nir: Add a basic CSE pass

This pass is still fairly basic.  It only handles ALU operations, constant
loads, and phi nodes.  No texture ops or intrinsics yet.

Reviewed-by: Connor Abbott <cwabbott0@gmail.com>

src/glsl/Makefile.sources

@@ -30,6 +30,7 @@ NIR_FILES = \
 	$(GLSL_SRCDIR)/nir/nir_opcodes.c \
 	$(GLSL_SRCDIR)/nir/nir_opcodes.h \
 	$(GLSL_SRCDIR)/nir/nir_opt_copy_propagate.c \
+	$(GLSL_SRCDIR)/nir/nir_opt_cse.c \
 	$(GLSL_SRCDIR)/nir/nir_opt_dce.c \
 	$(GLSL_SRCDIR)/nir/nir_opt_global_to_local.c \
 	$(GLSL_SRCDIR)/nir/nir_opt_peephole_ffma.c \

src/glsl/nir/nir.h

@@ -1370,6 +1370,8 @@ bool nir_opt_global_to_local(nir_shader *shader);
 bool nir_copy_prop_impl(nir_function_impl *impl);
 bool nir_copy_prop(nir_shader *shader);
 
+bool nir_opt_cse(nir_shader *shader);
+
 bool nir_opt_dce_impl(nir_function_impl *impl);
 bool nir_opt_dce(nir_shader *shader);
 

src/glsl/nir/nir_opt_cse.c

@@ -0,0 +1,269 @@
+/*
+ * 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@jlekstrand.net)
+ *
+ */
+
+#include "nir.h"
+
+/*
+ * Implements common subexpression elimination
+ */
+
+struct cse_state {
+   void *mem_ctx;
+   bool progress;
+};
+
+static bool
+nir_alu_srcs_equal(nir_alu_src src1, nir_alu_src src2, uint8_t read_mask)
+{
+   if (src1.abs != src2.abs || src1.negate != src2.negate)
+      return false;
+
+   for (int i = 0; i < 4; ++i) {
+      if (!(read_mask & (1 << i)))
+         continue;
+
+      if (src1.swizzle[i] != src2.swizzle[i])
+         return false;
+   }
+
+   return nir_srcs_equal(src1.src, src2.src);
+}
+
+static bool
+nir_instrs_equal(nir_instr *instr1, nir_instr *instr2)
+{
+   if (instr1->type != instr2->type)
+      return false;
+
+   switch (instr1->type) {
+   case nir_instr_type_alu: {
+      nir_alu_instr *alu1 = nir_instr_as_alu(instr1);
+      nir_alu_instr *alu2 = nir_instr_as_alu(instr2);
+
+      if (alu1->op != alu2->op)
+         return false;
+
+      if (alu1->has_predicate != alu2->has_predicate)
+         return false;
+
+      if (alu1->has_predicate &&
+          !nir_srcs_equal(alu1->predicate, alu2->predicate))
+         return false;
+
+      /* TODO: We can probably acutally do something more inteligent such
+       * as allowing different numbers and taking a maximum or something
+       * here */
+      if (alu1->dest.dest.ssa.num_components != alu2->dest.dest.ssa.num_components)
+         return false;
+
+      for (unsigned i = 0; i < nir_op_infos[alu1->op].num_inputs; i++) {
+         if (!nir_alu_srcs_equal(alu1->src[i], alu2->src[i],
+                                 (1 << alu1->dest.dest.ssa.num_components) - 1))
+            return false;
+      }
+      return true;
+   }
+   case nir_instr_type_texture:
+      return false;
+   case nir_instr_type_load_const: {
+      nir_load_const_instr *load1 = nir_instr_as_load_const(instr1);
+      nir_load_const_instr *load2 = nir_instr_as_load_const(instr2);
+
+      if (load1->num_components != load2->num_components)
+         return false;
+
+      return memcmp(load1->value.f, load2->value.f,
+                    load1->num_components * sizeof load2->value.f) == 0;
+   }
+   case nir_instr_type_phi: {
+      nir_phi_instr *phi1 = nir_instr_as_phi(instr1);
+      nir_phi_instr *phi2 = nir_instr_as_phi(instr2);
+
+      if (phi1->instr.block != phi2->instr.block)
+         return false;
+
+      foreach_list_typed(nir_phi_src, src1, node, &phi1->srcs) {
+         foreach_list_typed(nir_phi_src, src2, node, &phi2->srcs) {
+            if (src1->pred == src2->pred) {
+               if (!nir_srcs_equal(src1->src, src2->src))
+                  return false;
+
+               break;
+            }
+         }
+      }
+
+      return true;
+   }
+   case nir_instr_type_intrinsic:
+   case nir_instr_type_call:
+   case nir_instr_type_jump:
+   case nir_instr_type_ssa_undef:
+   case nir_instr_type_parallel_copy:
+   default:
+      unreachable("Invalid instruction type");
+   }
+
+   return false;
+}
+
+static bool
+src_is_ssa(nir_src *src, void *data)
+{
+   return src->is_ssa;
+}
+
+static bool
+dest_is_ssa(nir_dest *dest, void *data)
+{
+   return dest->is_ssa;
+}
+
+static bool
+nir_instr_can_cse(nir_instr *instr)
+{
+   switch (instr->type) {
+   case nir_instr_type_alu:
+   case nir_instr_type_load_const:
+   case nir_instr_type_phi:
+      return nir_foreach_dest(instr, dest_is_ssa, NULL) &&
+             nir_foreach_src(instr, src_is_ssa, NULL);
+   case nir_instr_type_texture:
+      return false; /* TODO */
+   case nir_instr_type_intrinsic:
+   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:
+      assert(nir_instr_as_load_const(instr)->dest.is_ssa);
+      return &nir_instr_as_load_const(instr)->dest.ssa;
+   case nir_instr_type_phi:
+      assert(nir_instr_as_phi(instr)->dest.is_ssa);
+      return &nir_instr_as_phi(instr)->dest.ssa;
+   default:
+      unreachable("We never ask for any of these");
+   }
+}
+
+static void
+nir_opt_cse_instr(nir_instr *instr, struct cse_state *state)
+{
+   if (!nir_instr_can_cse(instr))
+      return;
+
+   for (struct exec_node *node = instr->node.prev;
+        !exec_node_is_head_sentinel(node); node = node->prev) {
+      nir_instr *other = exec_node_data(nir_instr, node, node);
+      if (nir_instrs_equal(instr, other)) {
+         nir_src other_dest_src = {
+            .is_ssa = true,
+            .ssa = nir_instr_get_dest_ssa_def(other),
+         };
+         nir_ssa_def_rewrite_uses(nir_instr_get_dest_ssa_def(instr),
+                                  other_dest_src, state->mem_ctx);
+         nir_instr_remove(instr);
+         state->progress = true;
+         return;
+      }
+   }
+
+   for (nir_block *block = instr->block->imm_dom;
+        block != NULL; block = block->imm_dom) {
+      nir_foreach_instr_reverse(block, other) {
+         if (nir_instrs_equal(instr, other)) {
+            nir_src other_dest_src = {
+               .is_ssa = true,
+               .ssa = nir_instr_get_dest_ssa_def(other),
+            };
+            nir_ssa_def_rewrite_uses(nir_instr_get_dest_ssa_def(instr),
+                                     other_dest_src, state->mem_ctx);
+            nir_instr_remove(instr);
+            state->progress = true;
+            return;
+         }
+      }
+   }
+}
+
+static bool
+nir_opt_cse_block(nir_block *block, void *void_state)
+{
+   struct cse_state *state = void_state;
+
+   nir_foreach_instr_safe(block, instr)
+      nir_opt_cse_instr(instr, state);
+
+   return true;
+}
+
+static bool
+nir_opt_cse_impl(nir_function_impl *impl)
+{
+   struct cse_state state;
+
+   state.mem_ctx = ralloc_parent(impl);
+   state.progress = false;
+
+   nir_metadata_require(impl, nir_metadata_dominance);
+
+   nir_foreach_block(impl, nir_opt_cse_block, &state);
+
+   if (state.progress)
+      nir_metadata_dirty(impl, nir_metadata_block_index |
+                               nir_metadata_dominance);
+
+   return state.progress;
+}
+
+bool
+nir_opt_cse(nir_shader *shader)
+{
+   bool progress = false;
+
+   nir_foreach_overload(shader, overload) {
+      if (overload->impl)
+         progress |= nir_opt_cse_impl(overload->impl);
+   }
+
+   return progress;
+}