[Mesa-dev] [PATCH 4/4] nir: link time opt duplicate varyings
Timothy Arceri
tarceri at itsqueeze.com
Sat Dec 15 02:16:03 UTC 2018
On 15/12/18 7:32 am, Marek Olšák wrote:
> For patches 1-3:
>
> Reviewed-by: Marek Olšák <marek.olsak at amd.com <mailto:marek.olsak at amd.com>>
>
Thanks!
> I'm not so knowledgeable to be able to comment on patch 4.
>
> Does it also merge varyings such as (x,y,undef,undef) and
> (x,undef,undef,w)? There is a game which outputs (x,y,z,undef) and
> (x,y,undef,undef) where the vertex shader is a SSO.
No. All of the link-time optimisations in NIR are currently only applied
at actual link-time. I've often thought about adding a way to apply
these to SSO shaders but this is unlikely something I will end up
working on since our main focus these days is on Vulkan and there we
always link the entire pipeline so its not an issue.
>
> Marek
>
> On Mon, Dec 10, 2018 at 11:28 PM Timothy Arceri <tarceri at itsqueeze.com
> <mailto:tarceri at itsqueeze.com>> wrote:
>
> If we are outputting the same value to more than one output
> component rewrite the inputs to read from a single component.
>
> This will allow the duplicate varying components to be optimised
> away by the existing opts.
>
> shader-db results i965 (SKL):
>
> total instructions in shared programs: 12869230 -> 12860886 (-0.06%)
> instructions in affected programs: 322601 -> 314257 (-2.59%)
> helped: 3080
> HURT: 8
>
> total cycles in shared programs: 317792574 -> 317730593 (-0.02%)
> cycles in affected programs: 2584925 -> 2522944 (-2.40%)
> helped: 2975
> HURT: 477
>
> shader-db results radeonsi (VEGA):
>
> Totals from affected shaders:
> SGPRS: 30960 -> 31056 (0.31 %)
> VGPRS: 17052 -> 16672 (-2.23 %)
> Spilled SGPRs: 184 -> 167 (-9.24 %)
> Spilled VGPRs: 0 -> 0 (0.00 %)
> Private memory VGPRs: 0 -> 0 (0.00 %)
> Scratch size: 0 -> 0 (0.00 %) dwords per thread
> Code Size: 562532 -> 549404 (-2.33 %) bytes
> LDS: 0 -> 0 (0.00 %) blocks
> Max Waves: 6011 -> 6110 (1.65 %)
> Wait states: 0 -> 0 (0.00 %)
>
> vkpipeline-db results RADV (VEGA):
>
> Totals from affected shaders:
> SGPRS: 14880 -> 15080 (1.34 %)
> VGPRS: 10872 -> 10888 (0.15 %)
> Spilled SGPRs: 0 -> 0 (0.00 %)
> Spilled VGPRs: 0 -> 0 (0.00 %)
> Private memory VGPRs: 0 -> 0 (0.00 %)
> Scratch size: 0 -> 0 (0.00 %) dwords per thread
> Code Size: 674016 -> 668396 (-0.83 %) bytes
> LDS: 0 -> 0 (0.00 %) blocks
> Max Waves: 2708 -> 2704 (-0.15 %)
> Wait states: 0 -> 0 (0.00 %
> ---
> src/compiler/nir/nir_linking_helpers.c | 95 ++++++++++++++++++++++++++
> 1 file changed, 95 insertions(+)
>
> diff --git a/src/compiler/nir/nir_linking_helpers.c
> b/src/compiler/nir/nir_linking_helpers.c
> index 37644d339f..bdfa7b8c4d 100644
> --- a/src/compiler/nir/nir_linking_helpers.c
> +++ b/src/compiler/nir/nir_linking_helpers.c
> @@ -700,6 +700,27 @@ nir_link_xfb_varyings(nir_shader *producer,
> nir_shader *consumer)
> }
> }
>
> +static nir_variable *
> +get_matching_input_var(nir_shader *consumer, nir_variable *out_var)
> +{
> + nir_variable *input_var = NULL;
> + nir_foreach_variable(var, &consumer->inputs) {
> + if (var->data.location >= VARYING_SLOT_VAR0 &&
> + var->data.location - VARYING_SLOT_VAR0 < MAX_VARYING) {
> +
> + if (var->data.location == out_var->data.location &&
> + var->data.location_frac == out_var->data.location_frac &&
> + var->data.interpolation == out_var->data.interpolation &&
> + get_interp_loc(var) == get_interp_loc(out_var)) {
> + input_var = var;
> + break;
> + }
> + }
> + }
> +
> + return input_var;
> +}
> +
> static bool
> can_replace_varying(nir_variable *out_var, nir_intrinsic_instr
> *store_intr)
> {
> @@ -782,6 +803,57 @@ try_replace_constant_input(nir_shader *shader,
> return progress;
> }
>
> +static bool
> +try_replace_duplicate_input(nir_shader *shader, nir_variable
> *input_var,
> + nir_intrinsic_instr *dup_store_intr)
> +{
> + assert(input_var);
> +
> + nir_variable *dup_out_var =
> +
> nir_deref_instr_get_variable(nir_src_as_deref(dup_store_intr->src[0]));
> +
> + if (!can_replace_varying(dup_out_var, dup_store_intr))
> + return false;
> +
> + nir_function_impl *impl = nir_shader_get_entrypoint(shader);
> +
> + nir_builder b;
> + nir_builder_init(&b, impl);
> +
> + bool progress = false;
> + nir_foreach_block(block, impl) {
> + nir_foreach_instr(instr, block) {
> + if (instr->type != nir_instr_type_intrinsic)
> + continue;
> +
> + nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
> + if (intr->intrinsic != nir_intrinsic_load_deref)
> + continue;
> +
> + nir_variable *in_var =
> +
> nir_deref_instr_get_variable(nir_src_as_deref(intr->src[0]));
> +
> + if (in_var->data.mode != nir_var_shader_in)
> + continue;
> +
> + if (in_var->data.location != dup_out_var->data.location ||
> + in_var->data.location_frac !=
> dup_out_var->data.location_frac ||
> + in_var->data.interpolation !=
> input_var->data.interpolation ||
> + get_interp_loc(in_var) != get_interp_loc(input_var))
> + continue;
> +
> + b.cursor = nir_before_instr(instr);
> +
> + nir_ssa_def *load = nir_load_var(&b, input_var);
> + nir_ssa_def_rewrite_uses(&intr->dest.ssa,
> nir_src_for_ssa(load));
> +
> + progress = true;
> + }
> + }
> +
> + return progress;
> +}
> +
> bool
> nir_link_opt_varyings(nir_shader *producer, nir_shader *consumer)
> {
> @@ -795,6 +867,10 @@ nir_link_opt_varyings(nir_shader *producer,
> nir_shader *consumer)
>
> nir_function_impl *impl = nir_shader_get_entrypoint(producer);
>
> + struct hash_table *varying_values =
> + _mesa_hash_table_create(NULL, _mesa_hash_pointer,
> + _mesa_key_pointer_equal);
> +
> /* If we find a store in the last block of the producer we can
> be sure this
> * is the only possible value for this output.
> */
> @@ -809,11 +885,30 @@ nir_link_opt_varyings(nir_shader *producer,
> nir_shader *consumer)
> continue;
>
> if (intr->src[1].ssa->parent_instr->type !=
> nir_instr_type_load_const) {
> + struct hash_entry *entry =
> + _mesa_hash_table_search(varying_values,
> intr->src[1].ssa);
> + if (entry) {
> + progress |=
> + try_replace_duplicate_input(consumer,
> + (nir_variable *)
> entry->data,
> + intr);
> + } else {
> + nir_variable *out_var =
> +
> nir_deref_instr_get_variable(nir_src_as_deref(intr->src[0]));
> + nir_variable *in_var = get_matching_input_var(consumer,
> out_var);
> + if (in_var && can_replace_varying(out_var, intr)) {
> + _mesa_hash_table_insert(varying_values,
> intr->src[1].ssa,
> + in_var);
> + }
> + }
> +
> continue;
> }
>
> progress |= try_replace_constant_input(consumer, intr);
> }
>
> + _mesa_hash_table_destroy(varying_values, NULL);
> +
> return progress;
> }
> --
> 2.19.2
>
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