middle-end: inspect all exits for additional annotations for loop.

Attaching a pragma to a loop which has a complex condition often gets the pragma
dropped. e.g.

#pragma GCC novector
  while (i < N && parse_tables_n--)

before lowering this is represented as:

 if (ANNOTATE_EXPR <i <= 305 && parse_tables_n--  != 0, no-vector>) ...

But after lowering the condition is broken appart and attached to the final
component of the expression:

  if (parse_tables_n.2_2 != 0) goto <D.4456>; else goto <D.4453>;
  <D.4456>:
    iftmp.1D.4452 = 1;
    goto <D.4454>;
  <D.4453>:
    iftmp.1D.4452 = 0;
  <D.4454>:
    D.4451 = .ANNOTATE (iftmp.1D.4452, 2, 0);
    if (D.4451 != 0) goto <D.4442>; else goto <D.4440>;
  <D.4440>:

and it's never heard from again because during replace_loop_annotate we only
inspect the loop header and latch for annotations.

Since annotations were supposed to apply to the loop as a whole this fixes it
by checking the loop exit src blocks for annotations instead.

gcc/ChangeLog:

	* tree-cfg.cc (replace_loop_annotate): Inspect loop edges for annotations.

gcc/testsuite/ChangeLog:

	* gcc.dg/vect/vect-novect_gcond.c: New test.

gcc/testsuite/gcc.dg/vect/vect-novect_gcond.c

@@ -0,0 +1,39 @@
+/* { dg-add-options vect_early_break } */
+/* { dg-require-effective-target vect_early_break_hw } */
+/* { dg-require-effective-target vect_int } */
+/* { dg-additional-options "-O3" } */
+
+/* { dg-final { scan-tree-dump-not "LOOP VECTORIZED" "vect" } } */
+
+#include "tree-vect.h"
+
+#define N 306
+#define NEEDLE 136
+
+int table[N];
+
+__attribute__ ((noipa))
+int foo (int i, unsigned short parse_tables_n)
+{
+  parse_tables_n >>= 9;
+  parse_tables_n += 11;
+#pragma GCC novector
+  while (i < N && parse_tables_n--)
+    table[i++] = 0;
+
+  return table[NEEDLE];
+}
+
+int main ()
+{
+  check_vect ();
+
+#pragma GCC novector
+  for (int j = 0; j < N; j++)
+    table[j] = -1;
+
+  if (foo (0, 0xFFFF) != 0)
+    __builtin_abort ();
+
+  return 0;
+}

gcc/tree-cfg.cc

@@ -320,12 +320,9 @@ replace_loop_annotate (void)
 
   for (auto loop : loops_list (cfun, 0))
     {
-      /* First look into the header.  */
-      replace_loop_annotate_in_block (loop->header, loop);
-
-      /* Then look into the latch, if any.  */
-      if (loop->latch)
-	replace_loop_annotate_in_block (loop->latch, loop);
+      /* Check all exit source blocks for annotations.  */
+      for (auto e : get_loop_exit_edges (loop))
+	replace_loop_annotate_in_block (e->src, loop);
 
       /* Push the global flag_finite_loops state down to individual loops.  */
       loop->finite_p = flag_finite_loops;