Re: Do not spill variables/registers on the stack

[Ian Lance Taylor <iant at google dot com>]

Stefan Schulze Frielinghaus <stefan@seekline.net> writes:

> I would like to compile my code with optimization level zero (-O0) and
> enable only one optimization which keeps most variables in registers if
> possible, i.e. does not spill them on the stack.
>
> At the moment I circumvent this problem by always stating that a
> variable should be in a register if possible:
>
> int main(void) {
> 	register int a = 1;
> 	register int b = -1;
>
> 	return a+b;
> }
>
> Compiling it with -O0 results in a binary where the variables a and b
> are in registers and are not spilled on the stack. If I remove the
> keyword "register", then the variables are spilled on the stack.
> I had a look at the man page but couldn't find a suitable optimization
> flag which prohibits this.
>
> Does someone has an idea?

What you want is to disable all optimizations other than register
allocation.  That does not sound like a particularly useful feature for
gcc to provide, and in fact it does not provide it.  You could do it by
changing gcc's source code.

Ian