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From: Richard Henderson <rth@twiddle.net>
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Date: Wed, 12 Aug 2015 10:00:41 -0700
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Subject: Re: [Qemu-devel] [PATCH for-2.5 19/30] m68k: add cmpm
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To: Laurent Vivier <laurent@vivier.eu>, qemu-devel@nongnu.org
Cc: peter.maydell@linaro.org, Andreas Schwab <schwab@linux-m68k.org>, gerg@uclinux.org

On 08/09/2015 01:13 PM, Laurent Vivier wrote:
> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
> ---
>  target-m68k/translate.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/target-m68k/translate.c b/target-m68k/translate.c
> index ae57792..adf4521 100644
> --- a/target-m68k/translate.c
> +++ b/target-m68k/translate.c
> @@ -2002,6 +2002,24 @@ DISAS_INSN(eor)
>  
>      opsize = insn_opsize(insn, 6);
>  
> +    if (((insn >> 3) & 7) == 1) {
> +        /* cmpm */

Surely this can be separated out from EOR via masks at register_opcode time.
And since this isn't a coldfire instruction...

> +        reg = AREG(insn, 0);
> +        src = gen_load(s, opsize, reg, 1);
> +        tcg_gen_addi_i32(reg, reg, opsize_bytes(opsize));
> +
> +        reg = AREG(insn, 9);
> +        dest = gen_load(s, opsize, reg, 1);
> +        tcg_gen_addi_i32(reg, reg, opsize_bytes(opsize));
> +
> +        reg = tcg_temp_new();
> +        tcg_gen_sub_i32(reg, dest, src);
> +        gen_update_cc_add(reg, src);

No need for the extra temp, reg.  Simply modify dest.

> +        SET_CC_OP(opsize, SUB);
> +
> +        return;
> +    }
> +
>      SRC_EA(env, src, opsize, -1, &addr);
>      reg = DREG(insn, 9);
>      dest = tcg_temp_new();
>