From: Jeff Law <law@redhat.com>
To: Steven Bosscher <stevenb.gcc@gmail.com>,
Alex Velenko <alex.velenko@arm.com>
Cc: GCC Patches <gcc-patches@gcc.gnu.org>,
Marcus Shawcroft <Marcus.Shawcroft@arm.com>
Subject: Re: [PATCH] [RTL] Relax CSE check to set REG_EQUAL notes.
Date: Mon, 09 Mar 2015 17:40:00 -0000 [thread overview]
Message-ID: <54FDDB1C.2000006@redhat.com> (raw)
In-Reply-To: <CABu31nMVShGV0WrECtz64JO3wvY0xuqWy_iDK9b2jVO2LHik3Q@mail.gmail.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
next prev parent reply other threads:[~2015-03-09 17:40 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-04 11:09 Alex Velenko
2015-03-06 12:24 ` Segher Boessenkool
2015-03-09 9:54 ` Steven Bosscher
2015-03-09 17:40 ` Jeff Law [this message]
2015-04-10 9:14 ` Alex Velenko
2015-04-24 1:17 ` Jeff Law
2015-04-24 12:52 ` Alex Velenko
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