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radeonsi: rework MSAA resolve averaging to exploit instruction-level parallelism

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Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21860>
This commit is contained in:
Marek Olšák
2023-03-06 13:28:42 -05:00
committed by Marge Bot
parent 1d978917a0
commit e32700c503
1 changed files with 25 additions and 6 deletions
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src/gallium/drivers/radeonsi/si_shaderlib_nir.c
+25 -6
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@@ -327,6 +327,30 @@ static nir_ssa_def *convert_linear_to_srgb(nir_builder *b, nir_ssa_def *input)
return nir_vec(b, comp, 4);
}
static nir_ssa_def *average_samples(nir_builder *b, nir_ssa_def **samples, unsigned num_samples)
{
/* This works like add-reduce by computing the sum of each pair independently, and then
* computing the sum of each pair of sums, and so on, to get better instruction-level
* parallelism.
*/
if (num_samples == 16) {
for (unsigned i = 0; i < 8; i++)
samples[i] = nir_fadd(b, samples[i * 2], samples[i * 2 + 1]);
}
if (num_samples >= 8) {
for (unsigned i = 0; i < 4; i++)
samples[i] = nir_fadd(b, samples[i * 2], samples[i * 2 + 1]);
}
if (num_samples >= 4) {
for (unsigned i = 0; i < 2; i++)
samples[i] = nir_fadd(b, samples[i * 2], samples[i * 2 + 1]);
}
if (num_samples >= 2)
samples[0] = nir_fadd(b, samples[0], samples[1]);
return nir_fmul_imm(b, samples[0], 1.0 / num_samples); /* average the sum */
}
static nir_ssa_def *image_resolve_msaa(nir_builder *b, nir_variable *img, unsigned num_samples,
nir_ssa_def *coord, enum amd_gfx_level gfx_level)
{
@@ -363,12 +387,7 @@ static nir_ssa_def *image_resolve_msaa(nir_builder *b, nir_variable *img, unsign
coord, sample_index[i], zero);
}
/* Average all samples. (the only options on gfx11) */
result = NULL;
for (unsigned i = 0; i < num_samples; i++) {
result = i ? nir_fadd(b, result, samples[i]) : samples[i];
}
result = nir_fmul_imm(b, result, 1.0 / num_samples); /* average the sum */
result = average_samples(b, samples, num_samples);
if (gfx_level < GFX11) {
/* Exit the conditional branch and get the result out of the branch. */