Re: [Qemu-devel] [PATCH 2/2] target-ppc: fix xscmpodp and xscmpudp decoding

[Aurelien Jarno <aurelien@aurel32.net>]

On 2015-09-22 12:26, Thomas Huth wrote:
> On 13/09/15 23:03, Aurelien Jarno wrote:
> > The xscmpodp and xscmpudp instructions only have the AX, BX bits in
> > there encoding, the lowest bit (usually TX) is marked as an invalid
> > bit. We therefore can't decode them with GEN_XX2FORM, which decodes
> > the two lowest bit.
> > 
> > Introduce a new form GEN_XX2FORM, which decodes AX and BX and mark
> > the lowest bit as invalid.
> > 
> > Cc: Tom Musta <tommusta@gmail.com>
> > Cc: Alexander Graf <agraf@suse.de>
> > Cc: qemu-stable@nongnu.org
> > Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
> > ---
> >  target-ppc/translate.c | 11 +++++++++--
> >  1 file changed, 9 insertions(+), 2 deletions(-)
> > 
> > diff --git a/target-ppc/translate.c b/target-ppc/translate.c
> > index 84c5cea..c0eed13 100644
> > --- a/target-ppc/translate.c
> > +++ b/target-ppc/translate.c
> > @@ -10670,6 +10670,13 @@ GEN_HANDLER2_E(name, #name, 0x3C, opc2 | 1, opc3, 0, PPC_NONE, fl2), \
> >  GEN_HANDLER2_E(name, #name, 0x3C, opc2 | 2, opc3, 0, PPC_NONE, fl2), \
> >  GEN_HANDLER2_E(name, #name, 0x3C, opc2 | 3, opc3, 0, PPC_NONE, fl2)
> >  
> > +#undef GEN_XX2IFORM
> > +#define GEN_XX2IFORM(name, opc2, opc3, fl2)                           \
> > +GEN_HANDLER2_E(name, #name, 0x3C, opc2 | 0, opc3, 1, PPC_NONE, fl2), \
> > +GEN_HANDLER2_E(name, #name, 0x3C, opc2 | 1, opc3, 1, PPC_NONE, fl2), \
> > +GEN_HANDLER2_E(name, #name, 0x3C, opc2 | 2, opc3, 1, PPC_NONE, fl2), \
> > +GEN_HANDLER2_E(name, #name, 0x3C, opc2 | 3, opc3, 1, PPC_NONE, fl2)
> > +
> >  #undef GEN_XX3_RC_FORM
> >  #define GEN_XX3_RC_FORM(name, opc2, opc3, fl2)                          \
> >  GEN_HANDLER2_E(name, #name, 0x3C, opc2 | 0x00, opc3 | 0x00, 0, PPC_NONE, fl2), \
> > @@ -10731,8 +10738,8 @@ GEN_XX3FORM(xsnmaddadp, 0x04, 0x14, PPC2_VSX),
> >  GEN_XX3FORM(xsnmaddmdp, 0x04, 0x15, PPC2_VSX),
> >  GEN_XX3FORM(xsnmsubadp, 0x04, 0x16, PPC2_VSX),
> >  GEN_XX3FORM(xsnmsubmdp, 0x04, 0x17, PPC2_VSX),
> > -GEN_XX2FORM(xscmpodp,  0x0C, 0x05, PPC2_VSX),
> > -GEN_XX2FORM(xscmpudp,  0x0C, 0x04, PPC2_VSX),
> > +GEN_XX2IFORM(xscmpodp,  0x0C, 0x05, PPC2_VSX),
> > +GEN_XX2IFORM(xscmpudp,  0x0C, 0x04, PPC2_VSX),
> 
> According to PowerISA 2.07, xscmpodp and xscmpudp are of type XX3, not
> of type XX2 ... so should this macro maybe rather be named XX3IFORM instead?

Indeed, I have chosen the name without actually realizing the manual
also give names. Then I do wonder if the lower bit is really decoded as
invalid, I wouldn't be surprised it is actually just ignored.

I'll try to do some tests on real hardware and come up with a fixup
patch.

Aurelien

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                 http://www.aurel32.net