push_through_perm():

 - fixed dominance frontier IF walking the whole block upwards
 - simplified code
 - hopefully better explanation how the frontier is calculated

[r21312]

diff --git a/ir/be/belower.c b/ir/be/belower.c
index 872bd37..587b517 100644 (file)
--- a/ir/be/belower.c
+++ b/ir/be/belower.c
@@ -894,34 +894,35 @@ static int push_through_perm(ir_node *perm, void *data)
        bitset_t *moved   = bitset_alloca(arity);
        int n_moved;
        int new_size;
-       ir_node *frontier = sched_first(bl);
+       ir_node *frontier = bl;
        FIRM_DBG_REGISTER(firm_dbg_module_t *mod, "firm.be.lower.permmove");
 
        int i, n;
        const ir_edge_t *edge;
-       ir_node *last_proj = NULL, *irn;
+       ir_node *one_proj = NULL, *irn;
        const arch_register_class_t *cls = NULL;
 
        DBG((mod, LEVEL_1, "perm move %+F irg %+F\n", perm, irg));
 
-       /* get some proj and find out the register class of the proj. */
-       foreach_out_edge (perm, edge) {
-               last_proj  = get_edge_src_irn(edge);
-               cls = arch_get_irn_reg_class(aenv, last_proj, -1);
-               assert(is_Proj(last_proj));
-               break;
-       }
+       /* get some Proj and find out the register class of that Proj. */
+       edge     = get_irn_out_edge_first_kind(perm, EDGE_KIND_NORMAL);
+       one_proj = get_edge_src_irn(edge);
+       assert(is_Proj(one_proj));
+       cls      = arch_get_irn_reg_class(aenv, one_proj, -1);
 
-       /* find the point in the schedule after which the
+       /* Find the point in the schedule after which the
         * potentially movable nodes must be defined.
-        * A perm will only be pushed up to first instruction
-        * which lets an operand of itself die.  */
-
+        * A Perm will only be pushed up to first instruction
+        * which lets an operand of itself die.
+        * If we would allow to move the Perm above this instruction,
+        * the former dead operand would be live now at the point of
+        * the Perm, increasing the register pressure by one.
+        */
        sched_foreach_reverse_from (sched_prev(perm), irn) {
-               for(i = get_irn_arity(irn) - 1; i >= 0; --i) {
+               for (i = get_irn_arity(irn) - 1; i >= 0; --i) {
                        ir_node *op = get_irn_n(irn, i);
-                       if(arch_irn_consider_in_reg_alloc(aenv, cls, op)
-                               && !values_interfere(env->birg, op, last_proj)) {
+                       if (arch_irn_consider_in_reg_alloc(aenv, cls, op)
+                               && !values_interfere(env->birg, op, one_proj)) {
                                frontier = sched_next(irn);
                                goto found_front;
                        }
@@ -938,11 +939,12 @@ found_front:
                int                        input = -1;
                ir_node                   *proj;
 
+               /* search if node is a INPUT of Perm */
                foreach_out_edge(perm, edge) {
                        ir_node *out = get_edge_src_irn(edge);
                        int      pn  = get_Proj_proj(out);
                        ir_node *in  = get_irn_n(perm, pn);
-                       if(node == in) {
+                       if (node == in) {
                                proj  = out;
                                input = pn;
                                break;