http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59660
--- Comment #10 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Jan Hubicka from comment #9)
> Hi,
> this patch solves the testcase.
> The first hunk gets rid of the redundant NOP_EXPR converting TRUTH_EXPR from
> INT to BOOL. The second improves gimplifier to not introduce unnecesary
> control flow.
>
> If this approach seems to make sense, I will extend it to other booleans and
> prepare less hackish patch.
>
> Honza
>
> Index: fold-const.c
> ===================================================================
> --- fold-const.c (revision 206346)
> +++ fold-const.c (working copy)
> @@ -1977,6 +1977,8 @@ fold_convert_loc (location_t loc, tree t
>
> case INTEGER_TYPE: case ENUMERAL_TYPE: case BOOLEAN_TYPE:
> case OFFSET_TYPE:
> + if (TREE_CODE (arg) == TRUTH_ORIF_EXPR)
> + return fold_build2_loc (loc, TRUTH_ORIF_EXPR, type, TREE_OPERAND (arg,
> 0),
> TREE_OPERAND (arg, 1));
> if (TREE_CODE (arg) == INTEGER_CST)
> {
> tem = fold_convert_const (NOP_EXPR, type, arg);
This looks bogus. See where we do this folding and instead handle it
there (I suspect gimple_boolify?)
> Index: gimplify.c
> ===================================================================
> --- gimplify.c (revision 206346)
> +++ gimplify.c (working copy)
> @@ -2931,14 +2931,37 @@ gimplify_cond_expr (tree *expr_p, gimple
> result = build_simple_mem_ref_loc (loc, tmp);
> }
>
> - /* Build the new then clause, `tmp = then_;'. But don't build the
> - assignment if the value is void; in C++ it can be if it's a throw. */
> - if (!VOID_TYPE_P (TREE_TYPE (then_)))
> - TREE_OPERAND (expr, 1) = build2 (MODIFY_EXPR, type, tmp, then_);
> + /* Convert (A||B) ? true : false
> + as A ? tmp = true : tmp = B != 0. */
So does it end up working for if (a || b || c)? Otherwise this looks
sensible to me. (A&&B) ? true : false -> A ? tmp = B != 0 : tmp = false
then?
> - /* Similarly, build the new else clause, `tmp = else_;'. */
> - if (!VOID_TYPE_P (TREE_TYPE (else_)))
> - TREE_OPERAND (expr, 2) = build2 (MODIFY_EXPR, type, tmp, else_);
> + if (integer_zerop (else_) && integer_onep (then_)
> + && TREE_CODE (TREE_OPERAND (expr, 0)) == TRUTH_ORIF_EXPR)
> + {
> + tree pred = TREE_OPERAND (expr, 0);
> + location_t loc = EXPR_LOCATION (*expr_p);
> + TREE_OPERAND (expr, 0) = TREE_OPERAND (pred, 0);
> + /* Build the new then clause, `tmp = then_;'. But don't build the
> + assignment if the value is void; in C++ it can be if it's a throw.
> */
> + TREE_OPERAND (expr, 1) = build2 (MODIFY_EXPR, type, tmp,
> + fold_convert (type,
> boolean_true_node));
> +
> + /* Similarly, build the new else clause, `tmp = else_;'. */
> + TREE_OPERAND (expr, 2) = build2 (MODIFY_EXPR, type, tmp,
> + fold_build2_loc (loc, NE_EXPR, type,
> TREE_OPERAND (pred, 1),
> + fold_convert
> (TREE_TYPE (TREE_OPERAND (pred, 1)),
> +
> integer_zero_node)));
> + }
> + else
> + {
> + /* Build the new then clause, `tmp = then_;'. But don't build the
> + assignment if the value is void; in C++ it can be if it's a throw.
> */
> + if (!VOID_TYPE_P (TREE_TYPE (then_)))
> + TREE_OPERAND (expr, 1) = build2 (MODIFY_EXPR, type, tmp, then_);
> +
> + /* Similarly, build the new else clause, `tmp = else_;'. */
> + if (!VOID_TYPE_P (TREE_TYPE (else_)))
> + TREE_OPERAND (expr, 2) = build2 (MODIFY_EXPR, type, tmp, else_);
> + }
>
> TREE_TYPE (expr) = void_type_node;
> recalculate_side_effects (expr);
