[ECOS] Why Just even registers get saved during register windows under/over flow in Sparc? Thanks.

[Gary Thomas]

On Tue, 2002-08-13 at 06:24, Qiang Huang wrote:
> Hi all:
>    In the overflow/underflow handler in Sparc why just a single register
> window(Isn't that all the register windows get saved to stack?) get saved
> and why just even register get saved? Thanks a lot.

A Nick indicated yesterday, the entire window set is saved
when a thread switch occurs.  Other than that, it makes sense
to only bother with a single window when an under/overflow
happens.

As for "even registers only"; look more closely.  The registers
are being saved as even/odd register pairs.  For example, the
instruction (std %l0,[%sp+0]) saves registers %l0 and %l1 in
a single instruction.  Much faster.

-- 
------------------------------------------------------------
Gary Thomas                  |
eCosCentric, Ltd.            |  
+1 (970) 229-1963            |  eCos & RedBoot experts
gthomas@ecoscentric.com      |
http://www.ecoscentric.com/  |
------------------------------------------------------------


-- 
Before posting, please read the FAQ: http://sources.redhat.com/fom/ecos
and search the list archive: http://sources.redhat.com/ml/ecos-discuss