[PATCH] TLC to reassoc get_rank

[Richard Biener]

Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.

Richard.

2015-05-29  Richard Biener  <rguent...@suse.de>

        * tree-ssa-reassoc.c (get_rank): Simplify.

Index: gcc/tree-ssa-reassoc.c
===================================================================
--- gcc/tree-ssa-reassoc.c      (revision 223818)
+++ gcc/tree-ssa-reassoc.c      (working copy)
@@ -417,10 +417,6 @@ insert_operand_rank (tree e, long rank)
 static long
 get_rank (tree e)
 {
-  /* Constants have rank 0.  */
-  if (is_gimple_min_invariant (e))
-    return 0;
-
   /* SSA_NAME's have the rank of the expression they are the result
      of.
      For globals and uninitialized values, the rank is 0.
@@ -460,9 +456,9 @@ get_rank (tree e)
 
   if (TREE_CODE (e) == SSA_NAME)
     {
+      ssa_op_iter iter;
       gimple stmt;
       long rank;
-      int i, n;
       tree op;
 
       if (SSA_NAME_IS_DEFAULT_DEF (e))
@@ -472,8 +468,7 @@ get_rank (tree e)
       if (gimple_code (stmt) == GIMPLE_PHI)
        return phi_rank (stmt);
 
-      if (!is_gimple_assign (stmt)
-         || gimple_vdef (stmt))
+      if (!is_gimple_assign (stmt))
        return bb_rank[gimple_bb (stmt)->index];
 
       /* If we already have a rank for this expression, use that.  */
@@ -484,34 +479,12 @@ get_rank (tree e)
       /* Otherwise, find the maximum rank for the operands.  As an
         exception, remove the bias from loop-carried phis when propagating
         the rank so that dependent operations are not also biased.  */
+      /* Simply walk over all SSA uses - this takes advatage of the
+         fact that non-SSA operands are is_gimple_min_invariant and
+        thus have rank 0.  */
       rank = 0;
-      if (gimple_assign_single_p (stmt))
-       {
-         tree rhs = gimple_assign_rhs1 (stmt);
-         n = TREE_OPERAND_LENGTH (rhs);
-         if (n == 0)
-           rank = propagate_rank (rank, rhs);
-         else
-           {
-             for (i = 0; i < n; i++)
-               {
-                 op = TREE_OPERAND (rhs, i);
-
-                 if (op != NULL_TREE)
-                   rank = propagate_rank (rank, op);
-               }
-           }
-       }
-      else
-       {
-         n = gimple_num_ops (stmt);
-         for (i = 1; i < n; i++)
-           {
-             op = gimple_op (stmt, i);
-             gcc_assert (op);
-             rank = propagate_rank (rank, op);
-           }
-       }
+      FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_USE)
+       rank = propagate_rank (rank, op);
 
       if (dump_file && (dump_flags & TDF_DETAILS))
        {
@@ -525,7 +498,11 @@ get_rank (tree e)
       return (rank + 1);
     }
 
-  /* Globals, etc,  are rank 0 */
+  /* Constants have rank 0.  */
+  if (is_gimple_min_invariant (e))
+    return 0;
+
+  /* Constants, globals, etc., are rank 0 */
   return 0;
 }