"which function is called when updating a register?"

[Andrew Cagney]

> Hi
> 
>   Thanks for the reply.
> 
>   My problem is that after I building a new target, I could not see the
> registers being updated except PC. For example, after I did "set $sp =
> 0x80001000", and then "info reg", I still saw $sp is ZERO.
> 
>   I am trying to fig out what was wrong with my build. One way to do this is
> to trace the simulator execution. However I don't have a clear picture about
> the interface between the simulator execution and gdb. For example, which
> data structures are read by "info reg" command and which ones are touched by
> the simulator. How could GDB get those register content being updated by the
> simulator?

When the inferior (simulator) is resumed, GDB flushes its internal 
register cache (target_registers_changed).  This causes GDB to always 
fetch the latest register values found in the simulator.

Andrew