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From: Florian Weimer <fw@deneb.enyo.de>
To: <Paul_Koning@Dell.com>
Cc: <gcc@gcc.gnu.org>,  <cfe-dev@lists.llvm.org>,  <sw-dev@groups.riscv.org>
Subject: Re: Spurious register spill with volatile function argument
Date: Mon, 28 Mar 2016 15:10:00 -0000	[thread overview]
Message-ID: <874mbqr64c.fsf@mid.deneb.enyo.de> (raw)
In-Reply-To: <9C15BEC4-998E-40C4-8246-2DE78FF785AB@dell.com> (Paul Koning's	message of "Mon, 28 Mar 2016 14:33:40 +0000")

* Paul Koning:

>> On Mar 28, 2016, at 8:11 AM, Florian Weimer <fw@deneb.enyo.de> wrote:
>> 
>> ...
>> The problem is that “reading” is either not defined, or the existing
>> flatly contradicts existing practice.
>> 
>> For example, if p is a pointer to a struct, will the expression &p->m
>> read *p?
>
> Presumably the offset of m is substantially larger than 0?  If so, my
> answer would be "it had better not".  Does any compiler treat that
> statement as an access to *p ?

As I tried to explain, GCC does, for aliasing purposes.  For the
expression p->m, there is an implicit read of *p, asserting that the
static and dynamic types match.

      reply	other threads:[~2016-03-28 15:10 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <2600D96D-94BC-4259-9D39-DE4993859281@mac.com>
     [not found] ` <9F3C9DE6-F00B-4402-A83B-354455DEAFFA@mac.com>
     [not found]   ` <CA++6G0CK3Yu-w9fhOrvpRP49qz9=Vs20J_=R28Mq=zCJOH+-UA@mail.gmail.com>
2016-03-27  5:58     ` Michael Clark
2016-03-28  9:16       ` Andrew Haley
2016-03-28 12:12         ` Florian Weimer
2016-03-28 14:34           ` Paul_Koning
2016-03-28 15:10             ` Florian Weimer [this message]

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