On Fri, Apr 29, 2011 at 6:43 PM, Jakub Jelinek <[email protected]> wrote:
> Hi!
>
> The following patch fixes a bug in tree-switch-conversion.c with
> signed index_expr's. build_arrays would compute index_expr - range_min
> in index_expr's type and use that as index into CSWTCH.N array,
> which is wrong, because in this case index_expr 98 - (-62) computed
> in signed char type results in signed overflow and we end up
> loading from CSWTCH.2[-96]. Apparently for the bounds checking
> we perform the same index_expr - range_min computation, but in
> corresponding unsigned type. This patch computes it just once in
> unsigned type, so that overflow isn't undefined.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for
> trunk/4.6/4.5/4.4?
>
> 2011-04-29 Jakub Jelinek <[email protected]>
>
> PR tree-optimization/48809
> * tree-switch-conversion.c (build_arrays): Compute tidx in unsigned
> type.
> (gen_inbound_check): Don't compute index_expr - range_min in utype
> again, instead reuse SSA_NAME initialized in build_arrays.
> Remove two useless gsi_for_stmt calls.
>
> * gcc.c-torture/execute/pr48809.c: New test.
>
> --- gcc/tree-switch-conversion.c.jj 2010-12-02 11:51:32.000000000 +0100
> +++ gcc/tree-switch-conversion.c 2011-04-29 15:23:57.000000000 +0200
> @@ -1,6 +1,6 @@
> /* Switch Conversion converts variable initializations based on switch
> statements to initializations from a static array.
> - Copyright (C) 2006, 2008, 2009, 2010 Free Software Foundation, Inc.
> + Copyright (C) 2006, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
> Contributed by Martin Jambor <[email protected]>
>
> This file is part of GCC.
> @@ -656,7 +656,7 @@ static void
> build_arrays (gimple swtch)
> {
> tree arr_index_type;
> - tree tidx, sub, tmp;
> + tree tidx, sub, tmp, utype;
> gimple stmt;
> gimple_stmt_iterator gsi;
> int i;
> @@ -664,14 +664,20 @@ build_arrays (gimple swtch)
>
> gsi = gsi_for_stmt (swtch);
>
> + /* Make sure we do not generate arithmetics in a subrange. */
> + utype = TREE_TYPE (info.index_expr);
> + if (TREE_TYPE (utype))
> + utype = lang_hooks.types.type_for_mode (TYPE_MODE (TREE_TYPE (utype)),
> 1);
> + else
> + utype = lang_hooks.types.type_for_mode (TYPE_MODE (utype), 1);
> +
type_for_mode? Ick. What's TREE_TYPE of that char type anyway?
Why not always
utype = build_nonstandard_integer_type (TYPE_PRECISION (TREE_TYPE
(info.index_expr)), 1);
?
Richard.
> arr_index_type = build_index_type (info.range_size);
> - tmp = create_tmp_var (TREE_TYPE (info.index_expr), "csti");
> + tmp = create_tmp_var (utype, "csui");
> add_referenced_var (tmp);
> tidx = make_ssa_name (tmp, NULL);
> - sub = fold_build2_loc (loc, MINUS_EXPR,
> - TREE_TYPE (info.index_expr), info.index_expr,
> - fold_convert_loc (loc, TREE_TYPE (info.index_expr),
> - info.range_min));
> + sub = fold_build2_loc (loc, MINUS_EXPR, utype,
> + fold_convert_loc (loc, utype, info.index_expr),
> + fold_convert_loc (loc, utype, info.range_min));
> sub = force_gimple_operand_gsi (&gsi, sub,
> false, NULL, true, GSI_SAME_STMT);
> stmt = gimple_build_assign (tidx, sub);
> @@ -780,12 +786,7 @@ gen_inbound_check (gimple swtch)
> tree label_decl2 = create_artificial_label (UNKNOWN_LOCATION);
> tree label_decl3 = create_artificial_label (UNKNOWN_LOCATION);
> gimple label1, label2, label3;
> -
> - tree utype;
> - tree tmp_u_1, tmp_u_2, tmp_u_var;
> - tree cast;
> - gimple cast_assign, minus_assign;
> - tree ulb, minus;
> + tree utype, tidx;
> tree bound;
>
> gimple cond_stmt;
> @@ -799,49 +800,24 @@ gen_inbound_check (gimple swtch)
> gcc_assert (info.default_values);
> bb0 = gimple_bb (swtch);
>
> - /* Make sure we do not generate arithmetics in a subrange. */
> - if (TREE_TYPE (TREE_TYPE (info.index_expr)))
> - utype = lang_hooks.types.type_for_mode
> - (TYPE_MODE (TREE_TYPE (TREE_TYPE (info.index_expr))), 1);
> - else
> - utype = lang_hooks.types.type_for_mode
> - (TYPE_MODE (TREE_TYPE (info.index_expr)), 1);
> + tidx = gimple_assign_lhs (info.arr_ref_first);
> + utype = TREE_TYPE (tidx);
>
> /* (end of) block 0 */
> gsi = gsi_for_stmt (info.arr_ref_first);
> - tmp_u_var = create_tmp_var (utype, "csui");
> - add_referenced_var (tmp_u_var);
> - tmp_u_1 = make_ssa_name (tmp_u_var, NULL);
> -
> - cast = fold_convert_loc (loc, utype, info.index_expr);
> - cast_assign = gimple_build_assign (tmp_u_1, cast);
> - SSA_NAME_DEF_STMT (tmp_u_1) = cast_assign;
> - gsi_insert_before (&gsi, cast_assign, GSI_SAME_STMT);
> - update_stmt (cast_assign);
> -
> - ulb = fold_convert_loc (loc, utype, info.range_min);
> - minus = fold_build2_loc (loc, MINUS_EXPR, utype, tmp_u_1, ulb);
> - minus = force_gimple_operand_gsi (&gsi, minus, false, NULL, true,
> - GSI_SAME_STMT);
> - tmp_u_2 = make_ssa_name (tmp_u_var, NULL);
> - minus_assign = gimple_build_assign (tmp_u_2, minus);
> - SSA_NAME_DEF_STMT (tmp_u_2) = minus_assign;
> - gsi_insert_before (&gsi, minus_assign, GSI_SAME_STMT);
> - update_stmt (minus_assign);
> + gsi_next (&gsi);
>
> bound = fold_convert_loc (loc, utype, info.range_size);
> - cond_stmt = gimple_build_cond (LE_EXPR, tmp_u_2, bound, NULL_TREE,
> NULL_TREE);
> + cond_stmt = gimple_build_cond (LE_EXPR, tidx, bound, NULL_TREE, NULL_TREE);
> gsi_insert_before (&gsi, cond_stmt, GSI_SAME_STMT);
> update_stmt (cond_stmt);
>
> /* block 2 */
> - gsi = gsi_for_stmt (info.arr_ref_first);
> label2 = gimple_build_label (label_decl2);
> gsi_insert_before (&gsi, label2, GSI_SAME_STMT);
> last_assign = gen_def_assigns (&gsi);
>
> /* block 1 */
> - gsi = gsi_for_stmt (info.arr_ref_first);
> label1 = gimple_build_label (label_decl1);
> gsi_insert_before (&gsi, label1, GSI_SAME_STMT);
>
> --- gcc/testsuite/gcc.c-torture/execute/pr48809.c.jj 2011-04-29
> 15:30:29.000000000 +0200
> +++ gcc/testsuite/gcc.c-torture/execute/pr48809.c 2011-04-29
> 15:29:49.000000000 +0200
> @@ -0,0 +1,60 @@
> +/* PR tree-optimization/48809 */
> +
> +extern void abort (void);
> +
> +int
> +foo (signed char x)
> +{
> + int y = 0;
> + switch (x)
> + {
> + case 0: y = 1; break;
> + case 1: y = 7; break;
> + case 2: y = 2; break;
> + case 3: y = 19; break;
> + case 4: y = 5; break;
> + case 5: y = 17; break;
> + case 6: y = 31; break;
> + case 7: y = 8; break;
> + case 8: y = 28; break;
> + case 9: y = 16; break;
> + case 10: y = 31; break;
> + case 11: y = 12; break;
> + case 12: y = 15; break;
> + case 13: y = 111; break;
> + case 14: y = 17; break;
> + case 15: y = 10; break;
> + case 16: y = 31; break;
> + case 17: y = 7; break;
> + case 18: y = 2; break;
> + case 19: y = 19; break;
> + case 20: y = 5; break;
> + case 21: y = 107; break;
> + case 22: y = 31; break;
> + case 23: y = 8; break;
> + case 24: y = 28; break;
> + case 25: y = 106; break;
> + case 26: y = 31; break;
> + case 27: y = 102; break;
> + case 28: y = 105; break;
> + case 29: y = 111; break;
> + case 30: y = 17; break;
> + case 31: y = 10; break;
> + case 32: y = 31; break;
> + case 98: y = 18; break;
> + case -62: y = 19; break;
> + }
> + return y;
> +}
> +
> +int
> +main ()
> +{
> + if (foo (98) != 18 || foo (97) != 0 || foo (99) != 0)
> + abort ();
> + if (foo (-62) != 19 || foo (-63) != 0 || foo (-61) != 0)
> + abort ();
> + if (foo (28) != 105 || foo (27) != 102 || foo (29) != 111)
> + abort ();
> + return 0;
> +}
>
> Jakub
>
