nir: add an SSA-based copy propagation pass

src/glsl/Makefile.sources

@@ -25,6 +25,7 @@ NIR_FILES = \
 	$(GLSL_SRCDIR)/nir/nir_lower_variables_scalar.c \
 	$(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_global_to_local.c \
 	$(GLSL_SRCDIR)/nir/nir_print.c \
 	$(GLSL_SRCDIR)/nir/nir_remove_dead_variables.c \

src/glsl/nir/nir.h

@@ -1293,6 +1293,9 @@ void nir_convert_to_ssa(nir_shader *shader);
 
 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);
+
 #ifdef __cplusplus
 } /* extern "C" */
 #endif

src/glsl/nir/nir_opt_copy_propagate.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:
+ *    Connor Abbott (cwabbott0@gmail.com)
+ *
+ */
+
+#include "nir.h"
+#include <main/imports.h>
+
+/**
+ * SSA-based copy propagation
+ */
+
+static bool is_move(nir_alu_instr *instr)
+{
+   if (instr->op != nir_op_fmov &&
+       instr->op != nir_op_imov)
+      return false;
+
+   if (instr->dest.saturate)
+      return false;
+
+   /* we handle modifiers in a separate pass */
+
+   if (instr->src[0].abs || instr->src[0].negate)
+      return false;
+
+   if (!instr->src[0].src.is_ssa)
+      return false;
+
+   return true;
+
+}
+
+static bool
+is_swizzleless_move(nir_alu_instr *instr)
+{
+   if (!is_move(instr))
+      return false;
+
+   for (unsigned i = 0; i < 4; i++) {
+      if (!((instr->dest.write_mask >> i) & 1))
+         break;
+      if (instr->src[0].swizzle[i] != i)
+         return false;
+   }
+
+   return true;
+}
+
+static bool is_vec(nir_alu_instr *instr)
+{
+   for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++)
+      if (!instr->src[i].src.is_ssa)
+         return false;
+
+   return instr->op == nir_op_vec2 ||
+          instr->op == nir_op_vec3 ||
+          instr->op == nir_op_vec4;
+}
+
+typedef struct {
+   nir_ssa_def *def;
+   bool found;
+} search_def_state;
+
+static bool
+search_def(nir_src *src, void *_state)
+{
+   search_def_state *state = (search_def_state *) _state;
+
+   if (src->is_ssa && src->ssa == state->def)
+      state->found = true;
+
+   return true;
+}
+
+static void
+rewrite_src_instr(nir_src *src, nir_ssa_def *new_def, nir_instr *parent_instr)
+{
+   nir_ssa_def *old_def = src->ssa;
+
+   src->ssa = new_def;
+
+   /*
+    * The instruction could still use the old definition in one of its other
+    * sources, so only remove the instruction from the uses if there are no
+    * more uses left.
+    */
+
+   search_def_state search_state;
+   search_state.def = old_def;
+   search_state.found = false;
+   nir_foreach_src(parent_instr, search_def, &search_state);
+   if (!search_state.found) {
+      struct set_entry *entry =
+         _mesa_set_search(old_def->uses, _mesa_hash_pointer(parent_instr),
+                          parent_instr);
+      assert(entry);
+      _mesa_set_remove(old_def->uses, entry);
+   }
+
+   _mesa_set_add(new_def->uses, _mesa_hash_pointer(parent_instr),
+                 parent_instr);
+}
+
+static void
+rewrite_src_if(nir_if *if_stmt, nir_ssa_def *new_def)
+{
+   nir_ssa_def *old_def = if_stmt->condition.ssa;
+
+   if_stmt->condition.ssa = new_def;
+
+   struct set_entry *entry =
+      _mesa_set_search(old_def->if_uses, _mesa_hash_pointer(if_stmt), if_stmt);
+   assert(entry);
+   _mesa_set_remove(old_def->if_uses, entry);
+
+   _mesa_set_add(new_def->if_uses, _mesa_hash_pointer(if_stmt), if_stmt);
+}
+
+static bool
+copy_prop_src(nir_src *src, nir_instr *parent_instr, nir_if *parent_if)
+{
+   if (!src->is_ssa) {
+      if (src->reg.indirect)
+         return copy_prop_src(src, parent_instr, parent_if);
+      return false;
+   }
+
+   nir_instr *src_instr = src->ssa->parent_instr;
+   if (src_instr->type != nir_instr_type_alu)
+      return false;
+
+   nir_alu_instr *alu_instr = nir_instr_as_alu(src_instr);
+   if (!is_swizzleless_move(alu_instr))
+      return false;
+
+   if (parent_instr)
+      rewrite_src_instr(src, alu_instr->src[0].src.ssa, parent_instr);
+   else
+      rewrite_src_if(parent_if, alu_instr->src[0].src.ssa);
+
+   return true;
+}
+
+static bool
+copy_prop_alu_src(nir_alu_instr *parent_alu_instr, unsigned index)
+{
+   nir_alu_src *src = &parent_alu_instr->src[index];
+   if (!src->src.is_ssa) {
+      if (src->src.reg.indirect)
+         return copy_prop_src(src->src.reg.indirect, &parent_alu_instr->instr,
+                              NULL);
+      return false;
+   }
+
+   nir_instr *src_instr =  src->src.ssa->parent_instr;
+   if (src_instr->type != nir_instr_type_alu)
+      return false;
+
+   nir_alu_instr *alu_instr = nir_instr_as_alu(src_instr);
+   if (!is_move(alu_instr) && !is_vec(alu_instr))
+      return false;
+
+   nir_ssa_def *def;
+   unsigned new_swizzle[4] = {0, 0, 0, 0};
+
+   if (alu_instr->op == nir_op_fmov ||
+       alu_instr->op == nir_op_imov) {
+      for (unsigned i = 0; i < 4; i++)
+         new_swizzle[i] = alu_instr->src[0].swizzle[src->swizzle[i]];
+      def = alu_instr->src[0].src.ssa;
+   } else {
+      def = NULL;
+
+      for (unsigned i = 0; i < 4; i++) {
+         if (!nir_alu_instr_channel_used(parent_alu_instr, index, i))
+            continue;
+
+         nir_ssa_def *new_def = alu_instr->src[src->swizzle[i]].src.ssa;
+         if (def == NULL)
+            def = new_def;
+         else {
+            if (def != new_def)
+               return false;
+         }
+         new_swizzle[i] = alu_instr->src[src->swizzle[i]].swizzle[0];
+      }
+   }
+
+   for (unsigned i = 0; i < 4; i++)
+      src->swizzle[i] = new_swizzle[i];
+
+   rewrite_src_instr(&src->src, def, &parent_alu_instr->instr);
+
+   return true;
+}
+
+typedef struct {
+   nir_instr *parent_instr;
+   bool progress;
+} copy_prop_state;
+
+static bool
+copy_prop_src_cb(nir_src *src, void *_state)
+{
+   copy_prop_state *state = (copy_prop_state *) _state;
+   while (copy_prop_src(src, state->parent_instr, NULL))
+      state->progress = true;
+
+   return true;
+}
+
+static bool
+copy_prop_instr(nir_instr *instr)
+{
+   if (instr->type == nir_instr_type_alu) {
+      nir_alu_instr *alu_instr = nir_instr_as_alu(instr);
+      bool progress = false;
+
+      for (unsigned i = 0; i < nir_op_infos[alu_instr->op].num_inputs; i++)
+         while (copy_prop_alu_src(alu_instr, i))
+            progress = true;
+
+      if (alu_instr->has_predicate)
+         while (copy_prop_src(&alu_instr->predicate, instr, NULL))
+            progress = true;
+
+      if (!alu_instr->dest.dest.is_ssa && alu_instr->dest.dest.reg.indirect)
+         while (copy_prop_src(alu_instr->dest.dest.reg.indirect, instr, NULL))
+            progress = true;
+
+      return progress;
+   }
+
+   copy_prop_state state;
+   state.parent_instr = instr;
+   state.progress = false;
+   nir_foreach_src(instr, copy_prop_src_cb, &state);
+
+   return state.progress;
+}
+
+static bool
+copy_prop_if(nir_if *if_stmt)
+{
+   return copy_prop_src(&if_stmt->condition, NULL, if_stmt);
+}
+
+static bool
+copy_prop_block(nir_block *block, void *_state)
+{
+   bool *progress = (bool *) _state;
+
+   nir_foreach_instr(block, instr) {
+      if (copy_prop_instr(instr))
+         *progress = true;
+   }
+
+   if (block->cf_node.node.next != NULL && /* check that we aren't the end node */
+       !nir_cf_node_is_last(&block->cf_node) &&
+       nir_cf_node_next(&block->cf_node)->type == nir_cf_node_if) {
+      nir_if *if_stmt = nir_cf_node_as_if(nir_cf_node_next(&block->cf_node));
+      if (copy_prop_if(if_stmt))
+         *progress = true;
+   }
+
+   return true;
+}
+
+bool
+nir_copy_prop_impl(nir_function_impl *impl)
+{
+   bool progress = false;
+
+   nir_foreach_block(impl, copy_prop_block, &progress);
+   return progress;
+}
+
+bool
+nir_copy_prop(nir_shader *shader)
+{
+   bool progress = false;
+
+   nir_foreach_overload(shader, overload) {
+      if (overload->impl && nir_copy_prop_impl(overload->impl))
+         progress = true;
+   }
+
+   return progress;
+}