live insns deleted by delete_trivially_dead_insns()

[Paolo Bonzini]

Eric Botcazou wrote:
>>    It isn't until the loop2_done dump that the problem shows up.
>> delete_trivially_dead_insns() is called. It calls dead_libcall_p() on insn
>> 62 and seeing both the REQ_EQUAL and the REG_RETVAL note and successfully
>> replacing reg 92 with const_int 0, determines that the while libcall
>> sequence 63-152-61-62 is dead and can be deleted, without ever checking
>> insns 63, 152 or 61 for liveness.
> 
> Because it's the semantics of libcall sequences.  My take is that the lower 
> subreg pass breaks it in this case.

Can you also check -fno-forward-propagate?

Paolo