GCC ASM(): Urgent!

[YZ Dai]

Hi,

I'm using GNU CC, ccmips or asmips. I see within the generated .s file
from .c file there are:

jpeg_idct_ifast:
 .frame $fp,368,$31  # vars= 360, regs= 1/0, args= 0, extra= 0
 .mask 0x40000000,-8
 .fmask 0x00000000,0

1. What does .frame,.mask and .fmask means?
2. Which registers are protected? Which registers I can use in my ASM()
routine?
3. How to support Mips R3900 instruction like MULT rd,rs,rt?
4. In GCC book within a macro "\" gives operator value, but the example
gives compile error:
.macro mname rd
    .word   \ rd
.endm

5. How to debug and trace in the asm() instructions in a .C file?

Many thanks!

YZ DAI