Re: [Qemu-devel] [PATCH] tcg: optimize gen_extr_i64_i32()

[Philippe Mathieu-Daudé]

On 05/12/2017 11:13 PM, Richard Henderson wrote:
> On 05/12/2017 05:29 PM, Philippe Mathieu-Daudé wrote:
> > Inspired by Richard Henderson comment:
> >
> >
> > http://lists.nongnu.org/archive/html/qemu-devel/2017-05/msg02277.html
> >
> > Patch applied mechanically with this coccinelle semantic patch:
> >
> >      @@
> >      expression lo, hi,arg;
> >      @@
> >      -tcg_gen_extrl_i64_i32(lo, arg);
> >      -tcg_gen_extrh_i64_i32(hi, arg);
> >      +tcg_gen_extr_i64_i32(lo, hi, arg);
> >
> > Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> > ---
> >   tcg/tcg-op.c | 3 +--
> >   1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/tcg/tcg-op.c b/tcg/tcg-op.c
> > index 6b1f41500c..f3d556c21a 100644
> > --- a/tcg/tcg-op.c
> > +++ b/tcg/tcg-op.c
> > @@ -2562,8 +2562,7 @@ void tcg_gen_extr_i64_i32(TCGv_i32 lo, TCGv_i32
> > hi, TCGv_i64 arg)
> >           tcg_gen_mov_i32(lo, TCGV_LOW(arg));
> >           tcg_gen_mov_i32(hi, TCGV_HIGH(arg));
> >       } else {
> > -        tcg_gen_extrl_i64_i32(lo, arg);
> > -        tcg_gen_extrh_i64_i32(hi, arg);
> > +        tcg_gen_extr_i64_i32(lo, hi, arg);
>
> You've just created an instance of infinite self-recursion.

Now I understand why Eric writes "applied mechanically" then "verified 
manually" in his commits, it avoid to ask for non-sens review...