532 lines
15 KiB
C
532 lines
15 KiB
C
/* Register conflict graph computation routines.
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Copyright (C) 2000 Free Software Foundation, Inc.
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Contributed by CodeSourcery, LLC
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 2, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING. If not, write to the Free
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Software Foundation, 59 Temple Place - Suite 330, Boston, MA
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02111-1307, USA. */
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/* References:
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Building an Optimizing Compiler
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Robert Morgan
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Butterworth-Heinemann, 1998 */
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#include "config.h"
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#include "system.h"
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#include "obstack.h"
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#include "hashtab.h"
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#include "rtl.h"
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#include "hard-reg-set.h"
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#include "basic-block.h"
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/* Use malloc to allocate obstack chunks. */
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#define obstack_chunk_alloc xmalloc
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#define obstack_chunk_free free
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/* A register conflict graph is an undirected graph containing nodes
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for some or all of the regs used in a function. Arcs represent
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conflicts, i.e. two nodes are connected by an arc if there is a
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point in the function at which the regs corresponding to the two
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nodes are both live.
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The conflict graph is represented by the data structures described
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in Morgan section 11.3.1. Nodes are not stored explicitly; only
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arcs are. An arc stores the numbers of the regs it connects.
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Arcs can be located by two methods:
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- The two reg numbers for each arc are hashed into a single
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value, and the arc is placed in a hash table according to this
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value. This permits quick determination of whether a specific
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conflict is present in the graph.
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- Additionally, the arc data structures are threaded by a set of
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linked lists by single reg number. Since each arc references
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two regs, there are two next pointers, one for the
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smaller-numbered reg and one for the larger-numbered reg. This
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permits the quick enumeration of conflicts for a single
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register.
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Arcs are allocated from an obstack. */
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/* An arc in a conflict graph. */
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struct conflict_graph_arc_def
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{
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/* The next element of the list of conflicts involving the
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smaller-numbered reg, as an index in the table of arcs of this
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graph. Contains NULL if this is the tail. */
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struct conflict_graph_arc_def *smaller_next;
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/* The next element of the list of conflicts involving the
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larger-numbered reg, as an index in the table of arcs of this
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graph. Contains NULL if this is the tail. */
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struct conflict_graph_arc_def *larger_next;
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/* The smaller-numbered reg involved in this conflict. */
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int smaller;
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/* The larger-numbered reg involved in this conflict. */
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int larger;
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};
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typedef struct conflict_graph_arc_def *conflict_graph_arc;
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typedef const struct conflict_graph_arc_def *const_conflict_graph_arc;
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/* A conflict graph. */
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struct conflict_graph_def
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{
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/* A hash table of arcs. Used to search for a specific conflict. */
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htab_t arc_hash_table;
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/* The number of regs this conflict graph handles. */
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int num_regs;
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/* For each reg, the arc at the head of a list that threads through
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all the arcs involving that reg. An entry is NULL if no
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conflicts exist involving that reg. */
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conflict_graph_arc *neighbor_heads;
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/* Arcs are allocated from here. */
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struct obstack arc_obstack;
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};
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/* The initial capacity (number of conflict arcs) for newly-created
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conflict graphs. */
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#define INITIAL_ARC_CAPACITY 64
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/* Computes the hash value of the conflict graph arc connecting regs
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R1 and R2. R1 is assumed to be smaller or equal to R2. */
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#define CONFLICT_HASH_FN(R1, R2) ((R2) * ((R2) - 1) / 2 + (R1))
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static unsigned arc_hash PARAMS ((const void *));
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static int arc_eq PARAMS ((const void *, const void *));
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static int print_conflict PARAMS ((int, int, void *));
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static void mark_reg PARAMS ((rtx, rtx, void *));
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/* Callback function to compute the hash value of an arc. Uses
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current_graph to locate the graph to which the arc belongs. */
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static unsigned
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arc_hash (arcp)
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const void *arcp;
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{
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const_conflict_graph_arc arc = (const_conflict_graph_arc) arcp;
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return CONFLICT_HASH_FN (arc->smaller, arc->larger);
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}
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/* Callback function to determine the equality of two arcs in the hash
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table. */
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static int
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arc_eq (arcp1, arcp2)
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const void *arcp1;
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const void *arcp2;
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{
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const_conflict_graph_arc arc1 = (const_conflict_graph_arc) arcp1;
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const_conflict_graph_arc arc2 = (const_conflict_graph_arc) arcp2;
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return arc1->smaller == arc2->smaller && arc1->larger == arc2->larger;
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}
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/* Creates an empty conflict graph to hold conflicts among NUM_REGS
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registers. */
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conflict_graph
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conflict_graph_new (num_regs)
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int num_regs;
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{
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conflict_graph graph
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= (conflict_graph) xmalloc (sizeof (struct conflict_graph_def));
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graph->num_regs = num_regs;
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/* Set up the hash table. No delete action is specified; memory
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management of arcs is through the obstack. */
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graph->arc_hash_table
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= htab_create (INITIAL_ARC_CAPACITY, &arc_hash, &arc_eq, NULL);
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/* Create an obstack for allocating arcs. */
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obstack_init (&graph->arc_obstack);
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/* Create and zero the lookup table by register number. */
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graph->neighbor_heads
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= (conflict_graph_arc *) xmalloc (num_regs * sizeof (conflict_graph_arc));
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memset (graph->neighbor_heads, 0, num_regs * sizeof (conflict_graph_arc));
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return graph;
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}
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/* Deletes a conflict graph. */
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void
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conflict_graph_delete (graph)
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conflict_graph graph;
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{
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obstack_free (&graph->arc_obstack, NULL);
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htab_delete (graph->arc_hash_table);
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free (graph->neighbor_heads);
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free (graph);
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}
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/* Adds a conflict to GRAPH between regs REG1 and REG2, which must be
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distinct. Returns non-zero, unless the conflict is already present
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in GRAPH, in which case it does nothing and returns zero. */
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int
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conflict_graph_add (graph, reg1, reg2)
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conflict_graph graph;
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int reg1;
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int reg2;
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{
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int smaller = MIN (reg1, reg2);
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int larger = MAX (reg1, reg2);
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struct conflict_graph_arc_def dummy;
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conflict_graph_arc arc;
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void **slot;
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/* A reg cannot conflict with itself. */
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if (reg1 == reg2)
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abort ();
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dummy.smaller = smaller;
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dummy.larger = larger;
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slot = htab_find_slot (graph->arc_hash_table, (void *) &dummy, INSERT);
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/* If the conflict is already there, do nothing. */
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if (*slot != NULL)
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return 0;
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/* Allocate an arc. */
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arc
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= (conflict_graph_arc)
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obstack_alloc (&graph->arc_obstack,
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sizeof (struct conflict_graph_arc_def));
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/* Record the reg numbers. */
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arc->smaller = smaller;
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arc->larger = larger;
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/* Link the conflict into into two lists, one for each reg. */
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arc->smaller_next = graph->neighbor_heads[smaller];
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graph->neighbor_heads[smaller] = arc;
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arc->larger_next = graph->neighbor_heads[larger];
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graph->neighbor_heads[larger] = arc;
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/* Put it in the hash table. */
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*slot = (void *) arc;
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return 1;
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}
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/* Returns non-zero if a conflict exists in GRAPH between regs REG1
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and REG2. */
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int
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conflict_graph_conflict_p (graph, reg1, reg2)
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conflict_graph graph;
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int reg1;
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int reg2;
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{
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/* Build an arc to search for. */
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struct conflict_graph_arc_def arc;
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arc.smaller = MIN (reg1, reg2);
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arc.larger = MAX (reg1, reg2);
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return htab_find (graph->arc_hash_table, (void *) &arc) != NULL;
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}
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/* Calls ENUM_FN for each conflict in GRAPH involving REG. EXTRA is
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passed back to ENUM_FN. */
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void
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conflict_graph_enum (graph, reg, enum_fn, extra)
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conflict_graph graph;
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int reg;
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conflict_graph_enum_fn enum_fn;
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void *extra;
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{
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conflict_graph_arc arc = graph->neighbor_heads[reg];
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while (arc != NULL)
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{
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/* Invoke the callback. */
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if ((*enum_fn) (arc->smaller, arc->larger, extra))
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/* Stop if requested. */
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break;
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/* Which next pointer to follow depends on whether REG is the
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smaller or larger reg in this conflict. */
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if (reg < arc->larger)
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arc = arc->smaller_next;
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else
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arc = arc->larger_next;
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}
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}
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/* For each conflict between a register x and SRC in GRAPH, adds a
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conflict to GRAPH between x and TARGET. */
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void
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conflict_graph_merge_regs (graph, target, src)
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conflict_graph graph;
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int target;
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int src;
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{
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conflict_graph_arc arc = graph->neighbor_heads[src];
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if (target == src)
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return;
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while (arc != NULL)
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{
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int other = arc->smaller;
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if (other == src)
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other = arc->larger;
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conflict_graph_add (graph, target, other);
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/* Which next pointer to follow depends on whether REG is the
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smaller or larger reg in this conflict. */
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if (src < arc->larger)
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arc = arc->smaller_next;
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else
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arc = arc->larger_next;
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}
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}
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/* Holds context information while a conflict graph is being traversed
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for printing. */
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struct print_context
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{
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/* The file pointer to which we're printing. */
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FILE *fp;
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/* The reg whose conflicts we're printing. */
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int reg;
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/* Whether a conflict has already been printed for this reg. */
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int started;
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};
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/* Callback function when enumerating conflicts during printing. */
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static int
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print_conflict (reg1, reg2, contextp)
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int reg1;
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int reg2;
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void *contextp;
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{
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struct print_context *context = (struct print_context *) contextp;
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int reg;
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/* If this is the first conflict printed for this reg, start a new
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line. */
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if (! context->started)
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{
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fprintf (context->fp, " %d:", context->reg);
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context->started = 1;
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}
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/* Figure out the reg whose conflicts we're printing. The other reg
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is the interesting one. */
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if (reg1 == context->reg)
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reg = reg2;
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else if (reg2 == context->reg)
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reg = reg1;
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else
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abort ();
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/* Print the conflict. */
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fprintf (context->fp, " %d", reg);
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/* Continue enumerating. */
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return 0;
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}
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/* Prints the conflicts in GRAPH to FP. */
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void
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conflict_graph_print (graph, fp)
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conflict_graph graph;
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FILE *fp;
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{
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int reg;
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struct print_context context;
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context.fp = fp;
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fprintf (fp, "Conflicts:\n");
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/* Loop over registers supported in this graph. */
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for (reg = 0; reg < graph->num_regs; ++reg)
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{
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context.reg = reg;
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context.started = 0;
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/* Scan the conflicts for reg, printing as we go. A label for
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this line will be printed the first time a conflict is
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printed for the reg; we won't start a new line if this reg
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has no conflicts. */
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conflict_graph_enum (graph, reg, &print_conflict, &context);
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/* If this reg does have conflicts, end the line. */
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if (context.started)
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fputc ('\n', fp);
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}
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}
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/* Callback function for note_stores. */
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static void
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mark_reg (reg, setter, data)
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rtx reg;
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rtx setter ATTRIBUTE_UNUSED;
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void *data;
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{
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regset set = (regset) data;
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if (GET_CODE (reg) == SUBREG)
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reg = SUBREG_REG (reg);
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/* We're only interested in regs. */
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if (GET_CODE (reg) != REG)
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return;
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SET_REGNO_REG_SET (set, REGNO (reg));
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}
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/* Allocates a conflict graph and computes conflicts over the current
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function for the registers set in REGS. The caller is responsible
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for deallocating the return value.
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Preconditions: the flow graph must be in SSA form, and life
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analysis (specifically, regs live at exit from each block) must be
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up-to-date.
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This algorithm determines conflicts by walking the insns in each
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block backwards. We maintain the set of live regs at each insn,
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starting with the regs live on exit from the block. For each insn:
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1. If a reg is set in this insns, it must be born here, since
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we're in SSA. Therefore, it was not live before this insns,
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so remove it from the set of live regs.
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2. For each reg born in this insn, record a conflict between it
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and every other reg live coming into this insn. For each
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existing conflict, one of the two regs must be born while the
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other is alive. See Morgan or elsewhere for a proof of this.
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3. Regs clobbered by this insn must have been live coming into
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it, so record them as such.
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The resulting conflict graph is not built for regs in REGS
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themselves; rather, partition P is used to obtain the canonical reg
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for each of these. The nodes of the conflict graph are these
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canonical regs instead. */
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conflict_graph
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conflict_graph_compute (regs, p)
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regset regs;
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partition p;
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{
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int b;
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conflict_graph graph = conflict_graph_new (max_reg_num ());
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regset_head live_head;
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regset live = &live_head;
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regset_head born_head;
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regset born = &born_head;
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INIT_REG_SET (live);
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INIT_REG_SET (born);
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for (b = n_basic_blocks; --b >= 0; )
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{
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basic_block bb = BASIC_BLOCK (b);
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rtx insn;
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rtx head;
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/* Start with the regs that are live on exit, limited to those
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we're interested in. */
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COPY_REG_SET (live, bb->global_live_at_end);
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AND_REG_SET (live, regs);
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/* Walk the instruction stream backwards. */
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head = bb->head;
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insn = bb->end;
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for (insn = bb->end; insn != head; insn = PREV_INSN (insn))
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{
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int born_reg;
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int live_reg;
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rtx link;
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/* Are we interested in this insn? */
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if (INSN_P (insn))
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{
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/* Determine which regs are set in this insn. Since
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we're in SSA form, if a reg is set here it isn't set
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anywhere else, so this insn is where the reg is born. */
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CLEAR_REG_SET (born);
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note_stores (PATTERN (insn), mark_reg, born);
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AND_REG_SET (born, regs);
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/* Regs born here were not live before this insn. */
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AND_COMPL_REG_SET (live, born);
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/* For every reg born here, add a conflict with every other
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reg live coming into this insn. */
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EXECUTE_IF_SET_IN_REG_SET
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(born, FIRST_PSEUDO_REGISTER, born_reg,
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{
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EXECUTE_IF_SET_IN_REG_SET
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(live, FIRST_PSEUDO_REGISTER, live_reg,
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{
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/* Build the conflict graph in terms of canonical
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regnos. */
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int b = partition_find (p, born_reg);
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int l = partition_find (p, live_reg);
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if (b != l)
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conflict_graph_add (graph, b, l);
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});
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});
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/* Morgan's algorithm checks the operands of the insn
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and adds them to the set of live regs. Instead, we
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use death information added by life analysis. Regs
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dead after this instruction were live before it. */
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for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
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if (REG_NOTE_KIND (link) == REG_DEAD)
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{
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unsigned int regno = REGNO (XEXP (link, 0));
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if (REGNO_REG_SET_P (regs, regno))
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SET_REGNO_REG_SET (live, regno);
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}
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}
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}
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}
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FREE_REG_SET (live);
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FREE_REG_SET (born);
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return graph;
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}
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