return GS_ALL_DONE;
}
+/* Compare two case labels. Because the front end should already have
+ made sure that case ranges do not overlap, it is enough to only compare
+ the CASE_LOW values of each case label. */
+
+static int
+compare_case_labels (const void *p1, const void *p2)
+{
+ tree case1 = *(tree *)p1;
+ tree case2 = *(tree *)p2;
+
+ return tree_int_cst_compare (CASE_LOW (case1), CASE_LOW (case2));
+}
+
/* Gimplify a SWITCH_EXPR, and collect a TREE_VEC of the labels it can
branch to. */
if (SWITCH_BODY (switch_expr))
{
varray_type labels, saved_labels;
- bool saw_default;
- tree label_vec, t;
+ tree label_vec, default_case = NULL_TREE;
size_t i, len;
/* If someone can be bothered to fill in the labels, they can
gimplify_ctxp->case_labels = saved_labels;
len = VARRAY_ACTIVE_SIZE (labels);
- saw_default = false;
for (i = 0; i < len; ++i)
{
- t = VARRAY_TREE (labels, i);
+ tree t = VARRAY_TREE (labels, i);
if (!CASE_LOW (t))
{
- saw_default = true;
+ /* The default case must be the last label in the list. */
+ default_case = t;
+ VARRAY_TREE (labels, i) = VARRAY_TREE (labels, len - 1);
+ len--;
break;
}
}
- label_vec = make_tree_vec (len + !saw_default);
+ label_vec = make_tree_vec (len + 1);
SWITCH_LABELS (*expr_p) = label_vec;
-
- for (i = 0; i < len; ++i)
- TREE_VEC_ELT (label_vec, i) = VARRAY_TREE (labels, i);
-
append_to_statement_list (switch_expr, pre_p);
- /* If the switch has no default label, add one, so that we jump
- around the switch body. */
- if (!saw_default)
+ if (! default_case)
{
- t = build (CASE_LABEL_EXPR, void_type_node, NULL_TREE,
- NULL_TREE, create_artificial_label ());
- TREE_VEC_ELT (label_vec, len) = t;
+ /* If the switch has no default label, add one, so that we jump
+ around the switch body. */
+ default_case = build (CASE_LABEL_EXPR, void_type_node, NULL_TREE,
+ NULL_TREE, create_artificial_label ());
append_to_statement_list (SWITCH_BODY (switch_expr), pre_p);
- *expr_p = build (LABEL_EXPR, void_type_node, CASE_LABEL (t));
+ *expr_p = build (LABEL_EXPR, void_type_node,
+ CASE_LABEL (default_case));
}
else
*expr_p = SWITCH_BODY (switch_expr);
+ qsort (&VARRAY_TREE (labels, 0), len, sizeof (tree),
+ compare_case_labels);
+ for (i = 0; i < len; ++i)
+ TREE_VEC_ELT (label_vec, i) = VARRAY_TREE (labels, i);
+ TREE_VEC_ELT (label_vec, len) = default_case;
+
SWITCH_BODY (switch_expr) = NULL;
}
else if (!SWITCH_LABELS (switch_expr))
static void tree_merge_blocks (basic_block, basic_block);
static bool tree_can_merge_blocks_p (basic_block, basic_block);
static void remove_bb (basic_block);
+static void group_case_labels (void);
static void cleanup_dead_labels (void);
static bool cleanup_control_flow (void);
static bool cleanup_control_expr_graph (basic_block, block_stmt_iterator);
/* Adjust the size of the array. */
VARRAY_GROW (basic_block_info, n_basic_blocks);
+ /* To speed up statement iterator walks, we first purge dead labels. */
+ cleanup_dead_labels ();
+
+ /* Group case nodes to reduce the number of edges.
+ We do this after cleaning up dead labels because otherwise we miss
+ a lot of obvious case merging opportunities. */
+ group_case_labels ();
+
/* Create the edges of the flowgraph. */
make_edges ();
builder inserted for completeness. */
remove_fake_edges ();
- /* To speed up statement iterator walks, we first purge dead labels. */
- cleanup_dead_labels ();
-
/* Clean up the graph and warn for unreachable code. */
cleanup_tree_cfg ();
}
break;
}
+ /* We have to handle GOTO_EXPRs until they're removed, and we don't
+ remove them until after we've created the CFG edges. */
+ case GOTO_EXPR:
+ {
+ tree label = GOTO_DESTINATION (stmt);
+ if (! computed_goto_p (stmt))
+ GOTO_DESTINATION (stmt) =
+ label_for_bb[label_to_block (label)->index];
+ break;
+ }
+
default:
break;
}
free (label_for_bb);
}
+/* Look for blocks ending in a multiway branch (a SWITCH_EXPR in GIMPLE),
+ and scan the sorted vector of cases. Combine the ones jumping to the
+ same label.
+ Eg. three separate entries 1: 2: 3: become one entry 1..3: */
+
+static void
+group_case_labels (void)
+{
+ basic_block bb;
+
+ FOR_EACH_BB (bb)
+ {
+ tree stmt = last_stmt (bb);
+ if (stmt && TREE_CODE (stmt) == SWITCH_EXPR)
+ {
+ tree labels = SWITCH_LABELS (stmt);
+ int old_size = TREE_VEC_LENGTH (labels);
+ int i, j, new_size = old_size;
+
+ /* Look for possible opportunities to merge cases.
+ Ignore the last element of the label vector because it
+ must be the default case. */
+ i = 0;
+ while (i < old_size - 2)
+ {
+ tree base_case, base_label, base_high, type;
+ base_case = TREE_VEC_ELT (labels, i);
+
+ if (! base_case)
+ abort ();
+
+ type = TREE_TYPE (CASE_LOW (base_case));
+ base_label = CASE_LABEL (base_case);
+ base_high = CASE_HIGH (base_case) ?
+ CASE_HIGH (base_case) : CASE_LOW (base_case);
+
+ /* 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 - 2)
+ {
+ tree merge_case = TREE_VEC_ELT (labels, ++i);
+ tree merge_label = CASE_LABEL (merge_case);
+ tree t = int_const_binop (PLUS_EXPR, base_high,
+ integer_one_node, 1);
+
+ /* Merge the cases if they jump to the same place,
+ and their ranges are consecutive. */
+ if (merge_label == base_label
+ && tree_int_cst_equal (CASE_LOW (merge_case), t))
+ {
+ base_high = CASE_HIGH (merge_case) ?
+ CASE_HIGH (merge_case) : CASE_LOW (merge_case);
+ CASE_HIGH (base_case) = base_high;
+ TREE_VEC_ELT (labels, i) = NULL_TREE;
+ new_size--;
+ }
+ else
+ break;
+ }
+ }
+
+ /* 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 (! TREE_VEC_ELT (labels, j))
+ j++;
+ TREE_VEC_ELT (labels, i) = TREE_VEC_ELT (labels, j++);
+ }
+ TREE_VEC_LENGTH (labels) = new_size;
+ }
+ }
+}
/* Checks whether we can merge block B into block A. */
}
-/* Return the CASE_LABEL_EXPR that SWITCH_EXPR will take for VAL. */
+/* Return the CASE_LABEL_EXPR that SWITCH_EXPR will take for VAL.
+ We can make optimal use here of the fact that the case labels are
+ sorted: We can do a binary search for a case matching VAL. */
static tree
find_case_label_for_value (tree switch_expr, tree val)
{
tree vec = SWITCH_LABELS (switch_expr);
- size_t i, n = TREE_VEC_LENGTH (vec);
- tree default_case = NULL;
+ size_t low, high, n = TREE_VEC_LENGTH (vec);
+ tree default_case = TREE_VEC_ELT (vec, n - 1);
- for (i = 0; i < n; ++i)
+ for (low = -1, high = n - 1; high - low > 1; )
{
+ size_t i = (high + low) / 2;
tree t = TREE_VEC_ELT (vec, i);
+ int cmp;
- if (CASE_LOW (t) == NULL)
- default_case = t;
- else if (CASE_HIGH (t) == NULL)
+ /* Cache the result of comparing CASE_LOW and val. */
+ cmp = tree_int_cst_compare (CASE_LOW (t), val);
+
+ if (cmp > 0)
+ high = i;
+ else
+ low = i;
+
+ if (CASE_HIGH (t) == NULL)
{
- /* A `normal' case label. */
- if (tree_int_cst_equal (CASE_LOW (t), val))
+ /* A singe-valued case label. */
+ if (cmp == 0)
return t;
}
else
{
/* A case range. We can only handle integer ranges. */
- if (tree_int_cst_compare (CASE_LOW (t), val) <= 0
- && tree_int_cst_compare (CASE_HIGH (t), val) >= 0)
+ if (cmp <= 0 && tree_int_cst_compare (CASE_HIGH (t), val) >= 0)
return t;
}
}
- if (!default_case)
- abort ();
-
return default_case;
}
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