VOIDmode in ZERO_EXTEND crashed

[daniel tian <daniel dot xntian at gmail dot com>]

hi, everyone:
     I have ported the gcc to new RISC chip. But when I build the
newlib with it, the gcc crashed in simplify-rtx.c.
     error message is like this:

     ../../../../../newlib-1.16.0/newlib/libc/time/tzset_r.c: In
function _tzset_r?
     ../../../../../newlib-1.16.0/newlib/libc/time/tzset_r.c:195:
internal compiler error: in simplify_const_unary_operation, at
simplify-rtx.c:1108

     And the code there is simplify-rtx.c 1108:

     case ZERO_EXTEND:
	  /* When zero-extending a CONST_INT, we need to know its
             original mode.  */
	  gcc_assert (op_mode != VOIDmode);

     I tracked the gcc, It caused by the RTX   (const_int 60). As I
know the CONST_INT is alway being VOIDmode.
     I dumped the rtl tzset_r.c.161r.dce, and I think it caused by the
following rtx(because the there is const_int 60 in this rtx and the
register used is exactly what I saw in rtx which causes the gcc
crash):

      (insn 229 228 230 21
../../../../../newlib-1.16.0/newlib/libc/time/tzset_r.c:78 (set
(reg:SI 181)
        (mult:SI (zero_extend:SI (reg:HI 182 [ mm ]))
            (zero_extend:SI (const_int 60 [0x3c])))) 63
{rice_umulhisi3} (expr_list:REG_DEAD (reg:HI 182 [ mm ])
        (nil)))

    And the problem is I don't know why it lead crashing.
    PS: Does gcc have a function which could dump the specified rtx? I
wanna dump the rtx when the crash happening.

    Can somebody give me some advice?
    Any suggestion is appreciated.

    Thanks.

                  daniel.