Re: [Qemu-devel] [PATCH 3/4] tcg/aarch64: implement sign/zero extend operations

[Claudio Fontana]

On 31.05.2013 21:13, Richard Henderson wrote:
> On 05/31/2013 11:05 AM, Jani Kokkonen wrote:
>> +static inline void tcg_out_uxt(TCGContext *s, int s_bits,
>> +                               TCGReg rd, TCGReg rn)
>> +{
>> +    /* using ALIASes UXTB 0x53001c00, UXTH 0x53003c00
>> +       of UBFM Wd, Wn, #0, #7|15 and mov */
>> +    int bits = 8 * (1 << s_bits) - 1;
>> +    tcg_out_ubfm(s, 0, rd, rn, 0, bits);
>> +}
> 
> Err, ubfm never generates mov, does it?

No, the comment is a leftover, it's wrong.

> Yes, you do that later,
> 
>> +    case INDEX_op_ext32u_i64:
>> +        tcg_out_movr(s, 0, args[0], args[1]);
>> +        break;
> 
> but the comment isn't actually correct in tcg_out_uxt, surely?
> 

right.

I was think also about the

INDEX_op_ext16u_i64 and INDEX_op_ext16u_i32,
I think I can just use ext = 0 for both when doing the UXT,
consistently to what we discussed before about trying to use
ext=0 whenever possible.

CLaudio