[RFC][PATCH] Preferred rename register in regrename pass
Bernd Schmidt
bschmidt@redhat.com
Tue Nov 10 22:57:00 GMT 2015
On 11/10/2015 11:33 PM, Robert Suchanek wrote:
>
> The reason behind the failures is that the terminated_this_insn had
> a different number of consecutive registers (and mode) to the input
> operand in a move currently being considered for tying. In the fix,
> I allow tying only if there is matching number of NREGS.
>
> Bernd, do you think that this check would be sufficient and safe?
> I'm not sure what would be better: check the mode, nregs plus perhaps
> consider tying only if nregs == 1.
Hmm, but shouldn't the regno still be the same? Or is this a case where
we have a multi-word chain like ax/dx and then something like a "set bx,
dx" involving only a part of it, but the entire chain dies?
I guess this is ok to stop the failures for now, but you may want to
move the check to the point where we set terminated_this_insn. Also, as
I pointed out earlier, clearing terminated_this_insn should probably
happen earlier.
Bernd
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