Re: [Qemu-devel] [PATCH 09/22] exec-all: shrink tb->invalid to uint8_t

[Richard Henderson]

On 07/10/2017 01:57 PM, Emilio G. Cota wrote:
> > What I would prefer to do is generalize tb->cflags.  Those values *do*
> > affect how we compile the TB, and yet we don't take them into account.  So I
> > think it would be a good idea to feed that into the TB hash.
>
> I'm having trouble seeing how this could work.
> Where do we get the "current" values from the current state, i.e.
> the ones we need to generate the hash and perform comparisons?
> In particular:
> - CF_COUNT_MASK: just use CF_COUNT_MASK?
> - CF_LAST_IO: ?
> - CF_NOCACHE: always 0 I guess

All of these are set by cpu_io_recompile as needed.
They are all clear for normal TBs.

> - CF_USE/IGNORE_ICOUNT: ?
CF_IGNORE_ICOUNT probably shouldn't exist.  Probably the callers of tb_gen_code 
should simply set CF_USE_ICOUNT properly if use_icount is true, rather than 
having two flags control the same feature.

At which point CF_USE_ICOUNT should be set iff use_icount is true.

Likewise CF_PARALLEL would be set iff parallel_cpus is true, except for within 
cpu_exec_step_atomic where we would always use 0 (because that's the whole 
point of that function).


r~