[Mesa-dev] [PATCH 1/3] nir: add new linking opt nir_move_out_const_to_consumer()
Timothy Arceri
tarceri at itsqueeze.com
Wed Nov 7 08:40:43 UTC 2018
On 7/11/18 7:40 pm, Samuel Pitoiset wrote:
> IIRC, I wrote a pass similar to this one a while ago, but never finished
> it.
>
> I don't really like the helper name though, how about
> nir_link_immediate_varyings()? or nir_link_constant_varyings()?
Sure. Happy to change the name. I''ll go with
nir_link_constant_varyings() unless there are any other objections.
>
> On 11/7/18 5:20 AM, Timothy Arceri wrote:
>> This pass moves constant outputs to the consuming shader stage
>> where possible.
>> ---
>> src/compiler/nir/nir.h | 2 +
>> src/compiler/nir/nir_linking_helpers.c | 104 ++++++++++++++++++++++
>> src/mesa/state_tracker/st_glsl_to_nir.cpp | 2 +-
>> 3 files changed, 107 insertions(+), 1 deletion(-)
>>
>> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
>> index a0ae9a4430e..0b8c8578953 100644
>> --- a/src/compiler/nir/nir.h
>> +++ b/src/compiler/nir/nir.h
>> @@ -2800,6 +2800,8 @@ bool nir_remove_unused_io_vars(nir_shader
>> *shader, struct exec_list *var_list,
>> void nir_compact_varyings(nir_shader *producer, nir_shader *consumer,
>> bool default_to_smooth_interp);
>> void nir_link_xfb_varyings(nir_shader *producer, nir_shader *consumer);
>> +bool nir_move_out_const_to_consumer(nir_shader *producer,
>> + nir_shader *consumer);
>> typedef enum {
>> /* If set, this forces all non-flat fragment shader inputs to be
>> diff --git a/src/compiler/nir/nir_linking_helpers.c
>> b/src/compiler/nir/nir_linking_helpers.c
>> index de6f2481def..19905e2ad5d 100644
>> --- a/src/compiler/nir/nir_linking_helpers.c
>> +++ b/src/compiler/nir/nir_linking_helpers.c
>> @@ -22,6 +22,7 @@
>> */
>> #include "nir.h"
>> +#include "nir_builder.h"
>> #include "util/set.h"
>> #include "util/hash_table.h"
>> @@ -556,3 +557,106 @@ nir_link_xfb_varyings(nir_shader *producer,
>> nir_shader *consumer)
>> }
>> }
>> }
>> +
>> +static bool
>> +try_replace_constant_input(nir_shader *shader,
>> + nir_intrinsic_instr *store_intr)
>> +{
>> + nir_variable *out_var =
>> +
>> nir_deref_instr_get_variable(nir_src_as_deref(store_intr->src[0]));
>> +
>> + if (out_var->data.mode != nir_var_shader_out)
>> + return false;
>> +
>> + /* Skip types that require more complex handling.
>> + * TODO: add support for these types.
>> + */
>> + if (glsl_type_is_array(out_var->type) ||
>> + glsl_type_is_dual_slot(out_var->type) ||
>> + glsl_type_is_matrix(out_var->type) ||
>> + glsl_type_is_struct(out_var->type))
>> + return false;
>> +
>> + if (out_var->data.location < VARYING_SLOT_VAR0 ||
>> + out_var->data.location - VARYING_SLOT_VAR0 >= MAX_VARYING)
>> + 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 != out_var->data.location ||
>> + in_var->data.location_frac != out_var->data.location_frac)
>> + continue;
>> +
>> + b.cursor = nir_before_instr(instr);
>> +
>> + nir_load_const_instr *out_const =
>> +
>> nir_instr_as_load_const(store_intr->src[1].ssa->parent_instr);
>> +
>> + /* Add new const to replace the input */
>> + nir_ssa_def *nconst = nir_build_imm(&b,
>> store_intr->num_components,
>> + intr->dest.ssa.bit_size,
>> + out_const->value);
>> +
>> + nir_ssa_def_rewrite_uses(&intr->dest.ssa,
>> nir_src_for_ssa(nconst));
>> +
>> + progress = true;
>> + }
>> + }
>> +
>> + return progress;
>> +}
>> +
>> +bool
>> +nir_move_out_const_to_consumer(nir_shader *producer, nir_shader
>> *consumer)
>> +{
>> + /* TODO: Add support for more shader stage combinations */
>> + if (consumer->info.stage != MESA_SHADER_FRAGMENT ||
>> + (producer->info.stage != MESA_SHADER_VERTEX &&
>> + producer->info.stage != MESA_SHADER_TESS_EVAL))
>> + return false;
>> +
>> + bool progress = false;
>> +
>> + nir_function_impl *impl = nir_shader_get_entrypoint(producer);
>> +
>> + /* 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.
>> + */
>> + nir_block *last_block = nir_impl_last_block(impl);
>> + nir_foreach_instr_reverse(instr, last_block) {
>> + if (instr->type != nir_instr_type_intrinsic)
>> + continue;
>> +
>> + nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
>> +
>> + if (intr->intrinsic != nir_intrinsic_store_deref)
>> + continue;
>> +
>> + if (intr->src[1].ssa->parent_instr->type !=
>> nir_instr_type_load_const) {
>> + continue;
>> + }
>> +
>> + progress |= try_replace_constant_input(consumer, intr);
>> + }
>> +
>> + return progress;
>> +}
>> diff --git a/src/mesa/state_tracker/st_glsl_to_nir.cpp
>> b/src/mesa/state_tracker/st_glsl_to_nir.cpp
>> index dcf8c2b638e..9141acbc4df 100644
>> --- a/src/mesa/state_tracker/st_glsl_to_nir.cpp
>> +++ b/src/mesa/state_tracker/st_glsl_to_nir.cpp
>> @@ -757,7 +757,7 @@ st_link_nir(struct gl_context *ctx,
>> */
>> if (!prev_shader->sh.LinkedTransformFeedback)
>>
>> nir_compact_varyings(shader_program->_LinkedShaders[prev]->Program->nir,
>> - nir, ctx->API != API_OPENGL_COMPAT);
>> + nir, ctx->API != API_OPENGL_COMPAT);
>> }
>> prev = i;
>> }
>>
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