Re: [PATCH 2/2 v3][IRA,LRA] Fix PR86939, IRA incorrectly creates an interference between a pseudo register and a hard register

[Peter Bergner <bergner at linux dot ibm dot com>]

On 11/8/18 10:19 AM, Renlin Li wrote:
>> Yes, this is the problem.  We see from the dump, that r2040 does not conflict with
>> hard reg r1:
>>
>> ;; a2040(r1597,l0) conflicts: <list of pseudo regs>
>> ;;     total conflict hard regs:
>> ;;     conflict hard regs:
> I think you should look for axxx(r2040, ..)?
> 
> Maybe I am wrong (not an expert of RA), from what I observed, it is the LRA
> makes the code more complex. It decides to split the live range and spill r2040.
> It creates multiple instructions to reload it.
> r2944 in LRA dump is the register which starts to go wrong. It is assigned as r1.

Yes, IRA and LRA have similar code to compute conflicts.  We need them both to
compute that r2040 (and the reload pseudo(s) generated for it by LRA) conflict
with r1.

Peter