Re: [Qemu-devel] [PATCH] TCG: fix copy propagation

[Stefan Weil]

Am 06.08.2011 22:13, schrieb Stefan Weil:
> Am 06.08.2011 16:06, schrieb Blue Swirl:
> > Copy propagation introduced in 22613af4a6d9602001e6d0e7b6d98aa40aa018dc
> > considered only global registers. However, register temps and stack
> > allocated locals must be handled differently because register temps
> > don't survive across brcond.
> >
> > Fix by propagating only within same class of temps.
> >
> > Signed-off-by: Blue Swirl <address@hidden>
> > ---
> > tcg/optimize.c | 13 +++++++------
> > tcg/tcg.h | 5 +++++
> > 2 files changed, 12 insertions(+), 6 deletions(-)
> >
> > diff --git a/tcg/optimize.c b/tcg/optimize.c
> > index a3bfa5e..748ecf9 100644
> > --- a/tcg/optimize.c
> > +++ b/tcg/optimize.c
> > @@ -185,12 +185,13 @@ static int op_to_movi(int op)
> > }
> > }
> >
> > -static void tcg_opt_gen_mov(TCGArg *gen_args, TCGArg dst, TCGArg src,
> > - int nb_temps, int nb_globals)
> > +static void tcg_opt_gen_mov(TCGContext *s, TCGArg *gen_args, TCGArg 
> > dst,
> > + TCGArg src, int nb_temps, int nb_globals)
> > {
> > reset_temp(dst, nb_temps, nb_globals);
> > assert(temps[src].state != TCG_TEMP_COPY);
> > - if (src >= nb_globals) {
> > + if (src >= nb_globals &&
> > + tcg_arg_is_local(s, src) == tcg_arg_is_local(s, dst)) {
> > assert(temps[src].state != TCG_TEMP_CONST);
> [snip]
>
> Hi Blue,
>
> your patch fixes qemu-system-x86_64 which now seems to work on 32 bit 
> hosts, too.
>
> qemu-system-mips64(el) still fail with the same abort. They work when 
> I remove the
> if block in tcg_opt_gen_mov.
>
> The Debian kernel for qemu-system-mips64 which I used for the test is 
> available on
> http://qemu.weilnetz.de/mips64/.
>
> I could not reproduce the crash with qemu-system-ppc64 - neither with 
> nor without
> your patch.
>
> Kind regards,
> Stefan

The patch works with qemu-system-mips64(el) after a small modification:

if (src >= nb_globals &&
    tcg_arg_is_local(s, src) && tcg_arg_is_local(s, dst)) {

Cheers,
Stefan