Wasmtime GitHub notifications bot (Aug 10 2022 at 19:35): Wasmtime GitHub notifications bot (Aug 10 2022 at 19:35):uweigand opened PR #4682 from s390x-lane-order to main:
This implements the s390x back-end portion of the solution for
https://github.com/bytecodealliance/wasmtime/issues/4566We now support both big- and little-endian vector lane order
in code generation. The order used for a function is determined
by the function's ABI: if it uses a Wasmtime ABI, it will use
little-endian lane order, and big-endian lane order otherwise.
(This ensures that all raw_bitcast instructions generated by
both wasmtime and other cranelift frontends can always be
implemented as a no-op.)Lane order affects the implementation of a number of operations:
- Vector immediates
- Vector memory load / store (in big- and little-endian variants)
Operations explicitly using lane numbers
(insertlane, extractlane, shuffle, swizzle)Operations implicitly using lane numbers
(iadd_pairwise, narrow/widen, promote/demote, fcvt_low, vhigh_bits)In addition, when calling a function using a different lane order,
we need to lane-swap all vector values passed or returned in registers.A small number of changes to common code were also needed:
Ensure we always select a Wasmtime calling convention on s390x
in crates/cranelift (func_signature).Fix vector immediates for filetests/runtests. In PR #4427,
I attempted to fix this by byte-swapping the V128 value, but
with the new scheme, we'd instead need to perform a per-lane
byte swap. Since we do not know the actual type in write_to_slice
and read_from_slice, this isn't easily possible.Revert this part of PR #4427 again, and instead just mark the
memory buffer as little-endian when emitting the trampoline;
the back-end will then emit correct code to load the constant.Change a runtest in simd-bitselect-to-vselect.clif to no longer
make little-endian lane order assumptions.Remove runtests in simd-swizzle.clif that make little-endian
lane order assumptions by relying on implicit type conversion
when using a non-i16x8 swizzle result type (this feature should
probably be removed anyway).Tested with both wasmtime and cg_clif.
FYI - @cfallin
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Wasmtime GitHub notifications bot (Aug 10 2022 at 20:19):uweigand updated PR #4682 from s390x-lane-order to main.
Wasmtime GitHub notifications bot (Aug 10 2022 at 21:58):uweigand updated PR #4682 from s390x-lane-order to main.
Wasmtime GitHub notifications bot (Aug 11 2022 at 19:10):cfallin submitted PR review.
Wasmtime GitHub notifications bot (Aug 11 2022 at 19:10):cfallin merged PR #4682.
Last updated: Dec 23 2024 at 12:05 UTC