Repository navigation
scatter and gather are not strict provenance compatible #271
Description
The implementations of gather and scatter in portable-simd currently are not compatible with strict provenance. Specifically, it is SimdConstPtr::wrapping_add that transmutes a vector of pointers to a vector of integers, does integer arithmetic, and then transmutes back the result. It also has safety comments that are somewhat in conflict with what I am writing in rust-lang/rust#95547. ;)
Reacted by Jubilee
Activity
calebzulawski commentedon Apr 3, 2022
I think this is easy to fix, we just need a new intrinsic for vector pointer offset
RalfJung commentedon Apr 10, 2022
So how would one start fixing this? Add a new
simd_offsetcase around here? Can I just callbx.inbounds_gepwith SIMD types?calebzulawski commentedon Apr 10, 2022
Yeah, that seems right to me. It might also be possible to implement it in
rustc_codegen_ssa?RalfJung commentedon Apr 10, 2022
Are there other SIMD intrinsics that do that that could be used as a template?
calebzulawski commentedon Apr 10, 2022
Hmm, I was thinking offsetting pointers is pretty backend-agnostic but I don't see anything similar. It's probably fine putting it in the LLVM backend with all of the other SIMD intrinsics.
Rollup merge of rust-lang#95961 - RalfJung:gather-scatter, r=workingj…
Rollup merge of rust-lang#95961 - RalfJung:gather-scatter, r=workingj…
Rollup merge of rust-lang#95961 - RalfJung:gather-scatter, r=workingj…
Rollup merge of rust-lang#95961 - RalfJung:gather-scatter, r=workingj…
Rollup merge of rust-lang#95961 - RalfJung:gather-scatter, r=workingj…
Rollup merge of #95961 - RalfJung:gather-scatter, r=workingjubilee
Rollup merge of #95961 - RalfJung:gather-scatter, r=workingjubilee
Rollup merge of #95961 - RalfJung:gather-scatter, r=workingjubilee