pa reload problem

[John David Anglin]

>         b,l foo,%r2
>         copy %r27,%r4
>         addil LT'cpu_hz,%r4	! know r27 trashed in call, so use r4
>         ldd RT'cpu_hz(%r1),%r1
>         ldd -144(%r30),%r2
>         ldw 0(%r1),%r19
>         addil LT'L$C0000,%r27	! oops, should be using r4
>         ldd RT'L$C0000(%r1),%r1

It looks to me like this happens because the register life analysis in
pass 13 decides that r27 (dp) is dead.  This causes combine to delete the
insn that restores r27 after the call to foo and use the value saved
in r4 as a proxy for dp.

(insn 16 14 21 (set (reg:DI 27 %r27)
        (reg:DI 4 %r4)) 123 {movstrsi_internal+11} (nil)
    (expr_list:REG_DEAD (reg:DI 4 %r4)
	(nil)))

(insn 21 16 23 (set (reg:DI 68)
	(plus:DI (reg:DI 27 %r27)
	    (high:DI (symbol_ref:DI ("cpu_hz"))))) 81 {post_std+3} (insn_list 16 (nil))
     (expr_list:REG_DEAD (reg:DI 27 %r27)
	(nil)))

The const_int's which follow haven't been expanded at this point.  Thus,
the life analysis can't tell that r27 is still needed.

Dave
-- 
J. David Anglin                                  dave.anglin@nrc.ca
National Research Council of Canada              (613) 990-0752 (FAX: 952-6605)