[Mesa-dev] [PATCH 2/3] nir: add varying component packing helpers
Timothy Arceri
tarceri at itsqueeze.com
Wed Oct 18 11:22:11 UTC 2017
This packing pass is relatively simple, it only packs scalar
components. To be effective it relies on nir_lower_io_to_scalar_early()
having already split the majority of varyings into scalar components.
We may wish to add matrix and array support at some point however
a matrix/array splitting pass would also take care of the majority
of cases.
---
src/compiler/nir/nir.h | 2 +
src/compiler/nir/nir_linking_helpers.c | 237 +++++++++++++++++++++++++++++++++
2 files changed, 239 insertions(+)
diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 70c23c2db99..e3de6c3dfe8 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -2423,6 +2423,8 @@ void nir_assign_var_locations(struct exec_list *var_list, unsigned *size,
/* Some helpers to do very simple linking */
bool nir_remove_unused_varyings(nir_shader *producer, nir_shader *consumer);
+void nir_compact_varyings(nir_shader *producer, nir_shader *consumer,
+ bool default_to_smooth_interp);
typedef enum {
/* If set, this forces all non-flat fragment shader inputs to be
diff --git a/src/compiler/nir/nir_linking_helpers.c b/src/compiler/nir/nir_linking_helpers.c
index 5591f9be820..3de30650a2e 100644
--- a/src/compiler/nir/nir_linking_helpers.c
+++ b/src/compiler/nir/nir_linking_helpers.c
@@ -150,3 +150,240 @@ nir_remove_unused_varyings(nir_shader *producer, nir_shader *consumer)
return progress;
}
+
+static uint8_t
+get_interp_type(nir_variable *var, bool default_to_smooth_interp)
+{
+ return var->data.interpolation == INTERP_MODE_NONE &&
+ default_to_smooth_interp ?
+ INTERP_MODE_SMOOTH : var->data.interpolation;
+}
+
+static void
+get_slot_component_masks_and_interp_types(struct exec_list *var_list,
+ uint8_t *comps, uint8_t *interp_type,
+ gl_shader_stage stage,
+ bool default_to_smooth_interp)
+{
+ nir_foreach_variable_safe(var, var_list) {
+ assert(var->data.location >= 0);
+
+ /* Only remap things that aren't built-ins.
+ * TODO: add TES patch support.
+ */
+ if (var->data.location >= VARYING_SLOT_VAR0 &&
+ var->data.location - VARYING_SLOT_VAR0 < 32) {
+
+ const struct glsl_type *type = var->type;
+ if (nir_is_per_vertex_io(var, stage)) {
+ assert(glsl_type_is_array(type));
+ type = glsl_get_array_element(type);
+ }
+
+ unsigned location = var->data.location - VARYING_SLOT_VAR0;
+ unsigned elements =
+ glsl_get_vector_elements(glsl_without_array(type));
+
+ bool dual_slot = glsl_type_is_dual_slot(glsl_without_array(type));
+ unsigned slots = glsl_count_attribute_slots(type, false);
+ for (unsigned i = 0; i < slots; i++) {
+ interp_type[location + i] =
+ get_interp_type(var, default_to_smooth_interp);
+
+ if (dual_slot) {
+ unsigned comps_slot2 = 0;
+ if (i & 1) {
+ comps[location + i] |= ((1 << comps_slot2) - 1);
+ } else {
+ unsigned num_comps = 4 - var->data.location_frac;
+ comps_slot2 = (elements * 2) - num_comps;
+
+ /* Assume ARB_enhanced_layouts packing rules for doubles */
+ assert(var->data.location_frac == 0 ||
+ var->data.location_frac == 2);
+ assert(comps_slot2 <= 4);
+
+ comps[location + i] |=
+ ((1 << num_comps) - 1) << var->data.location_frac;
+ }
+ } else {
+ comps[location + i] |=
+ ((1 << elements) - 1) << var->data.location_frac;
+ }
+ }
+ }
+ }
+}
+
+struct varying_loc
+{
+ uint8_t component;
+ uint32_t location;
+};
+
+static void
+remap_slots_and_components(struct exec_list *var_list,
+ struct varying_loc (*remap)[4])
+{
+ nir_foreach_variable(var, var_list) {
+ assert(var->data.location >= 0);
+
+ /* Only remap things that aren't built-ins */
+ if (var->data.location >= VARYING_SLOT_VAR0 &&
+ var->data.location - VARYING_SLOT_VAR0 < 32) {
+ assert(var->data.location - VARYING_SLOT_VAR0 < 32);
+ assert(remap[var->data.location - VARYING_SLOT_VAR0] >= 0);
+
+ unsigned location = var->data.location - VARYING_SLOT_VAR0;
+ struct varying_loc *new_loc = &remap[location][var->data.location_frac];
+ if (new_loc->location) {
+ var->data.location = new_loc->location;
+ var->data.location_frac = new_loc->component;
+ }
+ }
+ }
+}
+
+/* If there are empty components in the slot compact the remaining components
+ * as close to component 0 as possible. This will make it easier to fill the
+ * empty components with components from a different slot in a following pass.
+ */
+static void
+compact_components(nir_shader *producer, nir_shader *consumer, uint8_t *comps,
+ uint8_t *interp_type, bool default_to_smooth_interp)
+{
+ struct exec_list *input_list = &consumer->inputs;
+ struct exec_list *output_list = &producer->outputs;
+ struct varying_loc remap[32][4] = {{{0}, {0}}};
+
+ /* Create a cursor for each interpolation type */
+ unsigned cursor[4] = {0};
+
+ /* We only need to pass over one stage and we choose the consumer as it seems
+ * to cause a larger reduction in instruction counts (tested on i965).
+ *
+ * TODO: However since its possible to have more outputs than the consumer
+ * has inputs, it might be better to pack based on the outputs in some
+ * instances. More investigation could be useful here.
+ */
+ nir_foreach_variable(var, input_list) {
+
+ /* Only remap things that aren't builtins.
+ * TODO: add TES patch support.
+ */
+ if (var->data.location >= VARYING_SLOT_VAR0 &&
+ var->data.location - VARYING_SLOT_VAR0 < 32) {
+
+ const struct glsl_type *type = var->type;
+ if (nir_is_per_vertex_io(var, consumer->stage)) {
+ assert(glsl_type_is_array(type));
+ type = glsl_get_array_element(type);
+ }
+
+ /* Skip types that require more complex packing handling.
+ * TODO: add support for these types.
+ */
+ if (glsl_type_is_array(type) ||
+ glsl_type_is_dual_slot(type) ||
+ glsl_type_is_matrix(type) ||
+ glsl_type_is_struct(type) ||
+ glsl_type_is_64bit(type))
+ continue;
+
+ /* We ignore complex types above and all other vector types should
+ * have been split into scalar variables by the lower_io_to_scalar
+ * pass. The only exeption should by OpenGL xfb varyings.
+ */
+ if (glsl_get_vector_elements(type) != 1)
+ continue;
+
+ unsigned location = var->data.location - VARYING_SLOT_VAR0;
+ uint8_t used_comps = comps[location];
+
+ /* If there are no empty components there is nothing more for us to do.
+ */
+ if (used_comps == 0xf)
+ continue;
+
+ bool found_new_offset = false;
+ uint8_t interp = get_interp_type(var, default_to_smooth_interp);
+ for (; cursor[interp] < 32; cursor[interp]++) {
+
+ /* We couldn't find anywhere to pack the varying continue on. */
+ if (cursor[interp] == location)
+ break;
+
+ /* We can only pack varyings with matching interpolation types */
+ if (interp_type[cursor[interp]] != interp)
+ continue;
+
+ uint8_t cursor_used_comps = comps[cursor[interp]];
+
+ /* If the slot is empty just skip it for now, compact_var_list()
+ * can be called after this function to remove empty slots for us.
+ * TODO: finish implementing compact_var_list() requires array and
+ * matrix splitting.
+ */
+ if (!cursor_used_comps)
+ continue;
+
+ uint8_t unused_comps = ~cursor_used_comps;
+
+ for (unsigned i = 0; i < 4; i++) {
+ uint8_t new_var_comps = 1 << i;
+ if (unused_comps & new_var_comps) {
+ remap[location][var->data.location_frac].component = i;
+ remap[location][var->data.location_frac].location =
+ cursor[interp] + VARYING_SLOT_VAR0;
+
+ found_new_offset = true;
+
+ /* Turn off the mask for the component we are remapping */
+ if (comps[location] & 1 << var->data.location_frac) {
+ comps[location] ^= 1 << var->data.location_frac;
+ comps[cursor[interp]] |= new_var_comps;
+ }
+ break;
+ }
+ }
+
+ if (found_new_offset)
+ break;
+ }
+ }
+ }
+
+ remap_slots_and_components(input_list, remap);
+ remap_slots_and_components(output_list, remap);
+}
+
+/* We assume that this has been called more-or-less directly after
+ * remove_unused_varyings. At this point, all of the varyings that we
+ * aren't going to be using have been completely removed and the
+ * inputs_read and outputs_written fields in nir_shader_info reflect
+ * this. Therefore, the total set of valid slots is the OR of the two
+ * sets of varyings; this accounts for varyings which one side may need
+ * to read/write even if the other doesn't. This can happen if, for
+ * instance, an array is used indirectly from one side causing it to be
+ * unsplittable but directly from the other.
+ */
+void
+nir_compact_varyings(nir_shader *producer, nir_shader *consumer,
+ bool default_to_smooth_interp)
+{
+ assert(producer->stage != MESA_SHADER_FRAGMENT);
+ assert(consumer->stage != MESA_SHADER_VERTEX);
+
+ uint8_t comps[32] = {0};
+ uint8_t interp_type[32] = {0};
+
+ get_slot_component_masks_and_interp_types(&producer->outputs, comps,
+ interp_type, producer->stage,
+ default_to_smooth_interp);
+ get_slot_component_masks_and_interp_types(&consumer->inputs, comps,
+ interp_type, consumer->stage,
+ default_to_smooth_interp);
+
+ compact_components(producer, consumer, comps, interp_type,
+ default_to_smooth_interp);
+}
--
2.13.6
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