Understanding RTL (dumps)

[kevin diggs]

Hi,

Sorry for the noise. I am trying to learn RTL. A simple function's
PowerPC RTL (gcc 3.4.6) has as one of the first RTL expressions:

(insn 3 2 4 (set (mem/f:SI (reg/f:SI 114 virtual-stack-vars) [0 u+0 S4 A32])
        (reg:SI 3 3 [ u ])) -1 (nil)
    (nil))

>From the gcc-int manual, the first 3 fields (arguments) are:

1) unique id
2) previous instruction chain
3) next instruction chain

The last four are:  RTL expression for the side effect (pattern),
instruction code of match (-1 if not yet matched), dependent
instruction list, and note list.

So for this example (which I *think* is putting the register argument
(PowerPC ABI?) on the stack???):

1) 3
2) 2
3) 4
5) (set (mem/f:SI (reg/f:SI 114 virtual-stack-vars) [0 u+0 S4 A32])
(reg:SI 3 3 [u]) )
6) -1
7) (nil)
8) (nil)

I am having trouble reading the pattern (field 5). It is a set:

(set lval x)

Two arguments, in this case the address is a mem:

(mem/f:SI ...)

and the source (x) is a reg:

(reg:SI 3 3 [u])

A mem has two arguments:

(mem:m addr alias)

The addr appears to be a reg but regs only have one argument? What is
"virtual-stack-vars"? Is the stuff in square brackets the alias set?
It's a vector (list?), right?

The 'x' in the set is "(reg:SI 3 3 [u])". What is the second '3' and
the '[u]'???

Thanks!

kevin

P.S.:  Almost forgot:  what is the '/f'?