Richard Henderson <r...@twiddle.net> writes:
> On 02/14/2017 02:05 PM, Nikunj A Dadhania wrote:
>> Yes, you are right. I had a discussion with Paul Mackerras yesterday, he
>> explained to me in detail about the bits. I am working on the revised
>> implementation. Will detail it in the commit message.
>
> As you're working on this, consider changing the definition of cpu_ov such
> that
> the MSB is OV and bit 31 is OV32.
>
> E.g.
>
>
> static inline void gen_op_arith_compute_ov(DisasContext *ctx, TCGv arg0,
> TCGv arg1, TCGv arg2, int sub)
> {
> TCGv t0 = tcg_temp_new();
>
> tcg_gen_xor_tl(cpu_ov, arg0, arg2);
> tcg_gen_xor_tl(t0, arg1, arg2);
> if (sub) {
> tcg_gen_and_tl(cpu_ov, cpu_ov, t0);
> } else {
> tcg_gen_andc_tl(cpu_ov, cpu_ov, t0);
> }
> tcg_temp_free(t0);
> if (NARROW_MODE(ctx)) {
> tcg_gen_ext32s_tl(cpu_ov, cpu_ov);
> }
> - tcg_gen_shri_tl(cpu_ov, cpu_ov, TARGET_LONG_BITS - 1);
> tcg_gen_or_tl(cpu_so, cpu_so, cpu_ov);
> }
>
>
> is all that is required for arithmetic to compute OV and OV32 into those two
> bits.
How about the below?
@@ -809,10 +809,11 @@ static inline void gen_op_arith_compute_ov(DisasContext
*ctx, TCGv arg0,
tcg_gen_andc_tl(cpu_ov, cpu_ov, t0);
}
tcg_temp_free(t0);
+ tcg_gen_extract_tl(cpu_ov32, cpu_ov, 31, 1);
+ tcg_gen_extract_tl(cpu_ov, cpu_ov, 63, 1);
if (NARROW_MODE(ctx)) {
- tcg_gen_ext32s_tl(cpu_ov, cpu_ov);
+ tcg_gen_mov_tl(cpu_ov, cpu_ov32);
}
- tcg_gen_shri_tl(cpu_ov, cpu_ov, TARGET_LONG_BITS - 1);
tcg_gen_or_tl(cpu_so, cpu_so, cpu_ov);
}
Regards
Nikunj
