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Vector Task Group meeting minutes for 2021/2/19
Date: 2021/02/19
Task Group: Vector Extension Chair: Krste Asanovic Vice-Chair: Roger Espasa Number of Attendees: ~23 Current issues on github: https://github.com/riscv/riscv-v-spec # Next Meeting/Freezing The schedule is to meet again in two weeks (Friday March 5). The plan is to have all pending updates and cleanups in spec by that date, to be able to agree to freeze and move forward into public review (v1.0), which should happen soon after this meeting. Please continue to send PRs for any small typos and clarifications, and use mailing list for larger issues. Issues discussed #640 Bound on VLMAX The major issue raised was that software would otherwise have to cope with indices that might not fit in 16b. The group agreed that profiles and/or platform specs can set the upper bound, with a current recommendation that all profiles limit VLMAX to 64K elements (VLEN=64Kib, or 8K bytes per vector register). The current ISA spec can support larger VLMAX already, but adding vrgatherei32 instruction would be a useful addition (post-v1.0) if architectural vector regfiles >256KiB become common. It was also discussed that a privileged setting will be desired to modulate visible VLEN to support thread migration, or just different application vector profiles with different VLMAX in general. |
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