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nir/lower_clip: implement ClipVertex lowering for GS + lowered IO correctly

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This is currently needed to fix d3d12 for st_unlower_io_to_vars.

The idea is to track the current value of ClipVertex in a temporary
variable, and for every emit_vertex, we load the ClipVertex value from
the temporary (which matches the stored value) and insert new CLIP_DIST
stores before emit_vertex.

Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32363>
This commit is contained in:
Marek Olšák 2024-11-26 20:03:26 -05:00 • committed by Marge Bot
parent a648acc287
commit c50c9e9bf9
1 changed files with 68 additions and 11 deletions
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79
src/compiler/nir/nir_lower_clip.c
View file

@ -150,10 +150,6 @@ load_clipdist_input(nir_builder *b, nir_variable *in, int location_offset,
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)
{
@ -271,6 +267,9 @@ struct lower_clip_state {
unsigned ucp_enables;
bool use_clipdist_array;
const gl_state_index16 (*clipplane_state_tokens)[STATE_LENGTH];
/* This holds the current CLIP_VERTEX value for GS. */
nir_variable *clipvertex_gs_temp;
};
static void
@ -318,9 +317,15 @@ static void
lower_clip_vertex_intrin(nir_builder *b, const struct lower_clip_state *state)
{
nir_def *clipdist[MAX_CLIP_PLANES] = {NULL};
nir_def *cv =
find_output(b, b->shader->info.outputs_written & VARYING_BIT_CLIP_VERTEX ?
VARYING_SLOT_CLIP_VERTEX : VARYING_SLOT_POS);
nir_def *cv;
if (state->clipvertex_gs_temp) {
cv = nir_load_deref(b, nir_build_deref_var(b, state->clipvertex_gs_temp));
} else {
cv = find_output(b, b->shader->info.outputs_written &
VARYING_BIT_CLIP_VERTEX ?
VARYING_SLOT_CLIP_VERTEX : VARYING_SLOT_POS);
}
for (int plane = 0; plane < MAX_CLIP_PLANES; plane++) {
if (state->ucp_enables & (1 << plane)) {
@ -423,6 +428,10 @@ nir_lower_clip_vs(nir_shader *shader, unsigned ucp_enables, bool use_vars,
return true;
}
/*
* GS lowering
*/
static bool
lower_clip_vertex_gs(nir_builder *b, nir_intrinsic_instr *intr, void *opaque)
{
@ -443,9 +452,49 @@ lower_clip_vertex_gs(nir_builder *b, nir_intrinsic_instr *intr, void *opaque)
}
}
/*
* GS lowering
/* Track the CLIP_VERTEX or POS value in a local variable, so that we can
* retrieve it at emit_vertex.
*/
static bool
save_clipvertex_to_temp_gs(nir_builder *b, nir_intrinsic_instr *intr,
void *opaque)
{
const struct lower_clip_state *state =
(const struct lower_clip_state *)opaque;
gl_varying_slot clip_output_slot =
b->shader->info.outputs_written & VARYING_BIT_CLIP_VERTEX ?
VARYING_SLOT_CLIP_VERTEX : VARYING_SLOT_POS;
if (intr->intrinsic != nir_intrinsic_store_output ||
nir_intrinsic_io_semantics(intr).location != clip_output_slot)
return false;
b->cursor = nir_before_instr(&intr->instr);
unsigned component = nir_intrinsic_component(intr);
unsigned writemask = nir_intrinsic_write_mask(intr);
nir_def *value = intr->src[0].ssa;
/* Shift vector elements to the right by component. */
if (component) {
unsigned swizzle[4] = {0};
for (unsigned i = 1; i < value->num_components; i++)
swizzle[component + i] = i;
value = nir_swizzle(b, value, swizzle,
component + value->num_components);
}
nir_store_deref(b, nir_build_deref_var(b, state->clipvertex_gs_temp),
nir_pad_vec4(b, value), writemask << component);
/* Remove the CLIP_VERTEX store because it will be replaced by CLIP_DIST
* stores.
*/
if (clip_output_slot == VARYING_SLOT_CLIP_VERTEX)
nir_instr_remove(&intr->instr);
return true;
}
bool
nir_lower_clip_gs(nir_shader *shader, unsigned ucp_enables,
@ -467,8 +516,16 @@ nir_lower_clip_gs(nir_shader *shader, unsigned ucp_enables,
shader->info.clip_distance_array_size = util_last_bit(ucp_enables);
/* insert CLIPDIST outputs */
if (!shader->info.io_lowered) {
if (shader->info.io_lowered) {
/* Track the current value of CLIP_VERTEX or POS in a local variable. */
state.clipvertex_gs_temp =
nir_local_variable_create(nir_shader_get_entrypoint(shader),
glsl_vec4_type(), "clipvertex_gs_temp");
if (!nir_shader_intrinsics_pass(shader, save_clipvertex_to_temp_gs,
nir_metadata_control_flow, &state))
return false;
} else {
/* insert CLIPDIST outputs */
create_clipdist_vars(shader, state.out, ucp_enables, true,
use_clipdist_array);
}