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mesa/src/compiler/nir/nir_lower_clip.c

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/*
* Copyright © 2015 Red Hat
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*
* Authors:
* Rob Clark <robclark@freedesktop.org>
*/
#include "nir.h"
#include "nir_builder.h"
#define MAX_CLIP_PLANES 8
/* Generates the lowering code for user-clip-planes, generating CLIPDIST
* from UCP[n] + CLIPVERTEX or POSITION. Additionally, an optional pass
* for fragment shaders to insert conditional kills based on the inter-
* polated CLIPDIST
*
* NOTE: should be run after nir_lower_outputs_to_temporaries() (or at
* least in scenarios where you can count on each output written once
* and only once).
*/
static nir_variable *
create_clipdist_var(nir_shader *shader,
bool output, gl_varying_slot slot, unsigned array_size)
{
nir_variable *var = rzalloc(shader, nir_variable);
if (output) {
var->data.driver_location = shader->num_outputs;
var->data.mode = nir_var_shader_out;
shader->num_outputs += MAX2(1, DIV_ROUND_UP(array_size, 4));
} else {
var->data.driver_location = shader->num_inputs;
var->data.mode = nir_var_shader_in;
shader->num_inputs += MAX2(1, DIV_ROUND_UP(array_size, 4));
}
var->name = ralloc_asprintf(var, "clipdist_%d", var->data.driver_location);
var->data.index = 0;
var->data.location = slot;
if (array_size > 0) {
var->type = glsl_array_type(glsl_float_type(), array_size,
sizeof(float));
var->data.compact = 1;
} else
var->type = glsl_vec4_type();
nir_shader_add_variable(shader, var);
return var;
}
static void
create_clipdist_vars(nir_shader *shader, nir_variable **io_vars,
unsigned ucp_enables, bool output,
bool use_clipdist_array)
{
shader->info.clip_distance_array_size = util_last_bit(ucp_enables);
if (shader->info.io_lowered)
return;
if (use_clipdist_array) {
io_vars[0] =
create_clipdist_var(shader, output,
VARYING_SLOT_CLIP_DIST0,
shader->info.clip_distance_array_size);
} else {
if (ucp_enables & 0x0f)
io_vars[0] =
create_clipdist_var(shader, output,
VARYING_SLOT_CLIP_DIST0, 0);
if (ucp_enables & 0xf0)
io_vars[1] =
create_clipdist_var(shader, output,
VARYING_SLOT_CLIP_DIST1, 0);
}
}
static void
store_clipdist_output(nir_builder *b, nir_variable *out, int location, int location_offset,
nir_def **val, bool use_clipdist_array)
{
unsigned num_slots = b->shader->info.clip_distance_array_size;
nir_io_semantics semantics = {
.location = location,
.num_slots = num_slots,
};
if (location == VARYING_SLOT_CLIP_DIST1 || location_offset)
num_slots -= 4;
else
num_slots = MIN2(num_slots, 4);
for (unsigned i = 0; i < num_slots; i++) {
nir_store_output(b,
val[i] ? val[i] : nir_imm_zero(b, 1, 32),
nir_imm_int(b, location_offset),
.src_type = nir_type_float32,
.write_mask = 0x1,
.component = i,
.io_semantics = semantics,
.base = out ? out->data.driver_location : 0);
}
}
static void
load_clipdist_input(nir_builder *b, nir_variable *in, int location_offset,
nir_def **val)
{
nir_io_semantics semantics = {
.location = in->data.location,
.num_slots = 1,
};
nir_def *load;
if (b->shader->options->use_interpolated_input_intrinsics) {
/* TODO: use sample when per-sample shading? */
nir_def *barycentric = nir_load_barycentric(
b, nir_intrinsic_load_barycentric_pixel, INTERP_MODE_NONE);
load = nir_load_interpolated_input(
b, 4, 32, barycentric, nir_imm_int(b, location_offset),
.base = in->data.driver_location,
.dest_type = nir_type_float32,
.io_semantics = semantics);
} else {
load = nir_load_input(b, 4, 32, nir_imm_int(b, location_offset),
.base = in->data.driver_location,
.dest_type = nir_type_float32,
.io_semantics = semantics);
}
val[0] = nir_channel(b, load, 0);
val[1] = nir_channel(b, load, 1);
val[2] = nir_channel(b, load, 2);
val[3] = nir_channel(b, load, 3);
}
/* TODO: maybe this would be a useful helper?
* NOTE: assumes each output is written exactly once (and unconditionally)
* so if needed nir_lower_outputs_to_temporaries()
*/
static nir_def *
find_output(nir_builder *b, unsigned location)
{
nir_def *def = NULL;
nir_def *components[4] = {NULL};
nir_instr *first = NULL;
unsigned found = 0;
nir_foreach_function_impl(impl, b->shader) {
nir_foreach_block_reverse(block, impl) {
nir_def *new_def = NULL;
nir_foreach_instr_reverse(instr, block) {
if (instr->type != nir_instr_type_intrinsic)
continue;
nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
if ((intr->intrinsic == nir_intrinsic_store_output ||
intr->intrinsic == nir_intrinsic_store_per_vertex_output ||
intr->intrinsic == nir_intrinsic_store_per_primitive_output) &&
nir_intrinsic_io_semantics(intr).location == location) {
assert(nir_src_is_const(*nir_get_io_offset_src(intr)));
int wrmask = nir_intrinsic_write_mask(intr);
if (intr->num_components == 4 && wrmask == 0xf) {
new_def = intr->src[0].ssa;
} else {
int c = nir_intrinsic_component(intr);
assert(intr->num_components == 1 && wrmask == 0x1);
assert(!components[c]);
components[c] = intr->src[0].ssa;
if (!first)
first = &intr->instr;
found++;
}
}
}
assert(!(new_def && def));
if (!def)
def = new_def;
#if !MESA_DEBUG
/* for debug builds, scan entire shader to assert
* if output is written multiple times. For release
* builds just assume all is well and bail when we
* find first:
*/
if (def || found == 4)
break;
#endif
}
}
assert(def || found == 4);
if (found) {
b->cursor = nir_after_instr(first);
def = nir_vec(b, components, 4);
}
return def;
}
static bool
find_clipvertex_and_position_outputs(nir_shader *shader,
nir_variable **clipvertex,
nir_variable **position)
{
if (shader->info.io_lowered) {
if (shader->info.outputs_written & (VARYING_BIT_CLIP_DIST0 | VARYING_BIT_CLIP_DIST1))
return false;
if (shader->info.outputs_written & (VARYING_BIT_POS | VARYING_BIT_CLIP_VERTEX))
return true;
return false;
}
nir_foreach_shader_out_variable(var, shader) {
switch (var->data.location) {
case VARYING_SLOT_POS:
*position = var;
break;
case VARYING_SLOT_CLIP_VERTEX:
*clipvertex = var;
break;
case VARYING_SLOT_CLIP_DIST0:
case VARYING_SLOT_CLIP_DIST1:
/* if shader is already writing CLIPDIST, then
* there should be no user-clip-planes to deal
* with.
*
* We assume nir_remove_dead_variables has removed the clipdist
* variables if they're not written.
*/
return false;
}
}
return *clipvertex || *position;
}
static nir_def *
get_ucp(nir_builder *b, int plane,
const gl_state_index16 clipplane_state_tokens[][STATE_LENGTH])
{
if (clipplane_state_tokens) {
char tmp[100];
snprintf(tmp, ARRAY_SIZE(tmp), "gl_ClipPlane%dMESA", plane);
nir_variable *var = nir_state_variable_create(b->shader,
glsl_vec4_type(),
tmp, clipplane_state_tokens[plane]);
return nir_load_var(b, var);
} else
return nir_load_user_clip_plane(b, plane);
}
static void
lower_clip_outputs(nir_builder *b, nir_variable *position,
nir_variable *clipvertex, nir_variable **out,
unsigned ucp_enables, bool use_vars,
bool use_clipdist_array,
const gl_state_index16 clipplane_state_tokens[][STATE_LENGTH])
{
nir_def *clipdist[MAX_CLIP_PLANES] = {NULL};
nir_def *cv;
if (use_vars) {
cv = nir_load_var(b, clipvertex ? clipvertex : position);
if (clipvertex) {
clipvertex->data.mode = nir_var_shader_temp;
nir_fixup_deref_modes(b->shader);
}
} else {
if (b->shader->info.outputs_written & VARYING_BIT_CLIP_VERTEX)
cv = find_output(b, VARYING_SLOT_CLIP_VERTEX);
else {
cv = find_output(b, VARYING_SLOT_POS);
}
}
for (int plane = 0; plane < MAX_CLIP_PLANES; plane++) {
if (ucp_enables & (1 << plane)) {
nir_def *ucp = get_ucp(b, plane, clipplane_state_tokens);
/* calculate clipdist[plane] - dot(ucp, cv): */
clipdist[plane] = nir_fdot(b, ucp, cv);
} else {
/* 0.0 == don't-clip == disabled: */
clipdist[plane] = nir_imm_float(b, 0.0);
}
if (use_clipdist_array && use_vars && plane < util_last_bit(ucp_enables)) {
nir_deref_instr *deref;
deref = nir_build_deref_array_imm(b,
nir_build_deref_var(b, out[0]),
plane);
nir_store_deref(b, deref, clipdist[plane], 1);
}
}
if (!use_clipdist_array || !use_vars) {
if (use_vars) {
if (ucp_enables & 0x0f)
nir_store_var(b, out[0], nir_vec(b, clipdist, 4), 0xf);
if (ucp_enables & 0xf0)
nir_store_var(b, out[1], nir_vec(b, &clipdist[4], 4), 0xf);
} else if (use_clipdist_array) {
/* always emit first half of array */
store_clipdist_output(b, out[0], VARYING_SLOT_CLIP_DIST0, 0, &clipdist[0], use_clipdist_array);
if (ucp_enables & 0xf0)
store_clipdist_output(b, out[0], VARYING_SLOT_CLIP_DIST0, 1, &clipdist[4], use_clipdist_array);
} else {
if (ucp_enables & 0x0f)
store_clipdist_output(b, out[0], VARYING_SLOT_CLIP_DIST0, 0, &clipdist[0], use_clipdist_array);
if (ucp_enables & 0xf0)
store_clipdist_output(b, out[1], VARYING_SLOT_CLIP_DIST1, 0, &clipdist[4], use_clipdist_array);
}
}
}
/*
* VS lowering
*/
/* ucp_enables is bitmask of enabled ucps. Actual ucp values are
* passed in to shader via user_clip_plane system-values
*
* If use_vars is true, the pass will use variable loads and stores instead
* of working with store_output intrinsics.
*
* If use_clipdist_array is true, the pass will use compact arrays for the
* clipdist output instead of two vec4s.
*/
bool
nir_lower_clip_vs(nir_shader *shader, unsigned ucp_enables, bool use_vars,
bool use_clipdist_array,
const gl_state_index16 clipplane_state_tokens[][STATE_LENGTH])
{
nir_function_impl *impl = nir_shader_get_entrypoint(shader);
nir_builder b;
nir_variable *position = NULL;
nir_variable *clipvertex = NULL;
nir_variable *out[2] = { NULL };
if (!ucp_enables)
return false;
if (shader->info.io_lowered)
use_vars = false;
b = nir_builder_create(impl);
/* NIR should ensure that, even in case of loops/if-else, there
* should be only a single predecessor block to end_block, which
* makes the perfect place to insert the clipdist calculations.
*
* NOTE: in case of early returns, these would have to be lowered
* to jumps to end_block predecessor in a previous pass. Not sure
* if there is a good way to sanity check this, but for now the
* users of this pass don't support sub-routines.
*/
assert(impl->end_block->predecessors->entries == 1);
b.cursor = nir_after_impl(impl);
/* find clipvertex/position outputs */
if (!find_clipvertex_and_position_outputs(shader, &clipvertex, &position))
return false;
/* insert CLIPDIST outputs */
create_clipdist_vars(shader, out, ucp_enables, true,
use_clipdist_array);
lower_clip_outputs(&b, position, clipvertex, out, ucp_enables, use_vars,
use_clipdist_array, clipplane_state_tokens);
nir_metadata_preserve(impl, nir_metadata_dominance);
return true;
}
static void
lower_clip_in_gs_block(nir_builder *b, nir_block *block, nir_variable *position,
nir_variable *clipvertex, nir_variable **out,
unsigned ucp_enables, bool use_clipdist_array,
const gl_state_index16 clipplane_state_tokens[][STATE_LENGTH])
{
nir_foreach_instr_safe(instr, block) {
if (instr->type != nir_instr_type_intrinsic)
continue;
nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
switch (intrin->intrinsic) {
case nir_intrinsic_emit_vertex_with_counter:
case nir_intrinsic_emit_vertex:
b->cursor = nir_before_instr(instr);
lower_clip_outputs(b, position, clipvertex, out, ucp_enables, !b->shader->info.io_lowered,
use_clipdist_array, clipplane_state_tokens);
break;
default:
/* not interesting; skip this */
break;
}
}
}
/*
* GS lowering
*/
bool
nir_lower_clip_gs(nir_shader *shader, unsigned ucp_enables,
bool use_clipdist_array,
const gl_state_index16 clipplane_state_tokens[][STATE_LENGTH])
{
nir_function_impl *impl = nir_shader_get_entrypoint(shader);
nir_builder b;
nir_variable *position = NULL;
nir_variable *clipvertex = NULL;
nir_variable *out[2] = { NULL };
if (!ucp_enables)
return false;
/* find clipvertex/position outputs */
if (!find_clipvertex_and_position_outputs(shader, &clipvertex, &position))
return false;
/* insert CLIPDIST outputs */
create_clipdist_vars(shader, out, ucp_enables, true,
use_clipdist_array);
b = nir_builder_create(impl);
nir_foreach_block(block, impl)
lower_clip_in_gs_block(&b, block, position, clipvertex, out,
ucp_enables, use_clipdist_array,
clipplane_state_tokens);
nir_metadata_preserve(impl, nir_metadata_dominance);
return true;
}
/*
* FS lowering
*/
static void
lower_clip_fs(nir_function_impl *impl, unsigned ucp_enables,
nir_variable **in, bool use_clipdist_array)
{
nir_def *clipdist[MAX_CLIP_PLANES];
nir_builder b = nir_builder_at(nir_before_impl(impl));
if (!use_clipdist_array) {
if (ucp_enables & 0x0f)
load_clipdist_input(&b, in[0], 0, &clipdist[0]);
if (ucp_enables & 0xf0)
load_clipdist_input(&b, in[1], 0, &clipdist[4]);
} else {
if (ucp_enables & 0x0f)
load_clipdist_input(&b, in[0], 0, &clipdist[0]);
if (ucp_enables & 0xf0)
load_clipdist_input(&b, in[0], 1, &clipdist[4]);
}
nir_def *cond = NULL;
for (int plane = 0; plane < MAX_CLIP_PLANES; plane++) {
if (ucp_enables & (1 << plane)) {
nir_def *this_cond =
nir_flt_imm(&b, clipdist[plane], 0.0);
cond = cond ? nir_ior(&b, cond, this_cond) : this_cond;
}
}
if (cond != NULL) {
nir_discard_if(&b, cond);
b.shader->info.fs.uses_discard = true;
}
nir_metadata_preserve(impl, nir_metadata_dominance);
}
static bool
fs_has_clip_dist_input_var(nir_shader *shader, nir_variable **io_vars,
unsigned *ucp_enables)
{
assert(shader->info.stage == MESA_SHADER_FRAGMENT);
nir_foreach_shader_in_variable(var, shader) {
switch (var->data.location) {
case VARYING_SLOT_CLIP_DIST0:
assert(var->data.compact);
io_vars[0] = var;
*ucp_enables &= (1 << glsl_get_length(var->type)) - 1;
return true;
default:
break;
}
}
return false;
}
/* insert conditional kill based on interpolated CLIPDIST
*/
bool
nir_lower_clip_fs(nir_shader *shader, unsigned ucp_enables,
bool use_clipdist_array)
{
nir_variable *in[2] = { 0 };
if (!ucp_enables)
return false;
/* this is probably broken until https://gitlab.freedesktop.org/mesa/mesa/-/issues/10826 is fixed */
assert(!shader->info.io_lowered);
/* No hard reason to require use_clipdist_arr to work with
* frag-shader-based gl_ClipDistance, except that the only user that does
* not enable this does not support GL 3.0 (or EXT_clip_cull_distance).
*/
if (!fs_has_clip_dist_input_var(shader, in, &ucp_enables))
create_clipdist_vars(shader, in, ucp_enables, false, use_clipdist_array);
else
assert(use_clipdist_array);
nir_foreach_function_with_impl(function, impl, shader) {
if (!strcmp(function->name, "main"))
lower_clip_fs(impl, ucp_enables, in, use_clipdist_array);
}
return true;
}
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