On 04/28/2016 01:40 PM, Antia Puentes wrote:
> From: Alejandro Piñeiro <apinhe...@igalia.com>
>
> The HW has a restriction that only vertical stride may cross register
> boundaries. Until now this was only handled on VGRFs at
> rw_reg_from_fs_reg, but it is also needed for attributes.
>
> This can be seen as the equivalent of commit 552cfa9 but for
> attributes. Take a look to the git message on that commit for further
> info.
> ---
> src/mesa/drivers/dri/i965/brw_fs.cpp | 23 +++++++++++++++++++++--
> 1 file changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp
> b/src/mesa/drivers/dri/i965/brw_fs.cpp
> index ce84d0a..98cbf9f 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
> @@ -1844,11 +1844,30 @@ fs_visitor::convert_attr_sources_to_hw_regs(fs_inst
> *inst)
> inst->src[i].nr +
> inst->src[i].reg_offset;
>
> - unsigned width = inst->src[i].stride == 0 ? 1 : inst->exec_size;
> + unsigned exec_size;
Blank line here.
> + /* As explained at brw_reg_from_fs_reg, From the Haswell PRM:
> + *
> + * VertStride must be used to cross GRF register boundaries. This
> + * rule implies that elements within a 'Width' cannot cross GRF
> + * boundaries.
> + *
> + * So, for registers that are large enough, we have to split the
> exec
> + * size in two and trust the compression state to sort it out.
> + */
> + unsigned total_size = inst->exec_size *
> + inst->src[i].stride *
> + type_sz(inst->src[i].type);
const unsigned total_size = ... ;
I think the code below is better as
assert(total_size <= 64);
const unsigned exec_size = (total_size <= 32) ? inst->exec_size :
inst->exec_size / 2;
I'll defer to one of the people who work more in the back end.
> + if (total_size <= 32) {
> + exec_size = inst->exec_size;
> + } else {
> + assert(total_size / 2 <= 32);
> + exec_size = inst->exec_size / 2;
> + }
> + unsigned width = inst->src[i].stride == 0 ? 1 : exec_size;
> struct brw_reg reg =
> stride(byte_offset(retype(brw_vec8_grf(grf, 0),
> inst->src[i].type),
> inst->src[i].subreg_offset),
> - inst->exec_size * inst->src[i].stride,
> + exec_size * inst->src[i].stride,
> width, inst->src[i].stride);
> reg.abs = inst->src[i].abs;
> reg.negate = inst->src[i].negate;
>
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