high memory +------------------------+
| .... |
| .... |
virtual frame | argument n |
pointer $(fp) ->/+------------------------+\
/ | | \
frame offset | local & temporaries | \
\ | | \
\+------------------------+ \
| saved registers | frame size
| (including returnreg) | /
+------------------------+ /
| .... | /
stack | argument build | /
pointer $(sp) -> +------------------------+/
(framereg) | .... |
| .... |
| |
| |
| |
low memory +------------------------+
.frame framereg, framesize, returnreg
The virtual frame pointer is a frame pointer as used in other compiler systems but has no register allocated for it. It consists of the framereg ($sp, in most cases) added to the framesize. The returnreg specifies the register containing the return address (usually $ra).
.mask bitmask, frameoffset
The .mask directive specifies the registers to be stored and where they are stored. A bit should be on in bitmask for each register saved (for example, if register $31 is saved, bit 31 should be ‘1’ in bitmask. Bits are set in bitmask in little-endian order, even if the machine configuration is big-endian).The frameoffset is the offset from the virtual frame pointer (this number is usually negative).
.fmask bitmask, frameoffset
Notice that saving floating-point registers is identical to saving general registers except we use the .fmask pseudo-op instead of .mask, and the stores are of floating-point singles or doubles.
.text .cfi_sections .debug_frame .align 2 .globl main .cfi_startproc .ent main .type main, @function main: .frame $fp,32,$31 # vars= 16, regs= 1/0, args= 0, gp= 0 .mask 0x40000000,-8 .fmask 0x00000000,0 .set noreorder .set nomacro daddiu $sp,$sp,-32 .cfi_def_cfa_offset 32 sd $fp,24($sp) .cfi_offset 30, -8 move $fp,$sp .cfi_def_cfa_register 30 move $2,$4 sd $5,8($fp) sll $2,$2,0 sw $2,0($fp) .loc 1 6 12 move $2,$0 .loc 1 7 1 move $sp,$fp .cfi_def_cfa_register 29 ld $fp,24($sp) daddiu $sp,$sp,32 .cfi_restore 30 .cfi_def_cfa_offset 0 jr $31 nop .set macro .set reorder .end main .cfi_endproc .size main, .-main |
References
From: http://www.cs.unibo.it/~solmi/teaching/arch_2002-2003/AssemblyLanguageProgDoc.pdf