[patch] Fix PR rtl-optimization/89588

[Eric Botcazou]

Hi,

this is the failure of the assertion:

  /* Should not get here (such loop should be peeled instead).  */
  gcc_assert (niter > max_unroll + 1);

in unroll_loop_constant_iterations on a testcase both containing #pragma GCC 
unroll and compiled with -fno-tree-loop-optimize.  The proposed fix is just to 
disable the pragma altogether when the option is passed.

Tested on x86_64-suse-linux, OK for mainline and 8 branch?


2019-03-11  Eric Botcazou  <ebotca...@adacore.com>

        PR rtl-optimization/89588
        * tree-cfg.c (replace_loop_annotate_in_block) <annot_expr_unroll_kind>:
        Skip annotation and warn if -fno-tree-loop-optimize is specified.


2019-03-11  Eric Botcazou  <ebotca...@adacore.com>

        * c-c++-common/unroll-6.c: New test.

-- 
Eric Botcazou
Index: tree-cfg.c
===================================================================
--- tree-cfg.c	(revision 269546)
+++ tree-cfg.c	(working copy)
@@ -280,9 +280,16 @@ replace_loop_annotate_in_block (basic_bl
 	  loop->safelen = INT_MAX;
 	  break;
 	case annot_expr_unroll_kind:
-	  loop->unroll
-	    = (unsigned short) tree_to_shwi (gimple_call_arg (stmt, 2));
-	  cfun->has_unroll = true;
+	  if (flag_tree_loop_optimize)
+	    {
+	      loop->unroll
+		= (unsigned short) tree_to_shwi (gimple_call_arg (stmt, 2));
+	      cfun->has_unroll = true;
+	    }
+	  else
+	    warning_at (gimple_location (stmt), 0,
+			"pragma GCC unroll disabled by "
+			"-fno-tree-loop-optimize");
 	  break;
 	case annot_expr_no_vector_kind:
 	  loop->dont_vectorize = true;

/* { dg-do compile } */
/* { dg-options "-O -fno-tree-loop-optimize" } */

void test (void)
{
  #pragma GCC unroll 2
  for (int nv = 0; nv <= 2; nv += 2) /* { dg-warning "GCC unroll disabled" } */
    {}
}