[Mesa-dev] [PATCH 091/133] nir: Add a pass to lower local variable accesses to SSA values
Jason Ekstrand
jason at jlekstrand.net
Wed Dec 17 21:35:12 PST 2014
On Wed, Dec 17, 2014 at 8:42 PM, Connor Abbott <cwabbott0 at gmail.com> wrote:
>
> On Wed, Dec 17, 2014 at 10:50 PM, Jason Ekstrand <jason at jlekstrand.net>
> wrote:
> >
> >
> > On Wed, Dec 17, 2014 at 7:13 PM, Connor Abbott <cwabbott0 at gmail.com>
> wrote:
> >>
> >> On Tue, Dec 16, 2014 at 1:11 AM, Jason Ekstrand <jason at jlekstrand.net>
> >> wrote:
> >> > This pass analizes all of the load/store operations and, when a
> variable
> >> > is
> >> > never aliased (potentially used by an indirect operation), it is
> lowered
> >> > directly to an SSA value. This pass translates to SSA directly and
> does
> >> > not require any fixup by the original to-SSA pass.
> >> > ---
> >> > src/glsl/Makefile.sources | 1 +
> >> > src/glsl/nir/nir.h | 2 +
> >> > src/glsl/nir/nir_lower_variables.c | 1071
> >> > ++++++++++++++++++++++++++++++++++++
> >> > 3 files changed, 1074 insertions(+)
> >> > create mode 100644 src/glsl/nir/nir_lower_variables.c
> >> >
> >> > diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
> >> > index 84245bc..1d3b049 100644
> >> > --- a/src/glsl/Makefile.sources
> >> > +++ b/src/glsl/Makefile.sources
> >> > @@ -24,6 +24,7 @@ NIR_FILES = \
> >> > $(GLSL_SRCDIR)/nir/nir_lower_atomics.c \
> >> > $(GLSL_SRCDIR)/nir/nir_lower_samplers.cpp \
> >> > $(GLSL_SRCDIR)/nir/nir_lower_system_values.c \
> >> > + $(GLSL_SRCDIR)/nir/nir_lower_variables.c \
> >> > $(GLSL_SRCDIR)/nir/nir_lower_variables_scalar.c \
> >> > $(GLSL_SRCDIR)/nir/nir_lower_vec_to_movs.c \
> >> > $(GLSL_SRCDIR)/nir/nir_metadata.c \
> >> > diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
> >> > index 86cda07..b3abfb9 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_variables(nir_shader *shader);
> >> > +
> >> > void nir_lower_variables_scalar(nir_shader *shader, bool
> lower_globals,
> >> > bool lower_io, bool add_names,
> >> > bool native_integers);
> >> > diff --git a/src/glsl/nir/nir_lower_variables.c
> >> > b/src/glsl/nir/nir_lower_variables.c
> >> > new file mode 100644
> >> > index 0000000..052b021
> >> > --- /dev/null
> >> > +++ b/src/glsl/nir/nir_lower_variables.c
> >> > @@ -0,0 +1,1071 @@
> >> > +/*
> >> > + * 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 deref_node {
> >> > + struct deref_node *parent;
> >> > + const struct glsl_type *type;
> >> > +
> >> > + bool lower_to_ssa;
> >> > +
> >> > + struct set *loads;
> >> > + struct set *stores;
> >> > + struct set *copies;
> >> > +
> >> > + nir_ssa_def **def_stack;
> >> > + nir_ssa_def **def_stack_tail;
> >> > +
> >> > + struct deref_node *wildcard;
> >> > + struct deref_node *indirect;
> >> > + struct deref_node *children[0];
> >> > +};
> >>
> >> I think this should be a typedef'd struct, that's the way everything
> >> else is in NIR, including all the other pass-specific structures (all
> >> bikesheds aside).
> >
> >
> > Sure, and I think I certainly will if it gets moved to a header file. In
> > general, I haven't been typdef'ing pass-specific stuff. Maybe you were,
> but
> > I haven't.
> >
> >>
> >>
> >> > +
> >> > +struct lower_variables_state {
> >> > + void *mem_ctx;
> >> > + void *dead_ctx;
> >> > + nir_function_impl *impl;
> >> > +
> >> > + /* A hash table mapping variables to deref_node data */
> >> > + struct hash_table *deref_var_nodes;
> >> > + /* A hash table mapping dereference leaves to deref_node data */
> >> > + struct hash_table *deref_leaves;
> >> > +
> >> > + /* A hash table mapping phi nodes to deref_state data */
> >> > + struct hash_table *phi_table;
> >> > +};
> >> > +
> >> > +/* The following two functions implement a hash and equality check
> for
> >> > + * variable dreferences. When the hash or equality function
> encounters
> >> > an
> >> > + * array, all indirects are treated as equal and are never equal to a
> >> > + * direct dereference or a wildcard.
> >> > + */
> >> > +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: {
> >> > + nir_deref_array *array = nir_deref_as_array(deref);
> >> > + hash += 268435183 * array->deref_array_type;
> >> > + if (array->deref_array_type == nir_deref_array_type_direct)
> >> > + hash ^= array->base_offset; /* Some prime */
> >> > + break;
> >> > + }
> >> > + case nir_deref_type_struct:
> >> > + hash ^= nir_deref_as_struct(deref)->index;
> >> > + break;
> >> > + }
> >> > +
> >> > + return hash * 0x01000193;
> >> > +}
> >>
> >> I seem to recall you saying these magic numbers aren't really
> >> necessary. If they are, can we document why you chose them and what
> >> they're doing?
> >
> >
> > They're some primes I grabbed off the internet. Hashing is magic. I
> don't
> > claim that this hash is good. Just that it's a hash.
> >
> >>
> >>
> >> > +
> >> > +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;
> >> > + case nir_deref_type_array: {
> >> > + nir_deref_array *a_arr = nir_deref_as_array(a);
> >> > + nir_deref_array *b_arr = nir_deref_as_array(b);
> >> > +
> >> > + if (a_arr->deref_array_type != b_arr->deref_array_type)
> >> > + return false;
> >> > +
> >> > + if (a_arr->deref_array_type == nir_deref_array_type_direct &&
> >> > + a_arr->base_offset != b_arr->base_offset)
> >> > + return false;
> >> > + 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;
> >> > +}
> >> > +
> >> > +static int
> >> > +type_get_length(const struct glsl_type *type)
> >> > +{
> >> > + switch (glsl_get_base_type(type)) {
> >> > + case GLSL_TYPE_STRUCT:
> >> > + case GLSL_TYPE_ARRAY:
> >> > + return glsl_get_length(type);
> >> > + case GLSL_TYPE_FLOAT:
> >> > + case GLSL_TYPE_INT:
> >> > + case GLSL_TYPE_UINT:
> >> > + case GLSL_TYPE_BOOL:
> >> > + if (glsl_type_is_matrix(type))
> >> > + return glsl_get_matrix_columns(type);
> >> > + else
> >> > + return glsl_get_vector_elements(type);
> >> > + default:
> >> > + unreachable("Invalid deref base type");
> >> > + }
> >> > +}
> >> > +
> >> > +static struct deref_node *
> >> > +deref_node_create(struct deref_node *parent,
> >> > + const struct glsl_type *type, void *mem_ctx)
> >> > +{
> >> > + size_t size = sizeof(struct deref_node) +
> >> > + type_get_length(type) * sizeof(struct deref_node *);
> >> > +
> >> > + struct deref_node *node = rzalloc_size(mem_ctx, size);
> >> > + node->type = type;
> >> > + node->parent = parent;
> >> > +
> >> > + return node;
> >> > +}
> >> > +
> >> > +static struct deref_node *
> >> > +get_deref_node(nir_deref_var *deref, bool add_to_leaves,
> >> > + struct lower_variables_state *state)
> >> > +{
> >> > + bool is_leaf = true;
> >> > + struct deref_node *parent = NULL;
> >> > + nir_deref *tail = &deref->deref;
> >> > + while (tail) {
> >> > + struct deref_node *node;
> >> > +
> >> > + switch (tail->deref_type) {
> >> > + case nir_deref_type_var: {
> >> > + assert(tail == &deref->deref);
> >> > + assert(parent == NULL);
> >> > +
> >> > + uint32_t var_hash = _mesa_hash_pointer(deref->var);
> >> > + struct hash_entry *entry =
> >> > + _mesa_hash_table_search(state->deref_var_nodes,
> >> > + var_hash, deref->var);
> >> > + if (entry) {
> >> > + node = entry->data;
> >> > + } else {
> >> > + node = deref_node_create(NULL, tail->type,
> >> > state->dead_ctx);
> >> > + _mesa_hash_table_insert(state->deref_var_nodes,
> >> > + var_hash, deref->var, node);
> >> > + }
> >> > + break;
> >> > + }
> >> > +
> >> > + case nir_deref_type_struct: {
> >> > + assert(parent != NULL);
> >> > +
> >> > + nir_deref_struct *deref_struct = nir_deref_as_struct(tail);
> >> > + assert(deref_struct->index < type_get_length(parent->type));
> >> > + if (parent->children[deref_struct->index]) {
> >> > + node = parent->children[deref_struct->index];
> >> > + } else {
> >> > + node = deref_node_create(parent, tail->type,
> >> > state->dead_ctx);
> >> > + parent->children[deref_struct->index] = node;
> >> > + }
> >> > + break;
> >> > + }
> >> > +
> >> > + case nir_deref_type_array: {
> >> > + assert(parent != NULL);
> >> > +
> >> > + nir_deref_array *arr = nir_deref_as_array(tail);
> >> > + switch (arr->deref_array_type) {
> >> > + case nir_deref_array_type_direct:
> >> > + if (arr->base_offset >= type_get_length(parent->type)) {
> >> > + /* This is possible if a loop unrolls and generates an
> >> > + * out-of-bounds offset. We need to handle this at
> >> > least
> >> > + * somewhat gracefully.
> >> > + */
> >> > + return NULL;
> >> > + } else if (parent->children[arr->base_offset]) {
> >> > + node = parent->children[arr->base_offset];
> >> > + } else {
> >> > + node = deref_node_create(parent, tail->type,
> >> > state->dead_ctx);
> >> > + parent->children[arr->base_offset] = node;
> >> > + }
> >> > + break;
> >> > + case nir_deref_array_type_indirect:
> >> > + if (parent->indirect) {
> >> > + node = parent->indirect;
> >> > + } else {
> >> > + node = deref_node_create(parent, tail->type,
> >> > state->dead_ctx);
> >> > + parent->indirect = node;
> >> > + }
> >> > + is_leaf = false;
> >>
> >> Maybe I'm not understanding something, but I don't think how you're
> >> setting is_leaf makes sense. For example, if I have
> >>
> >> vec4 foo[10];
> >>
> >> and I have a dereference like foo[i], then that sounds like it should
> >> be a leaf dereference (since it's not dereferencing a composite type
> >> like a struct or array). But here you'd set is_leaf to false in that
> >> case. I also see nothing that would set is_leaf to false if I just
> >> dereference foo by itself. On second thought, by that definition all
> >> of our derefs should be leaf dereferences, so maybe is_leaf is
> >> supposed to mean something else?
>
> You didn't respond here. Can you explain what is_leaf is supposed to be
> doing?
>
Looking at it again, it is, as you said below "entirely direct". is_leaf
is a bad name. I should change that and comment it better.
>
> >>
> >> > + break;
> >> > + case nir_deref_array_type_wildcard:
> >> > + if (parent->wildcard) {
> >> > + node = parent->wildcard;
> >> > + } else {
> >> > + node = deref_node_create(parent, tail->type,
> >> > state->dead_ctx);
> >> > + parent->wildcard = node;
> >> > + }
> >> > + is_leaf = false;
> >> > + break;
> >> > + default:
> >> > + unreachable("Invalid array deref type");
> >> > + }
> >> > + break;
> >> > + }
> >> > + default:
> >> > + unreachable("Invalid deref type");
> >> > + }
> >> > +
> >> > + parent = node;
> >> > + tail = tail->child;
> >> > + }
> >> > +
> >> > + assert(parent);
> >> > +
> >> > + if (is_leaf && add_to_leaves)
> >> > + _mesa_hash_table_insert(state->deref_leaves,
> >> > + hash_deref(deref), deref, parent);
> >> > +
> >> > + return parent;
> >> > +}
> >> > +
> >> > +static void
> >> > +register_load_instr(nir_intrinsic_instr *load_instr, bool
> create_node,
> >> > + struct lower_variables_state *state)
> >> > +{
> >> > + struct deref_node *node = get_deref_node(load_instr->variables[0],
> >> > + create_node, state);
> >> > + if (node == NULL)
> >> > + return;
> >> > +
> >> > + if (node->loads == NULL)
> >> > + node->loads = _mesa_set_create(state->dead_ctx,
> >> > + _mesa_key_pointer_equal);
> >> > +
> >> > + _mesa_set_add(node->loads, _mesa_hash_pointer(load_instr),
> >> > load_instr);
> >> > +}
> >> > +
> >> > +static void
> >> > +register_store_instr(nir_intrinsic_instr *store_instr, bool
> >> > create_node,
> >> > + struct lower_variables_state *state)
> >> > +{
> >> > + struct deref_node *node =
> get_deref_node(store_instr->variables[0],
> >> > + create_node, state);
> >> > + if (node == NULL)
> >> > + return;
> >> > +
> >> > + if (node->stores == NULL)
> >> > + node->stores = _mesa_set_create(state->dead_ctx,
> >> > + _mesa_key_pointer_equal);
> >> > +
> >> > + _mesa_set_add(node->stores, _mesa_hash_pointer(store_instr),
> >> > store_instr);
> >> > +}
> >> > +
> >> > +static void
> >> > +register_copy_instr(nir_intrinsic_instr *copy_instr, bool
> create_node,
> >> > + struct lower_variables_state *state)
> >> > +{
> >> > + for (unsigned idx = 0; idx < 2; idx++) {
> >> > + struct deref_node *node =
> >> > get_deref_node(copy_instr->variables[idx],
> >> > + create_node, state);
> >> > + if (node == NULL)
> >> > + continue;
> >> > +
> >> > + if (node->copies == NULL)
> >> > + node->copies = _mesa_set_create(state->dead_ctx,
> >> > + _mesa_key_pointer_equal);
> >> > +
> >> > + _mesa_set_add(node->copies, _mesa_hash_pointer(copy_instr),
> >> > copy_instr);
> >> > + }
> >> > +}
> >> > +
> >> > +static bool
> >> > +foreach_deref_node_worker(struct deref_node *node, nir_deref *deref,
> >> > + bool (* cb)(struct deref_node *node,
> >> > + struct lower_variables_state
> >> > *state),
> >> > + struct lower_variables_state *state)
> >> > +{
> >> > + if (deref->child == NULL) {
> >> > + return cb(node, state);
> >> > + } else {
> >> > + switch (deref->child->deref_type) {
> >> > + case nir_deref_type_array: {
> >> > + nir_deref_array *arr = nir_deref_as_array(deref->child);
> >> > + assert(arr->deref_array_type ==
> nir_deref_array_type_direct);
> >> > + if (node->children[arr->base_offset] &&
> >> > +
> >> > !foreach_deref_node_worker(node->children[arr->base_offset],
> >> > + deref->child, cb, state))
> >> > + return false;
> >> > +
> >> > + if (node->wildcard &&
> >> > + !foreach_deref_node_worker(node->wildcard,
> >> > + deref->child, cb, state))
> >> > + return false;
> >> > +
> >> > + return true;
> >> > + }
> >> > +
> >> > + case nir_deref_type_struct: {
> >> > + nir_deref_struct *str = nir_deref_as_struct(deref->child);
> >> > + return foreach_deref_node_worker(node->children[str->index],
> >> > + deref->child, cb, state);
> >> > + }
> >> > +
> >> > + default:
> >> > + unreachable("Invalid deref child type");
> >> > + }
> >> > + }
> >> > +}
> >> > +
> >> > +static bool
> >> > +foreach_deref_node_match(nir_deref_var *deref,
> >> > + bool (* cb)(struct deref_node *node,
> >> > + struct lower_variables_state
> >> > *state),
> >> > + struct lower_variables_state *state)
> >> > +{
> >> > + nir_deref_var var_deref = *deref;
> >> > + var_deref.deref.child = NULL;
> >> > + struct deref_node *node = get_deref_node(&var_deref, false,
> state);
> >> > +
> >> > + if (node == NULL)
> >> > + return false;
> >> > +
> >> > + return foreach_deref_node_worker(node, &deref->deref, cb, state);
> >> > +}
> >>
> >> Hmm, it seems we never use this function... and even if we did,
> >> get_deref_node() seems to provide basically the same functionality.
> >> Remove them?
> >
> >
> > We do use it.
>
> Where? And why can't you use get_node_deref() instead? If this fn is
> necessary, we should still get rid of the recursion and calling a
> callback by just passing back the deref_node * value and returning
> NULL instead of false it it doesn't exist. Also, foreach_* is a pretty
> bad name since it's job seems to be to return something, i.e. the
> deref_node pointer.
>
Down below. I pointed it out. What this function does is not entirely
obvious. Given a fully-qualified deref, it iterates over every deref and
calls the callback on everything that matches. For example a[1].bar[3].baz
will match all of the following:
a[1].bar[3].baz
a[1].bar[*].baz
a[*].bar[3].baz
a[*].bar[*].baz
We use this to lower all of the above var_copy intrinsics to actual
load/store intrinsics.
>
> >
> >>
> >>
> >> > +
> >> > +/* This question can only be asked about leaves. Searching down the
> >> > tree
> >> > + * is much harder than searching up.
> >> > + */
> >> > +static bool
> >> > +deref_may_be_aliased_node(struct deref_node *node, nir_deref *deref,
> >> > + struct lower_variables_state *state)
> >> > +{
> >> > + if (deref->child == NULL) {
> >> > + return false;
> >> > + } else {
> >> > + switch (deref->child->deref_type) {
> >> > + case nir_deref_type_array: {
> >> > + nir_deref_array *arr = nir_deref_as_array(deref->child);
> >> > + if (arr->deref_array_type == nir_deref_array_type_indirect)
> >> > + return true;
> >> > +
> >> > + assert(arr->deref_array_type ==
> nir_deref_array_type_direct);
> >>
> >> Why is this assert here? You're handling the wildcard case a few lines
> >> down.
> >
> >
> > The assert is here because you can only ask the "is this aliased"
> question
> > (at the moment) about an entirely direct reference. The stuff below is
> for
> > if there is a wildcard reference of this somewhere.
>
> Ok, so by "leaf" you mean "entirely direct reference"? And why,
> exactly, can't you answer this question? I thought we were using this
> to figure out if we could lower the variables to SSA, and the rule
> there is just "if there are no indirect dereferences, then we're
> fine"?
>
Yes, but in order to ask the question "are there any indirects to this" we
need to know what we're talking about. It's very clear what "are there any
indirects to a[1].foo[3].bar?" but "are there any indirects to
a[*].foo[4].bar?" is a much harder question and it's not at all clear that
it's even useful to ask that question.
>
> >
> >>
> >>
> >> > +
> >> > + if (node->children[arr->base_offset] &&
> >> > +
> >> > deref_may_be_aliased_node(node->children[arr->base_offset],
> >> > + deref->child, state))
> >> > + return true;
> >> > +
> >> > + if (node->wildcard &&
> >> > + deref_may_be_aliased_node(node->wildcard, deref->child,
> >> > state))
> >> > + return true;
> >> > +
> >> > + return false;
> >> > + }
> >> > +
> >> > + case nir_deref_type_struct: {
> >> > + nir_deref_struct *str = nir_deref_as_struct(deref->child);
> >> > + if (node->children[str->index]) {
> >> > + return
> >> > deref_may_be_aliased_node(node->children[str->index],
> >> > + deref->child, state);
> >> > + } else {
> >> > + return false;
> >> > + }
> >> > + }
> >> > +
> >> > + default:
> >> > + unreachable("Invalid nir_deref child type");
> >> > + }
> >> > + }
> >> > +}
> >> > +
> >> > +static bool
> >> > +deref_may_be_aliased(nir_deref_var *deref,
> >> > + struct lower_variables_state *state)
> >> > +{
> >> > + nir_deref_var var_deref = *deref;
> >> > + var_deref.deref.child = NULL;
> >> > + struct deref_node *node = get_deref_node(&var_deref, false,
> state);
> >>
> >> Instead of doing all these shenanigans, can we just look up the hash
> >> table itself? You're only using a very small part of get_deref_node()
> >> here.
> >
> >
> > Nope. Every time we hit an array reference, a wildcard may be floating
> > around somewhere and, if it is, we have to take two paths: One for the
> > direct reference and one for the wildcard.
>
> Wait, I'm confused... looking at get_deref_node, it's always going to
> hit the deref_type_var case then immediately return the entry it found
> or created. I wasn't talking about deref_may_be_aliased_node(), just
> the 3 lines above. What I mean is that we can pull out the "searching
> or creating the root of the deref_node tree" part of get_deref_node()
> into a separate function and then just use that here.
>
Right... I missed what you were saying. Sure, we could just lookup the
root.
>
> >
> >>
> >>
> >> > +
> >> > + /* An invalid dereference can't be aliased. */
> >> > + if (node == NULL)
> >> > + return false;
> >> > +
> >> > + return deref_may_be_aliased_node(node, &deref->deref, state);
> >> > +}
> >> > +
> >> > +static bool
> >> > +fill_deref_tables_block(nir_block *block, void *void_state)
> >> > +{
> >> > + struct lower_variables_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:
> >> > + register_load_instr(intrin, true, state);
> >> > + 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:
> >> > + register_store_instr(intrin, true, state);
> >> > + break;
> >> > +
> >> > + case nir_intrinsic_copy_var:
> >> > + register_copy_instr(intrin, true, state);
> >> > + break;
> >> > +
> >> > + default:
> >> > + continue;
> >> > + }
> >> > + }
> >> > +
> >> > + return true;
> >> > +}
> >> > +
> >> > +static nir_deref *
> >> > +deref_next_wildcard_parent(nir_deref *deref)
> >> > +{
> >> > + for (nir_deref *tail = deref; tail->child; tail = tail->child) {
> >> > + if (tail->child->deref_type != nir_deref_type_array)
> >> > + continue;
> >> > +
> >> > + nir_deref_array *arr = nir_deref_as_array(tail->child);
> >> > +
> >> > + if (arr->deref_array_type == nir_deref_array_type_wildcard)
> >> > + return tail;
> >> > + }
> >> > +
> >> > + return NULL;
> >> > +}
> >> > +
> >> > +static nir_deref *
> >> > +get_deref_tail(nir_deref *deref)
> >> > +{
> >> > + while (deref->child)
> >> > + deref = deref->child;
> >> > +
> >> > + return deref;
> >> > +}
> >>
> >> I'm getting some deja vu, it's like I've seen this function before...
> >> ;) really, need to move it to nir.c.
> >
> >
> > Yeah. nir_deref needs some helpers. That can be done.
> >
> >>
> >>
> >> > +
> >> > +static void
> >> > +emit_copy_load_store(nir_intrinsic_instr *copy_instr,
> >> > + nir_deref_var *dest_head, nir_deref_var
> *src_head,
> >> > + nir_deref *dest_tail, nir_deref *src_tail,
> >> > + struct lower_variables_state *state)
> >> > +{
> >> > + nir_deref *src_arr_parent = deref_next_wildcard_parent(src_tail);
> >> > + nir_deref *dest_arr_parent =
> deref_next_wildcard_parent(dest_tail);
> >> > +
> >> > + if (src_arr_parent || dest_arr_parent) {
> >> > + assert(dest_arr_parent && dest_arr_parent);
> >> > +
> >> > + nir_deref_array *src_arr =
> >> > nir_deref_as_array(src_arr_parent->child);
> >> > + nir_deref_array *dest_arr =
> >> > nir_deref_as_array(dest_arr_parent->child);
> >> > +
> >> > + unsigned length = type_get_length(src_arr_parent->type);
> >> > + assert(length == type_get_length(dest_arr_parent->type));
> >> > + assert(length > 0);
> >> > +
> >> > + src_arr->deref_array_type = nir_deref_array_type_direct;
> >> > + dest_arr->deref_array_type = nir_deref_array_type_direct;
> >> > + for (unsigned i = 0; i < length; i++) {
> >> > + src_arr->base_offset = i;
> >> > + dest_arr->base_offset = i;
> >> > + emit_copy_load_store(copy_instr, dest_head, src_head,
> >> > + &dest_arr->deref, &src_arr->deref,
> >> > state);
> >> > + }
> >> > + src_arr->deref_array_type = nir_deref_array_type_wildcard;
> >> > + dest_arr->deref_array_type = nir_deref_array_type_wildcard;
> >> > + } else {
> >> > + /* Base case. Actually do the copy */
> >> > + src_tail = get_deref_tail(src_tail);
> >> > + dest_tail = get_deref_tail(dest_tail);
> >> > +
> >> > + assert(src_tail->type == dest_tail->type);
> >> > +
> >> > + unsigned num_components =
> >> > glsl_get_vector_elements(src_tail->type);
> >> > +
> >> > + nir_deref *src_deref = nir_copy_deref(state->mem_ctx,
> >> > &src_head->deref);
> >> > + nir_deref *dest_deref = nir_copy_deref(state->mem_ctx,
> >> > &dest_head->deref);
> >> > +
> >> > + nir_intrinsic_op load_op;
> >> > + switch (num_components) {
> >> > + case 1: load_op = nir_intrinsic_load_var_vec1; break;
> >> > + case 2: load_op = nir_intrinsic_load_var_vec2; break;
> >> > + case 3: load_op = nir_intrinsic_load_var_vec3; break;
> >> > + case 4: load_op = nir_intrinsic_load_var_vec4; break;
> >> > + default: unreachable("Invalid number of components"); break;
> >> > + }
> >> > +
> >> > + nir_intrinsic_instr *load =
> >> > nir_intrinsic_instr_create(state->mem_ctx,
> >> > +
> load_op);
> >> > + load->variables[0] = nir_deref_as_var(src_deref);
> >> > + load->dest.is_ssa = true;
> >> > + nir_ssa_def_init(&load->instr, &load->dest.ssa, num_components,
> >> > NULL);
> >> > +
> >> > + nir_instr_insert_before(©_instr->instr, &load->instr);
> >> > + register_load_instr(load, false, state);
> >> > +
> >> > + nir_intrinsic_op store_op;
> >> > + switch (num_components) {
> >> > + case 1: store_op = nir_intrinsic_store_var_vec1; break;
> >> > + case 2: store_op = nir_intrinsic_store_var_vec2; break;
> >> > + case 3: store_op = nir_intrinsic_store_var_vec3; break;
> >> > + case 4: store_op = nir_intrinsic_store_var_vec4; break;
> >> > + default: unreachable("Invalid number of components"); break;
> >> > + }
> >> > +
> >> > + nir_intrinsic_instr *store =
> >> > nir_intrinsic_instr_create(state->mem_ctx,
> >> > +
> >> > store_op);
> >> > + store->variables[0] = nir_deref_as_var(dest_deref);
> >> > + store->src[0].is_ssa = true;
> >> > + store->src[0].ssa = &load->dest.ssa;
> >> > +
> >> > + if (copy_instr->has_predicate) {
> >> > + store->has_predicate = true;
> >> > + store->predicate = nir_src_copy(copy_instr->predicate,
> >> > state->mem_ctx);
> >> > + }
> >> > +
> >> > + nir_instr_insert_before(©_instr->instr, &store->instr);
> >> > + register_store_instr(store, false, state);
> >> > + }
> >> > +}
> >> > +
> >> > +static bool
> >> > +lower_copies_to_load_store(struct deref_node *node,
> >> > + struct lower_variables_state *state)
> >>
> >> This never returns false, so just make it return void.
> >
> >
> > No, we do use the return value. It's passed into foreach_deref_match
> down
> > there
>
> Ok, depending on your answer to my comment about foreach_deref_match
> and foreach_deref_worker I think we can still clean it up then.
>
Oh, don't worry. This entire file needs to be cleaned up. It's just about
as clean as I was able to get it at the time.
>
> >
> >>
> >>
> >> > +{
> >> > + if (!node->copies)
> >> > + return true;
> >> > +
> >> > + struct set_entry *copy_entry;
> >> > + set_foreach(node->copies, copy_entry) {
> >> > + nir_intrinsic_instr *copy = (void *)copy_entry->key;
> >> > +
> >> > + emit_copy_load_store(copy, copy->variables[0],
> >> > copy->variables[1],
> >> > + ©->variables[0]->deref,
> >> > + ©->variables[1]->deref,
> >> > + state);
> >> > +
> >> > + for (unsigned i = 0; i < 2; ++i) {
> >> > + struct deref_node *arg_node =
> >> > get_deref_node(copy->variables[i],
> >> > + false, state);
> >> > + if (arg_node == NULL)
> >> > + continue;
> >> > +
> >> > + struct set_entry *arg_entry =
> >> > _mesa_set_search(arg_node->copies,
> >> > +
> >> > copy_entry->hash,
> >> > + copy);
> >> > + assert(arg_entry);
> >> > + _mesa_set_remove(node->copies, arg_entry);
> >> > + }
> >> > +
> >> > + nir_instr_remove(©->instr);
> >> > + }
> >> > +
> >> > + return true;
> >> > +}
> >> > +
> >> > +static nir_load_const_instr *
> >> > +get_const_initializer_load(const nir_deref_var *deref,
> >> > + struct lower_variables_state *state)
> >> > +{
> >> > + nir_constant *constant = deref->var->constant_initializer;
> >> > + const nir_deref *tail = &deref->deref;
> >> > + unsigned matrix_offset = 0;
> >> > + while (tail->child) {
> >> > + switch (tail->child->deref_type) {
> >> > + case nir_deref_type_array: {
> >> > + nir_deref_array *arr = nir_deref_as_array(tail->child);
> >> > + assert(arr->deref_array_type ==
> nir_deref_array_type_direct);
> >> > + if (glsl_type_is_matrix(tail->type)) {
> >> > + assert(arr->deref.child == NULL);
> >> > + matrix_offset = arr->base_offset;
> >> > + } else {
> >> > + constant = constant->elements[arr->base_offset];
> >> > + }
> >> > + break;
> >> > + }
> >> > +
> >> > + case nir_deref_type_struct: {
> >> > + constant =
> >> > constant->elements[nir_deref_as_struct(tail->child)->index];
> >> > + break;
> >> > + }
> >> > +
> >> > + default:
> >> > + unreachable("Invalid deref child type");
> >> > + }
> >> > +
> >> > + tail = tail->child;
> >> > + }
> >> > +
> >> > + nir_load_const_instr *load =
> >> > nir_load_const_instr_create(state->mem_ctx);
> >> > + load->array_elems = 0;
> >> > + load->num_components = glsl_get_vector_elements(tail->type);
> >> > +
> >> > + matrix_offset *= load->num_components;
> >> > + for (unsigned i = 0; i < load->num_components; i++) {
> >> > + switch (glsl_get_base_type(tail->type)) {
> >> > + case GLSL_TYPE_FLOAT:
> >> > + case GLSL_TYPE_INT:
> >> > + case GLSL_TYPE_UINT:
> >> > + load->value.u[i] = constant->value.u[matrix_offset + i];
> >> > + break;
> >> > + case GLSL_TYPE_BOOL:
> >> > + load->value.u[i] = constant->value.u[matrix_offset + i] ?
> >> > + NIR_TRUE : NIR_FALSE;
> >> > + break;
> >> > + default:
> >> > + unreachable("Invalid immediate type");
> >> > + }
> >> > + }
> >> > +
> >> > + return load;
> >> > +}
> >> > +
> >> > +static void
> >> > +def_stack_push(struct deref_node *node, nir_ssa_def *def,
> >> > + struct lower_variables_state *state)
> >> > +{
> >> > + if (node->def_stack == NULL) {
> >> > + node->def_stack = ralloc_array(state->dead_ctx, nir_ssa_def *,
> >> > + state->impl->num_blocks);
> >> > + node->def_stack_tail = node->def_stack - 1;
> >> > + }
> >> > +
> >> > + if (node->def_stack_tail >= node->def_stack) {
> >> > + nir_ssa_def *top_def = *node->def_stack_tail;
> >> > +
> >> > + if (def->parent_instr->block == top_def->parent_instr->block) {
> >> > + /* They're in the same block, just replace the top */
> >> > + *node->def_stack_tail = def;
> >> > + return;
> >> > + }
> >> > + }
> >> > +
> >> > + *(++node->def_stack_tail) = def;
> >> > +}
> >> > +
> >> > +static nir_ssa_def *
> >> > +get_ssa_def_for_block(struct deref_node *node, nir_block *block,
> >> > + struct lower_variables_state *state)
> >> > +{
> >> > + if (node->def_stack) {
> >> > + while (node->def_stack_tail >= node->def_stack) {
> >> > + nir_ssa_def *def = *node->def_stack_tail;
> >> > +
> >> > + for (nir_block *dom = block; dom != NULL; dom =
> dom->imm_dom)
> >> > {
> >> > + if (def->parent_instr->block == dom)
> >> > + return def;
> >> > + }
> >> > +
> >> > + node->def_stack_tail--;
> >> > + }
> >> > + }
> >> > +
> >> > + /* If we got here then we don't have a definition that dominates
> the
> >> > + * given block. This means that we need to add an undef and use
> >> > that.
> >> > + */
> >> > + nir_ssa_undef_instr *undef =
> >> > nir_ssa_undef_instr_create(state->mem_ctx);
> >> > + nir_ssa_def_init(&undef->instr, &undef->def,
> >> > + glsl_get_vector_elements(node->type), NULL);
> >> > + nir_instr_insert_before_cf_list(&state->impl->body,
> &undef->instr);
> >> > + def_stack_push(node, &undef->def, state);
> >> > + return &undef->def;
> >> > +}
> >>
> >> I've said this before, but I really think we should be doing exactly
> >> what the paper says. It might be just an optimization, but it gives
> >> paranoid people like me much greater confidence that what we're doing
> >> is actually correct. Also, we should be referencing the paper in a
> >> comment somewhere...
> >>
> >> Here are the changes I think you'll need to make:
> >>
> >> -Add a hash table to the state that maps from SSA definition to deref
> >> node, and make def_stack_push() update it (but only when we don't
> >> replace the top of the stack to prevent popping more than once per
> >> stack)
> >> -Add the for loop in deref_to_ssa_block() that goes backwards, looking
> >> at each SSA definition and if it corresponds to a deref node, pops
> >> that node's stack
> >> -Make get_ssa_def_for_block() not pop the stack
> >>
> >> I don't think it'll be that difficult, and you may even end up with
> >> less code after doing the third step.
> >
> >
> > Given that we know that, at any given point, the top of the stack
> belongs to
> > either the current block or one of its parents in the dominance tree, why
> > can't we just do "if (stack_top->block == block) pop()" after walking the
> > children?
>
> Because then we'd have to walk every node after visiting every block
> to make that check, something that's probably much more expensive than
> walking every instruction. At least, that's why the paper's written
> that way.
Right... I thought through that earlier today and, aparently, forgot.
>
> >
> >>
> >>
> >> > +
> >> > +static void
> >> > +add_phi_sources(nir_block *block, nir_block *pred,
> >> > + struct lower_variables_state *state)
> >> > +{
> >> > + nir_foreach_instr(block, instr) {
> >> > + if (instr->type != nir_instr_type_phi)
> >> > + break;
> >> > +
> >> > + nir_phi_instr *phi = nir_instr_as_phi(instr);
> >> > +
> >> > + struct hash_entry *entry =
> >> > + _mesa_hash_table_search(state->phi_table,
> >> > + _mesa_hash_pointer(phi), phi);
> >> > + if (!entry)
> >> > + continue;
> >> > +
> >> > + struct deref_node *node = entry->data;
> >> > +
> >> > + nir_phi_src *src = ralloc(state->mem_ctx, nir_phi_src);
> >> > + src->pred = pred;
> >> > + src->src.is_ssa = true;
> >> > + src->src.ssa = get_ssa_def_for_block(node, pred, state);
> >> > +
> >> > + _mesa_set_add(src->src.ssa->uses, _mesa_hash_pointer(instr),
> >> > instr);
> >> > +
> >> > + exec_list_push_tail(&phi->srcs, &src->node);
> >> > + }
> >> > +}
> >> > +
> >> > +static bool
> >> > +lower_deref_to_ssa_block(nir_block *block, void *void_state)
> >> > +{
> >> > + struct lower_variables_state *state = void_state;
> >> > +
> >> > + nir_foreach_instr_safe(block, instr) {
> >> > + if (instr->type == nir_instr_type_phi) {
> >> > + nir_phi_instr *phi = nir_instr_as_phi(instr);
> >> > +
> >> > + struct hash_entry *entry =
> >> > + _mesa_hash_table_search(state->phi_table,
> >> > + _mesa_hash_pointer(phi), phi);
> >> > +
> >> > + /* This can happen if we already have phi nodes in the
> program
> >> > + * that were not created in this pass.
> >> > + */
> >> > + if (!entry)
> >> > + continue;
> >> > +
> >> > + struct deref_node *node = entry->data;
> >> > +
> >> > + def_stack_push(node, &phi->dest.ssa, state);
> >> > + } else if (instr->type == nir_instr_type_intrinsic) {
> >> > + 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: {
> >> > + struct deref_node *node =
> >> > get_deref_node(intrin->variables[0],
> >> > + false, state);
> >> > + unsigned num_chans =
> >> > +
> nir_intrinsic_infos[intrin->intrinsic].dest_components;
> >> > +
> >> > + if (node == NULL) {
> >> > + /* If we hit this path then we are referencing an
> >> > invalid
> >> > + * value. Most likely, we unrolled something and are
> >> > + * reading past the end of some array. In any case,
> >> > this
> >> > + * should result in an undefined value.
> >> > + */
> >> > + nir_ssa_undef_instr *undef =
> >> > + nir_ssa_undef_instr_create(state->mem_ctx);
> >> > + nir_ssa_def_init(&undef->instr, &undef->def,
> num_chans,
> >> > NULL);
> >> > +
> >> > + nir_instr_insert_before(&intrin->instr,
> &undef->instr);
> >> > + nir_instr_remove(&intrin->instr);
> >> > +
> >> > + nir_src new_src = {
> >> > + .is_ssa = true,
> >> > + .ssa = &undef->def,
> >> > + };
> >> > +
> >> > + nir_ssa_def_rewrite_uses(&intrin->dest.ssa, new_src,
> >> > + state->mem_ctx);
> >> > + continue;
> >> > + }
> >> > +
> >> > + if (!node->lower_to_ssa)
> >> > + continue;
> >> > +
> >> > + nir_alu_instr *mov = nir_alu_instr_create(state->mem_ctx,
> >> > + nir_op_imov);
> >> > + mov->src[0].src.is_ssa = true;
> >> > + mov->src[0].src.ssa = get_ssa_def_for_block(node, block,
> >> > state);
> >> > + for (unsigned i = num_chans; i < 4; i++)
> >> > + mov->src[0].swizzle[i] = 0;
> >> > +
> >> > + assert(intrin->dest.is_ssa);
> >> > +
> >> > + mov->dest.write_mask = (1 << num_chans) - 1;
> >> > + mov->dest.dest.is_ssa = true;
> >> > + nir_ssa_def_init(&mov->instr, &mov->dest.dest.ssa,
> >> > num_chans, NULL);
> >> > +
> >> > + nir_instr_insert_before(&intrin->instr, &mov->instr);
> >> > + nir_instr_remove(&intrin->instr);
> >> > +
> >> > + 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);
> >> > + 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: {
> >> > + struct deref_node *node =
> >> > get_deref_node(intrin->variables[0],
> >> > + false, state);
> >> > +
> >> > + if (node == NULL) {
> >> > + /* Probably an out-of-bounds array store. That should
> >> > be a
> >> > + * no-op. */
> >> > + nir_instr_remove(&intrin->instr);
> >> > + continue;
> >> > + }
> >> > +
> >> > + if (!node->lower_to_ssa)
> >> > + continue;
> >> > +
> >> > + unsigned num_chans =
> glsl_get_vector_elements(node->type);
> >> > +
> >> > + assert(intrin->src[0].is_ssa);
> >> > +
> >> > + nir_alu_instr *mov;
> >> > + if (intrin->has_predicate) {
> >> > + mov = nir_alu_instr_create(state->mem_ctx,
> >> > nir_op_bcsel);
> >> > + mov->src[0].src = nir_src_copy(intrin->predicate,
> >> > + state->mem_ctx);
> >> > + memset(mov->src[0].swizzle, 0, sizeof
> >> > mov->src[0].swizzle);
> >> > +
> >> > + mov->src[1].src.is_ssa = true;
> >> > + mov->src[1].src.ssa = intrin->src[0].ssa;
> >> > + for (unsigned i = num_chans; i < 4; i++)
> >> > + mov->src[1].swizzle[i] = 0;
> >> > +
> >> > + mov->src[2].src.is_ssa = true;
> >> > + mov->src[2].src.ssa = get_ssa_def_for_block(node,
> block,
> >> > state);
> >> > + for (unsigned i = num_chans; i < 4; i++)
> >> > + mov->src[2].swizzle[i] = 0;
> >> > +
> >> > + } else {
> >> > + mov = nir_alu_instr_create(state->mem_ctx,
> nir_op_imov);
> >> > +
> >> > + mov->src[0].src.is_ssa = true;
> >> > + mov->src[0].src.ssa = intrin->src[0].ssa;
> >> > + for (unsigned i = num_chans; i < 4; i++)
> >> > + mov->src[0].swizzle[i] = 0;
> >> > + }
> >> > +
> >> > + mov->dest.write_mask = (1 << num_chans) - 1;
> >> > + mov->dest.dest.is_ssa = true;
> >> > + nir_ssa_def_init(&mov->instr, &mov->dest.dest.ssa,
> >> > num_chans, NULL);
> >> > +
> >> > + nir_instr_insert_before(&intrin->instr, &mov->instr);
> >> > + nir_instr_remove(&intrin->instr);
> >> > +
> >> > + def_stack_push(node, &mov->dest.dest.ssa, state);
> >> > + break;
> >> > + }
> >> > +
> >> > + default:
> >> > + break;
> >> > + }
> >> > + }
> >> > + }
> >> > +
> >> > + if (block->successors[0])
> >> > + add_phi_sources(block->successors[0], block, state);
> >> > + if (block->successors[1])
> >> > + add_phi_sources(block->successors[1], block, state);
> >> > +
> >> > + return true;
> >> > +}
> >> > +
> >> > +static void
> >> > +insert_phi_nodes(struct lower_variables_state *state)
> >> > +{
> >> > + unsigned work[state->impl->num_blocks];
> >> > + unsigned has_already[state->impl->num_blocks];
> >> > + nir_block *W[state->impl->num_blocks];
> >> > +
> >> > + memset(work, 0, sizeof work);
> >> > + memset(has_already, 0, sizeof has_already);
> >> > +
> >> > + unsigned w_start, w_end;
> >> > + unsigned iter_count = 0;
> >> > +
> >> > + struct hash_entry *deref_entry;
> >> > + hash_table_foreach(state->deref_leaves, deref_entry) {
> >> > + struct deref_node *node = deref_entry->data;
> >> > +
> >> > + if (node->stores == NULL)
> >> > + continue;
> >> > +
> >> > + if (!node->lower_to_ssa)
> >> > + continue;
> >> > +
> >> > + w_start = w_end = 0;
> >> > + iter_count++;
> >> > +
> >> > + struct set_entry *store_entry;
> >> > + set_foreach(node->stores, store_entry) {
> >> > + nir_intrinsic_instr *store = (nir_intrinsic_instr
> >> > *)store_entry->key;
> >> > + if (work[store->instr.block->index] < iter_count)
> >> > + W[w_end++] = store->instr.block;
> >> > + work[store->instr.block->index] = iter_count;
> >> > + }
> >> > +
> >> > + while (w_start != w_end) {
> >> > + nir_block *cur = W[w_start++];
> >> > + struct set_entry *dom_entry;
> >> > + set_foreach(cur->dom_frontier, dom_entry) {
> >> > + nir_block *next = (nir_block *) dom_entry->key;
> >> > +
> >> > + /*
> >> > + * If there's more than one return statement, then the
> end
> >> > block
> >> > + * can be a join point for some definitions. However,
> there
> >> > are
> >> > + * no instructions in the end block, so nothing would use
> >> > those
> >> > + * phi nodes. Of course, we couldn't place those phi
> nodes
> >> > + * anyways due to the restriction of having no
> instructions
> >> > in the
> >> > + * end block...
> >> > + */
> >> > + if (next == state->impl->end_block)
> >> > + continue;
> >> > +
> >> > + if (has_already[next->index] < iter_count) {
> >> > + nir_phi_instr *phi =
> >> > nir_phi_instr_create(state->mem_ctx);
> >> > + phi->dest.is_ssa = true;
> >> > + nir_ssa_def_init(&phi->instr, &phi->dest.ssa,
> >> > + glsl_get_vector_elements(node->type),
> >> > NULL);
> >> > + nir_instr_insert_before_block(next, &phi->instr);
> >> > +
> >> > + _mesa_hash_table_insert(state->phi_table,
> >> > + _mesa_hash_pointer(phi), phi,
> >> > node);
> >> > +
> >> > + has_already[next->index] = iter_count;
> >> > + if (work[next->index] < iter_count) {
> >> > + work[next->index] = iter_count;
> >> > + W[w_end++] = next;
> >> > + }
> >> > + }
> >> > + }
> >> > + }
> >> > + }
> >> > +}
> >> > +
> >> > +static bool
> >> > +nir_lower_variables_impl(nir_function_impl *impl)
> >> > +{
> >> > + struct lower_variables_state state;
> >> > +
> >> > + state.mem_ctx = ralloc_parent(impl);
> >> > + state.dead_ctx = ralloc_context(state.mem_ctx);
> >> > + state.impl = impl;
> >> > +
> >> > + state.deref_var_nodes = _mesa_hash_table_create(state.dead_ctx,
> >> > +
> >> > _mesa_key_pointer_equal);
> >> > + state.deref_leaves = _mesa_hash_table_create(state.dead_ctx,
> >> > + derefs_equal);
> >> > + state.phi_table = _mesa_hash_table_create(state.dead_ctx,
> >> > +
> _mesa_key_pointer_equal);
> >> > +
> >> > + nir_foreach_block(impl, fill_deref_tables_block, &state);
> >> > +
> >> > + struct set *outputs = _mesa_set_create(state.dead_ctx,
> >> > + _mesa_key_pointer_equal);
> >> > +
> >> > + bool progress = false;
> >> > +
> >> > + nir_metadata_require(impl, nir_metadata_block_index);
> >> > +
> >> > + struct hash_entry *entry;
> >> > + hash_table_foreach(state.deref_leaves, entry) {
> >> > + nir_deref_var *deref = (void *)entry->key;
> >> > + struct deref_node *node = entry->data;
> >> > +
> >> > + if (deref->var->data.mode != nir_var_local) {
> >> > + _mesa_hash_table_remove(state.deref_leaves, entry);
> >> > + continue;
> >> > + }
> >> > +
> >> > + if (deref_may_be_aliased(deref, &state)) {
> >> > + _mesa_hash_table_remove(state.deref_leaves, entry);
> >> > + continue;
> >> > + }
> >> > +
> >> > + node->lower_to_ssa = true;
> >> > + progress = true;
> >> > +
> >> > + if (deref->var->constant_initializer) {
> >> > + nir_load_const_instr *load =
> get_const_initializer_load(deref,
> >> > &state);
> >> > + load->dest.is_ssa = true;
> >> > + nir_ssa_def_init(&load->instr, &load->dest.ssa,
> >> > + glsl_get_vector_elements(node->type),
> NULL);
> >> > + nir_instr_insert_before_cf_list(&impl->body, &load->instr);
> >> > + def_stack_push(node, &load->dest.ssa, &state);
> >> > + }
> >> > +
> >> > + if (deref->var->data.mode == nir_var_shader_out)
> >> > + _mesa_set_add(outputs, _mesa_hash_pointer(node), node);
> >> > +
> >> > + foreach_deref_node_match(deref, lower_copies_to_load_store,
> >> > &state);
>
It's used right here ^^
> >> > + }
> >> > +
> >> > + if (!progress)
> >> > + return false;
> >> > +
> >> > + nir_metadata_require(impl, nir_metadata_dominance);
> >> > +
> >> > + insert_phi_nodes(&state);
> >> > + nir_foreach_block(impl, lower_deref_to_ssa_block, &state);
> >> > +
> >> > + nir_metadata_dirty(impl, nir_metadata_block_index |
> >> > + nir_metadata_dominance);
> >> > +
> >> > + ralloc_free(state.dead_ctx);
> >> > +
> >> > + return progress;
> >> > +}
> >> > +
> >> > +void
> >> > +nir_lower_variables(nir_shader *shader)
> >> > +{
> >> > + nir_foreach_overload(shader, overload) {
> >> > + if (overload->impl)
> >> > + nir_lower_variables_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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