On 6/29/17 8:58 AM, Richard Biener wrote:
> On Thu, 29 Jun 2017, Peter Bergner wrote:
>
>> On 6/29/17 4:03 AM, Richard Biener wrote:
>>>
>>> This refactors things a bit to make CFG cleanup handle switches with
>>> just a default label. If we make sure to cleanup the CFG after
>>> group_case_labels removes cases with just __builtin_unreachable ()
>>> inside then this fixes the ICE seen in PR81994 as well.
>>>
>>> I wonder if find_taken_edge should generally handle successors
>>> with __builtin_unreachable () -- OTOH that would get rid of those
>>> too early I guess.
>>
>> Should we offer an early out of group_case_labels_stmt() for the
>> fairly common case of new_size == old_size? There's no reason to
>> execute the compress labels loop if we didn't combine any of the
>> labels.
>
> We can also merge both loops, counting new_size upwards, storing
> to label new_size if new_size != i ...
Like this. I'm bootstrapping and regtesting the following patch on
powerpc64le-linux. Ok if it survives?
Peter
* tree-cfg.c (group_case_labels_stmt): Merge scanning and compressing
loops. Remove now unneeded calls to gimple_switch_set_label() that
just set removed labels to NULL_TREE.
Index: gcc/tree-cfg.c
===================================================================
--- gcc/tree-cfg.c (revision 249801)
+++ gcc/tree-cfg.c (working copy)
@@ -1679,13 +1679,13 @@ bool
group_case_labels_stmt (gswitch *stmt)
{
int old_size = gimple_switch_num_labels (stmt);
- int i, j, base_index, new_size = old_size;
+ int i, next_index, new_size;
basic_block default_bb = NULL;
default_bb = label_to_block (CASE_LABEL (gimple_switch_default_label
(stmt)));
/* Look for possible opportunities to merge cases. */
- i = 1;
+ new_size = i = 1;
while (i < old_size)
{
tree base_case, base_high;
@@ -1699,23 +1699,21 @@ group_case_labels_stmt (gswitch *stmt)
/* Discard cases that have the same destination as the default case. */
if (base_bb == default_bb)
{
- gimple_switch_set_label (stmt, i, NULL_TREE);
i++;
- new_size--;
continue;
}
base_high = CASE_HIGH (base_case)
? CASE_HIGH (base_case)
: CASE_LOW (base_case);
- base_index = i++;
+ next_index = i + 1;
/* Try to merge case labels. Break out when we reach the end
of the label vector or when we cannot merge the next case
label with the current one. */
- while (i < old_size)
+ while (next_index < old_size)
{
- tree merge_case = gimple_switch_label (stmt, i);
+ tree merge_case = gimple_switch_label (stmt, next_index);
basic_block merge_bb = label_to_block (CASE_LABEL (merge_case));
wide_int bhp1 = wi::add (base_high, 1);
@@ -1727,9 +1725,7 @@ group_case_labels_stmt (gswitch *stmt)
base_high = CASE_HIGH (merge_case) ?
CASE_HIGH (merge_case) : CASE_LOW (merge_case);
CASE_HIGH (base_case) = base_high;
- gimple_switch_set_label (stmt, i, NULL_TREE);
- new_size--;
- i++;
+ next_index++;
}
else
break;
@@ -1742,23 +1738,22 @@ group_case_labels_stmt (gswitch *stmt)
edge base_edge = find_edge (gimple_bb (stmt), base_bb);
if (base_edge != NULL)
remove_edge_and_dominated_blocks (base_edge);
- gimple_switch_set_label (stmt, base_index, NULL_TREE);
- new_size--;
+ i = next_index;
+ continue;
}
- }
- /* Compress the case labels in the label vector, and adjust the
- length of the vector. */
- for (i = 0, j = 0; i < new_size; i++)
- {
- while (! gimple_switch_label (stmt, j))
- j++;
- gimple_switch_set_label (stmt, i,
- gimple_switch_label (stmt, j++));
+ if (new_size < i)
+ gimple_switch_set_label (stmt, new_size,
+ gimple_switch_label (stmt, i));
+ i = next_index;
+ new_size++;
}
gcc_assert (new_size <= old_size);
- gimple_switch_set_num_labels (stmt, new_size);
+
+ if (new_size < old_size)
+ gimple_switch_set_num_labels (stmt, new_size);
+
return new_size < old_size;
}
