PR tree-optimization/89713 - Assume loop with an exit is finite

gcc/ChangeLog:

        * doc/invoke.texi (-ffinite-loops): Document new option.
        * common.opt (-ffinite-loops): New option.
        * tree-ssa-dce.c (mark_stmt_if_obviously_necessary): Mark
        IFN_GOACC_LOOP calls as necessary.
        * tree-ssa-loop-niter.c (finite_loop_p): Assume loop with an exit
        is finite.
        * omp-offload.c (oacc_xform_loop): Skip lowering if return value of
        IFN_GOACC_LOOP call is not used.
        * opts.c (default_options_table): Enable -ffinite-loops at -O2+.

gcc/testsuite/ChangeLog:

        * g++.dg/tree-ssa/empty-loop.C: New test.
        * gcc.dg/tree-ssa/dce-2.c: New test.
        * gcc.dg/const-1.c: Add -fno-finite-loops option.
        * gcc.dg/graphite/graphite.exp: Likewise.
        * gcc.dg/loop-unswitch-1.c: Likewise.
        * gcc.dg/predict-9.c: Likewise.
        * gcc.dg/pure-2.c: Likewise.
        * gcc.dg/tree-ssa/20040211-1.c: Likewise.
        * gcc.dg/tree-ssa/loop-10.c: Likewise.
        * gcc.dg/tree-ssa/split-path-6.c: Likewise.
        * gcc.dg/tree-ssa/ssa-thread-12.c: Likewise.

libgomp/ChangeLog:

        * testsuite/libgomp.oacc-c-c++-common/pr84955-1.c: New test.

From-SVN: r272234

1 files changed, 21 insertions, 0 deletions

diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c
index 84e6e31..f513859 100644
--- a/gcc/tree-ssa-loop-niter.c
+++ b/gcc/tree-ssa-loop-niter.c
@@ -2830,6 +2830,27 @@ finite_loop_p (struct loop *loop)
 		 loop->num);
       return true;
     }
+
+  if (flag_finite_loops)
+    {
+      unsigned i;
+      vec<edge> exits = get_loop_exit_edges (loop);
+      edge ex;
+
+      /* If the loop has a normal exit, we can assume it will terminate.  */
+      FOR_EACH_VEC_ELT (exits, i, ex)
+	if (!(ex->flags & (EDGE_EH | EDGE_ABNORMAL | EDGE_FAKE)))
+	  {
+	    exits.release ();
+	    if (dump_file)
+	      fprintf (dump_file, "Assume loop %i to be finite: it has an exit "
+		       "and -ffinite-loops is on.\n", loop->num);
+	    return true;
+	  }
+
+      exits.release ();
+    }
+
   return false;
 }