glsl2: Add new tree grafting optimization pass.

1 files changed, 356 insertions, 0 deletions

diff --git a/src/glsl/ir_tree_grafting.cpp b/src/glsl/ir_tree_grafting.cpp
new file mode 100644
index 00000000000..6f62de758b2
--- /dev/null
+++ b/src/glsl/ir_tree_grafting.cpp
@@ -0,0 +1,356 @@
+/*
+ * Copyright © 2010 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.
+ */
+
+/**
+ * \file ir_tree_grafting.cpp
+ *
+ * Takes assignments to variables that are dereferenced only once and
+ * pastes the RHS expression into where the variable is dereferenced.
+ *
+ * In the process of various operations like function inlining and
+ * tertiary op handling, we'll end up with our expression trees having
+ * been chopped up into a series of assignments of short expressions
+ * to temps.  Other passes like ir_algebraic.cpp would prefer to see
+ * the deepest expression trees they can to try to optimize them.
+ *
+ * This is a lot like copy propagaton.  In comparison, copy
+ * propagation only acts on plain copies, not arbitrary expressions on
+ * the RHS.  Generally, we wouldn't want to go pasting some
+ * complicated expression everywhere it got used, though, so we don't
+ * handle expressions in that pass.
+ *
+ * The hard part is making sure we don't move an expression across
+ * some other assignments that would change the value of the
+ * expression.  So we split this into two passes: First, find the
+ * variables in our scope which are written to once and read once, and
+ * then go through basic blocks seeing if we find an opportunity to
+ * move those expressions safely.
+ */
+
+#include "ir.h"
+#include "ir_visitor.h"
+#include "ir_variable_refcount.h"
+#include "ir_basic_block.h"
+#include "ir_optimization.h"
+#include "glsl_types.h"
+
+static bool debug = false;
+
+class ir_tree_grafting_visitor : public ir_hierarchical_visitor {
+public:
+   ir_tree_grafting_visitor(ir_assignment *graft_assign,
+			    ir_variable *graft_var)
+   {
+      this->progress = false;
+      this->graft_assign = graft_assign;
+      this->graft_var = graft_var;
+   }
+
+   virtual ir_visitor_status visit_leave(class ir_assignment *);
+   virtual ir_visitor_status visit_enter(class ir_call *);
+   virtual ir_visitor_status visit_enter(class ir_expression *);
+   virtual ir_visitor_status visit_enter(class ir_function *);
+   virtual ir_visitor_status visit_enter(class ir_function_signature *);
+   virtual ir_visitor_status visit_enter(class ir_if *);
+   virtual ir_visitor_status visit_enter(class ir_loop *);
+   virtual ir_visitor_status visit_enter(class ir_swizzle *);
+   virtual ir_visitor_status visit_enter(class ir_texture *);
+
+   bool do_graft(ir_rvalue **rvalue);
+
+   bool progress;
+   ir_variable *graft_var;
+   ir_assignment *graft_assign;
+};
+
+struct find_deref_info {
+   ir_variable *var;
+   bool found;
+};
+
+void
+dereferences_variable_callback(ir_instruction *ir, void *data)
+{
+   struct find_deref_info *info = (struct find_deref_info *)data;
+
+   if (ir == info->var)
+      info->found = true;
+}
+
+static bool
+dereferences_variable(ir_instruction *ir, ir_variable *var)
+{
+   struct find_deref_info info;
+
+   info.var = var;
+   info.found = false;
+
+   visit_tree(ir, dereferences_variable_callback, &info);
+
+   return info.found;
+}
+
+bool
+ir_tree_grafting_visitor::do_graft(ir_rvalue **rvalue)
+{
+   if (!*rvalue)
+      return false;
+
+   ir_dereference_variable *deref = (*rvalue)->as_dereference_variable();
+
+   if (!deref || deref->var != this->graft_var)
+      return false;
+
+   if (debug) {
+      printf("GRAFTING:\n");
+      this->graft_assign->rhs->print();
+      printf("\n");
+      printf("TO:\n");
+      (*rvalue)->print();
+      printf("\n");
+   }
+
+   this->graft_assign->remove();
+   *rvalue = this->graft_assign->rhs;
+
+   this->progress = true;
+   return true;
+}
+
+ir_visitor_status
+ir_tree_grafting_visitor::visit_enter(ir_loop *ir)
+{
+   (void)ir;
+   /* Do not traverse into the body of the loop since that is a
+    * different basic block.
+    */
+   return visit_stop;
+}
+
+ir_visitor_status
+ir_tree_grafting_visitor::visit_leave(ir_assignment *ir)
+{
+   if (do_graft(&ir->rhs) ||
+       do_graft(&ir->condition))
+      return visit_stop;
+
+   /* If this assignment updates a variable used in the assignment
+    * we're trying to graft, then we're done.
+    */
+   if (dereferences_variable(this->graft_assign->rhs,
+			     ir->lhs->variable_referenced())) {
+      if (debug) {
+	 printf("graft killed by: ");
+	 ir->print();
+	 printf("\n");
+      }
+      return visit_stop;
+   }
+
+   return visit_continue;
+}
+
+ir_visitor_status
+ir_tree_grafting_visitor::visit_enter(ir_function *ir)
+{
+   (void) ir;
+   return visit_continue_with_parent;
+}
+
+ir_visitor_status
+ir_tree_grafting_visitor::visit_enter(ir_function_signature *ir)
+{
+   (void)ir;
+   return visit_continue_with_parent;
+}
+
+ir_visitor_status
+ir_tree_grafting_visitor::visit_enter(ir_call *ir)
+{
+   /* Reminder: iterating ir_call iterates its parameters. */
+   foreach_iter(exec_list_iterator, iter, *ir) {
+      ir_rvalue *ir = (ir_rvalue *)iter.get();
+      ir_rvalue *new_ir = ir;
+
+      if (do_graft(&new_ir)) {
+	 ir->replace_with(new_ir);
+	 return visit_stop;
+      }
+   }
+
+   return visit_continue;
+}
+
+ir_visitor_status
+ir_tree_grafting_visitor::visit_enter(ir_expression *ir)
+{
+   for (unsigned int i = 0; i < ir->get_num_operands(); i++) {
+      if (do_graft(&ir->operands[i]))
+	 return visit_stop;
+   }
+
+   return visit_continue;
+}
+
+ir_visitor_status
+ir_tree_grafting_visitor::visit_enter(ir_if *ir)
+{
+   if (do_graft(&ir->condition))
+      return visit_stop;
+
+   /* Do not traverse into the body of the if-statement since that is a
+    * different basic block.
+    */
+   return visit_continue_with_parent;
+}
+
+ir_visitor_status
+ir_tree_grafting_visitor::visit_enter(ir_swizzle *ir)
+{
+   if (do_graft(&ir->val))
+      return visit_stop;
+
+   return visit_continue;
+}
+
+ir_visitor_status
+ir_tree_grafting_visitor::visit_enter(ir_texture *ir)
+{
+   if (do_graft(&ir->coordinate) ||
+       do_graft(&ir->projector) ||
+       do_graft(&ir->shadow_comparitor))
+	 return visit_stop;
+
+   switch (ir->op) {
+   case ir_tex:
+      break;
+   case ir_txb:
+      if (do_graft(&ir->lod_info.bias))
+	 return visit_stop;
+      break;
+   case ir_txf:
+   case ir_txl:
+      if (do_graft(&ir->lod_info.lod))
+	 return visit_stop;
+      break;
+   case ir_txd:
+      if (do_graft(&ir->lod_info.grad.dPdx) ||
+	  do_graft(&ir->lod_info.grad.dPdy))
+	 return visit_stop;
+      break;
+   }
+
+   return visit_continue;
+}
+
+struct tree_grafting_info {
+   ir_variable_refcount_visitor *refs;
+   bool progress;
+};
+
+static bool
+try_tree_grafting(ir_assignment *start,
+		  ir_variable *lhs_var,
+		  ir_instruction *bb_last)
+{
+   ir_tree_grafting_visitor v(start, lhs_var);
+
+   if (debug) {
+      printf("trying to graft: ");
+      lhs_var->print();
+      printf("\n");
+   }
+
+   for (ir_instruction *ir = (ir_instruction *)start->next;
+	ir != bb_last->next;
+	ir = (ir_instruction *)ir->next) {
+
+      if (debug) {
+	 printf("- ");
+	 ir->print();
+	 printf("\n");
+      }
+
+      ir_visitor_status s = ir->accept(&v);
+      if (s == visit_stop)
+	 return v.progress;
+   }
+
+   return false;
+}
+
+static void
+tree_grafting_basic_block(ir_instruction *bb_first,
+			  ir_instruction *bb_last,
+			  void *data)
+{
+   struct tree_grafting_info *info = (struct tree_grafting_info *)data;
+   ir_instruction *ir, *next;
+
+   for (ir = bb_first, next = (ir_instruction *)ir->next;
+	ir != bb_last->next;
+	ir = next, next = (ir_instruction *)ir->next) {
+      ir_assignment *assign = ir->as_assignment();
+
+      if (!assign)
+	 continue;
+
+      ir_variable *lhs_var = assign->lhs->whole_variable_referenced();
+      if (!lhs_var)
+	 continue;
+
+      struct variable_entry *entry = info->refs->get_variable_entry(lhs_var);
+
+      if (!entry->declaration ||
+	  entry->assigned_count != 1 ||
+	  entry->referenced_count != 2)
+	 continue;
+
+      assert(assign == entry->assign);
+
+      /* Found a possibly graftable assignment.  Now, walk through the
+       * rest of the BB seeing if the deref is here, and if nothing interfered with
+       * pasting its expression's values in between.
+       */
+      info->progress |= try_tree_grafting(assign, lhs_var, bb_last);
+   }
+}
+
+/**
+ * Does a copy propagation pass on the code present in the instruction stream.
+ */
+bool
+do_tree_grafting(exec_list *instructions)
+{
+   ir_variable_refcount_visitor refs;
+   struct tree_grafting_info info;
+
+   info.progress = false;
+   info.refs = &refs;
+
+   visit_list_elements(info.refs, instructions);
+
+   call_for_basic_blocks(instructions, tree_grafting_basic_block, &info);
+
+   return info.progress;
+}