Re: [C++ PATCH] Genericize IF_STMT already during genericization, before gimplification (PR c++/36254)

["Richard Guenther" <richard dot guenther at gmail dot com>]

On Thu, Jan 8, 2009 at 11:30 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> shortcut_cond_expr uses block_may_fallthru to determine whether
> a jump around else is needed or not.  But this happens during
> gimplification, before then and else are gimplified, and block_may_fallthru,
> being a middle-end function, doesn't understand FE specific trees.
> For if this can be fixed simply by genericizing IF_STMT into COND_EXPR
> already during cp_genericize, before gimplification - there is nothing
> in IF_STMT genericization that needs to be deferred till gimplification.

Isn't this true for all frontend specific trees?  That is, FOR_STMT isn't proper
GENERIC either - and don't we want to feed the gimplifier with GENERIC only?

Richard.

> Bootstrapped/regtested on x86_64-linux, ok for trunk?
>
> 2009-01-08  Jakub Jelinek  <jakub@redhat.com>
>
>        PR c++/36254
>        * cp-gimplify.c (genericize_if_stmt): Renamed from ...
>        (gimplify_if_stmt): ... this.
>        (cp_gimplify_expr): Don't handle IF_STMT here.
>        (cp_genericize_r): Call genericize_if_stmt for IF_STMT.
>
>        * g++.dg/warn/Wreturn-type-5.C: New test.
>
> --- gcc/cp/cp-gimplify.c.jj     2008-11-04 21:03:14.000000000 +0100
> +++ gcc/cp/cp-gimplify.c        2009-01-08 22:16:52.000000000 +0100
> @@ -158,7 +158,7 @@ genericize_eh_spec_block (tree *stmt_p)
>  /* Genericize an IF_STMT by turning it into a COND_EXPR.  */
>
>  static void
> -gimplify_if_stmt (tree *stmt_p)
> +genericize_if_stmt (tree *stmt_p)
>  {
>   tree stmt, cond, then_, else_;
>   location_t locus = EXPR_LOCATION (*stmt_p);
> @@ -611,11 +611,6 @@ cp_gimplify_expr (tree *expr_p, gimple_s
>       ret = GS_ALL_DONE;
>       break;
>
> -    case IF_STMT:
> -      gimplify_if_stmt (expr_p);
> -      ret = GS_OK;
> -      break;
> -
>     case FOR_STMT:
>       gimplify_for_stmt (expr_p, pre_p);
>       ret = GS_OK;
> @@ -803,6 +798,13 @@ cp_genericize_r (tree *stmt_p, int *walk
>                      CLEANUP_BODY (stmt),
>                      CLEANUP_EXPR (stmt));
>
> +  else if (TREE_CODE (stmt) == IF_STMT)
> +    {
> +      genericize_if_stmt (stmt_p);
> +      /* *stmt_p has changed, tail recurse to handle it again.  */
> +      return cp_genericize_r (stmt_p, walk_subtrees, data);
> +    }
> +
>   /* COND_EXPR might have incompatible types in branches if one or both
>      arms are bitfields.  Fix it up now.  */
>   else if (TREE_CODE (stmt) == COND_EXPR)
> --- gcc/testsuite/g++.dg/warn/Wreturn-type-5.C.jj       2009-01-08 17:43:06.000000000 +0100
> +++ gcc/testsuite/g++.dg/warn/Wreturn-type-5.C  2009-01-08 17:43:06.000000000 +0100
> @@ -0,0 +1,21 @@
> +// PR c++/36254
> +// { dg-do compile }
> +// { dg-options "-Wreturn-type" }
> +
> +int i, j, k;
> +struct X { X (); ~X (); };
> +
> +bool
> +foo ()
> +{
> +  X x;
> +  if (i && j)
> +    {
> +      if (k)
> +       return true;
> +      else
> +       return false;
> +    }
> +  else
> +    return false;
> +}
>
>        Jakub
>