What is the difference between .code32
, .code 32
, and .arm
directives in an assembly file?
The .S file will be compiled with arm-none-eabi-as
Are the three directives identical? None of these directives are explained in the programmer's guide (https://developer.arm.com/documentation/den0013/d/Introduction-to-Assembly-Language/Introduction-to-the-GNU-Assembler/Assembler-directives?lang=en), so it's hard to answer this myself.
Essentially, we wish to ensure that all functions writen in a given .S file are in ARM32 instruction mode (i.e. not Thumb).
--
Update: looks like I imagined .code32
! The other two directives are identical, .arm
is literally just shorthand for .code 32
.
Cheers for fast replies!
CodePudding user response:
They are documented in the GNU assembler manual at https://sourceware.org/binutils/docs/as/ARM-Directives.html#ARM-Directives.
.code [16|32]
This directive selects the instruction set being generated. The value 16 selects Thumb, with the value 32 selecting ARM.
.arm
This performs the same action as
.code 32
.
So either one would do what you want.
The .code32
variant is not mentioned. As you note, it doesn't actually work in GNU as. It could be a typo, or maybe some versions have permissive syntax that makes the space optional.