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Subject: Re: [Qemu-devel] [PATCH 3/4] target-ppc: implement xxbr[qdwh]
 instruction
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To: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>, qemu-ppc@nongnu.org, david@gibson.dropbear.id.au
Cc: qemu-devel@nongnu.org, benh@kernel.crashing.org

On 10/07/2016 01:57 PM, Nikunj A Dadhania wrote:
> +static void gen_xxbrq(DisasContext *ctx)
> +{
> +    TCGv_i64 xth = cpu_vsrh(xT(ctx->opcode));
> +    TCGv_i64 xtl = cpu_vsrl(xT(ctx->opcode));
> +    TCGv_i64 xbh = cpu_vsrh(xB(ctx->opcode));
> +    TCGv_i64 xbl = cpu_vsrl(xB(ctx->opcode));
> +
> +    if (unlikely(!ctx->vsx_enabled)) {
> +        gen_exception(ctx, POWERPC_EXCP_VSXU);
> +        return;
> +    }
> +    tcg_gen_bswap64_i64(xth, xbl);
> +    tcg_gen_bswap64_i64(xtl, xbh);
> +}

You need a temporary for the case of T==B.  You don't want to overwrite XBH 
with XTH before you consume the input.


r~