* tree-ssa-ccp.c (get_default_value): If we have a constant

	value recorded for an SSA_NAME, then use that constant as
	the initial lattice value.
	(substitute_and_fold): Transfer equivalences discovered into
	SSA_NAME_EQUIV.

	* tree.h (SSA_NAME_EQUIV): Add comments.
	(SET_SSA_NAME_EQUIV): Similarly.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@87844 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 28 insertions, 1 deletions

diff --git a/gcc/tree-ssa-ccp.c b/gcc/tree-ssa-ccp.c
index 81ce67321c5..5fe1e1de66f 100644
--- a/gcc/tree-ssa-ccp.c
+++ b/gcc/tree-ssa-ccp.c
@@ -135,7 +135,14 @@ get_default_value (tree var)
   val.lattice_val = UNDEFINED;
   val.const_val = NULL_TREE;
 
-  if (TREE_CODE (sym) == PARM_DECL || TREE_THIS_VOLATILE (sym))
+  if (TREE_CODE (var) == SSA_NAME
+      && SSA_NAME_EQUIV (var)
+      && is_gimple_min_invariant (SSA_NAME_EQUIV (var)))
+    {
+      val.lattice_val = CONSTANT;
+      val.const_val = SSA_NAME_EQUIV (var);
+    }
+  else if (TREE_CODE (sym) == PARM_DECL || TREE_THIS_VOLATILE (sym))
     {
       /* Function arguments and volatile variables are considered VARYING.  */
       val.lattice_val = VARYING;
@@ -512,6 +519,7 @@ static void
 substitute_and_fold (void)
 {
   basic_block bb;
+  unsigned int i;
 
   if (dump_file && (dump_flags & TDF_DETAILS))
     fprintf (dump_file,
@@ -586,6 +594,25 @@ substitute_and_fold (void)
 	    }
 	}
     }
+
+  /* And transfer what we learned from VALUE_VECTOR into the
+     SSA_NAMEs themselves.  This probably isn't terribly important
+     since we probably constant propagated the values to their
+     use sites above.  */
+  for (i = 0; i < num_ssa_names; i++)
+    {
+      tree name = ssa_name (i);
+      value *value;
+
+      if (!name)
+	continue;
+
+      value = get_value (name);
+      if (value->lattice_val == CONSTANT
+          && is_gimple_reg (name)
+	  && is_gimple_min_invariant (value->const_val))
+	SET_SSA_NAME_EQUIV (name, value->const_val)
+    }
 }