[ping x2] Re: [PATCH] Fix expand_builtin_atomic_fetch_op for pre-op (PR80902)

[Segher Boessenkool <segher at kernel dot crashing dot org>]

Ping.

On Wed, May 31, 2017 at 08:19:56AM -0500, Segher Boessenkool wrote:
> Ping.
> 
> (Sorry for the very aggressive ping; this fixes 764 testsuite failures
> on powerpc-linux).
> 
> 
> Segher
> 
> 
> On Sun, May 28, 2017 at 12:31:12PM +0000, Segher Boessenkool wrote:
> > __atomic_add_fetch adds a value to some memory, and returns the result.
> > If there is no direct support for this, expand_builtin_atomic_fetch_op
> > is asked to implement this as __atomic_fetch_add (which returns the
> > original value of the mem), followed by the addition.  Now, the
> > __atomic_add_fetch could have been a tail call, but we shouldn't
> > perform the __atomic_fetch_add as a tail call: following code would
> > not be executed, and in fact thrown away because there is a barrier
> > after tail calls.
> > 
> > This fixes it.
> > 
> > Tested on powerpc64-linux {-m32,-m64}.  Is this okay for trunk?
> > 
> > 
> > Segher
> > 
> > 
> > 2017-05-28  Segher Boessenkool  <segher@kernel.crashing.org>
> > 
> > 	PR middle-end/80902
> > 	* builtins.c (expand_builtin_atomic_fetch_op): If emitting code after
> > 	a call, force the call to not be a tail call.
> > 
> > ---
> >  gcc/builtins.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/gcc/builtins.c b/gcc/builtins.c
> > index 4f6c9c4..3a70693 100644
> > --- a/gcc/builtins.c
> > +++ b/gcc/builtins.c
> > @@ -6079,6 +6079,12 @@ expand_builtin_atomic_fetch_op (machine_mode mode, tree exp, rtx target,
> >    gcc_assert (TREE_OPERAND (addr, 0) == fndecl);
> >    TREE_OPERAND (addr, 0) = builtin_decl_explicit (ext_call);
> >  
> > +  /* If we will emit code after the call, the call can not be a tail call.
> > +     If it is emitted as a tail call, a barrier is emitted after it, and
> > +     then all trailing code is removed.  */
> > +  if (!ignore)
> > +    CALL_EXPR_TAILCALL (exp) = 0;
> > +
> >    /* Expand the call here so we can emit trailing code.  */
> >    ret = expand_call (exp, target, ignore);
> >  
> > -- 
> > 1.9.3