1596 lines
48 KiB
C
1596 lines
48 KiB
C
/* Thread edges through blocks and update the control flow and SSA graphs.
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Copyright (C) 2004-2013 Free Software Foundation, Inc.
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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
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3, or (at your option)
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any later version.
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GCC is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License 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 COPYING3. If not see
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<http://www.gnu.org/licenses/>. */
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#include "config.h"
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#include "system.h"
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#include "coretypes.h"
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#include "tree.h"
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#include "flags.h"
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#include "basic-block.h"
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#include "function.h"
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#include "gimple.h"
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#include "gimple-iterator.h"
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#include "gimple-ssa.h"
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#include "tree-phinodes.h"
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#include "tree-ssa.h"
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#include "tree-ssa-threadupdate.h"
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#include "dumpfile.h"
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#include "cfgloop.h"
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#include "hash-table.h"
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#include "dbgcnt.h"
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/* Given a block B, update the CFG and SSA graph to reflect redirecting
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one or more in-edges to B to instead reach the destination of an
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out-edge from B while preserving any side effects in B.
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i.e., given A->B and B->C, change A->B to be A->C yet still preserve the
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side effects of executing B.
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1. Make a copy of B (including its outgoing edges and statements). Call
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the copy B'. Note B' has no incoming edges or PHIs at this time.
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2. Remove the control statement at the end of B' and all outgoing edges
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except B'->C.
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3. Add a new argument to each PHI in C with the same value as the existing
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argument associated with edge B->C. Associate the new PHI arguments
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with the edge B'->C.
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4. For each PHI in B, find or create a PHI in B' with an identical
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PHI_RESULT. Add an argument to the PHI in B' which has the same
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value as the PHI in B associated with the edge A->B. Associate
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the new argument in the PHI in B' with the edge A->B.
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5. Change the edge A->B to A->B'.
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5a. This automatically deletes any PHI arguments associated with the
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edge A->B in B.
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5b. This automatically associates each new argument added in step 4
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with the edge A->B'.
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6. Repeat for other incoming edges into B.
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7. Put the duplicated resources in B and all the B' blocks into SSA form.
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Note that block duplication can be minimized by first collecting the
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set of unique destination blocks that the incoming edges should
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be threaded to.
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Block duplication can be further minimized by using B instead of
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creating B' for one destination if all edges into B are going to be
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threaded to a successor of B. We had code to do this at one time, but
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I'm not convinced it is correct with the changes to avoid mucking up
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the loop structure (which may cancel threading requests, thus a block
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which we thought was going to become unreachable may still be reachable).
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This code was also going to get ugly with the introduction of the ability
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for a single jump thread request to bypass multiple blocks.
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We further reduce the number of edges and statements we create by
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not copying all the outgoing edges and the control statement in
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step #1. We instead create a template block without the outgoing
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edges and duplicate the template. */
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/* Steps #5 and #6 of the above algorithm are best implemented by walking
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all the incoming edges which thread to the same destination edge at
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the same time. That avoids lots of table lookups to get information
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for the destination edge.
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To realize that implementation we create a list of incoming edges
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which thread to the same outgoing edge. Thus to implement steps
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#5 and #6 we traverse our hash table of outgoing edge information.
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For each entry we walk the list of incoming edges which thread to
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the current outgoing edge. */
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struct el
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{
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edge e;
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struct el *next;
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};
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/* Main data structure recording information regarding B's duplicate
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blocks. */
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/* We need to efficiently record the unique thread destinations of this
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block and specific information associated with those destinations. We
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may have many incoming edges threaded to the same outgoing edge. This
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can be naturally implemented with a hash table. */
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struct redirection_data : typed_free_remove<redirection_data>
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{
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/* A duplicate of B with the trailing control statement removed and which
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targets a single successor of B. */
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basic_block dup_block;
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/* The jump threading path. */
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vec<jump_thread_edge *> *path;
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/* A list of incoming edges which we want to thread to the
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same path. */
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struct el *incoming_edges;
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/* hash_table support. */
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typedef redirection_data value_type;
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typedef redirection_data compare_type;
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static inline hashval_t hash (const value_type *);
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static inline int equal (const value_type *, const compare_type *);
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};
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/* Simple hashing function. For any given incoming edge E, we're going
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to be most concerned with the final destination of its jump thread
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path. So hash on the block index of the final edge in the path. */
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inline hashval_t
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redirection_data::hash (const value_type *p)
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{
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vec<jump_thread_edge *> *path = p->path;
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return path->last ()->e->dest->index;
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}
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/* Given two hash table entries, return true if they have the same
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jump threading path. */
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inline int
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redirection_data::equal (const value_type *p1, const compare_type *p2)
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{
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vec<jump_thread_edge *> *path1 = p1->path;
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vec<jump_thread_edge *> *path2 = p2->path;
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if (path1->length () != path2->length ())
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return false;
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for (unsigned int i = 1; i < path1->length (); i++)
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{
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if ((*path1)[i]->type != (*path2)[i]->type
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|| (*path1)[i]->e != (*path2)[i]->e)
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return false;
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}
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return true;
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}
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/* Data structure of information to pass to hash table traversal routines. */
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struct ssa_local_info_t
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{
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/* The current block we are working on. */
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basic_block bb;
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/* A template copy of BB with no outgoing edges or control statement that
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we use for creating copies. */
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basic_block template_block;
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/* TRUE if we thread one or more jumps, FALSE otherwise. */
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bool jumps_threaded;
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};
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/* Passes which use the jump threading code register jump threading
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opportunities as they are discovered. We keep the registered
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jump threading opportunities in this vector as edge pairs
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(original_edge, target_edge). */
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static vec<vec<jump_thread_edge *> *> paths;
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/* When we start updating the CFG for threading, data necessary for jump
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threading is attached to the AUX field for the incoming edge. Use these
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macros to access the underlying structure attached to the AUX field. */
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#define THREAD_PATH(E) ((vec<jump_thread_edge *> *)(E)->aux)
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/* Jump threading statistics. */
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struct thread_stats_d
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{
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unsigned long num_threaded_edges;
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};
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struct thread_stats_d thread_stats;
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/* Remove the last statement in block BB if it is a control statement
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Also remove all outgoing edges except the edge which reaches DEST_BB.
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If DEST_BB is NULL, then remove all outgoing edges. */
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static void
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remove_ctrl_stmt_and_useless_edges (basic_block bb, basic_block dest_bb)
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{
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gimple_stmt_iterator gsi;
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edge e;
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edge_iterator ei;
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gsi = gsi_last_bb (bb);
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/* If the duplicate ends with a control statement, then remove it.
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Note that if we are duplicating the template block rather than the
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original basic block, then the duplicate might not have any real
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statements in it. */
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if (!gsi_end_p (gsi)
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&& gsi_stmt (gsi)
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&& (gimple_code (gsi_stmt (gsi)) == GIMPLE_COND
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|| gimple_code (gsi_stmt (gsi)) == GIMPLE_GOTO
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|| gimple_code (gsi_stmt (gsi)) == GIMPLE_SWITCH))
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gsi_remove (&gsi, true);
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for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); )
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{
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if (e->dest != dest_bb)
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remove_edge (e);
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else
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ei_next (&ei);
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}
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}
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/* Create a duplicate of BB. Record the duplicate block in RD. */
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static void
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create_block_for_threading (basic_block bb, struct redirection_data *rd)
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{
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edge_iterator ei;
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edge e;
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/* We can use the generic block duplication code and simply remove
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the stuff we do not need. */
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rd->dup_block = duplicate_block (bb, NULL, NULL);
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FOR_EACH_EDGE (e, ei, rd->dup_block->succs)
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e->aux = NULL;
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/* Zero out the profile, since the block is unreachable for now. */
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rd->dup_block->frequency = 0;
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rd->dup_block->count = 0;
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}
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/* Main data structure to hold information for duplicates of BB. */
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static hash_table <redirection_data> redirection_data;
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/* Given an outgoing edge E lookup and return its entry in our hash table.
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If INSERT is true, then we insert the entry into the hash table if
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it is not already present. INCOMING_EDGE is added to the list of incoming
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edges associated with E in the hash table. */
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static struct redirection_data *
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lookup_redirection_data (edge e, enum insert_option insert)
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{
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struct redirection_data **slot;
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struct redirection_data *elt;
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vec<jump_thread_edge *> *path = THREAD_PATH (e);
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/* Build a hash table element so we can see if E is already
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in the table. */
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elt = XNEW (struct redirection_data);
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elt->path = path;
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elt->dup_block = NULL;
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elt->incoming_edges = NULL;
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slot = redirection_data.find_slot (elt, insert);
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/* This will only happen if INSERT is false and the entry is not
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in the hash table. */
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if (slot == NULL)
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{
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free (elt);
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return NULL;
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}
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/* This will only happen if E was not in the hash table and
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INSERT is true. */
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if (*slot == NULL)
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{
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*slot = elt;
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elt->incoming_edges = XNEW (struct el);
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elt->incoming_edges->e = e;
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elt->incoming_edges->next = NULL;
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return elt;
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}
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/* E was in the hash table. */
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else
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{
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/* Free ELT as we do not need it anymore, we will extract the
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relevant entry from the hash table itself. */
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free (elt);
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/* Get the entry stored in the hash table. */
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elt = *slot;
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/* If insertion was requested, then we need to add INCOMING_EDGE
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to the list of incoming edges associated with E. */
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if (insert)
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{
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struct el *el = XNEW (struct el);
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el->next = elt->incoming_edges;
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el->e = e;
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elt->incoming_edges = el;
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}
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return elt;
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}
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}
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/* For each PHI in BB, copy the argument associated with SRC_E to TGT_E. */
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static void
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copy_phi_args (basic_block bb, edge src_e, edge tgt_e)
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{
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gimple_stmt_iterator gsi;
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int src_indx = src_e->dest_idx;
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for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
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{
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gimple phi = gsi_stmt (gsi);
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source_location locus = gimple_phi_arg_location (phi, src_indx);
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add_phi_arg (phi, gimple_phi_arg_def (phi, src_indx), tgt_e, locus);
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}
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}
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/* We have recently made a copy of ORIG_BB, including its outgoing
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edges. The copy is NEW_BB. Every PHI node in every direct successor of
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ORIG_BB has a new argument associated with edge from NEW_BB to the
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successor. Initialize the PHI argument so that it is equal to the PHI
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argument associated with the edge from ORIG_BB to the successor. */
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static void
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update_destination_phis (basic_block orig_bb, basic_block new_bb)
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{
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edge_iterator ei;
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edge e;
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FOR_EACH_EDGE (e, ei, orig_bb->succs)
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{
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edge e2 = find_edge (new_bb, e->dest);
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copy_phi_args (e->dest, e, e2);
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}
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}
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/* Given a duplicate block and its single destination (both stored
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in RD). Create an edge between the duplicate and its single
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destination.
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Add an additional argument to any PHI nodes at the single
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destination. */
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static void
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create_edge_and_update_destination_phis (struct redirection_data *rd,
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basic_block bb)
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{
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edge e = make_edge (bb, rd->path->last ()->e->dest, EDGE_FALLTHRU);
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rescan_loop_exit (e, true, false);
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e->probability = REG_BR_PROB_BASE;
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e->count = bb->count;
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/* We have to copy path -- which means creating a new vector as well
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as all the jump_thread_edge entries. */
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if (rd->path->last ()->e->aux)
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{
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vec<jump_thread_edge *> *path = THREAD_PATH (rd->path->last ()->e);
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vec<jump_thread_edge *> *copy = new vec<jump_thread_edge *> ();
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/* Sadly, the elements of the vector are pointers and need to
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be copied as well. */
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for (unsigned int i = 0; i < path->length (); i++)
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{
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jump_thread_edge *x
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= new jump_thread_edge ((*path)[i]->e, (*path)[i]->type);
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copy->safe_push (x);
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}
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e->aux = (void *)copy;
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}
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else
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{
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e->aux = NULL;
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}
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/* If there are any PHI nodes at the destination of the outgoing edge
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from the duplicate block, then we will need to add a new argument
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to them. The argument should have the same value as the argument
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associated with the outgoing edge stored in RD. */
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copy_phi_args (e->dest, rd->path->last ()->e, e);
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}
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/* Wire up the outgoing edges from the duplicate block and
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update any PHIs as needed. */
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void
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ssa_fix_duplicate_block_edges (struct redirection_data *rd,
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ssa_local_info_t *local_info)
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{
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edge e = rd->incoming_edges->e;
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vec<jump_thread_edge *> *path = THREAD_PATH (e);
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/* If we were threading through an joiner block, then we want
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to keep its control statement and redirect an outgoing edge.
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Else we want to remove the control statement & edges, then create
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a new outgoing edge. In both cases we may need to update PHIs. */
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if ((*path)[1]->type == EDGE_COPY_SRC_JOINER_BLOCK)
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{
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edge victim;
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edge e2;
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/* This updates the PHIs at the destination of the duplicate
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block. */
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update_destination_phis (local_info->bb, rd->dup_block);
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/* Find the edge from the duplicate block to the block we're
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threading through. That's the edge we want to redirect. */
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victim = find_edge (rd->dup_block, (*path)[1]->e->dest);
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e2 = redirect_edge_and_branch (victim, path->last ()->e->dest);
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e2->count = path->last ()->e->count;
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/* If we redirected the edge, then we need to copy PHI arguments
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at the target. If the edge already existed (e2 != victim case),
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then the PHIs in the target already have the correct arguments. */
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if (e2 == victim)
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copy_phi_args (e2->dest, path->last ()->e, e2);
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}
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else
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{
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remove_ctrl_stmt_and_useless_edges (rd->dup_block, NULL);
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create_edge_and_update_destination_phis (rd, rd->dup_block);
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}
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}
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/* Hash table traversal callback routine to create duplicate blocks. */
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int
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ssa_create_duplicates (struct redirection_data **slot,
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ssa_local_info_t *local_info)
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{
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struct redirection_data *rd = *slot;
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/* Create a template block if we have not done so already. Otherwise
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use the template to create a new block. */
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if (local_info->template_block == NULL)
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{
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create_block_for_threading (local_info->bb, rd);
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local_info->template_block = rd->dup_block;
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/* We do not create any outgoing edges for the template. We will
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take care of that in a later traversal. That way we do not
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create edges that are going to just be deleted. */
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}
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else
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{
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create_block_for_threading (local_info->template_block, rd);
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/* Go ahead and wire up outgoing edges and update PHIs for the duplicate
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block. */
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ssa_fix_duplicate_block_edges (rd, local_info);
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}
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/* Keep walking the hash table. */
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return 1;
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}
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/* We did not create any outgoing edges for the template block during
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block creation. This hash table traversal callback creates the
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outgoing edge for the template block. */
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inline int
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ssa_fixup_template_block (struct redirection_data **slot,
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ssa_local_info_t *local_info)
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{
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struct redirection_data *rd = *slot;
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/* If this is the template block halt the traversal after updating
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it appropriately.
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If we were threading through an joiner block, then we want
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to keep its control statement and redirect an outgoing edge.
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Else we want to remove the control statement & edges, then create
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a new outgoing edge. In both cases we may need to update PHIs. */
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if (rd->dup_block && rd->dup_block == local_info->template_block)
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{
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ssa_fix_duplicate_block_edges (rd, local_info);
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return 0;
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}
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return 1;
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}
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/* Hash table traversal callback to redirect each incoming edge
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associated with this hash table element to its new destination. */
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int
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ssa_redirect_edges (struct redirection_data **slot,
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ssa_local_info_t *local_info)
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{
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struct redirection_data *rd = *slot;
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struct el *next, *el;
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/* Walk over all the incoming edges associated associated with this
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hash table entry. */
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for (el = rd->incoming_edges; el; el = next)
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|
{
|
|
edge e = el->e;
|
|
vec<jump_thread_edge *> *path = THREAD_PATH (e);
|
|
|
|
/* Go ahead and free this element from the list. Doing this now
|
|
avoids the need for another list walk when we destroy the hash
|
|
table. */
|
|
next = el->next;
|
|
free (el);
|
|
|
|
thread_stats.num_threaded_edges++;
|
|
|
|
if (rd->dup_block)
|
|
{
|
|
edge e2;
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
fprintf (dump_file, " Threaded jump %d --> %d to %d\n",
|
|
e->src->index, e->dest->index, rd->dup_block->index);
|
|
|
|
rd->dup_block->count += e->count;
|
|
|
|
/* Excessive jump threading may make frequencies large enough so
|
|
the computation overflows. */
|
|
if (rd->dup_block->frequency < BB_FREQ_MAX * 2)
|
|
rd->dup_block->frequency += EDGE_FREQUENCY (e);
|
|
|
|
/* In the case of threading through a joiner block, the outgoing
|
|
edges from the duplicate block were updated when they were
|
|
redirected during ssa_fix_duplicate_block_edges. */
|
|
if ((*path)[1]->type != EDGE_COPY_SRC_JOINER_BLOCK)
|
|
EDGE_SUCC (rd->dup_block, 0)->count += e->count;
|
|
|
|
/* Redirect the incoming edge (possibly to the joiner block) to the
|
|
appropriate duplicate block. */
|
|
e2 = redirect_edge_and_branch (e, rd->dup_block);
|
|
gcc_assert (e == e2);
|
|
flush_pending_stmts (e2);
|
|
}
|
|
|
|
/* Go ahead and clear E->aux. It's not needed anymore and failure
|
|
to clear it will cause all kinds of unpleasant problems later. */
|
|
delete_jump_thread_path (path);
|
|
e->aux = NULL;
|
|
|
|
}
|
|
|
|
/* Indicate that we actually threaded one or more jumps. */
|
|
if (rd->incoming_edges)
|
|
local_info->jumps_threaded = true;
|
|
|
|
return 1;
|
|
}
|
|
|
|
/* Return true if this block has no executable statements other than
|
|
a simple ctrl flow instruction. When the number of outgoing edges
|
|
is one, this is equivalent to a "forwarder" block. */
|
|
|
|
static bool
|
|
redirection_block_p (basic_block bb)
|
|
{
|
|
gimple_stmt_iterator gsi;
|
|
|
|
/* Advance to the first executable statement. */
|
|
gsi = gsi_start_bb (bb);
|
|
while (!gsi_end_p (gsi)
|
|
&& (gimple_code (gsi_stmt (gsi)) == GIMPLE_LABEL
|
|
|| is_gimple_debug (gsi_stmt (gsi))
|
|
|| gimple_nop_p (gsi_stmt (gsi))))
|
|
gsi_next (&gsi);
|
|
|
|
/* Check if this is an empty block. */
|
|
if (gsi_end_p (gsi))
|
|
return true;
|
|
|
|
/* Test that we've reached the terminating control statement. */
|
|
return gsi_stmt (gsi)
|
|
&& (gimple_code (gsi_stmt (gsi)) == GIMPLE_COND
|
|
|| gimple_code (gsi_stmt (gsi)) == GIMPLE_GOTO
|
|
|| gimple_code (gsi_stmt (gsi)) == GIMPLE_SWITCH);
|
|
}
|
|
|
|
/* BB is a block which ends with a COND_EXPR or SWITCH_EXPR and when BB
|
|
is reached via one or more specific incoming edges, we know which
|
|
outgoing edge from BB will be traversed.
|
|
|
|
We want to redirect those incoming edges to the target of the
|
|
appropriate outgoing edge. Doing so avoids a conditional branch
|
|
and may expose new optimization opportunities. Note that we have
|
|
to update dominator tree and SSA graph after such changes.
|
|
|
|
The key to keeping the SSA graph update manageable is to duplicate
|
|
the side effects occurring in BB so that those side effects still
|
|
occur on the paths which bypass BB after redirecting edges.
|
|
|
|
We accomplish this by creating duplicates of BB and arranging for
|
|
the duplicates to unconditionally pass control to one specific
|
|
successor of BB. We then revector the incoming edges into BB to
|
|
the appropriate duplicate of BB.
|
|
|
|
If NOLOOP_ONLY is true, we only perform the threading as long as it
|
|
does not affect the structure of the loops in a nontrivial way.
|
|
|
|
If JOINERS is true, then thread through joiner blocks as well. */
|
|
|
|
static bool
|
|
thread_block_1 (basic_block bb, bool noloop_only, bool joiners)
|
|
{
|
|
/* E is an incoming edge into BB that we may or may not want to
|
|
redirect to a duplicate of BB. */
|
|
edge e, e2;
|
|
edge_iterator ei;
|
|
ssa_local_info_t local_info;
|
|
struct loop *loop = bb->loop_father;
|
|
|
|
/* To avoid scanning a linear array for the element we need we instead
|
|
use a hash table. For normal code there should be no noticeable
|
|
difference. However, if we have a block with a large number of
|
|
incoming and outgoing edges such linear searches can get expensive. */
|
|
redirection_data.create (EDGE_COUNT (bb->succs));
|
|
|
|
/* If we thread the latch of the loop to its exit, the loop ceases to
|
|
exist. Make sure we do not restrict ourselves in order to preserve
|
|
this loop. */
|
|
if (loop->header == bb)
|
|
{
|
|
e = loop_latch_edge (loop);
|
|
vec<jump_thread_edge *> *path = THREAD_PATH (e);
|
|
|
|
if (path
|
|
&& (((*path)[1]->type == EDGE_COPY_SRC_JOINER_BLOCK && joiners)
|
|
|| ((*path)[1]->type == EDGE_COPY_SRC_BLOCK && !joiners)))
|
|
{
|
|
for (unsigned int i = 1; i < path->length (); i++)
|
|
{
|
|
edge e2 = (*path)[i]->e;
|
|
|
|
if (loop_exit_edge_p (loop, e2))
|
|
{
|
|
loop->header = NULL;
|
|
loop->latch = NULL;
|
|
loops_state_set (LOOPS_NEED_FIXUP);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Record each unique threaded destination into a hash table for
|
|
efficient lookups. */
|
|
FOR_EACH_EDGE (e, ei, bb->preds)
|
|
{
|
|
if (e->aux == NULL)
|
|
continue;
|
|
|
|
vec<jump_thread_edge *> *path = THREAD_PATH (e);
|
|
|
|
if (((*path)[1]->type == EDGE_COPY_SRC_JOINER_BLOCK && !joiners)
|
|
|| ((*path)[1]->type == EDGE_COPY_SRC_BLOCK && joiners))
|
|
continue;
|
|
|
|
e2 = path->last ()->e;
|
|
if (!e2 || noloop_only)
|
|
{
|
|
/* If NOLOOP_ONLY is true, we only allow threading through the
|
|
header of a loop to exit edges.
|
|
|
|
There are two cases to consider. The first when BB is the
|
|
loop header. We will attempt to thread this elsewhere, so
|
|
we can just continue here. */
|
|
|
|
if (bb == bb->loop_father->header
|
|
&& (!loop_exit_edge_p (bb->loop_father, e2)
|
|
|| (*path)[1]->type == EDGE_COPY_SRC_JOINER_BLOCK))
|
|
continue;
|
|
|
|
|
|
/* The second occurs when there was loop header buried in a jump
|
|
threading path. We do not try and thread this elsewhere, so
|
|
just cancel the jump threading request by clearing the AUX
|
|
field now. */
|
|
if ((bb->loop_father != e2->src->loop_father
|
|
&& !loop_exit_edge_p (e2->src->loop_father, e2))
|
|
|| (e2->src->loop_father != e2->dest->loop_father
|
|
&& !loop_exit_edge_p (e2->src->loop_father, e2)))
|
|
{
|
|
/* Since this case is not handled by our special code
|
|
to thread through a loop header, we must explicitly
|
|
cancel the threading request here. */
|
|
delete_jump_thread_path (path);
|
|
e->aux = NULL;
|
|
continue;
|
|
}
|
|
}
|
|
|
|
if (e->dest == e2->src)
|
|
update_bb_profile_for_threading (e->dest, EDGE_FREQUENCY (e),
|
|
e->count, (*THREAD_PATH (e))[1]->e);
|
|
|
|
/* Insert the outgoing edge into the hash table if it is not
|
|
already in the hash table. */
|
|
lookup_redirection_data (e, INSERT);
|
|
}
|
|
|
|
/* We do not update dominance info. */
|
|
free_dominance_info (CDI_DOMINATORS);
|
|
|
|
/* We know we only thread through the loop header to loop exits.
|
|
Let the basic block duplication hook know we are not creating
|
|
a multiple entry loop. */
|
|
if (noloop_only
|
|
&& bb == bb->loop_father->header)
|
|
set_loop_copy (bb->loop_father, loop_outer (bb->loop_father));
|
|
|
|
/* Now create duplicates of BB.
|
|
|
|
Note that for a block with a high outgoing degree we can waste
|
|
a lot of time and memory creating and destroying useless edges.
|
|
|
|
So we first duplicate BB and remove the control structure at the
|
|
tail of the duplicate as well as all outgoing edges from the
|
|
duplicate. We then use that duplicate block as a template for
|
|
the rest of the duplicates. */
|
|
local_info.template_block = NULL;
|
|
local_info.bb = bb;
|
|
local_info.jumps_threaded = false;
|
|
redirection_data.traverse <ssa_local_info_t *, ssa_create_duplicates>
|
|
(&local_info);
|
|
|
|
/* The template does not have an outgoing edge. Create that outgoing
|
|
edge and update PHI nodes as the edge's target as necessary.
|
|
|
|
We do this after creating all the duplicates to avoid creating
|
|
unnecessary edges. */
|
|
redirection_data.traverse <ssa_local_info_t *, ssa_fixup_template_block>
|
|
(&local_info);
|
|
|
|
/* The hash table traversals above created the duplicate blocks (and the
|
|
statements within the duplicate blocks). This loop creates PHI nodes for
|
|
the duplicated blocks and redirects the incoming edges into BB to reach
|
|
the duplicates of BB. */
|
|
redirection_data.traverse <ssa_local_info_t *, ssa_redirect_edges>
|
|
(&local_info);
|
|
|
|
/* Done with this block. Clear REDIRECTION_DATA. */
|
|
redirection_data.dispose ();
|
|
|
|
if (noloop_only
|
|
&& bb == bb->loop_father->header)
|
|
set_loop_copy (bb->loop_father, NULL);
|
|
|
|
/* Indicate to our caller whether or not any jumps were threaded. */
|
|
return local_info.jumps_threaded;
|
|
}
|
|
|
|
/* Wrapper for thread_block_1 so that we can first handle jump
|
|
thread paths which do not involve copying joiner blocks, then
|
|
handle jump thread paths which have joiner blocks.
|
|
|
|
By doing things this way we can be as aggressive as possible and
|
|
not worry that copying a joiner block will create a jump threading
|
|
opportunity. */
|
|
|
|
static bool
|
|
thread_block (basic_block bb, bool noloop_only)
|
|
{
|
|
bool retval;
|
|
retval = thread_block_1 (bb, noloop_only, false);
|
|
retval |= thread_block_1 (bb, noloop_only, true);
|
|
return retval;
|
|
}
|
|
|
|
|
|
/* Threads edge E through E->dest to the edge THREAD_TARGET (E). Returns the
|
|
copy of E->dest created during threading, or E->dest if it was not necessary
|
|
to copy it (E is its single predecessor). */
|
|
|
|
static basic_block
|
|
thread_single_edge (edge e)
|
|
{
|
|
basic_block bb = e->dest;
|
|
struct redirection_data rd;
|
|
vec<jump_thread_edge *> *path = THREAD_PATH (e);
|
|
edge eto = (*path)[1]->e;
|
|
|
|
for (unsigned int i = 0; i < path->length (); i++)
|
|
delete (*path)[i];
|
|
delete path;
|
|
e->aux = NULL;
|
|
|
|
thread_stats.num_threaded_edges++;
|
|
|
|
if (single_pred_p (bb))
|
|
{
|
|
/* If BB has just a single predecessor, we should only remove the
|
|
control statements at its end, and successors except for ETO. */
|
|
remove_ctrl_stmt_and_useless_edges (bb, eto->dest);
|
|
|
|
/* And fixup the flags on the single remaining edge. */
|
|
eto->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE | EDGE_ABNORMAL);
|
|
eto->flags |= EDGE_FALLTHRU;
|
|
|
|
return bb;
|
|
}
|
|
|
|
/* Otherwise, we need to create a copy. */
|
|
if (e->dest == eto->src)
|
|
update_bb_profile_for_threading (bb, EDGE_FREQUENCY (e), e->count, eto);
|
|
|
|
vec<jump_thread_edge *> *npath = new vec<jump_thread_edge *> ();
|
|
jump_thread_edge *x = new jump_thread_edge (e, EDGE_START_JUMP_THREAD);
|
|
npath->safe_push (x);
|
|
|
|
x = new jump_thread_edge (eto, EDGE_COPY_SRC_BLOCK);
|
|
npath->safe_push (x);
|
|
rd.path = npath;
|
|
|
|
create_block_for_threading (bb, &rd);
|
|
remove_ctrl_stmt_and_useless_edges (rd.dup_block, NULL);
|
|
create_edge_and_update_destination_phis (&rd, rd.dup_block);
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
fprintf (dump_file, " Threaded jump %d --> %d to %d\n",
|
|
e->src->index, e->dest->index, rd.dup_block->index);
|
|
|
|
rd.dup_block->count = e->count;
|
|
rd.dup_block->frequency = EDGE_FREQUENCY (e);
|
|
single_succ_edge (rd.dup_block)->count = e->count;
|
|
redirect_edge_and_branch (e, rd.dup_block);
|
|
flush_pending_stmts (e);
|
|
|
|
return rd.dup_block;
|
|
}
|
|
|
|
/* Callback for dfs_enumerate_from. Returns true if BB is different
|
|
from STOP and DBDS_CE_STOP. */
|
|
|
|
static basic_block dbds_ce_stop;
|
|
static bool
|
|
dbds_continue_enumeration_p (const_basic_block bb, const void *stop)
|
|
{
|
|
return (bb != (const_basic_block) stop
|
|
&& bb != dbds_ce_stop);
|
|
}
|
|
|
|
/* Evaluates the dominance relationship of latch of the LOOP and BB, and
|
|
returns the state. */
|
|
|
|
enum bb_dom_status
|
|
{
|
|
/* BB does not dominate latch of the LOOP. */
|
|
DOMST_NONDOMINATING,
|
|
/* The LOOP is broken (there is no path from the header to its latch. */
|
|
DOMST_LOOP_BROKEN,
|
|
/* BB dominates the latch of the LOOP. */
|
|
DOMST_DOMINATING
|
|
};
|
|
|
|
static enum bb_dom_status
|
|
determine_bb_domination_status (struct loop *loop, basic_block bb)
|
|
{
|
|
basic_block *bblocks;
|
|
unsigned nblocks, i;
|
|
bool bb_reachable = false;
|
|
edge_iterator ei;
|
|
edge e;
|
|
|
|
/* This function assumes BB is a successor of LOOP->header.
|
|
If that is not the case return DOMST_NONDOMINATING which
|
|
is always safe. */
|
|
{
|
|
bool ok = false;
|
|
|
|
FOR_EACH_EDGE (e, ei, bb->preds)
|
|
{
|
|
if (e->src == loop->header)
|
|
{
|
|
ok = true;
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (!ok)
|
|
return DOMST_NONDOMINATING;
|
|
}
|
|
|
|
if (bb == loop->latch)
|
|
return DOMST_DOMINATING;
|
|
|
|
/* Check that BB dominates LOOP->latch, and that it is back-reachable
|
|
from it. */
|
|
|
|
bblocks = XCNEWVEC (basic_block, loop->num_nodes);
|
|
dbds_ce_stop = loop->header;
|
|
nblocks = dfs_enumerate_from (loop->latch, 1, dbds_continue_enumeration_p,
|
|
bblocks, loop->num_nodes, bb);
|
|
for (i = 0; i < nblocks; i++)
|
|
FOR_EACH_EDGE (e, ei, bblocks[i]->preds)
|
|
{
|
|
if (e->src == loop->header)
|
|
{
|
|
free (bblocks);
|
|
return DOMST_NONDOMINATING;
|
|
}
|
|
if (e->src == bb)
|
|
bb_reachable = true;
|
|
}
|
|
|
|
free (bblocks);
|
|
return (bb_reachable ? DOMST_DOMINATING : DOMST_LOOP_BROKEN);
|
|
}
|
|
|
|
/* Return true if BB is part of the new pre-header that is created
|
|
when threading the latch to DATA. */
|
|
|
|
static bool
|
|
def_split_header_continue_p (const_basic_block bb, const void *data)
|
|
{
|
|
const_basic_block new_header = (const_basic_block) data;
|
|
const struct loop *l;
|
|
|
|
if (bb == new_header
|
|
|| loop_depth (bb->loop_father) < loop_depth (new_header->loop_father))
|
|
return false;
|
|
for (l = bb->loop_father; l; l = loop_outer (l))
|
|
if (l == new_header->loop_father)
|
|
return true;
|
|
return false;
|
|
}
|
|
|
|
/* Thread jumps through the header of LOOP. Returns true if cfg changes.
|
|
If MAY_PEEL_LOOP_HEADERS is false, we avoid threading from entry edges
|
|
to the inside of the loop. */
|
|
|
|
static bool
|
|
thread_through_loop_header (struct loop *loop, bool may_peel_loop_headers)
|
|
{
|
|
basic_block header = loop->header;
|
|
edge e, tgt_edge, latch = loop_latch_edge (loop);
|
|
edge_iterator ei;
|
|
basic_block tgt_bb, atgt_bb;
|
|
enum bb_dom_status domst;
|
|
|
|
/* We have already threaded through headers to exits, so all the threading
|
|
requests now are to the inside of the loop. We need to avoid creating
|
|
irreducible regions (i.e., loops with more than one entry block), and
|
|
also loop with several latch edges, or new subloops of the loop (although
|
|
there are cases where it might be appropriate, it is difficult to decide,
|
|
and doing it wrongly may confuse other optimizers).
|
|
|
|
We could handle more general cases here. However, the intention is to
|
|
preserve some information about the loop, which is impossible if its
|
|
structure changes significantly, in a way that is not well understood.
|
|
Thus we only handle few important special cases, in which also updating
|
|
of the loop-carried information should be feasible:
|
|
|
|
1) Propagation of latch edge to a block that dominates the latch block
|
|
of a loop. This aims to handle the following idiom:
|
|
|
|
first = 1;
|
|
while (1)
|
|
{
|
|
if (first)
|
|
initialize;
|
|
first = 0;
|
|
body;
|
|
}
|
|
|
|
After threading the latch edge, this becomes
|
|
|
|
first = 1;
|
|
if (first)
|
|
initialize;
|
|
while (1)
|
|
{
|
|
first = 0;
|
|
body;
|
|
}
|
|
|
|
The original header of the loop is moved out of it, and we may thread
|
|
the remaining edges through it without further constraints.
|
|
|
|
2) All entry edges are propagated to a single basic block that dominates
|
|
the latch block of the loop. This aims to handle the following idiom
|
|
(normally created for "for" loops):
|
|
|
|
i = 0;
|
|
while (1)
|
|
{
|
|
if (i >= 100)
|
|
break;
|
|
body;
|
|
i++;
|
|
}
|
|
|
|
This becomes
|
|
|
|
i = 0;
|
|
while (1)
|
|
{
|
|
body;
|
|
i++;
|
|
if (i >= 100)
|
|
break;
|
|
}
|
|
*/
|
|
|
|
/* Threading through the header won't improve the code if the header has just
|
|
one successor. */
|
|
if (single_succ_p (header))
|
|
goto fail;
|
|
|
|
if (latch->aux)
|
|
{
|
|
vec<jump_thread_edge *> *path = THREAD_PATH (latch);
|
|
if ((*path)[1]->type == EDGE_COPY_SRC_JOINER_BLOCK)
|
|
goto fail;
|
|
tgt_edge = (*path)[1]->e;
|
|
tgt_bb = tgt_edge->dest;
|
|
}
|
|
else if (!may_peel_loop_headers
|
|
&& !redirection_block_p (loop->header))
|
|
goto fail;
|
|
else
|
|
{
|
|
tgt_bb = NULL;
|
|
tgt_edge = NULL;
|
|
FOR_EACH_EDGE (e, ei, header->preds)
|
|
{
|
|
if (!e->aux)
|
|
{
|
|
if (e == latch)
|
|
continue;
|
|
|
|
/* If latch is not threaded, and there is a header
|
|
edge that is not threaded, we would create loop
|
|
with multiple entries. */
|
|
goto fail;
|
|
}
|
|
|
|
vec<jump_thread_edge *> *path = THREAD_PATH (e);
|
|
|
|
if ((*path)[1]->type == EDGE_COPY_SRC_JOINER_BLOCK)
|
|
goto fail;
|
|
tgt_edge = (*path)[1]->e;
|
|
atgt_bb = tgt_edge->dest;
|
|
if (!tgt_bb)
|
|
tgt_bb = atgt_bb;
|
|
/* Two targets of threading would make us create loop
|
|
with multiple entries. */
|
|
else if (tgt_bb != atgt_bb)
|
|
goto fail;
|
|
}
|
|
|
|
if (!tgt_bb)
|
|
{
|
|
/* There are no threading requests. */
|
|
return false;
|
|
}
|
|
|
|
/* Redirecting to empty loop latch is useless. */
|
|
if (tgt_bb == loop->latch
|
|
&& empty_block_p (loop->latch))
|
|
goto fail;
|
|
}
|
|
|
|
/* The target block must dominate the loop latch, otherwise we would be
|
|
creating a subloop. */
|
|
domst = determine_bb_domination_status (loop, tgt_bb);
|
|
if (domst == DOMST_NONDOMINATING)
|
|
goto fail;
|
|
if (domst == DOMST_LOOP_BROKEN)
|
|
{
|
|
/* If the loop ceased to exist, mark it as such, and thread through its
|
|
original header. */
|
|
loop->header = NULL;
|
|
loop->latch = NULL;
|
|
loops_state_set (LOOPS_NEED_FIXUP);
|
|
return thread_block (header, false);
|
|
}
|
|
|
|
if (tgt_bb->loop_father->header == tgt_bb)
|
|
{
|
|
/* If the target of the threading is a header of a subloop, we need
|
|
to create a preheader for it, so that the headers of the two loops
|
|
do not merge. */
|
|
if (EDGE_COUNT (tgt_bb->preds) > 2)
|
|
{
|
|
tgt_bb = create_preheader (tgt_bb->loop_father, 0);
|
|
gcc_assert (tgt_bb != NULL);
|
|
}
|
|
else
|
|
tgt_bb = split_edge (tgt_edge);
|
|
}
|
|
|
|
if (latch->aux)
|
|
{
|
|
basic_block *bblocks;
|
|
unsigned nblocks, i;
|
|
|
|
/* First handle the case latch edge is redirected. We are copying
|
|
the loop header but not creating a multiple entry loop. Make the
|
|
cfg manipulation code aware of that fact. */
|
|
set_loop_copy (loop, loop);
|
|
loop->latch = thread_single_edge (latch);
|
|
set_loop_copy (loop, NULL);
|
|
gcc_assert (single_succ (loop->latch) == tgt_bb);
|
|
loop->header = tgt_bb;
|
|
|
|
/* Remove the new pre-header blocks from our loop. */
|
|
bblocks = XCNEWVEC (basic_block, loop->num_nodes);
|
|
nblocks = dfs_enumerate_from (header, 0, def_split_header_continue_p,
|
|
bblocks, loop->num_nodes, tgt_bb);
|
|
for (i = 0; i < nblocks; i++)
|
|
if (bblocks[i]->loop_father == loop)
|
|
{
|
|
remove_bb_from_loops (bblocks[i]);
|
|
add_bb_to_loop (bblocks[i], loop_outer (loop));
|
|
}
|
|
free (bblocks);
|
|
|
|
/* If the new header has multiple latches mark it so. */
|
|
FOR_EACH_EDGE (e, ei, loop->header->preds)
|
|
if (e->src->loop_father == loop
|
|
&& e->src != loop->latch)
|
|
{
|
|
loop->latch = NULL;
|
|
loops_state_set (LOOPS_MAY_HAVE_MULTIPLE_LATCHES);
|
|
}
|
|
|
|
/* Cancel remaining threading requests that would make the
|
|
loop a multiple entry loop. */
|
|
FOR_EACH_EDGE (e, ei, header->preds)
|
|
{
|
|
edge e2;
|
|
|
|
if (e->aux == NULL)
|
|
continue;
|
|
|
|
vec<jump_thread_edge *> *path = THREAD_PATH (e);
|
|
e2 = path->last ()->e;
|
|
|
|
if (e->src->loop_father != e2->dest->loop_father
|
|
&& e2->dest != loop->header)
|
|
{
|
|
delete_jump_thread_path (path);
|
|
e->aux = NULL;
|
|
}
|
|
}
|
|
|
|
/* Thread the remaining edges through the former header. */
|
|
thread_block (header, false);
|
|
}
|
|
else
|
|
{
|
|
basic_block new_preheader;
|
|
|
|
/* Now consider the case entry edges are redirected to the new entry
|
|
block. Remember one entry edge, so that we can find the new
|
|
preheader (its destination after threading). */
|
|
FOR_EACH_EDGE (e, ei, header->preds)
|
|
{
|
|
if (e->aux)
|
|
break;
|
|
}
|
|
|
|
/* The duplicate of the header is the new preheader of the loop. Ensure
|
|
that it is placed correctly in the loop hierarchy. */
|
|
set_loop_copy (loop, loop_outer (loop));
|
|
|
|
thread_block (header, false);
|
|
set_loop_copy (loop, NULL);
|
|
new_preheader = e->dest;
|
|
|
|
/* Create the new latch block. This is always necessary, as the latch
|
|
must have only a single successor, but the original header had at
|
|
least two successors. */
|
|
loop->latch = NULL;
|
|
mfb_kj_edge = single_succ_edge (new_preheader);
|
|
loop->header = mfb_kj_edge->dest;
|
|
latch = make_forwarder_block (tgt_bb, mfb_keep_just, NULL);
|
|
loop->header = latch->dest;
|
|
loop->latch = latch->src;
|
|
}
|
|
|
|
return true;
|
|
|
|
fail:
|
|
/* We failed to thread anything. Cancel the requests. */
|
|
FOR_EACH_EDGE (e, ei, header->preds)
|
|
{
|
|
vec<jump_thread_edge *> *path = THREAD_PATH (e);
|
|
|
|
if (path)
|
|
{
|
|
delete_jump_thread_path (path);
|
|
e->aux = NULL;
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/* E1 and E2 are edges into the same basic block. Return TRUE if the
|
|
PHI arguments associated with those edges are equal or there are no
|
|
PHI arguments, otherwise return FALSE. */
|
|
|
|
static bool
|
|
phi_args_equal_on_edges (edge e1, edge e2)
|
|
{
|
|
gimple_stmt_iterator gsi;
|
|
int indx1 = e1->dest_idx;
|
|
int indx2 = e2->dest_idx;
|
|
|
|
for (gsi = gsi_start_phis (e1->dest); !gsi_end_p (gsi); gsi_next (&gsi))
|
|
{
|
|
gimple phi = gsi_stmt (gsi);
|
|
|
|
if (!operand_equal_p (gimple_phi_arg_def (phi, indx1),
|
|
gimple_phi_arg_def (phi, indx2), 0))
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/* Walk through the registered jump threads and convert them into a
|
|
form convenient for this pass.
|
|
|
|
Any block which has incoming edges threaded to outgoing edges
|
|
will have its entry in THREADED_BLOCK set.
|
|
|
|
Any threaded edge will have its new outgoing edge stored in the
|
|
original edge's AUX field.
|
|
|
|
This form avoids the need to walk all the edges in the CFG to
|
|
discover blocks which need processing and avoids unnecessary
|
|
hash table lookups to map from threaded edge to new target. */
|
|
|
|
static void
|
|
mark_threaded_blocks (bitmap threaded_blocks)
|
|
{
|
|
unsigned int i;
|
|
bitmap_iterator bi;
|
|
bitmap tmp = BITMAP_ALLOC (NULL);
|
|
basic_block bb;
|
|
edge e;
|
|
edge_iterator ei;
|
|
|
|
/* Move the jump threading requests from PATHS to each edge
|
|
which starts a jump thread path. */
|
|
for (i = 0; i < paths.length (); i++)
|
|
{
|
|
vec<jump_thread_edge *> *path = paths[i];
|
|
edge e = (*path)[0]->e;
|
|
e->aux = (void *)path;
|
|
bitmap_set_bit (tmp, e->dest->index);
|
|
}
|
|
|
|
|
|
|
|
/* If optimizing for size, only thread through block if we don't have
|
|
to duplicate it or it's an otherwise empty redirection block. */
|
|
if (optimize_function_for_size_p (cfun))
|
|
{
|
|
EXECUTE_IF_SET_IN_BITMAP (tmp, 0, i, bi)
|
|
{
|
|
bb = BASIC_BLOCK (i);
|
|
if (EDGE_COUNT (bb->preds) > 1
|
|
&& !redirection_block_p (bb))
|
|
{
|
|
FOR_EACH_EDGE (e, ei, bb->preds)
|
|
{
|
|
if (e->aux)
|
|
{
|
|
vec<jump_thread_edge *> *path = THREAD_PATH (e);
|
|
delete_jump_thread_path (path);
|
|
e->aux = NULL;
|
|
}
|
|
}
|
|
}
|
|
else
|
|
bitmap_set_bit (threaded_blocks, i);
|
|
}
|
|
}
|
|
else
|
|
bitmap_copy (threaded_blocks, tmp);
|
|
|
|
/* Look for jump threading paths which cross multiple loop headers.
|
|
|
|
The code to thread through loop headers will change the CFG in ways
|
|
that break assumptions made by the loop optimization code.
|
|
|
|
We don't want to blindly cancel the requests. We can instead do better
|
|
by trimming off the end of the jump thread path. */
|
|
EXECUTE_IF_SET_IN_BITMAP (tmp, 0, i, bi)
|
|
{
|
|
basic_block bb = BASIC_BLOCK (i);
|
|
FOR_EACH_EDGE (e, ei, bb->preds)
|
|
{
|
|
if (e->aux)
|
|
{
|
|
vec<jump_thread_edge *> *path = THREAD_PATH (e);
|
|
|
|
/* Basically we're looking for a situation where we can see
|
|
3 or more loop structures on a jump threading path. */
|
|
|
|
struct loop *first_father = (*path)[0]->e->src->loop_father;
|
|
struct loop *second_father = NULL;
|
|
for (unsigned int i = 0; i < path->length (); i++)
|
|
{
|
|
/* See if this is a loop father we have not seen before. */
|
|
if ((*path)[i]->e->dest->loop_father != first_father
|
|
&& (*path)[i]->e->dest->loop_father != second_father)
|
|
{
|
|
/* We've already seen two loop fathers, so we
|
|
need to trim this jump threading path. */
|
|
if (second_father != NULL)
|
|
{
|
|
/* Trim from entry I onwards. */
|
|
for (unsigned int j = i; j < path->length (); j++)
|
|
delete (*path)[j];
|
|
path->truncate (i);
|
|
|
|
/* Now that we've truncated the path, make sure
|
|
what's left is still valid. We need at least
|
|
two edges on the path and the last edge can not
|
|
be a joiner. This should never happen, but let's
|
|
be safe. */
|
|
if (path->length () < 2
|
|
|| (path->last ()->type
|
|
== EDGE_COPY_SRC_JOINER_BLOCK))
|
|
{
|
|
delete_jump_thread_path (path);
|
|
e->aux = NULL;
|
|
}
|
|
break;
|
|
}
|
|
else
|
|
{
|
|
second_father = (*path)[i]->e->dest->loop_father;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/* If we have a joiner block (J) which has two successors S1 and S2 and
|
|
we are threading though S1 and the final destination of the thread
|
|
is S2, then we must verify that any PHI nodes in S2 have the same
|
|
PHI arguments for the edge J->S2 and J->S1->...->S2.
|
|
|
|
We used to detect this prior to registering the jump thread, but
|
|
that prohibits propagation of edge equivalences into non-dominated
|
|
PHI nodes as the equivalency test might occur before propagation.
|
|
|
|
This must also occur after we truncate any jump threading paths
|
|
as this scenario may only show up after truncation.
|
|
|
|
This works for now, but will need improvement as part of the FSA
|
|
optimization.
|
|
|
|
Note since we've moved the thread request data to the edges,
|
|
we have to iterate on those rather than the threaded_edges vector. */
|
|
EXECUTE_IF_SET_IN_BITMAP (tmp, 0, i, bi)
|
|
{
|
|
bb = BASIC_BLOCK (i);
|
|
FOR_EACH_EDGE (e, ei, bb->preds)
|
|
{
|
|
if (e->aux)
|
|
{
|
|
vec<jump_thread_edge *> *path = THREAD_PATH (e);
|
|
bool have_joiner = ((*path)[1]->type == EDGE_COPY_SRC_JOINER_BLOCK);
|
|
|
|
if (have_joiner)
|
|
{
|
|
basic_block joiner = e->dest;
|
|
edge final_edge = path->last ()->e;
|
|
basic_block final_dest = final_edge->dest;
|
|
edge e2 = find_edge (joiner, final_dest);
|
|
|
|
if (e2 && !phi_args_equal_on_edges (e2, final_edge))
|
|
{
|
|
delete_jump_thread_path (path);
|
|
e->aux = NULL;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
BITMAP_FREE (tmp);
|
|
}
|
|
|
|
|
|
/* Walk through all blocks and thread incoming edges to the appropriate
|
|
outgoing edge for each edge pair recorded in THREADED_EDGES.
|
|
|
|
It is the caller's responsibility to fix the dominance information
|
|
and rewrite duplicated SSA_NAMEs back into SSA form.
|
|
|
|
If MAY_PEEL_LOOP_HEADERS is false, we avoid threading edges through
|
|
loop headers if it does not simplify the loop.
|
|
|
|
Returns true if one or more edges were threaded, false otherwise. */
|
|
|
|
bool
|
|
thread_through_all_blocks (bool may_peel_loop_headers)
|
|
{
|
|
bool retval = false;
|
|
unsigned int i;
|
|
bitmap_iterator bi;
|
|
bitmap threaded_blocks;
|
|
struct loop *loop;
|
|
loop_iterator li;
|
|
|
|
/* We must know about loops in order to preserve them. */
|
|
gcc_assert (current_loops != NULL);
|
|
|
|
if (!paths.exists ())
|
|
return false;
|
|
|
|
threaded_blocks = BITMAP_ALLOC (NULL);
|
|
memset (&thread_stats, 0, sizeof (thread_stats));
|
|
|
|
mark_threaded_blocks (threaded_blocks);
|
|
|
|
initialize_original_copy_tables ();
|
|
|
|
/* First perform the threading requests that do not affect
|
|
loop structure. */
|
|
EXECUTE_IF_SET_IN_BITMAP (threaded_blocks, 0, i, bi)
|
|
{
|
|
basic_block bb = BASIC_BLOCK (i);
|
|
|
|
if (EDGE_COUNT (bb->preds) > 0)
|
|
retval |= thread_block (bb, true);
|
|
}
|
|
|
|
/* Then perform the threading through loop headers. We start with the
|
|
innermost loop, so that the changes in cfg we perform won't affect
|
|
further threading. */
|
|
FOR_EACH_LOOP (li, loop, LI_FROM_INNERMOST)
|
|
{
|
|
if (!loop->header
|
|
|| !bitmap_bit_p (threaded_blocks, loop->header->index))
|
|
continue;
|
|
|
|
retval |= thread_through_loop_header (loop, may_peel_loop_headers);
|
|
}
|
|
|
|
/* Assume we had a jump thread path which went from the latch to the exit
|
|
and a path which goes from outside to inside the same loop.
|
|
|
|
If the latch to exit was handled first, we will thread it and clear
|
|
loop->header.
|
|
|
|
The second path will be ignored by thread_block because we're going
|
|
through a loop header. It will also be ignored by the loop above
|
|
because loop->header is NULL.
|
|
|
|
This results in the second path never being threaded. The failure
|
|
mode is a dangling AUX field.
|
|
|
|
This is inherently a bit of a pain to fix, so we just walk all the
|
|
blocks and all the incoming edges to those blocks and clear their
|
|
AUX fields. */
|
|
basic_block bb;
|
|
edge_iterator ei;
|
|
edge e;
|
|
FOR_EACH_BB (bb)
|
|
{
|
|
FOR_EACH_EDGE (e, ei, bb->preds)
|
|
if (e->aux)
|
|
{
|
|
vec<jump_thread_edge *> *path = THREAD_PATH (e);
|
|
|
|
delete_jump_thread_path (path);
|
|
e->aux = NULL;
|
|
}
|
|
}
|
|
|
|
statistics_counter_event (cfun, "Jumps threaded",
|
|
thread_stats.num_threaded_edges);
|
|
|
|
free_original_copy_tables ();
|
|
|
|
BITMAP_FREE (threaded_blocks);
|
|
threaded_blocks = NULL;
|
|
paths.release ();
|
|
|
|
if (retval)
|
|
loops_state_set (LOOPS_NEED_FIXUP);
|
|
|
|
return retval;
|
|
}
|
|
|
|
/* Delete the jump threading path PATH. We have to explcitly delete
|
|
each entry in the vector, then the container. */
|
|
|
|
void
|
|
delete_jump_thread_path (vec<jump_thread_edge *> *path)
|
|
{
|
|
for (unsigned int i = 0; i < path->length (); i++)
|
|
delete (*path)[i];
|
|
path->release();
|
|
}
|
|
|
|
/* Dump a jump threading path, including annotations about each
|
|
edge in the path. */
|
|
|
|
static void
|
|
dump_jump_thread_path (FILE *dump_file, vec<jump_thread_edge *> path)
|
|
{
|
|
fprintf (dump_file,
|
|
" Registering jump thread: (%d, %d) incoming edge; ",
|
|
path[0]->e->src->index, path[0]->e->dest->index);
|
|
|
|
for (unsigned int i = 1; i < path.length (); i++)
|
|
{
|
|
/* We can get paths with a NULL edge when the final destination
|
|
of a jump thread turns out to be a constant address. We dump
|
|
those paths when debugging, so we have to be prepared for that
|
|
possibility here. */
|
|
if (path[i]->e == NULL)
|
|
continue;
|
|
|
|
if (path[i]->type == EDGE_COPY_SRC_JOINER_BLOCK)
|
|
fprintf (dump_file, " (%d, %d) joiner; ",
|
|
path[i]->e->src->index, path[i]->e->dest->index);
|
|
if (path[i]->type == EDGE_COPY_SRC_BLOCK)
|
|
fprintf (dump_file, " (%d, %d) normal;",
|
|
path[i]->e->src->index, path[i]->e->dest->index);
|
|
if (path[i]->type == EDGE_NO_COPY_SRC_BLOCK)
|
|
fprintf (dump_file, " (%d, %d) nocopy;",
|
|
path[i]->e->src->index, path[i]->e->dest->index);
|
|
}
|
|
fputc ('\n', dump_file);
|
|
}
|
|
|
|
/* Register a jump threading opportunity. We queue up all the jump
|
|
threading opportunities discovered by a pass and update the CFG
|
|
and SSA form all at once.
|
|
|
|
E is the edge we can thread, E2 is the new target edge, i.e., we
|
|
are effectively recording that E->dest can be changed to E2->dest
|
|
after fixing the SSA graph. */
|
|
|
|
void
|
|
register_jump_thread (vec<jump_thread_edge *> *path)
|
|
{
|
|
if (!dbg_cnt (registered_jump_thread))
|
|
{
|
|
delete_jump_thread_path (path);
|
|
return;
|
|
}
|
|
|
|
/* First make sure there are no NULL outgoing edges on the jump threading
|
|
path. That can happen for jumping to a constant address. */
|
|
for (unsigned int i = 0; i < path->length (); i++)
|
|
if ((*path)[i]->e == NULL)
|
|
{
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
{
|
|
fprintf (dump_file,
|
|
"Found NULL edge in jump threading path. Cancelling jump thread:\n");
|
|
dump_jump_thread_path (dump_file, *path);
|
|
}
|
|
|
|
delete_jump_thread_path (path);
|
|
return;
|
|
}
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
dump_jump_thread_path (dump_file, *path);
|
|
|
|
if (!paths.exists ())
|
|
paths.create (5);
|
|
|
|
paths.safe_push (path);
|
|
}
|