Abt RTL expression

[Revital1 Eres <ERES at il dot ibm dot com>]

(insn 8 6 9 1 (parallel [
            (set (reg/f:SI 32)
                (symbol_ref:SI ("t") <var_decl 0x402270b0 t>))
            (clobber (reg:CC 21 cc))
        ]) -1 (nil)
    (nil))

Here is an answer to your first question:

8 6 9 are the serial numbers of the current, previous and next instructions
in the instructions link list;
1 is the serial number of the instruction basic block.
You can read more about the RTL representation of insn in
http://gcc.gnu.org/onlinedocs/gccint/Insns.html.

Also, the following are taken from http://gcc.gnu.org/onlinedocs/gccint/:

clobber indicates something is clobbered in a way that we don't want to
explain.
For example, subroutine calls will clobber some physical registers.

reg/f - In reg expressions, 1 means that the register holds a pointer.

Revital