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Date: Sat, 15 Mar 2008 21:26:22 +0200
From: Niklas Holsti <niklas.holsti@tidorum.invalid>
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Subject: Re: Endian-problem/bug with system.bit_ops (gnat3.15)...
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Date: 2008-03-15T21:26:22+02:00
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Erik Baigar wrote:
> Niklas Holsti wrote:
> 
>>Did you have a question to ask, or did you just want to report this
>>problem and your solution?
> 
> Since the problem is solved by including all 32bits the posting is 
> not really a question - maybe the posting will give someone else, 
> encountering the same problem, a hint what to look out for...

Ok, good. (I meant no criticism, I just wondered if, or how, I 
could help.)

>>I think that your program could be made more portable by avoiding
>>'Address (and, of course, System.Bit_Ops) and using instead modular
>>types (not available in Ada83) and their predefined bitwise "and"
>>and "or" operations.
> 
> Do you have an estimation on performance? The current code 
> is quite fast in emulating the vintage processor (more than 
> 3.5MIPS in the simulation) using the non portable System.Bit_Ops...

As I understand it, and have observed in some programs and some 
targets, a bitwise operation (and, or, xor, not) on modular types 
with a power-of-two modulus translates directly into the 
corresponding machine instruction. I expect such modular types to 
be as fast as System.Bit_Ops, even if the operations in 
System.Bit_Ops are intrinsic or inlined.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
       .      @       .