[Bug c/48623] New: gcc 4.6.0 generates no code for a function with __attribute__((always_inline))

[richard at nod dot at]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48623

           Summary: gcc 4.6.0 generates no code for a function with
                    __attribute__((always_inline))
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: rich...@nod.at


gcc 4.6.0 builds a non-functional User Mode Linux kernel.
It seems to optimize away the function sub_preempt_count() used in
kernel/softirq.c:__local_bh_enable().
Thus, the preempt counter gets out of balance and the kernel crashes.

A standalone test case is attached.
Just compile it with:
gcc testcase.c -Os -g -c -o testcase.o

Using objdump you can see that no code was generated for sub_preempt_count().
gcc 4.3, 4.4 and 4.5 generate code.
Without __attribute__((always_inline)) 4.6.0 produces code...

Thanks,
//richard