From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: GNAT 4.8 atomic access to 64-bit objects
Date: Fri, 15 Nov 2013 22:33:37 +0100
Date: 2013-11-15T22:33:37+01:00 [thread overview]
Message-ID: <ap60v90ea1hu$.hagui2l6id62.dlg@40tude.net> (raw)
In-Reply-To: 52867527$0$9504$9b4e6d93@newsspool1.arcor-online.net
On Fri, 15 Nov 2013 20:25:28 +0100, Georg Bauhaus wrote:
> On 15.11.13 09:44, Dmitry A. Kazakov wrote:
>> On Thu, 14 Nov 2013 21:34:26 +0100, Ludovic Brenta wrote:
>
>>> I'd suggest you use 64-bit floating-point registers instead; i386
>>> processors have them, I think. That has been a useful trick for a
>>> decade or so :)
>>
>> Using unchecked union or unchecked conversion?
>
> FTR, a different 32 bit implementation (Ada 95) does not support a binary
> modulus of 64, and also, while Unchecked_Conversion passes the value 42
> from an integer register to a FPT register and back as 42, idly trying
> type Fake is new Long_Float;
> pragma Atomic (Fake);
> gives
> LRM:C.6(10), Indivisible read/update not supported for given subtype, pragma Atomic ignored
Try this:
with Interfaces;
with Ada.Unchecked_Conversion;
with Ada.Text_IO;
procedure Test is
type T is mod 2**64;
type Atomic_T is new Interfaces.IEEE_Float_64;
function Load is new Ada.Unchecked_Conversion (Atomic_T, T);
function Store is new Ada.Unchecked_Conversion (T, Atomic_T);
X : Atomic_T;
pragma Atomic (X);
begin
X := Store (123);
Ada.Text_IO.Put_Line (T'Image (Load (X)));
X := Store (Load (X) + 1);
Ada.Text_IO.Put_Line (T'Image (Load (X)));
end Test;
The code generated looks horrific.
--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de
next prev parent reply other threads:[~2013-11-15 21:33 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-14 15:57 GNAT 4.8 atomic access to 64-bit objects Dmitry A. Kazakov
2013-11-14 20:34 ` Ludovic Brenta
2013-11-15 8:44 ` Dmitry A. Kazakov
2013-11-15 19:25 ` Georg Bauhaus
2013-11-15 21:33 ` Dmitry A. Kazakov [this message]
2013-11-16 10:08 ` Georg Bauhaus
2013-11-16 12:02 ` Dmitry A. Kazakov
2013-11-15 19:08 ` Stefan.Lucks
2013-11-15 21:19 ` Dmitry A. Kazakov
2013-11-22 0:30 ` Randy Brukardt
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