[Bug target/59968] New: Unused BT patterns

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59968

            Bug ID: 59968
           Summary: Unused BT patterns
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hjl.tools at gmail dot com
            Target: x86/x86-64

There are some BT patterns in i386 guarded with
TARGET_USE_BT.  But there are no testcases to show
if they are used at all.

Also BT instructions supports memory destination.
But BT patterns only allow register destination.