1 files changed, 348 insertions, 0 deletions

diff --git a/mesalib/src/glsl/ir_copy_propagation.cpp b/mesalib/src/glsl/ir_copy_propagation.cpp
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index 000000000..0fe8fa6c4
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+++ b/mesalib/src/glsl/ir_copy_propagation.cpp
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+/*
+ * 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_copy_propagation.cpp
+ *
+ * Moves usage of recently-copied variables to the previous copy of
+ * the variable.
+ *
+ * This should reduce the number of MOV instructions in the generated
+ * programs unless copy propagation is also done on the LIR, and may
+ * help anyway by triggering other optimizations that live in the HIR.
+ */
+
+#include "ir.h"
+#include "ir_visitor.h"
+#include "ir_basic_block.h"
+#include "ir_optimization.h"
+#include "glsl_types.h"
+
+class acp_entry : public exec_node
+{
+public:
+   acp_entry(ir_variable *lhs, ir_variable *rhs)
+   {
+      assert(lhs);
+      assert(rhs);
+      this->lhs = lhs;
+      this->rhs = rhs;
+   }
+
+   ir_variable *lhs;
+   ir_variable *rhs;
+};
+
+
+class kill_entry : public exec_node
+{
+public:
+   kill_entry(ir_variable *var)
+   {
+      assert(var);
+      this->var = var;
+   }
+
+   ir_variable *var;
+};
+
+class ir_copy_propagation_visitor : public ir_hierarchical_visitor {
+public:
+   ir_copy_propagation_visitor()
+   {
+      progress = false;
+      mem_ctx = talloc_new(0);
+      this->acp = new(mem_ctx) exec_list;
+      this->kills = new(mem_ctx) exec_list;
+   }
+   ~ir_copy_propagation_visitor()
+   {
+      talloc_free(mem_ctx);
+   }
+
+   virtual ir_visitor_status visit(class ir_dereference_variable *);
+   virtual ir_visitor_status visit_enter(class ir_loop *);
+   virtual ir_visitor_status visit_enter(class ir_function_signature *);
+   virtual ir_visitor_status visit_enter(class ir_function *);
+   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_if *);
+
+   void add_copy(ir_assignment *ir);
+   void kill(ir_variable *ir);
+   void handle_if_block(exec_list *instructions);
+
+   /** List of acp_entry: The available copies to propagate */
+   exec_list *acp;
+   /**
+    * List of kill_entry: The variables whose values were killed in this
+    * block.
+    */
+   exec_list *kills;
+
+   bool progress;
+
+   bool killed_all;
+
+   void *mem_ctx;
+};
+
+ir_visitor_status
+ir_copy_propagation_visitor::visit_enter(ir_function_signature *ir)
+{
+   /* Treat entry into a function signature as a completely separate
+    * block.  Any instructions at global scope will be shuffled into
+    * main() at link time, so they're irrelevant to us.
+    */
+   exec_list *orig_acp = this->acp;
+   exec_list *orig_kills = this->kills;
+   bool orig_killed_all = this->killed_all;
+
+   this->acp = new(mem_ctx) exec_list;
+   this->kills = new(mem_ctx) exec_list;
+   this->killed_all = false;
+
+   visit_list_elements(this, &ir->body);
+
+   this->kills = orig_kills;
+   this->acp = orig_acp;
+   this->killed_all = orig_killed_all;
+
+   return visit_continue_with_parent;
+}
+
+ir_visitor_status
+ir_copy_propagation_visitor::visit_leave(ir_assignment *ir)
+{
+   kill(ir->lhs->variable_referenced());
+
+   add_copy(ir);
+
+   return visit_continue;
+}
+
+ir_visitor_status
+ir_copy_propagation_visitor::visit_enter(ir_function *ir)
+{
+   (void) ir;
+   return visit_continue;
+}
+
+/**
+ * Replaces dereferences of ACP RHS variables with ACP LHS variables.
+ *
+ * This is where the actual copy propagation occurs.  Note that the
+ * rewriting of ir_dereference means that the ir_dereference instance
+ * must not be shared by multiple IR operations!
+ */
+ir_visitor_status
+ir_copy_propagation_visitor::visit(ir_dereference_variable *ir)
+{
+   if (this->in_assignee)
+      return visit_continue;
+
+   ir_variable *var = ir->var;
+
+   foreach_iter(exec_list_iterator, iter, *this->acp) {
+      acp_entry *entry = (acp_entry *)iter.get();
+
+      if (var == entry->lhs) {
+	 ir->var = entry->rhs;
+	 this->progress = true;
+	 break;
+      }
+   }
+
+   return visit_continue;
+}
+
+
+ir_visitor_status
+ir_copy_propagation_visitor::visit_enter(ir_call *ir)
+{
+   /* Do copy propagation on call parameters, but skip any out params */
+   exec_list_iterator sig_param_iter = ir->get_callee()->parameters.iterator();
+   foreach_iter(exec_list_iterator, iter, ir->actual_parameters) {
+      ir_variable *sig_param = (ir_variable *)sig_param_iter.get();
+      ir_instruction *ir = (ir_instruction *)iter.get();
+      if (sig_param->mode != ir_var_out && sig_param->mode != ir_var_inout) {
+         ir->accept(this);
+      }
+      sig_param_iter.next();
+   }
+
+   /* Since we're unlinked, we don't (necssarily) know the side effects of
+    * this call.  So kill all copies.
+    */
+   acp->make_empty();
+   this->killed_all = true;
+
+   return visit_continue_with_parent;
+}
+
+void
+ir_copy_propagation_visitor::handle_if_block(exec_list *instructions)
+{
+   exec_list *orig_acp = this->acp;
+   exec_list *orig_kills = this->kills;
+   bool orig_killed_all = this->killed_all;
+
+   this->acp = new(mem_ctx) exec_list;
+   this->kills = new(mem_ctx) exec_list;
+   this->killed_all = false;
+
+   /* Populate the initial acp with a copy of the original */
+   foreach_iter(exec_list_iterator, iter, *orig_acp) {
+      acp_entry *a = (acp_entry *)iter.get();
+      this->acp->push_tail(new(this->mem_ctx) acp_entry(a->lhs, a->rhs));
+   }
+
+   visit_list_elements(this, instructions);
+
+   if (this->killed_all) {
+      orig_acp->make_empty();
+   }
+
+   exec_list *new_kills = this->kills;
+   this->kills = orig_kills;
+   this->acp = orig_acp;
+   this->killed_all = this->killed_all || orig_killed_all;
+
+   foreach_iter(exec_list_iterator, iter, *new_kills) {
+      kill_entry *k = (kill_entry *)iter.get();
+      kill(k->var);
+   }
+}
+
+ir_visitor_status
+ir_copy_propagation_visitor::visit_enter(ir_if *ir)
+{
+   ir->condition->accept(this);
+
+   handle_if_block(&ir->then_instructions);
+   handle_if_block(&ir->else_instructions);
+
+   /* handle_if_block() already descended into the children. */
+   return visit_continue_with_parent;
+}
+
+ir_visitor_status
+ir_copy_propagation_visitor::visit_enter(ir_loop *ir)
+{
+   exec_list *orig_acp = this->acp;
+   exec_list *orig_kills = this->kills;
+   bool orig_killed_all = this->killed_all;
+
+   /* FINISHME: For now, the initial acp for loops is totally empty.
+    * We could go through once, then go through again with the acp
+    * cloned minus the killed entries after the first run through.
+    */
+   this->acp = new(mem_ctx) exec_list;
+   this->kills = new(mem_ctx) exec_list;
+   this->killed_all = false;
+
+   visit_list_elements(this, &ir->body_instructions);
+
+   if (this->killed_all) {
+      orig_acp->make_empty();
+   }
+
+   exec_list *new_kills = this->kills;
+   this->kills = orig_kills;
+   this->acp = orig_acp;
+   this->killed_all = this->killed_all || orig_killed_all;
+
+   foreach_iter(exec_list_iterator, iter, *new_kills) {
+      kill_entry *k = (kill_entry *)iter.get();
+      kill(k->var);
+   }
+
+   /* already descended into the children. */
+   return visit_continue_with_parent;
+}
+
+void
+ir_copy_propagation_visitor::kill(ir_variable *var)
+{
+   assert(var != NULL);
+
+   /* Remove any entries currently in the ACP for this kill. */
+   foreach_iter(exec_list_iterator, iter, *acp) {
+      acp_entry *entry = (acp_entry *)iter.get();
+
+      if (entry->lhs == var || entry->rhs == var) {
+	 entry->remove();
+      }
+   }
+
+   /* Add the LHS variable to the list of killed variables in this block.
+    */
+   this->kills->push_tail(new(this->mem_ctx) kill_entry(var));
+}
+
+/**
+ * Adds an entry to the available copy list if it's a plain assignment
+ * of a variable to a variable.
+ */
+void
+ir_copy_propagation_visitor::add_copy(ir_assignment *ir)
+{
+   acp_entry *entry;
+
+   if (ir->condition) {
+      ir_constant *condition = ir->condition->as_constant();
+      if (!condition || !condition->value.b[0])
+	 return;
+   }
+
+   ir_variable *lhs_var = ir->whole_variable_written();
+   ir_variable *rhs_var = ir->rhs->whole_variable_referenced();
+
+   if ((lhs_var != NULL) && (rhs_var != NULL)) {
+      if (lhs_var == rhs_var) {
+	 /* This is a dumb assignment, but we've conveniently noticed
+	  * it here.  Removing it now would mess up the loop iteration
+	  * calling us.  Just flag it to not execute, and someone else
+	  * will clean up the mess.
+	  */
+	 ir->condition = new(talloc_parent(ir)) ir_constant(false);
+	 this->progress = true;
+      } else {
+	 entry = new(this->mem_ctx) acp_entry(lhs_var, rhs_var);
+	 this->acp->push_tail(entry);
+      }
+   }
+}
+
+/**
+ * Does a copy propagation pass on the code present in the instruction stream.
+ */
+bool
+do_copy_propagation(exec_list *instructions)
+{
+   ir_copy_propagation_visitor v;
+
+   visit_list_elements(&v, instructions);
+
+   return v.progress;
+}