Re: [Qemu-devel] TCG is hard to understand!

[Laurent Desnogues]

On Fri, Dec 11, 2009 at 4:18 AM, Jun Koi <address@hidden> wrote:
>
> Another question: I look at tcg_gen_callN() to see how the helper is
> executed. We put the helper opcode into the TCG code buffer, and put
> helper's params into gen_opparam_buf.
>
> However, then when TCG generates code to actually call the helper, we
> just put the opcode of the host insn into the output buffer, which is
> target code at this step, then run it.
>
> Now when the helper is executed, it must get its param from the stack,
> which is really the host stack. But as said above, its params are in
> gen_opparam_buf, but not in stack?
> I searched around, and dont see anywhere we link gen_opparam_buf with
> the host stack. So how the helper can get its param??
>
> Surely I missed something, or misunderstand the whole picture. Any hint?

Take a look at tcg.c:tcg_reg_alloc_call


Laurent