Re: [Qemu-devel] [PATCH v5 45/76] target/mips: Implement emulation of nanoMIPS LLWP/SCWP pair

[Richard Henderson]

On 08/02/2018 08:29 AM, Aleksandar Markovic wrote:
> Hi, Richard,
> 
> We are going to remove obsoleted helpers, that was just an honest mistake 
> made in a rush.
> 
> For unprotected access to gpr, we are going to insert if(reg1 != 0) in two 
> places.

Be careful that you do not eliminate side effects in the process.  This
includes things like check_dspr2, and any helper that sets overflow_flag or
carry_flag.

I cannot see how you will avoid that when adding only two if statements.


> However, it looks there is a bigger problem now in SCWP. QEMU crashes with 
> this message:
> 
> /qemu/tcg/tcg.c:2862: tcg fatal error
> 
> This happens in user mode only, system mode case runs fine.
> 
> the problem seems to appear as a consequence of using tcg_gen_brcond_*(().
> 
> Do you have any idea what are we doing wrong here?

If you send me a binary that triggers this error, I'll look at it.


r~