[PATCH] Fix predcom ICE introduced by var clobber changes (PR tree-optimization/51246, take 2)

[Jakub Jelinek]

On Thu, Nov 24, 2011 at 05:28:00PM +0100, Michael Matz wrote:
> As the default defs are already automatically handled by all our ssa 
> infrastructure (including warning and propagation machinery) I think it 
> would be best to generate such one instead of a clobber for the RHS.

So like this?

2011-11-24  Jakub Jelinek  <ja...@redhat.com>

        PR tree-optimization/51246
        * tree-predcom.c (replace_ref_with): Handle also clobber on the
        rhs.

        * gcc.c-torture/compile/pr51246.c: New test.

--- gcc/tree-predcom.c.jj       2011-09-26 14:07:06.000000000 +0200
+++ gcc/tree-predcom.c  2011-11-24 17:39:08.196727939 +0100
@@ -1306,8 +1306,20 @@ replace_ref_with (gimple stmt, tree new_
       val = gimple_assign_lhs (stmt);
       if (TREE_CODE (val) != SSA_NAME)
        {
-         gcc_assert (gimple_assign_copy_p (stmt));
          val = gimple_assign_rhs1 (stmt);
+         gcc_assert (gimple_assign_single_p (stmt));
+         if (TREE_CLOBBER_P (val))
+           {
+             val = gimple_default_def (cfun, SSA_NAME_VAR (new_tree));
+             if (val == NULL_TREE)
+               {
+                 val = make_ssa_name (SSA_NAME_VAR (new_tree),
+                                      gimple_build_nop ());
+                 set_default_def (SSA_NAME_VAR (new_tree), val);
+               }
+           }
+         else
+           gcc_assert (gimple_assign_copy_p (stmt));
        }
     }
   else
--- gcc/testsuite/gcc.c-torture/compile/pr51246.c.jj    2011-11-24 
09:15:10.322906812 +0100
+++ gcc/testsuite/gcc.c-torture/compile/pr51246.c       2011-11-24 
09:14:52.000000000 +0100
@@ -0,0 +1,14 @@
+/* PR tree-optimization/51246 */
+
+int a, *b;
+
+void
+test (void)
+{
+  while (1)
+    {
+      int c;
+      a = c;
+      b = &c;
+    }
+}

        Jakub