CHAPTER 18. ARRAYS CHAPTER 18. ARRAYS
18.1.3 MIPS.
The function uses a lot of S- registers which must be preserved, so that’s why its values are saved in the function prologue
and restored in the epilogue.
Listing 18.4: Optimizing GCC 4.4.5 (IDA)main:
var_70 = -0x70
var_68 = -0x68
var_14 = -0x14
var_10 = -0x10
var_C = -0xC
var_8 = -8
var_4 = -4
; function prologue:
lui $gp, (gnu_local_gp >> 16)
addiu $sp, -0x80
la $gp, (gnu_local_gp & 0xFFFF)
sw $ra, 0x80+var_4($sp)
sw $s3, 0x80+var_8($sp)
sw $s2, 0x80+var_C($sp)
sw $s1, 0x80+var_10($sp)
sw $s0, 0x80+var_14($sp)
sw $gp, 0x80+var_70($sp)
addiu $s1, $sp, 0x80+var_68
move $v1, $s1
move $v0, $zero
; that value will be used as a loop terminator.
; it was precalculated by GCC compiler at compile stage:
li $a0, 0x28 # '('
loc_34: # CODE XREF: main+3C
; store value into memory:
sw $v0, 0($v1)
; increase value to be stored by 2 at each iteration:
addiu $v0, 2
; loop terminator reached?
bne $v0, $a0, loc_34
; add 4 to address anyway:
addiu $v1, 4
; array filling loop is ended
; second loop begin
la $s3, $LC0 # "a[%d]=%d\n"
; "i" variable will reside in $s0:
move $s0, $zero
li $s2, 0x14
loc_54: # CODE XREF: main+70
; call printf():
lw $t9, (printf & 0xFFFF)($gp)
lw $a2, 0($s1)
move $a1, $s0
move $a0, $s3
jalr $t9
; increment "i":
addiu $s0, 1
lw $gp, 0x80+var_70($sp)
; jump to loop body if end is not reached:
bne $s0, $s2, loc_54
; move memory pointer to the next 32-bit word:
addiu $s1, 4
; function epilogue
lw $ra, 0x80+var_4($sp)
move $v0, $zero
lw $s3, 0x80+var_8($sp)
lw $s2, 0x80+var_C($sp)
lw $s1, 0x80+var_10($sp)
lw $s0, 0x80+var_14($sp)
jr $ra