[Bug inline-asm/59157] New: "+f" constraint rejected: output constraint 0 must specify a single register

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59157

            Bug ID: 59157
           Summary: "+f" constraint rejected: output constraint 0 must
                    specify a single register
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: inline-asm
          Assignee: unassigned at gcc dot gnu.org
          Reporter: glisse at gcc dot gnu.org
            Target: x86_64-unknown-linux-gnu

double f(double x){
  asm volatile("":"+f"(x));
  return x;
}

a.c: In function 'f':
a.c:2:3: error: output constraint 0 must specify a single register
   asm volatile("":"+f"(x));
   ^

If I use "+mf", it is accepted with -m64 but still fails with -m32.