Re: [Qemu-devel] [PATCH 5/8] tcg/optimize: Handle known-zeros masks for ANDC

[Aurelien Jarno]

On Fri, Jan 31, 2014 at 08:47:00AM -0600, Richard Henderson wrote:
> Signed-off-by: Richard Henderson <address@hidden>
> ---
>  tcg/optimize.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/tcg/optimize.c b/tcg/optimize.c
> index d3b099a..3291a08 100644
> --- a/tcg/optimize.c
> +++ b/tcg/optimize.c
> @@ -727,6 +727,17 @@ static TCGArg *tcg_constant_folding(TCGContext *s, 
> uint16_t *tcg_opc_ptr,
>              mask = temps[args[1]].mask & mask;
>              break;
>  
> +        CASE_OP_32_64(andc):
> +            /* Known-zeros does not imply known-ones.  Therefore unless
> +               args[2] is constant, we can't infer anything from it.  */
> +            if (temps[args[2]].state == TCG_TEMP_CONST) {
> +                mask = ~temps[args[2]].mask;
> +                goto and_const;
> +            }
> +            /* But we certainly know nothing outside args[1] may be set. */
> +            mask = temps[args[1]].mask;
> +            break;
> +
>          case INDEX_op_sar_i32:
>              if (temps[args[2]].state == TCG_TEMP_CONST) {
>                  mask = (int32_t)temps[args[1]].mask >> temps[args[2]].val;

Reviewed-by: Aurelien Jarno <address@hidden>

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
address@hidden                 http://www.aurel32.net