PR c++/35325

[pf3gnuchains/gcc-fork.git] / gcc / tree-ssa-propagate.c

diff --git a/gcc/tree-ssa-propagate.c b/gcc/tree-ssa-propagate.c
index 4803362..c37cfa5 100644 (file)
--- a/gcc/tree-ssa-propagate.c
+++ b/gcc/tree-ssa-propagate.c
@@ -6,7 +6,7 @@
 
    GCC is free software; you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by the
-   Free Software Foundation; either version 2, or (at your option) any
+   Free Software Foundation; either version 3, or (at your option) any
    later version.
 
    GCC is distributed in the hope that it will be useful, but WITHOUT
@@ -15,9 +15,8 @@
    for more details.
 
    You should have received a copy of the GNU General Public License
-   along with GCC; see the file COPYING.  If not, write to the Free
-   Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
-   02110-1301, USA.  */
+   along with GCC; see the file COPYING3.  If not see
+   <http://www.gnu.org/licenses/>.  */
 
 #include "config.h"
 #include "system.h"
@@ -617,7 +616,7 @@ valid_gimple_expression_p (tree expr)
                  return false;
                t = TREE_OPERAND (t, 0);
              }
-           if (!is_gimple_addressable (t))
+           if (!is_gimple_id (t))
              return false;
            break;
          }
@@ -711,12 +710,9 @@ set_rhs (tree *stmt_p, tree expr)
     case GIMPLE_MODIFY_STMT:
       op = GIMPLE_STMT_OPERAND (stmt, 1);
       if (TREE_CODE (op) == WITH_SIZE_EXPR)
-       {
-         stmt = op;
-          TREE_OPERAND (stmt, 1) = expr;
-       }
+       TREE_OPERAND (op, 0) = expr;
       else
-        GIMPLE_STMT_OPERAND (stmt, 1) = expr;
+       GIMPLE_STMT_OPERAND (stmt, 1) = expr;
       break;
 
     case COND_EXPR:
@@ -752,6 +748,7 @@ set_rhs (tree *stmt_p, tree expr)
                SSA_NAME_DEF_STMT (var) = *stmt_p;
            }
        }
+      stmt->base.ann = NULL;
       break;
     }
 
@@ -1214,10 +1211,12 @@ substitute_and_fold (prop_value_t *prop_value, bool use_ranges_p)
        for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
          replace_phi_args_in (phi, prop_value);
 
-      for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
+      /* Propagate known values into stmts.  Do a backward walk to expose
+        more trivially deletable stmts.  */
+      for (i = bsi_last (bb); !bsi_end_p (i);)
        {
           bool replaced_address, did_replace;
-         tree prev_stmt = NULL;
+         tree call, prev_stmt = NULL;
          tree stmt = bsi_stmt (i);
 
          /* Ignore ASSERT_EXPRs.  They are used by VRP to generate
@@ -1225,7 +1224,33 @@ substitute_and_fold (prop_value_t *prop_value, bool use_ranges_p)
             afterwards.  */
          if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
              && TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == ASSERT_EXPR)
-           continue;
+           {
+             bsi_prev (&i);
+             continue;
+           }
+
+         /* No point propagating into a stmt whose result is not used,
+            but instead we might be able to remove a trivially dead stmt.  */
+         if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
+             && TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 0)) == SSA_NAME
+             && !stmt_ann (stmt)->has_volatile_ops
+             && has_zero_uses (GIMPLE_STMT_OPERAND (stmt, 0))
+             && !tree_could_throw_p (stmt)
+             && (!(call = get_call_expr_in (stmt))
+                 || !TREE_SIDE_EFFECTS (call)))
+           {
+             if (dump_file && dump_flags & TDF_DETAILS)
+               {
+                 fprintf (dump_file, "Removing dead stmt ");
+                 print_generic_expr (dump_file, stmt, 0);
+                 fprintf (dump_file, "\n");
+               }
+             bsi_remove (&i, true);
+             release_defs (stmt);
+             if (!bsi_end_p (i))
+               bsi_prev (&i);
+             continue;
+           }
 
          /* Record the state of the statement before replacements.  */
          push_stmt_changes (bsi_stmt_ptr (i));
@@ -1301,6 +1326,8 @@ substitute_and_fold (prop_value_t *prop_value, bool use_ranges_p)
             statement.  */
          if (use_ranges_p)
            simplify_stmt_using_ranges (stmt);
+
+         bsi_prev (&i);
        }
     }