From: Segher Boessenkool <segher@kernel.crashing.org>
To: Dimitar Dimitrov <dimitar@dinux.eu>
Cc: Christophe Lyon <christophe.lyon@linaro.org>,
Thomas Preudhomme <thomas.preudhomme@linaro.org>,
gcc Patches <gcc-patches@gcc.gnu.org>,
Richard Sandiford <richard.sandiford@arm.com>,
"Thomas Preud'homme" <thomas.preudhomme@arm.com>
Subject: Re: [PATCH] [RFC] PR target/52813 and target/11807
Date: Thu, 13 Dec 2018 14:49:00 -0000 [thread overview]
Message-ID: <20181213144837.GD3803@gate.crashing.org> (raw)
In-Reply-To: <4591520.WeSID5Fo3g@tpdeb>
On Wed, Dec 12, 2018 at 06:26:10PM +0200, Dimitar Dimitrov wrote:
> I expect that if I mark a HW register as "clobber", compiler would save its
> contents before executing the asm statement, and after that it would restore
> its contents. This is the GCC behaviour for all but the SP and PIC registers.
> That is why I believe that PR52813 is a valid bug.
It won't do it for *any* fixed registers. But you do not want to error
or even warn for some fixed registers, for example the "flags" register
on x86 is *always* written to by asm.
But you never want to warn for non-fixed registers, and e.g.
PIC_OFFSET_TABLE_REGNUM isn't always a fixed register (when flag_pic is 0
for example).
> I'm not sure how GCC could recover if SP is clobbered. If SP is clobbered in
> such a way that GCC will not notice (e.g. thread switching), then why should
> GCC know about it in the first place?
Up until today, GCC has always just ignored it if you claimed to clobber
the stack pointer.
Segher
next prev parent reply other threads:[~2018-12-13 14:49 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-09 10:09 Dimitar Dimitrov
2018-12-10 11:21 ` Richard Sandiford
2018-12-10 19:36 ` Dimitar Dimitrov
2018-12-11 15:52 ` Richard Sandiford
2018-12-12 9:42 ` Christophe Lyon
2018-12-12 10:03 ` Christophe Lyon
2018-12-12 16:39 ` Dimitar Dimitrov
2018-12-12 10:30 ` Thomas Preudhomme
2018-12-12 11:21 ` Thomas Preudhomme
2018-12-12 13:19 ` Christophe Lyon
2018-12-12 15:13 ` Christophe Lyon
2018-12-12 15:35 ` Thomas Preudhomme
2018-12-12 16:26 ` Dimitar Dimitrov
2018-12-13 14:49 ` Segher Boessenkool [this message]
2018-12-13 22:21 ` Dimitar Dimitrov
2018-12-14 8:52 ` Segher Boessenkool
2018-12-16 8:43 ` Dimitar Dimitrov
2018-12-17 15:23 ` Segher Boessenkool
2018-12-14 13:49 ` Richard Sandiford
2018-12-15 15:38 ` Segher Boessenkool
2018-12-12 11:24 ` Andreas Schwab
2018-12-16 14:36 Bernd Edlinger
2018-12-16 16:14 ` Dimitar Dimitrov
2018-12-17 11:47 ` Richard Sandiford
2018-12-17 12:54 ` Christophe Lyon
2018-12-17 13:35 ` Richard Sandiford
2018-12-17 13:42 ` Christophe Lyon
2018-12-17 14:05 ` Bernd Edlinger
2018-12-17 14:10 ` Bernd Edlinger
2018-12-17 15:55 ` Segher Boessenkool
2018-12-17 18:46 ` Richard Sandiford
2018-12-17 20:15 ` Bernd Edlinger
2018-12-19 6:40 ` Dimitar Dimitrov
2018-12-19 9:29 ` Segher Boessenkool
2018-12-18 14:16 ` Bernd Edlinger
2018-12-18 15:14 ` Bernd Edlinger
2019-01-07 9:23 ` Jakub Jelinek
2019-01-07 21:51 ` Bernd Edlinger
2019-01-08 12:03 ` Richard Sandiford
2019-01-10 13:21 ` Segher Boessenkool
2019-01-10 21:23 ` Richard Sandiford
2019-01-10 21:26 ` Jakub Jelinek
2019-01-10 21:56 ` Richard Sandiford
2019-01-11 12:26 ` Segher Boessenkool
2019-01-10 22:32 ` Bernd Edlinger
2019-01-11 12:18 ` Segher Boessenkool
2019-01-11 12:23 ` Richard Sandiford
2019-01-11 22:59 ` Jeff Law
2019-01-17 14:27 ` Christophe Lyon
2019-01-18 9:49 ` Richard Sandiford
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