How to SET a memory location with value contained in rtx register...

[Vaibhav Shrimali]

I am making changes in the prologue of the compiler (ix86_expand_prologue()).
Here I want to SET (not push) a previous memory location, i.e. which
lies above the stack_pointer, with a value contained in a rtx variable
(register).
I could not find a method which would allow me to do the task.
One procedure I can think of is that I can store that memory location
in another rtx type variable. So is it possible to store the value of
a rtx variable in a memory location specified by another rtx variable.
Please suggest me some solution.
Thank You.

-- 
Vaibhav Shrimali
BTech(ICT), DA-IICT
Gandhinagar