re PR tree-optimization/19038 (tree-ssa causing loops to have more than one BB)

2005-01-20  Daniel Berlin  <dberlin@dberlin.org>

	Fix PR tree-optimization/19038
	* tree-ssa-dom.c (cprop_operand): Don't replace loop invaeriant
	copies with loop variant ones.

From-SVN: r94069

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 73db887aff196fdc647d3be635274c89ee69068a..1a9d9e6cbb72f850d370ec5325f469654ffd10f3 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2005-01-20  Daniel Berlin  <dberlin@dberlin.org>
+
+       Fix PR tree-optimization/19038
+       * tree-ssa-dom.c (cprop_operand): Don't replace loop invaeriant
+       copies with loop variant ones.
+
 2005-01-22  Kazu Hirata  <kazu@cs.umass.edu>
 
        * cfganal.c, real.h, reorg.c, timevar.def, tree-ssa-ccp.c,

diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c
index 35847ec3f28cb70a240b25c437fb75923bd79f42..68147989e4943fcfa24c226820a5c6742fd6d5d7 100644 (file)
--- a/gcc/tree-ssa-dom.c
+++ b/gcc/tree-ssa-dom.c
@@ -2819,6 +2819,14 @@ cprop_operand (tree stmt, use_operand_p op_p)
         extensions.  */
       else if (!may_propagate_copy (op, val))
        return false;
+      
+      /* Do not propagate copies if the propagated value is at a deeper loop
+        depth than the propagatee.  Otherwise, this may move loop variant
+        variables outside of their loops and prevent coalescing
+        opportunities.  If the value was loop invariant, it will be hoisted
+        by LICM and exposed for copy propagation.  */
+      if (loop_depth_of_name (val) > loop_depth_of_name (op))
+       return false;
 
       /* Dump details.  */
       if (dump_file && (dump_flags & TDF_DETAILS))