Reviewed-by: Jason Ekstrand <jason.ekstr...@intel.com>
On Thu, Oct 8, 2015 at 9:46 PM, Connor Abbott <cwabbo...@gmail.com> wrote:
> This will replace direct usage of nir_instrs_equal() in the CSE pass,
> which reduces an O(n^2) algorithm with an effectively O(n) one. It'll
> also be useful for implementing GVN on top of GCM.
>
> v2:
> - Add texture support.
> - Add more comments.
> - Rename instr_can_hash() to instr_can_rewrite() since it's really more
> about whether its uses can be rewritten, and it's implicitly used by
> nir_instrs_equal() as well.
> - Rename nir_instr_set_add() to nir_instr_set_add_or_rewrite() (Jason).
> - Make the HASH() macro less magical (Topi).
> - Rewrite the commit message.
>
> v3:
> - For sorting phi sources, use a VLA, store pointers to the sources, and
> compare the predecessor pointer directly (Jason).
>
> Signed-off-by: Connor Abbott <cwabbo...@gmail.com>
> ---
> Jason, does this look good to you? Still no piglit regressions -- I'm
> working on getting perf numbers.
>
> src/glsl/nir/nir_instr_set.c | 314
> +++++++++++++++++++++++++++++++++++++++++++
> src/glsl/nir/nir_instr_set.h | 35 +++++
> 2 files changed, 349 insertions(+)
>
> diff --git a/src/glsl/nir/nir_instr_set.c b/src/glsl/nir/nir_instr_set.c
> index 72ab048..7460fcc 100644
> --- a/src/glsl/nir/nir_instr_set.c
> +++ b/src/glsl/nir/nir_instr_set.c
> @@ -22,6 +22,181 @@
> */
>
> #include "nir_instr_set.h"
> +#include "nir_vla.h"
> +
> +#define HASH(hash, data) _mesa_fnv32_1a_accumulate((hash), (data))
> +
> +static uint32_t
> +hash_src(uint32_t hash, const nir_src *src)
> +{
> + assert(src->is_ssa);
> + hash = HASH(hash, src->ssa);
> + return hash;
> +}
> +
> +static uint32_t
> +hash_alu_src(uint32_t hash, const nir_alu_src *src, unsigned num_components)
> +{
> + hash = HASH(hash, src->abs);
> + hash = HASH(hash, src->negate);
> +
> + for (unsigned i = 0; i < num_components; i++)
> + hash = HASH(hash, src->swizzle[i]);
> +
> + hash = hash_src(hash, &src->src);
> + return hash;
> +}
> +
> +static uint32_t
> +hash_alu(uint32_t hash, const nir_alu_instr *instr)
> +{
> + hash = HASH(hash, instr->op);
> + hash = HASH(hash, instr->dest.dest.ssa.num_components);
> +
> + if (nir_op_infos[instr->op].algebraic_properties & NIR_OP_IS_COMMUTATIVE)
> {
> + assert(nir_op_infos[instr->op].num_inputs == 2);
> + uint32_t hash0 = hash_alu_src(hash, &instr->src[0],
> + nir_ssa_alu_instr_src_components(instr,
> 0));
> + uint32_t hash1 = hash_alu_src(hash, &instr->src[1],
> + nir_ssa_alu_instr_src_components(instr,
> 1));
> + /* For commutative operations, we need some commutative way of
> + * combining the hashes. One option would be to XOR them but that
> + * means that anything with two identical sources will hash to 0 and
> + * that's common enough we probably don't want the guaranteed
> + * collision. Either addition or multiplication will also work.
> + */
> + hash = hash0 * hash1;
> + } else {
> + for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++) {
> + hash = hash_alu_src(hash, &instr->src[i],
> + nir_ssa_alu_instr_src_components(instr, i));
> + }
> + }
> +
> + return hash;
> +}
> +
> +static uint32_t
> +hash_load_const(uint32_t hash, const nir_load_const_instr *instr)
> +{
> + hash = HASH(hash, instr->def.num_components);
> +
> + hash = _mesa_fnv32_1a_accumulate_block(hash, instr->value.f,
> + instr->def.num_components
> + * sizeof(instr->value.f[0]));
> +
> + return hash;
> +}
> +
> +static int
> +cmp_phi_src(const void *data1, const void *data2)
> +{
> + nir_phi_src *src1 = *(nir_phi_src **)data1;
> + nir_phi_src *src2 = *(nir_phi_src **)data2;
> + return src1->pred - src2->pred;
> +}
> +
> +static uint32_t
> +hash_phi(uint32_t hash, const nir_phi_instr *instr)
> +{
> + hash = HASH(hash, instr->instr.block);
> +
> + /* sort sources by predecessor, since the order shouldn't matter */
> + unsigned num_preds = instr->instr.block->predecessors->entries;
> + NIR_VLA(nir_phi_src *, srcs, num_preds);
> + unsigned i = 0;
> + nir_foreach_phi_src(instr, src) {
> + srcs[i++] = src;
> + }
> +
> + qsort(srcs, num_preds, sizeof(nir_phi_src *), cmp_phi_src);
> +
> + for (i = 0; i < num_preds; i++) {
> + hash = hash_src(hash, &srcs[i]->src);
> + hash = HASH(hash, srcs[i]->pred);
> + }
> +
> + return hash;
> +}
> +
> +static uint32_t
> +hash_intrinsic(uint32_t hash, const nir_intrinsic_instr *instr)
> +{
> + const nir_intrinsic_info *info = &nir_intrinsic_infos[instr->intrinsic];
> + hash = HASH(hash, instr->intrinsic);
> +
> + if (info->has_dest)
> + hash = HASH(hash, instr->dest.ssa.num_components);
> +
> + assert(info->num_variables == 0);
> +
> + hash = _mesa_fnv32_1a_accumulate_block(hash, instr->const_index,
> + info->num_indices
> + *
> sizeof(instr->const_index[0]));
> + return hash;
> +}
> +
> +static uint32_t
> +hash_tex(uint32_t hash, const nir_tex_instr *instr)
> +{
> + hash = HASH(hash, instr->op);
> + hash = HASH(hash, instr->num_srcs);
> +
> + for (unsigned i = 0; i < instr->num_srcs; i++) {
> + hash = HASH(hash, instr->src[i].src_type);
> + hash = hash_src(hash, &instr->src[i].src);
> + }
> +
> + hash = HASH(hash, instr->coord_components);
> + hash = HASH(hash, instr->sampler_dim);
> + hash = HASH(hash, instr->is_array);
> + hash = HASH(hash, instr->is_shadow);
> + hash = HASH(hash, instr->is_new_style_shadow);
> + hash = HASH(hash, instr->const_offset);
> + unsigned component = instr->component;
> + hash = HASH(hash, component);
> + hash = HASH(hash, instr->sampler_index);
> + hash = HASH(hash, instr->sampler_array_size);
> +
> + assert(!instr->sampler);
> +
> + return hash;
> +}
> +
> +/* Computes a hash of an instruction for use in a hash table. Note that this
> + * will only work for instructions where instr_can_rewrite() returns true,
> and
> + * it should return identical hashes for two instructions that are the same
> + * according nir_instrs_equal().
> + */
> +
> +static uint32_t
> +hash_instr(const void *data)
> +{
> + const nir_instr *instr = data;
> + uint32_t hash = _mesa_fnv32_1a_offset_bias;
> +
> + switch (instr->type) {
> + case nir_instr_type_alu:
> + hash = hash_alu(hash, nir_instr_as_alu(instr));
> + break;
> + case nir_instr_type_load_const:
> + hash = hash_load_const(hash, nir_instr_as_load_const(instr));
> + break;
> + case nir_instr_type_phi:
> + hash = hash_phi(hash, nir_instr_as_phi(instr));
> + break;
> + case nir_instr_type_intrinsic:
> + hash = hash_intrinsic(hash, nir_instr_as_intrinsic(instr));
> + break;
> + case nir_instr_type_tex:
> + hash = hash_tex(hash, nir_instr_as_tex(instr));
> + break;
> + default:
> + unreachable("Invalid instruction type");
> + }
> +
> + return hash;
> +}
>
> bool
> nir_srcs_equal(nir_src src1, nir_src src2)
> @@ -66,6 +241,12 @@ nir_alu_srcs_equal(const nir_alu_instr *alu1, const
> nir_alu_instr *alu2,
> return nir_srcs_equal(alu1->src[src1].src, alu2->src[src2].src);
> }
>
> +/* Returns "true" if two instructions are equal. Note that this will only
> + * work for the subset of instructions defined by instr_can_rewrite(). Also,
> + * it should only return "true" for instructions that hash_instr() will
> return
> + * the same hash for (ignoring collisions, of course).
> + */
> +
> bool
> nir_instrs_equal(const nir_instr *instr1, const nir_instr *instr2)
> {
> @@ -204,3 +385,136 @@ nir_instrs_equal(const nir_instr *instr1, const
> nir_instr *instr2)
> return false;
> }
>
> +static bool
> +src_is_ssa(nir_src *src, void *data)
> +{
> + (void) data;
> + return src->is_ssa;
> +}
> +
> +static bool
> +dest_is_ssa(nir_dest *dest, void *data)
> +{
> + (void) data;
> + return dest->is_ssa;
> +}
> +
> +/* This function determines if uses of an instruction can safely be rewritten
> + * to use another identical instruction instead. Note that this function must
> + * be kept in sync with hash_instr() and nir_instrs_equal() -- only
> + * instructions that pass this test will be handed on to those functions, and
> + * conversely they must handle everything that this function returns true
> for.
> + */
> +
> +static bool
> +instr_can_rewrite(nir_instr *instr)
> +{
> + /* We only handle SSA. */
> + if (!nir_foreach_dest(instr, dest_is_ssa, NULL) ||
> + !nir_foreach_src(instr, src_is_ssa, NULL))
> + return false;
> +
> + switch (instr->type) {
> + case nir_instr_type_alu:
> + case nir_instr_type_load_const:
> + case nir_instr_type_phi:
> + return true;
> + case nir_instr_type_tex: {
> + nir_tex_instr *tex = nir_instr_as_tex(instr);
> +
> + /* Don't support un-lowered sampler derefs currently. */
> + if (tex->sampler)
> + return false;
> +
> + return true;
> + }
> + case nir_instr_type_intrinsic: {
> + const nir_intrinsic_info *info =
> + &nir_intrinsic_infos[nir_instr_as_intrinsic(instr)->intrinsic];
> + return (info->flags & NIR_INTRINSIC_CAN_ELIMINATE) &&
> + (info->flags & NIR_INTRINSIC_CAN_REORDER) &&
> + info->num_variables == 0; /* not implemented yet */
> + }
> + case nir_instr_type_call:
> + case nir_instr_type_jump:
> + case nir_instr_type_ssa_undef:
> + return false;
> + case nir_instr_type_parallel_copy:
> + default:
> + unreachable("Invalid instruction type");
> + }
> +
> + return false;
> +}
> +
> +static nir_ssa_def *
> +nir_instr_get_dest_ssa_def(nir_instr *instr)
> +{
> + switch (instr->type) {
> + case nir_instr_type_alu:
> + assert(nir_instr_as_alu(instr)->dest.dest.is_ssa);
> + return &nir_instr_as_alu(instr)->dest.dest.ssa;
> + case nir_instr_type_load_const:
> + return &nir_instr_as_load_const(instr)->def;
> + case nir_instr_type_phi:
> + assert(nir_instr_as_phi(instr)->dest.is_ssa);
> + return &nir_instr_as_phi(instr)->dest.ssa;
> + case nir_instr_type_intrinsic:
> + assert(nir_instr_as_intrinsic(instr)->dest.is_ssa);
> + return &nir_instr_as_intrinsic(instr)->dest.ssa;
> + case nir_instr_type_tex:
> + assert(nir_instr_as_tex(instr)->dest.is_ssa);
> + return &nir_instr_as_tex(instr)->dest.ssa;
> + default:
> + unreachable("We never ask for any of these");
> + }
> +}
> +
> +static bool
> +cmp_func(const void *data1, const void *data2)
> +{
> + return nir_instrs_equal(data1, data2);
> +}
> +
> +struct set *
> +nir_instr_set_create(void *mem_ctx)
> +{
> + return _mesa_set_create(mem_ctx, hash_instr, cmp_func);
> +}
> +
> +void
> +nir_instr_set_destroy(struct set *instr_set)
> +{
> + _mesa_set_destroy(instr_set, NULL);
> +}
> +
> +bool
> +nir_instr_set_add_or_rewrite(struct set *instr_set, nir_instr *instr)
> +{
> + if (!instr_can_rewrite(instr))
> + return false;
> +
> + struct set_entry *entry = _mesa_set_search(instr_set, instr);
> + if (entry) {
> + nir_ssa_def *def = nir_instr_get_dest_ssa_def(instr);
> + nir_ssa_def *new_def =
> + nir_instr_get_dest_ssa_def((nir_instr *) entry->key);
> + nir_ssa_def_rewrite_uses(def, nir_src_for_ssa(new_def));
> + return true;
> + }
> +
> + _mesa_set_add(instr_set, instr);
> + return false;
> +}
> +
> +void
> +nir_instr_set_remove(struct set *instr_set, nir_instr *instr)
> +{
> + if (!instr_can_rewrite(instr))
> + return;
> +
> + struct set_entry *entry = _mesa_set_search(instr_set, instr);
> + if (entry)
> + _mesa_set_remove(instr_set, entry);
> +}
> +
> diff --git a/src/glsl/nir/nir_instr_set.h b/src/glsl/nir/nir_instr_set.h
> index f5baffa..a7f6c9d 100644
> --- a/src/glsl/nir/nir_instr_set.h
> +++ b/src/glsl/nir/nir_instr_set.h
> @@ -27,3 +27,38 @@
>
> bool nir_instrs_equal(const nir_instr *instr1, const nir_instr *instr2);
>
> +/**
> + * This file defines functions for creating, destroying, and manipulating an
> + * "instruction set," which is an abstraction for finding duplicate
> + * instructions using a hash set. Note that the question of whether an
> + * instruction is actually a duplicate (e.g. whether it has any side effects)
> + * is handled transparently. The user can pass any instruction to
> + * nir_instr_set_add_or_rewrite() and nir_instr_set_remove(), and if the
> + * instruction isn't safe to rewrite or isn't supported, it's silently
> + * removed.
> + */
> +
> +/*@{*/
> +
> +/** Creates an instruction set, using a given ralloc mem_ctx */
> +struct set *nir_instr_set_create(void *mem_ctx);
> +
> +/** Destroys an instruction set. */
> +void nir_instr_set_destroy(struct set *instr_set);
> +
> +/**
> + * Adds an instruction to an instruction set if it doesn't exist, or if it
> + * does already exist, rewrites all uses of it to point to the other
> + * already-inserted instruction. Returns 'true' if the uses of the
> instruction
> + * were rewritten.
> + */
> +bool nir_instr_set_add_or_rewrite(struct set *instr_set, nir_instr *instr);
> +
> +/**
> + * Removes an instruction from an instruction set, so that other instructions
> + * won't be merged with it.
> + */
> +void nir_instr_set_remove(struct set *instr_set, nir_instr *instr);
> +
> +/*@}*/
> +
> --
> 2.1.0
>
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