[patch] invariant expressions in loop at depth zero

[Sebastian Pop]

> This doesn't look right.  It won't work for loop 0 then.  Why does
> flow_bb_inside_loop_p return true for your case?  This seems to be
> the place to fix it.

I'm calling expr_invariant_in_loop_p (loop_0, N) and N is defined in
bb_2 in loop0, so flow_bb_inside_loop_p (loop_0, bb_2) is returning true.

>  why are you calling expr_invariant_in_loop_p for loop_0?
>

I could fix the problem in the caller, but I still don't understand
why expr_invariant_in_loop_p should not be called with loop_0.

Could I document and add an assert in expr_invariant_in_loop_p for
this case?

Index: tree-scalar-evolution.c
===================================================================
--- tree-scalar-evolution.c	(revision 132763)
+++ tree-scalar-evolution.c	(working copy)
@@ -1971,6 +1971,7 @@ instantiate_parameters_1 (struct loop *l
       /* A parameter (or loop invariant and we do not want to include
 	 evolutions in outer loops), nothing to do.  */
       if (!def_bb
+	  || loop_depth (def_bb->loop_father) == 0
 	  || (!(flags & INSERT_SUPERLOOP_CHRECS)
 	      && !flow_bb_inside_loop_p (loop, def_bb)))
 	return chrec;
Index: tree-chrec.c
===================================================================
--- tree-chrec.c	(revision 132763)
+++ tree-chrec.c	(working copy)
@@ -948,8 +948,9 @@ evolution_function_is_invariant_rec_p (t
   if (evolution_function_is_constant_p (chrec))
     return true;

-  if (TREE_CODE (chrec) == SSA_NAME
-      && expr_invariant_in_loop_p (get_loop (loopnum), chrec))
+  if (TREE_CODE (chrec) == SSA_NAME
+      && (loopnum == 0
+	  || expr_invariant_in_loop_p (get_loop (loopnum), chrec)))
     return true;

   if (TREE_CODE (chrec) == POLYNOMIAL_CHREC)
Index: tree-ssa-loop-ivopts.c
===================================================================
--- tree-ssa-loop-ivopts.c	(revision 132763)
+++ tree-ssa-loop-ivopts.c	(working copy)
@@ -1254,7 +1254,8 @@ find_interesting_uses_cond (struct ivopt
 }

 /* Returns true if expression EXPR is obviously invariant in LOOP,
-   i.e. if all its operands are defined outside of the LOOP.  */
+   i.e. if all its operands are defined outside of the LOOP.  LOOP
+   should not be the function body.  */

 bool
 expr_invariant_in_loop_p (struct loop *loop, tree expr)
@@ -1262,6 +1263,8 @@ expr_invariant_in_loop_p (struct loop *l
   basic_block def_bb;
   unsigned i, len;

+  gcc_assert (loop_depth (loop) > 0);
+
   if (is_gimple_min_invariant (expr))
     return true;