CODEWITHSUNDEEP
gccassemblyarm
user277465
user277465

Reputation:

ARM overflow flag

I read here, that the overflow flag might also be set in certain cases. Trying out the following sample of code :-

.global main
.func main

main:
mov r0, #4026531839
mov r1, #-1
sub r0, r0, r1
os is_set
mov r0, #17
bx lr

is_set:
mov r0, #71
bx lr

I got an error message that said the following :-

carryflagsub.s: Assembler messages:
carryflagsub.s:8: Error: bad instruction `os is_set'

Isn't os the instruction used to test if the overflow flag is set?

Upvotes: 0

Views: 343

Answers (2)

newbie
newbie

Reputation: 1260

There is no os instruction in ARM instruction set. However, to test if the overflow flag is set you can use conditional execution of instructions, like that.

bvs is_set

You can learn about conditional execution in ARM reference manual.

Upvotes: 2

ooga
ooga

Reputation: 15501

By os I assume you mean vs.

If you want to branch on the vs condition, the instruction is bvs.

Upvotes: 0

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