llvm dev - May 2011 - [LLVMdev] Need advice on writing scheduling pass

hi Jonas,

On Wed, May 25, 2011 at 12:59 AM, Jakob Stoklund Olesen <stoklund at
2pi.dk> wrote:
>
> On May 24, 2011, at 8:22 AM, Jonas Paulsson wrote:
>
>> Hi (Jakob),
>>
>> in reference to the prior message below, I have the following follow-up
questions, as I also need a scheduling pass
>> prior to regalloc. I need to do this in order to set VLIW-flags, so
that the RA is aware of several MI's
>> per cycle with a redefined LiveRange::overlap-function. On a
multiple-issue cycle, a register that gets killed
>> can be reused by another MI - these live ranges do not then overlap.
>
> Redefining overlap() won't work for that. There is other code assuming
that overlap means overlap, for example the LiveIntervalUnion used by the new
register allocators.
>
> For VLIW, you probably want to number your packets instead of individual
instructions. We don't have any VLIW support, so nobody has thought about
how best to do it.
People had discussed VLIW support before, you may have a look at this:
http://old.nabble.com/VLIW-Scheduling-td857833.html

I implemented the VLIW scheduling/register allocate in llvm backend
like the way described in the above thread, and it work without any
problem.

best regards
ether

On May 24, 2011, at 6:46 PM, ether zhhb wrote:
> hi Jonas,
> 
> On Wed, May 25, 2011 at 12:59 AM, Jakob Stoklund Olesen <stoklund at
2pi.dk> wrote:
>> For VLIW, you probably want to number your packets instead of
individual instructions. We don't have any VLIW support, so nobody has
thought about how best to do it.
> 
> People had discussed VLIW support before, you may have a look at this:
> http://old.nabble.com/VLIW-Scheduling-td857833.html
Wow, that's old, but it is still a good way of solving the problem. It is
the easiest way of smuggling packets through regalloc.
> I implemented the VLIW scheduling/register allocate in llvm backend
> like the way described in the above thread, and it work without any
> problem.
I assume you put your VLIW scheduler before the register allocator super-pass?

/jakob

>
> I assume you put your VLIW scheduler before the register allocator
super-pass?
right
>
> /jakob
>
>