Very Computer

1. SPARC stack pointer (maybe off topic)

My question concerns the following assembler instruction

ld [%i0], %sp

What I would like to happen is the contents of %i0 point to a structure I
have built.  I expect that the stack should now point to the information
the [%i0] points to.

DIAGRAM 1
-------------------------------------------------------------
REGISTERS               Main Memory    
%sp -> 0xa              0xa contains 0xff9ef    
%i0 -> 0xef20           Oxb [or $sp + 4] contains Oxffeee

                        0xef20 contains Oxf10

                        0xf10 contains structure data
                        ...
-------------------------------------------------------------

I want this to happen:

DIAGRAM 2
-------------------------------------------------------------
%sp -> 0xf10            0xf10 contains structure data
-------------------------------------------------------------

Unfortunately this happens:

DIAGRAM 3
-------------------------------------------------------------
%sp -> 0xf10            0xf10 contains 0xff9ef
                        ... old sp info copied here
-------------------------------------------------------------

I find this very strange, and suspect the %sp register cannot be
manipulated.  If I do the same stuff with %fp I have no problem
unfortunately I need to use the %sp

Any ideas??
If you need more info on the overall problem it can be arranged

Peter Jamieson
U of T

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