Bug 969

Summary: 64-bit variants of setvl, svshape, svstep and svindex
Product: Libre-SOC's first SoC Reporter: Luke Kenneth Casson Leighton <lkcl>
Component: SpecificationAssignee: Luke Kenneth Casson Leighton <lkcl>
Status: CONFIRMED ---    
Severity: enhancement CC: libre-soc-isa, programmerjake
Priority: ---    
Version: unspecified   
Hardware: Other   
OS: Linux   
See Also: https://bugs.libre-soc.org/show_bug.cgi?id=965
NLnet milestone: NLnet.2022-08-051.OPF total budget (EUR) for completion of task and all subtasks: 0
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Bug Blocks: 952    

Description Luke Kenneth Casson Leighton 2022-10-24 01:07:53 BST
the 32 bit variants turn out to be severely under pressure, cf chacha20
needing 3D svshape2.
Comment 1 Jacob Lifshay 2022-10-25 02:53:31 BST
please have bits that are specifically reserved for enabling future regfile extensions, last time setvl had that but you ended up using it for something else, i was eventually ok with that because i figured we could cram those extension bits in the prefix of sv.setvl

if you can reserve 3 bits at minimum, preferably 5-8 bits, that should be good. we'd need 3 bits for a mode and the rest for immediate extension to support larger VL/MAXVL.