inserting insns just before final

[aksammy@xxxxxxxxxxxx]

Hi, 

I'm trying to insert some special instructions into insn chain just before 
final where the asm code is generated. I invoke this pass just before
final is invoked from toplev.c My target is xscale-elf and I have modified 
arm.md to include the decription of the new instruction. 

At this point I'm simply doing a extract_insn on the insn which I pass
from toplev. I assume insn in toplev points to the start of the insn chain 
for the function. I get the following seg fault in libgcc2. 

[snip]
../../gcc-3.4.1/gcc/libgcc2.c: In function `__muldi3':
../../gcc-3.4.1/gcc/libgcc2.c:470: internal compiler error: Segmentation 
fault
Please submit a full bug report,
with preprocessed source if appropriate.
[snip] 

What am I doing wrong? 

Thanks in advance,
-Arvind 

PS: Please point me to some resources regarding insertion of special 
instructions in gcc, if such a thing exists. Thanks.