On 2/22/15 08:25, Chris Metcalf wrote:
> On 2/21/2015 7:25 PM, Chen Gang S wrote:
>> On 2/22/15 00:33, Richard Henderson wrote:
>>> >On 02/21/2015 07:31 AM, Chen Gang S wrote:
>>>> >>
>>>> >> - We can still use the original pipes order: "y0, y2, y1" and "x0, x1".
>>> >
>>> >I guess, sure, though I don't think that'll help as much as you imagine.
>>> >
>>>
>> OK, thanks. For me, your idea is OK, it is more simpler (although with
>> more tcg temporary variables).
>
> Richard pretty much said all I wanted to say, but I just wanted to reinforce
> that the semantics of the multiple pipes is always "all together".
OK, thanks.
> So if you
> have
> { move r1, r2; move r2, r1 } then that swaps r1 and r2.
So the first pipe must have temporary variable.
> Or if you have
> { ld r1, sp; jrp r1 } then you are restoring r1 but jumping to wherever its
> previous value said you needed to go. Etc.
Excuse me, I am not quite sure whether ld/st can be in pipe x0, y0, or
y1.
But I guess your meaning is that y2 must have temporary variable, or it
will cause issue.
> Similarly, if any pipeline takes an exception (a TLB fault from a memory op,
> a GPV fault from an illegal mfspr, etc) then no pipeline completes its action.
>
Oh, really !! And I guess, Richard's code can not be sure of it: memory
write operand (e.g st) is not buffered. If what I guess is correct, for
me, it is not quite easy to fix this issue.
I also guess, at present, we need think of more before continue.
Thanks.
--
Chen Gang
Open, share, and attitude like air, water, and life which God blessed
