Fix PR 83530

[Andrey Belevantsev]

Hello,

This issue is when we cannot correctly make insn tick data for the
unscheduled code (but processed by the modulo scheduler).  Fixed by closely
following usual scheduling process as described in the PR.

Best,
Andrey

2018-04-03  Andrey Belevantsev  <a...@ispras.ru>

        PR rtl-optimization/83530

        * sel-sched.c (force_next_insn): New global variable.
        (remove_insn_for_debug): When force_next_insn is true, also leave only
next insn
        in the ready list.
        (sel_sched_region): When the region wasn't scheduled, make another pass
over it
        with force_next_insn set to 1.


        * gcc.dg/pr8350.c: New test.

diff --git a/gcc/sel-sched.c b/gcc/sel-sched.c
index 76092f9587a..fca2b69c5ee 100644
--- a/gcc/sel-sched.c
+++ b/gcc/sel-sched.c
@@ -5004,12 +5004,16 @@ remove_temp_moveop_nops (bool full_tidying)
    distinguishing between bookkeeping copies and original insns.  */
 static int max_uid_before_move_op = 0;

+/* When true, we're always scheduling next insn on the already scheduled code
+   to get the right insn data for the following bundling or other passes.  */
+static int force_next_insn = 0;
+
 /* Remove from AV_VLIW_P all instructions but next when debug counter
    tells us so.  Next instruction is fetched from BNDS.  */
 static void
 remove_insns_for_debug (blist_t bnds, av_set_t *av_vliw_p)
 {
-  if (! dbg_cnt (sel_sched_insn_cnt))
+  if (! dbg_cnt (sel_sched_insn_cnt) || force_next_insn)
     /* Leave only the next insn in av_vliw.  */
     {
       av_set_iterator av_it;
@@ -7642,7 +7646,13 @@ sel_sched_region (int rgn)
     sel_sched_region_1 ();
   else
     /* Force initialization of INSN_SCHED_CYCLEs for correct bundling.  */
-    reset_sched_cycles_p = true;
+    {
+      reset_sched_cycles_p = false;
+      pipelining_p = false;
+      force_next_insn = 1;
+      sel_sched_region_1 ();
+      force_next_insn = 0;
+    }

   sel_region_finish (reset_sched_cycles_p);
 }
diff --git a/gcc/testsuite/gcc.dg/pr83530.c b/gcc/testsuite/gcc.dg/pr83530.c
new file mode 100644
index 00000000000..f4d8927de92
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr83530.c
@@ -0,0 +1,15 @@
+/* { dg-do compile { target powerpc*-*-* ia64-*-* i?86-*-* x86_64-*-* } } */
+/* { dg-options "-O2 -fmodulo-sched -fselective-scheduling2" } */
+int vm, z0;
+short int mz;
+
+int
+ny (void)
+{
+  int ch;
+
+  for (ch = 0; ch < 6; ++ch)
+    vm += ch / vm;
+
+  return z0 + mz;
+}