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Re: [PATCH] handle bzero/bcopy in DSE and aliasing (PR 80933, 80934)

On 06/07/2017 02:01 PM, Marc Glisse wrote:
On Wed, 7 Jun 2017, Bernhard Reutner-Fischer wrote:

On 7 June 2017 16:46:53 CEST, Martin Sebor <> wrote:
On 06/07/2017 02:23 AM, Richard Biener wrote:
On Wed, Jun 7, 2017 at 5:26 AM, Martin Sebor <>
Note I'd be _much_ more sympathetic to simply canonicalizing all of
bzero and bcopy
to memset / memmove and be done with all the above complexity.

Attached is an updated patch along these lines.  Please let me
know if it matches your expectations.

I think you attached the wrong patch.

Yes I did, sorry.  The correct one is attached.

Under POSIX.1-2008 "optimizing" bzero or bcmp is IMO plain wrong.

It's like optimizing foo() to a random built-in but maybe that's just
me. If your libc provides a define to a standard function for these
under a compat knob then fine but otherwise you should fix that.
*shrug*. Joseph?

The patch optimizes __builtin_bzero, which should be ok. The question
(independent from this patch) is then under what conditions bzero should
be detected as a builtin.

Yes.  The problem is that unlike for C and C++, GCC doesn't have
a mechanism to select the target version of POSIX.  I think it

But there is a subtle problem with the patch that needs fixing.
Bcopy should not be transformed to memcpy but rather memmove.
I'll fix that before committing.


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