On Thu, 2017-03-23 at 08:59 +0100, Samuel Iglesias Gonsálvez wrote:
> On Wed, 2017-03-22 at 15:47 -0700, Francisco Jerez wrote:
> > Samuel Iglesias Gonsálvez <sigles...@igalia.com> writes:
> >
> > > Generalize it to lower any unsupported narrower conversion.
> > >
> > > v2 (Curro):
> > > - Add supports_type_conversion()
> > > - Reuse existing intruction instead of cloning it.
> > > - Generalize d2x to narrower and equal size conversions.
> > >
> > > Signed-off-by: Samuel Iglesias Gonsálvez <sigles...@igalia.com>
> > > ---
> > > src/intel/compiler/brw_fs.cpp | 11 ++--
> > > src/intel/compiler/brw_fs_lower_d2x.cpp | 97
> > > ++++++++++++++++++++++++---------
> > > 2 files changed, 77 insertions(+), 31 deletions(-)
> > >
> > > diff --git a/src/intel/compiler/brw_fs.cpp
> > > b/src/intel/compiler/brw_fs.cpp
> > > index 6da23b17107..8612a83805d 100644
> > > --- a/src/intel/compiler/brw_fs.cpp
> > > +++ b/src/intel/compiler/brw_fs.cpp
> > > @@ -5694,11 +5694,6 @@ fs_visitor::optimize()
> > > OPT(dead_code_eliminate);
> > > }
> > >
> > > - if (OPT(lower_d2x)) {
> > > - OPT(opt_copy_propagation);
> > > - OPT(dead_code_eliminate);
> > > - }
> > > -
> > > OPT(lower_simd_width);
> > >
> > > /* After SIMD lowering just in case we had to unroll the EOT
> > > send. */
> > > @@ -5745,6 +5740,12 @@ fs_visitor::optimize()
> > > OPT(dead_code_eliminate);
> > > }
> > >
> > > + if (OPT(lower_d2x)) {
> > > + OPT(opt_copy_propagation);
> > > + OPT(dead_code_eliminate);
> > > + OPT(lower_simd_width);
> > > + }
> > > +
> > > lower_uniform_pull_constant_loads();
> > >
> > > validate();
> > > diff --git a/src/intel/compiler/brw_fs_lower_d2x.cpp
> > > b/src/intel/compiler/brw_fs_lower_d2x.cpp
> > > index a2db1154615..fa25d313dcd 100644
> > > --- a/src/intel/compiler/brw_fs_lower_d2x.cpp
> > > +++ b/src/intel/compiler/brw_fs_lower_d2x.cpp
> > > @@ -27,47 +27,92 @@
> > >
> > > using namespace brw;
> > >
> > > +static bool
> > > +supports_type_conversion(fs_inst *inst) {
> >
> > Pointer should be marked const.
> >
> > > + switch(inst->opcode) {
> > > + case BRW_OPCODE_MOV:
> > > + case SHADER_OPCODE_MOV_INDIRECT:
> > > + return true;
> > > + case BRW_OPCODE_SEL:
> > > + return false;
> >
> > I suggest you return 'inst->dst.type == get_exec_type_size(inst)'
> > here
> > in order to simplify the logic below and restructure things in a
> > way
> > that allows you to make opcode-specific decisions here based on the
> > actual execution and destination types.
>
> I guess you meant:
> 'type_sz(inst->dst.type) == get_exec_type_size(inst)'
>
> This would make it simpler but we then allow f2d conversion which is
Sorry, I meant f2i conversion.
Sam
> not allowed for SEL.
>
> >
> > > + default:
> > > + /* FIXME: We assume the opcodes don't explicitly mentioned
> > > + * before just work fine with arbitrary conversions.
> > > + */
> > > + return true;
> > > + }
> > > +}
> > > +
> > > bool
> > > fs_visitor::lower_d2x()
> > > {
> > > bool progress = false;
> > >
> > > foreach_block_and_inst_safe(block, fs_inst, inst, cfg) {
> > > - if (inst->opcode != BRW_OPCODE_MOV)
> > > - continue;
> > > + bool inst_support_conversion =
> > > supports_type_conversion(inst);
> > > + bool supported_conversion =
> > > + inst_support_conversion &&
> > > + (get_exec_type_size(inst) != 8 ||
> > > + type_sz(inst->dst.type) > 4 ||
> > > + type_sz(inst->dst.type) >= get_exec_type_size(inst));
> > >
> > > - if (inst->dst.type != BRW_REGISTER_TYPE_F &&
> > > - inst->dst.type != BRW_REGISTER_TYPE_D &&
> > > - inst->dst.type != BRW_REGISTER_TYPE_UD)
> > > + /* If the conversion is supported or there is no
> > > conversion
> > > then
> > > + * do nothing.
> > > + */
> > > + if (supported_conversion ||
> > > + (!inst_support_conversion && inst->dst.type == inst-
> > > > src[0].type) ||
> >
> > You should be using the execution type here (and below where you
> > allocate the temp0 and temp1 vgrfs) instead of assuming it matches
> > the
> > type of the first source. Also I'm not 100% certain that the
> > combination of this conditional continue, the one below, the
> > if/else
> > branches below and the supported_conversion definitions above catch
> > the
> > exact set of cases where you need to apply lowering. This would be
> > a
> > lot easier to follow (most of the above goes away) if you did
> > something
> > along the lines of:
> >
>
> OK, thanks.
>
> > > if (supports_type_conversion(inst)) {
> > > if (get_exec_type_size(inst) == 8 && type_sz(inst->dst.type) <
> > > 8) {
> > > // Apply strided move workaround...
> > > progress = true;
> > > }
> > > } else {
> > > // Apply general conversion workaround...
> > > progress = true;
> > > }
> > > + inst->dst.file == BAD_FILE || inst->src[0].file ==
> > > BAD_FILE)
> >
> > I don't think the 'inst->dst.file == BAD_FILE || inst->src[0].file
> > ==
> > BAD_FILE' terms of this expression are correct or useful, the
> > 'inst->src[0].file' term because there might be a destination
> > region
> > conversion regardless of what the file of the first source is, the
> > 'inst->dst.file == BAD_FILE' term because you could just rely on
> > DCE
> > instead...
> >
>
> OK
>
> > > continue;
> > >
> > > - if (inst->src[0].type != BRW_REGISTER_TYPE_DF &&
> > > - inst->src[0].type != BRW_REGISTER_TYPE_UQ &&
> > > - inst->src[0].type != BRW_REGISTER_TYPE_Q)
> > > - continue;
> > > + /* This pass only supports conversion to narrower or equal
> > > size types. */
> > > + if (get_exec_type_size(inst) < type_sz(inst->dst.type))
> > > + continue;
> > >
> >
> > I think you need to apply this condition to the if branch below
> > that
> > deals with DF to F conversions *only*, the else branch you probably
> > need
> > to apply regardless of whether the destination type is larger or
> > smaller
> > than the execution type.
> >
>
> OK
>
> > > - assert(inst->dst.file == VGRF);
> > > assert(inst->saturate == false);
> >
> > I don't see why it's safe to rely on saturate being false here, in
> > any
> > case it would be straightforward to handle it by setting the flag
> > on
> > the
> > emitted MOV instruction and clearing it on the original
> > instruction.
> >
>
> OK
>
> > > - fs_reg dst = inst->dst;
> > >
> > > const fs_builder ibld(this, block, inst);
> > > + fs_reg dst = inst->dst;
> > >
> > > - /* From the Broadwell PRM, 3D Media GPGPU, "Double
> > > Precision
> > > Float to
> > > - * Single Precision Float":
> > > - *
> > > - * The upper Dword of every Qword will be written with
> > > undefined
> > > - * value when converting DF to F.
> > > - *
> > > - * So we need to allocate a temporary that's two
> > > registers,
> > > and then do
> > > - * a strided MOV to get the lower DWord of every Qword
> > > that
> > > has the
> > > - * result.
> > > - */
> > > - fs_reg temp = ibld.vgrf(inst->src[0].type, 1);
> > > - fs_reg strided_temp = subscript(temp, inst->dst.type, 0);
> > > - ibld.MOV(strided_temp, inst->src[0]);
> > > - ibld.MOV(dst, strided_temp);
> > > + if (inst_support_conversion && !supported_conversion) {
> > > + /* From the Broadwell PRM, 3D Media GPGPU, "Double
> > > Precision Float to
> > > + * Single Precision Float":
> > > + *
> > > + * The upper Dword of every Qword will be written
> > > with
> > > undefined
> > > + * value when converting DF to F.
> > > + *
> > > + * So we need to allocate a temporary that's two
> > > registers, and then do
> > > + * a strided MOV to get the lower DWord of every Qword
> > > that has the
> > > + * result.
> > > + */
> > > + fs_reg temp = ibld.vgrf(inst->src[0].type, 1);
> >
> > The '1' argument is redundant in all fs_builder::vgrf() calls here
> > and
> > below.
> >
>
> OK
>
> > > + fs_reg strided_temp = subscript(temp, dst.type, 0);
> > > +
> > > + /* We clone the original instruction as we are going to
> > > modify it
> > > + * and emit another one after it.
> > > + */
> >
> > Comment seems stale.
> >
>
> Right.
>
> > > + inst->dst = strided_temp;
> > > + /* As it is an strided destination, we write n-times
> > > more
> > > being n the
> > > + * size difference between source and destination
> > > types.
> > > Update
> >
> > I guess by difference you meant ratio here and in the copy-pasted
> > comment below (the comments also have a few minor spelling mistakes
> > but
> > that's unlikely to cause as much confusion).
> >
>
> Right.
>
> > > + * size_written with the new destination.
> > > + */
> > > + inst->size_written = inst->dst.component_size(inst-
> > > > exec_size);
> >
> > I think I'd add an assert(inst->size_written ==
> > inst->dst.component_size(inst->exec_size)) right before you assign
> > 'inst->dst' to point at the temporary in order to make sure you
> > aren't
> > accidentally miscompiling instructions that write multiple
> > components.
> >
>
> OK
>
> > > + ibld.at(block, inst->next).MOV(dst, strided_temp);
> > > + } else {
> > > + fs_reg temp0 = ibld.vgrf(inst->src[0].type, 1);
> > > + fs_reg temp1 = ibld.vgrf(inst->src[0].type, 1);
> > > + fs_reg strided_temp1 = subscript(temp1, dst.type, 0);
> > > +
> > > + inst->dst = temp0;
> > > + /* As it is an strided destination, we write n-times
> > > more
> > > being n the
> > > + * size difference between source and destination
> > > types.
> > > Update
> > > + * size_written with the new destination.
> > > + */
> > > + inst->size_written = inst->dst.component_size(inst-
> > > > exec_size);
> > >
> > >
> > > - inst->remove(block);
> > > + /* Now, do the conversion to original destination's
> > > type.
> > > */
> > > + fs_inst *mov = ibld.at(block, inst-
> > > > next).MOV(strided_temp1, temp0);
> > >
> > > + ibld.at(block, mov->next).MOV(dst, strided_temp1);
> >
> > Isn't this MOV and the strided_temp1 handling redundant? I'd
> > expect
> > it
> > to be handled automatically during the next loop iteration of this
> > pass
> > (though you may have to switch back to foreach_block_and_inst()
> > instead
> > of foreach_block_and_inst_safe()), which would also result in
> > better
> > code because the extra move would only be emitted if this is an
> > actual
> > DF->F conversion.
> >
>
> Good catch!
>
> Thanks for all the suggestions, I am going to do them.
>
> Sam
>
> > > + }
> > > progress = true;
> > > }
> > >
> > > --
> > > 2.11.0
> > >
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>
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