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.
Obviously more is required for multiplication and division, and you'd also have
to change cpu_so to examine the MSB as well.
r~
