[Bug tree-optimization/50213] [4.6/4.7 Regression] Regression in space-optimized code relative to 4.5.x

["rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50213

--- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-09-07 08:59:01 UTC ---
With

Index: gcc/tree-ssa-forwprop.c
===================================================================
--- gcc/tree-ssa-forwprop.c     (revision 178628)
+++ gcc/tree-ssa-forwprop.c     (working copy)
@@ -34,6 +34,7 @@ along with GCC; see the file COPYING3.
 #include "flags.h"
 #include "gimple.h"
 #include "expr.h"
+#include "cfgloop.h"

 /* This pass propagates the RHS of assignment statements into use
    sites of the LHS of the assignment.  It's basically a specialized
@@ -1069,10 +1070,11 @@ forward_propagate_addr_expr (tree name,
          continue;
        }

-      /* If the use is in a deeper loop nest, then we do not want
-        to propagate non-invariant ADDR_EXPRs into the loop as that
-        is likely adding expression evaluations into the loop.  */
-      if (gimple_bb (use_stmt)->loop_depth > stmt_loop_depth
+      /* If the use is in a different loop nest, then we do not want
+        to propagate non-invariant ADDR_EXPRs into or out of the loop
+        as that is likely adding expression evaluations into the loop
+        or extends register lifetimes across loop boundaries.  */
+      if (gimple_bb (use_stmt)->loop_depth != stmt_loop_depth
          && !is_gimple_min_invariant (rhs))
        {
          all = false;
@@ -2322,6 +2324,13 @@ ssa_forward_propagate_and_combine (void)
 {
   basic_block bb;
   unsigned int todoflags = 0;
+  bool cleanup_loops = false;
+
+  if (!current_loops)
+    {
+      loop_optimizer_init (LOOPS_NORMAL);
+      cleanup_loops = true;
+    }

   cfg_changed = false;

@@ -2517,6 +2526,9 @@ ssa_forward_propagate_and_combine (void)
        }
     }

+  if (cleanup_loops)
+    loop_optimizer_finalize ();
+
   if (cfg_changed)
     todoflags |= TODO_cleanup_cfg;


This is fixed.  Of course computing loops all over the place is ... not
the cheapest thing.

I'll see if we can easily avoid some of them.