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Re: [PATCH v2 2/3] Add predict_doloop_p target hook
On Mon, May 20, 2019 at 01:31:10PM -0600, Jeff Law wrote:
> On 5/15/19 10:44 AM, Segher Boessenkool wrote:
> > But we can be allocated a floating point register, or memory, instead.
> > That is heavily discouraged (by making it more expensive), but it can
> > still happen. This is a jump_insn so it cannot get any reloads, either;
> > but even if it could, that is an *expensive* thing to do.
> RIght. ANd that's consistent with what other architectures have needed
> to do. I can't describe the pain of what happens on the PA when you
> find out that the loop counter got allocated to the shift amount
> register or a floating point register. It's rare, but you had to handle
> it. Ugh.
Maybe it's time to finally allow output reloads on jump insns. In LRA
only, if that helps?
Segher