gcc 3.3.1 segmentation fault (in rtlanal.c, rtx_varies_p())

[Grigory Tolstolytkin]

When compiling attached source file, the compiler crashes with 
segmentation fault in rtx_varies_p() function in rtlanal.c
I reproduced it at least for two tragets: arm_v5t_le and arm_iwmmxt_le. 
It doesn't occur when compiling with -O0 or -O1,
but for others do.

I debugged the compiler and found that the compiler generates the 
following rtl instruction:

(insn 16 15 17 0 0x4021b344 (set (reg/f:SI 71)
        (reg:SI 0 r0)) 345 {*iwmmxt_movsi_insn} (nil)
        (insn_list:REG_RETVAL 15 (expr_list:REG_EQUAL (expr_list 
(symbol_ref:SI ("cl"))
        (nil))
        (nil))))

Then, the "expr_list (symbol_ref:SI("cl"))" comes to the hash table for 
CSE optimization (the hash table declared in cse.c)

And when CSE optimization is applied
(cse_insn() is called on the rtl instruction
    (insn 28 47 36 1 0x4021b318 (set (mem/f:SI (plus:SI (reg/f:SI 25 sfp)
    (const_int -4 [0xfffffffc])) [2 S4 A32])
    (reg/v/f:SI 68)) 345 {*iwmmxt_movsi_insn} (nil)
    (nil))
) the rtl expression from the hash table is extracted and rtx_varies_p() 
function is called on each parameter of expr_list.
But the second parameter is NIL and rtx_varies_p() crashes on the first 
line (code = GET_CODE(x)), since the x is NULL.

If I add the follwing code in the beginning of rtx_varies_p():
"
    if (x == NULL)
        return 0;    // nil expression doesn't have have a value which 
can vary even between two executions of the program
"
then the compiler successfully generates object file. I wrote a simple 
test which calls the code from that object file and everything seems to 
work fine.

But I suppose that my fix might be wrong since I don't clearly 
understand how the compiler should work. In fact, does anybody know 
whether it's possible that such expressions may occur in the hash table 
or not?

Compilation parameters:
'arm_v5t_le-gcc -Os -c test.c -o test.o'

Any help is appreciated.
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