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Sender: Richard Henderson <rth7680@gmail.com>
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Date: Fri, 06 Dec 2013 11:39:15 +1300
From: Richard Henderson <rth@twiddle.net>
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Subject: Re: [Qemu-devel] [PATCH 02/13] target-arm: A64: add support for
 logical (shifted register)
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To: Peter Maydell <peter.maydell@linaro.org>, qemu-devel@nongnu.org
Cc: patches@linaro.org, Michael Matz <matz@suse.de>, Claudio Fontana <claudio.fontana@linaro.org>, Dirk Mueller <dmueller@suse.de>, Will Newton <will.newton@linaro.org>, Laurent Desnogues <laurent.desnogues@gmail.com>, =?ISO-8859-1?Q?Alex_Benn=E9e?= <alex.bennee@linaro.org>, kvmarm@lists.cs.columbia.edu, Christoffer Dall <christoffer.dall@linaro.org>

On 12/06/2013 10:51 AM, Peter Maydell wrote:
> +    if (invert) {
> +        tcg_gen_not_i64(tcg_rm, tcg_rm);
> +    }
> +
> +    tcg_rd = cpu_reg(s, rd);
> +    tcg_rn = cpu_reg(s, rn);
> +
> +    switch (opc) {
> +    case 0: /* AND, BIC */
> +    case 3: /* ANDS, BICS */
> +        tcg_gen_and_i64(tcg_rd, tcg_rn, tcg_rm);
> +        break;
> +    case 1: /* ORR, ORN */
> +        tcg_gen_or_i64(tcg_rd, tcg_rn, tcg_rm);
> +        break;
> +    case 2: /* EOR, EON */
> +        tcg_gen_xor_i64(tcg_rd, tcg_rn, tcg_rm);
> +        break;
> +    default:
> +        assert(FALSE);
> +        break;
> +    }

While correct, surely better to work with tcg and select on opc:invert to
generate andc/orc/eqv?

Also, isn't MOV (register) canonical for ORR (rn=31 && shift_amount=0), and MVN
(register) canonical for ORN (rn=31 && shift_amount=0), and both therefore also
worth a special case?


r~