From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Duration for GNAT on ARM
Date: Tue, 23 Dec 2014 23:42:51 +0100
Date: 2014-12-23T23:42:51+01:00 [thread overview]
Message-ID: <14woqdx7yg0ry.eghy2k6aafqc.dlg@40tude.net> (raw)
In-Reply-To: ly7fxi5afe.fsf@pushface.org
On Tue, 23 Dec 2014 21:21:57 +0000, Simon Wright wrote:
> You use -gnatS to get GNAT to output a representation of package
> Standard.
>
> If you do this with a native compiler, you get (typically)
>
> type Duration is delta 0.000000001
> range -((2 ** 63 - 1) * 0.000000001) ..
> +((2 ** 63 - 1) * 0.000000001);
> for Duration'Small use 0.000000001;
>
> However, if I do this with both GNAT GPL 2014 and FSF GCC 4.9.1
> cross-compiling to arm-eabi for the STM32F4 family (Cortex M4), I get
>
> type Duration is delta 0.020
> range -((2 ** 31 - 1) * 0.020) ..
> +((2 ** 31 - 1) * 0.020);
> for Duration'Small use 0.020;
>
> I can understand the 32-bit vs 64-bit part - a misguided attempt at
> efficiency, perhaps - but who gets to say that the clock runs at 50 Hz?
E.g. those who have time source derived from timer interrupts.
> On the STM32's with STMicroelectronics' HAL, the tick is 1 kHz.
But does the RTL assumed by the compiler use this clock?
--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de
next prev parent reply other threads:[~2014-12-23 22:42 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-23 21:21 Duration for GNAT on ARM Simon Wright
2014-12-23 22:42 ` Dmitry A. Kazakov [this message]
2014-12-23 22:52 ` J-P. Rosen
2014-12-24 0:27 ` Simon Wright
2014-12-24 9:40 ` Simon Wright
2014-12-24 0:04 ` Simon Wright
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