re PR middle-end/27136 (Compile failure with -O -ffast-math)

2006-05-07  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/27136
	* tree-ssa-loop-niter.c (get_val_for): Correct function
	comment, assert requirements.
	(loop_niter_by_eval): Stop processing if the iterated
	value did not simplify.

	* gcc.dg/torture/pr27136.c: New testcase.

From-SVN: r113601

1 files changed, 8 insertions, 2 deletions

diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c
index bc359ad..a3c5791 100644
--- a/gcc/tree-ssa-loop-niter.c
+++ b/gcc/tree-ssa-loop-niter.c
@@ -1301,7 +1301,7 @@ get_base_for (struct loop *loop, tree x)
 
 /* Given an expression X, then 
  
-   * if BASE is NULL_TREE, X must be a constant and we return X.
+   * if X is NULL_TREE, we return the constant BASE.
    * otherwise X is a SSA name, whose value in the considered loop is derived
      by a chain of operations with constant from a result of a phi node in
      the header of the loop.  Then we return value of X when the value of the
@@ -1314,6 +1314,8 @@ get_val_for (tree x, tree base)
   use_operand_p op;
   ssa_op_iter iter;
 
+  gcc_assert (is_gimple_min_invariant (base));
+
   if (!x)
     return base;
 
@@ -1414,7 +1416,11 @@ loop_niter_by_eval (struct loop *loop, edge exit)
 	}
 
       for (j = 0; j < 2; j++)
-	val[j] = get_val_for (next[j], val[j]);
+	{
+	  val[j] = get_val_for (next[j], val[j]);
+	  if (!is_gimple_min_invariant (val[j]))
+	    return chrec_dont_know;
+	}
     }
 
   return chrec_dont_know;