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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.

 *

 * Authors:

 *    Eric Anholt 

 *

 */

/** @file register_allocate.c

 *

 * Graph-coloring register allocator.

 */

#include 

#include "main/imports.h"

#include "main/macros.h"

#include "main/mtypes.h"

#include "register_allocate.h"

struct ra_reg {

   char *name;

   GLboolean *conflicts;

};

struct ra_regs {

   struct ra_reg *regs;

   unsigned int count;

   struct ra_class **classes;

   unsigned int class_count;

};

struct ra_class {

   GLboolean *regs;

   /**

    * p_B in Runeson/Nyström paper.

    *

    * This is "how many regs are in the set."

    */

   unsigned int p;

   /**

    * q_B,C in Runeson/Nyström paper.

    */

   unsigned int *q;

};

struct ra_node {

   GLboolean *adjacency;

   unsigned int class;

   unsigned int adjacency_count;

   unsigned int reg;

   GLboolean in_stack;

   float spill_cost;

};

struct ra_graph {

   struct ra_regs *regs;

   /**

    * the variables that need register allocation.

    */

   struct ra_node *nodes;

   unsigned int count; /**< count of nodes. */

   unsigned int *stack;

   unsigned int stack_count;

};

struct ra_regs *

ra_alloc_reg_set(unsigned int count)

{

   unsigned int i;

   struct ra_regs *regs;

   regs = rzalloc(NULL, struct ra_regs);

   regs->count = count;

   regs->regs = rzalloc_array(regs, struct ra_reg, count);

   for (i = 0; i < count; i++) {

      regs->regs[i].conflicts = rzalloc_array(regs->regs, GLboolean, count);

      regs->regs[i].conflicts[i] = GL_TRUE;

   }

   return regs;

}

void

ra_add_reg_conflict(struct ra_regs *regs, unsigned int r1, unsigned int r2)

{

   regs->regs[r1].conflicts[r2] = GL_TRUE;

   regs->regs[r2].conflicts[r1] = GL_TRUE;

}

unsigned int

ra_alloc_reg_class(struct ra_regs *regs)

{

   struct ra_class *class;

   regs->classes = reralloc(regs->regs, regs->classes, struct ra_class *,

			    regs->class_count + 1);

   class = rzalloc(regs, struct ra_class);

   regs->classes[regs->class_count] = class;

   class->regs = rzalloc_array(class, GLboolean, regs->count);

   return regs->class_count++;

}

void

ra_class_add_reg(struct ra_regs *regs, unsigned int c, unsigned int r)

{

   struct ra_class *class = regs->classes[c];

   class->regs[r] = GL_TRUE;

   class->p++;

}

/**

 * Must be called after all conflicts and register classes have been

 * set up and before the register set is used for allocation.

 */

void

ra_set_finalize(struct ra_regs *regs)

{

   unsigned int b, c;

   for (b = 0; b < regs->class_count; b++) {

      regs->classes[b]->q = ralloc_array(regs, unsigned int, regs->class_count);

   }

   /* Compute, for each class B and C, how many regs of B an

    * allocation to C could conflict with.

    */

   for (b = 0; b < regs->class_count; b++) {

      for (c = 0; c < regs->class_count; c++) {

	 unsigned int rc;

	 int max_conflicts = 0;

	 for (rc = 0; rc < regs->count; rc++) {

	    unsigned int rb;

	    int conflicts = 0;

	    if (!regs->classes[c]->regs[rc])

	       continue;

	    for (rb = 0; rb < regs->count; rb++) {

	       if (regs->classes[b]->regs[rb] &&

		   regs->regs[rb].conflicts[rc])

		  conflicts++;

	    }

	    max_conflicts = MAX2(max_conflicts, conflicts);

	 }

	 regs->classes[b]->q[c] = max_conflicts;

      }

   }

}

struct ra_graph *

ra_alloc_interference_graph(struct ra_regs *regs, unsigned int count)

{

   struct ra_graph *g;

   unsigned int i;

   g = rzalloc(regs, struct ra_graph);

   g->regs = regs;

   g->nodes = rzalloc_array(g, struct ra_node, count);

   g->count = count;

   g->stack = rzalloc_array(g, unsigned int, count);

   for (i = 0; i < count; i++) {

      g->nodes[i].adjacency = rzalloc_array(g, GLboolean, count);

      g->nodes[i].adjacency[i] = GL_TRUE;

      g->nodes[i].reg = ~0;

   }

   return g;

}

void

ra_set_node_class(struct ra_graph *g,

		  unsigned int n, unsigned int class)

{

   g->nodes[n].class = class;

}

void

ra_add_node_interference(struct ra_graph *g,

			 unsigned int n1, unsigned int n2)

{

   if (g->nodes[n1].adjacency[n2])

      return;

   g->nodes[n1].adjacency[n2] = GL_TRUE;

   g->nodes[n2].adjacency_count++;

   g->nodes[n2].adjacency[n1] = GL_TRUE;

   g->nodes[n2].adjacency_count++;

}

static GLboolean pq_test(struct ra_graph *g, unsigned int n)

{

   unsigned int j;

   unsigned int q = 0;

   int n_class = g->nodes[n].class;

   for (j = 0; j < g->count; j++) {

      if (j == n || g->nodes[j].in_stack)

	 continue;

      if (g->nodes[n].adjacency[j]) {

	 unsigned int j_class = g->nodes[j].class;

	 q += g->regs->classes[n_class]->q[j_class];

      }

   }

   return q < g->regs->classes[n_class]->p;

}

/**

 * Simplifies the interference graph by pushing all

 * trivially-colorable nodes into a stack of nodes to be colored,

 * removing them from the graph, and rinsing and repeating.

 *

 * Returns GL_TRUE if all nodes were removed from the graph.  GL_FALSE

 * means that either spilling will be required, or optimistic coloring

 * should be applied.

 */

GLboolean

ra_simplify(struct ra_graph *g)

{

   GLboolean progress = GL_TRUE;

   int i;

   while (progress) {

      progress = GL_FALSE;

      for (i = g->count - 1; i >= 0; i--) {

	 if (g->nodes[i].in_stack)

	    continue;

	 if (pq_test(g, i)) {

	    g->stack[g->stack_count] = i;

	    g->stack_count++;

	    g->nodes[i].in_stack = GL_TRUE;

	    progress = GL_TRUE;

	 }

      }

   }

   for (i = 0; i < g->count; i++) {

      if (!g->nodes[i].in_stack)

	 return GL_FALSE;

   }

   return GL_TRUE;

}

/**

 * Pops nodes from the stack back into the graph, coloring them with

 * registers as they go.

 *

 * If all nodes were trivially colorable, then this must succeed.  If

 * not (optimistic coloring), then it may return GL_FALSE;

 */

GLboolean

ra_select(struct ra_graph *g)

{

   int i;

   while (g->stack_count != 0) {

      unsigned int r;

      int n = g->stack[g->stack_count - 1];

      struct ra_class *c = g->regs->classes[g->nodes[n].class];

      /* Find the lowest-numbered reg which is not used by a member

       * of the graph adjacent to us.

       */

      for (r = 0; r < g->regs->count; r++) {

	 if (!c->regs[r])

	    continue;

	 /* Check if any of our neighbors conflict with this register choice. */

	 for (i = 0; i < g->count; i++) {

	    if (g->nodes[n].adjacency[i] &&

	       !g->nodes[i].in_stack &&

		g->regs->regs[r].conflicts[g->nodes[i].reg]) {

	       break;

	    }

	 }

	 if (i == g->count)

	    break;

      }

      if (r == g->regs->count)

	 return GL_FALSE;

      g->nodes[n].reg = r;

      g->nodes[n].in_stack = GL_FALSE;

      g->stack_count--;

   }

   return GL_TRUE;

}

/**

 * Optimistic register coloring: Just push the remaining nodes

 * on the stack.  They'll be colored first in ra_select(), and

 * if they succeed then the locally-colorable nodes are still

 * locally-colorable and the rest of the register allocation

 * will succeed.

 */

void

ra_optimistic_color(struct ra_graph *g)

{

   unsigned int i;

   for (i = 0; i < g->count; i++) {

      if (g->nodes[i].in_stack)

	 continue;

      g->stack[g->stack_count] = i;

      g->stack_count++;

      g->nodes[i].in_stack = GL_TRUE;

   }

}

GLboolean

ra_allocate_no_spills(struct ra_graph *g)

{

   if (!ra_simplify(g)) {

      ra_optimistic_color(g);

   }

   return ra_select(g);

}

unsigned int

ra_get_node_reg(struct ra_graph *g, unsigned int n)

{

   return g->nodes[n].reg;

}

static float

ra_get_spill_benefit(struct ra_graph *g, unsigned int n)

{

   int j;

   float benefit = 0;

   int n_class = g->nodes[n].class;

   /* Define the benefit of eliminating an interference between n, j

    * through spilling as q(C, B) / p(C).  This is similar to the

    * "count number of edges" approach of traditional graph coloring,

    * but takes classes into account.

    */

   for (j = 0; j < g->count; j++) {

      if (j != n && g->nodes[n].adjacency[j]) {

	 unsigned int j_class = g->nodes[j].class;

	 benefit += ((float)g->regs->classes[n_class]->q[j_class] /

		     g->regs->classes[n_class]->p);

	 break;

      }

   }

   return benefit;

}

/**

 * Returns a node number to be spilled according to the cost/benefit using

 * the pq test, or -1 if there are no spillable nodes.

 */

int

ra_get_best_spill_node(struct ra_graph *g)

{

   unsigned int best_node = -1;

   unsigned int best_benefit = 0.0;

   unsigned int n;

   for (n = 0; n < g->count; n++) {

      float cost = g->nodes[n].spill_cost;

      float benefit;

      if (cost <= 0.0)

	 continue;

      benefit = ra_get_spill_benefit(g, n);

      if (benefit / cost > best_benefit) {

	 best_benefit = benefit / cost;

	 best_node = n;

      }

   }

   return best_node;

}

/**

 * Only nodes with a spill cost set (cost != 0.0) will be considered

 * for register spilling.

 */

void

ra_set_node_spill_cost(struct ra_graph *g, unsigned int n, float cost)

{

   g->nodes[n].spill_cost = cost;

}