Re: [PATCH v3 09/30] tcg/loongarch64: Implement tcg_out_mov and tcg_out_movi

[Richard Henderson]

On 9/22/21 11:09 AM, WANG Xuerui wrote:
> +    if (sextreg(val, 0, 52) == val) {
> +        /*
> +         * Fits in 52-bits, upper bits are already properly sign-extended by
> +         * cu32i.d.
> +         */
> +        return;
> +    }
> +    tcg_out_opc_cu52i_d(s, rd, rd, top);
> +}

Oh, future improvement: constants with 52 low zero bits can be loaded with cu52i(rd, zero, 
val >> 52).

Which means there's a set of interesting constants:

  abc0_0000_0000_0def

        ori     rd, zero, 0xdef
        cu52i   rd, rd, 0xabc

  abcf_ffff_ffff_fdef

        cu52i   rd, zero, 0xabc - 1
        addi.d  rd, rd, 0xdef

Also,

> +    tcg_out_opc_lu12i_w(s, rd, upper);
> +    if (low != 0) {
> +        tcg_out_opc_ori(s, rd, rd, low & 0xfff);
> +    }

when upper == 0 and low != 0, we can omit the lu12i.


r~