Re: [Qemu-devel] [PATCH] tcg/mips: Bugfix for crash when runningprogram with qemu-i386.

[jiang.biao2]

>>       if (TCG_TARGET_REG_BITS > TARGET_LONG_BITS) {



>>           tcg_out_ext32u(s, base, addr_regl)
>> -        addr_regl = base
>> +        tcg_out_mov(s, TCG_TYPE_PTR, addr_regl, base)
>>       }
>>       if (guest_base == 0 && data_regl != addr_regl) {
>>           base = addr_regl
> 
> This is wrong, because you're not allowed to modify the input operands.
> 
> Try this, just a few lines lower in the function:

> -        tcg_out_movi(s, TCG_TYPE_PTR, base, guest_base)
> -        tcg_out_opc_reg(s, ALIAS_PADD, base, base, addr_regl)
> +        tcg_out_movi(s, TCG_TYPE_PTR, TCG_TMP0, guest_base)
> +        tcg_out_opc_reg(s, ALIAS_PADD, base, TCG_TMP0, addr_regl)
>

Got it, but the real problem is for addr_regl instead of guest_base.


Using your code for reference, I'll use TCG_TMP0 for addr_regl instead 


of modifying it, and then send patch of new version later.





>


> and you'll need the same change within tcg_out_qemu_st.
I'll write a test demo to produce crash in tcg_out_qemu_st flow, and send

another patch for that.





> Better would be to reserve a register for the guest_base, like we do for ppc. 
> See all of the uses of TCG_GUEST_BASE_REG in tcg/ppc/tcg-target.inc.c.
It uses base(TCG_REG_A0) for temperary use for guest_base in this case.




Thanks a lot.