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ac/nir: cull triangles/lines when all W positions are zero/NaN

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It looks like the fixed-func hardware is very slow to cull primitives
with zero pos.w but shader based culling helps a lot.

This fixes a massive performance gap with the FSR2 demo compared to
AMDGPU-PRO, +228% on RDNA2.

Based on my investigation, AMDGPU-PRO seems to always cull these
primitives. Note that disabling NGG culling with AMDGPU-PRO reports the
same performance as RADV without that fix. Also note that the FSR2
sample doesn't specify any cull mode (ie. VK_CULL_MODE_NONE is used),
so this is the only reason PRO was culling more than RADV.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/7260
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/31891>
This commit is contained in:
Samuel Pitoiset
2024-10-29 17:47:07 +01:00
committed by Marge Bot
parent 322a83f321
commit 7015e22cb6
1 changed files with 7 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/amd/common/ac_nir_cull.c
+7 -5
View File
@@ -14,7 +14,7 @@
typedef struct
{
nir_def *w_reflection;
nir_def *all_w_negative;
nir_def *all_w_negative_or_zero_or_nan;
nir_def *any_w_negative;
} position_w_info;
@@ -22,15 +22,17 @@ static void
analyze_position_w(nir_builder *b, nir_def *pos[][4], unsigned num_vertices,
position_w_info *w_info)
{
w_info->all_w_negative = nir_imm_true(b);
w_info->all_w_negative_or_zero_or_nan = nir_imm_true(b);
w_info->w_reflection = nir_imm_false(b);
w_info->any_w_negative = nir_imm_false(b);
for (unsigned i = 0; i < num_vertices; ++i) {
nir_def *neg_w = nir_flt_imm(b, pos[i][3], 0.0f);
nir_def *neg_or_zero_or_nan_w = nir_fgeu(b, nir_imm_float(b, 0.0f), pos[i][3]);
w_info->w_reflection = nir_ixor(b, neg_w, w_info->w_reflection);
w_info->any_w_negative = nir_ior(b, neg_w, w_info->any_w_negative);
w_info->all_w_negative = nir_iand(b, neg_w, w_info->all_w_negative);
w_info->all_w_negative_or_zero_or_nan = nir_iand(b, neg_or_zero_or_nan_w, w_info->all_w_negative_or_zero_or_nan);
}
}
@@ -131,7 +133,7 @@ ac_nir_cull_triangle(nir_builder *b,
void *state)
{
nir_def *accepted = initially_accepted;
accepted = nir_iand(b, accepted, nir_inot(b, w_info->all_w_negative));
accepted = nir_iand(b, accepted, nir_inot(b, w_info->all_w_negative_or_zero_or_nan));
accepted = nir_iand(b, accepted, nir_inot(b, cull_face_triangle(b, pos, w_info)));
nir_def *bbox_accepted = NULL;
@@ -303,7 +305,7 @@ ac_nir_cull_line(nir_builder *b,
void *state)
{
nir_def *accepted = initially_accepted;
accepted = nir_iand(b, accepted, nir_inot(b, w_info->all_w_negative));
accepted = nir_iand(b, accepted, nir_inot(b, w_info->all_w_negative_or_zero_or_nan));
nir_def *bbox_accepted = NULL;