Avoid an unnecessary basic block in case of do ... while (0);.

diff --git a/ast2firm.c b/ast2firm.c
index 7f0e78b..1447635 100644 (file)
--- a/ast2firm.c
+++ b/ast2firm.c
@@ -4542,30 +4542,36 @@ static ir_node *do_while_statement_to_firm(do_while_statement_t *statement)
        /* create the header block */
        ir_node *header_block = new_immBlock();
 
-       /* the loop body */
-       ir_node *body_block = new_immBlock();
-       jump_to(body_block);
-
        PUSH_BREAK(NULL);
        PUSH_CONTINUE(header_block);
 
+       /* The loop body. */
+       ir_node            *body_block = NULL;
+       expression_t *const cond       = statement->condition;
+       /* Avoid an explicit body block in case of do ... while (0);. */
+       if (is_constant_expression(cond) != EXPR_CLASS_CONSTANT || fold_constant_to_bool(cond)) {
+               /* Not do ... while (0);. */
+               body_block = new_immBlock();
+               jump_to(body_block);
+       }
        statement_to_firm(statement->body);
-       ir_node *const false_block = get_break_label();
-
-       POP_CONTINUE();
-       POP_BREAK();
-
-       jump_if_reachable(header_block);
 
        /* create the condition */
+       jump_if_reachable(header_block);
        mature_immBlock(header_block);
        set_cur_block(header_block);
-
-       create_condition_evaluation(statement->condition, body_block, false_block);
-       mature_immBlock(body_block);
+       ir_node *const false_block = get_break_label();
+       if (body_block) {
+               create_condition_evaluation(statement->condition, body_block, false_block);
+               mature_immBlock(body_block);
+       } else {
+               jump_if_reachable(false_block);
+       }
        mature_immBlock(false_block);
-
        set_cur_block(false_block);
+
+       POP_CONTINUE();
+       POP_BREAK();
        return NULL;
 }