[Bug middle-end/47602] Permit inline asm to clobber PIC register

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47602

--- Comment #13 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2011-02-04 15:23:22 UTC ---
> In what way are we helping them by forcing them to know about it?  How does
> that help them write inline assembler which, e.g., uses the cpuid instruction,
> or makes a kernel system call which passes a parameter in %ebx?

In these cases, that won't probably help them indeed.  But, in other cases,
like someone wanting to write very efficiently a hot loop in asm for a library,
making it explicit that the %ebx register is not freely available like the
others might help him to find the most efficient approach.  Maybe we could just
warn though.