From: Richard Earnshaw <rearnsha@arm.com>
To: Julian Brown <julian@codesourcery.com>
Cc: gcc-patches@gcc.gnu.org, paul@codesourcery.com,
Ramana Radhakrishnan <ramana.radhakrishnan@linaro.org>
Subject: Re: [PATCH, ARM] Fix ABI for double-precision helpers on single-float-only CPUs
Date: Thu, 02 Jun 2011 15:35:00 -0000 [thread overview]
Message-ID: <1307028902.17090.6.camel@e102346-lin.cambridge.arm.com> (raw)
In-Reply-To: <20110527173238.630c95b8@rex.config>
On Fri, 2011-05-27 at 17:32 +0100, Julian Brown wrote:
> The helper functions used to implement double-precision arithmetic on
> ARM processors that only support single-precision arithmetic in hardware
> should use the soft-float ABI (i.e. passing and returning floating-point
> arguments in core registers), even when -mfloat-abi=hard is in effect.
> This patch tweaks the ABI for the affected functions so that is true.
>
> Tested with cross to ARM EABI, and by manually observing compiler
> output. We've also been carrying this patch in our local tree for some
> time without issue.
>
> OK to apply?
>
> Thanks,
>
> Julian
>
> ChangeLog
>
> gcc/
> * config/arm/arm.c (arm_libcall_uses_aapcs_base)
> (arm_init_cumulative_args): Use correct ABI for double-precision
> helper functions in hard-float mode if only single-precision
> arithmetic is supported in hardware.
I see Paul has already approved this, but I've just spotted one
potential problem that might cause latent bugs sometime in the future.
The code to register the libcalls is only run once, the first time we
try to look up a libcall. If we ever end up allowing dynamic changing
of CPU and optimization options, not registering the other libcalls will
lead to subtle problems at run time. I suggest that these functions be
unconditionally added along with the other libcalls.
I also don't understand why all the tests are needed in
arm_init_cumulative_args? Surely arm_libcall_uses_aapcs_base() will
already have run that test.
R.
next prev parent reply other threads:[~2011-06-02 15:35 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-27 17:50 Julian Brown
2011-06-02 13:17 ` Paul Brook
2011-06-02 15:35 ` Richard Earnshaw [this message]
2011-06-03 17:41 ` Julian Brown
2011-06-06 16:07 ` Richard Earnshaw
2011-06-14 4:09 ` Ramana Radhakrishnan
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