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r300: vectorization tweaks for R300/R400

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Vectorization can make the constant layout worse and increase
the constant register usage. The worst scenario is vectorization
lowered indirect register access, where we access i-th element
and later we access i-1 or i+1 (most notably glamor and gsk shaders).
In this case we already added constants 1..n where n is the array
size, however we can reuse them unless the lowered ladder gets
vectorized later.

Thus prevent vectorization of the specific patterns from lowered
indirect access.

This is quite a heavy hammer, we could in theory estimate how many
slots will the current ubos and constants need and only disable
vectorization when we are close to the limit. However, this would
likely need a global shader analysis each time r300_should_vectorize_inst
is called, which we want to avoid.

So for now just don't vectorize anything that loads constants if we
already have lot of uniforms.

This is the final missing piece to make glamor work on R400.

shader-db R420:
total instructions in shared programs: 107288 -> 107290 (<.01%)
instructions in affected programs: 236 -> 238 (0.85%)
helped: 2
HURT: 3
total temps in shared programs: 17730 -> 17726 (-0.02%)
temps in affected programs: 41 -> 37 (-9.76%)
helped: 4
HURT: 0
total cycles in shared programs: 163251 -> 163251 (0.00%)
cycles in affected programs: 478 -> 478 (0.00%)
helped: 2
HURT: 3
GAINED: 7 (2 glamor and 5 GSK shaders)

RV370 is quite similar instruction/temp-wise, but we don't gain any
shader there, because they are all over the 64 instructions limit...

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/10787
Signed-off-by: Pavel Ondračka <pavel.ondracka@gmail.com>
Reviewed-by: Filip Gawin <filip.gawin@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29734>
This commit is contained in:
Pavel Ondračka 2024-05-07 09:14:05 +02:00 • committed by Marge Bot
parent 5f68ba505b
commit 4b040577d5
1 changed files with 61 additions and 1 deletions
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62
src/gallium/drivers/r300/compiler/r300_nir.c
View file

@ -46,12 +46,69 @@ r300_is_only_used_as_float(const nir_alu_instr *instr)
static unsigned char
r300_should_vectorize_instr(const nir_instr *instr, const void *data)
{
bool *too_many_ubos = (bool *) data;
if (instr->type != nir_instr_type_alu)
return 0;
/* Vectorization can make the constant layout worse and increase
* the constant register usage. The worst scenario is vectorization
* of lowered indirect register access, where we access i-th element
* and later we access i-1 or i+1 (most notably glamor and gsk shaders).
* In this case we already added constants 1..n where n is the array
* size, however we can reuse them unless the lowered ladder gets
* vectorized later.
*
* Thus prevent vectorization of the specific patterns from lowered
* indirect access.
*
* This is quite a heavy hammer, we could in theory estimate how many
* slots will the current ubos and constants need and only disable
* vectorization when we are close to the limit. However, this would
* likely need a global shader analysis each time r300_should_vectorize_inst
* is called, which we want to avoid.
*
* So for now just don't vectorize anything that loads constants.
*/
if (*too_many_ubos) {
nir_alu_instr *alu = nir_instr_as_alu(instr);
unsigned num_srcs = nir_op_infos[alu->op].num_inputs;
for (unsigned i = 0; i < num_srcs; i++) {
if (nir_src_is_const(alu->src[i].src)) {
return 0;
}
}
}
return 4;
}
/* R300 and R400 have just 32 vec4 constant register slots in fs.
* Therefore, while its possible we will be able to compact some of
* the constants later, we need to be extra careful with adding
* new constants anyway.
*/
static bool have_too_many_ubos(nir_shader *s, bool is_r500)
{
if (s->info.stage != MESA_SHADER_FRAGMENT)
return false;
if (is_r500)
return false;
nir_foreach_variable_with_modes(var, s, nir_var_mem_ubo) {
int ubo = var->data.driver_location;
assert (ubo == 0);
unsigned size = glsl_get_explicit_size(var->interface_type, false);
if (DIV_ROUND_UP(size, 16) > 32)
return true;
}
return false;
}
static bool
r300_should_vectorize_io(unsigned align, unsigned bit_size,
unsigned num_components, unsigned high_offset,
@ -157,7 +214,10 @@ r300_optimize_nir(struct nir_shader *s, struct pipe_screen *screen)
NIR_PASS(progress, s, nir_opt_shrink_stores, true);
NIR_PASS(progress, s, nir_opt_shrink_vectors, false);
NIR_PASS(progress, s, nir_opt_loop);
NIR_PASS(progress, s, nir_opt_vectorize, r300_should_vectorize_instr, NULL);
bool too_many_ubos = have_too_many_ubos(s, is_r500);
NIR_PASS(progress, s, nir_opt_vectorize, r300_should_vectorize_instr,
&too_many_ubos);
NIR_PASS(progress, s, nir_opt_undef);
if(!progress)
NIR_PASS(progress, s, nir_lower_undef_to_zero);