From: Vadim Godunko <vgodunko@gmail.com>
Subject: Re: highest bit, statically determined
Date: Sun, 30 Sep 2012 08:01:54 -0700 (PDT)
Date: 2012-09-30T08:01:54-07:00 [thread overview]
Message-ID: <b81d4661-16cc-4f09-a6f5-82c68f5c0bef@googlegroups.com> (raw)
In-Reply-To: <506769fb$0$6580$9b4e6d93@newsspool3.arcor-online.net>
On Sunday, September 30, 2012 1:37:00 AM UTC+4, Georg Bauhaus wrote:
>
> Daringly, I have tried to steal the idea and try a comparison (out of
> curiosity, not for the static thing). GCC performs simple tail call
> elimination (explaining the Shift parameter)!
>
If you don't need static function, you can use following function (GCC can precompute its result for static value):
with Interfaces.C; use Interfaces.C;
function Bit (X : Unsigned) return Unsigned;
pragma Inline (Bit);
function Bit (X : Unsigned) return Unsigned is
function CLZ (X : Unsigned) return Unsigned;
pragma Import (Intrinsic, CLZ, "__builtin_clz");
begin
if X = 0 then
-- XXX Return what you want.
return 0;
else
return Unsigned'Size - CLZ (X);
end if;
end Bit;
next prev parent reply other threads:[~2012-09-30 15:01 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-29 17:34 highest bit, statically determined Georg Bauhaus
2012-09-29 18:11 ` Pascal Obry
2012-09-29 18:59 ` Georg Bauhaus
2012-09-29 19:18 ` Georg Bauhaus
2012-09-29 18:57 ` Bill Findlay
2012-09-29 19:16 ` Bill Findlay
2012-09-29 21:36 ` Georg Bauhaus
2012-09-29 22:06 ` Georg Bauhaus
2012-09-29 23:38 ` Bill Findlay
2012-09-30 15:01 ` Vadim Godunko [this message]
2012-11-04 20:45 ` Yannick Duchêne (Hibou57)
2012-11-04 22:00 ` Bill Findlay
2012-09-30 15:39 ` Anatoly Chernyshev
2012-09-30 18:36 ` Shark8
2012-10-01 8:07 ` Georg Bauhaus
2012-10-01 8:11 ` Georg Bauhaus
2012-10-01 8:52 ` Anatoly Chernyshev
2012-10-01 21:30 ` Georg Bauhaus
2012-10-01 22:55 ` Shark8
2012-10-01 23:25 ` Georg Bauhaus
2012-10-02 11:03 ` Brian Drummond
2012-10-03 9:30 ` kalvink65
2012-10-03 18:54 ` Georg Bauhaus
2012-10-04 7:46 ` Georg Bauhaus
2012-10-04 8:25 ` Stephen Leake
2012-10-04 10:01 ` kalvin.news
2012-10-05 7:50 ` Anatoly Chernyshev
2012-10-05 8:38 ` Anatoly Chernyshev
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