[04/05] Fix PR 69032

[Andrey Belevantsev <abel at ispras dot ru>]

Hello,

We fail to find the proper seqno for the fresh bookkeeping copy in this PR. 
 The problem is that in get_seqno_by_preds we are iterating over bb from 
the given insn backwards up to the first bb insn.  We skip the initial insn 
when iterating over bb, yet we should take seqno from it.

The code in question originally didn't include bb head when iterating, and 
was patched to do so in 2011.  The patch was wrong and instead of including 
bb head managed to exclude the original insn itself.  By reading the 
original and patched code I've convinced myself that the right fix will be 
to do what the patch intended and include both the initial insn and the bb 
head in the iteration.

Ok for trunk?

gcc/

2016-03-14  Andrey Belevantsev  <abel@ispras.ru>

    PR rtl-optimization/69032
    * sel-sched-ir.c (get_seqno_by_preds): Include both tmp and head when 
looping backwards over basic block insns.

testsuite/

2016-03-14  Andrey Belevantsev  <abel@ispras.ru>

    PR rtl-optimization/69032
    * gcc.dg/pr69032.c: New test.

Best,
Andrey

diff --git a/gcc/sel-sched-ir.c b/gcc/sel-sched-ir.c
index ec59280..c1a9e55 100644
--- a/gcc/sel-sched-ir.c
+++ b/gcc/sel-sched-ir.c
@@ -4103,11 +4103,14 @@ get_seqno_by_preds (rtx_insn *insn)
   insn_t *preds;
   int n, i, seqno;
 
-  while (tmp != head)
+  /* Loop backwards from insn to head including both.  */
+  while (1)
     {
-      tmp = PREV_INSN (tmp);
       if (INSN_P (tmp))
         return INSN_SEQNO (tmp);
+      if (tmp == head)
+	break;
+      tmp = PREV_INSN (tmp);
     }
 
   cfg_preds (bb, &preds, &n);
diff --git a/gcc/testsuite/gcc.dg/pr69032.c b/gcc/testsuite/gcc.dg/pr69032.c
new file mode 100644
index 0000000..e0925cd
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr69032.c
@@ -0,0 +1,11 @@
+/* { dg-do compile { target powerpc*-*-* ia64-*-* i?86-*-* x86_64-*-* } } */
+/* { dg-options "-O2 -fsched-pressure -fsel-sched-pipelining -fselective-scheduling" } */
+
+void foo (long long i)
+{
+   while (i != -1)
+     {
+	++i;
+	 __asm__ ("");
+     }
+}