Mill Computing, Inc. Forums The Mill Architecture Grab bag of questions Reply To: Grab bag of questions

Ivan Godard
Post count: 656

– 12) Any plans for over-128-bits SIMD?
The problem with wide SIMD is that the belts position widths must match the widest possible, which is wasteful for the vast majority of code that won’t use it, or we would need to have multiple belts of differing element widths with the concomitant hassles of multiple ops/transfer move instructions/etc. that plague the legacy ISAs with multiple register widths. We have pretty much settled that SIMD in a member will only be to the widest scalar width, and further parallelism will be provided by wider pipes.

As an aside: auto-SIMD with the same semantics as scalar has been ten years away for a very long time. It is worst when the code does something unexpected, like overflow. At least on a Mill you will get the same answer SIMD or scalar; good luck on legacy ISAs.