Re: [PATCH] [RTL] Relax CSE check to set REG_EQUAL notes.

[Jeff Law <law at redhat dot com>]

On 03/09/15 03:53, Steven Bosscher wrote:
> On Wed, Mar 4, 2015 at 12:09 PM, Alex Velenko wrote:
> > For example, in arm testcase pr43920-2.c, CSE previously decided not to put
> > an "obvious" note on insn 9, as set value was the same as note value.
> > At the same time, other insns set up as -1 were set up through a register
> > and did get a note:
>
> ...which is the point of the REG_EQUAL notes. In insn 8 there is a
> REG_EQUAL note to show that the value of r111 is known. In insn 9 the
> known value is, well, known from SET_SRC so there is no need for a
> REG_EQUAL note. Adding REG_EQUAL notes in such cases is just wasteful.
RIght.  I'd rather look into why later passes aren't discovering 
whatever equivalences are important rather than adding the redundant notes.

Regardless, I think this is a gcc-6 issue, so I'm not likely to look at 
it in the immediate future.

jeff