[Mesa-dev] [PATCH] nv50/ir: Split 64-bit MAD and MUL operations

[Pierre Moreau]

On 06:05 PM - Mar 19 2016, Ilia Mirkin wrote:
> Not 100% sure, but pretty sure this is wrong. Can you provide the
> generated sequence of instructions in response to a 64-bit mul and
> mad?

For the given mul:

  mov u64 %r42d 0x0000000000000004
  mov u64 %r52d 0x0000000000000002
  mul u64 %r55d %r42d %r52d

the following is generated:

   mov u32 $r0 0x00000004
   mov u32 $r1 0x00000000
   mov u32 $r2 0x00000002
   mov u32 $r3 0x00000000
   mul u32 { $r0 $c0 } $r0 $r2
   mul (SUBOP:1) u32 $r1 $r1 $r3 $c0


Whereas for the mad, I need to first find how to tell Nouveau to stop splitting
each of my mads to mul + add…

> 
> On Sat, Mar 19, 2016 at 5:56 PM, Pierre Moreau <pierre.morrow at free.fr> wrote:
> > Two 32-bit MAD or MUL operations are generated in place of the original 64-bit
> > operation. All operands can either be signed or unsigned, but they have to be
> > integers.
> >
> > Signed-off-by: Pierre Moreau <pierre.morrow at free.fr>
> > ---
> >  src/gallium/drivers/nouveau/codegen/nv50_ir_build_util.cpp | 11 ++++++++++-
> >  1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_build_util.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_build_util.cpp
> > index 84ebfdb..0b37fcf 100644
> > --- a/src/gallium/drivers/nouveau/codegen/nv50_ir_build_util.cpp
> > +++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_build_util.cpp
> > @@ -586,6 +586,12 @@ BuildUtil::split64BitOpPostRA(Function *fn, Instruction *i,
> >        srcNr = 2;
> >        break;
> >     case OP_SELP: srcNr = 3; break;
> > +   case OP_MAD: /* fallthrough */
> > +   case OP_MUL:
> > +      if (!carry || isFloatType(i->dType) || isFloatType(i->sType))
> > +         return NULL;
> > +      srcNr = (i->op == OP_MAD) ? 3 : 2;
> > +      break;
> >     default:
> >        // TODO when needed
> >        return NULL;
> > @@ -600,6 +606,9 @@ BuildUtil::split64BitOpPostRA(Function *fn, Instruction *i,
> >
> >     hi->getDef(0)->reg.data.id++;
> >
> > +   if (i->op == OP_MAD || i->op == OP_MUL)
> > +      hi->subOp = NV50_IR_SUBOP_MUL_HIGH;
> > +
> >     for (int s = 0; s < srcNr; ++s) {
> >        if (lo->getSrc(s)->reg.size < 8) {
> >           if (s == 2)
> > @@ -629,7 +638,7 @@ BuildUtil::split64BitOpPostRA(Function *fn, Instruction *i,
> >           }
> >        }
> >     }
> > -   if (srcNr == 2) {
> > +   if (srcNr >= 2) {
> >        lo->setFlagsDef(1, carry);
> >        hi->setFlagsSrc(hi->srcCount(), carry);
> >     }
> > --
> > 2.7.4
> >
> > _______________________________________________
> > mesa-dev mailing list
> > mesa-dev at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/mesa-dev
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