Simplify if_statement_to_firm() so it in particular does not create a critical edge...

- The then part is constructed before the else part now.
- No explicit block after the if statement is created if the then or else parts do not jump there.

diff --git a/ast2firm.c b/ast2firm.c
index c6b9796..875f1d9 100644 (file)
--- a/ast2firm.c
+++ b/ast2firm.c
@@ -4739,41 +4739,33 @@ static void if_statement_to_firm(if_statement_t *statement)
                false_block = new_immBlock();
                create_condition_evaluation(statement->condition, true_block, false_block);
                mature_immBlock(true_block);
-       }
-
-       /* Create the false statement.
-        * Handle false before true, so if no false statement is present, then the
-        * empty false block is reused as fallthrough block. */
-       ir_node *fallthrough_block = NULL;
-       if (statement->false_statement != NULL) {
-               if (false_block != NULL) {
-                       mature_immBlock(false_block);
-               }
-               set_cur_block(false_block);
-               statement_to_firm(statement->false_statement);
-               if (currently_reachable()) {
-                       fallthrough_block = new_immBlock();
-                       add_immBlock_pred(fallthrough_block, new_Jmp());
-               }
-       } else {
-               fallthrough_block = false_block;
+               mature_immBlock(false_block);
        }
 
        /* Create the true statement. */
        set_cur_block(true_block);
        statement_to_firm(statement->true_statement);
-       if (currently_reachable()) {
-               if (fallthrough_block == NULL) {
-                       fallthrough_block = new_immBlock();
-               }
-               add_immBlock_pred(fallthrough_block, new_Jmp());
+       ir_node *fallthrough_block = get_cur_block();
+
+       /* Create the false statement. */
+       set_cur_block(false_block);
+       if (statement->false_statement != NULL) {
+               statement_to_firm(statement->false_statement);
        }
 
-       /* Handle the block after the if-statement. */
-       if (fallthrough_block != NULL) {
-               mature_immBlock(fallthrough_block);
+       /* Handle the block after the if-statement.  Minor simplification and
+        * optimisation: Reuse the false/true block as fallthrough block, if the
+        * true/false statement does not pass control to the fallthrough block, e.g.
+        * in the typical if (x) return; pattern. */
+       if (fallthrough_block) {
+               if (currently_reachable()) {
+                       ir_node *const t_jump = new_r_Jmp(fallthrough_block);
+                       ir_node *const f_jump = new_Jmp();
+                       ir_node *const in[]   = { t_jump, f_jump };
+                       fallthrough_block = new_Block(2, in);
+               }
+               set_cur_block(fallthrough_block);
        }
-       set_cur_block(fallthrough_block);
 }
 
 /* Create a jump node which jumps into target_block, if the current block is