On 12/15/20 8:01 PM, frank.ch...@sifive.com wrote:
> +static bool gen_shifti(DisasContext *ctx, arg_shift *a,
> + void(*func)(TCGv, TCGv, TCGv))
> +{
> + TCGv source1 = tcg_temp_new();
> + TCGv source2 = tcg_temp_new();
> +
> + gen_get_gpr(source1, a->rs1);
> + tcg_gen_movi_tl(source2, a->shamt);
> +
> + tcg_gen_andi_tl(source2, source2, TARGET_LONG_BITS - 1);
Don't make the tcg optimizer do what it's easy to do in C, e.g.
tcg_gen_movi_tl(source2, a->shamt & (TARGET_LONG_BITS - 1));
Except in this case, I believe that shamt *cannot* be out of range, because
that would be an illegal instruction. E.g. in trans_srli, we check for that
first.
In the previous review I had recommended that you convert the existing
immediate shift instructions to this new interface, which should have shown
this problem.
> +static bool gen_shiftiw(DisasContext *ctx, arg_shift *a,
> + void(*func)(TCGv, TCGv, TCGv))
> +{
> + TCGv source1 = tcg_temp_new();
> + TCGv source2 = tcg_temp_new();
> +
> + gen_get_gpr(source1, a->rs1);
> + tcg_gen_movi_tl(source2, a->shamt);
> +
> + tcg_gen_andi_tl(source2, source2, 31);
This mask is unnecesary because the decode already uses @sh5.
r~
