gcc feature request / RFC: extra clobbered regs

[Andy Lutomirski]

On Wed, Jul 1, 2015 at 10:35 AM, Vladimir Makarov <vmakarov@redhat.com> wrote:
> Actually it raise a question for me.  If we describe that a function
> clobbers more than calling convention and then use it as a value (assigning
> a variable or passing as an argument) and loosing a track of it and than
> call it.  How can RA know what the call clobbers actually.  So for the
> function with the attributes we should prohibit use it as a value or make
> the attributes as a part of the function type, or at least say it is unsafe.

I think it should be part of the type.  This shouldn't compile:

void func(void) __attribute__((used_reg("r12")));
void (*x)(void);
x = func;

--Andy