Loop invariant code corrupting xstormy16 insn

[Nick Clifton <nickc at redhat dot com>]

Hi Zdenek, Hi Daniel, Hi Geoff,

  I think that I have found a small bug in the loop invariant code.
  The problem is exhibited when building newlib for the xstormy16-elf
  toolchain although it may happen with other targets as well.  The
  problem occurs when an insn contains an r-value use of a register
  that is going to hoisted as well as a clobber of that register, like
  this:

    (parallel [
              (set (pc)
                   (if_then_else (lt:SI (reg:SI 45)    <---
                                        (reg:SI 26))
                                 (label_ref:HI 129)
                                 (pc)))
              (clobber (reg:SI 45))                    <-- must be the same
              (clobber (scratch:BI))
              ])

  The important point here is that the register referenced in the
  first clobber must match the register used as the first argument of
  the condition operation.  (This comes from the "ineqbranchsi"
  pattern in the xstormy16 machine description).

  The problem is that the loop-invariant optimization was deciding
  that (reg:SI 45) could be hoisted out of the loop, whereas really it
  should be left alone.  I have been looking at the loop invariant
  code trying to figure out what needs to be changed, but so far I
  have not been able to puzzle it out.

  I think that the real problem might be the clobbers in the
  ineqbranchsi pattern, but I do not know how it could be changed to
  fix this.

  Any ideas ?

Cheers
  Nick