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

From: Claudio Fontana <claudio.fontana@huawei.com>
To: Richard Henderson <rth@twiddle.net>
Cc: Laurent Desnogues <laurent.desnogues@gmail.com>,
	Peter Maydell <peter.maydell@linaro.org>,
	Jani Kokkonen <Jani.Kokkonen@huawei.com>,
	qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 3/4] tcg/aarch64: implement sign/zero extend operations
Date: Mon, 3 Jun 2013 11:48:23 +0200	[thread overview]
Message-ID: <51AC6667.5030008@huawei.com> (raw)
In-Reply-To: <51A8F670.1060601@twiddle.net>

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