Miscompilation of glibc with CVS mainline

[John David Anglin]

> > > Here's a small testcase that has the same behaviour:
> > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > extern void weak_func (void *arg);
> > > asm (".weak weak_func");
> > > 
> > > void
> > > test (void *arg)
> > > {
> > >   if (&weak_func != (void *)0)
> > >     weak_func (arg);
> > >   
> > > }
> > 
> > As GCC is not told in any way that weak_func is actually weak, I think
> > it is glibc's fault.
> 
> This is definitely a gcc problem.  This is the code arising from
> Andreas' testcase for hppa-linux at -O2:
> 
>         stw %r2,-20(%r30)
> 	ldo 64(%r30),%r30
> 	ldw -84(%r30),%r2
> 	bl weak_func,%r0
> 	ldo -64(%r30),%r30
> 
> We have completely lost the `if'.  As a result, weak_func is always
> called.

There is another problem.  The call to weak_func has been turned into
a sibcall.  It seems that TARGET_FUNCTION_OK_FOR_SIBCALL isn't being
consulted as we don't allow indirect sibcalls on hppa-linux.

Dave
-- 
J. David Anglin                                  dave.anglin@nrc.ca
National Research Council of Canada              (613) 990-0752 (FAX: 952-6605)