Signed Bitfield Insert in Zeros copies a bitfield of <width> bits from the least significant bits of the source register to bit position <lsb> of the destination register, setting the destination bits below the bitfield to zero, and the bits above the bitfield to a copy of the most significant bit of the bitfield.
带符号的位字段零插入将<width>位的位字段从源寄存器的最低有效位复制到目标寄存器的<lsb>位位置，将位字段下方的目标位设置为零，并将位字段上方的位设置为位字段最高有效位的副本。
32-bit variant
SBFIZ <Wd>, <Wn>, #<lsb>, #<width>
is equivalent to
SBFM <Wd>, <Wn>, #(-<lsb> MOD 32), #(<width>-1)
64-bit variant
SBFIZ <Xd>, <Xn>, #<lsb>, #<width>
is equivalent to
SBFM <Xd>, <Xn>, #(-<lsb> MOD 64), #(<width>-1)
40380c: 937d7f80 sbfiz x0, x28, #3, #32 // x28=1, x0=1<<3=8
403810: 97fff8dc bl 401b80 <malloc@plt> // malloc(x0)
403814: f9002660 str x0, [x19, #72] // this->argv=malloc
403818: aa0003fb mov x27, x0
40381c: b4000b20 cbz x0, 403980 <ferror@plt+0x1aa0> // exit(1)
if (!(this->argv = malloc(sizeof(char *) * this->argc))) {
// cbz 403980
perror("malloc");
exit(1);
}
=> 0x000000000040380c: 80 7f 7d 93 sbfiz x0, x28, #3, #32
1: $sp = (void *) 0x7fffffb190
(gdb) p/x $x0
$65 = 0xc
(gdb) p/x $x28
$66 = 0x1
(gdb) n
0x0000000000403810 in ?? ()
=> 0x0000000000403810: dc f8 ff 97 bl 0x401b80 <malloc@plt>
1: $sp = (void *) 0x7fffffb190
(gdb) p/x $x0
$67 = 0x8
(gdb) p/x $x28
$68 = 0x1