[PATCH] Fix ICE in lambda-code (regression from 4.1.1, PR tree-optimization/29290)

[Jakub Jelinek <jakub at redhat dot com>]

Hi!

linear_transform_loops checks that none of the inner loops have multiple
exits, but doesn't check whether loop_nest itself has multiple exits.
Before the mid August change
http://gcc.gnu.org/viewcvs?view=rev&revision=116223
there was no ICE, all that happened when loop_nest->single_exit == NULL
is that gcc_loopnest_to_lambda_loopnest called gcc_loop_to_lambda_loop
and that immediately failed:
  /* Find out induction var and exit condition.  */
  inductionvar = find_induction_var_from_exit_cond (loop);
  exit_cond = get_loop_exit_condition (loop);

  if (inductionvar == NULL || exit_cond == NULL)
    {
      if (dump_file && (dump_flags & TDF_DETAILS))
        fprintf (dump_file,
                 "Unable to convert loop: Cannot determine exit condition or induction variable for loop.\n");
      return NULL;
    }
because a loop with multiple exits has exit_cond == NULL. 
gcc_loop_to_lambda_loop failure leeds to gcc_loopnest_to_lambda_loopnest
faiure and so linear_transform_loops did nothing for this loop.
But after the 116223 checkin, gcc_loopnest_to_lambda_loopnest
first calls:
  bool perfect_nest = perfect_nest_p (loop_nest);

  if (!perfect_nest && !can_convert_to_perfect_nest (loop_nest))
    goto fail;
and can_convert_to_perfect_nest relies on loop_nest->single_exit != NULL,
so we ICE in there.  As from the above I'm very sure we wouldn't do
anything meaningful with multiple exit loops anyway, I think it is better
to jump ship early then robustify various places in lambda-code.c.
The exact testcase doesn't ICE on the trunk, apparently because earlier
optimizations resulted in different loop set at the start of
-ftree-loop-linear pass, but I don't see what would prevent such an ICE
if ever a multiple exit loop is passed to it and gets through the
tree-loop-linear.c conditions up to gcc_loopnest_to_lambda_loopnest.

Ok for trunk/4.1?

2006-10-05  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/23625
	* tree-loop-linear.c (linear_transform_loops): Bail if loop_nest has
	multiple exits.

	* gfortran.dg/pr29290.f90: New test.

--- gcc/tree-loop-linear.c.jj	2006-10-05 11:51:35.000000000 +0200
+++ gcc/tree-loop-linear.c	2006-10-05 11:53:34.000000000 +0200
@@ -267,12 +267,12 @@ linear_transform_loops (struct loops *lo
                {
 	        ...
                }
-           for (j = 0; j < 50; j++)
+             for (j = 0; j < 50; j++)
                {
                 ...
                }
            } */
-      if (!loop_nest || !loop_nest->inner)
+      if (!loop_nest || !loop_nest->inner || !loop_nest->single_exit)
 	continue;
       VEC_truncate (tree, oldivs, 0);
       VEC_truncate (tree, invariants, 0);
--- gcc/testsuite/gfortran.dg/pr29290.f90.jj	2006-10-05 11:56:01.000000000 +0200
+++ gcc/testsuite/gfortran.dg/pr29290.f90	2006-10-05 11:59:01.000000000 +0200
@@ -0,0 +1,9 @@
+! PR tree-optimization/23625
+! { dg-do compile }
+! { dg-options "-O3 -ftree-loop-linear" }
+
+subroutine pr23625 (a, b, c, d)
+  integer c, d
+  real*8 a(c,c), b(c,c)
+  a(1:d,1:d) = b(1:d,1:d)
+end

	Jakub