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jeremybenn |
/* Thread edges through blocks and update the control flow and SSA graphs.
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Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010, 201
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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 "tm.h"
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#include "tree.h"
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#include "flags.h"
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#include "tm_p.h"
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#include "basic-block.h"
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#include "output.h"
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#include "function.h"
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#include "tree-flow.h"
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#include "tree-dump.h"
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#include "tree-pass.h"
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#include "cfgloop.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
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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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/* An outgoing edge from B. DUP_BLOCK will have OUTGOING_EDGE->dest as
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its single successor. */
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edge outgoing_edge;
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edge intermediate_edge;
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/* A list of incoming edges which we want to thread to
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OUTGOING_EDGE->dest. */
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struct el *incoming_edges;
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};
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/* Main data structure to hold information for duplicates of BB. */
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static htab_t redirection_data;
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/* Data structure of information to pass to hash table traversal routines. */
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struct local_info
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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(edge,heap) *threaded_edges;
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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_TARGET(E) ((edge *)(E)->aux)[0]
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#define THREAD_TARGET2(E) ((edge *)(E)->aux)[1]
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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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/* Hashing and equality routines for our hash table. */
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static hashval_t
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redirection_data_hash (const void *p)
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{
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edge e = ((const struct redirection_data *)p)->outgoing_edge;
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return e->dest->index;
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}
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static int
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redirection_data_eq (const void *p1, const void *p2)
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{
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edge e1 = ((const struct redirection_data *)p1)->outgoing_edge;
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edge e2 = ((const struct redirection_data *)p2)->outgoing_edge;
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edge e3 = ((const struct redirection_data *)p1)->intermediate_edge;
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edge e4 = ((const struct redirection_data *)p2)->intermediate_edge;
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return e1 == e2 && e3 == e4;
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}
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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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void **slot;
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struct redirection_data *elt;
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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->intermediate_edge = THREAD_TARGET2 (e) ? THREAD_TARGET (e) : NULL;
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elt->outgoing_edge = THREAD_TARGET2 (e) ? THREAD_TARGET2 (e)
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: THREAD_TARGET (e);
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elt->dup_block = NULL;
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elt->incoming_edges = NULL;
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slot = htab_find_slot (redirection_data, 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 = (void *)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 = (struct redirection_data *) *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->outgoing_edge->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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if (rd->outgoing_edge->aux)
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361 |
|
|
{
|
362 |
|
|
e->aux = (edge *) XNEWVEC (edge, 2);
|
363 |
|
|
THREAD_TARGET(e) = THREAD_TARGET (rd->outgoing_edge);
|
364 |
|
|
THREAD_TARGET2(e) = THREAD_TARGET2 (rd->outgoing_edge);
|
365 |
|
|
}
|
366 |
|
|
else
|
367 |
|
|
{
|
368 |
|
|
e->aux = NULL;
|
369 |
|
|
}
|
370 |
|
|
|
371 |
|
|
/* If there are any PHI nodes at the destination of the outgoing edge
|
372 |
|
|
from the duplicate block, then we will need to add a new argument
|
373 |
|
|
to them. The argument should have the same value as the argument
|
374 |
|
|
associated with the outgoing edge stored in RD. */
|
375 |
|
|
copy_phi_args (e->dest, rd->outgoing_edge, e);
|
376 |
|
|
}
|
377 |
|
|
|
378 |
|
|
/* Wire up the outgoing edges from the duplicate block and
|
379 |
|
|
update any PHIs as needed. */
|
380 |
|
|
static void
|
381 |
|
|
fix_duplicate_block_edges (struct redirection_data *rd,
|
382 |
|
|
struct local_info *local_info)
|
383 |
|
|
{
|
384 |
|
|
/* If we were threading through an joiner block, then we want
|
385 |
|
|
to keep its control statement and redirect an outgoing edge.
|
386 |
|
|
Else we want to remove the control statement & edges, then create
|
387 |
|
|
a new outgoing edge. In both cases we may need to update PHIs. */
|
388 |
|
|
if (THREAD_TARGET2 (rd->incoming_edges->e))
|
389 |
|
|
{
|
390 |
|
|
edge victim;
|
391 |
|
|
edge e2;
|
392 |
|
|
edge e = rd->incoming_edges->e;
|
393 |
|
|
|
394 |
|
|
/* This updates the PHIs at the destination of the duplicate
|
395 |
|
|
block. */
|
396 |
|
|
update_destination_phis (local_info->bb, rd->dup_block);
|
397 |
|
|
|
398 |
|
|
/* Find the edge from the duplicate block to the block we're
|
399 |
|
|
threading through. That's the edge we want to redirect. */
|
400 |
|
|
victim = find_edge (rd->dup_block, THREAD_TARGET (e)->dest);
|
401 |
|
|
e2 = redirect_edge_and_branch (victim, THREAD_TARGET2 (e)->dest);
|
402 |
|
|
|
403 |
|
|
/* If we redirected the edge, then we need to copy PHI arguments
|
404 |
|
|
at the target. If the edge already existed (e2 != victim case),
|
405 |
|
|
then the PHIs in the target already have the correct arguments. */
|
406 |
|
|
if (e2 == victim)
|
407 |
|
|
copy_phi_args (e2->dest, THREAD_TARGET2 (e), e2);
|
408 |
|
|
}
|
409 |
|
|
else
|
410 |
|
|
{
|
411 |
|
|
remove_ctrl_stmt_and_useless_edges (rd->dup_block, NULL);
|
412 |
|
|
create_edge_and_update_destination_phis (rd, rd->dup_block);
|
413 |
|
|
}
|
414 |
|
|
}
|
415 |
|
|
/* Hash table traversal callback routine to create duplicate blocks. */
|
416 |
|
|
|
417 |
|
|
static int
|
418 |
|
|
create_duplicates (void **slot, void *data)
|
419 |
|
|
{
|
420 |
|
|
struct redirection_data *rd = (struct redirection_data *) *slot;
|
421 |
|
|
struct local_info *local_info = (struct local_info *)data;
|
422 |
|
|
|
423 |
|
|
/* Create a template block if we have not done so already. Otherwise
|
424 |
|
|
use the template to create a new block. */
|
425 |
|
|
if (local_info->template_block == NULL)
|
426 |
|
|
{
|
427 |
|
|
create_block_for_threading (local_info->bb, rd);
|
428 |
|
|
local_info->template_block = rd->dup_block;
|
429 |
|
|
|
430 |
|
|
/* We do not create any outgoing edges for the template. We will
|
431 |
|
|
take care of that in a later traversal. That way we do not
|
432 |
|
|
create edges that are going to just be deleted. */
|
433 |
|
|
}
|
434 |
|
|
else
|
435 |
|
|
{
|
436 |
|
|
create_block_for_threading (local_info->template_block, rd);
|
437 |
|
|
|
438 |
|
|
/* Go ahead and wire up outgoing edges and update PHIs for the duplicate
|
439 |
|
|
block. */
|
440 |
|
|
fix_duplicate_block_edges (rd, local_info);
|
441 |
|
|
}
|
442 |
|
|
|
443 |
|
|
/* Keep walking the hash table. */
|
444 |
|
|
return 1;
|
445 |
|
|
}
|
446 |
|
|
|
447 |
|
|
/* We did not create any outgoing edges for the template block during
|
448 |
|
|
block creation. This hash table traversal callback creates the
|
449 |
|
|
outgoing edge for the template block. */
|
450 |
|
|
|
451 |
|
|
static int
|
452 |
|
|
fixup_template_block (void **slot, void *data)
|
453 |
|
|
{
|
454 |
|
|
struct redirection_data *rd = (struct redirection_data *) *slot;
|
455 |
|
|
struct local_info *local_info = (struct local_info *)data;
|
456 |
|
|
|
457 |
|
|
/* If this is the template block halt the traversal after updating
|
458 |
|
|
it appropriately.
|
459 |
|
|
|
460 |
|
|
If we were threading through an joiner block, then we want
|
461 |
|
|
to keep its control statement and redirect an outgoing edge.
|
462 |
|
|
Else we want to remove the control statement & edges, then create
|
463 |
|
|
a new outgoing edge. In both cases we may need to update PHIs. */
|
464 |
|
|
if (rd->dup_block && rd->dup_block == local_info->template_block)
|
465 |
|
|
{
|
466 |
|
|
fix_duplicate_block_edges (rd, local_info);
|
467 |
|
|
return 0;
|
468 |
|
|
}
|
469 |
|
|
|
470 |
|
|
return 1;
|
471 |
|
|
}
|
472 |
|
|
|
473 |
|
|
/* Hash table traversal callback to redirect each incoming edge
|
474 |
|
|
associated with this hash table element to its new destination. */
|
475 |
|
|
|
476 |
|
|
static int
|
477 |
|
|
redirect_edges (void **slot, void *data)
|
478 |
|
|
{
|
479 |
|
|
struct redirection_data *rd = (struct redirection_data *) *slot;
|
480 |
|
|
struct local_info *local_info = (struct local_info *)data;
|
481 |
|
|
struct el *next, *el;
|
482 |
|
|
|
483 |
|
|
/* Walk over all the incoming edges associated associated with this
|
484 |
|
|
hash table entry. */
|
485 |
|
|
for (el = rd->incoming_edges; el; el = next)
|
486 |
|
|
{
|
487 |
|
|
edge e = el->e;
|
488 |
|
|
|
489 |
|
|
/* Go ahead and free this element from the list. Doing this now
|
490 |
|
|
avoids the need for another list walk when we destroy the hash
|
491 |
|
|
table. */
|
492 |
|
|
next = el->next;
|
493 |
|
|
free (el);
|
494 |
|
|
|
495 |
|
|
thread_stats.num_threaded_edges++;
|
496 |
|
|
/* If we are threading through a joiner block, then we have to
|
497 |
|
|
find the edge we want to redirect and update some PHI nodes. */
|
498 |
|
|
if (THREAD_TARGET2 (e))
|
499 |
|
|
{
|
500 |
|
|
edge e2;
|
501 |
|
|
|
502 |
|
|
/* We want to redirect the incoming edge to the joiner block (E)
|
503 |
|
|
to instead reach the duplicate of the joiner block. */
|
504 |
|
|
e2 = redirect_edge_and_branch (e, rd->dup_block);
|
505 |
|
|
flush_pending_stmts (e2);
|
506 |
|
|
}
|
507 |
|
|
else if (rd->dup_block)
|
508 |
|
|
{
|
509 |
|
|
edge e2;
|
510 |
|
|
|
511 |
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
512 |
|
|
fprintf (dump_file, " Threaded jump %d --> %d to %d\n",
|
513 |
|
|
e->src->index, e->dest->index, rd->dup_block->index);
|
514 |
|
|
|
515 |
|
|
rd->dup_block->count += e->count;
|
516 |
|
|
|
517 |
|
|
/* Excessive jump threading may make frequencies large enough so
|
518 |
|
|
the computation overflows. */
|
519 |
|
|
if (rd->dup_block->frequency < BB_FREQ_MAX * 2)
|
520 |
|
|
rd->dup_block->frequency += EDGE_FREQUENCY (e);
|
521 |
|
|
EDGE_SUCC (rd->dup_block, 0)->count += e->count;
|
522 |
|
|
/* Redirect the incoming edge to the appropriate duplicate
|
523 |
|
|
block. */
|
524 |
|
|
e2 = redirect_edge_and_branch (e, rd->dup_block);
|
525 |
|
|
gcc_assert (e == e2);
|
526 |
|
|
flush_pending_stmts (e2);
|
527 |
|
|
}
|
528 |
|
|
|
529 |
|
|
/* Go ahead and clear E->aux. It's not needed anymore and failure
|
530 |
|
|
to clear it will cause all kinds of unpleasant problems later. */
|
531 |
|
|
free (e->aux);
|
532 |
|
|
e->aux = NULL;
|
533 |
|
|
|
534 |
|
|
}
|
535 |
|
|
|
536 |
|
|
/* Indicate that we actually threaded one or more jumps. */
|
537 |
|
|
if (rd->incoming_edges)
|
538 |
|
|
local_info->jumps_threaded = true;
|
539 |
|
|
|
540 |
|
|
return 1;
|
541 |
|
|
}
|
542 |
|
|
|
543 |
|
|
/* Return true if this block has no executable statements other than
|
544 |
|
|
a simple ctrl flow instruction. When the number of outgoing edges
|
545 |
|
|
is one, this is equivalent to a "forwarder" block. */
|
546 |
|
|
|
547 |
|
|
static bool
|
548 |
|
|
redirection_block_p (basic_block bb)
|
549 |
|
|
{
|
550 |
|
|
gimple_stmt_iterator gsi;
|
551 |
|
|
|
552 |
|
|
/* Advance to the first executable statement. */
|
553 |
|
|
gsi = gsi_start_bb (bb);
|
554 |
|
|
while (!gsi_end_p (gsi)
|
555 |
|
|
&& (gimple_code (gsi_stmt (gsi)) == GIMPLE_LABEL
|
556 |
|
|
|| is_gimple_debug (gsi_stmt (gsi))
|
557 |
|
|
|| gimple_nop_p (gsi_stmt (gsi))))
|
558 |
|
|
gsi_next (&gsi);
|
559 |
|
|
|
560 |
|
|
/* Check if this is an empty block. */
|
561 |
|
|
if (gsi_end_p (gsi))
|
562 |
|
|
return true;
|
563 |
|
|
|
564 |
|
|
/* Test that we've reached the terminating control statement. */
|
565 |
|
|
return gsi_stmt (gsi)
|
566 |
|
|
&& (gimple_code (gsi_stmt (gsi)) == GIMPLE_COND
|
567 |
|
|
|| gimple_code (gsi_stmt (gsi)) == GIMPLE_GOTO
|
568 |
|
|
|| gimple_code (gsi_stmt (gsi)) == GIMPLE_SWITCH);
|
569 |
|
|
}
|
570 |
|
|
|
571 |
|
|
/* BB is a block which ends with a COND_EXPR or SWITCH_EXPR and when BB
|
572 |
|
|
is reached via one or more specific incoming edges, we know which
|
573 |
|
|
outgoing edge from BB will be traversed.
|
574 |
|
|
|
575 |
|
|
We want to redirect those incoming edges to the target of the
|
576 |
|
|
appropriate outgoing edge. Doing so avoids a conditional branch
|
577 |
|
|
and may expose new optimization opportunities. Note that we have
|
578 |
|
|
to update dominator tree and SSA graph after such changes.
|
579 |
|
|
|
580 |
|
|
The key to keeping the SSA graph update manageable is to duplicate
|
581 |
|
|
the side effects occurring in BB so that those side effects still
|
582 |
|
|
occur on the paths which bypass BB after redirecting edges.
|
583 |
|
|
|
584 |
|
|
We accomplish this by creating duplicates of BB and arranging for
|
585 |
|
|
the duplicates to unconditionally pass control to one specific
|
586 |
|
|
successor of BB. We then revector the incoming edges into BB to
|
587 |
|
|
the appropriate duplicate of BB.
|
588 |
|
|
|
589 |
|
|
If NOLOOP_ONLY is true, we only perform the threading as long as it
|
590 |
|
|
does not affect the structure of the loops in a nontrivial way. */
|
591 |
|
|
|
592 |
|
|
static bool
|
593 |
|
|
thread_block (basic_block bb, bool noloop_only)
|
594 |
|
|
{
|
595 |
|
|
/* E is an incoming edge into BB that we may or may not want to
|
596 |
|
|
redirect to a duplicate of BB. */
|
597 |
|
|
edge e, e2;
|
598 |
|
|
edge_iterator ei;
|
599 |
|
|
struct local_info local_info;
|
600 |
|
|
struct loop *loop = bb->loop_father;
|
601 |
|
|
|
602 |
|
|
/* To avoid scanning a linear array for the element we need we instead
|
603 |
|
|
use a hash table. For normal code there should be no noticeable
|
604 |
|
|
difference. However, if we have a block with a large number of
|
605 |
|
|
incoming and outgoing edges such linear searches can get expensive. */
|
606 |
|
|
redirection_data = htab_create (EDGE_COUNT (bb->succs),
|
607 |
|
|
redirection_data_hash,
|
608 |
|
|
redirection_data_eq,
|
609 |
|
|
free);
|
610 |
|
|
|
611 |
|
|
/* If we thread the latch of the loop to its exit, the loop ceases to
|
612 |
|
|
exist. Make sure we do not restrict ourselves in order to preserve
|
613 |
|
|
this loop. */
|
614 |
|
|
if (loop->header == bb)
|
615 |
|
|
{
|
616 |
|
|
e = loop_latch_edge (loop);
|
617 |
|
|
|
618 |
|
|
if (e->aux)
|
619 |
|
|
e2 = THREAD_TARGET (e);
|
620 |
|
|
else
|
621 |
|
|
e2 = NULL;
|
622 |
|
|
|
623 |
|
|
if (e2 && loop_exit_edge_p (loop, e2))
|
624 |
|
|
{
|
625 |
|
|
loop->header = NULL;
|
626 |
|
|
loop->latch = NULL;
|
627 |
|
|
}
|
628 |
|
|
}
|
629 |
|
|
|
630 |
|
|
/* Record each unique threaded destination into a hash table for
|
631 |
|
|
efficient lookups. */
|
632 |
|
|
FOR_EACH_EDGE (e, ei, bb->preds)
|
633 |
|
|
{
|
634 |
|
|
if (e->aux == NULL)
|
635 |
|
|
continue;
|
636 |
|
|
|
637 |
|
|
if (THREAD_TARGET2 (e))
|
638 |
|
|
e2 = THREAD_TARGET2 (e);
|
639 |
|
|
else
|
640 |
|
|
e2 = THREAD_TARGET (e);
|
641 |
|
|
|
642 |
|
|
if (!e2
|
643 |
|
|
/* If NOLOOP_ONLY is true, we only allow threading through the
|
644 |
|
|
header of a loop to exit edges. */
|
645 |
|
|
|| (noloop_only
|
646 |
|
|
&& bb == bb->loop_father->header
|
647 |
|
|
&& (!loop_exit_edge_p (bb->loop_father, e2)
|
648 |
|
|
|| THREAD_TARGET2 (e))))
|
649 |
|
|
continue;
|
650 |
|
|
|
651 |
|
|
if (e->dest == e2->src)
|
652 |
|
|
update_bb_profile_for_threading (e->dest, EDGE_FREQUENCY (e),
|
653 |
|
|
e->count, THREAD_TARGET (e));
|
654 |
|
|
|
655 |
|
|
/* Insert the outgoing edge into the hash table if it is not
|
656 |
|
|
already in the hash table. */
|
657 |
|
|
lookup_redirection_data (e, INSERT);
|
658 |
|
|
}
|
659 |
|
|
|
660 |
|
|
/* We do not update dominance info. */
|
661 |
|
|
free_dominance_info (CDI_DOMINATORS);
|
662 |
|
|
|
663 |
|
|
/* Now create duplicates of BB.
|
664 |
|
|
|
665 |
|
|
Note that for a block with a high outgoing degree we can waste
|
666 |
|
|
a lot of time and memory creating and destroying useless edges.
|
667 |
|
|
|
668 |
|
|
So we first duplicate BB and remove the control structure at the
|
669 |
|
|
tail of the duplicate as well as all outgoing edges from the
|
670 |
|
|
duplicate. We then use that duplicate block as a template for
|
671 |
|
|
the rest of the duplicates. */
|
672 |
|
|
local_info.template_block = NULL;
|
673 |
|
|
local_info.bb = bb;
|
674 |
|
|
local_info.jumps_threaded = false;
|
675 |
|
|
htab_traverse (redirection_data, create_duplicates, &local_info);
|
676 |
|
|
|
677 |
|
|
/* The template does not have an outgoing edge. Create that outgoing
|
678 |
|
|
edge and update PHI nodes as the edge's target as necessary.
|
679 |
|
|
|
680 |
|
|
We do this after creating all the duplicates to avoid creating
|
681 |
|
|
unnecessary edges. */
|
682 |
|
|
htab_traverse (redirection_data, fixup_template_block, &local_info);
|
683 |
|
|
|
684 |
|
|
/* The hash table traversals above created the duplicate blocks (and the
|
685 |
|
|
statements within the duplicate blocks). This loop creates PHI nodes for
|
686 |
|
|
the duplicated blocks and redirects the incoming edges into BB to reach
|
687 |
|
|
the duplicates of BB. */
|
688 |
|
|
htab_traverse (redirection_data, redirect_edges, &local_info);
|
689 |
|
|
|
690 |
|
|
/* Done with this block. Clear REDIRECTION_DATA. */
|
691 |
|
|
htab_delete (redirection_data);
|
692 |
|
|
redirection_data = NULL;
|
693 |
|
|
|
694 |
|
|
/* Indicate to our caller whether or not any jumps were threaded. */
|
695 |
|
|
return local_info.jumps_threaded;
|
696 |
|
|
}
|
697 |
|
|
|
698 |
|
|
/* Threads edge E through E->dest to the edge THREAD_TARGET (E). Returns the
|
699 |
|
|
copy of E->dest created during threading, or E->dest if it was not necessary
|
700 |
|
|
to copy it (E is its single predecessor). */
|
701 |
|
|
|
702 |
|
|
static basic_block
|
703 |
|
|
thread_single_edge (edge e)
|
704 |
|
|
{
|
705 |
|
|
basic_block bb = e->dest;
|
706 |
|
|
edge eto = THREAD_TARGET (e);
|
707 |
|
|
struct redirection_data rd;
|
708 |
|
|
|
709 |
|
|
free (e->aux);
|
710 |
|
|
e->aux = NULL;
|
711 |
|
|
|
712 |
|
|
thread_stats.num_threaded_edges++;
|
713 |
|
|
|
714 |
|
|
if (single_pred_p (bb))
|
715 |
|
|
{
|
716 |
|
|
/* If BB has just a single predecessor, we should only remove the
|
717 |
|
|
control statements at its end, and successors except for ETO. */
|
718 |
|
|
remove_ctrl_stmt_and_useless_edges (bb, eto->dest);
|
719 |
|
|
|
720 |
|
|
/* And fixup the flags on the single remaining edge. */
|
721 |
|
|
eto->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE | EDGE_ABNORMAL);
|
722 |
|
|
eto->flags |= EDGE_FALLTHRU;
|
723 |
|
|
|
724 |
|
|
return bb;
|
725 |
|
|
}
|
726 |
|
|
|
727 |
|
|
/* Otherwise, we need to create a copy. */
|
728 |
|
|
if (e->dest == eto->src)
|
729 |
|
|
update_bb_profile_for_threading (bb, EDGE_FREQUENCY (e), e->count, eto);
|
730 |
|
|
|
731 |
|
|
rd.outgoing_edge = eto;
|
732 |
|
|
|
733 |
|
|
create_block_for_threading (bb, &rd);
|
734 |
|
|
remove_ctrl_stmt_and_useless_edges (rd.dup_block, NULL);
|
735 |
|
|
create_edge_and_update_destination_phis (&rd, rd.dup_block);
|
736 |
|
|
|
737 |
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
738 |
|
|
fprintf (dump_file, " Threaded jump %d --> %d to %d\n",
|
739 |
|
|
e->src->index, e->dest->index, rd.dup_block->index);
|
740 |
|
|
|
741 |
|
|
rd.dup_block->count = e->count;
|
742 |
|
|
rd.dup_block->frequency = EDGE_FREQUENCY (e);
|
743 |
|
|
single_succ_edge (rd.dup_block)->count = e->count;
|
744 |
|
|
redirect_edge_and_branch (e, rd.dup_block);
|
745 |
|
|
flush_pending_stmts (e);
|
746 |
|
|
|
747 |
|
|
return rd.dup_block;
|
748 |
|
|
}
|
749 |
|
|
|
750 |
|
|
/* Callback for dfs_enumerate_from. Returns true if BB is different
|
751 |
|
|
from STOP and DBDS_CE_STOP. */
|
752 |
|
|
|
753 |
|
|
static basic_block dbds_ce_stop;
|
754 |
|
|
static bool
|
755 |
|
|
dbds_continue_enumeration_p (const_basic_block bb, const void *stop)
|
756 |
|
|
{
|
757 |
|
|
return (bb != (const_basic_block) stop
|
758 |
|
|
&& bb != dbds_ce_stop);
|
759 |
|
|
}
|
760 |
|
|
|
761 |
|
|
/* Evaluates the dominance relationship of latch of the LOOP and BB, and
|
762 |
|
|
returns the state. */
|
763 |
|
|
|
764 |
|
|
enum bb_dom_status
|
765 |
|
|
{
|
766 |
|
|
/* BB does not dominate latch of the LOOP. */
|
767 |
|
|
DOMST_NONDOMINATING,
|
768 |
|
|
/* The LOOP is broken (there is no path from the header to its latch. */
|
769 |
|
|
DOMST_LOOP_BROKEN,
|
770 |
|
|
/* BB dominates the latch of the LOOP. */
|
771 |
|
|
DOMST_DOMINATING
|
772 |
|
|
};
|
773 |
|
|
|
774 |
|
|
static enum bb_dom_status
|
775 |
|
|
determine_bb_domination_status (struct loop *loop, basic_block bb)
|
776 |
|
|
{
|
777 |
|
|
basic_block *bblocks;
|
778 |
|
|
unsigned nblocks, i;
|
779 |
|
|
bool bb_reachable = false;
|
780 |
|
|
edge_iterator ei;
|
781 |
|
|
edge e;
|
782 |
|
|
|
783 |
|
|
/* This function assumes BB is a successor of LOOP->header.
|
784 |
|
|
If that is not the case return DOMST_NONDOMINATING which
|
785 |
|
|
is always safe. */
|
786 |
|
|
{
|
787 |
|
|
bool ok = false;
|
788 |
|
|
|
789 |
|
|
FOR_EACH_EDGE (e, ei, bb->preds)
|
790 |
|
|
{
|
791 |
|
|
if (e->src == loop->header)
|
792 |
|
|
{
|
793 |
|
|
ok = true;
|
794 |
|
|
break;
|
795 |
|
|
}
|
796 |
|
|
}
|
797 |
|
|
|
798 |
|
|
if (!ok)
|
799 |
|
|
return DOMST_NONDOMINATING;
|
800 |
|
|
}
|
801 |
|
|
|
802 |
|
|
if (bb == loop->latch)
|
803 |
|
|
return DOMST_DOMINATING;
|
804 |
|
|
|
805 |
|
|
/* Check that BB dominates LOOP->latch, and that it is back-reachable
|
806 |
|
|
from it. */
|
807 |
|
|
|
808 |
|
|
bblocks = XCNEWVEC (basic_block, loop->num_nodes);
|
809 |
|
|
dbds_ce_stop = loop->header;
|
810 |
|
|
nblocks = dfs_enumerate_from (loop->latch, 1, dbds_continue_enumeration_p,
|
811 |
|
|
bblocks, loop->num_nodes, bb);
|
812 |
|
|
for (i = 0; i < nblocks; i++)
|
813 |
|
|
FOR_EACH_EDGE (e, ei, bblocks[i]->preds)
|
814 |
|
|
{
|
815 |
|
|
if (e->src == loop->header)
|
816 |
|
|
{
|
817 |
|
|
free (bblocks);
|
818 |
|
|
return DOMST_NONDOMINATING;
|
819 |
|
|
}
|
820 |
|
|
if (e->src == bb)
|
821 |
|
|
bb_reachable = true;
|
822 |
|
|
}
|
823 |
|
|
|
824 |
|
|
free (bblocks);
|
825 |
|
|
return (bb_reachable ? DOMST_DOMINATING : DOMST_LOOP_BROKEN);
|
826 |
|
|
}
|
827 |
|
|
|
828 |
|
|
/* Thread jumps through the header of LOOP. Returns true if cfg changes.
|
829 |
|
|
If MAY_PEEL_LOOP_HEADERS is false, we avoid threading from entry edges
|
830 |
|
|
to the inside of the loop. */
|
831 |
|
|
|
832 |
|
|
static bool
|
833 |
|
|
thread_through_loop_header (struct loop *loop, bool may_peel_loop_headers)
|
834 |
|
|
{
|
835 |
|
|
basic_block header = loop->header;
|
836 |
|
|
edge e, tgt_edge, latch = loop_latch_edge (loop);
|
837 |
|
|
edge_iterator ei;
|
838 |
|
|
basic_block tgt_bb, atgt_bb;
|
839 |
|
|
enum bb_dom_status domst;
|
840 |
|
|
|
841 |
|
|
/* We have already threaded through headers to exits, so all the threading
|
842 |
|
|
requests now are to the inside of the loop. We need to avoid creating
|
843 |
|
|
irreducible regions (i.e., loops with more than one entry block), and
|
844 |
|
|
also loop with several latch edges, or new subloops of the loop (although
|
845 |
|
|
there are cases where it might be appropriate, it is difficult to decide,
|
846 |
|
|
and doing it wrongly may confuse other optimizers).
|
847 |
|
|
|
848 |
|
|
We could handle more general cases here. However, the intention is to
|
849 |
|
|
preserve some information about the loop, which is impossible if its
|
850 |
|
|
structure changes significantly, in a way that is not well understood.
|
851 |
|
|
Thus we only handle few important special cases, in which also updating
|
852 |
|
|
of the loop-carried information should be feasible:
|
853 |
|
|
|
854 |
|
|
1) Propagation of latch edge to a block that dominates the latch block
|
855 |
|
|
of a loop. This aims to handle the following idiom:
|
856 |
|
|
|
857 |
|
|
first = 1;
|
858 |
|
|
while (1)
|
859 |
|
|
{
|
860 |
|
|
if (first)
|
861 |
|
|
initialize;
|
862 |
|
|
first = 0;
|
863 |
|
|
body;
|
864 |
|
|
}
|
865 |
|
|
|
866 |
|
|
After threading the latch edge, this becomes
|
867 |
|
|
|
868 |
|
|
first = 1;
|
869 |
|
|
if (first)
|
870 |
|
|
initialize;
|
871 |
|
|
while (1)
|
872 |
|
|
{
|
873 |
|
|
first = 0;
|
874 |
|
|
body;
|
875 |
|
|
}
|
876 |
|
|
|
877 |
|
|
The original header of the loop is moved out of it, and we may thread
|
878 |
|
|
the remaining edges through it without further constraints.
|
879 |
|
|
|
880 |
|
|
2) All entry edges are propagated to a single basic block that dominates
|
881 |
|
|
the latch block of the loop. This aims to handle the following idiom
|
882 |
|
|
(normally created for "for" loops):
|
883 |
|
|
|
884 |
|
|
i = 0;
|
885 |
|
|
while (1)
|
886 |
|
|
{
|
887 |
|
|
if (i >= 100)
|
888 |
|
|
break;
|
889 |
|
|
body;
|
890 |
|
|
i++;
|
891 |
|
|
}
|
892 |
|
|
|
893 |
|
|
This becomes
|
894 |
|
|
|
895 |
|
|
i = 0;
|
896 |
|
|
while (1)
|
897 |
|
|
{
|
898 |
|
|
body;
|
899 |
|
|
i++;
|
900 |
|
|
if (i >= 100)
|
901 |
|
|
break;
|
902 |
|
|
}
|
903 |
|
|
*/
|
904 |
|
|
|
905 |
|
|
/* Threading through the header won't improve the code if the header has just
|
906 |
|
|
one successor. */
|
907 |
|
|
if (single_succ_p (header))
|
908 |
|
|
goto fail;
|
909 |
|
|
|
910 |
|
|
if (latch->aux)
|
911 |
|
|
{
|
912 |
|
|
if (THREAD_TARGET2 (latch))
|
913 |
|
|
goto fail;
|
914 |
|
|
tgt_edge = THREAD_TARGET (latch);
|
915 |
|
|
tgt_bb = tgt_edge->dest;
|
916 |
|
|
}
|
917 |
|
|
else if (!may_peel_loop_headers
|
918 |
|
|
&& !redirection_block_p (loop->header))
|
919 |
|
|
goto fail;
|
920 |
|
|
else
|
921 |
|
|
{
|
922 |
|
|
tgt_bb = NULL;
|
923 |
|
|
tgt_edge = NULL;
|
924 |
|
|
FOR_EACH_EDGE (e, ei, header->preds)
|
925 |
|
|
{
|
926 |
|
|
if (!e->aux)
|
927 |
|
|
{
|
928 |
|
|
if (e == latch)
|
929 |
|
|
continue;
|
930 |
|
|
|
931 |
|
|
/* If latch is not threaded, and there is a header
|
932 |
|
|
edge that is not threaded, we would create loop
|
933 |
|
|
with multiple entries. */
|
934 |
|
|
goto fail;
|
935 |
|
|
}
|
936 |
|
|
|
937 |
|
|
if (THREAD_TARGET2 (e))
|
938 |
|
|
goto fail;
|
939 |
|
|
tgt_edge = THREAD_TARGET (e);
|
940 |
|
|
atgt_bb = tgt_edge->dest;
|
941 |
|
|
if (!tgt_bb)
|
942 |
|
|
tgt_bb = atgt_bb;
|
943 |
|
|
/* Two targets of threading would make us create loop
|
944 |
|
|
with multiple entries. */
|
945 |
|
|
else if (tgt_bb != atgt_bb)
|
946 |
|
|
goto fail;
|
947 |
|
|
}
|
948 |
|
|
|
949 |
|
|
if (!tgt_bb)
|
950 |
|
|
{
|
951 |
|
|
/* There are no threading requests. */
|
952 |
|
|
return false;
|
953 |
|
|
}
|
954 |
|
|
|
955 |
|
|
/* Redirecting to empty loop latch is useless. */
|
956 |
|
|
if (tgt_bb == loop->latch
|
957 |
|
|
&& empty_block_p (loop->latch))
|
958 |
|
|
goto fail;
|
959 |
|
|
}
|
960 |
|
|
|
961 |
|
|
/* The target block must dominate the loop latch, otherwise we would be
|
962 |
|
|
creating a subloop. */
|
963 |
|
|
domst = determine_bb_domination_status (loop, tgt_bb);
|
964 |
|
|
if (domst == DOMST_NONDOMINATING)
|
965 |
|
|
goto fail;
|
966 |
|
|
if (domst == DOMST_LOOP_BROKEN)
|
967 |
|
|
{
|
968 |
|
|
/* If the loop ceased to exist, mark it as such, and thread through its
|
969 |
|
|
original header. */
|
970 |
|
|
loop->header = NULL;
|
971 |
|
|
loop->latch = NULL;
|
972 |
|
|
return thread_block (header, false);
|
973 |
|
|
}
|
974 |
|
|
|
975 |
|
|
if (tgt_bb->loop_father->header == tgt_bb)
|
976 |
|
|
{
|
977 |
|
|
/* If the target of the threading is a header of a subloop, we need
|
978 |
|
|
to create a preheader for it, so that the headers of the two loops
|
979 |
|
|
do not merge. */
|
980 |
|
|
if (EDGE_COUNT (tgt_bb->preds) > 2)
|
981 |
|
|
{
|
982 |
|
|
tgt_bb = create_preheader (tgt_bb->loop_father, 0);
|
983 |
|
|
gcc_assert (tgt_bb != NULL);
|
984 |
|
|
}
|
985 |
|
|
else
|
986 |
|
|
tgt_bb = split_edge (tgt_edge);
|
987 |
|
|
}
|
988 |
|
|
|
989 |
|
|
if (latch->aux)
|
990 |
|
|
{
|
991 |
|
|
/* First handle the case latch edge is redirected. */
|
992 |
|
|
loop->latch = thread_single_edge (latch);
|
993 |
|
|
gcc_assert (single_succ (loop->latch) == tgt_bb);
|
994 |
|
|
loop->header = tgt_bb;
|
995 |
|
|
|
996 |
|
|
/* Thread the remaining edges through the former header. */
|
997 |
|
|
thread_block (header, false);
|
998 |
|
|
}
|
999 |
|
|
else
|
1000 |
|
|
{
|
1001 |
|
|
basic_block new_preheader;
|
1002 |
|
|
|
1003 |
|
|
/* Now consider the case entry edges are redirected to the new entry
|
1004 |
|
|
block. Remember one entry edge, so that we can find the new
|
1005 |
|
|
preheader (its destination after threading). */
|
1006 |
|
|
FOR_EACH_EDGE (e, ei, header->preds)
|
1007 |
|
|
{
|
1008 |
|
|
if (e->aux)
|
1009 |
|
|
break;
|
1010 |
|
|
}
|
1011 |
|
|
|
1012 |
|
|
/* The duplicate of the header is the new preheader of the loop. Ensure
|
1013 |
|
|
that it is placed correctly in the loop hierarchy. */
|
1014 |
|
|
set_loop_copy (loop, loop_outer (loop));
|
1015 |
|
|
|
1016 |
|
|
thread_block (header, false);
|
1017 |
|
|
set_loop_copy (loop, NULL);
|
1018 |
|
|
new_preheader = e->dest;
|
1019 |
|
|
|
1020 |
|
|
/* Create the new latch block. This is always necessary, as the latch
|
1021 |
|
|
must have only a single successor, but the original header had at
|
1022 |
|
|
least two successors. */
|
1023 |
|
|
loop->latch = NULL;
|
1024 |
|
|
mfb_kj_edge = single_succ_edge (new_preheader);
|
1025 |
|
|
loop->header = mfb_kj_edge->dest;
|
1026 |
|
|
latch = make_forwarder_block (tgt_bb, mfb_keep_just, NULL);
|
1027 |
|
|
loop->header = latch->dest;
|
1028 |
|
|
loop->latch = latch->src;
|
1029 |
|
|
}
|
1030 |
|
|
|
1031 |
|
|
return true;
|
1032 |
|
|
|
1033 |
|
|
fail:
|
1034 |
|
|
/* We failed to thread anything. Cancel the requests. */
|
1035 |
|
|
FOR_EACH_EDGE (e, ei, header->preds)
|
1036 |
|
|
{
|
1037 |
|
|
free (e->aux);
|
1038 |
|
|
e->aux = NULL;
|
1039 |
|
|
}
|
1040 |
|
|
return false;
|
1041 |
|
|
}
|
1042 |
|
|
|
1043 |
|
|
/* Walk through the registered jump threads and convert them into a
|
1044 |
|
|
form convenient for this pass.
|
1045 |
|
|
|
1046 |
|
|
Any block which has incoming edges threaded to outgoing edges
|
1047 |
|
|
will have its entry in THREADED_BLOCK set.
|
1048 |
|
|
|
1049 |
|
|
Any threaded edge will have its new outgoing edge stored in the
|
1050 |
|
|
original edge's AUX field.
|
1051 |
|
|
|
1052 |
|
|
This form avoids the need to walk all the edges in the CFG to
|
1053 |
|
|
discover blocks which need processing and avoids unnecessary
|
1054 |
|
|
hash table lookups to map from threaded edge to new target. */
|
1055 |
|
|
|
1056 |
|
|
static void
|
1057 |
|
|
mark_threaded_blocks (bitmap threaded_blocks)
|
1058 |
|
|
{
|
1059 |
|
|
unsigned int i;
|
1060 |
|
|
bitmap_iterator bi;
|
1061 |
|
|
bitmap tmp = BITMAP_ALLOC (NULL);
|
1062 |
|
|
basic_block bb;
|
1063 |
|
|
edge e;
|
1064 |
|
|
edge_iterator ei;
|
1065 |
|
|
|
1066 |
|
|
for (i = 0; i < VEC_length (edge, threaded_edges); i += 3)
|
1067 |
|
|
{
|
1068 |
|
|
edge e = VEC_index (edge, threaded_edges, i);
|
1069 |
|
|
edge *x = (edge *) XNEWVEC (edge, 2);
|
1070 |
|
|
|
1071 |
|
|
e->aux = x;
|
1072 |
|
|
THREAD_TARGET (e) = VEC_index (edge, threaded_edges, i + 1);
|
1073 |
|
|
THREAD_TARGET2 (e) = VEC_index (edge, threaded_edges, i + 2);
|
1074 |
|
|
bitmap_set_bit (tmp, e->dest->index);
|
1075 |
|
|
}
|
1076 |
|
|
|
1077 |
|
|
/* If optimizing for size, only thread through block if we don't have
|
1078 |
|
|
to duplicate it or it's an otherwise empty redirection block. */
|
1079 |
|
|
if (optimize_function_for_size_p (cfun))
|
1080 |
|
|
{
|
1081 |
|
|
EXECUTE_IF_SET_IN_BITMAP (tmp, 0, i, bi)
|
1082 |
|
|
{
|
1083 |
|
|
bb = BASIC_BLOCK (i);
|
1084 |
|
|
if (EDGE_COUNT (bb->preds) > 1
|
1085 |
|
|
&& !redirection_block_p (bb))
|
1086 |
|
|
{
|
1087 |
|
|
FOR_EACH_EDGE (e, ei, bb->preds)
|
1088 |
|
|
{
|
1089 |
|
|
free (e->aux);
|
1090 |
|
|
e->aux = NULL;
|
1091 |
|
|
}
|
1092 |
|
|
}
|
1093 |
|
|
else
|
1094 |
|
|
bitmap_set_bit (threaded_blocks, i);
|
1095 |
|
|
}
|
1096 |
|
|
}
|
1097 |
|
|
else
|
1098 |
|
|
bitmap_copy (threaded_blocks, tmp);
|
1099 |
|
|
|
1100 |
|
|
BITMAP_FREE(tmp);
|
1101 |
|
|
}
|
1102 |
|
|
|
1103 |
|
|
|
1104 |
|
|
/* Walk through all blocks and thread incoming edges to the appropriate
|
1105 |
|
|
outgoing edge for each edge pair recorded in THREADED_EDGES.
|
1106 |
|
|
|
1107 |
|
|
It is the caller's responsibility to fix the dominance information
|
1108 |
|
|
and rewrite duplicated SSA_NAMEs back into SSA form.
|
1109 |
|
|
|
1110 |
|
|
If MAY_PEEL_LOOP_HEADERS is false, we avoid threading edges through
|
1111 |
|
|
loop headers if it does not simplify the loop.
|
1112 |
|
|
|
1113 |
|
|
Returns true if one or more edges were threaded, false otherwise. */
|
1114 |
|
|
|
1115 |
|
|
bool
|
1116 |
|
|
thread_through_all_blocks (bool may_peel_loop_headers)
|
1117 |
|
|
{
|
1118 |
|
|
bool retval = false;
|
1119 |
|
|
unsigned int i;
|
1120 |
|
|
bitmap_iterator bi;
|
1121 |
|
|
bitmap threaded_blocks;
|
1122 |
|
|
struct loop *loop;
|
1123 |
|
|
loop_iterator li;
|
1124 |
|
|
|
1125 |
|
|
/* We must know about loops in order to preserve them. */
|
1126 |
|
|
gcc_assert (current_loops != NULL);
|
1127 |
|
|
|
1128 |
|
|
if (threaded_edges == NULL)
|
1129 |
|
|
return false;
|
1130 |
|
|
|
1131 |
|
|
threaded_blocks = BITMAP_ALLOC (NULL);
|
1132 |
|
|
memset (&thread_stats, 0, sizeof (thread_stats));
|
1133 |
|
|
|
1134 |
|
|
mark_threaded_blocks (threaded_blocks);
|
1135 |
|
|
|
1136 |
|
|
initialize_original_copy_tables ();
|
1137 |
|
|
|
1138 |
|
|
/* First perform the threading requests that do not affect
|
1139 |
|
|
loop structure. */
|
1140 |
|
|
EXECUTE_IF_SET_IN_BITMAP (threaded_blocks, 0, i, bi)
|
1141 |
|
|
{
|
1142 |
|
|
basic_block bb = BASIC_BLOCK (i);
|
1143 |
|
|
|
1144 |
|
|
if (EDGE_COUNT (bb->preds) > 0)
|
1145 |
|
|
retval |= thread_block (bb, true);
|
1146 |
|
|
}
|
1147 |
|
|
|
1148 |
|
|
/* Then perform the threading through loop headers. We start with the
|
1149 |
|
|
innermost loop, so that the changes in cfg we perform won't affect
|
1150 |
|
|
further threading. */
|
1151 |
|
|
FOR_EACH_LOOP (li, loop, LI_FROM_INNERMOST)
|
1152 |
|
|
{
|
1153 |
|
|
if (!loop->header
|
1154 |
|
|
|| !bitmap_bit_p (threaded_blocks, loop->header->index))
|
1155 |
|
|
continue;
|
1156 |
|
|
|
1157 |
|
|
retval |= thread_through_loop_header (loop, may_peel_loop_headers);
|
1158 |
|
|
}
|
1159 |
|
|
|
1160 |
|
|
statistics_counter_event (cfun, "Jumps threaded",
|
1161 |
|
|
thread_stats.num_threaded_edges);
|
1162 |
|
|
|
1163 |
|
|
free_original_copy_tables ();
|
1164 |
|
|
|
1165 |
|
|
BITMAP_FREE (threaded_blocks);
|
1166 |
|
|
threaded_blocks = NULL;
|
1167 |
|
|
VEC_free (edge, heap, threaded_edges);
|
1168 |
|
|
threaded_edges = NULL;
|
1169 |
|
|
|
1170 |
|
|
if (retval)
|
1171 |
|
|
loops_state_set (LOOPS_NEED_FIXUP);
|
1172 |
|
|
|
1173 |
|
|
return retval;
|
1174 |
|
|
}
|
1175 |
|
|
|
1176 |
|
|
/* Register a jump threading opportunity. We queue up all the jump
|
1177 |
|
|
threading opportunities discovered by a pass and update the CFG
|
1178 |
|
|
and SSA form all at once.
|
1179 |
|
|
|
1180 |
|
|
E is the edge we can thread, E2 is the new target edge, i.e., we
|
1181 |
|
|
are effectively recording that E->dest can be changed to E2->dest
|
1182 |
|
|
after fixing the SSA graph. */
|
1183 |
|
|
|
1184 |
|
|
void
|
1185 |
|
|
register_jump_thread (edge e, edge e2, edge e3)
|
1186 |
|
|
{
|
1187 |
|
|
/* This can occur if we're jumping to a constant address or
|
1188 |
|
|
or something similar. Just get out now. */
|
1189 |
|
|
if (e2 == NULL)
|
1190 |
|
|
return;
|
1191 |
|
|
|
1192 |
|
|
if (threaded_edges == NULL)
|
1193 |
|
|
threaded_edges = VEC_alloc (edge, heap, 15);
|
1194 |
|
|
|
1195 |
|
|
if (dump_file && (dump_flags & TDF_DETAILS)
|
1196 |
|
|
&& e->dest != e2->src)
|
1197 |
|
|
fprintf (dump_file,
|
1198 |
|
|
" Registering jump thread around one or more intermediate blocks\n");
|
1199 |
|
|
|
1200 |
|
|
VEC_safe_push (edge, heap, threaded_edges, e);
|
1201 |
|
|
VEC_safe_push (edge, heap, threaded_edges, e2);
|
1202 |
|
|
VEC_safe_push (edge, heap, threaded_edges, e3);
|
1203 |
|
|
}
|