Re: [Qemu-devel] Re: Compile files only once: some planning

[Paolo Bonzini]

On 03/24/2010 03:56 PM, Paul Brook wrote:
> > On 03/24/2010 12:19 PM, Richard Henderson wrote:
> > > On 03/24/2010 02:47 AM, Paolo Bonzini wrote:
> > > > 1) make CPUState define only common fields. Include CPUState at the
> > > > beginning of each per-target CPUXYZState.
> > >
> > > Irritatingly, the common fields contain quite big TLBs. And the
> > > offsets from the start of env affect the compactness of the code
> > > generated from TCG. We really really want the general registers
> > > to come first to make sure that those offsets fit the host's
> > > reg+offset addressing mode.
> >
> > What about adding a 512-bytes (or more) block or something like that at
> > the beginning of CPUState with a union, so you can put the per-target
> > stuff there?
>
> Is it really worth the hassle? Anything touching CPUState is probably going to
> be CPU specific anyway.

qemu-timer.c, hw/dma.c is not and these are the first two files I looked 
at.  translate-all.c is the third, and it is except for a trivial cleanup.

Big parts of vl.c are independent too.

As a quick check:

$ git grep -l 'CPUState' | grep -ve ^tcg -e ^target- | wc -l
96
$ git grep -l 'CPUState' | grep -ve ^tcg -e ^target- | \
     xargs grep -l '#if.*TARGET_' | wc -l
36

The ones that remain are pretty much what would you expect, besides 
translate-all.c and some in hw/ which I snipped:

bsd-user/main.c
darwin-user/main.c darwin-user/qemu.h darwin-user/signal.c
linux-user/elfload.c linux-user/main.c linux-user/qemu.h
linux-user/signal.c linux-user/syscall.c

cpu-all.h cpu-defs.h cpu-exec.c
def-helper.h
disas.c
exec-all.h exec.c
gdbstub.c
monitor.c
translate-all.c
vl.c

Of course this doesn't mean that 60 files are target-independent, but 
30-ish probably are or can be made so.

It would also help code clarity to use CPUXYZState more, to understand 
which hw/ files are specific to one model.  For hw/s390-virtio.c that's 
obvious, but slightly less so for hw/sun4m.c and even less so for 
hw/syborg.c.  This is an independent cleanup.

Paolo