Re: [PATCH v5] riscv: Add support for the Zfa extension

[Richard Henderson]

On 6/30/23 13:52, Christoph Muellner wrote:
> +bool trans_fmvp_d_x(DisasContext *ctx, arg_fmvp_d_x *a)
> +{
> +    REQUIRE_FPU;
> +    REQUIRE_ZFA(ctx);
> +    REQUIRE_EXT(ctx, RVD);
> +    REQUIRE_32BIT(ctx);
> +
> +    TCGv src1 = get_gpr(ctx, a->rs1, EXT_ZERO);
> +    TCGv src2 = get_gpr(ctx, a->rs2, EXT_ZERO);
> +    TCGv_i64 t1 = tcg_temp_new_i64();
> +    TCGv_i64 t2 = tcg_temp_new_i64();
> +
> +    tcg_gen_ext_tl_i64(t1, src1);
> +    tcg_gen_ext_tl_i64(t2, src2);
> +    tcg_gen_shli_i64(t2, t2, 32);
> +    tcg_gen_or_i64(t2, t2, t1);
> +    tcg_gen_mov_i64(cpu_fpr[a->rd], t2);

This isn't right, because tcg_gen_ext_tl_i64 does signed extension.

But this whole operation is

    tcg_gen_concat_tl_i64(cpu_fpr[a->rd], src1, src2);

(which isn't a great name, but chosen long ago).

You can also use EXT_NONE, since we'll be discarding the upper bits.


r~