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  1.  Home
  2. MI400
  3. June 2005

Re: Write System Pointer to User Space

Looking an an MI pgm with a 32-byte CPYBLA and a 32-byte CPYBWP, the CPYBLA uses LSDX/STSDX (Load/Store string doubleword indexed), while CPYBWP uses 2 pairs of LQ/STQ (Load/Store quadword). 

One could write test loops to find out which is faster.

I suspect memcpy always does CPYBWP.

--Dave

Steve Richter wrote:


-----Original Message-----
From: mi400-bounces@xxxxxxxxxxxx [mailto:mi400-bounces@xxxxxxxxxxxx]On
Behalf Of Dave McKenzie
Sent: Sunday, June 19, 2005 2:11 PM
To: MI Programming on the AS400 / iSeries
Subject: Re: [MI400] Write System Pointer to User Space


Hi Peter,


Here's a pgm that does that.  The "memcpy" function does the equivalent
of a CPYBWP (Copy Bytes With Pointers) MI instruction under the covers.


I have always assumed that CPYBWP was slower than CPYBLA.  Not true? Does 
memcpy always use CPYBWP in place of CPYBLA? ( I know,  LDQ and STQ! )

-Steve

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