On Wed, Aug 17, 2016 at 10:03:28AM +0200, Richard Biener wrote:
> On Tue, 16 Aug 2016, Jakub Jelinek wrote:
>
> > Hi!
> >
> > The FRE devirtualization unlike gimple-fold or other places would transform
> > some method call with TREE_ADDRESSABLE lhs into __builtin_unreachable call
> > with the same lhs, which is invalid (__builtin_unreachable returns void).
> > Also, gimple_call_fntype has not been adjusted in these cases.
> >
> > Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
> > trunk? What about 6.x? Do you prefer it in 6.2, or 6.3?
>
> I think the patch can be simplified to just set fntype - PRE/FRE already
> arrange to fixup stmts, including calling fixup_noreturn_call which
> removes the lhs if required.
That isn't enough, unless fixup_noreturn_call is changed to test not just
should_remove_lhs_p, but also VOID_TYPE_P (TREE_TYPE (gimple_call_fntype
(call_stmt))
Otherwise, should_remove_lhs_p would in this case return true (we don't want
to remove TREE_ADDRESSABLE lhs). The exception is when we change the return
type because we've turned the function into one returning void (i.e.
__builtin_unreachable/__cxa_pure_virtual and the like).
So, do you prefer following (so far tested just with make check-g++
RUNTESTFLAGS=devirt*.C)
instead?
2016-08-17 Jakub Jelinek <ja...@redhat.com>
PR middle-end/77259
* tree-ssa-pre.c (eliminate_dom_walker::before_dom_children): If
turning a call into __builtin_unreachable-like noreturn call, adjust
gimple_call_set_fntype.
* tree-cfgcleanup.c (fixup_noreturn_call): Remove lhs also if
gimple_call_fntype has void return type.
* g++.dg/ipa/devirt-52.C: New test.
--- gcc/tree-ssa-pre.c.jj 2016-08-16 13:22:49.095671219 +0200
+++ gcc/tree-ssa-pre.c 2016-08-17 10:24:42.498730917 +0200
@@ -4543,6 +4543,15 @@ eliminate_dom_walker::before_dom_childre
lang_hooks.decl_printable_name (fn, 2));
}
gimple_call_set_fndecl (call_stmt, fn);
+ /* If changing the call to __builtin_unreachable
+ or similar noreturn function, adjust gimple_call_fntype
+ too. */
+ if (gimple_call_noreturn_p (call_stmt)
+ && VOID_TYPE_P (TREE_TYPE (TREE_TYPE (fn)))
+ && TYPE_ARG_TYPES (TREE_TYPE (fn))
+ && (TREE_VALUE (TYPE_ARG_TYPES (TREE_TYPE (fn)))
+ == void_type_node))
+ gimple_call_set_fntype (call_stmt, TREE_TYPE (fn));
maybe_remove_unused_call_args (cfun, call_stmt);
gimple_set_modified (stmt, true);
}
--- gcc/tree-cfgcleanup.c.jj 2016-08-09 09:41:14.000000000 +0200
+++ gcc/tree-cfgcleanup.c 2016-08-17 10:36:24.198791289 +0200
@@ -602,9 +602,14 @@ fixup_noreturn_call (gimple *stmt)
/* If there is an LHS, remove it, but only if its type has fixed size.
The LHS will need to be recreated during RTL expansion and creating
temporaries of variable-sized types is not supported. Also don't
- do this with TREE_ADDRESSABLE types, as assign_temp will abort. */
+ do this with TREE_ADDRESSABLE types, as assign_temp will abort.
+ Drop LHS regardless of TREE_ADDRESSABLE, if the function call
+ has been changed into a call that does not return a value, like
+ __builtin_unreachable or __cxa_pure_virtual. */
tree lhs = gimple_call_lhs (stmt);
- if (should_remove_lhs_p (lhs))
+ if (lhs
+ && (should_remove_lhs_p (lhs)
+ || VOID_TYPE_P (TREE_TYPE (gimple_call_fntype (stmt)))))
{
gimple_call_set_lhs (stmt, NULL_TREE);
--- gcc/testsuite/g++.dg/ipa/devirt-52.C.jj 2016-08-17 10:23:39.775528901
+0200
+++ gcc/testsuite/g++.dg/ipa/devirt-52.C 2016-08-17 10:23:39.775528901
+0200
@@ -0,0 +1,56 @@
+// PR middle-end/77259
+// { dg-do compile { target c++11 } }
+// { dg-options "-O2" }
+
+template <typename, typename = int> class A;
+template <typename, typename> struct A
+{
+ A (A &&);
+};
+template <typename S, typename T, typename U>
+A<S> operator+(S *, const A<T, U> &);
+template <typename S, typename T, typename U>
+void operator+(const A<T, U> &, S *);
+struct B
+{
+ template <typename V> B (V);
+};
+template <typename V> V foo (B) {}
+class C;
+template <typename> struct D
+{
+ C *operator->() { return d; }
+ C *d;
+};
+struct C
+{
+ virtual A<int> bar ();
+};
+struct E
+{
+ ~E ();
+ virtual A<char> bar (const B &) const;
+};
+template <typename> struct F : E
+{
+};
+template <typename W> struct F<D<W>> : E
+{
+ A<char> bar (const B &) const try
+ {
+ D<W> a = baz ();
+ }
+ catch (int)
+ {
+ }
+ D<W> baz () const
+ {
+ D<C> b = foo<D<C>>(0);
+ "" + b->bar () + "";
+ }
+};
+struct G : F<D<int>>
+{
+ G (int);
+};
+void test () { G (0); }
Jakub
