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Re: port-hp300/50852: src/sys/arch/hp300/stand/common/ite.c:239: bad expression
The following reply was made to PR port-hp300/50852; it has been noted by GNATS.
From: David Holland <dholland-bugs%netbsd.org@localhost>
Subject: Re: port-hp300/50852: src/sys/arch/hp300/stand/common/ite.c:239: bad
Date: Mon, 29 Feb 2016 15:09:10 +0000
On Sat, Feb 27, 2016 at 06:40:01PM +0000, Joerg Sonnenberger wrote:
> Ironically, for the pre-increment version, it is highly
> likely that no sane compiler ever did not do the correct thing, but
> that's beside the point.
That's not true. A reasonable implementation of pre/post-increment
effects is to write them back at the next sequence point, so you'd get
t1 = whichconsole + 1
t2 = whichconsole + 1
t3 = t2 % (NITE+1)
whichconsole = t3
whichconsole = t1
which after further obvious simplifications turns into
whichconsole = whichconsole + 1
aka The Wrong Thing.
Anyway, regardless of whether you're channeling Dan Pop it's all
irrelevant; code of this form should not be allowed to exist.
David A. Holland
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