[Libre-soc-isa] [Bug 924] potential major opcode allocation for SVP64

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=924

--- Comment #21 from Jacob Lifshay <programmerjake at gmail.com> ---
(In reply to Jacob Lifshay from comment #20)
> (In reply to Luke Kenneth Casson Leighton from comment #19)
> > appreciated - unless there is a really *really* good reason i am
> > not going to worry about it.  first reason: breaking up the 24-bits
> > of SVRM starts to interfere with XO (in other encodings).

just now realized you were talking about the XO field, not XO form. regardless,
the example encoding resolves those issues afaict:

> example encoding scheme (just complete enough to illustrate my point):
> space saving measures: EXT2xx is half the size, XO is much larger in fli
> than usual
> prefix:
> |0  |6   |11  |13 |16  |21  |22  |28 |29 |30      |31  |32 |
> | 9 | SVRM[0:21]                 | 0 | 0 | SVRM[22:23] | - | SVP64 ext0xx
> | 9 | SVRM[0:21]                 | 0 | 1 | SVRM[22:23] | - | SVP64Single ext0xx
> | 9 | SVRM[0:21]                 | 1 | 0 | SVRM[22:23] | 0 | SVP64 ext2xx
> | 9 | SVRM[0:21]                 | 1 | 0 | SVRM[22:23] | 1 | SVP64Single ext2xx
> | 9 | -                          | 1 | 1 | -               | scalar 32/64-bit
> | 9 | RT | RA     | RB | OE | XO | 1 | 1 | XO     | Rc |   | XO-form 32-bit
> | 9 | RT | RA     | RB | XO      | 1 | 1 | XO     | Rc |   | X-form 32-bit
> | 9 | RS | RA     | sh | XO      | 1 | 1 | sh     | Rc |   | XS-form 32-bit
> | 9 |FRT |mode| XO               | 1 | 1 | XO          |imm| fli 64-bit

-- 
You are receiving this mail because:
You are on the CC list for the bug.