Re: [GXemul-devel] Patch: don't crash on MIPS divide overflow

[Anders G. <ga...@gm...>]

>
> When emulating the MIPS DIV and DDIV instructions, check for divide
> overflow instead of performing the overflowing divide on the host and
> crashing the emulator.  This is needed to run recent versions of the
> NetBSD test suite on an emulated MIPS system.
>
> --- gxemul.old/work/gxemul-0.6.0.1/src/cpus/cpu_mips_instr.cc
>  2018-08-08 17:27:19.146417631 +0300
> +++ gxemul/work/gxemul-0.6.0.1/src/cpus/cpu_mips_instr.cc
>  2018-08-08 17:27:27.944250037 +0300
> @@ -1262,6 +1262,8 @@
>         int32_t res, rem;
>         if (b == 0)
>                 res = 0, rem = a;
> +       else if (a == (int32_t)0x80000000U && b == -1)
> +               res = 0, rem = 0;
>         else
>                 res = a / b, rem = a - b*res;
>         cpu->cd.mips.lo = (int32_t)res;
> @@ -1284,6 +1286,8 @@
>         int64_t res, rem;
>         if (b == 0)
>                 res = 0;
> +       else if (a == (int64_t)0x8000000000000000ULL && b == -1)
> +               res = 0;
>         else
>                 res = a / b;
>         rem = a - b*res;
>

Thanks Andreas. The fix is now in trunk. A snapshot can be found here for
testing: http://gavare.se/gxemul/news.html


Anders