[PATCH] regrename: Fix -fcompare-debug issue in check_new_reg_p [PR105041]

[Jeff Law]

On 6/10/2022 9:40 AM, Segher Boessenkool wrote:
> Hi!
>
> On Fri, Jun 10, 2022 at 07:52:57PM +0530, Surya Kumari Jangala wrote:
>> In check_new_reg_p, the nregs of a du chain is computed by obtaining the MODE
>> of the first element in the chain, and then calling hard_regno_nregs() with the
>> MODE. But the first element of the chain can be a DEBUG_INSN whose mode need
>> not be the same as the rest of the elements in the du chain. This
>> was resulting in fcompare-debug failure as check_new_reg_p was returning a
>> different result with -g for the same candidate register. We can instead obtain
>> nregs from the du chain itself.
> Great, thanks for finding and fixing this!  I cannot approve it, you'll
> have to wait for someone who can.  It looks fine to me, but that does
> not mean so much in regrename.c :-)
I'll go ahead and ACK the regrename bits.  So as soon as you're happy 
with the testsuite bits, this is good to go.

jeff