I am trying to learn ARM assembly and I wanted to store a signed number in a register, it has to be something like -
MOV R0, #-10
But this stores the number normally and not as a signed number. I tried using LDRSB as -
LDRSB R0, =0x0000000A, but it gave me errors.
Assembly language is specific to the assembler. Did you mean arm7 or armv7?
This is gnu assembler
mov r0,#-10
ldr r0,=-10
.thumb
mov r0,#-10
ldr r0,=-10
.syntax unified
mov r0,#-10
ldr r0,=-10
so.s: Assembler messages:
so.s:12: Error: cannot honor width suffix -- `mov r0,#-10'
so.s:7: Error: invalid immediate: -10 is out of range
try again
mov r0,#-10
ldr r0,=-10
.thumb
@mov r0,#-10
ldr r0,=-10
.syntax unified
@mov r0,#-10
ldr r0,=-10
00000000 <.text>:
0: e3e00009 mvn r0, #9
4: e3e00009 mvn r0, #9
8: 4800 ldr r0, [pc, #0] ; (c <.text+0xc>)
a: 4800 ldr r0, [pc, #0] ; (c <.text+0xc>)
c: fffffff6 .word 0xfffffff6
so were you looking at (full sized) ARM then?
0: e3e00009 mvn r0, #9
4: e3e00009 mvn r0, #9
Which is the easiest one of the three to encode. And you can easily see the encoding in the ARM documentation. And the tools have already done half the work for you (0xfffffff6).
If you meant armv7 then
mov r0,#-10
ldr r0,=-10
.thumb
@mov r0,#-10
ldr r0,=-10
.syntax unified
mov r0,#-10
ldr r0,=-10
00000000 <.text>:
0: e3e00009 mvn r0, #9
4: e3e00009 mvn r0, #9
8: f06f 0009 mvn.w r0, #9
c: f06f 0009 mvn.w r0, #9
10: f06f 0009 mvn.w r0, #9