[Libre-soc-bugs] [Bug 1068] add instructions from ls012 not currently implemented in binutils

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Thu Apr 27 13:33:00 BST 2023


--- Comment #5 from Dmitry Selyutin <ghostmansd at gmail.com> ---
(In reply to Luke Kenneth Casson Leighton from comment #4)
> (In reply to Dmitry Selyutin from comment #3)
> > I'm lost a bit between the list above and list here:
> > https://git.libre-soc.org/?p=libreriscv.git;a=commitdiff;
> > h=1612a779c718fef1bec4f0384d4121119665f32e.
> > 
> > I counted all additions (+ in patch), and got me 172 instructions. Do we
> > intend to cover all of them in this task? 
> no absolutely not. i've already pre-filtered them.

OK, so I need to go through list at
https://bugs.libre-soc.org/show_bug.cgi?id=1068#c2 and fix flags, right? More
on the flags below.

>  although it looked
> like i did it "quick" so it's good to ask, i did it "quick" because
> (a) i have been keeping an eye on this for months and (b) i'm on a
> deadline.

Ah no, actually my suspicions were based on a simpler ground: comment here
predates the comment in another task. So I suspected the more recent one is the
one I should consider most. :-)

> > Also, a question of DRAFTFFS flag. Am I right that I need to filter
> > instructions marked with "FFS" in "level" section of optable.csv?
> no. it's literally a replace "SVP64" flag with "DRAFT_SFFS" in ppc_opc.c
> (because they're *all* Scalar SFFS instructions).

Ah, my bad. I thought that we need only consider stuff with SFFS in level
column, and considered things like setvl or svstep or svremap being marked as
`PPC_OPCODE_SVP64`. If not, I don't even understand when we need
`PPC_OPCODE_SVP64`, other than checking that some instructions start with "sv."
in asm and disassembly magically handles the prefix.
Please confirm if the latter statement is correct. :-)

> > Do we need other flags?
> not right now.

So, if I understand correctly, -mlibresoc activates both PPC_OPCODE_SVP64 and
PPC_OPCODE_DRAFT_SFFS (perhaps both should be called "draft").
PPC_OPCODE_DRAFT_SFFS can also be activated via -mdraft-sffs.
Should we also have -mdraft-svp64 which activates PPC_OPCODE_DRAFT_SVP64 but

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