[U-Boot] analyze/change assembly code

[Marek Vasut]

Dear Gerlando Falauto,

> Hi all,
> 
> we recently to had face some nasty issues, where for some reason two
> (functionally identical) versions of some code behave very differently.
> Namely, one version works and the other doesn't always work.
> It was clear from the beginning this was because of HW- (or compiler-)
> related issues.
> I thought it would then be useful to have a peek at what the compiler is
> doing behind the scenes, and possibly make some simple changes to the
> code. For instance, inserting some nops here and there, or reordering
> some instructions, may help in tracking down these different behaviors.
> 
> I know the easiest way to LOOK at the file is simply to use objdump to
> disassemble an .o file. In the end I somehow managed to tamper with the
> makefiles so to get what I wanted for a given file, by adding a fake new
> ".s" target with the recipe to build it, and having the .o file depend
> on a ".S" file (which would be a manual/changed copy of the generated
> ".s" file) instead of the original ".c" file.
> This is however not linear and nice at all. So I was wondering whether
> there already is a well-established way of having the make process
> create (and keep) assembly files which can be then manually changed.
> 
> Does my question make any sense at all? Any ideas?

What compiler do you use? The Linaro one didn't behave properly for example.

Best regards,
Marek Vasut