Re: [Qemu-devel] [PATCH 16/20] target/arm: Make CCR register banked for v8M

[Richard Henderson]

On 08/22/2017 08:08 AM, Peter Maydell wrote:
> +        if (attrs.secure) {
> +            /* the BFHFNMIGN bit is not banked; keep that in the NS copy */
> +            int new_bfhnmign = !!(value & R_V7M_CCR_BFHFNMIGN_MASK);
> +
> +            cpu->env.v7m.ccr[M_REG_NS] = 
> deposit32(cpu->env.v7m.ccr[M_REG_NS],
> +                                                    
> R_V7M_CCR_BFHFNMIGN_SHIFT,
> +                                                    
> R_V7M_CCR_BFHFNMIGN_LENGTH,
> +                                                    new_bfhnmign);
> +            value &= ~R_V7M_CCR_BFHFNMIGN_MASK;
> +        }

No need to extract and then redeposit, just use the mask.

    cpu->env.v7m.ccr[M_REG_NS] =
      (cpu->env.v7m.ccr[M_REG_NS] & ~R_V7M_CCR_BFHFNMIGN_MASK)
      | (value & R_V7M_CCR_BFHFNMIGN_MASK);


r~