On Mon, Jul 9, 2012 at 12:57 PM, Steven Bosscher <stevenb....@gmail.com> wrote:
> Hello,
>
> How annoying that it was decided at some point to not always group
> switch case labels in tree-cfgcleanup! This PR53887 and PR53881 before
> it are both cases where the switch lowering to bit tests ICEs because
> the case labels haven't been grouped. For PR53887 there is a case
> label that shares an edge with the default label, and for PR53881
> there were two cases going to the same basic block (i.e. same edge)
> but with different CASE_LABELs.
>
> The most robust fix is to group the case labels before trying the
> switch lowering. This also helps for switch conversion to a load from
> a static initializer because before this patch the heuristics were
> being fooled to perform unprofitable conversions.
>
> Bootstrapped on powerpc64-unknown-linux-gnu, testing in progress. OK
> if it passes?
Ok.
Thanks,
Richard.
> Ciao!
> Steven
>
> gcc/
> PR tree-optimization/53887
> * tree-cfg.c (group_case_labels_stmt): Make non-static.
> * tree-flow.h (group_case_labels_stmt): Add prototype.
> * tree-switch-conversion.c (process_switch): Use
> group_case_labels_stmt
> to pre-process every switch.
>
> testsuite/
> PR tree-optimization/53887
> * gcc.dg/pr53887.c: New test.
>
> Index: tree-cfg.c
> ===================================================================
> --- tree-cfg.c (revision 189366)
> +++ tree-cfg.c (working copy)
> @@ -125,7 +125,6 @@ static edge find_taken_edge_computed_goto (basic_b
> static edge find_taken_edge_cond_expr (basic_block, tree);
> static edge find_taken_edge_switch_expr (basic_block, tree);
> static tree find_case_label_for_value (gimple, tree);
> -static void group_case_labels_stmt (gimple);
>
> void
> init_empty_tree_cfg_for_function (struct function *fn)
> @@ -1331,7 +1330,7 @@ cleanup_dead_labels (void)
> the ones jumping to the same label.
> Eg. three separate entries 1: 2: 3: become one entry 1..3: */
>
> -static void
> +void
> group_case_labels_stmt (gimple stmt)
> {
> int old_size = gimple_switch_num_labels (stmt);
> Index: tree-flow.h
> ===================================================================
> --- tree-flow.h (revision 189366)
> +++ tree-flow.h (working copy)
> @@ -428,6 +428,7 @@ extern void debug_loop_num (unsigned, int);
> extern void print_loops (FILE *, int);
> extern void print_loops_bb (FILE *, basic_block, int, int);
> extern void cleanup_dead_labels (void);
> +extern void group_case_labels_stmt (gimple);
> extern void group_case_labels (void);
> extern gimple first_stmt (basic_block);
> extern gimple last_stmt (basic_block);
> Index: tree-switch-conversion.c
> ===================================================================
> --- tree-switch-conversion.c (revision 189366)
> +++ tree-switch-conversion.c (working copy)
> @@ -1339,9 +1339,15 @@ process_switch (gimple swtch)
> {
> struct switch_conv_info info;
>
> - /* Degenerate case with only a default label should never happen. */
> - gcc_checking_assert (gimple_switch_num_labels (swtch) > 1);
> + /* Group case labels so that we get the right results from the heuristics
> + that decide on the code generation approach for this switch. */
> + group_case_labels_stmt (swtch);
>
> + /* If this switch is now a degenerate case with only a default label,
> + there is nothing left for us to do. */
> + if (gimple_switch_num_labels (swtch) < 2)
> + return "switch is a degenerate case";
> +
> collect_switch_conv_info (swtch, &info);
>
> /* No error markers should reach here (they should be filtered out
> Index: testsuite/gcc.dg/pr53887.c
> ===================================================================
> --- testsuite/gcc.dg/pr53887.c (revision 0)
> +++ testsuite/gcc.dg/pr53887.c (revision 0)
> @@ -0,0 +1,24 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +
> +enum
> +{ Failed, NoError, NoDiskette }
> +a;
> +int b, c;
> +void
> +fn1 ()
> +{
> + if (c)
> + a << 1;
> + switch (b)
> + {
> + default:
> + a << 1;
> + case 0:
> + b = 0;
> + case 1:
> + case NoDiskette:
> + ;
> + }
> +}
> +
