From: Michael Matz <matz@suse.de>
To: Aaron Sawdey <acsawdey@linux.ibm.com>
Cc: gcc@gcc.gnu.org, Joseph Myers <joseph@codesourcery.com>,
Jakub Jelinek <jakub@redhat.com>,
Richard Biener <richard.guenther@gmail.com>,
law@redhat.com,
Segher Boessenkool <segher@kernel.crashing.org>,
David Edelsohn <dje.gcc@gmail.com>,
Bill Schmidt <wschmidt@linux.ibm.com>
Subject: Re: Fixing inline expansion of overlapping memmove and non-overlapping memcpy
Date: Wed, 15 May 2019 13:10:00 -0000 [thread overview]
Message-ID: <alpine.LSU.2.21.1905151302540.8064@wotan.suse.de> (raw)
In-Reply-To: <ee8e07d1-1e34-15e9-1536-161c9c29b3e2@linux.ibm.com>
Hi,
On Tue, 14 May 2019, Aaron Sawdey wrote:
> memcpy -> expand with movmem pattern
> memmove (no overlap) -> transform to memcpy -> expand with movmem pattern
> memmove (overlap) -> remains memmove -> glibc call
...
> However in builtins.c expand_builtin_memmove() does not actually do the
> expansion using the memmove pattern.
Because it can't: the movmem pattern is not defined to require handling
overlaps, and hence can't be used for any possibly overlapping
memmove. (So, in a way the pattern is misnamed and should probably have
been called cpymem from the beginning, alas there we are).
> So here's my proposed set of fixes:
> * Add new optab entries for nonoverlapping_memcpy and overlapping_memmove
> cases.
Wouldn't it be nicer to rename the current movmem pattern to cpymem
wholesale for all ports (i.e. roughly a big s/movmem/cpymem/ over the
whole tree) and then introduce a new optional movmem pattern with
overlapping semantics?
Ciao,
Michael.
next prev parent reply other threads:[~2019-05-15 13:10 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-14 19:21 Aaron Sawdey
2019-05-15 12:23 ` Richard Biener
2019-05-15 13:24 ` Aaron Sawdey
2019-05-15 14:02 ` Michael Matz
2019-05-15 14:11 ` Jakub Jelinek
2019-05-15 14:47 ` Michael Matz
2019-05-15 16:24 ` Aaron Sawdey
2019-05-15 16:31 ` Jakub Jelinek
2019-05-15 17:59 ` Aaron Sawdey
2019-05-15 18:01 ` Jakub Jelinek
2019-05-15 18:03 ` Aaron Sawdey
2019-05-15 13:10 ` Michael Matz [this message]
2019-05-15 13:16 ` Aaron Sawdey
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