If a color colors all nodes in a chunk, other colors will not be tried anymore.

Missing is a color sequence detection; at the moment, colors are used from 0..k-1.
This is probably not so superb

[r14864]

diff --git a/ir/be/becopyheur4.c b/ir/be/becopyheur4.c
index 8d202ca..ee97153 100644 (file)
--- a/ir/be/becopyheur4.c
+++ b/ir/be/becopyheur4.c
@@ -1001,7 +1001,7 @@ static int change_node_color(co_mst_env_t *env, co_mst_irn_t *node, int tgt_col,
                return res;
        }
 
-       DEBUG_ONLY(
+#ifndef NDEBUG
                if (firm_dbg_get_mask(dbg) & LEVEL_4) {
                        if (node->fixed || node->tmp_fixed)
                                DB((dbg, LEVEL_4, "\t\tCNC: %+F has already fixed color %d\n", node->irn, col));
@@ -1011,7 +1011,7 @@ static int change_node_color(co_mst_env_t *env, co_mst_irn_t *node, int tgt_col,
                                DB((dbg, LEVEL_4, ")\n"));
                        }
                }
-       )
+#endif
 
        return 0;
 }
@@ -1023,6 +1023,7 @@ static int change_node_color(co_mst_env_t *env, co_mst_irn_t *node, int tgt_col,
 static void color_aff_chunk(co_mst_env_t *env, aff_chunk_t *c) {
        aff_chunk_t *best_chunk   = NULL;
        int         best_color    = -1;
+       int         did_all       = 0;
        waitq       *changed_ones = new_waitq();
        waitq       *tmp_chunks   = new_waitq();
        waitq       *best_starts  = NULL;
@@ -1034,8 +1035,15 @@ static void color_aff_chunk(co_mst_env_t *env, aff_chunk_t *c) {
        DB((dbg, LEVEL_2, "\n"));
 
 
-       /* check which color is the "best" for the given chunk */
-       for (col = 0; col < env->n_regs; ++col) {
+       /* check which color is the "best" for the given chunk.
+        * if we found a color which was ok for all nodes, we take it
+        * and do not look further. (see did_all flag usage below.)
+        * If we have many colors which fit all nodes it is hard to decide
+        * which one to take anyway.
+        * TODO Sebastian: Perhaps we should at all nodes and figure out
+        * a suitable color using costs as done above (determine_color_costs).
+        */
+       for (col = 0; col < env->n_regs && !did_all; ++col) {
                int         one_good     = 0;
                waitq       *good_starts = new_waitq();
                aff_chunk_t *local_best;
@@ -1046,6 +1054,9 @@ static void color_aff_chunk(co_mst_env_t *env, aff_chunk_t *c) {
 
                DB((dbg, LEVEL_3, "\ttrying color %d\n", col));
 
+               /* suppose we can color all nodes to the same color */
+               did_all = 1;
+
                /* try to bring all nodes of given chunk to the current color. */
                for (idx = 0, len = ARR_LEN(c->n); idx < len; ++idx) {
                        ir_node      *irn  = c->n[idx];
@@ -1063,6 +1074,7 @@ static void color_aff_chunk(co_mst_env_t *env, aff_chunk_t *c) {
                        if (good)
                                waitq_put(good_starts, node);
                        one_good |= good;
+                       did_all  &= good;
 
                        DB((dbg, LEVEL_4, "\t\t... %+F attempt from %d to %d %s\n", irn, node->col, col, one_good ? "succeeded" : "failed"));
                }