From: Jeff Law <law@redhat.com>
To: Eric Botcazou <ebotcazou@adacore.com>,
Segher Boessenkool <segher@kernel.crashing.org>
Cc: Bill Schmidt <wschmidt@linux.vnet.ibm.com>,
GCC Patches <gcc-patches@gcc.gnu.org>,
David Edelsohn <dje.gcc@gmail.com>
Subject: Re: [PATCH, rs6000] Fix PR72827 (ada bootstrap failure)
Date: Tue, 06 Sep 2016 21:31:00 -0000 [thread overview]
Message-ID: <3451b7ff-16ac-5da9-cfce-620569501a99@redhat.com> (raw)
In-Reply-To: <9091974.6AZfFVcF36@arcturus.home>
On 08/31/2016 01:08 AM, Eric Botcazou wrote:
>> DSE should really detect this is happening and not do the wrong thing.
>> Maybe add an assert somewhere? Much easier to debug, that way.
>
> That sounds fragile, functions are allowed to fiddle with the frame pointer in
> the prologue or epilogue (but of course not in the body). I think that DSE is
> not the only RTL pass which makes this assumption of invariant frame pointer
> in the body, it seems rather fundamental in the RTL middle-end.
That's my recollection as well -- I recall many patches flying by
through the years that assumed the frame pointer was invariant -- but
they were mostly (all?) in things that ran before we add the
prologue/epilogue to the INSN chain.
jeff
next prev parent reply other threads:[~2016-09-06 21:24 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-31 1:24 Bill Schmidt
2016-08-31 6:20 ` Segher Boessenkool
2016-08-31 7:08 ` Eric Botcazou
2016-08-31 9:07 ` Segher Boessenkool
2016-09-06 21:31 ` Jeff Law [this message]
2016-09-06 23:02 ` Segher Boessenkool
2016-09-07 0:10 ` Jeff Law
2016-08-31 14:00 ` Bill Schmidt
2016-08-31 15:31 ` Eric Botcazou
2016-08-31 16:13 ` Bill Schmidt
2016-08-31 20:07 ` Bill Schmidt
2016-09-01 2:15 ` [PATCH v2, " Bill Schmidt
2016-09-01 7:21 ` Eric Botcazou
2016-09-01 14:32 ` Segher Boessenkool
2016-09-01 14:44 ` Bill Schmidt
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