Comme=
nt # 18
on bug 10692=
8
from Miroslav =C5=A0ustek
(In reply to Roland Scheidegger from comment #12)
> (In reply to ubizjak from comment #11)
> > The (effectively the same patch as yours) proposed patch would be:
> >=20
> > diff --git a/src/gallium/drivers/r600/sb/sb_expr.cpp
> > b/src/gallium/drivers/r600/sb/sb_expr.cpp
> > index 7a5d62c8e8..a609d1377f 100644
> > --- a/src/gallium/drivers/r600/sb/sb_expr.cpp
> > +++ b/src/gallium/drivers/r600/sb/sb_expr.cpp
> > @@ -714,6 +714,8 @@ bool expr_handler::fold_assoc=
(alu_node *n) {
> >=20=20
> > n->src.resize(2);
> > n->bc.set_op(ALU_OP2_ADD);
> > + fold_alu_op2(*n);
> > + return true;
> > }
> > } else if (last_arg >=3D 0) {
> > n->src[0] =3D a->src[last_arg];
> >=20
> > WDYT?
>=20
> I am not quite convinced it's ok to return true (in fold_alu_op3) if t=
he
> expression hasn't really been folded. You are quite right that just ab=
ove it
> looks similar, but all other places always return the return value of
> fold_alu_op2 when calling into it from fold_alu_op3.
> (Not saying it isn't correct, just saying I can't tell...)
I guess it is OK. There already is the same pattern in fold_mul_add where it
tries to fold:
> ADD x, MUL(y, z)
into:
> MULADD y, z, x
and when it succeeds, it does:
>
> fold_alu_op3(*n);
> return true;
That means that no matter if fold_alu_op3 folds the instruction any further,
fold_mul_add returns true because it converted ADD and MUL into MULADD.
In fold_alu_op2 where fold_mul_add is called, the return value is used in an
early return condition:
> if (n.bc.op =3D=3D ALU_OP2_ADD) {
> if (fold_mul_add(&n))
> return true;
> }
It seems OK to me to return true after calling fold_alu_op2 in fold_alu_op3=
as
a sign that the node should not be folded as op3 anymore.
Also, the return value of fold_alu_op* is thrown away anyway here:
> bool expr_handler::try_fold(value* v) {
> assert(!v->gvn_source);
>=20
> if (v->def)
Here expr_handler::try_fold(node* n) calls the fold_alu_op* methods:
> try_fold(v->def);
>=20
> if (v->gvn_source)
> return true;
>=20
> return false;
> }
I like the patch that ubizjak@=
gmail.com posted:
> diff --git a/src/gallium/drivers/r600/sb/sb_expr=
.cpp b/src/gallium/drivers/r600/sb/sb_expr.cpp
> index 1df78da660..8cbff6f577 100644
> --- a/src/gallium/drivers/r600/sb/sb_expr.cpp
> +++ b/src/gallium/drivers/r600/sb/sb_expr.cpp
> @@ -723,6 +723,8 @@ bool expr_handler::fold_assoc(alu_=
node *n) {
>=20=20
> n->src.resize(2);
> n->bc.set_op(ALU_OP2_ADD);
> + fold_alu_op2(n);
> + return true;
> }
> } else if (last_arg >=3D 0) {
> n->src[0] =3D a->src[last_arg];