[Bug inline-asm/47419] missed 'mov (base,index,scale),reg' optimization?

["pinskia at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47419

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-01-23 10:22:37 UTC ---
Well there is no constraint for reg+reg*N really. You should do:
  asm /* reading has side-effects in hardware */ volatile (
                "movl %1, %0"
                : /* output operands */ "=r" ( value )
                : /* input operands */ "m" ( *(address + index) )
                : /* clobbers */
        );


This will be the correct way of expressing it and not to mention will produce
the code you want.  Though you might as well just do:
unsigned __attribute__((regparm(2)))
asm_read_mapped_register( unsigned* address, unsigned long index )
{
  volatile *unsigned a = address + index;
  return *a;
}

---- CUT -----
The constraint r just means register and nothing else can match it.