Re: [Qemu-devel] [PATCH v2 1/3] target-mips: Copy restrictions from ext/ins to dext/dins

[Aurelien Jarno <aurelien@aurel32.net>]

On 2015-08-03 14:41, Richard Henderson wrote:
> On 08/03/2015 02:31 PM, Aurelien Jarno wrote:
> >On 2015-08-03 12:35, Richard Henderson wrote:
> >>          if (msb != 31) {
> >>-            tcg_gen_andi_tl(t0, t0, (1 << (msb + 1)) - 1);
> >>+            tcg_gen_andi_tl(t0, t0, (1U << (msb + 1)) - 1);
> >
> >Is this change really needed?
> 
> msb == 30 means 1 << 31.  Which officially must be unsigned to be correct.
> If we were to run under ubsan, this would trigger an error.

Ok.

> >Note that DEXT can't fail as both lsb and msb are in the range 0..31.
> >DEXTU and DEXTM can.
> ...
> >The same way DINSM can't fail.
> 
> Yes, I know.  But it seems cleaner to do the checks always, unifying all of
> the code.

Agreed.

> >Should we try to get this one into 2.4, if not already too late?
> 
> Perhaps.  Otherwise via stable after the fact.

Ok. Leon, do you have other pending patches for 2.4/2.4.1? The
semihosting microMIPS R6 one maybe?

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                 http://www.aurel32.net