| /* Thread edges through blocks and update the control flow and SSA graphs. |
| Copyright (C) 2004-2021 Free Software Foundation, Inc. |
| |
| This file is part of GCC. |
| |
| GCC is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 3, or (at your option) |
| any later version. |
| |
| GCC is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GCC; see the file COPYING3. If not see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include "config.h" |
| #include "system.h" |
| #include "coretypes.h" |
| #include "backend.h" |
| #include "tree.h" |
| #include "gimple.h" |
| #include "cfghooks.h" |
| #include "tree-pass.h" |
| #include "ssa.h" |
| #include "fold-const.h" |
| #include "cfganal.h" |
| #include "gimple-iterator.h" |
| #include "tree-ssa.h" |
| #include "tree-ssa-threadupdate.h" |
| #include "cfgloop.h" |
| #include "dbgcnt.h" |
| #include "tree-cfg.h" |
| #include "tree-vectorizer.h" |
| |
| /* Given a block B, update the CFG and SSA graph to reflect redirecting |
| one or more in-edges to B to instead reach the destination of an |
| out-edge from B while preserving any side effects in B. |
| |
| i.e., given A->B and B->C, change A->B to be A->C yet still preserve the |
| side effects of executing B. |
| |
| 1. Make a copy of B (including its outgoing edges and statements). Call |
| the copy B'. Note B' has no incoming edges or PHIs at this time. |
| |
| 2. Remove the control statement at the end of B' and all outgoing edges |
| except B'->C. |
| |
| 3. Add a new argument to each PHI in C with the same value as the existing |
| argument associated with edge B->C. Associate the new PHI arguments |
| with the edge B'->C. |
| |
| 4. For each PHI in B, find or create a PHI in B' with an identical |
| PHI_RESULT. Add an argument to the PHI in B' which has the same |
| value as the PHI in B associated with the edge A->B. Associate |
| the new argument in the PHI in B' with the edge A->B. |
| |
| 5. Change the edge A->B to A->B'. |
| |
| 5a. This automatically deletes any PHI arguments associated with the |
| edge A->B in B. |
| |
| 5b. This automatically associates each new argument added in step 4 |
| with the edge A->B'. |
| |
| 6. Repeat for other incoming edges into B. |
| |
| 7. Put the duplicated resources in B and all the B' blocks into SSA form. |
| |
| Note that block duplication can be minimized by first collecting the |
| set of unique destination blocks that the incoming edges should |
| be threaded to. |
| |
| We reduce the number of edges and statements we create by not copying all |
| the outgoing edges and the control statement in step #1. We instead create |
| a template block without the outgoing edges and duplicate the template. |
| |
| Another case this code handles is threading through a "joiner" block. In |
| this case, we do not know the destination of the joiner block, but one |
| of the outgoing edges from the joiner block leads to a threadable path. This |
| case largely works as outlined above, except the duplicate of the joiner |
| block still contains a full set of outgoing edges and its control statement. |
| We just redirect one of its outgoing edges to our jump threading path. */ |
| |
| |
| /* Steps #5 and #6 of the above algorithm are best implemented by walking |
| all the incoming edges which thread to the same destination edge at |
| the same time. That avoids lots of table lookups to get information |
| for the destination edge. |
| |
| To realize that implementation we create a list of incoming edges |
| which thread to the same outgoing edge. Thus to implement steps |
| #5 and #6 we traverse our hash table of outgoing edge information. |
| For each entry we walk the list of incoming edges which thread to |
| the current outgoing edge. */ |
| |
| struct el |
| { |
| edge e; |
| struct el *next; |
| }; |
| |
| /* Main data structure recording information regarding B's duplicate |
| blocks. */ |
| |
| /* We need to efficiently record the unique thread destinations of this |
| block and specific information associated with those destinations. We |
| may have many incoming edges threaded to the same outgoing edge. This |
| can be naturally implemented with a hash table. */ |
| |
| struct redirection_data : free_ptr_hash<redirection_data> |
| { |
| /* We support wiring up two block duplicates in a jump threading path. |
| |
| One is a normal block copy where we remove the control statement |
| and wire up its single remaining outgoing edge to the thread path. |
| |
| The other is a joiner block where we leave the control statement |
| in place, but wire one of the outgoing edges to a thread path. |
| |
| In theory we could have multiple block duplicates in a jump |
| threading path, but I haven't tried that. |
| |
| The duplicate blocks appear in this array in the same order in |
| which they appear in the jump thread path. */ |
| basic_block dup_blocks[2]; |
| |
| /* The jump threading path. */ |
| vec<jump_thread_edge *> *path; |
| |
| /* A list of incoming edges which we want to thread to the |
| same path. */ |
| struct el *incoming_edges; |
| |
| /* hash_table support. */ |
| static inline hashval_t hash (const redirection_data *); |
| static inline int equal (const redirection_data *, const redirection_data *); |
| }; |
| |
| /* 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, |
| bool registering) |
| { |
| fprintf (dump_file, |
| " %s%s jump thread: (%d, %d) incoming edge; ", |
| (registering ? "Registering" : "Cancelling"), |
| (path[0]->type == EDGE_FSM_THREAD ? " FSM": ""), |
| 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); |
| if (path[0]->type == EDGE_FSM_THREAD) |
| fprintf (dump_file, " (%d, %d) ", |
| path[i]->e->src->index, path[i]->e->dest->index); |
| } |
| fputc ('\n', dump_file); |
| } |
| |
| /* Simple hashing function. For any given incoming edge E, we're going |
| to be most concerned with the final destination of its jump thread |
| path. So hash on the block index of the final edge in the path. */ |
| |
| inline hashval_t |
| redirection_data::hash (const redirection_data *p) |
| { |
| vec<jump_thread_edge *> *path = p->path; |
| return path->last ()->e->dest->index; |
| } |
| |
| /* Given two hash table entries, return true if they have the same |
| jump threading path. */ |
| inline int |
| redirection_data::equal (const redirection_data *p1, const redirection_data *p2) |
| { |
| vec<jump_thread_edge *> *path1 = p1->path; |
| vec<jump_thread_edge *> *path2 = p2->path; |
| |
| if (path1->length () != path2->length ()) |
| return false; |
| |
| for (unsigned int i = 1; i < path1->length (); i++) |
| { |
| if ((*path1)[i]->type != (*path2)[i]->type |
| || (*path1)[i]->e != (*path2)[i]->e) |
| return false; |
| } |
| |
| return true; |
| } |
| |
| /* Rather than search all the edges in jump thread paths each time |
| DOM is able to simply if control statement, we build a hash table |
| with the deleted edges. We only care about the address of the edge, |
| not its contents. */ |
| struct removed_edges : nofree_ptr_hash<edge_def> |
| { |
| static hashval_t hash (edge e) { return htab_hash_pointer (e); } |
| static bool equal (edge e1, edge e2) { return e1 == e2; } |
| }; |
| |
| static hash_table<removed_edges> *removed_edges; |
| |
| /* Data structure of information to pass to hash table traversal routines. */ |
| struct ssa_local_info_t |
| { |
| /* The current block we are working on. */ |
| basic_block bb; |
| |
| /* We only create a template block for the first duplicated block in a |
| jump threading path as we may need many duplicates of that block. |
| |
| The second duplicate block in a path is specific to that path. Creating |
| and sharing a template for that block is considerably more difficult. */ |
| basic_block template_block; |
| |
| /* If we append debug stmts to the template block after creating it, |
| this iterator won't be the last one in the block, and further |
| copies of the template block shouldn't get debug stmts after |
| it. */ |
| gimple_stmt_iterator template_last_to_copy; |
| |
| /* Blocks duplicated for the thread. */ |
| bitmap duplicate_blocks; |
| |
| /* TRUE if we thread one or more jumps, FALSE otherwise. */ |
| bool jumps_threaded; |
| |
| /* When we have multiple paths through a joiner which reach different |
| final destinations, then we may need to correct for potential |
| profile insanities. */ |
| bool need_profile_correction; |
| }; |
| |
| /* Passes which use the jump threading code register jump threading |
| opportunities as they are discovered. We keep the registered |
| jump threading opportunities in this vector as edge pairs |
| (original_edge, target_edge). */ |
| static vec<vec<jump_thread_edge *> *> paths; |
| |
| /* When we start updating the CFG for threading, data necessary for jump |
| threading is attached to the AUX field for the incoming edge. Use these |
| macros to access the underlying structure attached to the AUX field. */ |
| #define THREAD_PATH(E) ((vec<jump_thread_edge *> *)(E)->aux) |
| |
| /* Jump threading statistics. */ |
| |
| struct thread_stats_d |
| { |
| unsigned long num_threaded_edges; |
| }; |
| |
| struct thread_stats_d thread_stats; |
| |
| |
| /* Remove the last statement in block BB if it is a control statement |
| Also remove all outgoing edges except the edge which reaches DEST_BB. |
| If DEST_BB is NULL, then remove all outgoing edges. */ |
| |
| void |
| remove_ctrl_stmt_and_useless_edges (basic_block bb, basic_block dest_bb) |
| { |
| gimple_stmt_iterator gsi; |
| edge e; |
| edge_iterator ei; |
| |
| gsi = gsi_last_bb (bb); |
| |
| /* If the duplicate ends with a control statement, then remove it. |
| |
| Note that if we are duplicating the template block rather than the |
| original basic block, then the duplicate might not have any real |
| statements in it. */ |
| if (!gsi_end_p (gsi) |
| && gsi_stmt (gsi) |
| && (gimple_code (gsi_stmt (gsi)) == GIMPLE_COND |
| || gimple_code (gsi_stmt (gsi)) == GIMPLE_GOTO |
| || gimple_code (gsi_stmt (gsi)) == GIMPLE_SWITCH)) |
| gsi_remove (&gsi, true); |
| |
| for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); ) |
| { |
| if (e->dest != dest_bb) |
| { |
| free_dom_edge_info (e); |
| remove_edge (e); |
| } |
| else |
| { |
| e->probability = profile_probability::always (); |
| ei_next (&ei); |
| } |
| } |
| |
| /* If the remaining edge is a loop exit, there must have |
| a removed edge that was not a loop exit. |
| |
| In that case BB and possibly other blocks were previously |
| in the loop, but are now outside the loop. Thus, we need |
| to update the loop structures. */ |
| if (single_succ_p (bb) |
| && loop_outer (bb->loop_father) |
| && loop_exit_edge_p (bb->loop_father, single_succ_edge (bb))) |
| loops_state_set (LOOPS_NEED_FIXUP); |
| } |
| |
| /* Create a duplicate of BB. Record the duplicate block in an array |
| indexed by COUNT stored in RD. */ |
| |
| static void |
| create_block_for_threading (basic_block bb, |
| struct redirection_data *rd, |
| unsigned int count, |
| bitmap *duplicate_blocks) |
| { |
| edge_iterator ei; |
| edge e; |
| |
| /* We can use the generic block duplication code and simply remove |
| the stuff we do not need. */ |
| rd->dup_blocks[count] = duplicate_block (bb, NULL, NULL); |
| |
| FOR_EACH_EDGE (e, ei, rd->dup_blocks[count]->succs) |
| { |
| e->aux = NULL; |
| |
| /* If we duplicate a block with an outgoing edge marked as |
| EDGE_IGNORE, we must clear EDGE_IGNORE so that it doesn't |
| leak out of the current pass. |
| |
| It would be better to simplify switch statements and remove |
| the edges before we get here, but the sequencing is nontrivial. */ |
| e->flags &= ~EDGE_IGNORE; |
| } |
| |
| /* Zero out the profile, since the block is unreachable for now. */ |
| rd->dup_blocks[count]->count = profile_count::uninitialized (); |
| if (duplicate_blocks) |
| bitmap_set_bit (*duplicate_blocks, rd->dup_blocks[count]->index); |
| } |
| |
| /* Main data structure to hold information for duplicates of BB. */ |
| |
| static hash_table<redirection_data> *redirection_data; |
| |
| /* Given an outgoing edge E lookup and return its entry in our hash table. |
| |
| If INSERT is true, then we insert the entry into the hash table if |
| it is not already present. INCOMING_EDGE is added to the list of incoming |
| edges associated with E in the hash table. */ |
| |
| static struct redirection_data * |
| lookup_redirection_data (edge e, enum insert_option insert) |
| { |
| struct redirection_data **slot; |
| struct redirection_data *elt; |
| vec<jump_thread_edge *> *path = THREAD_PATH (e); |
| |
| /* Build a hash table element so we can see if E is already |
| in the table. */ |
| elt = XNEW (struct redirection_data); |
| elt->path = path; |
| elt->dup_blocks[0] = NULL; |
| elt->dup_blocks[1] = NULL; |
| elt->incoming_edges = NULL; |
| |
| slot = redirection_data->find_slot (elt, insert); |
| |
| /* This will only happen if INSERT is false and the entry is not |
| in the hash table. */ |
| if (slot == NULL) |
| { |
| free (elt); |
| return NULL; |
| } |
| |
| /* This will only happen if E was not in the hash table and |
| INSERT is true. */ |
| if (*slot == NULL) |
| { |
| *slot = elt; |
| elt->incoming_edges = XNEW (struct el); |
| elt->incoming_edges->e = e; |
| elt->incoming_edges->next = NULL; |
| return elt; |
| } |
| /* E was in the hash table. */ |
| else |
| { |
| /* Free ELT as we do not need it anymore, we will extract the |
| relevant entry from the hash table itself. */ |
| free (elt); |
| |
| /* Get the entry stored in the hash table. */ |
| elt = *slot; |
| |
| /* If insertion was requested, then we need to add INCOMING_EDGE |
| to the list of incoming edges associated with E. */ |
| if (insert) |
| { |
| struct el *el = XNEW (struct el); |
| el->next = elt->incoming_edges; |
| el->e = e; |
| elt->incoming_edges = el; |
| } |
| |
| return elt; |
| } |
| } |
| |
| /* Similar to copy_phi_args, except that the PHI arg exists, it just |
| does not have a value associated with it. */ |
| |
| static void |
| copy_phi_arg_into_existing_phi (edge src_e, edge tgt_e) |
| { |
| int src_idx = src_e->dest_idx; |
| int tgt_idx = tgt_e->dest_idx; |
| |
| /* Iterate over each PHI in e->dest. */ |
| for (gphi_iterator gsi = gsi_start_phis (src_e->dest), |
| gsi2 = gsi_start_phis (tgt_e->dest); |
| !gsi_end_p (gsi); |
| gsi_next (&gsi), gsi_next (&gsi2)) |
| { |
| gphi *src_phi = gsi.phi (); |
| gphi *dest_phi = gsi2.phi (); |
| tree val = gimple_phi_arg_def (src_phi, src_idx); |
| location_t locus = gimple_phi_arg_location (src_phi, src_idx); |
| |
| SET_PHI_ARG_DEF (dest_phi, tgt_idx, val); |
| gimple_phi_arg_set_location (dest_phi, tgt_idx, locus); |
| } |
| } |
| |
| /* Given ssa_name DEF, backtrack jump threading PATH from node IDX |
| to see if it has constant value in a flow sensitive manner. Set |
| LOCUS to location of the constant phi arg and return the value. |
| Return DEF directly if either PATH or idx is ZERO. */ |
| |
| static tree |
| get_value_locus_in_path (tree def, vec<jump_thread_edge *> *path, |
| basic_block bb, int idx, location_t *locus) |
| { |
| tree arg; |
| gphi *def_phi; |
| basic_block def_bb; |
| |
| if (path == NULL || idx == 0) |
| return def; |
| |
| def_phi = dyn_cast <gphi *> (SSA_NAME_DEF_STMT (def)); |
| if (!def_phi) |
| return def; |
| |
| def_bb = gimple_bb (def_phi); |
| /* Don't propagate loop invariants into deeper loops. */ |
| if (!def_bb || bb_loop_depth (def_bb) < bb_loop_depth (bb)) |
| return def; |
| |
| /* Backtrack jump threading path from IDX to see if def has constant |
| value. */ |
| for (int j = idx - 1; j >= 0; j--) |
| { |
| edge e = (*path)[j]->e; |
| if (e->dest == def_bb) |
| { |
| arg = gimple_phi_arg_def (def_phi, e->dest_idx); |
| if (is_gimple_min_invariant (arg)) |
| { |
| *locus = gimple_phi_arg_location (def_phi, e->dest_idx); |
| return arg; |
| } |
| break; |
| } |
| } |
| |
| return def; |
| } |
| |
| /* For each PHI in BB, copy the argument associated with SRC_E to TGT_E. |
| Try to backtrack jump threading PATH from node IDX to see if the arg |
| has constant value, copy constant value instead of argument itself |
| if yes. */ |
| |
| static void |
| copy_phi_args (basic_block bb, edge src_e, edge tgt_e, |
| vec<jump_thread_edge *> *path, int idx) |
| { |
| gphi_iterator gsi; |
| int src_indx = src_e->dest_idx; |
| |
| for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) |
| { |
| gphi *phi = gsi.phi (); |
| tree def = gimple_phi_arg_def (phi, src_indx); |
| location_t locus = gimple_phi_arg_location (phi, src_indx); |
| |
| if (TREE_CODE (def) == SSA_NAME |
| && !virtual_operand_p (gimple_phi_result (phi))) |
| def = get_value_locus_in_path (def, path, bb, idx, &locus); |
| |
| add_phi_arg (phi, def, tgt_e, locus); |
| } |
| } |
| |
| /* We have recently made a copy of ORIG_BB, including its outgoing |
| edges. The copy is NEW_BB. Every PHI node in every direct successor of |
| ORIG_BB has a new argument associated with edge from NEW_BB to the |
| successor. Initialize the PHI argument so that it is equal to the PHI |
| argument associated with the edge from ORIG_BB to the successor. |
| PATH and IDX are used to check if the new PHI argument has constant |
| value in a flow sensitive manner. */ |
| |
| static void |
| update_destination_phis (basic_block orig_bb, basic_block new_bb, |
| vec<jump_thread_edge *> *path, int idx) |
| { |
| edge_iterator ei; |
| edge e; |
| |
| FOR_EACH_EDGE (e, ei, orig_bb->succs) |
| { |
| edge e2 = find_edge (new_bb, e->dest); |
| copy_phi_args (e->dest, e, e2, path, idx); |
| } |
| } |
| |
| /* Given a duplicate block and its single destination (both stored |
| in RD). Create an edge between the duplicate and its single |
| destination. |
| |
| Add an additional argument to any PHI nodes at the single |
| destination. IDX is the start node in jump threading path |
| we start to check to see if the new PHI argument has constant |
| value along the jump threading path. */ |
| |
| static void |
| create_edge_and_update_destination_phis (struct redirection_data *rd, |
| basic_block bb, int idx) |
| { |
| edge e = make_single_succ_edge (bb, rd->path->last ()->e->dest, EDGE_FALLTHRU); |
| |
| rescan_loop_exit (e, true, false); |
| |
| /* We used to copy the thread path here. That was added in 2007 |
| and dutifully updated through the representation changes in 2013. |
| |
| In 2013 we added code to thread from an interior node through |
| the backedge to another interior node. That runs after the code |
| to thread through loop headers from outside the loop. |
| |
| The latter may delete edges in the CFG, including those |
| which appeared in the jump threading path we copied here. Thus |
| we'd end up using a dangling pointer. |
| |
| After reviewing the 2007/2011 code, I can't see how anything |
| depended on copying the AUX field and clearly copying the jump |
| threading path is problematical due to embedded edge pointers. |
| It has been removed. */ |
| e->aux = NULL; |
| |
| /* If there are any PHI nodes at the destination of the outgoing edge |
| from the duplicate block, then we will need to add a new argument |
| to them. The argument should have the same value as the argument |
| associated with the outgoing edge stored in RD. */ |
| copy_phi_args (e->dest, rd->path->last ()->e, e, rd->path, idx); |
| } |
| |
| /* Look through PATH beginning at START and return TRUE if there are |
| any additional blocks that need to be duplicated. Otherwise, |
| return FALSE. */ |
| static bool |
| any_remaining_duplicated_blocks (vec<jump_thread_edge *> *path, |
| unsigned int start) |
| { |
| for (unsigned int i = start + 1; i < path->length (); i++) |
| { |
| if ((*path)[i]->type == EDGE_COPY_SRC_JOINER_BLOCK |
| || (*path)[i]->type == EDGE_COPY_SRC_BLOCK) |
| return true; |
| } |
| return false; |
| } |
| |
| |
| /* Compute the amount of profile count coming into the jump threading |
| path stored in RD that we are duplicating, returned in PATH_IN_COUNT_PTR and |
| PATH_IN_FREQ_PTR, as well as the amount of counts flowing out of the |
| duplicated path, returned in PATH_OUT_COUNT_PTR. LOCAL_INFO is used to |
| identify blocks duplicated for jump threading, which have duplicated |
| edges that need to be ignored in the analysis. Return true if path contains |
| a joiner, false otherwise. |
| |
| In the non-joiner case, this is straightforward - all the counts |
| flowing into the jump threading path should flow through the duplicated |
| block and out of the duplicated path. |
| |
| In the joiner case, it is very tricky. Some of the counts flowing into |
| the original path go offpath at the joiner. The problem is that while |
| we know how much total count goes off-path in the original control flow, |
| we don't know how many of the counts corresponding to just the jump |
| threading path go offpath at the joiner. |
| |
| For example, assume we have the following control flow and identified |
| jump threading paths: |
| |
| A B C |
| \ | / |
| Ea \ |Eb / Ec |
| \ | / |
| v v v |
| J <-- Joiner |
| / \ |
| Eoff/ \Eon |
| / \ |
| v v |
| Soff Son <--- Normal |
| /\ |
| Ed/ \ Ee |
| / \ |
| v v |
| D E |
| |
| Jump threading paths: A -> J -> Son -> D (path 1) |
| C -> J -> Son -> E (path 2) |
| |
| Note that the control flow could be more complicated: |
| - Each jump threading path may have more than one incoming edge. I.e. A and |
| Ea could represent multiple incoming blocks/edges that are included in |
| path 1. |
| - There could be EDGE_NO_COPY_SRC_BLOCK edges after the joiner (either |
| before or after the "normal" copy block). These are not duplicated onto |
| the jump threading path, as they are single-successor. |
| - Any of the blocks along the path may have other incoming edges that |
| are not part of any jump threading path, but add profile counts along |
| the path. |
| |
| In the above example, after all jump threading is complete, we will |
| end up with the following control flow: |
| |
| A B C |
| | | | |
| Ea| |Eb |Ec |
| | | | |
| v v v |
| Ja J Jc |
| / \ / \Eon' / \ |
| Eona/ \ ---/---\-------- \Eonc |
| / \ / / \ \ |
| v v v v v |
| Sona Soff Son Sonc |
| \ /\ / |
| \___________ / \ _____/ |
| \ / \/ |
| vv v |
| D E |
| |
| The main issue to notice here is that when we are processing path 1 |
| (A->J->Son->D) we need to figure out the outgoing edge weights to |
| the duplicated edges Ja->Sona and Ja->Soff, while ensuring that the |
| sum of the incoming weights to D remain Ed. The problem with simply |
| assuming that Ja (and Jc when processing path 2) has the same outgoing |
| probabilities to its successors as the original block J, is that after |
| all paths are processed and other edges/counts removed (e.g. none |
| of Ec will reach D after processing path 2), we may end up with not |
| enough count flowing along duplicated edge Sona->D. |
| |
| Therefore, in the case of a joiner, we keep track of all counts |
| coming in along the current path, as well as from predecessors not |
| on any jump threading path (Eb in the above example). While we |
| first assume that the duplicated Eona for Ja->Sona has the same |
| probability as the original, we later compensate for other jump |
| threading paths that may eliminate edges. We do that by keep track |
| of all counts coming into the original path that are not in a jump |
| thread (Eb in the above example, but as noted earlier, there could |
| be other predecessors incoming to the path at various points, such |
| as at Son). Call this cumulative non-path count coming into the path |
| before D as Enonpath. We then ensure that the count from Sona->D is as at |
| least as big as (Ed - Enonpath), but no bigger than the minimum |
| weight along the jump threading path. The probabilities of both the |
| original and duplicated joiner block J and Ja will be adjusted |
| accordingly after the updates. */ |
| |
| static bool |
| compute_path_counts (struct redirection_data *rd, |
| ssa_local_info_t *local_info, |
| profile_count *path_in_count_ptr, |
| profile_count *path_out_count_ptr) |
| { |
| edge e = rd->incoming_edges->e; |
| vec<jump_thread_edge *> *path = THREAD_PATH (e); |
| edge elast = path->last ()->e; |
| profile_count nonpath_count = profile_count::zero (); |
| bool has_joiner = false; |
| profile_count path_in_count = profile_count::zero (); |
| |
| /* Start by accumulating incoming edge counts to the path's first bb |
| into a couple buckets: |
| path_in_count: total count of incoming edges that flow into the |
| current path. |
| nonpath_count: total count of incoming edges that are not |
| flowing along *any* path. These are the counts |
| that will still flow along the original path after |
| all path duplication is done by potentially multiple |
| calls to this routine. |
| (any other incoming edge counts are for a different jump threading |
| path that will be handled by a later call to this routine.) |
| To make this easier, start by recording all incoming edges that flow into |
| the current path in a bitmap. We could add up the path's incoming edge |
| counts here, but we still need to walk all the first bb's incoming edges |
| below to add up the counts of the other edges not included in this jump |
| threading path. */ |
| struct el *next, *el; |
| auto_bitmap in_edge_srcs; |
| for (el = rd->incoming_edges; el; el = next) |
| { |
| next = el->next; |
| bitmap_set_bit (in_edge_srcs, el->e->src->index); |
| } |
| edge ein; |
| edge_iterator ei; |
| FOR_EACH_EDGE (ein, ei, e->dest->preds) |
| { |
| vec<jump_thread_edge *> *ein_path = THREAD_PATH (ein); |
| /* Simply check the incoming edge src against the set captured above. */ |
| if (ein_path |
| && bitmap_bit_p (in_edge_srcs, (*ein_path)[0]->e->src->index)) |
| { |
| /* It is necessary but not sufficient that the last path edges |
| are identical. There may be different paths that share the |
| same last path edge in the case where the last edge has a nocopy |
| source block. */ |
| gcc_assert (ein_path->last ()->e == elast); |
| path_in_count += ein->count (); |
| } |
| else if (!ein_path) |
| { |
| /* Keep track of the incoming edges that are not on any jump-threading |
| path. These counts will still flow out of original path after all |
| jump threading is complete. */ |
| nonpath_count += ein->count (); |
| } |
| } |
| |
| /* Now compute the fraction of the total count coming into the first |
| path bb that is from the current threading path. */ |
| profile_count total_count = e->dest->count; |
| /* Handle incoming profile insanities. */ |
| if (total_count < path_in_count) |
| path_in_count = total_count; |
| profile_probability onpath_scale = path_in_count.probability_in (total_count); |
| |
| /* Walk the entire path to do some more computation in order to estimate |
| how much of the path_in_count will flow out of the duplicated threading |
| path. In the non-joiner case this is straightforward (it should be |
| the same as path_in_count, although we will handle incoming profile |
| insanities by setting it equal to the minimum count along the path). |
| |
| In the joiner case, we need to estimate how much of the path_in_count |
| will stay on the threading path after the joiner's conditional branch. |
| We don't really know for sure how much of the counts |
| associated with this path go to each successor of the joiner, but we'll |
| estimate based on the fraction of the total count coming into the path |
| bb was from the threading paths (computed above in onpath_scale). |
| Afterwards, we will need to do some fixup to account for other threading |
| paths and possible profile insanities. |
| |
| In order to estimate the joiner case's counts we also need to update |
| nonpath_count with any additional counts coming into the path. Other |
| blocks along the path may have additional predecessors from outside |
| the path. */ |
| profile_count path_out_count = path_in_count; |
| profile_count min_path_count = path_in_count; |
| for (unsigned int i = 1; i < path->length (); i++) |
| { |
| edge epath = (*path)[i]->e; |
| profile_count cur_count = epath->count (); |
| if ((*path)[i]->type == EDGE_COPY_SRC_JOINER_BLOCK) |
| { |
| has_joiner = true; |
| cur_count = cur_count.apply_probability (onpath_scale); |
| } |
| /* In the joiner case we need to update nonpath_count for any edges |
| coming into the path that will contribute to the count flowing |
| into the path successor. */ |
| if (has_joiner && epath != elast) |
| { |
| /* Look for other incoming edges after joiner. */ |
| FOR_EACH_EDGE (ein, ei, epath->dest->preds) |
| { |
| if (ein != epath |
| /* Ignore in edges from blocks we have duplicated for a |
| threading path, which have duplicated edge counts until |
| they are redirected by an invocation of this routine. */ |
| && !bitmap_bit_p (local_info->duplicate_blocks, |
| ein->src->index)) |
| nonpath_count += ein->count (); |
| } |
| } |
| if (cur_count < path_out_count) |
| path_out_count = cur_count; |
| if (epath->count () < min_path_count) |
| min_path_count = epath->count (); |
| } |
| |
| /* We computed path_out_count above assuming that this path targeted |
| the joiner's on-path successor with the same likelihood as it |
| reached the joiner. However, other thread paths through the joiner |
| may take a different path through the normal copy source block |
| (i.e. they have a different elast), meaning that they do not |
| contribute any counts to this path's elast. As a result, it may |
| turn out that this path must have more count flowing to the on-path |
| successor of the joiner. Essentially, all of this path's elast |
| count must be contributed by this path and any nonpath counts |
| (since any path through the joiner with a different elast will not |
| include a copy of this elast in its duplicated path). |
| So ensure that this path's path_out_count is at least the |
| difference between elast->count () and nonpath_count. Otherwise the edge |
| counts after threading will not be sane. */ |
| if (local_info->need_profile_correction |
| && has_joiner && path_out_count < elast->count () - nonpath_count) |
| { |
| path_out_count = elast->count () - nonpath_count; |
| /* But neither can we go above the minimum count along the path |
| we are duplicating. This can be an issue due to profile |
| insanities coming in to this pass. */ |
| if (path_out_count > min_path_count) |
| path_out_count = min_path_count; |
| } |
| |
| *path_in_count_ptr = path_in_count; |
| *path_out_count_ptr = path_out_count; |
| return has_joiner; |
| } |
| |
| |
| /* Update the counts and frequencies for both an original path |
| edge EPATH and its duplicate EDUP. The duplicate source block |
| will get a count of PATH_IN_COUNT and PATH_IN_FREQ, |
| and the duplicate edge EDUP will have a count of PATH_OUT_COUNT. */ |
| static void |
| update_profile (edge epath, edge edup, profile_count path_in_count, |
| profile_count path_out_count) |
| { |
| |
| /* First update the duplicated block's count. */ |
| if (edup) |
| { |
| basic_block dup_block = edup->src; |
| |
| /* Edup's count is reduced by path_out_count. We need to redistribute |
| probabilities to the remaining edges. */ |
| |
| edge esucc; |
| edge_iterator ei; |
| profile_probability edup_prob |
| = path_out_count.probability_in (path_in_count); |
| |
| /* Either scale up or down the remaining edges. |
| probabilities are always in range <0,1> and thus we can't do |
| both by same loop. */ |
| if (edup->probability > edup_prob) |
| { |
| profile_probability rev_scale |
| = (profile_probability::always () - edup->probability) |
| / (profile_probability::always () - edup_prob); |
| FOR_EACH_EDGE (esucc, ei, dup_block->succs) |
| if (esucc != edup) |
| esucc->probability /= rev_scale; |
| } |
| else if (edup->probability < edup_prob) |
| { |
| profile_probability scale |
| = (profile_probability::always () - edup_prob) |
| / (profile_probability::always () - edup->probability); |
| FOR_EACH_EDGE (esucc, ei, dup_block->succs) |
| if (esucc != edup) |
| esucc->probability *= scale; |
| } |
| if (edup_prob.initialized_p ()) |
| edup->probability = edup_prob; |
| |
| gcc_assert (!dup_block->count.initialized_p ()); |
| dup_block->count = path_in_count; |
| } |
| |
| if (path_in_count == profile_count::zero ()) |
| return; |
| |
| profile_count final_count = epath->count () - path_out_count; |
| |
| /* Now update the original block's count in the |
| opposite manner - remove the counts/freq that will flow |
| into the duplicated block. Handle underflow due to precision/ |
| rounding issues. */ |
| epath->src->count -= path_in_count; |
| |
| /* Next update this path edge's original and duplicated counts. We know |
| that the duplicated path will have path_out_count flowing |
| out of it (in the joiner case this is the count along the duplicated path |
| out of the duplicated joiner). This count can then be removed from the |
| original path edge. */ |
| |
| edge esucc; |
| edge_iterator ei; |
| profile_probability epath_prob = final_count.probability_in (epath->src->count); |
| |
| if (epath->probability > epath_prob) |
| { |
| profile_probability rev_scale |
| = (profile_probability::always () - epath->probability) |
| / (profile_probability::always () - epath_prob); |
| FOR_EACH_EDGE (esucc, ei, epath->src->succs) |
| if (esucc != epath) |
| esucc->probability /= rev_scale; |
| } |
| else if (epath->probability < epath_prob) |
| { |
| profile_probability scale |
| = (profile_probability::always () - epath_prob) |
| / (profile_probability::always () - epath->probability); |
| FOR_EACH_EDGE (esucc, ei, epath->src->succs) |
| if (esucc != epath) |
| esucc->probability *= scale; |
| } |
| if (epath_prob.initialized_p ()) |
| epath->probability = epath_prob; |
| } |
| |
| /* Wire up the outgoing edges from the duplicate blocks and |
| update any PHIs as needed. Also update the profile counts |
| on the original and duplicate blocks and edges. */ |
| void |
| ssa_fix_duplicate_block_edges (struct redirection_data *rd, |
| ssa_local_info_t *local_info) |
| { |
| bool multi_incomings = (rd->incoming_edges->next != NULL); |
| edge e = rd->incoming_edges->e; |
| vec<jump_thread_edge *> *path = THREAD_PATH (e); |
| edge elast = path->last ()->e; |
| profile_count path_in_count = profile_count::zero (); |
| profile_count path_out_count = profile_count::zero (); |
| |
| /* First determine how much profile count to move from original |
| path to the duplicate path. This is tricky in the presence of |
| a joiner (see comments for compute_path_counts), where some portion |
| of the path's counts will flow off-path from the joiner. In the |
| non-joiner case the path_in_count and path_out_count should be the |
| same. */ |
| bool has_joiner = compute_path_counts (rd, local_info, |
| &path_in_count, &path_out_count); |
| |
| for (unsigned int count = 0, i = 1; i < path->length (); i++) |
| { |
| edge epath = (*path)[i]->e; |
| |
| /* If we were threading through an joiner block, then we want |
| to keep its control statement and redirect an outgoing edge. |
| Else we want to remove the control statement & edges, then create |
| a new outgoing edge. In both cases we may need to update PHIs. */ |
| if ((*path)[i]->type == EDGE_COPY_SRC_JOINER_BLOCK) |
| { |
| edge victim; |
| edge e2; |
| |
| gcc_assert (has_joiner); |
| |
| /* This updates the PHIs at the destination of the duplicate |
| block. Pass 0 instead of i if we are threading a path which |
| has multiple incoming edges. */ |
| update_destination_phis (local_info->bb, rd->dup_blocks[count], |
| path, multi_incomings ? 0 : i); |
| |
| /* Find the edge from the duplicate block to the block we're |
| threading through. That's the edge we want to redirect. */ |
| victim = find_edge (rd->dup_blocks[count], (*path)[i]->e->dest); |
| |
| /* If there are no remaining blocks on the path to duplicate, |
| then redirect VICTIM to the final destination of the jump |
| threading path. */ |
| if (!any_remaining_duplicated_blocks (path, i)) |
| { |
| e2 = redirect_edge_and_branch (victim, elast->dest); |
| /* If we redirected the edge, then we need to copy PHI arguments |
| at the target. If the edge already existed (e2 != victim |
| case), then the PHIs in the target already have the correct |
| arguments. */ |
| if (e2 == victim) |
| copy_phi_args (e2->dest, elast, e2, |
| path, multi_incomings ? 0 : i); |
| } |
| else |
| { |
| /* Redirect VICTIM to the next duplicated block in the path. */ |
| e2 = redirect_edge_and_branch (victim, rd->dup_blocks[count + 1]); |
| |
| /* We need to update the PHIs in the next duplicated block. We |
| want the new PHI args to have the same value as they had |
| in the source of the next duplicate block. |
| |
| Thus, we need to know which edge we traversed into the |
| source of the duplicate. Furthermore, we may have |
| traversed many edges to reach the source of the duplicate. |
| |
| Walk through the path starting at element I until we |
| hit an edge marked with EDGE_COPY_SRC_BLOCK. We want |
| the edge from the prior element. */ |
| for (unsigned int j = i + 1; j < path->length (); j++) |
| { |
| if ((*path)[j]->type == EDGE_COPY_SRC_BLOCK) |
| { |
| copy_phi_arg_into_existing_phi ((*path)[j - 1]->e, e2); |
| break; |
| } |
| } |
| } |
| |
| /* Update the counts of both the original block |
| and path edge, and the duplicates. The path duplicate's |
| incoming count are the totals for all edges |
| incoming to this jump threading path computed earlier. |
| And we know that the duplicated path will have path_out_count |
| flowing out of it (i.e. along the duplicated path out of the |
| duplicated joiner). */ |
| update_profile (epath, e2, path_in_count, path_out_count); |
| } |
| else if ((*path)[i]->type == EDGE_COPY_SRC_BLOCK) |
| { |
| remove_ctrl_stmt_and_useless_edges (rd->dup_blocks[count], NULL); |
| create_edge_and_update_destination_phis (rd, rd->dup_blocks[count], |
| multi_incomings ? 0 : i); |
| if (count == 1) |
| single_succ_edge (rd->dup_blocks[1])->aux = NULL; |
| |
| /* Update the counts of both the original block |
| and path edge, and the duplicates. Since we are now after |
| any joiner that may have existed on the path, the count |
| flowing along the duplicated threaded path is path_out_count. |
| If we didn't have a joiner, then cur_path_freq was the sum |
| of the total frequencies along all incoming edges to the |
| thread path (path_in_freq). If we had a joiner, it would have |
| been updated at the end of that handling to the edge frequency |
| along the duplicated joiner path edge. */ |
| update_profile (epath, EDGE_SUCC (rd->dup_blocks[count], 0), |
| path_out_count, path_out_count); |
| } |
| else |
| { |
| /* No copy case. In this case we don't have an equivalent block |
| on the duplicated thread path to update, but we do need |
| to remove the portion of the counts/freqs that were moved |
| to the duplicated path from the counts/freqs flowing through |
| this block on the original path. Since all the no-copy edges |
| are after any joiner, the removed count is the same as |
| path_out_count. |
| |
| If we didn't have a joiner, then cur_path_freq was the sum |
| of the total frequencies along all incoming edges to the |
| thread path (path_in_freq). If we had a joiner, it would have |
| been updated at the end of that handling to the edge frequency |
| along the duplicated joiner path edge. */ |
| update_profile (epath, NULL, path_out_count, path_out_count); |
| } |
| |
| /* Increment the index into the duplicated path when we processed |
| a duplicated block. */ |
| if ((*path)[i]->type == EDGE_COPY_SRC_JOINER_BLOCK |
| || (*path)[i]->type == EDGE_COPY_SRC_BLOCK) |
| { |
| count++; |
| } |
| } |
| } |
| |
| /* Hash table traversal callback routine to create duplicate blocks. */ |
| |
| int |
| ssa_create_duplicates (struct redirection_data **slot, |
| ssa_local_info_t *local_info) |
| { |
| struct redirection_data *rd = *slot; |
| |
| /* The second duplicated block in a jump threading path is specific |
| to the path. So it gets stored in RD rather than in LOCAL_DATA. |
| |
| Each time we're called, we have to look through the path and see |
| if a second block needs to be duplicated. |
| |
| Note the search starts with the third edge on the path. The first |
| edge is the incoming edge, the second edge always has its source |
| duplicated. Thus we start our search with the third edge. */ |
| vec<jump_thread_edge *> *path = rd->path; |
| for (unsigned int i = 2; i < path->length (); i++) |
| { |
| if ((*path)[i]->type == EDGE_COPY_SRC_BLOCK |
| || (*path)[i]->type == EDGE_COPY_SRC_JOINER_BLOCK) |
| { |
| create_block_for_threading ((*path)[i]->e->src, rd, 1, |
| &local_info->duplicate_blocks); |
| break; |
| } |
| } |
| |
| /* Create a template block if we have not done so already. Otherwise |
| use the template to create a new block. */ |
| if (local_info->template_block == NULL) |
| { |
| create_block_for_threading ((*path)[1]->e->src, rd, 0, |
| &local_info->duplicate_blocks); |
| local_info->template_block = rd->dup_blocks[0]; |
| local_info->template_last_to_copy |
| = gsi_last_bb (local_info->template_block); |
| |
| /* We do not create any outgoing edges for the template. We will |
| take care of that in a later traversal. That way we do not |
| create edges that are going to just be deleted. */ |
| } |
| else |
| { |
| gimple_seq seq = NULL; |
| if (gsi_stmt (local_info->template_last_to_copy) |
| != gsi_stmt (gsi_last_bb (local_info->template_block))) |
| { |
| if (gsi_end_p (local_info->template_last_to_copy)) |
| { |
| seq = bb_seq (local_info->template_block); |
| set_bb_seq (local_info->template_block, NULL); |
| } |
| else |
| seq = gsi_split_seq_after (local_info->template_last_to_copy); |
| } |
| create_block_for_threading (local_info->template_block, rd, 0, |
| &local_info->duplicate_blocks); |
| if (seq) |
| { |
| if (gsi_end_p (local_info->template_last_to_copy)) |
| set_bb_seq (local_info->template_block, seq); |
| else |
| gsi_insert_seq_after (&local_info->template_last_to_copy, |
| seq, GSI_SAME_STMT); |
| } |
| |
| /* Go ahead and wire up outgoing edges and update PHIs for the duplicate |
| block. */ |
| ssa_fix_duplicate_block_edges (rd, local_info); |
| } |
| |
| if (MAY_HAVE_DEBUG_STMTS) |
| { |
| /* Copy debug stmts from each NO_COPY src block to the block |
| that would have been its predecessor, if we can append to it |
| (we can't add stmts after a block-ending stmt), or prepending |
| to the duplicate of the successor, if there is one. If |
| there's no duplicate successor, we'll mostly drop the blocks |
| on the floor; propagate_threaded_block_debug_into, called |
| elsewhere, will consolidate and preserve the effects of the |
| binds, but none of the markers. */ |
| gimple_stmt_iterator copy_to = gsi_last_bb (rd->dup_blocks[0]); |
| if (!gsi_end_p (copy_to)) |
| { |
| if (stmt_ends_bb_p (gsi_stmt (copy_to))) |
| { |
| if (rd->dup_blocks[1]) |
| copy_to = gsi_after_labels (rd->dup_blocks[1]); |
| else |
| copy_to = gsi_none (); |
| } |
| else |
| gsi_next (©_to); |
| } |
| for (unsigned int i = 2, j = 0; i < path->length (); i++) |
| if ((*path)[i]->type == EDGE_NO_COPY_SRC_BLOCK |
| && gsi_bb (copy_to)) |
| { |
| for (gimple_stmt_iterator gsi = gsi_start_bb ((*path)[i]->e->src); |
| !gsi_end_p (gsi); gsi_next (&gsi)) |
| { |
| if (!is_gimple_debug (gsi_stmt (gsi))) |
| continue; |
| gimple *stmt = gsi_stmt (gsi); |
| gimple *copy = gimple_copy (stmt); |
| gsi_insert_before (©_to, copy, GSI_SAME_STMT); |
| } |
| } |
| else if ((*path)[i]->type == EDGE_COPY_SRC_BLOCK |
| || (*path)[i]->type == EDGE_COPY_SRC_JOINER_BLOCK) |
| { |
| j++; |
| gcc_assert (j < 2); |
| copy_to = gsi_last_bb (rd->dup_blocks[j]); |
| if (!gsi_end_p (copy_to)) |
| { |
| if (stmt_ends_bb_p (gsi_stmt (copy_to))) |
| copy_to = gsi_none (); |
| else |
| gsi_next (©_to); |
| } |
| } |
| } |
| |
| /* Keep walking the hash table. */ |
| return 1; |
| } |
| |
| /* We did not create any outgoing edges for the template block during |
| block creation. This hash table traversal callback creates the |
| outgoing edge for the template block. */ |
| |
| inline int |
| ssa_fixup_template_block (struct redirection_data **slot, |
| ssa_local_info_t *local_info) |
| { |
| struct redirection_data *rd = *slot; |
| |
| /* If this is the template block halt the traversal after updating |
| it appropriately. |
| |
| If we were threading through an joiner block, then we want |
| to keep its control statement and redirect an outgoing edge. |
| Else we want to remove the control statement & edges, then create |
| a new outgoing edge. In both cases we may need to update PHIs. */ |
| if (rd->dup_blocks[0] && rd->dup_blocks[0] == local_info->template_block) |
| { |
| ssa_fix_duplicate_block_edges (rd, local_info); |
| return 0; |
| } |
| |
| return 1; |
| } |
| |
| /* Hash table traversal callback to redirect each incoming edge |
| associated with this hash table element to its new destination. */ |
| |
| int |
| ssa_redirect_edges (struct redirection_data **slot, |
| ssa_local_info_t *local_info) |
| { |
| struct redirection_data *rd = *slot; |
| struct el *next, *el; |
| |
| /* Walk over all the incoming edges associated with this hash table |
| entry. */ |
| for (el = rd->incoming_edges; el; el = next) |
| { |
| 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_blocks[0]) |
| { |
| 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_blocks[0]->index); |
| |
| /* Redirect the incoming edge (possibly to the joiner block) to the |
| appropriate duplicate block. */ |
| e2 = redirect_edge_and_branch (e, rd->dup_blocks[0]); |
| 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)) |
| || gimple_clobber_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; |
| |
| local_info.duplicate_blocks = BITMAP_ALLOC (NULL); |
| local_info.need_profile_correction = false; |
| |
| /* 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 |
| = new hash_table<struct redirection_data> (EDGE_COUNT (bb->succs)); |
| |
| /* Record each unique threaded destination into a hash table for |
| efficient lookups. */ |
| edge last = NULL; |
| 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. */ |
| |
| /* One case occurs when there was loop header buried in a jump |
| threading path that crosses loop boundaries. 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) |
| || flow_loop_nested_p (bb->loop_father, |
| e2->dest->loop_father))) |
| { |
| /* 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; |
| } |
| |
| /* Another case occurs when trying to thread through our |
| own loop header, possibly from inside the loop. We will |
| thread these later. */ |
| unsigned int i; |
| for (i = 1; i < path->length (); i++) |
| { |
| if ((*path)[i]->e->src == bb->loop_father->header |
| && (!loop_exit_edge_p (bb->loop_father, e2) |
| || (*path)[1]->type == EDGE_COPY_SRC_JOINER_BLOCK)) |
| break; |
| } |
| |
| if (i != path->length ()) |
| continue; |
| |
| /* Loop parallelization can be confused by the result of |
| threading through the loop exit test back into the loop. |
| However, theading those jumps seems to help other codes. |
| |
| I have been unable to find anything related to the shape of |
| the CFG, the contents of the affected blocks, etc which would |
| allow a more sensible test than what we're using below which |
| merely avoids the optimization when parallelizing loops. */ |
| if (flag_tree_parallelize_loops > 1) |
| { |
| for (i = 1; i < path->length (); i++) |
| if (bb->loop_father == e2->src->loop_father |
| && loop_exits_from_bb_p (bb->loop_father, |
| (*path)[i]->e->src) |
| && !loop_exit_edge_p (bb->loop_father, e2)) |
| break; |
| |
| if (i != path->length ()) |
| { |
| delete_jump_thread_path (path); |
| e->aux = NULL; |
| continue; |
| } |
| } |
| } |
| |
| /* Insert the outgoing edge into the hash table if it is not |
| already in the hash table. */ |
| lookup_redirection_data (e, INSERT); |
| |
| /* When we have thread paths through a common joiner with different |
| final destinations, then we may need corrections to deal with |
| profile insanities. See the big comment before compute_path_counts. */ |
| if ((*path)[1]->type == EDGE_COPY_SRC_JOINER_BLOCK) |
| { |
| if (!last) |
| last = e2; |
| else if (e2 != last) |
| local_info.need_profile_correction = true; |
| } |
| } |
| |
| /* 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. */ |
| delete redirection_data; |
| redirection_data = NULL; |
| |
| if (noloop_only |
| && bb == bb->loop_father->header) |
| set_loop_copy (bb->loop_father, NULL); |
| |
| BITMAP_FREE (local_info.duplicate_blocks); |
| local_info.duplicate_blocks = 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; |
| } |
| |
| /* 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 |
| determine_bb_domination_status (class 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); |
| } |
| |
| /* 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 (class 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 (!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. */ |
| mark_loop_for_removal (loop); |
| 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); |
| } |
| |
| 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) |
| { |
| gphi_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)) |
| { |
| gphi *phi = gsi.phi (); |
| |
| if (!operand_equal_p (gimple_phi_arg_def (phi, indx1), |
| gimple_phi_arg_def (phi, indx2), 0)) |
| return false; |
| } |
| return true; |
| } |
| |
| /* Return the number of non-debug statements and non-virtual PHIs in a |
| block. */ |
| |
| static unsigned int |
| count_stmts_and_phis_in_block (basic_block bb) |
| { |
| unsigned int num_stmts = 0; |
| |
| gphi_iterator gpi; |
| for (gpi = gsi_start_phis (bb); !gsi_end_p (gpi); gsi_next (&gpi)) |
| if (!virtual_operand_p (PHI_RESULT (gpi.phi ()))) |
| num_stmts++; |
| |
| gimple_stmt_iterator gsi; |
| for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) |
| { |
| gimple *stmt = gsi_stmt (gsi); |
| if (!is_gimple_debug (stmt)) |
| num_stmts++; |
| } |
| |
| return num_stmts; |
| } |
| |
| |
| /* 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; |
| auto_bitmap tmp; |
| basic_block bb; |
| edge e; |
| edge_iterator ei; |
| |
| /* It is possible to have jump threads in which one is a subpath |
| of the other. ie, (A, B), (B, C), (C, D) where B is a joiner |
| block and (B, C), (C, D) where no joiner block exists. |
| |
| When this occurs ignore the jump thread request with the joiner |
| block. It's totally subsumed by the simpler jump thread request. |
| |
| This results in less block copying, simpler CFGs. More importantly, |
| when we duplicate the joiner block, B, in this case we will create |
| a new threading opportunity that we wouldn't be able to optimize |
| until the next jump threading iteration. |
| |
| So first convert the jump thread requests which do not require a |
| joiner block. */ |
| for (i = 0; i < paths.length (); i++) |
| { |
| vec<jump_thread_edge *> *path = paths[i]; |
| |
| if (path->length () > 1 |
| && (*path)[1]->type != EDGE_COPY_SRC_JOINER_BLOCK) |
| { |
| edge e = (*path)[0]->e; |
| e->aux = (void *)path; |
| bitmap_set_bit (tmp, e->dest->index); |
| } |
| } |
| |
| /* Now iterate again, converting cases where we want to thread |
| through a joiner block, but only if no other edge on the path |
| already has a jump thread attached to it. We do this in two passes, |
| to avoid situations where the order in the paths vec can hide overlapping |
| threads (the path is recorded on the incoming edge, so we would miss |
| cases where the second path starts at a downstream edge on the same |
| path). First record all joiner paths, deleting any in the unexpected |
| case where there is already a path for that incoming edge. */ |
| for (i = 0; i < paths.length ();) |
| { |
| vec<jump_thread_edge *> *path = paths[i]; |
| |
| if (path->length () > 1 |
| && (*path)[1]->type == EDGE_COPY_SRC_JOINER_BLOCK) |
| { |
| /* Attach the path to the starting edge if none is yet recorded. */ |
| if ((*path)[0]->e->aux == NULL) |
| { |
| (*path)[0]->e->aux = path; |
| i++; |
| } |
| else |
| { |
| paths.unordered_remove (i); |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| dump_jump_thread_path (dump_file, *path, false); |
| delete_jump_thread_path (path); |
| } |
| } |
| else |
| { |
| i++; |
| } |
| } |
| |
| /* Second, look for paths that have any other jump thread attached to |
| them, and either finish converting them or cancel them. */ |
| for (i = 0; i < paths.length ();) |
| { |
| vec<jump_thread_edge *> *path = paths[i]; |
| edge e = (*path)[0]->e; |
| |
| if (path->length () > 1 |
| && (*path)[1]->type == EDGE_COPY_SRC_JOINER_BLOCK && e->aux == path) |
| { |
| unsigned int j; |
| for (j = 1; j < path->length (); j++) |
| if ((*path)[j]->e->aux != NULL) |
| break; |
| |
| /* If we iterated through the entire path without exiting the loop, |
| then we are good to go, record it. */ |
| if (j == path->length ()) |
| { |
| bitmap_set_bit (tmp, e->dest->index); |
| i++; |
| } |
| else |
| { |
| e->aux = NULL; |
| paths.unordered_remove (i); |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| dump_jump_thread_path (dump_file, *path, false); |
| delete_jump_thread_path (path); |
| } |
| } |
| else |
| { |
| i++; |
| } |
| } |
| |
| /* When optimizing for size, prune all thread paths where statement |
| duplication is necessary. |
| |
| We walk the jump thread path looking for copied blocks. There's |
| two types of copied blocks. |
| |
| EDGE_COPY_SRC_JOINER_BLOCK is always copied and thus we will |
| cancel the jump threading request when optimizing for size. |
| |
| EDGE_COPY_SRC_BLOCK which is copied, but some of its statements |
| will be killed by threading. If threading does not kill all of |
| its statements, then we should cancel the jump threading request |
| when optimizing for size. */ |
| if (optimize_function_for_size_p (cfun)) |
| { |
| EXECUTE_IF_SET_IN_BITMAP (tmp, 0, i, bi) |
| { |
| FOR_EACH_EDGE (e, ei, BASIC_BLOCK_FOR_FN (cfun, i)->preds) |
| if (e->aux) |
| { |
| vec<jump_thread_edge *> *path = THREAD_PATH (e); |
| |
| unsigned int j; |
| for (j = 1; j < path->length (); j++) |
| { |
| bb = (*path)[j]->e->src; |
| if (redirection_block_p (bb)) |
| ; |
| else if ((*path)[j]->type == EDGE_COPY_SRC_JOINER_BLOCK |
| || ((*path)[j]->type == EDGE_COPY_SRC_BLOCK |
| && (count_stmts_and_phis_in_block (bb) |
| != estimate_threading_killed_stmts (bb)))) |
| break; |
| } |
| |
| if (j != path->length ()) |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| dump_jump_thread_path (dump_file, *path, 0); |
| delete_jump_thread_path (path); |
| e->aux = NULL; |
| } |
| else |
| bitmap_set_bit (threaded_blocks, i); |
| } |
| } |
| } |
| else |
| bitmap_copy (threaded_blocks, tmp); |
| |
| /* 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_FOR_FN (cfun, 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; |
| } |
| } |
| } |
| } |
| } |
| |
| /* Look for jump threading paths which cross multiple loop headers. |
| |
| The code to thread through loop headers will change the CFG in ways |
| that invalidate the cached loop iteration information. So we must |
| detect that case and wipe the cached information. */ |
| EXECUTE_IF_SET_IN_BITMAP (tmp, 0, i, bi) |
| { |
| basic_block bb = BASIC_BLOCK_FOR_FN (cfun, i); |
| FOR_EACH_EDGE (e, ei, bb->preds) |
| { |
| if (e->aux) |
| { |
| vec<jump_thread_edge *> *path = THREAD_PATH (e); |
| |
| for (unsigned int i = 0, crossed_headers = 0; |
| i < path->length (); |
| i++) |
| { |
| basic_block dest = (*path)[i]->e->dest; |
| basic_block src = (*path)[i]->e->src; |
| /* If we enter a loop. */ |
| if (flow_loop_nested_p (src->loop_father, dest->loop_father)) |
| ++crossed_headers; |
| /* If we step from a block outside an irreducible region |
| to a block inside an irreducible region, then we have |
| crossed into a loop. */ |
| else if (! (src->flags & BB_IRREDUCIBLE_LOOP) |
| && (dest->flags & BB_IRREDUCIBLE_LOOP)) |
| ++crossed_headers; |
| if (crossed_headers > 1) |
| { |
| vect_free_loop_info_assumptions |
| ((*path)[path->length () - 1]->e->dest->loop_father); |
| break; |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| |
| /* Verify that the REGION is a valid jump thread. A jump thread is a special |
| case of SEME Single Entry Multiple Exits region in which all nodes in the |
| REGION have exactly one incoming edge. The only exception is the first block |
| that may not have been connected to the rest of the cfg yet. */ |
| |
| DEBUG_FUNCTION void |
| verify_jump_thread (basic_block *region, unsigned n_region) |
| { |
| for (unsigned i = 0; i < n_region; i++) |
| gcc_assert (EDGE_COUNT (region[i]->preds) <= 1); |
| } |
| |
| /* Return true when BB is one of the first N items in BBS. */ |
| |
| static inline bool |
| bb_in_bbs (basic_block bb, basic_block *bbs, int n) |
| { |
| for (int i = 0; i < n; i++) |
| if (bb == bbs[i]) |
| return true; |
| |
| return false; |
| } |
| |
| DEBUG_FUNCTION void |
| debug_path (FILE *dump_file, int pathno) |
| { |
| vec<jump_thread_edge *> *p = paths[pathno]; |
| fprintf (dump_file, "path: "); |
| for (unsigned i = 0; i < p->length (); ++i) |
| fprintf (dump_file, "%d -> %d, ", |
| (*p)[i]->e->src->index, (*p)[i]->e->dest->index); |
| fprintf (dump_file, "\n"); |
| } |
| |
| DEBUG_FUNCTION void |
| debug_all_paths () |
| { |
| for (unsigned i = 0; i < paths.length (); ++i) |
| debug_path (stderr, i); |
| } |
| |
| /* Rewire a jump_thread_edge so that the source block is now a |
| threaded source block. |
| |
| PATH_NUM is an index into the global path table PATHS. |
| EDGE_NUM is the jump thread edge number into said path. |
| |
| Returns TRUE if we were able to successfully rewire the edge. */ |
| |
| static bool |
| rewire_first_differing_edge (unsigned path_num, unsigned edge_num) |
| { |
| vec<jump_thread_edge *> *path = paths[path_num]; |
| edge &e = (*path)[edge_num]->e; |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, "rewiring edge candidate: %d -> %d\n", |
| e->src->index, e->dest->index); |
| basic_block src_copy = get_bb_copy (e->src); |
| if (src_copy == NULL) |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, "ignoring candidate: there is no src COPY\n"); |
| return false; |
| } |
| edge new_edge = find_edge (src_copy, e->dest); |
| /* If the previously threaded paths created a flow graph where we |
| can no longer figure out where to go, give up. */ |
| if (new_edge == NULL) |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, "ignoring candidate: we lost our way\n"); |
| return false; |
| } |
| e = new_edge; |
| return true; |
| } |
| |
| /* After an FSM path has been jump threaded, adjust the remaining FSM |
| paths that are subsets of this path, so these paths can be safely |
| threaded within the context of the new threaded path. |
| |
| For example, suppose we have just threaded: |
| |
| 5 -> 6 -> 7 -> 8 -> 12 => 5 -> 6' -> 7' -> 8' -> 12' |
| |
| And we have an upcoming threading candidate: |
| 5 -> 6 -> 7 -> 8 -> 15 -> 20 |
| |
| This function adjusts the upcoming path into: |
| 8' -> 15 -> 20 |
| |
| CURR_PATH_NUM is an index into the global paths table. It |
| specifies the path that was just threaded. */ |
| |
| static void |
| adjust_paths_after_duplication (unsigned curr_path_num) |
| { |
| vec<jump_thread_edge *> *curr_path = paths[curr_path_num]; |
| gcc_assert ((*curr_path)[0]->type == EDGE_FSM_THREAD); |
| |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| { |
| fprintf (dump_file, "just threaded: "); |
| debug_path (dump_file, curr_path_num); |
| } |
| |
| /* Iterate through all the other paths and adjust them. */ |
| for (unsigned cand_path_num = 0; cand_path_num < paths.length (); ) |
| { |
| if (cand_path_num == curr_path_num) |
| { |
| ++cand_path_num; |
| continue; |
| } |
| /* Make sure the candidate to adjust starts with the same path |
| as the recently threaded path and is an FSM thread. */ |
| vec<jump_thread_edge *> *cand_path = paths[cand_path_num]; |
| if ((*cand_path)[0]->type != EDGE_FSM_THREAD |
| || (*cand_path)[0]->e != (*curr_path)[0]->e) |
| { |
| ++cand_path_num; |
| continue; |
| } |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| { |
| fprintf (dump_file, "adjusting candidate: "); |
| debug_path (dump_file, cand_path_num); |
| } |
| |
| /* Chop off from the candidate path any prefix it shares with |
| the recently threaded path. */ |
| unsigned minlength = MIN (curr_path->length (), cand_path->length ()); |
| unsigned j; |
| for (j = 0; j < minlength; ++j) |
| { |
| edge cand_edge = (*cand_path)[j]->e; |
| edge curr_edge = (*curr_path)[j]->e; |
| |
| /* Once the prefix no longer matches, adjust the first |
| non-matching edge to point from an adjusted edge to |
| wherever it was going. */ |
| if (cand_edge != curr_edge) |
| { |
| gcc_assert (cand_edge->src == curr_edge->src); |
| if (!rewire_first_differing_edge (cand_path_num, j)) |
| goto remove_candidate_from_list; |
| break; |
| } |
| } |
| if (j == minlength) |
| { |
| /* If we consumed the max subgraph we could look at, and |
| still didn't find any different edges, it's the |
| last edge after MINLENGTH. */ |
| if (cand_path->length () > minlength) |
| { |
| if (!rewire_first_differing_edge (cand_path_num, j)) |
| goto remove_candidate_from_list; |
| } |
| else if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, "adjusting first edge after MINLENGTH.\n"); |
| } |
| if (j > 0) |
| { |
| /* If we are removing everything, delete the entire candidate. */ |
| if (j == cand_path->length ()) |
| { |
| remove_candidate_from_list: |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, "adjusted candidate: [EMPTY]\n"); |
| delete_jump_thread_path (cand_path); |
| paths.unordered_remove (cand_path_num); |
| continue; |
| } |
| /* Otherwise, just remove the redundant sub-path. */ |
| cand_path->block_remove (0, j); |
| } |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| { |
| fprintf (dump_file, "adjusted candidate: "); |
| debug_path (dump_file, cand_path_num); |
| } |
| ++cand_path_num; |
| } |
| } |
| |
| /* Duplicates a jump-thread path of N_REGION basic blocks. |
| The ENTRY edge is redirected to the duplicate of the region. |
| |
| Remove the last conditional statement in the last basic block in the REGION, |
| and create a single fallthru edge pointing to the same destination as the |
| EXIT edge. |
| |
| CURRENT_PATH_NO is an index into the global paths[] table |
| specifying the jump-thread path. |
| |
| Returns false if it is unable to copy the region, true otherwise. */ |
| |
| static bool |
| duplicate_thread_path (edge entry, edge exit, basic_block *region, |
| unsigned n_region, unsigned current_path_no) |
| { |
| unsigned i; |
| class loop *loop = entry->dest->loop_father; |
| edge exit_copy; |
| edge redirected; |
| profile_count curr_count; |
| |
| if (!can_copy_bbs_p (region, n_region)) |
| return false; |
| |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| { |
| fprintf (dump_file, "\nabout to thread: "); |
| debug_path (dump_file, current_path_no); |
| } |
| |
| /* Some sanity checking. Note that we do not check for all possible |
| missuses of the functions. I.e. if you ask to copy something weird, |
| it will work, but the state of structures probably will not be |
| correct. */ |
| for (i = 0; i < n_region; i++) |
| { |
| /* We do not handle subloops, i.e. all the blocks must belong to the |
| same loop. */ |
| if (region[i]->loop_father != loop) |
| return false; |
| } |
| |
| initialize_original_copy_tables (); |
| |
| set_loop_copy (loop, loop); |
| |
| basic_block *region_copy = XNEWVEC (basic_block, n_region); |
| copy_bbs (region, n_region, region_copy, &exit, 1, &exit_copy, loop, |
| split_edge_bb_loc (entry), false); |
| |
| /* Fix up: copy_bbs redirects all edges pointing to copied blocks. The |
| following code ensures that all the edges exiting the jump-thread path are |
| redirected back to the original code: these edges are exceptions |
| invalidating the property that is propagated by executing all the blocks of |
| the jump-thread path in order. */ |
| |
| curr_count = entry->count (); |
| |
| for (i = 0; i < n_region; i++) |
| { |
| edge e; |
| edge_iterator ei; |
| basic_block bb = region_copy[i]; |
| |
| /* Watch inconsistent profile. */ |
| if (curr_count > region[i]->count) |
| curr_count = region[i]->count; |
| /* Scale current BB. */ |
| if (region[i]->count.nonzero_p () && curr_count.initialized_p ()) |
| { |
| /* In the middle of the path we only scale the frequencies. |
| In last BB we need to update probabilities of outgoing edges |
| because we know which one is taken at the threaded path. */ |
| if (i + 1 != n_region) |
| scale_bbs_frequencies_profile_count (region + i, 1, |
| region[i]->count - curr_count, |
| region[i]->count); |
| else |
| update_bb_profile_for_threading (region[i], |
| curr_count, |
| exit); |
| scale_bbs_frequencies_profile_count (region_copy + i, 1, curr_count, |
| region_copy[i]->count); |
| } |
| |
| if (single_succ_p (bb)) |
| { |
| /* Make sure the successor is the next node in the path. */ |
| gcc_assert (i + 1 == n_region |
| || region_copy[i + 1] == single_succ_edge (bb)->dest); |
| if (i + 1 != n_region) |
| { |
| curr_count = single_succ_edge (bb)->count (); |
| } |
| continue; |
| } |
| |
| /* Special case the last block on the path: make sure that it does not |
| jump back on the copied path, including back to itself. */ |
| if (i + 1 == n_region) |
| { |
| FOR_EACH_EDGE (e, ei, bb->succs) |
| if (bb_in_bbs (e->dest, region_copy, n_region)) |
| { |
| basic_block orig = get_bb_original (e->dest); |
| if (orig) |
| redirect_edge_and_branch_force (e, orig); |
| } |
| continue; |
| } |
| |
| /* Redirect all other edges jumping to non-adjacent blocks back to the |
| original code. */ |
| FOR_EACH_EDGE (e, ei, bb->succs) |
| if (region_copy[i + 1] != e->dest) |
| { |
| basic_block orig = get_bb_original (e->dest); |
| if (orig) |
| redirect_edge_and_branch_force (e, orig); |
| } |
| else |
| { |
| curr_count = e->count (); |
| } |
| } |
| |
| |
| if (flag_checking) |
| verify_jump_thread (region_copy, n_region); |
| |
| /* Remove the last branch in the jump thread path. */ |
| remove_ctrl_stmt_and_useless_edges (region_copy[n_region - 1], exit->dest); |
| |
| /* And fixup the flags on the single remaining edge. */ |
| edge fix_e = find_edge (region_copy[n_region - 1], exit->dest); |
| fix_e->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE | EDGE_ABNORMAL); |
| fix_e->flags |= EDGE_FALLTHRU; |
| |
| edge e = make_edge (region_copy[n_region - 1], exit->dest, EDGE_FALLTHRU); |
| |
| if (e) |
| { |
| rescan_loop_exit (e, true, false); |
| e->probability = profile_probability::always (); |
| } |
| |
| /* Redirect the entry and add the phi node arguments. */ |
| if (entry->dest == loop->header) |
| mark_loop_for_removal (loop); |
| redirected = redirect_edge_and_branch (entry, get_bb_copy (entry->dest)); |
| gcc_assert (redirected != NULL); |
| flush_pending_stmts (entry); |
| |
| /* Add the other PHI node arguments. */ |
| add_phi_args_after_copy (region_copy, n_region, NULL); |
| |
| free (region_copy); |
| |
| adjust_paths_after_duplication (current_path_no); |
| |
| free_original_copy_tables (); |
| return true; |
| } |
| |
| /* Return true when PATH is a valid jump-thread path. */ |
| |
| static bool |
| valid_jump_thread_path (vec<jump_thread_edge *> *path) |
| { |
| unsigned len = path->length (); |
| |
| /* Check that the path is connected. */ |
| for (unsigned int j = 0; j < len - 1; j++) |
| { |
| edge e = (*path)[j]->e; |
| if (e->dest != (*path)[j+1]->e->src) |
| return false; |
| } |
| return true; |
| } |
| |
| /* Remove any queued jump threads that include edge E. |
| |
| We don't actually remove them here, just record the edges into ax |
| hash table. That way we can do the search once per iteration of |
| DOM/VRP rather than for every case where DOM optimizes away a COND_EXPR. */ |
| |
| void |
| remove_jump_threads_including (edge_def *e) |
| { |
| if (!paths.exists ()) |
| return; |
| |
| if (!removed_edges) |
| removed_edges = new hash_table<struct removed_edges> (17); |
| |
| edge *slot = removed_edges->find_slot (e, INSERT); |
| *slot = e; |
| } |
| |
| /* 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; |
| class loop *loop; |
| auto_bitmap threaded_blocks; |
| hash_set<edge> visited_starting_edges; |
| |
| if (!paths.exists ()) |
| { |
| retval = false; |
| goto out; |
| } |
| |
| memset (&thread_stats, 0, sizeof (thread_stats)); |
| |
| /* Remove any paths that referenced removed edges. */ |
| if (removed_edges) |
| for (i = 0; i < paths.length (); ) |
| { |
| unsigned int j; |
| vec<jump_thread_edge *> *path = paths[i]; |
| |
| for (j = 0; j < path->length (); j++) |
| { |
| edge e = (*path)[j]->e; |
| if (removed_edges->find_slot (e, NO_INSERT)) |
| break; |
| } |
| |
| if (j != path->length ()) |
| { |
| delete_jump_thread_path (path); |
| paths.unordered_remove (i); |
| continue; |
| } |
| i++; |
| } |
| |
| /* Jump-thread all FSM threads before other jump-threads. */ |
| for (i = 0; i < paths.length ();) |
| { |
| vec<jump_thread_edge *> *path = paths[i]; |
| edge entry = (*path)[0]->e; |
| |
| /* Only code-generate FSM jump-threads in this loop. */ |
| if ((*path)[0]->type != EDGE_FSM_THREAD) |
| { |
| i++; |
| continue; |
| } |
| |
| /* Do not jump-thread twice from the same starting edge. |
| |
| Previously we only checked that we weren't threading twice |
| from the same BB, but that was too restrictive. Imagine a |
| path that starts from GIMPLE_COND(x_123 == 0,...), where both |
| edges out of this conditional yield paths that can be |
| threaded (for example, both lead to an x_123==0 or x_123!=0 |
| conditional further down the line. */ |
| if (visited_starting_edges.contains (entry) |
| /* We may not want to realize this jump thread path for |
| various reasons. So check it first. */ |
| || !valid_jump_thread_path (path)) |
| { |
| /* Remove invalid FSM jump-thread paths. */ |
| delete_jump_thread_path (path); |
| paths.unordered_remove (i); |
| continue; |
| } |
| |
| unsigned len = path->length (); |
| edge exit = (*path)[len - 1]->e; |
| basic_block *region = XNEWVEC (basic_block, len - 1); |
| |
| for (unsigned int j = 0; j < len - 1; j++) |
| region[j] = (*path)[j]->e->dest; |
| |
| if (duplicate_thread_path (entry, exit, region, len - 1, i)) |
| { |
| /* We do not update dominance info. */ |
| free_dominance_info (CDI_DOMINATORS); |
| visited_starting_edges.add (entry); |
| retval = true; |
| thread_stats.num_threaded_edges++; |
| } |
| |
| delete_jump_thread_path (path); |
| paths.unordered_remove (i); |
| free (region); |
| } |
| |
| /* Remove from PATHS all the jump-threads starting with an edge already |
| jump-threaded. */ |
| for (i = 0; i < paths.length ();) |
| { |
| vec<jump_thread_edge *> *path = paths[i]; |
| edge entry = (*path)[0]->e; |
| |
| /* Do not jump-thread twice from the same block. */ |
| if (visited_starting_edges.contains (entry)) |
| { |
| delete_jump_thread_path (path); |
| paths.unordered_remove (i); |
| } |
| else |
| i++; |
| } |
| |
| mark_threaded_blocks (threaded_blocks); |
| |
| initialize_original_copy_tables (); |
| |
| /* The order in which we process jump threads can be important. |
| |
| Consider if we have two jump threading paths A and B. If the |
| target edge of A is the starting edge of B and we thread path A |
| first, then we create an additional incoming edge into B->dest that |
| we cannot discover as a jump threading path on this iteration. |
| |
| If we instead thread B first, then the edge into B->dest will have |
| already been redirected before we process path A and path A will |
| natually, with no further work, target the redirected path for B. |
| |
| An post-order is sufficient here. Compute the ordering first, then |
| process the blocks. */ |
| if (!bitmap_empty_p (threaded_blocks)) |
| { |
| int *postorder = XNEWVEC (int, n_basic_blocks_for_fn (cfun)); |
| unsigned int postorder_num = post_order_compute (postorder, false, false); |
| for (unsigned int i = 0; i < postorder_num; i++) |
| { |
| unsigned int indx = postorder[i]; |
| if (bitmap_bit_p (threaded_blocks, indx)) |
| { |
| basic_block bb = BASIC_BLOCK_FOR_FN (cfun, indx); |
| retval |= thread_block (bb, true); |
| } |
| } |
| free (postorder); |
| } |
| |
| /* 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 (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); |
| } |
| |
| /* All jump threading paths should have been resolved at this |
| point. Verify that is the case. */ |
| basic_block bb; |
| FOR_EACH_BB_FN (bb, cfun) |
| { |
| edge_iterator ei; |
| edge e; |
| FOR_EACH_EDGE (e, ei, bb->preds) |
| gcc_assert (e->aux == NULL); |
| } |
| |
| statistics_counter_event (cfun, "Jumps threaded", |
| thread_stats.num_threaded_edges); |
| |
| free_original_copy_tables (); |
| |
| paths.release (); |
| |
| if (retval) |
| loops_state_set (LOOPS_NEED_FIXUP); |
| |
| out: |
| delete removed_edges; |
| removed_edges = NULL; |
| return retval; |
| } |
| |
| /* Delete the jump threading path PATH. We have to explicitly 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(); |
| delete path; |
| } |
| |
| /* 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, false); |
| } |
| |
| delete_jump_thread_path (path); |
| return; |
| } |
| |
| /* Only the FSM threader is allowed to thread across |
| backedges in the CFG. */ |
| if (flag_checking |
| && (*path)[0]->type != EDGE_FSM_THREAD) |
| gcc_assert (((*path)[i]->e->flags & EDGE_DFS_BACK) == 0); |
| } |
| |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| dump_jump_thread_path (dump_file, *path, true); |
| |
| if (!paths.exists ()) |
| paths.create (5); |
| |
| paths.safe_push (path); |
| } |
| |
| /* Return how many uses of T there are within BB, as long as there |
| aren't any uses outside BB. If there are any uses outside BB, |
| return -1 if there's at most one use within BB, or -2 if there is |
| more than one use within BB. */ |
| |
| static int |
| uses_in_bb (tree t, basic_block bb) |
| { |
| int uses = 0; |
| bool outside_bb = false; |
| |
| imm_use_iterator iter; |
| use_operand_p use_p; |
| FOR_EACH_IMM_USE_FAST (use_p, iter, t) |
| { |
| if (is_gimple_debug (USE_STMT (use_p))) |
| continue; |
| |
| if (gimple_bb (USE_STMT (use_p)) != bb) |
| outside_bb = true; |
| else |
| uses++; |
| |
| if (outside_bb && uses > 1) |
| return -2; |
| } |
| |
| if (outside_bb) |
| return -1; |
| |
| return uses; |
| } |
| |
| /* Starting from the final control flow stmt in BB, assuming it will |
| be removed, follow uses in to-be-removed stmts back to their defs |
| and count how many defs are to become dead and be removed as |
| well. */ |
| |
| unsigned int |
| estimate_threading_killed_stmts (basic_block bb) |
| { |
| int killed_stmts = 0; |
| hash_map<tree, int> ssa_remaining_uses; |
| auto_vec<gimple *, 4> dead_worklist; |
| |
| /* If the block has only two predecessors, threading will turn phi |
| dsts into either src, so count them as dead stmts. */ |
| bool drop_all_phis = EDGE_COUNT (bb->preds) == 2; |
| |
| if (drop_all_phis) |
| for (gphi_iterator gsi = gsi_start_phis (bb); |
| !gsi_end_p (gsi); gsi_next (&gsi)) |
| { |
| gphi *phi = gsi.phi (); |
| tree dst = gimple_phi_result (phi); |
| |
| /* We don't count virtual PHIs as stmts in |
| record_temporary_equivalences_from_phis. */ |
| if (virtual_operand_p (dst)) |
| continue; |
| |
| killed_stmts++; |
| } |
| |
| if (gsi_end_p (gsi_last_bb (bb))) |
| return killed_stmts; |
| |
| gimple *stmt = gsi_stmt (gsi_last_bb (bb)); |
| if (gimple_code (stmt) != GIMPLE_COND |
| && gimple_code (stmt) != GIMPLE_GOTO |
| && gimple_code (stmt) != GIMPLE_SWITCH) |
| return killed_stmts; |
| |
| /* The control statement is always dead. */ |
| killed_stmts++; |
| dead_worklist.quick_push (stmt); |
| while (!dead_worklist.is_empty ()) |
| { |
| stmt = dead_worklist.pop (); |
| |
| ssa_op_iter iter; |
| use_operand_p use_p; |
| FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE) |
| { |
| tree t = USE_FROM_PTR (use_p); |
| gimple *def = SSA_NAME_DEF_STMT (t); |
| |
| if (gimple_bb (def) == bb |
| && (gimple_code (def) != GIMPLE_PHI |
| || !drop_all_phis) |
| && !gimple_has_side_effects (def)) |
| { |
| int *usesp = ssa_remaining_uses.get (t); |
| int uses; |
| |
| if (usesp) |
| uses = *usesp; |
| else |
| uses = uses_in_bb (t, bb); |
| |
| gcc_assert (uses); |
| |
| /* Don't bother recording the expected use count if we |
| won't find any further uses within BB. */ |
| if (!usesp && (uses < -1 || uses > 1)) |
| { |
| usesp = &ssa_remaining_uses.get_or_insert (t); |
| *usesp = uses; |
| } |
| |
| if (uses < 0) |
| continue; |
| |
| --uses; |
| if (usesp) |
| *usesp = uses; |
| |
| if (!uses) |
| { |
| killed_stmts++; |
| if (usesp) |
| ssa_remaining_uses.remove (t); |
| if (gimple_code (def) != GIMPLE_PHI) |
| dead_worklist.safe_push (def); |
| } |
| } |
| } |
| } |
| |
| if (dump_file) |
| fprintf (dump_file, "threading bb %i kills %i stmts\n", |
| bb->index, killed_stmts); |
| |
| return killed_stmts; |
| } |