Re: [Qemu-devel] [PATCH 4/8] target-i386: Re-introduce optimal breakpoint removal

[Paolo Bonzini]

On 15/09/2015 20:45, Richard Henderson wrote:
> +        /* Fold the global and local enable bits together into the
> +           global fields, then xor to show which registers have
> +           changed collective enable state.  */
> +        int mod = ((old_dr7 | old_dr7 * 2) ^ (new_dr7 | new_dr7 * 2)) & 0xff;

The AND is not needed at all but, if you add it, you might as well use
"& 0xaa" which is clearer.  But even better, just do:

   target_ulong old_dr7 = env->dr[7];
   int mod = old_dr7 ^ new_dr7;
   ...
   if ((mod & ~0xff) == 0) {


and test with

        if (mod & (3 << i * 2))

inside the loop.

Otherwise looks good, I'll write a kvm-unit-tests patch for this.

Paolo