature surface' drastically. IMHO as long as it covers the most common use cases (e.g. vec4 / mat4x4 floating point math used in games and a couple of common ALU and bit-twiddling operations on integers) that's already quite a bit better than having to fall back to scalar math.
mdaniel 2y ago
> apparently I'm rate-limited on GitHub (???) and therefore can't see the spec. Are you also on Firefox? I've been getting those 429s a lot over the past week or so. I haven't changed my configuration other than I'm religious about the "check for updates" button, but I cannot imagine a world in which my release-branch browser is a novelty. No proxies, yes I run UBO but it is disabled for GH
- eppsilon 2y ago
  I got some using Orion on iOS yesterday. Same engine as every other iOS browser, so I guess it's sending a user agent GH doesn't like?
ncruces 2y ago
They were sufficient for me to implement most of `string.h` and get speedups between 4 and 16x vs “portable musl C code,” including sophisticated algorithms such as this one: http://0x80.pl/notesen/2016-11-28-simd-strfind.html http://0x80.pl/notesen/2016-11-28-simd-strfind.html I posted about my efforts here: https://news.ycombinator.com/item?id=43935284 https://news.ycombinator.com/item?id=43935284 Or, if you wanna jump to the code: https://github.com/ncruces/go-sqlite3/blob/main/sqlite3/libc/string.h https://github.com/ncruces/go-sqlite3/blob/main/sqlite3/libc...

flohofwoe 2y ago

https://web.archive.org/web/20250429065033/https://webassembly.github.io/spec/core/syntax/types.html https://web.archive.org/web/20250429065033/https://webassemb... Values are hardwired to 128 bits which can be i8x16/i16x8/i32x4/i64x2 or f32x4/f64x2, so that already limits the 'feature surface' drastically. IMHO as long as it covers the most common use cases (e.g. vec4 / mat4x4 floating point math used in games and a couple of common ALU and bit-twiddling operations on integers) that's already quite a bit better than having to fall back to scalar math.

mdaniel 2y ago

> apparently I'm rate-limited on GitHub (???) and therefore can't see the spec. Are you also on Firefox? I've been getting those 429s a lot over the past week or so. I haven't changed my configuration other than I'm religious about the "check for updates" button, but I cannot imagine a world in which my release-branch browser is a novelty. No proxies, yes I run UBO but it is disabled for GH

eppsilon 2y ago
I got some using Orion on iOS yesterday. Same engine as every other iOS browser, so I guess it's sending a user agent GH doesn't like?

ncruces 2y ago

They were sufficient for me to implement most of `string.h` and get speedups between 4 and 16x vs “portable musl C code,” including sophisticated algorithms such as this one: http://0x80.pl/notesen/2016-11-28-simd-strfind.html http://0x80.pl/notesen/2016-11-28-simd-strfind.html I posted about my efforts here: https://news.ycombinator.com/item?id=43935284 https://news.ycombinator.com/item?id=43935284 Or, if you wanna jump to the code: https://github.com/ncruces/go-sqlite3/blob/main/sqlite3/libc/string.h https://github.com/ncruces/go-sqlite3/blob/main/sqlite3/libc...