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Date: Mon, 3 Jun 2013 11:43:23 +0200
From: Claudio Fontana <claudio.fontana@huawei.com>
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Subject: Re: [Qemu-devel] [PATCH 1/4] tcg/aarch64: more low level ops in
 preparation of tlb, lookup
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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

On 31.05.2013 21:07, Richard Henderson wrote:
> On 05/31/2013 10:57 AM, Jani Kokkonen wrote:
>> +    ARITH_SUBS = 0x6b,
> 
> Any reason you're adding SUBS here, but not ANDS?

I also forgot ANDS, I'll add them and reorder.

>> +/* encode a logical immediate, mapping user parameter
>> +   M=set bits pattern length to S=M-1 */
>> +static inline unsigned int
>> +aarch64_limm(unsigned int m, unsigned int r)
>> +{
>> +    assert(m > 0);
>> +    return r << 16 | (m - 1) << 10;
>> +}
>> +
>> +/* test a register against an immediate bit pattern made of
>> +   M set bits rotated right by R.
>> +   Examples:
>> +   to test a 32/64 reg against 0x00000007, pass M = 3,  R = 0.
>> +   to test a 32/64 reg against 0x000000ff, pass M = 8,  R = 0.
>> +   to test a 32bit reg against 0xff000000, pass M = 8,  R = 8.
>> +   to test a 32bit reg against 0xff0000ff, pass M = 16, R = 8.
>> + */
>> +static inline void tcg_out_tst(TCGContext *s, int ext, TCGReg rn,
>> +                               unsigned int m, unsigned int r)
>> +{
>> +    /* using TST alias of ANDS XZR, Xn,#bimm64 0x7200001f */
>> +    unsigned int base = ext ? 0xf240001f : 0x7200001f;
>> +    tcg_out32(s, base | aarch64_limm(m, r) | rn << 5);
>> +}
>> +
>> +/* and a register with a bit pattern, similarly to TST, no flags change */
>> +static inline void tcg_out_andi(TCGContext *s, int ext, TCGReg rd, TCGReg rn,
>> +                                unsigned int m, unsigned int r)
>> +{
>> +    /* using AND 0x12000000 */
>> +    unsigned int base = ext ? 0x92400000 : 0x12000000;
>> +    tcg_out32(s, base | aarch64_limm(m, r) | rn << 5 | rd);
>> +}
>> +
> 
> This should be a separate patch, since it's not related to the tcg_out_arith
> change.
> 

Agreed.

Claudio