gcc - ARM overflow flag -


i read here, overflow flag might set in cases. trying out 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 error message said following :-

carryflagsub.s: assembler messages: carryflagsub.s:8: error: bad instruction `os is_set'

isn't os instruction used test if overflow flag set?

there no os instruction in arm instruction set. however, test if overflow flag set can use conditional execution of instructions, that.

bvs is_set

you can learn conditional execution in arm reference manual.


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