nir: add an instruction set API

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).

Reviewed-by: Jason Ekstrand <[email protected]>
Signed-off-by: Connor Abbott <[email protected]>

2 files changed, 349 insertions, 0 deletions

diff --git a/src/glsl/nir/nir_instr_set.c b/src/glsl/nir/nir_instr_set.c
index 72ab04895f6..7460fccba10 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 f5baffacb0e..a7f6c9dd1eb 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);
+
+/*@}*/
+