X-Git-Url: http://nsz.repo.hu/git/?a=blobdiff_plain;f=ir%2Fopt%2Freassoc.c;h=66174bb8e80dbbaac35f5a7c8bcde3cbac475855;hb=f274dcf35aa0d3f4748387dbddfe50e8d7d44951;hp=5e5a163d0cfba060dd96089e775fb1b7623b206c;hpb=a271fae214fe0c6111298477a7b02983ca7b46c4;p=libfirm

diff --git a/ir/opt/reassoc.c b/ir/opt/reassoc.c
index 5e5a163d0..66174bb8e 100644
--- a/ir/opt/reassoc.c
+++ b/ir/opt/reassoc.c
@@ -28,7 +28,7 @@
 # include "irloop.h"
 # include "debug.h"
 
-static firm_dbg_module_t *dbg;
+DEBUG_ONLY(static firm_dbg_module_t *dbg;)
 
 typedef struct _walker_t {
   int changes;          /* set, if a reassociation take place */
@@ -311,12 +311,23 @@ static int reassoc_Mul(ir_node **node)
       mode  = get_mode_from_ops(in[0], in[1]);
       irn   = optimize_node(new_ir_node(NULL, current_ir_graph, block, op, mode, 2, in));
 
-      DBG((dbg, LEVEL_5, "Applied: (%n .%s. %n) %n %n => (%n %n %n) .%s. (%n %n %n)\n",
-          t1, get_op_name(op), t2, n, c, t1, n, c, get_op_name(op), t2, n, c));
-      exchange(n, irn);
-		  *node = irn;
+      /* In some cases it might happen that the new irn is equal the old one, for
+       * instance in:
+       * (x - 1) * y == x * y - y
+       * will be transformed back by simpler optimization
+       * We could switch simple optimizations off, but this only happens iff y
+       * is a loop-invariant expreassion and that it is not clear if the new form
+       * is better.
+       * So, we let the old one.
+       */
+      if (irn != n) {
+        DBG((dbg, LEVEL_5, "Applied: (%n .%s. %n) %n %n => (%n %n %n) .%s. (%n %n %n)\n",
+            t1, get_op_name(op), t2, n, c, t1, n, c, get_op_name(op), t2, n, c));
+        exchange(n, irn);
+		    *node = irn;
 
-      return 1;
+        return 1;
+      }
     }
   }
   return 0;
@@ -413,5 +424,5 @@ ir_op_ops *firm_set_default_reassoc(opcode code, ir_op_ops *ops)
 /* initialize the reassociation by adding operations to some opcodes */
 void firm_init_reassociation(void)
 {
-  dbg = firm_dbg_register("firm.opt.reassoc");
+  FIRM_DBG_REGISTER(dbg, "firm.opt.reassoc");
 }