Re: [PATCH] Fix middle-end/67133, part 1

[Richard Biener <richard dot guenther at gmail dot com>]

On Tue, Aug 18, 2015 at 9:49 PM, Marek Polacek <polacek@redhat.com> wrote:
> On Tue, Aug 18, 2015 at 10:45:21AM +0200, Richard Biener wrote:
>> On Mon, Aug 17, 2015 at 7:31 PM, Jeff Law <law@redhat.com> wrote:
>> > But in walking through all that, I think I've stumbled on a simpler
>> > solution.  Specifically do as a little as possible and let the standard
>> > mechanisms clean things up :-)
>> >
>> > 1. Delete the code that removes instructions after the trap.
>> >
>> > 2. Split the block immediately after the trap and remove the edge
>> >    from the original block (with the trap) to the new block.
>>
>> cfg-cleanup will do that for you if you have a not returning stmt ending
>> the previous block.
>
> The following patch hopefully does what's oulined above.
> Arguably I should have renamed the insert_trap_and_remove_trailing_statements
> to something more descriptive, e.g. insert_trap_and_split_block.  Your
> call.
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk?

Looks good to me.

Richard.

> 2015-08-18  Marek Polacek  <polacek@redhat.com>
>
>         PR middle-end/67133
>         * gimple-ssa-isolate-paths.c
>         (insert_trap_and_remove_trailing_statements): Rename to ...
>         (insert_trap): ... this.  Don't remove trailing statements; split
>         block instead.
>         (find_explicit_erroneous_behaviour): Don't remove all outgoing edges.
>
>         * g++.dg/torture/pr67133.C: New test.
>
> diff --git gcc/gimple-ssa-isolate-paths.c gcc/gimple-ssa-isolate-paths.c
> index 6f84f85..ca2322d 100644
> --- gcc/gimple-ssa-isolate-paths.c
> +++ gcc/gimple-ssa-isolate-paths.c
> @@ -66,10 +66,10 @@ check_loadstore (gimple stmt, tree op, tree, void *data)
>    return false;
>  }
>
> -/* Insert a trap after SI and remove SI and all statements after the trap.  */
> +/* Insert a trap after SI and split the block after the trap.  */
>
>  static void
> -insert_trap_and_remove_trailing_statements (gimple_stmt_iterator *si_p, tree op)
> +insert_trap (gimple_stmt_iterator *si_p, tree op)
>  {
>    /* We want the NULL pointer dereference to actually occur so that
>       code that wishes to catch the signal can do so.
> @@ -115,18 +115,8 @@ insert_trap_and_remove_trailing_statements (gimple_stmt_iterator *si_p, tree op)
>    else
>      gsi_insert_before (si_p, seq, GSI_NEW_STMT);
>
> -  /* We must remove statements from the end of the block so that we
> -     never reference a released SSA_NAME.  */
> -  basic_block bb = gimple_bb (gsi_stmt (*si_p));
> -  for (gimple_stmt_iterator si = gsi_last_bb (bb);
> -       gsi_stmt (si) != gsi_stmt (*si_p);
> -       si = gsi_last_bb (bb))
> -    {
> -      stmt = gsi_stmt (si);
> -      unlink_stmt_vdef (stmt);
> -      gsi_remove (&si, true);
> -      release_defs (stmt);
> -    }
> +  split_block (gimple_bb (new_stmt), new_stmt);
> +  *si_p = gsi_for_stmt (stmt);
>  }
>
>  /* BB when reached via incoming edge E will exhibit undefined behaviour
> @@ -215,7 +205,7 @@ isolate_path (basic_block bb, basic_block duplicate,
>           update_stmt (ret);
>         }
>        else
> -       insert_trap_and_remove_trailing_statements (&si2, op);
> +       insert_trap (&si2, op);
>      }
>
>    return duplicate;
> @@ -422,14 +412,8 @@ find_explicit_erroneous_behaviour (void)
>                     continue;
>                 }
>
> -             insert_trap_and_remove_trailing_statements (&si,
> -                                                         null_pointer_node);
> -
> -             /* And finally, remove all outgoing edges from BB.  */
> -             edge e;
> -             for (edge_iterator ei = ei_start (bb->succs);
> -                  (e = ei_safe_edge (ei)); )
> -               remove_edge (e);
> +             insert_trap (&si, null_pointer_node);
> +             bb = gimple_bb (gsi_stmt (si));
>
>               /* Ignore any more operands on this statement and
>                  continue the statement iterator (which should
> diff --git gcc/testsuite/g++.dg/torture/pr67133.C gcc/testsuite/g++.dg/torture/pr67133.C
> index e69de29..0f23572 100644
> --- gcc/testsuite/g++.dg/torture/pr67133.C
> +++ gcc/testsuite/g++.dg/torture/pr67133.C
> @@ -0,0 +1,46 @@
> +// { dg-do compile }
> +// { dg-additional-options "-fisolate-erroneous-paths-attribute" }
> +
> +class A;
> +struct B {
> +  typedef A type;
> +};
> +template <typename> struct I : B {};
> +class C {
> +public:
> +  C(char *);
> +  int size();
> +};
> +template <typename> struct D;
> +template <typename _Tp, typename = D<_Tp>> class F {
> +  class G {
> +    template <typename> static _Tp *__test();
> +    typedef int _Del;
> +
> +  public:
> +    typedef decltype(__test<_Del>()) type;
> +  };
> +
> +public:
> +  typename I<_Tp>::type operator*() {
> +    typename G::type a = 0;
> +    return *a;
> +  }
> +};
> +class H {
> +  F<A> Out;
> +  H();
> +};
> +void fn1(void *, void *, int) __attribute__((__nonnull__));
> +class A {
> +  int OutBufEnd, OutBufCur;
> +
> +public:
> +  void operator<<(C p1) {
> +    int b, c = p1.size();
> +    if (OutBufEnd)
> +      fn1(&OutBufCur, &b, c);
> +  }
> +};
> +char* a;
> +H::H() { *Out << a; }
>
>         Marek