Initial shrink-wrapping patch

[Bernd Schmidt]

HJ found some more maybe_record_trace_start failures. In one case I
debugged, we have

(insn/f 31 0 32 (parallel [
            (set (reg/f:DI 7 sp)
                (plus:DI (reg/f:DI 7 sp)
                    (const_int 8 [0x8])))
            (clobber (reg:CC 17 flags))
            (clobber (mem:BLK (scratch) [0 A8]))
        ]) -1
     (expr_list:REG_CFA_ADJUST_CFA (set (reg/f:DI 7 sp)
            (plus:DI (reg/f:DI 7 sp)
                (const_int 8 [0x8])))
        (nil)))

The insn pattern is later changed by csa to adjust by 24, and the note
is left untouched; that seems to be triggering the problem.

Richard, is there a reason to use REG_CFA_ADJUST_CFA rather than
REG_CFA_DEF_CFA? If no, I'll just try to fix i386.c not to emit the former.


Bernd