glsl2: Add module to analyze variables used in loops

This is the first step eventually leading to loop unrolling.

src/glsl/loop_analysis.h

@@ -0,0 +1,190 @@
+/* -*- c++ -*- */
+/*
+ * 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.
+ */
+
+#pragma once
+#ifndef LOOP_ANALYSIS_H
+#define LOOP_ANALYSIS_H
+
+#include "ir.h"
+#include "program/hash_table.h"
+
+/**
+ * Analyze and classify all variables used in all loops in the instruction list
+ */
+extern class loop_state *
+analyze_loop_variables(exec_list *instructions);
+
+
+/**
+ * Tracking for all variables used in a loop
+ */
+class loop_variable_state : public exec_node {
+public:
+   class loop_variable *get(const ir_variable *);
+   class loop_variable *insert(ir_variable *);
+   class loop_terminator *insert(ir_if *);
+
+
+   /**
+    * Loop whose variable state is being tracked by this structure
+    */
+   ir_loop *loop;
+
+   /**
+    * Variables that have not yet been classified
+    */
+   exec_list variables;
+
+   /**
+    * Variables whose values are constant within the body of the loop
+    *
+    * This list contains \c loop_variable objects.
+    */
+   exec_list constants;
+
+   /**
+    * Induction variables for this loop
+    *
+    * This list contains \c loop_variable objects.
+    */
+   exec_list induction_variables;
+
+   /**
+    * Simple if-statements that lead to the termination of the loop
+    *
+    * This list contains \c loop_terminator objects.
+    *
+    * \sa is_loop_terminator
+    */
+   exec_list terminators;
+
+   /**
+    * Hash table containing all variables accessed in this loop
+    */
+   hash_table *var_hash;
+
+   loop_variable_state()
+   {
+      this->var_hash = hash_table_ctor(0, hash_table_pointer_hash,
+				       hash_table_pointer_compare);
+   }
+
+   ~loop_variable_state()
+   {
+      hash_table_dtor(this->var_hash);
+   }
+};
+
+
+class loop_variable : public exec_node {
+public:
+   /** The variable in question. */
+   ir_variable *var;
+
+   /** Is the variable read in the loop before it is written? */
+   bool read_before_write;
+
+   /** Are all variables in the RHS of the assignment loop constants? */
+   bool rhs_clean;
+
+   /** Is there an assignment to the variable that is conditional? */
+   bool conditional_assignment;
+
+   /** Reference to the first assignment to the variable in the loop body. */
+   ir_assignment *first_assignment;
+
+   /** Number of assignments to the variable in the loop body. */
+   unsigned num_assignments;
+
+   /**
+    * Increment values for loop induction variables
+    *
+    * Loop induction variables have a single increment of the form
+    * \c b * \c biv + \c c, where \c b and \c c are loop constants and \c i
+    * is a basic loop induction variable.
+    *
+    * If \c iv_scale is \c NULL, 1 is used.  If \c biv is the same as \c var,
+    * then \c var is a basic loop induction variable.
+    */
+   /*@{*/
+   ir_rvalue *iv_scale;
+   ir_variable *biv;
+   ir_rvalue *increment;
+   /*@}*/
+
+
+   inline bool is_loop_constant() const
+   {
+      const bool is_const = (this->num_assignments == 0)
+	 || ((this->num_assignments == 1)
+	     && !this->conditional_assignment
+	     && !this->read_before_write
+	     && this->rhs_clean);
+
+      /* If the RHS of *the* assignment is clean, then there must be exactly
+       * one assignment of the variable.
+       */
+      assert((this->rhs_clean && (this->num_assignments == 1))
+	     || !this->rhs_clean);
+
+      /* Variables that are marked read-only *MUST* be loop constant.
+       */
+      assert(!this->var->read_only || (this->var->read_only && is_const));
+
+      return is_const;
+   }
+};
+
+
+class loop_terminator : public exec_node {
+public:
+   ir_if *ir;
+};
+
+
+class loop_state {
+public:
+   ~loop_state();
+
+   /**
+    * Get the loop variable state data for a particular loop
+    */
+   loop_variable_state *get(const ir_loop *);
+
+   loop_variable_state *insert(ir_loop *ir);
+
+private:
+   loop_state();
+
+   /**
+    * Hash table containing all loops that have been analyzed.
+    */
+   hash_table *ht;
+
+   void *mem_ctx;
+
+   friend class loop_analysis;
+};
+
+#endif /* LOOP_ANALYSIS_H */