cfopt can skip jump blocks now

The preconditions were too tight

diff --git a/ir/opt/cfopt.c b/ir/opt/cfopt.c
index 12df7ed..20a70f3 100644 (file)
--- a/ir/opt/cfopt.c
+++ b/ir/opt/cfopt.c
@@ -669,7 +669,7 @@ static void remove_empty_blocks(ir_node *block, void *x)
        int n_preds = get_Block_n_cfgpreds(block);
 
        for (i = 0; i < n_preds; ++i) {
-               ir_node *jmp, *jmp_block, *pred, *pred_block;
+               ir_node *jmp, *jmp_block;
                int n_jpreds = 0;
 
                jmp = get_Block_cfgpred(block, i);
@@ -680,8 +680,6 @@ static void remove_empty_blocks(ir_node *block, void *x)
                        continue; /* this infinite loop cannot be optimized any further */
                if (is_unknown_jump_target(&env->block_infos, jmp_block))
                        continue; /* unknown jump target must not be optimized */
-               if (has_operations(&env->block_infos,jmp_block))
-                       continue; /* this block contains operations and cannot be skipped */
                if (has_phis(&env->block_infos,jmp_block))
                        continue; /* this block contains Phis and is not skipped */
                if (Block_block_visited(jmp_block)) {
@@ -708,6 +706,15 @@ static void remove_empty_blocks(ir_node *block, void *x)
                 * if block has no Phis.
                 */
                if (n_jpreds == 1) {
+                       ir_node *pred        = get_Block_cfgpred(jmp_block, 0);
+                       ir_node *pred_block  = get_nodes_block(pred);
+                       if (has_operations(&env->block_infos,jmp_block)) {
+                               if (get_irg_start_block(get_irn_irg(pred_block)) == pred_block)
+                                       continue; /* must not merge operations into start block */
+                               if (!is_Jmp(pred))
+                                       continue; /* must not create partially dead code, especially when it is mode_M */
+                       }
+
                        /* skip jmp block by rerouting its predecessor to block
                         *
                         *     A              A
@@ -716,14 +723,14 @@ static void remove_empty_blocks(ir_node *block, void *x)
                         *     |              |
                         *   block          block
                         */
-                       pred = get_Block_cfgpred(jmp_block, 0);
                        exchange(jmp, pred);
 
                        /* cleanup: jmp_block might have a Keep edge! */
-                       pred_block = get_nodes_block(pred);
                        exchange(jmp_block, pred_block);
                        env->changed = true;
-               } else if (! has_phis(&env->block_infos, block)) {
+               } else if ( !has_phis(&env->block_infos, block) &&
+                           !has_operations(&env->block_infos,jmp_block))
+               {
                        /* all predecessors can skip the jmp block, so block gets some new
                         * predecessors
                         *
@@ -742,7 +749,7 @@ static void remove_empty_blocks(ir_node *block, void *x)
                        }
                        /* now append the new predecessors */
                        for (j = 0; j < n_jpreds; ++j) {
-                               pred = get_Block_cfgpred(jmp_block, j);
+                               ir_node *pred = get_Block_cfgpred(jmp_block, j);
                                ins[n_preds+j] = pred;
                        }
                        set_irn_in(block, n_preds+n_jpreds, ins);