Enhance SCEV to follow copies of SSA_NAMEs.

(Fixes missed vectorization of gcc.dg/vect/pr65947-2.c.)

        * tree-scalar-evolution.c (follow_copies_to_constant): New.
        (analyze_initial_condition, analyze_scalar_evolution_1): Call previous.

From-SVN: r232509

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 26d7af09aed960bd323199f9ad199e1442bbb184..8e2b6e6849fe8b0c95544655704c9cd8bf76beac 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2016-01-18  Alan Lawrence  <alan.lawrence@arm.com>
+
+       * tree-scalar-evolution.c (follow_copies_to_constant): New.
+       (analyze_initial_condition, analyze_scalar_evolution_1): Call previous.
+
 2016-01-18  Alan Lawrence  <alan.lawrence@arm.com>
 
        PR target/63679

diff --git a/gcc/tree-scalar-evolution.c b/gcc/tree-scalar-evolution.c
index 2bfc50fd0168ee9457241d26b0f3dd5c9c276544..c36a0398db62bdf882d7f8613ab9162f1390f2e7 100644 (file)
--- a/gcc/tree-scalar-evolution.c
+++ b/gcc/tree-scalar-evolution.c
@@ -1522,6 +1522,34 @@ analyze_evolution_in_loop (gphi *loop_phi_node,
   return evolution_function;
 }
 
+/* Looks to see if VAR is a copy of a constant (via straightforward assignments
+   or degenerate phi's).  If so, returns the constant; else, returns VAR.  */
+
+static tree
+follow_copies_to_constant (tree var)
+{
+  tree res = var;
+  while (TREE_CODE (res) == SSA_NAME)
+    {
+      gimple *def = SSA_NAME_DEF_STMT (res);
+      if (gphi *phi = dyn_cast <gphi *> (def))
+       {
+         if (tree rhs = degenerate_phi_result (phi))
+           res = rhs;
+         else
+           break;
+       }
+      else if (gimple_assign_single_p (def))
+       /* Will exit loop if not an SSA_NAME.  */
+       res = gimple_assign_rhs1 (def);
+      else
+       break;
+    }
+  if (CONSTANT_CLASS_P (res))
+    return res;
+  return var;
+}
+
 /* Given a loop-phi-node, return the initial conditions of the
    variable on entry of the loop.  When the CCP has propagated
    constants into the loop-phi-node, the initial condition is
@@ -1574,21 +1602,9 @@ analyze_initial_condition (gphi *loop_phi_node)
   if (init_cond == chrec_not_analyzed_yet)
     init_cond = chrec_dont_know;
 
-  /* During early loop unrolling we do not have fully constant propagated IL.
-     Handle degenerate PHIs here to not miss important unrollings.  */
-  if (TREE_CODE (init_cond) == SSA_NAME)
-    {
-      gimple *def = SSA_NAME_DEF_STMT (init_cond);
-      if (gphi *phi = dyn_cast <gphi *> (def))
-       {
-         tree res = degenerate_phi_result (phi);
-         if (res != NULL_TREE
-             /* Only allow invariants here, otherwise we may break
-                loop-closed SSA form.  */
-             && is_gimple_min_invariant (res))
-           init_cond = res;
-       }
-    }
+  /* We may not have fully constant propagated IL.  Handle degenerate PHIs here
+     to not miss important early loop unrollings.  */
+  init_cond = follow_copies_to_constant (init_cond);
 
   if (dump_file && (dump_flags & TDF_SCEV))
     {
@@ -1968,8 +1984,8 @@ analyze_scalar_evolution_1 (struct loop *loop, tree var, tree res)
   if (bb == NULL
       || !flow_bb_inside_loop_p (loop, bb))
     {
-      /* Keep the symbolic form.  */
-      res = var;
+      /* Keep symbolic form, but look through obvious copies for constants.  */
+      res = follow_copies_to_constant (var);
       goto set_and_end;
     }