This instruction is only available when the jsconv target_feature is available,
so on ARMv8.3 or higher.
It is used e.g. by Ruffle[0] to speed up its conversion from f64 to i32, or by
any JS engine probably.
I’ve picked the stdarch_aarch64_jscvt feature because it’s the name of the
FEAT_JSCVT, but hesitated with naming it stdarch_aarch64_jsconv (the name of
the target_feature) or stdarch_aarch64_jcvt (the name of the C intrinsic) or
stdarch_aarch64_fjcvtzs (the name of the instruction), this choice is purely
arbitrary and I guess it could be argued one way or another. I wouldn’t expect
it to stay unstable for too long, so ultimately this shouldn’t matter much.
This feature is now tracked in this issue[1].
[0] https://github.com/ruffle-rs/ruffle/pull/21780
[1] https://github.com/rust-lang/rust/issues/147555
This involves moving from the ACLE intrinsic definitions (which aren't
available for SVE at this point) to a JSON file. This was derived from
ARM's documentation[^1], and then relicensed under `MIT OR Apache-2.0` for
use in this repository.
[^1]: https://developer.arm.com/architectures/instruction-sets/intrinsics
