[Mesa-dev] [PATCH 092/133] nir: Add a pass to lower local variables to registers
Jason Ekstrand
jason at jlekstrand.net
Tue Jan 6 17:05:48 PST 2015
On Sun, Jan 4, 2015 at 7:52 PM, Connor Abbott <cwabbott0 at gmail.com> wrote:
>
>
> On Tue, Dec 16, 2014 at 1:11 AM, Jason Ekstrand <jason at jlekstrand.net>
> wrote:
>
>> ---
>> src/glsl/Makefile.sources | 1 +
>> src/glsl/nir/nir.h | 2 +
>> src/glsl/nir/nir_lower_locals_to_regs.c | 313
>> ++++++++++++++++++++++++++++++++
>> 3 files changed, 316 insertions(+)
>> create mode 100644 src/glsl/nir/nir_lower_locals_to_regs.c
>>
>> diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
>> index 1d3b049..6230f49 100644
>> --- a/src/glsl/Makefile.sources
>> +++ b/src/glsl/Makefile.sources
>> @@ -22,6 +22,7 @@ NIR_FILES = \
>> $(GLSL_SRCDIR)/nir/nir_intrinsics.h \
>> $(GLSL_SRCDIR)/nir/nir_live_variables.c \
>> $(GLSL_SRCDIR)/nir/nir_lower_atomics.c \
>> + $(GLSL_SRCDIR)/nir/nir_lower_locals_to_regs.c \
>> $(GLSL_SRCDIR)/nir/nir_lower_samplers.cpp \
>> $(GLSL_SRCDIR)/nir/nir_lower_system_values.c \
>> $(GLSL_SRCDIR)/nir/nir_lower_variables.c \
>> diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
>> index b3abfb9..7d7aec7 100644
>> --- a/src/glsl/nir/nir.h
>> +++ b/src/glsl/nir/nir.h
>> @@ -1358,6 +1358,8 @@ void nir_dump_cfg(nir_shader *shader, FILE *fp);
>>
>> void nir_split_var_copies(nir_shader *shader);
>>
>> +void nir_lower_locals_to_regs(nir_shader *shader);
>> +
>> void nir_lower_variables(nir_shader *shader);
>>
>> void nir_lower_variables_scalar(nir_shader *shader, bool lower_globals,
>> diff --git a/src/glsl/nir/nir_lower_locals_to_regs.c
>> b/src/glsl/nir/nir_lower_locals_to_regs.c
>> new file mode 100644
>> index 0000000..caf1c29
>> --- /dev/null
>> +++ b/src/glsl/nir/nir_lower_locals_to_regs.c
>> @@ -0,0 +1,313 @@
>> +/*
>> + * Copyright © 2014 Intel Corporation
>> + *
>> + * Permission is hereby granted, free of charge, to any person obtaining
>> a
>> + * copy of this software and associated documentation files (the
>> "Software"),
>> + * to deal in the Software without restriction, including without
>> limitation
>> + * the rights to use, copy, modify, merge, publish, distribute,
>> sublicense,
>> + * and/or sell copies of the Software, and to permit persons to whom the
>> + * Software is furnished to do so, subject to the following conditions:
>> + *
>> + * The above copyright notice and this permission notice (including the
>> next
>> + * paragraph) shall be included in all copies or substantial portions of
>> the
>> + * Software.
>> + *
>> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
>> EXPRESS OR
>> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
>> MERCHANTABILITY,
>> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
>> SHALL
>> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
>> OTHER
>> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
>> ARISING
>> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
>> DEALINGS
>> + * IN THE SOFTWARE.
>> + *
>> + * Authors:
>> + * Jason Ekstrand (jason at jlekstrand.net)
>> + *
>> + */
>> +
>> +#include "nir.h"
>> +
>> +struct locals_to_regs_state {
>> + void *mem_ctx;
>> + nir_function_impl *impl;
>> +
>> + /* A hash table mapping derefs to registers */
>> + struct hash_table *regs_table;
>> +};
>> +
>> +/* The following two functions implement a hash and equality check for
>> + * variable dreferences. When the hash or equality function encounters
>> an
>> + * array, it ignores the offset and whether it is direct or indirect
>> + * entirely.
>> + */
>> +static uint32_t
>> +hash_deref(const void *void_deref)
>> +{
>> + const nir_deref *deref = void_deref;
>> +
>> + uint32_t hash;
>> + if (deref->child) {
>> + hash = hash_deref(deref->child);
>> + } else {
>> + hash = 2166136261ul;
>> + }
>> +
>> + switch (deref->deref_type) {
>> + case nir_deref_type_var:
>> + hash ^= _mesa_hash_pointer(nir_deref_as_var(deref)->var);
>> + break;
>> + case nir_deref_type_array: {
>> + hash ^= 268435183;
>> + break;
>> + }
>> + case nir_deref_type_struct:
>> + hash ^= nir_deref_as_struct(deref)->index;
>> + break;
>> + }
>> +
>> + return hash * 0x01000193;
>> +}
>>
>
> Same comment here about using FNV-1a instead.
>
>
>> +
>> +static bool
>> +derefs_equal(const void *void_a, const void *void_b)
>> +{
>> + const nir_deref *a = void_a;
>> + const nir_deref *b = void_b;
>> +
>> + if (a->deref_type != b->deref_type)
>> + return false;
>> +
>> + switch (a->deref_type) {
>> + case nir_deref_type_var:
>> + if (nir_deref_as_var(a)->var != nir_deref_as_var(b)->var)
>> + return false;
>> + break;
>>
>
> Again, we could split this out of the loop since it's only going to be
> used once.
>
>
>> + case nir_deref_type_array:
>> + /* Do nothing. All array derefs are the same */
>> + break;
>> + case nir_deref_type_struct:
>> + if (nir_deref_as_struct(a)->index != nir_deref_as_struct(b)->index)
>> + return false;
>> + break;
>> + default:
>> + unreachable("Invalid dreference type");
>> + }
>> +
>> + assert((a->child == NULL) == (b->child == NULL));
>> + if (a->child)
>> + return derefs_equal(a->child, b->child);
>> + else
>> + return true;
>> +}
>>
>
> Same comment about using a for loop here.
>
Hashing and loopifying are done in 150/133
>
>
>> +
>> +static nir_register *
>> +get_reg_for_deref(nir_deref_var *deref, struct locals_to_regs_state
>> *state)
>> +{
>> + uint32_t hash = hash_deref(deref);
>> +
>> + struct hash_entry *entry = _mesa_hash_table_search(state->regs_table,
>> + hash, deref);
>> + if (entry)
>> + return entry->data;
>> +
>> + unsigned array_size = 1;
>> + nir_deref *tail = &deref->deref;
>> + while (tail->child) {
>> + if (tail->child->deref_type == nir_deref_type_array) {
>> + /* Multiply by the parent's type. */
>> + if (glsl_type_is_matrix(tail->type)) {
>> + array_size *= glsl_get_matrix_columns(tail->type);
>> + } else {
>> + assert(glsl_get_length(tail->type) > 0);
>> + array_size *= glsl_get_length(tail->type);
>> + }
>> + }
>> + tail = tail->child;
>> + }
>> +
>> + assert(glsl_type_is_vector(tail->type) ||
>> glsl_type_is_scalar(tail->type));
>> +
>> + nir_register *reg = nir_local_reg_create(state->impl);
>> + reg->num_components = glsl_get_vector_elements(tail->type);
>> + reg->num_array_elems = array_size > 1 ? array_size : 0;
>> +
>> + _mesa_hash_table_insert(state->regs_table, hash, deref, reg);
>> +
>> + return reg;
>> +}
>> +
>> +static nir_src
>> +get_deref_reg_src(nir_deref_var *deref, nir_instr *instr,
>> + struct locals_to_regs_state *state)
>> +{
>> + nir_src src;
>> +
>> + src.is_ssa = false;
>> + src.reg.reg = get_reg_for_deref(deref, state);
>> + src.reg.base_offset = 0;
>> + src.reg.indirect = NULL;
>> +
>> + nir_deref *tail = &deref->deref;
>> + while (tail->child != NULL) {
>> + const struct glsl_type *parent_type = tail->type;
>> + tail = tail->child;
>> +
>> + if (tail->deref_type != nir_deref_type_array)
>> + continue;
>> +
>> + nir_deref_array *deref_array = nir_deref_as_array(tail);
>> +
>> + src.reg.base_offset *= glsl_get_length(parent_type);
>> + src.reg.base_offset += deref_array->base_offset;
>> +
>> + if (src.reg.indirect) {
>>
>
> It doesn't matter too much, but since it's so easy I'd put "&&
> glsl_get_length(parent_type) != 1" here to save some CPU cycles.
>
>
>> + nir_load_const_instr *load_const =
>> + nir_load_const_instr_create(state->mem_ctx);
>> + load_const->num_components = 1;
>> + load_const->value.u[0] = glsl_get_length(parent_type);
>> + load_const->dest.is_ssa = true;
>> + nir_ssa_def_init(&load_const->instr, &load_const->dest.ssa, 1,
>> NULL);
>> + nir_instr_insert_before(instr, &load_const->instr);
>> +
>> + nir_alu_instr *mul = nir_alu_instr_create(state->mem_ctx,
>> nir_op_imul);
>> + mul->src[0].src = *src.reg.indirect;
>> + mul->src[1].src.is_ssa = true;
>> + mul->src[1].src.ssa = &load_const->dest.ssa;
>> + mul->dest.write_mask = 1;
>> + mul->dest.dest.is_ssa = true;
>> + nir_ssa_def_init(&mul->instr, &mul->dest.dest.ssa, 1, NULL);
>> + nir_instr_insert_before(instr, &mul->instr);
>> +
>> + src.reg.indirect->is_ssa = true;
>> + src.reg.indirect->ssa = &mul->dest.dest.ssa;
>> + }
>
> +
>> + if (deref_array->deref_array_type ==
>> nir_deref_array_type_indirect) {
>> + if (src.reg.indirect == NULL) {
>> + src.reg.indirect = ralloc(state->mem_ctx, nir_src);
>> + *src.reg.indirect = nir_src_copy(deref_array->indirect,
>> + state->mem_ctx);
>> + } else {
>> + nir_alu_instr *add = nir_alu_instr_create(state->mem_ctx,
>> + nir_op_iadd);
>> + add->src[0].src = *src.reg.indirect;
>> + add->src[1].src = nir_src_copy(deref_array->indirect,
>> + state->mem_ctx);
>> + add->dest.write_mask = 1;
>> + add->dest.dest.is_ssa = true;
>> + nir_ssa_def_init(&add->instr, &add->dest.dest.ssa, 1, NULL);
>> + nir_instr_insert_before(instr, &add->instr);
>> +
>> + src.reg.indirect->is_ssa = true;
>> + src.reg.indirect->ssa = &add->dest.dest.ssa;
>> + }
>> + }
>> + }
>> +
>> + return src;
>> +}
>> +
>> +static bool
>> +lower_locals_to_regs_block(nir_block *block, void *void_state)
>> +{
>> + struct locals_to_regs_state *state = void_state;
>> +
>> + nir_foreach_instr_safe(block, instr) {
>> + if (instr->type != nir_instr_type_intrinsic)
>> + continue;
>> +
>> + nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
>> +
>> + switch (intrin->intrinsic) {
>> + case nir_intrinsic_load_var_vec1:
>> + case nir_intrinsic_load_var_vec2:
>> + case nir_intrinsic_load_var_vec3:
>> + case nir_intrinsic_load_var_vec4: {
>> + if (intrin->variables[0]->var->data.mode != nir_var_local)
>> + continue;
>> +
>> + nir_alu_instr *mov = nir_alu_instr_create(state->mem_ctx,
>> nir_op_imov);
>> + mov->src[0].src = get_deref_reg_src(intrin->variables[0],
>> + &intrin->instr, state);
>> + unsigned num_components =
>> mov->src[0].src.reg.reg->num_components;
>> + mov->dest.write_mask = (1 << num_components) - 1;
>> + if (intrin->dest.is_ssa) {
>> + mov->dest.dest.is_ssa = true;
>> + nir_ssa_def_init(&mov->instr, &mov->dest.dest.ssa,
>> + num_components, NULL);
>> +
>> + nir_src new_src = {
>> + .is_ssa = true,
>> + .ssa = &mov->dest.dest.ssa,
>> + };
>> +
>> + nir_ssa_def_rewrite_uses(&intrin->dest.ssa, new_src,
>> + state->mem_ctx);
>> + } else {
>> + mov->dest.dest = nir_dest_copy(intrin->dest, state->mem_ctx);
>> + }
>> + nir_instr_insert_before(&intrin->instr, &mov->instr);
>> +
>> + nir_instr_remove(&intrin->instr);
>> + break;
>> + }
>> +
>> + case nir_intrinsic_store_var_vec1:
>> + case nir_intrinsic_store_var_vec2:
>> + case nir_intrinsic_store_var_vec3:
>> + case nir_intrinsic_store_var_vec4: {
>> + if (intrin->variables[0]->var->data.mode != nir_var_local)
>> + continue;
>> +
>> + nir_src reg_src = get_deref_reg_src(intrin->variables[0],
>> + &intrin->instr, state);
>> + unsigned num_components = reg_src.reg.reg->num_components;
>> +
>> + nir_alu_instr *mov = nir_alu_instr_create(state->mem_ctx,
>> nir_op_imov);
>> + mov->src[0].src = nir_src_copy(intrin->src[0], state->mem_ctx);
>> + mov->dest.write_mask = (1 << num_components) - 1;
>> + mov->dest.dest.is_ssa = false;
>> + mov->dest.dest.reg.reg = reg_src.reg.reg;
>> + mov->dest.dest.reg.base_offset = reg_src.reg.base_offset;
>> + mov->dest.dest.reg.indirect = reg_src.reg.indirect;
>> +
>> + nir_instr_insert_before(&intrin->instr, &mov->instr);
>> +
>> + nir_instr_remove(&intrin->instr);
>> + break;
>> + }
>> +
>> + case nir_intrinsic_copy_var:
>> + unreachable("There should be no copies whatsoever at this
>> point");
>> + break;
>>
>
> Are you sure about this? My impression is that lower_variables will lower
> copies involving things that aren't indirectly referenced, but if you have
> something like:
>
> foo[i] = ...
> bar[*] = foo[*];
> ... = bar[i];
>
> then the copy in the middle won't get lowered, unless there's something
> else I'm missing that will lower it.
>
Yeah, there may be something missing there. I have a pass lying around
somewhere that lowers all copies. Unfortunately, I've never actually seen
this happen in the wild so It's untested. I'll try and cook something up
that I think is reliable.
> If we always lowered these copies (ignoring that it hurts packing for vec4
> backends), then we wouldn't need wildcards in the first place...
>
Yes, but I have an evil plot to do copy propagation of variables that
properly handles arrays. >:-]
>
>
>> +
>> + default:
>> + continue;
>> + }
>> + }
>> +
>> + return true;
>> +}
>> +
>> +static void
>> +nir_lower_locals_to_regs_impl(nir_function_impl *impl)
>> +{
>> + struct locals_to_regs_state state;
>> +
>> + state.mem_ctx = ralloc_parent(impl);
>> + state.impl = impl;
>> + state.regs_table = _mesa_hash_table_create(NULL, derefs_equal);
>> +
>> + nir_foreach_block(impl, lower_locals_to_regs_block, &state);
>> +
>> + _mesa_hash_table_destroy(state.regs_table, NULL);
>> +}
>> +
>> +void
>> +nir_lower_locals_to_regs(nir_shader *shader)
>> +{
>> + nir_foreach_overload(shader, overload) {
>> + if (overload->impl)
>> + nir_lower_locals_to_regs_impl(overload->impl);
>> + }
>> +}
>> --
>> 2.2.0
>>
>> _______________________________________________
>> mesa-dev mailing list
>> mesa-dev at lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/mesa-dev
>>
>
>
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