[Mesa-dev] [PATCH v3 2/2] i965/vec4: load dvec3/4 uniforms first in the push constant buffer
Francisco Jerez
currojerez at riseup.net
Wed May 3 23:47:31 UTC 2017
Samuel Iglesias Gonsálvez <siglesias at igalia.com> writes:
> Reorder the uniforms to load first the dvec4-aligned variables
> in the push constant buffer and then push the vec4-aligned ones.
>
> This fixes a bug were the dvec3/4 might be loaded one part on a GRF and
> the rest in next GRF, so the region parameters to read that could break
> the HW rules.
>
> v2:
> - Fix broken logic.
> - Add a comment to explain what should be needed to optimise the usage
> of the push constant buffer slots, as this patch does not pack the
> uniforms.
>
> Signed-off-by: Samuel Iglesias Gonsálvez <siglesias at igalia.com>
> Cc: "17.1" <mesa-stable at lists.freedesktop.org>
> ---
> src/intel/compiler/brw_vec4.cpp | 97 +++++++++++++++++++++++++++++++----------
> 1 file changed, 74 insertions(+), 23 deletions(-)
>
> diff --git a/src/intel/compiler/brw_vec4.cpp b/src/intel/compiler/brw_vec4.cpp
> index 0909ddb586..18bfd48fa1 100644
> --- a/src/intel/compiler/brw_vec4.cpp
> +++ b/src/intel/compiler/brw_vec4.cpp
> @@ -583,16 +583,44 @@ vec4_visitor::split_uniform_registers()
> }
> }
>
> +/* This function returns the register number where we placed the uniform */
> +static int
> +set_push_constant_loc(const int nr_uniforms, int *new_uniform_count,
> + const int src, const int size,
> + int *new_loc, int *new_chan,
> + int *new_chans_used)
> +{
> + int dst;
> + /* Find the lowest place we can slot this uniform in. */
> + for (dst = 0; dst < nr_uniforms; dst++) {
> + if (new_chans_used[dst] + size <= 4)
> + break;
> + }
> +
> + assert(dst < nr_uniforms);
> +
> + new_loc[src] = dst;
> + new_chan[src] = new_chans_used[dst];
> + new_chans_used[dst] += size;
> +
> + *new_uniform_count = MAX2(*new_uniform_count, dst + 1);
> + return dst;
> +}
> +
> void
> vec4_visitor::pack_uniform_registers()
> {
> uint8_t chans_used[this->uniforms];
> int new_loc[this->uniforms];
> int new_chan[this->uniforms];
> + bool is_aligned_to_dvec4[this->uniforms];
> + int new_chans_used[this->uniforms];
>
> memset(chans_used, 0, sizeof(chans_used));
> memset(new_loc, 0, sizeof(new_loc));
> memset(new_chan, 0, sizeof(new_chan));
> + memset(new_chans_used, 0, sizeof(new_chans_used));
> + memset(is_aligned_to_dvec4, 0, sizeof(is_aligned_to_dvec4));
>
> /* Find which uniform vectors are actually used by the program. We
> * expect unused vector elements when we've moved array access out
> @@ -631,10 +659,19 @@ vec4_visitor::pack_uniform_registers()
>
> unsigned channel = BRW_GET_SWZ(inst->src[i].swizzle, c) + 1;
> unsigned used = MAX2(chans_used[reg], channel * channel_size);
> - if (used <= 4)
> - chans_used[reg] = used;
> - else
> - chans_used[reg + 1] = used - 4;
> + /* FIXME: Marked all channels as used, so each uniform will
> + * fully use one or two vec4s. If we want to pack them, we need
> + * to, among other changes, set chans_used[reg] = used;
> + * chans_used[reg+1] = used - 4; and fix the swizzle at the
> + * end in order to set the proper location.
> + */
> + if (used <= 4) {
> + chans_used[reg] = 4;
Uhm... So this change prevents the uniform packing pass from actually
packing anything? Might affect more applications negatively than broken
FP64 would. Are you planning to send a v3 that fixes the issue without
disabling the optimization? May be worth holding this off until then.
Even if that means it will miss the v17.1 release it will probably make
it for the next bug-fix release.
> + } else {
> + is_aligned_to_dvec4[reg] = true;
> + is_aligned_to_dvec4[reg + 1] = true;
> + chans_used[reg + 1] = 4;
> + }
> }
> }
>
> @@ -659,42 +696,56 @@ vec4_visitor::pack_uniform_registers()
>
> int new_uniform_count = 0;
>
> + /* As the uniforms are going to be reordered, take the data from a temporary
> + * copy of the original param[].
> + */
> + gl_constant_value **param = ralloc_array(NULL, gl_constant_value*,
> + stage_prog_data->nr_params);
> + memcpy(param, stage_prog_data->param,
> + sizeof(gl_constant_value*) * stage_prog_data->nr_params);
> +
> /* Now, figure out a packing of the live uniform vectors into our
> - * push constants.
> + * push constants. Start with dvec{3,4} because they are aligned to
> + * dvec4 size (2 vec4).
> */
> for (int src = 0; src < uniforms; src++) {
> int size = chans_used[src];
>
> - if (size == 0)
> + if (size == 0 || !is_aligned_to_dvec4[src])
> continue;
>
> - int dst;
> - /* Find the lowest place we can slot this uniform in. */
> - for (dst = 0; dst < src; dst++) {
> - if (chans_used[dst] + size <= 4)
> - break;
> + int dst = set_push_constant_loc(uniforms, &new_uniform_count,
> + src, size, new_loc, new_chan,
> + new_chans_used);
> + if (dst != src) {
> + /* Move the references to the data */
> + for (int j = 0; j < size; j++) {
> + stage_prog_data->param[dst * 4 + new_chan[src] + j] =
> + param[src * 4 + j];
> + }
> }
> + }
>
> - if (src == dst) {
> - new_loc[src] = dst;
> - new_chan[src] = 0;
> - } else {
> - new_loc[src] = dst;
> - new_chan[src] = chans_used[dst];
> + /* Continue with the rest of data, which is aligned to vec4. */
> + for (int src = 0; src < uniforms; src++) {
> + int size = chans_used[src];
> +
> + if (size == 0 || is_aligned_to_dvec4[src])
> + continue;
>
> + int dst = set_push_constant_loc(uniforms, &new_uniform_count,
> + src, size, new_loc, new_chan,
> + new_chans_used);
> + if (dst != src) {
> /* Move the references to the data */
> for (int j = 0; j < size; j++) {
> stage_prog_data->param[dst * 4 + new_chan[src] + j] =
> - stage_prog_data->param[src * 4 + j];
> + param[src * 4 + j];
> }
> -
> - chans_used[dst] += size;
> - chans_used[src] = 0;
> }
> -
> - new_uniform_count = MAX2(new_uniform_count, dst + 1);
> }
>
> + ralloc_free(param);
> this->uniforms = new_uniform_count;
>
> /* Now, update the instructions for our repacked uniforms. */
> --
> 2.11.0
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