[Bug rtl-optimization/47602] New: Permit inline asm to clobber PIC register

[ian at airs dot com]

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

           Summary: Permit inline asm to clobber PIC register
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: ian@airs.com


This fails for i386 32-bit when using -fpic:

void foo() { asm volatile ("movl $0,%%ebx" : : : "ebx"); }

The compiler reports

foo.c:1:14: error: PIC register clobbered by ‘ebx’ in ‘asm’

This forces people to write their asm statements differently for PIC and
non-PIC code.  That is not useful.  The compiler could save and restore the PIC
register around the asm statement.  That would be more useful, and that is what
we should do.