a first try to propagate phi preferences upwards

[r26388]

diff --git a/ir/be/benewalloc.c b/ir/be/benewalloc.c
index b0dacd0..0a35360 100644 (file)
--- a/ir/be/benewalloc.c
+++ b/ir/be/benewalloc.c
@@ -1090,7 +1090,11 @@ static void add_phi_permutations(ir_node *block, int p)
        }
 }
 
-static void handle_phi_prefs(ir_node *phi)
+/**
+ * Set preferences for a phis register based on the registers used on the
+ * phi inputs.
+ */
+static void adapt_phi_prefs(ir_node *phi)
 {
        int i;
        int arity = get_irn_arity(phi);
@@ -1115,6 +1119,37 @@ static void handle_phi_prefs(ir_node *phi)
        }
 }
 
+/**
+ * After a phi has been assigned a register propagate preference inputs
+ * to the phi inputs.
+ */
+static void propagate_phi_register(ir_node *phi)
+{
+       int                    i;
+       ir_node               *block = get_nodes_block(phi);
+       int                    arity = get_irn_arity(phi);
+       const arch_register_t *reg   = arch_get_irn_register(phi);
+       unsigned               r     = arch_register_get_index(reg);
+
+       for (i = 0; i < arity; ++i) {
+               ir_node           *op   = get_Phi_pred(phi, i);
+               allocation_info_t *info = get_allocation_info(op);
+               ir_node           *pred;
+               float              weight;
+
+               /* already a register assigned? then we can't influence it anyway */
+               /* TODO: what about splits which we might still do... */
+               if (arch_get_irn_register(op) != NULL)
+                       continue;
+
+               pred   = get_Block_cfgpred_block(block, i);
+               weight = get_block_execfreq(execfreqs, pred);
+
+               /* promote the prefered register */
+               info->prefs[r] += AFF_PHI * weight;
+       }
+}
+
 /**
  * Walker: assign registers to all nodes of a block that
  * need registers from the currently considered register class.
@@ -1235,10 +1270,9 @@ static void allocate_coalesce_block(ir_node *block, void *data)
                if (reg != NULL) {
                        use_reg(node, reg);
                } else {
-                       /* TODO: give boni for registers already assigned at the
-                          predecessors */
-                       handle_phi_prefs(node);
+                       adapt_phi_prefs(node);
                        assign_reg(block, node);
+                       propagate_phi_register(node);
                }
        }
        start = node;
@@ -1250,6 +1284,12 @@ static void allocate_coalesce_block(ir_node *block, void *data)
                        continue;
 
                assign_reg(block, node);
+               /* shouldn't happen if we color in dominance order */
+               assert (!is_Phi(node));
+#if 0
+               if (is_Phi(node))
+                       propagate_phi_register(node);
+#endif
        }
 
        /* assign instructions in the block */