Add 128 bit numbers

Index > Main > Add 128 bit numbers

Author

Thread

kandamun

Joined: 20 Jul 2005
Posts: 25

kandamun 19 Feb 2008, 16:52

Hello all
Is there an instruction that adds two 128 bit numbers with carry?
I thought SSEx should have one but I could not find it.
And what is the most number of bits that can be ADDED with one instruction (with carry set)?

19 Feb 2008, 16:52

Borsuc

Joined: 29 Dec 2005
Posts: 2465
Location: Bucharest, Romania

Borsuc 19 Feb 2008, 16:57

kandamun wrote:

Hello all
Is there an instruction that adds two 128 bit numbers with carry?

You need two 64-bit adds, or four 32-bit adds, obviously to form a 128-bit add in both cases...

see Working with Big Numbers thread.

kandamun wrote:

And what is the most number of bits that can be ADDED with one instruction (with carry set)?

Infinite

as long as it fits in memory/RAM

19 Feb 2008, 16:57

kandamun

Joined: 20 Jul 2005
Posts: 25

kandamun 19 Feb 2008, 18:55

Thanks.
I know how to use 32-bit - add / adc .
But when there are 128 registers why isn't there 128 bit add instruction ?

19 Feb 2008, 18:55

r22

Joined: 27 Dec 2004
Posts: 805

r22 19 Feb 2008, 20:09

kandamun wrote:

Thanks.
I know how to use 32-bit - add / adc .
But when there are 128 registers why isn't there 128 bit add instruction ?

The 128bit registers are part of SSE.
SSE stands for Streaming SIMD Extensions.
SIMD stands for Single Instruction Multiple Data.

19 Feb 2008, 20:09

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19872
Location: In your JS exploiting you and your system

revolution 20 Feb 2008, 02:32

kandamun wrote:

Thanks.
I know how to use 32-bit - add / adc .
But when there are 128 registers why isn't there 128 bit add instruction ?

The registers are split into smaller parts, 64/32/16/8 bits, there is no instruction (yet) to work with all 128 bits as a single number. The MD part of SIMD implies that there is not just one piece of data in the register.

20 Feb 2008, 02:32

daniel.lewis

Joined: 28 Jan 2008
Posts: 92

daniel.lewis 21 Feb 2008, 06:34

Hmm... I should research to see if anyone has concieved of a parallelize-able lexer.

21 Feb 2008, 06:34

< Last Thread | Next Thread >

Forum Rules:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum