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flat assembler > Main > Using doubles (64 bit math)

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crc



Joined: 21 Jun 2003
Posts: 637
Location: Penndel, PA [USA]
I'm trying to make sense of doubles (64 bit). Basically I want to add/subtract/multiply/divide 64-bit integers. But I have no idea how to do any of this. I've heard that the FPU has instructions that can handle 64-bit math, but I've never used the FPU instructions (and have no idea what they are!). If anyone has sample code that shows how to do any of these things, please share it!
Post 13 Aug 2004, 22:46
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roticv



Joined: 19 Jun 2003
Posts: 374
Location: Singapore
Try bitrake's snipplet

http://www.bitrake.com/phpBB2/topic.php?t=62

I think using fpu for 64bit integer maths is a bad idea
Post 14 Aug 2004, 04:27
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tom tobias



Joined: 09 Sep 2003
Posts: 1320
Location: usa
you may wish to employ some of the newer registers, sorry, I have no experience with them, but I believe they are 128 bits wide. Regards, tom
Post 14 Aug 2004, 07:14
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7108
Location: Slovakia
tom: yes, they are, but they are purposed to work with multiple number at the same time, not on one big. MMX is for integers (whole numbers), SSE for floats. FPU works with single floating point numbers.

crc: chapter 8 (maybe 9) of my tuts will be about this, but you probably wouldn't want to wait for it (few month maybe). Anyway, check "adc" and "sbb" instructions about adding and substracting.
Post 20 Aug 2004, 20:05
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crc



Joined: 21 Jun 2003
Posts: 637
Location: Penndel, PA [USA]
Quote:
chapter 8 (maybe 9) of my tuts will be about this, but you probably wouldn't want to wait for it (few month maybe). Anyway, check "adc" and "sbb" instructions about adding and substracting.


Thank you for the pointers. I'm (slowly) starting to make sense of 64 bit numbers. Vid, I'll watch for chapters 8 & 9 of your tutorial; this is one aspect of assembly programming that I'm finding quite confusing :-/
Post 21 Aug 2004, 00:32
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crc



Joined: 21 Jun 2003
Posts: 637
Location: Penndel, PA [USA]
I *think* I have addition and subtraction working now, but I have no idea how to display the result Sad The value is in EDX:EAX Does anyone know how to display this in a console (Linux, FreeBSD, Windows, or BeOS?)

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Charles Childers, Programmer
Post 22 Aug 2004, 06:04
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7108
Location: Slovakia
if you want display it decimal, you need division and modulo operations.

by the way, there is something about combining two number into one in my tutorial, maybe it would help.
Post 22 Aug 2004, 11:19
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f0dder



Joined: 19 Feb 2004
Posts: 3170
Location: Denmark
http://srcvault.scali.eu.org/cgi-bin/Syntax/Syntax.cgi?PrintRadix.asm

Have a look around the source vault, there's a number of useful routines there.
Post 23 Aug 2004, 13:13
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Mac2004



Joined: 15 Dec 2003
Posts: 313
Hi!

Take a look at Randall Hyde's Art of Assembly book. Randall's teaching how to do 64bit and 128bit math. That could help you. Smile

Regards
Mac2004
Post 09 Sep 2004, 11:57
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