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Re: Ping : [PATCH] [gcc, combine] PR46164: Don't combine the insns if a volatile register is contained.


On 02/12/15 15:15, Segher Boessenkool wrote:
On Thu, Feb 12, 2015 at 03:54:21PM +0000, Richard Sandiford wrote:
"Hale Wang" <hale.wang@arm.com> writes:
Ping?

It's not a regression (or is it?), so it is not appropriate for stage4.
That's the big question, of course.

[ INSN can never be an asm, that is already refused by can_combine_p. ]

We do not guarantee things will end up in the specified reg (except for asm),
but will it hurt to leave things in the reg the user said it should be in, even
if we do not guarantee this behaviour?
I doubt it could hurt except in extreme corner cases where the value gets used later in some insn where the user register was inappropriate. That will cause a spill to copy from the user register to a scratch of the appropriate type.

That's, of course, if I'm reading this correctly...

jeff



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