[Libre-soc-bugs] [Bug 561] fail-first gather/scatter LD/ST means "strided"

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Thu Sep 2 20:06:07 BST 2021


https://bugs.libre-soc.org/show_bug.cgi?id=561

--- Comment #4 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
(In reply to Jacob Lifshay from comment #3)
> (In reply to Jacob Lifshay from comment #2)
> > strided load would mean something like:
> > 
> > for(i = 0; i < VL; i++)
> >     reg[rt + i] = mem[reg[ra] + i * imm];
> 
> we will want imm to be signed

that's an immediate variant - RA(D) - which is
already covered and separate and distinct from
Indexed variant (RA + RB).

it's looking like this one's an invalid bugreport
because ffirst *indexed* was supposed to be banned,
then used for sonething else, but it cannot be
an immediate-strided instruction because there is
no immediate.

it *could* however be used for

for(i = 0; i < VL; i++)
   reg[rt + i] = mem[reg[ra] + i * reg[rb]];

as long as RB is a scalar.

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