From: Segher Boessenkool <segher@kernel.crashing.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>,
Uros Bizjak <ubizjak@gmail.com>,
GCC Development <gcc@gcc.gnu.org>, X86 ML <x86@kernel.org>,
Jakub Jelinek <jakub@redhat.com>,
Andy Lutomirski <luto@amacapital.net>,
linux-toolchains@vger.kernel.org,
Christian Borntraeger <borntraeger@de.ibm.com>,
Will Deacon <will@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: typeof and operands in named address spaces
Date: Wed, 11 Nov 2020 18:47:59 -0600 [thread overview]
Message-ID: <20201112004759.GO2672@gate.crashing.org> (raw)
In-Reply-To: <20201110075742.GT2594@hirez.programming.kicks-ass.net>
On Tue, Nov 10, 2020 at 08:57:42AM +0100, Peter Zijlstra wrote:
> On Mon, Nov 09, 2020 at 11:50:15AM -0800, Nick Desaulniers wrote:
> > On Mon, Nov 9, 2020 at 11:46 AM Segher Boessenkool
> > <segher@kernel.crashing.org> wrote:
> > > On Mon, Nov 09, 2020 at 01:47:13PM +0100, Peter Zijlstra wrote:
> > > > C in general does not provide means to strip qualifiers.
> > >
> > > Most ways you can try to use the result are undefined behaviour, even.
> >
> > Yes, removing `const` from a `const` declared variable (via cast) then
> > expecting to use the result is a great way to have clang omit the use
> > from the final program. This has bitten us in the past getting MIPS
> > support up and running, and one of the MTK gfx drivers.
>
> Stripping const to delcare another variable is useful though. Sure C has
> sharp edges, esp. if you cast stuff, but since when did that stop anyone
> ;-)
My point is that removing most qualifiers usually is a problem, so
before doing this, we should think if it is such a good plan, whether
there is a safer / saner solution, etc.
Segher
next prev parent reply other threads:[~2020-11-12 0:51 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-04 18:31 Uros Bizjak
2020-11-05 7:26 ` Richard Biener
2020-11-05 8:56 ` Uros Bizjak
2020-11-05 9:36 ` Alexander Monakov
2020-11-05 10:33 ` Uros Bizjak
2020-11-05 11:38 ` Alexander Monakov
2020-11-05 12:00 ` Uros Bizjak
2020-11-05 12:14 ` Alexander Monakov
2020-11-05 12:24 ` Richard Biener
2020-11-05 12:32 ` Uros Bizjak
2020-11-05 12:35 ` Uros Bizjak
2020-11-05 13:22 ` Alexander Monakov
2020-11-05 13:39 ` Alexander Monakov
2020-11-05 13:46 ` Uros Bizjak
2020-11-05 12:26 ` Uros Bizjak
2020-11-05 15:27 ` Andy Lutomirski
2020-11-05 11:03 ` Uros Bizjak
2020-11-05 9:45 ` Richard Biener
2020-11-05 9:51 ` Jakub Jelinek
2020-11-09 12:47 ` Peter Zijlstra
2020-11-09 19:38 ` Segher Boessenkool
2020-11-09 19:50 ` Nick Desaulniers
2020-11-10 7:57 ` Peter Zijlstra
2020-11-10 18:42 ` Nick Desaulniers
2020-11-10 20:11 ` Peter Zijlstra
2020-11-12 0:40 ` Segher Boessenkool
2020-11-12 0:47 ` Segher Boessenkool [this message]
2020-11-10 7:52 ` Peter Zijlstra
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