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nir/lower_clip: make the pass compatible with Vulkan semantics

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Vulkan allows fragment shaders to read gl_ClipDistance[], in which
case the SPIR-V compiler inserts a single compact array variable for
VARYING_SLOW_CLIP_DIST0 and the lowering should not try to inject
its own variables, but instead work in terms of the existing one.
Vulkan drivers are expected to call this with use_clipdist_array set
to true to be consistent with this setup.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6022>
This commit is contained in:
Iago Toral Quiroga
2020-07-21 12:21:39 +02:00
parent 18fe130ec9
commit 17fd191eed
1 changed files with 43 additions and 13 deletions
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56
src/compiler/nir/nir_lower_clip.c
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@@ -81,7 +81,7 @@ create_clipdist_vars(nir_shader *shader, nir_variable **io_vars,
{
if (use_clipdist_array) {
io_vars[0] =
create_clipdist_var(shader, true,
create_clipdist_var(shader, output,
VARYING_SLOT_CLIP_DIST0,
util_last_bit(ucp_enables));
} else {
@@ -112,13 +112,14 @@ store_clipdist_output(nir_builder *b, nir_variable *out, nir_ssa_def **val)
}
static void
load_clipdist_input(nir_builder *b, nir_variable *in, nir_ssa_def **val)
load_clipdist_input(nir_builder *b, nir_variable *in, int location_offset,
nir_ssa_def **val)
{
nir_intrinsic_instr *load;
load = nir_intrinsic_instr_create(b->shader, nir_intrinsic_load_input);
load->num_components = 4;
nir_intrinsic_set_base(load, in->data.driver_location);
nir_intrinsic_set_base(load, in->data.driver_location + location_offset);
load->src[0] = nir_src_for_ssa(nir_imm_int(b, 0));
nir_ssa_dest_init(&load->instr, &load->dest, 4, 32, NULL);
nir_builder_instr_insert(b, &load->instr);
@@ -419,7 +420,7 @@ nir_lower_clip_gs(nir_shader *shader, unsigned ucp_enables,
static void
lower_clip_fs(nir_function_impl *impl, unsigned ucp_enables,
nir_variable **in)
nir_variable **in, bool use_clipdist_array)
{
nir_ssa_def *clipdist[MAX_CLIP_PLANES];
nir_builder b;
@@ -427,10 +428,17 @@ lower_clip_fs(nir_function_impl *impl, unsigned ucp_enables,
nir_builder_init(&b, impl);
b.cursor = nir_before_cf_list(&impl->body);
if (ucp_enables & 0x0f)
load_clipdist_input(&b, in[0], &clipdist[0]);
if (ucp_enables & 0xf0)
load_clipdist_input(&b, in[1], &clipdist[4]);
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]);
}
for (int plane = 0; plane < MAX_CLIP_PLANES; plane++) {
if (ucp_enables & (1 << plane)) {
@@ -451,6 +459,25 @@ lower_clip_fs(nir_function_impl *impl, unsigned ucp_enables,
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_variable(var, &shader->inputs) {
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
@@ -462,15 +489,18 @@ nir_lower_clip_fs(nir_shader *shader, unsigned ucp_enables,
if (!ucp_enables)
return false;
/* The shader won't normally have CLIPDIST inputs, so we
* must add our own:
/* Fragment shaders can't read gl_ClipDistance[] in OpenGL so it will not
* have the variable defined, but Vulkan allows this, in which case the
* SPIR-V compiler would have already added it as a compact array.
*/
/* insert CLIPDIST inputs */
create_clipdist_vars(shader, in, ucp_enables, false, use_clipdist_array);
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(function, shader) {
if (!strcmp(function->name, "main"))
lower_clip_fs(function->impl, ucp_enables, in);
lower_clip_fs(function->impl, ucp_enables, in, use_clipdist_array);
}
return true;