On 10/2/22 07:52, BitFriends wrote:
my bad, then I was mislead by "Which is, in general, what you want for implementing a
custom instruction". Also the code around me is full of gen instructions, so I thought
that's what I should use.
So, when reading the doc I found out about the cpu_{ld,st}*_mmu functions. That sounds
more what I want for a direct action, No?
That all depends on where you're putting the code. Based on what you've written so far,
I'd guess the answer is still no. But you haven't been overly verbose about what you're
trying to do.
r~
Regards
BitFriends
Richard Henderson <richard.hender...@linaro.org <mailto:richard.hender...@linaro.org>>
schrieb am So., 2. Okt. 2022, 16:40:
On 10/2/22 02:20, BitFriends wrote:
> I now came up with this code:
>
> TCGv_i64 res = 0;
> TCGv_i64 addr = (TCGv_i64)(env->regs[R_EDI]);
>
> tcg_gen_qemu_ld_i64(res, addr, 0, MO_LEUQ);
>
> env->regs[R_EAX] = (target_ulong)res;
>
> However this crashes afterwards in test_bit. Maybe this is caused by an
invalid
access?
> Anything wrong about the code? This still gives some warnings, like
TCGv_i32
expected (and
> when you use TCGv_i32, it says TCGv_i64 expected) plus some casting
warnings.
It is as if you did not read the second paragraph of my response at all.
tcg_gen_qemu_ld_i64 is for generating code, not performing a direct action.
Can you see how your code differs from *all* of the code around it?
r~
>
> Am Sa., 1. Okt. 2022 um 22:23 Uhr schrieb Richard Henderson
<richard.hender...@linaro.org <mailto:richard.hender...@linaro.org>
> <mailto:richard.hender...@linaro.org
<mailto:richard.hender...@linaro.org>>>:
>
> On 10/1/22 13:10, BitFriends wrote:
> > Hello,
> >
> > I am trying to create a custom instruction that accesses guest
memory
specified by an
> > address in a register. I specifically want to read from that
address. So I
tried to do
> > that using "tcg_gen_qemu_ld_i64(&res, env->regs[R_EDI], 0,
MO_LEUQ);", but that
> doesn't
> > save any result in res.
>
> This statement should have given you compilation errors, so I don't
know what
you mean by
> "doesn't save any result". There's clearly a disconnect between
what you
describe and
> what you actually attempted.
>
> Anyway, by the name you can see that function "gen"erates a "tcg"
operation,
which is
> then
> later compiled by the jit, the output of which is later executed to
produce a
result.
> Which is, in general, what you want for implementing a custom
instruction.
>
>
> r~
>
