http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58805
--- Comment #13 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #12)
> (In reply to vries from comment #10)
> > I've tried out the example from comment 9.
> >
> > Tree-tail-merge considers the statements without effect because:
> > ...
> > (gdb) call debug_gimple_stmt (stmt)
> > # .MEM_10 = VDEF <.MEM_3(D)>
> > __asm__("movq $42, %0
> > movq %0, %1
> > " : "t" "=&r" t_8, "r" "=r" *x_4(D));
> > (gdb) call gimple_has_side_effects (stmt)
> > $2 = false
> > ...
> > and tree-ssa-tail-merge.c:stmt_local_def will return true.
> >
> > The side effect of the asm is in the expression for the output operand, so
> > gimple_has_side_effects should return true.
>
> No it shouldn't. It should return true if the stmt has side-effects that
> are _not_ explicit in the statement. This side-effect is explicitely there.
That said, it doesn't return true for the call foo(x) in
struct X { int a[256]; };
struct X __attribute__((const)) foo ();
void bar (void)
{
struct X x;
x = foo ();
}
either, even though the call has a (explicit) store.
