Fix a bug of peephole optimization

```
  if   L1
L0:
  jump L2
L1:
  ...
L2:
```

was wrongly optimized to:

```
  unless L2
L0:
L1:
  ...
L2:
```

To make it conservative, this optimization is now disabled when there is
any label between `if` and `jump` instructions.
Fixes [Bug #14897].

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63868 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 2 insertions, 1 deletions

diff --git a/compile.c b/compile.c
index ea6b74d18d..139a778471 100644
--- a/compile.c
+++ b/compile.c
@@ -2730,7 +2730,8 @@ iseq_peephole_optimize(rb_iseq_t *iseq, LINK_ELEMENT *list, const int do_tailcal
 	    ELEM_INSERT_NEXT(&dniobj->link, &pop->link);
 	    goto again;
 	}
-	else if ((piobj = (INSN *)get_prev_insn(iobj)) != 0 &&
+	else if (IS_INSN(iobj->link.prev) &&
+                 (piobj = (INSN *)iobj->link.prev) &&
 		 (IS_INSN_ID(piobj, branchif) ||
 		  IS_INSN_ID(piobj, branchunless))) {
 	    INSN *pdiobj = (INSN *)get_destination_insn(piobj);