[PATCH, pre-approved] Fix operand scan problems for PR49749

[William J. Schmidt]

This patch fixes part of PR tree-optimization/49749.  The operand scans
in tree-ssa-reassoc.c:get_rank() can be prematurely halted by two
erroneous conditions, which this patch removes.  Patch pre-approved by
IRC communication with Richard Guenther, 7/21/11.

The wider issue of biasing reassociation in favor of loop-carried
dependencies is still pending.

Bootstrapped and regression-tested on powerpc64-linux.  I'll commit it
shortly.


2011-07-21  Bill Schmidt  <wschm...@linux.vnet.ibm.com>

        PR tree-optimization/49749
        * tree-ssa-reassoc.c (get_rank): Fix operand scan conditions and
        remove no-longer-used maxrank variable.
        
Index: gcc/tree-ssa-reassoc.c
===================================================================
--- gcc/tree-ssa-reassoc.c      (revision 176569)
+++ gcc/tree-ssa-reassoc.c      (working copy)
@@ -235,7 +235,7 @@ get_rank (tree e)
   if (TREE_CODE (e) == SSA_NAME)
     {
       gimple stmt;
-      long rank, maxrank;
+      long rank;
       int i, n;
 
       if (TREE_CODE (SSA_NAME_VAR (e)) == PARM_DECL
@@ -258,7 +258,6 @@ get_rank (tree e)
       /* Otherwise, find the maximum rank for the operands, or the bb
         rank, whichever is less.   */
       rank = 0;
-      maxrank = bb_rank[gimple_bb(stmt)->index];
       if (gimple_assign_single_p (stmt))
        {
          tree rhs = gimple_assign_rhs1 (stmt);
@@ -267,15 +266,15 @@ get_rank (tree e)
            rank = MAX (rank, get_rank (rhs));
          else
            {
-             for (i = 0;
-                  i < n && TREE_OPERAND (rhs, i) && rank != maxrank; i++)
-               rank = MAX(rank, get_rank (TREE_OPERAND (rhs, i)));
+             for (i = 0; i < n; i++)
+               if (TREE_OPERAND (rhs, i))
+                 rank = MAX(rank, get_rank (TREE_OPERAND (rhs, i)));
            }
        }
       else
        {
          n = gimple_num_ops (stmt);
-         for (i = 1; i < n && rank != maxrank; i++)
+         for (i = 1; i < n; i++)
            {
              gcc_assert (gimple_op (stmt, i));
              rank = MAX(rank, get_rank (gimple_op (stmt, i)));