wasmtime / issue #6104 Support bitcasting between scalar ... · git-wasmtime

Stream: git-wasmtime

Topic: wasmtime / issue #6104 Support bitcasting between scalar ...

Wasmtime GitHub notifications bot (Mar 27 2023 at 17:25):

Feature

See title. For example v0 = vconst.i64x2 ...; bitcast.i128 little v0.

Benefit

This allows bitcasting between the two without having to go through memory. Cg_clif needs this bitcasting for implementing mem::transmute and float to 128bit int casts on Windows. Currently it has to go through the stack, which is slower and inhibits optimizations.

Wasmtime GitHub notifications bot (Mar 27 2023 at 17:28):

jameysharp labeled issue #6104:

Feature

See title. For example v0 = vconst.i64x2 ...; bitcast.i128 little v0.

Benefit

This allows bitcasting between the two without having to go through memory. Cg_clif needs this bitcasting for implementing mem::transmute and float to 128bit int casts on Windows. Currently it has to go through the stack, which is slower and inhibits optimizations.

Wasmtime GitHub notifications bot (May 23 2024 at 15:13):

afonso360 added the cranelift:E-compiler-easy label to Issue #6104.

Wasmtime GitHub notifications bot (May 23 2024 at 15:21):

afonso360 commented on issue #6104:

This seems like a good starter issue. It currently affects all of our 4 backends.

Here's a test demonstrating the issue:
test compile
target aarch64

function %bitcast_vec_to_int(i64x2) -> i128 {
block0(v0: i64x2):
    v1 = bitcast.i128 little v0
    return v1
}

function %bitcast_int_to_vec(i128) -> i64x2 {
block0(v0: i128):
    v1 = bitcast.i64x2 little v0
    return v1
}
When running this test it fails with: should be implemented in ISLE: inst = v1 = bitcast.i128 little v0, type = Some(types::I128)

Happy to help anyone who wants to try working on this!

Wasmtime GitHub notifications bot (May 23 2024 at 15:21):

afonso360 added the cranelift:area:aarch64 label to Issue #6104.

Wasmtime GitHub notifications bot (May 23 2024 at 15:21):

afonso360 added the cranelift:area:s390x label to Issue #6104.

Wasmtime GitHub notifications bot (May 23 2024 at 15:21):

afonso360 added the cranelift:area:riscv64 label to Issue #6104.

Wasmtime GitHub notifications bot (May 23 2024 at 15:21):

afonso360 added the cranelift:area:x64 label to Issue #6104.

Wasmtime GitHub notifications bot (Oct 05 2024 at 20:39):

aidenfoxivey commented on issue #6104:

@afonso360 It seems like the only remaining part to fix is s390x, right?

Wasmtime GitHub notifications bot (Oct 05 2024 at 20:53):

afonso360 commented on issue #6104:

Yes, I think that's correct

Wasmtime GitHub notifications bot (Oct 05 2024 at 20:55):

aidenfoxivey commented on issue #6104:

Yes, I think that's correct

I'll take a look at how to get a VM running on my ARM MacBook.

Wasmtime GitHub notifications bot (Oct 05 2024 at 20:56):

aidenfoxivey commented on issue #6104:

Maybe I can take on that remaining part.

Wasmtime GitHub notifications bot (Oct 24 2024 at 17:48):

aidenfoxivey commented on issue #6104:

Signed up for one of those LinuxONE servers from IBM, but no response from them so far lol. I dunno whether maybe QEMU is the preferred approach?

Wasmtime GitHub notifications bot (Oct 24 2024 at 17:48):

aidenfoxivey edited a comment on issue #6104:

Signed up for (access/time on) one of those LinuxONE servers from IBM, but no response from them so far lol. I dunno whether maybe QEMU is the preferred approach?

Wasmtime GitHub notifications bot (Oct 24 2024 at 18:00):

afonso360 commented on issue #6104:

QEMU is usually easier for working on different arches. We have a great doc on how to set it up if you're running in Linux

Wasmtime GitHub notifications bot (Oct 24 2024 at 18:12):

aidenfoxivey commented on issue #6104:

QEMU is usually easier for working on different arches. We have a great doc on how to set it up if you're running in Linux

Maybe I'll try to run those in a VM. Unfortunately I'm a Mac person for the time being.

Last updated: Dec 23 2024 at 12:05 UTC