1 /* High-level loop manipulation functions.
2    Copyright (C) 2004-2022 Free Software Foundation, Inc.
3 
4 This file is part of GCC.
5 
6 GCC is free software; you can redistribute it and/or modify it
7 under the terms of the GNU General Public License as published by the
8 Free Software Foundation; either version 3, or (at your option) any
9 later version.
10 
11 GCC is distributed in the hope that it will be useful, but WITHOUT
12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 for more details.
15 
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3.  If not see
18 <http://www.gnu.org/licenses/>.  */
19 
20 #include "config.h"
21 #include "system.h"
22 #include "coretypes.h"
23 #include "backend.h"
24 #include "tree.h"
25 #include "gimple.h"
26 #include "cfghooks.h"
27 #include "tree-pass.h"	/* ??? for TODO_update_ssa but this isn't a pass.  */
28 #include "ssa.h"
29 #include "gimple-pretty-print.h"
30 #include "fold-const.h"
31 #include "cfganal.h"
32 #include "gimplify.h"
33 #include "gimple-iterator.h"
34 #include "gimplify-me.h"
35 #include "tree-cfg.h"
36 #include "tree-ssa-loop-ivopts.h"
37 #include "tree-ssa-loop-manip.h"
38 #include "tree-ssa-loop-niter.h"
39 #include "tree-ssa-loop.h"
40 #include "tree-into-ssa.h"
41 #include "tree-ssa.h"
42 #include "cfgloop.h"
43 #include "tree-scalar-evolution.h"
44 #include "tree-inline.h"
45 
46 /* All bitmaps for rewriting into loop-closed SSA go on this obstack,
47    so that we can free them all at once.  */
48 static bitmap_obstack loop_renamer_obstack;
49 
50 /* Creates an induction variable with value BASE + STEP * iteration in LOOP.
51    It is expected that neither BASE nor STEP are shared with other expressions
52    (unless the sharing rules allow this).  Use VAR as a base var_decl for it
53    (if NULL, a new temporary will be created).  The increment will occur at
54    INCR_POS (after it if AFTER is true, before it otherwise).  INCR_POS and
55    AFTER can be computed using standard_iv_increment_position.  The ssa versions
56    of the variable before and after increment will be stored in VAR_BEFORE and
57    VAR_AFTER (unless they are NULL).  */
58 
59 void
create_iv(tree base,tree step,tree var,class loop * loop,gimple_stmt_iterator * incr_pos,bool after,tree * var_before,tree * var_after)60 create_iv (tree base, tree step, tree var, class loop *loop,
61 	   gimple_stmt_iterator *incr_pos, bool after,
62 	   tree *var_before, tree *var_after)
63 {
64   gassign *stmt;
65   gphi *phi;
66   tree initial, step1;
67   gimple_seq stmts;
68   tree vb, va;
69   enum tree_code incr_op = PLUS_EXPR;
70   edge pe = loop_preheader_edge (loop);
71 
72   if (var != NULL_TREE)
73     {
74       vb = make_ssa_name (var);
75       va = make_ssa_name (var);
76     }
77   else
78     {
79       vb = make_temp_ssa_name (TREE_TYPE (base), NULL, "ivtmp");
80       va = make_temp_ssa_name (TREE_TYPE (base), NULL, "ivtmp");
81     }
82   if (var_before)
83     *var_before = vb;
84   if (var_after)
85     *var_after = va;
86 
87   /* For easier readability of the created code, produce MINUS_EXPRs
88      when suitable.  */
89   if (TREE_CODE (step) == INTEGER_CST)
90     {
91       if (TYPE_UNSIGNED (TREE_TYPE (step)))
92 	{
93 	  step1 = fold_build1 (NEGATE_EXPR, TREE_TYPE (step), step);
94 	  if (tree_int_cst_lt (step1, step))
95 	    {
96 	      incr_op = MINUS_EXPR;
97 	      step = step1;
98 	    }
99 	}
100       else
101 	{
102 	  bool ovf;
103 
104 	  if (!tree_expr_nonnegative_warnv_p (step, &ovf)
105 	      && may_negate_without_overflow_p (step))
106 	    {
107 	      incr_op = MINUS_EXPR;
108 	      step = fold_build1 (NEGATE_EXPR, TREE_TYPE (step), step);
109 	    }
110 	}
111     }
112   if (POINTER_TYPE_P (TREE_TYPE (base)))
113     {
114       if (TREE_CODE (base) == ADDR_EXPR)
115 	mark_addressable (TREE_OPERAND (base, 0));
116       step = convert_to_ptrofftype (step);
117       if (incr_op == MINUS_EXPR)
118 	step = fold_build1 (NEGATE_EXPR, TREE_TYPE (step), step);
119       incr_op = POINTER_PLUS_EXPR;
120     }
121   /* Gimplify the step if necessary.  We put the computations in front of the
122      loop (i.e. the step should be loop invariant).  */
123   step = force_gimple_operand (step, &stmts, true, NULL_TREE);
124   if (stmts)
125     gsi_insert_seq_on_edge_immediate (pe, stmts);
126 
127   stmt = gimple_build_assign (va, incr_op, vb, step);
128   /* Prevent the increment from inheriting a bogus location if it is not put
129      immediately after a statement whose location is known.  */
130   if (after)
131     {
132       if (gsi_end_p (*incr_pos)
133 	  || (is_gimple_debug (gsi_stmt (*incr_pos))
134 	      && gsi_bb (*incr_pos)
135 	      && gsi_end_p (gsi_last_nondebug_bb (gsi_bb (*incr_pos)))))
136 	{
137 	  edge e = single_succ_edge (gsi_bb (*incr_pos));
138 	  gimple_set_location (stmt, e->goto_locus);
139 	}
140       gsi_insert_after (incr_pos, stmt, GSI_NEW_STMT);
141     }
142   else
143     {
144       gimple_stmt_iterator gsi = *incr_pos;
145       if (!gsi_end_p (gsi) && is_gimple_debug (gsi_stmt (gsi)))
146 	gsi_next_nondebug (&gsi);
147       if (!gsi_end_p (gsi))
148 	gimple_set_location (stmt, gimple_location (gsi_stmt (gsi)));
149       gsi_insert_before (incr_pos, stmt, GSI_NEW_STMT);
150     }
151 
152   initial = force_gimple_operand (base, &stmts, true, var);
153   if (stmts)
154     gsi_insert_seq_on_edge_immediate (pe, stmts);
155 
156   phi = create_phi_node (vb, loop->header);
157   add_phi_arg (phi, initial, loop_preheader_edge (loop), UNKNOWN_LOCATION);
158   add_phi_arg (phi, va, loop_latch_edge (loop), UNKNOWN_LOCATION);
159 }
160 
161 /* Return the innermost superloop LOOP of USE_LOOP that is a superloop of
162    both DEF_LOOP and USE_LOOP.  */
163 
164 static inline class loop *
find_sibling_superloop(class loop * use_loop,class loop * def_loop)165 find_sibling_superloop (class loop *use_loop, class loop *def_loop)
166 {
167   unsigned ud = loop_depth (use_loop);
168   unsigned dd = loop_depth (def_loop);
169   gcc_assert (ud > 0 && dd > 0);
170   if (ud > dd)
171     use_loop = superloop_at_depth (use_loop, dd);
172   if (ud < dd)
173     def_loop = superloop_at_depth (def_loop, ud);
174   while (loop_outer (use_loop) != loop_outer (def_loop))
175     {
176       use_loop = loop_outer (use_loop);
177       def_loop = loop_outer (def_loop);
178       gcc_assert (use_loop && def_loop);
179     }
180   return use_loop;
181 }
182 
183 /* DEF_BB is a basic block containing a DEF that needs rewriting into
184    loop-closed SSA form.  USE_BLOCKS is the set of basic blocks containing
185    uses of DEF that "escape" from the loop containing DEF_BB (i.e. blocks in
186    USE_BLOCKS are dominated by DEF_BB but not in the loop father of DEF_B).
187    ALL_EXITS[I] is the set of all basic blocks that exit loop I.
188 
189    Compute the subset of LOOP_EXITS that exit the loop containing DEF_BB
190    or one of its loop fathers, in which DEF is live.  This set is returned
191    in the bitmap LIVE_EXITS.
192 
193    Instead of computing the complete livein set of the def, we use the loop
194    nesting tree as a form of poor man's structure analysis.  This greatly
195    speeds up the analysis, which is important because this function may be
196    called on all SSA names that need rewriting, one at a time.  */
197 
198 static void
compute_live_loop_exits(bitmap live_exits,bitmap use_blocks,bitmap * loop_exits,basic_block def_bb)199 compute_live_loop_exits (bitmap live_exits, bitmap use_blocks,
200 			 bitmap *loop_exits, basic_block def_bb)
201 {
202   unsigned i;
203   bitmap_iterator bi;
204   class loop *def_loop = def_bb->loop_father;
205   unsigned def_loop_depth = loop_depth (def_loop);
206   bitmap def_loop_exits;
207 
208   /* Normally the work list size is bounded by the number of basic
209      blocks in the largest loop.  We don't know this number, but we
210      can be fairly sure that it will be relatively small.  */
211   auto_vec<basic_block> worklist (MAX (8, n_basic_blocks_for_fn (cfun) / 128));
212 
213   EXECUTE_IF_SET_IN_BITMAP (use_blocks, 0, i, bi)
214     {
215       basic_block use_bb = BASIC_BLOCK_FOR_FN (cfun, i);
216       class loop *use_loop = use_bb->loop_father;
217       gcc_checking_assert (def_loop != use_loop
218 			   && ! flow_loop_nested_p (def_loop, use_loop));
219       if (! flow_loop_nested_p (use_loop, def_loop))
220 	use_bb = find_sibling_superloop (use_loop, def_loop)->header;
221       if (bitmap_set_bit (live_exits, use_bb->index))
222 	worklist.safe_push (use_bb);
223     }
224 
225   /* Iterate until the worklist is empty.  */
226   while (! worklist.is_empty ())
227     {
228       edge e;
229       edge_iterator ei;
230 
231       /* Pull a block off the worklist.  */
232       basic_block bb = worklist.pop ();
233 
234       /* Make sure we have at least enough room in the work list
235 	 for all predecessors of this block.  */
236       worklist.reserve (EDGE_COUNT (bb->preds));
237 
238       /* For each predecessor block.  */
239       FOR_EACH_EDGE (e, ei, bb->preds)
240 	{
241 	  basic_block pred = e->src;
242 	  class loop *pred_loop = pred->loop_father;
243 	  unsigned pred_loop_depth = loop_depth (pred_loop);
244 	  bool pred_visited;
245 
246 	  /* We should have met DEF_BB along the way.  */
247 	  gcc_assert (pred != ENTRY_BLOCK_PTR_FOR_FN (cfun));
248 
249 	  if (pred_loop_depth >= def_loop_depth)
250 	    {
251 	      if (pred_loop_depth > def_loop_depth)
252 		pred_loop = superloop_at_depth (pred_loop, def_loop_depth);
253 	      /* If we've reached DEF_LOOP, our train ends here.  */
254 	      if (pred_loop == def_loop)
255 		continue;
256 	    }
257 	  else if (! flow_loop_nested_p (pred_loop, def_loop))
258 	    pred = find_sibling_superloop (pred_loop, def_loop)->header;
259 
260 	  /* Add PRED to the LIVEIN set.  PRED_VISITED is true if
261 	     we had already added PRED to LIVEIN before.  */
262 	  pred_visited = !bitmap_set_bit (live_exits, pred->index);
263 
264 	  /* If we have visited PRED before, don't add it to the worklist.
265 	     If BB dominates PRED, then we're probably looking at a loop.
266 	     We're only interested in looking up in the dominance tree
267 	     because DEF_BB dominates all the uses.  */
268 	  if (pred_visited || dominated_by_p (CDI_DOMINATORS, pred, bb))
269 	    continue;
270 
271 	  worklist.quick_push (pred);
272 	}
273     }
274 
275   def_loop_exits = BITMAP_ALLOC (&loop_renamer_obstack);
276   for (class loop *loop = def_loop;
277        loop != current_loops->tree_root;
278        loop = loop_outer (loop))
279     bitmap_ior_into (def_loop_exits, loop_exits[loop->num]);
280   bitmap_and_into (live_exits, def_loop_exits);
281   BITMAP_FREE (def_loop_exits);
282 }
283 
284 /* Add a loop-closing PHI for VAR in basic block EXIT.  */
285 
286 static void
add_exit_phi(basic_block exit,tree var)287 add_exit_phi (basic_block exit, tree var)
288 {
289   gphi *phi;
290   edge e;
291   edge_iterator ei;
292 
293   /* Check that at least one of the edges entering the EXIT block exits
294      the loop, or a superloop of that loop, that VAR is defined in.  */
295   if (flag_checking)
296     {
297       gimple *def_stmt = SSA_NAME_DEF_STMT (var);
298       basic_block def_bb = gimple_bb (def_stmt);
299       FOR_EACH_EDGE (e, ei, exit->preds)
300 	{
301 	  class loop *aloop = find_common_loop (def_bb->loop_father,
302 						 e->src->loop_father);
303 	  if (!flow_bb_inside_loop_p (aloop, e->dest))
304 	    break;
305 	}
306       gcc_assert (e);
307     }
308 
309   phi = create_phi_node (NULL_TREE, exit);
310   create_new_def_for (var, phi, gimple_phi_result_ptr (phi));
311   FOR_EACH_EDGE (e, ei, exit->preds)
312     add_phi_arg (phi, var, e, UNKNOWN_LOCATION);
313 
314   if (dump_file && (dump_flags & TDF_DETAILS))
315     {
316       fprintf (dump_file, ";; Created LCSSA PHI: ");
317       print_gimple_stmt (dump_file, phi, 0, dump_flags);
318     }
319 }
320 
321 /* Add exit phis for VAR that is used in LIVEIN.
322    Exits of the loops are stored in LOOP_EXITS.  */
323 
324 static void
add_exit_phis_var(tree var,bitmap use_blocks,bitmap * loop_exits)325 add_exit_phis_var (tree var, bitmap use_blocks, bitmap *loop_exits)
326 {
327   unsigned index;
328   bitmap_iterator bi;
329   basic_block def_bb = gimple_bb (SSA_NAME_DEF_STMT (var));
330   bitmap live_exits = BITMAP_ALLOC (&loop_renamer_obstack);
331 
332   gcc_checking_assert (! bitmap_bit_p (use_blocks, def_bb->index));
333 
334   compute_live_loop_exits (live_exits, use_blocks, loop_exits, def_bb);
335 
336   EXECUTE_IF_SET_IN_BITMAP (live_exits, 0, index, bi)
337     {
338       add_exit_phi (BASIC_BLOCK_FOR_FN (cfun, index), var);
339     }
340 
341   BITMAP_FREE (live_exits);
342 }
343 
344 /* Add exit phis for the names marked in NAMES_TO_RENAME.
345    Exits of the loops are stored in EXITS.  Sets of blocks where the ssa
346    names are used are stored in USE_BLOCKS.  */
347 
348 static void
add_exit_phis(bitmap names_to_rename,bitmap * use_blocks,bitmap * loop_exits)349 add_exit_phis (bitmap names_to_rename, bitmap *use_blocks, bitmap *loop_exits)
350 {
351   unsigned i;
352   bitmap_iterator bi;
353 
354   EXECUTE_IF_SET_IN_BITMAP (names_to_rename, 0, i, bi)
355     {
356       add_exit_phis_var (ssa_name (i), use_blocks[i], loop_exits);
357     }
358 }
359 
360 /* Fill the array of bitmaps LOOP_EXITS with all loop exit edge targets.  */
361 
362 static void
get_loops_exits(bitmap * loop_exits)363 get_loops_exits (bitmap *loop_exits)
364 {
365   unsigned j;
366   edge e;
367 
368   for (auto loop : loops_list (cfun, 0))
369     {
370       auto_vec<edge> exit_edges = get_loop_exit_edges (loop);
371       loop_exits[loop->num] = BITMAP_ALLOC (&loop_renamer_obstack);
372       FOR_EACH_VEC_ELT (exit_edges, j, e)
373         bitmap_set_bit (loop_exits[loop->num], e->dest->index);
374     }
375 }
376 
377 /* For USE in BB, if it is used outside of the loop it is defined in,
378    mark it for rewrite.  Record basic block BB where it is used
379    to USE_BLOCKS.  Record the ssa name index to NEED_PHIS bitmap.
380    Note that for USEs in phis, BB should be the src of the edge corresponding to
381    the use, rather than the bb containing the phi.  */
382 
383 static void
find_uses_to_rename_use(basic_block bb,tree use,bitmap * use_blocks,bitmap need_phis)384 find_uses_to_rename_use (basic_block bb, tree use, bitmap *use_blocks,
385 			 bitmap need_phis)
386 {
387   unsigned ver;
388   basic_block def_bb;
389   class loop *def_loop;
390 
391   if (TREE_CODE (use) != SSA_NAME)
392     return;
393 
394   ver = SSA_NAME_VERSION (use);
395   def_bb = gimple_bb (SSA_NAME_DEF_STMT (use));
396   if (!def_bb)
397     return;
398   def_loop = def_bb->loop_father;
399 
400   /* If the definition is not inside a loop, it is not interesting.  */
401   if (!loop_outer (def_loop))
402     return;
403 
404   /* If the use is not outside of the loop it is defined in, it is not
405      interesting.  */
406   if (flow_bb_inside_loop_p (def_loop, bb))
407     return;
408 
409   /* If we're seeing VER for the first time, we still have to allocate
410      a bitmap for its uses.  */
411   if (bitmap_set_bit (need_phis, ver))
412     use_blocks[ver] = BITMAP_ALLOC (&loop_renamer_obstack);
413   bitmap_set_bit (use_blocks[ver], bb->index);
414 }
415 
416 /* For uses matching USE_FLAGS in STMT, mark names that are used outside of the
417    loop they are defined to rewrite.  Record the set of blocks in which the ssa
418    names are used to USE_BLOCKS, and the ssa names themselves to NEED_PHIS.  */
419 
420 static void
find_uses_to_rename_stmt(gimple * stmt,bitmap * use_blocks,bitmap need_phis,int use_flags)421 find_uses_to_rename_stmt (gimple *stmt, bitmap *use_blocks, bitmap need_phis,
422 			  int use_flags)
423 {
424   ssa_op_iter iter;
425   tree var;
426   basic_block bb = gimple_bb (stmt);
427 
428   if (is_gimple_debug (stmt))
429     return;
430 
431   /* FOR_EACH_SSA_TREE_OPERAND iterator does not allows SSA_OP_VIRTUAL_USES
432      only.  */
433   if (use_flags == SSA_OP_VIRTUAL_USES)
434     {
435       tree vuse = gimple_vuse (stmt);
436       if (vuse != NULL_TREE)
437 	find_uses_to_rename_use (bb, gimple_vuse (stmt), use_blocks, need_phis);
438     }
439   else
440     FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, use_flags)
441       find_uses_to_rename_use (bb, var, use_blocks, need_phis);
442 }
443 
444 /* Marks names matching USE_FLAGS that are used in BB and outside of the loop
445    they are defined in for rewrite.  Records the set of blocks in which the ssa
446    names are used to USE_BLOCKS.  Record the SSA names that will
447    need exit PHIs in NEED_PHIS.  */
448 
449 static void
find_uses_to_rename_bb(basic_block bb,bitmap * use_blocks,bitmap need_phis,int use_flags)450 find_uses_to_rename_bb (basic_block bb, bitmap *use_blocks, bitmap need_phis,
451 			int use_flags)
452 {
453   edge e;
454   edge_iterator ei;
455   bool do_virtuals = (use_flags & SSA_OP_VIRTUAL_USES) != 0;
456   bool do_nonvirtuals = (use_flags & SSA_OP_USE) != 0;
457 
458   FOR_EACH_EDGE (e, ei, bb->succs)
459     for (gphi_iterator bsi = gsi_start_phis (e->dest); !gsi_end_p (bsi);
460 	 gsi_next (&bsi))
461       {
462         gphi *phi = bsi.phi ();
463 	bool virtual_p = virtual_operand_p (gimple_phi_result (phi));
464 	if ((virtual_p && do_virtuals)
465 	    || (!virtual_p && do_nonvirtuals))
466 	  find_uses_to_rename_use (bb, PHI_ARG_DEF_FROM_EDGE (phi, e),
467 				   use_blocks, need_phis);
468       }
469 
470   for (gimple_stmt_iterator bsi = gsi_start_bb (bb); !gsi_end_p (bsi);
471        gsi_next (&bsi))
472     find_uses_to_rename_stmt (gsi_stmt (bsi), use_blocks, need_phis,
473 			      use_flags);
474 }
475 
476 /* Marks names matching USE_FLAGS that are used outside of the loop they are
477    defined in for rewrite.  Records the set of blocks in which the ssa names are
478    used to USE_BLOCKS.  Record the SSA names that will need exit PHIs in
479    NEED_PHIS.  If CHANGED_BBS is not NULL, scan only blocks in this set.  */
480 
481 static void
find_uses_to_rename(bitmap changed_bbs,bitmap * use_blocks,bitmap need_phis,int use_flags)482 find_uses_to_rename (bitmap changed_bbs, bitmap *use_blocks, bitmap need_phis,
483 		     int use_flags)
484 {
485   basic_block bb;
486   unsigned index;
487   bitmap_iterator bi;
488 
489   if (changed_bbs)
490     EXECUTE_IF_SET_IN_BITMAP (changed_bbs, 0, index, bi)
491       {
492 	bb = BASIC_BLOCK_FOR_FN (cfun, index);
493 	if (bb)
494 	  find_uses_to_rename_bb (bb, use_blocks, need_phis, use_flags);
495       }
496   else
497     FOR_EACH_BB_FN (bb, cfun)
498       find_uses_to_rename_bb (bb, use_blocks, need_phis, use_flags);
499 }
500 
501 /* Mark uses of DEF that are used outside of the loop they are defined in for
502    rewrite.  Record the set of blocks in which the ssa names are used to
503    USE_BLOCKS.  Record the SSA names that will need exit PHIs in NEED_PHIS.  */
504 
505 static void
find_uses_to_rename_def(tree def,bitmap * use_blocks,bitmap need_phis)506 find_uses_to_rename_def (tree def, bitmap *use_blocks, bitmap need_phis)
507 {
508   gimple *use_stmt;
509   imm_use_iterator imm_iter;
510 
511   FOR_EACH_IMM_USE_STMT (use_stmt, imm_iter, def)
512     {
513       if (is_gimple_debug (use_stmt))
514 	continue;
515 
516       basic_block use_bb = gimple_bb (use_stmt);
517 
518       use_operand_p use_p;
519       FOR_EACH_IMM_USE_ON_STMT (use_p, imm_iter)
520 	{
521 	  if (gimple_code (use_stmt) == GIMPLE_PHI)
522 	    {
523 	      edge e = gimple_phi_arg_edge (as_a <gphi *> (use_stmt),
524 					    PHI_ARG_INDEX_FROM_USE (use_p));
525 	      use_bb = e->src;
526 	    }
527 	  find_uses_to_rename_use (use_bb, USE_FROM_PTR (use_p), use_blocks,
528 				   need_phis);
529 	}
530     }
531 }
532 
533 /* Marks names matching USE_FLAGS that are defined in LOOP and used outside of
534    it for rewrite.  Records the set of blocks in which the ssa names are used to
535    USE_BLOCKS.  Record the SSA names that will need exit PHIs in NEED_PHIS.  */
536 
537 static void
find_uses_to_rename_in_loop(class loop * loop,bitmap * use_blocks,bitmap need_phis,int use_flags)538 find_uses_to_rename_in_loop (class loop *loop, bitmap *use_blocks,
539 			     bitmap need_phis, int use_flags)
540 {
541   bool do_virtuals = (use_flags & SSA_OP_VIRTUAL_USES) != 0;
542   bool do_nonvirtuals = (use_flags & SSA_OP_USE) != 0;
543   int def_flags = ((do_virtuals ? SSA_OP_VIRTUAL_DEFS : 0)
544 		   | (do_nonvirtuals ? SSA_OP_DEF : 0));
545 
546 
547   basic_block *bbs = get_loop_body (loop);
548 
549   for (unsigned int i = 0; i < loop->num_nodes; i++)
550     {
551       basic_block bb = bbs[i];
552 
553       for (gphi_iterator bsi = gsi_start_phis (bb); !gsi_end_p (bsi);
554 	   gsi_next (&bsi))
555 	{
556 	  gphi *phi = bsi.phi ();
557 	  tree res = gimple_phi_result (phi);
558 	  bool virtual_p = virtual_operand_p (res);
559 	  if ((virtual_p && do_virtuals)
560 	      || (!virtual_p && do_nonvirtuals))
561 	    find_uses_to_rename_def (res, use_blocks, need_phis);
562       }
563 
564       for (gimple_stmt_iterator bsi = gsi_start_bb (bb); !gsi_end_p (bsi);
565 	   gsi_next (&bsi))
566 	{
567 	  gimple *stmt = gsi_stmt (bsi);
568 	  /* FOR_EACH_SSA_TREE_OPERAND iterator does not allows
569 	     SSA_OP_VIRTUAL_DEFS only.  */
570 	  if (def_flags == SSA_OP_VIRTUAL_DEFS)
571 	    {
572 	      tree vdef = gimple_vdef (stmt);
573 	      if (vdef != NULL)
574 		find_uses_to_rename_def (vdef, use_blocks, need_phis);
575 	    }
576 	  else
577 	    {
578 	      tree var;
579 	      ssa_op_iter iter;
580 	      FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, def_flags)
581 		find_uses_to_rename_def (var, use_blocks, need_phis);
582 	    }
583 	}
584     }
585 
586   XDELETEVEC (bbs);
587 }
588 
589 /* Rewrites the program into a loop closed ssa form -- i.e. inserts extra
590    phi nodes to ensure that no variable is used outside the loop it is
591    defined in.
592 
593    This strengthening of the basic ssa form has several advantages:
594 
595    1) Updating it during unrolling/peeling/versioning is trivial, since
596       we do not need to care about the uses outside of the loop.
597       The same applies to virtual operands which are also rewritten into
598       loop closed SSA form.  Note that virtual operands are always live
599       until function exit.
600    2) The behavior of all uses of an induction variable is the same.
601       Without this, you need to distinguish the case when the variable
602       is used outside of the loop it is defined in, for example
603 
604       for (i = 0; i < 100; i++)
605 	{
606 	  for (j = 0; j < 100; j++)
607 	    {
608 	      k = i + j;
609 	      use1 (k);
610 	    }
611 	  use2 (k);
612 	}
613 
614       Looking from the outer loop with the normal SSA form, the first use of k
615       is not well-behaved, while the second one is an induction variable with
616       base 99 and step 1.
617 
618       If LOOP is non-null, only rewrite uses that have defs in LOOP.  Otherwise,
619       if CHANGED_BBS is not NULL, we look for uses outside loops only in the
620       basic blocks in this set.
621 
622       USE_FLAGS allows us to specify whether we want virtual, non-virtual or
623       both variables rewritten.
624 
625       UPDATE_FLAG is used in the call to update_ssa.  See
626       TODO_update_ssa* for documentation.  */
627 
628 void
rewrite_into_loop_closed_ssa_1(bitmap changed_bbs,unsigned update_flag,int use_flags,class loop * loop)629 rewrite_into_loop_closed_ssa_1 (bitmap changed_bbs, unsigned update_flag,
630 				int use_flags, class loop *loop)
631 {
632   bitmap *use_blocks;
633   bitmap names_to_rename;
634 
635   loops_state_set (LOOP_CLOSED_SSA);
636   if (number_of_loops (cfun) <= 1)
637     return;
638 
639   /* If the pass has caused the SSA form to be out-of-date, update it
640      now.  */
641   if (update_flag != 0)
642     update_ssa (update_flag);
643   else if (flag_checking)
644     verify_ssa (true, true);
645 
646   bitmap_obstack_initialize (&loop_renamer_obstack);
647 
648   names_to_rename = BITMAP_ALLOC (&loop_renamer_obstack);
649 
650   /* Uses of names to rename.  We don't have to initialize this array,
651      because we know that we will only have entries for the SSA names
652      in NAMES_TO_RENAME.  */
653   use_blocks = XNEWVEC (bitmap, num_ssa_names);
654 
655   if (loop != NULL)
656     {
657       gcc_assert (changed_bbs == NULL);
658       find_uses_to_rename_in_loop (loop, use_blocks, names_to_rename,
659 				   use_flags);
660     }
661   else
662     {
663       gcc_assert (loop == NULL);
664       find_uses_to_rename (changed_bbs, use_blocks, names_to_rename, use_flags);
665     }
666 
667   if (!bitmap_empty_p (names_to_rename))
668     {
669       /* An array of bitmaps where LOOP_EXITS[I] is the set of basic blocks
670 	 that are the destination of an edge exiting loop number I.  */
671       bitmap *loop_exits = XNEWVEC (bitmap, number_of_loops (cfun));
672       get_loops_exits (loop_exits);
673 
674       /* Add the PHI nodes on exits of the loops for the names we need to
675 	 rewrite.  */
676       add_exit_phis (names_to_rename, use_blocks, loop_exits);
677 
678       free (loop_exits);
679 
680       /* Fix up all the names found to be used outside their original
681 	 loops.  */
682       update_ssa (TODO_update_ssa);
683     }
684 
685   bitmap_obstack_release (&loop_renamer_obstack);
686   free (use_blocks);
687 }
688 
689 /* Rewrites the non-virtual defs and uses into a loop closed ssa form.  If
690    CHANGED_BBS is not NULL, we look for uses outside loops only in the basic
691    blocks in this set.  UPDATE_FLAG is used in the call to update_ssa.  See
692    TODO_update_ssa* for documentation.  */
693 
694 void
rewrite_into_loop_closed_ssa(bitmap changed_bbs,unsigned update_flag)695 rewrite_into_loop_closed_ssa (bitmap changed_bbs, unsigned update_flag)
696 {
697   rewrite_into_loop_closed_ssa_1 (changed_bbs, update_flag, SSA_OP_USE, NULL);
698 }
699 
700 /* Rewrites virtual defs and uses with def in LOOP into loop closed ssa
701    form.  */
702 
703 void
rewrite_virtuals_into_loop_closed_ssa(class loop * loop)704 rewrite_virtuals_into_loop_closed_ssa (class loop *loop)
705 {
706   rewrite_into_loop_closed_ssa_1 (NULL, 0, SSA_OP_VIRTUAL_USES, loop);
707 }
708 
709 /* Check invariants of the loop closed ssa form for the def in DEF_BB.  */
710 
711 static void
check_loop_closed_ssa_def(basic_block def_bb,tree def)712 check_loop_closed_ssa_def (basic_block def_bb, tree def)
713 {
714   use_operand_p use_p;
715   imm_use_iterator iterator;
716   FOR_EACH_IMM_USE_FAST (use_p, iterator, def)
717     {
718       if (is_gimple_debug (USE_STMT (use_p)))
719 	continue;
720 
721       basic_block use_bb = gimple_bb (USE_STMT (use_p));
722       if (is_a <gphi *> (USE_STMT (use_p)))
723 	use_bb = EDGE_PRED (use_bb, PHI_ARG_INDEX_FROM_USE (use_p))->src;
724 
725       gcc_assert (flow_bb_inside_loop_p (def_bb->loop_father, use_bb));
726     }
727 }
728 
729 /* Checks invariants of loop closed ssa form in BB.  */
730 
731 static void
check_loop_closed_ssa_bb(basic_block bb)732 check_loop_closed_ssa_bb (basic_block bb)
733 {
734   for (gphi_iterator bsi = gsi_start_phis (bb); !gsi_end_p (bsi);
735        gsi_next (&bsi))
736     {
737       gphi *phi = bsi.phi ();
738 
739       if (!virtual_operand_p (PHI_RESULT (phi)))
740 	check_loop_closed_ssa_def (bb, PHI_RESULT (phi));
741     }
742 
743   for (gimple_stmt_iterator bsi = gsi_start_nondebug_bb (bb); !gsi_end_p (bsi);
744        gsi_next_nondebug (&bsi))
745     {
746       ssa_op_iter iter;
747       tree var;
748       gimple *stmt = gsi_stmt (bsi);
749 
750       FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, SSA_OP_DEF)
751 	check_loop_closed_ssa_def (bb, var);
752     }
753 }
754 
755 /* Checks that invariants of the loop closed ssa form are preserved.
756    Call verify_ssa when VERIFY_SSA_P is true.  Note all loops are checked
757    if LOOP is NULL, otherwise, only LOOP is checked.  */
758 
759 DEBUG_FUNCTION void
verify_loop_closed_ssa(bool verify_ssa_p,class loop * loop)760 verify_loop_closed_ssa (bool verify_ssa_p, class loop *loop)
761 {
762   if (number_of_loops (cfun) <= 1)
763     return;
764 
765   if (verify_ssa_p)
766     verify_ssa (false, true);
767 
768   timevar_push (TV_VERIFY_LOOP_CLOSED);
769 
770   if (loop == NULL)
771     {
772       basic_block bb;
773 
774       FOR_EACH_BB_FN (bb, cfun)
775 	if (bb->loop_father && bb->loop_father->num > 0)
776 	  check_loop_closed_ssa_bb (bb);
777     }
778   else
779     {
780       basic_block *bbs = get_loop_body (loop);
781 
782       for (unsigned i = 0; i < loop->num_nodes; ++i)
783 	check_loop_closed_ssa_bb (bbs[i]);
784 
785       free (bbs);
786     }
787 
788   timevar_pop (TV_VERIFY_LOOP_CLOSED);
789 }
790 
791 /* Split loop exit edge EXIT.  The things are a bit complicated by a need to
792    preserve the loop closed ssa form.  If COPY_CONSTANTS_P is true then
793    forwarder PHIs are also created for constant arguments.
794    The newly created block is returned.  */
795 
796 basic_block
split_loop_exit_edge(edge exit,bool copy_constants_p)797 split_loop_exit_edge (edge exit, bool copy_constants_p)
798 {
799   basic_block dest = exit->dest;
800   basic_block bb = split_edge (exit);
801   gphi *phi, *new_phi;
802   tree new_name, name;
803   use_operand_p op_p;
804   gphi_iterator psi;
805   location_t locus;
806 
807   for (psi = gsi_start_phis (dest); !gsi_end_p (psi); gsi_next (&psi))
808     {
809       phi = psi.phi ();
810       op_p = PHI_ARG_DEF_PTR_FROM_EDGE (phi, single_succ_edge (bb));
811       locus = gimple_phi_arg_location_from_edge (phi, single_succ_edge (bb));
812 
813       name = USE_FROM_PTR (op_p);
814 
815       /* If the argument of the PHI node is a constant, we do not need
816 	 to keep it inside loop.  */
817       if (TREE_CODE (name) != SSA_NAME
818 	  && !copy_constants_p)
819 	continue;
820 
821       /* Otherwise create an auxiliary phi node that will copy the value
822 	 of the SSA name out of the loop.  */
823       new_name = duplicate_ssa_name (PHI_RESULT (phi), NULL);
824       new_phi = create_phi_node (new_name, bb);
825       add_phi_arg (new_phi, name, exit, locus);
826       SET_USE (op_p, new_name);
827     }
828 
829   return bb;
830 }
831 
832 /* Returns the basic block in that statements should be emitted for induction
833    variables incremented at the end of the LOOP.  */
834 
835 basic_block
ip_end_pos(class loop * loop)836 ip_end_pos (class loop *loop)
837 {
838   return loop->latch;
839 }
840 
841 /* Returns the basic block in that statements should be emitted for induction
842    variables incremented just before exit condition of a LOOP.  */
843 
844 basic_block
ip_normal_pos(class loop * loop)845 ip_normal_pos (class loop *loop)
846 {
847   gimple *last;
848   basic_block bb;
849   edge exit;
850 
851   if (!single_pred_p (loop->latch))
852     return NULL;
853 
854   bb = single_pred (loop->latch);
855   last = last_stmt (bb);
856   if (!last
857       || gimple_code (last) != GIMPLE_COND)
858     return NULL;
859 
860   exit = EDGE_SUCC (bb, 0);
861   if (exit->dest == loop->latch)
862     exit = EDGE_SUCC (bb, 1);
863 
864   if (flow_bb_inside_loop_p (loop, exit->dest))
865     return NULL;
866 
867   return bb;
868 }
869 
870 /* Stores the standard position for induction variable increment in LOOP
871    (just before the exit condition if it is available and latch block is empty,
872    end of the latch block otherwise) to BSI.  INSERT_AFTER is set to true if
873    the increment should be inserted after *BSI.  */
874 
875 void
standard_iv_increment_position(class loop * loop,gimple_stmt_iterator * bsi,bool * insert_after)876 standard_iv_increment_position (class loop *loop, gimple_stmt_iterator *bsi,
877 				bool *insert_after)
878 {
879   basic_block bb = ip_normal_pos (loop), latch = ip_end_pos (loop);
880   gimple *last = last_stmt (latch);
881 
882   if (!bb
883       || (last && gimple_code (last) != GIMPLE_LABEL))
884     {
885       *bsi = gsi_last_bb (latch);
886       *insert_after = true;
887     }
888   else
889     {
890       *bsi = gsi_last_bb (bb);
891       *insert_after = false;
892     }
893 }
894 
895 /* Copies phi node arguments for duplicated blocks.  The index of the first
896    duplicated block is FIRST_NEW_BLOCK.  */
897 
898 static void
copy_phi_node_args(unsigned first_new_block)899 copy_phi_node_args (unsigned first_new_block)
900 {
901   unsigned i;
902 
903   for (i = first_new_block; i < (unsigned) last_basic_block_for_fn (cfun); i++)
904     BASIC_BLOCK_FOR_FN (cfun, i)->flags |= BB_DUPLICATED;
905 
906   for (i = first_new_block; i < (unsigned) last_basic_block_for_fn (cfun); i++)
907     add_phi_args_after_copy_bb (BASIC_BLOCK_FOR_FN (cfun, i));
908 
909   for (i = first_new_block; i < (unsigned) last_basic_block_for_fn (cfun); i++)
910     BASIC_BLOCK_FOR_FN (cfun, i)->flags &= ~BB_DUPLICATED;
911 }
912 
913 
914 /* The same as cfgloopmanip.cc:duplicate_loop_body_to_header_edge, but also
915    updates the PHI nodes at start of the copied region.  In order to
916    achieve this, only loops whose exits all lead to the same location
917    are handled.
918 
919    Notice that we do not completely update the SSA web after
920    duplication.  The caller is responsible for calling update_ssa
921    after the loop has been duplicated.  */
922 
923 bool
gimple_duplicate_loop_body_to_header_edge(class loop * loop,edge e,unsigned int ndupl,sbitmap wont_exit,edge orig,vec<edge> * to_remove,int flags)924 gimple_duplicate_loop_body_to_header_edge (class loop *loop, edge e,
925 					   unsigned int ndupl,
926 					   sbitmap wont_exit, edge orig,
927 					   vec<edge> *to_remove, int flags)
928 {
929   unsigned first_new_block;
930 
931   if (!loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES))
932     return false;
933   if (!loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS))
934     return false;
935 
936   first_new_block = last_basic_block_for_fn (cfun);
937   if (!duplicate_loop_body_to_header_edge (loop, e, ndupl, wont_exit, orig,
938 					   to_remove, flags))
939     return false;
940 
941   /* Readd the removed phi args for e.  */
942   flush_pending_stmts (e);
943 
944   /* Copy the phi node arguments.  */
945   copy_phi_node_args (first_new_block);
946 
947   scev_reset ();
948 
949   return true;
950 }
951 
952 /* Returns true if we can unroll LOOP FACTOR times.  Number
953    of iterations of the loop is returned in NITER.  */
954 
955 bool
can_unroll_loop_p(class loop * loop,unsigned factor,class tree_niter_desc * niter)956 can_unroll_loop_p (class loop *loop, unsigned factor,
957 		   class tree_niter_desc *niter)
958 {
959   edge exit;
960 
961   /* Check whether unrolling is possible.  We only want to unroll loops
962      for that we are able to determine number of iterations.  We also
963      want to split the extra iterations of the loop from its end,
964      therefore we require that the loop has precisely one
965      exit.  */
966 
967   exit = single_dom_exit (loop);
968   if (!exit)
969     return false;
970 
971   if (!number_of_iterations_exit (loop, exit, niter, false)
972       || niter->cmp == ERROR_MARK
973       /* Scalar evolutions analysis might have copy propagated
974 	 the abnormal ssa names into these expressions, hence
975 	 emitting the computations based on them during loop
976 	 unrolling might create overlapping life ranges for
977 	 them, and failures in out-of-ssa.  */
978       || contains_abnormal_ssa_name_p (niter->may_be_zero)
979       || contains_abnormal_ssa_name_p (niter->control.base)
980       || contains_abnormal_ssa_name_p (niter->control.step)
981       || contains_abnormal_ssa_name_p (niter->bound))
982     return false;
983 
984   /* And of course, we must be able to duplicate the loop.  */
985   if (!can_duplicate_loop_p (loop))
986     return false;
987 
988   /* The final loop should be small enough.  */
989   if (tree_num_loop_insns (loop, &eni_size_weights) * factor
990       > (unsigned) param_max_unrolled_insns)
991     return false;
992 
993   return true;
994 }
995 
996 /* Determines the conditions that control execution of LOOP unrolled FACTOR
997    times.  DESC is number of iterations of LOOP.  ENTER_COND is set to
998    condition that must be true if the main loop can be entered.
999    If the loop does not always iterate an exact multiple of FACTOR times,
1000    EXIT_BASE, EXIT_STEP, EXIT_CMP and EXIT_BOUND are set to values describing
1001    how the exit from the unrolled loop should be controlled.  Otherwise,
1002    the trees are set to null and EXIT_CMP is set to ERROR_MARK.  */
1003 
1004 static void
determine_exit_conditions(class loop * loop,class tree_niter_desc * desc,unsigned factor,tree * enter_cond,tree * exit_base,tree * exit_step,enum tree_code * exit_cmp,tree * exit_bound)1005 determine_exit_conditions (class loop *loop, class tree_niter_desc *desc,
1006 			   unsigned factor, tree *enter_cond,
1007 			   tree *exit_base, tree *exit_step,
1008 			   enum tree_code *exit_cmp, tree *exit_bound)
1009 {
1010   gimple_seq stmts;
1011   tree base = desc->control.base;
1012   tree step = desc->control.step;
1013   tree bound = desc->bound;
1014   tree type = TREE_TYPE (step);
1015   tree bigstep, delta;
1016   tree min = lower_bound_in_type (type, type);
1017   tree max = upper_bound_in_type (type, type);
1018   enum tree_code cmp = desc->cmp;
1019   tree cond = boolean_true_node, assum;
1020 
1021   /* For pointers, do the arithmetics in the type of step.  */
1022   base = fold_convert (type, base);
1023   bound = fold_convert (type, bound);
1024 
1025   *enter_cond = boolean_false_node;
1026   *exit_base = NULL_TREE;
1027   *exit_step = NULL_TREE;
1028   *exit_cmp = ERROR_MARK;
1029   *exit_bound = NULL_TREE;
1030   gcc_assert (cmp != ERROR_MARK);
1031 
1032   /* We only need to be correct when we answer question
1033      "Do at least FACTOR more iterations remain?" in the unrolled loop.
1034      Thus, transforming BASE + STEP * i <> BOUND to
1035      BASE + STEP * i < BOUND is ok.  */
1036   if (cmp == NE_EXPR)
1037     {
1038       if (tree_int_cst_sign_bit (step))
1039 	cmp = GT_EXPR;
1040       else
1041 	cmp = LT_EXPR;
1042     }
1043   else if (cmp == LT_EXPR)
1044     {
1045       gcc_assert (!tree_int_cst_sign_bit (step));
1046     }
1047   else if (cmp == GT_EXPR)
1048     {
1049       gcc_assert (tree_int_cst_sign_bit (step));
1050     }
1051   else
1052     gcc_unreachable ();
1053 
1054   /* The main body of the loop may be entered iff:
1055 
1056      1) desc->may_be_zero is false.
1057      2) it is possible to check that there are at least FACTOR iterations
1058 	of the loop, i.e., BOUND - step * FACTOR does not overflow.
1059      3) # of iterations is at least FACTOR  */
1060 
1061   if (!integer_zerop (desc->may_be_zero))
1062     cond = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
1063 			invert_truthvalue (desc->may_be_zero),
1064 			cond);
1065 
1066   bigstep = fold_build2 (MULT_EXPR, type, step,
1067 			 build_int_cst_type (type, factor));
1068   delta = fold_build2 (MINUS_EXPR, type, bigstep, step);
1069   if (cmp == LT_EXPR)
1070     assum = fold_build2 (GE_EXPR, boolean_type_node,
1071 			 bound,
1072 			 fold_build2 (PLUS_EXPR, type, min, delta));
1073   else
1074     assum = fold_build2 (LE_EXPR, boolean_type_node,
1075 			 bound,
1076 			 fold_build2 (PLUS_EXPR, type, max, delta));
1077   cond = fold_build2 (TRUTH_AND_EXPR, boolean_type_node, assum, cond);
1078 
1079   bound = fold_build2 (MINUS_EXPR, type, bound, delta);
1080   assum = fold_build2 (cmp, boolean_type_node, base, bound);
1081   cond = fold_build2 (TRUTH_AND_EXPR, boolean_type_node, assum, cond);
1082 
1083   if (integer_nonzerop (cond)
1084       && integer_zerop (desc->may_be_zero))
1085     {
1086       /* Convert the latch count to an iteration count.  */
1087       tree niter = fold_build2 (PLUS_EXPR, type, desc->niter,
1088 				build_one_cst (type));
1089       if (multiple_of_p (type, niter, bigstep))
1090 	return;
1091     }
1092 
1093   cond = force_gimple_operand (unshare_expr (cond), &stmts, false, NULL_TREE);
1094   if (stmts)
1095     gsi_insert_seq_on_edge_immediate (loop_preheader_edge (loop), stmts);
1096   /* cond now may be a gimple comparison, which would be OK, but also any
1097      other gimple rhs (say a && b).  In this case we need to force it to
1098      operand.  */
1099   if (!is_gimple_condexpr (cond))
1100     {
1101       cond = force_gimple_operand (cond, &stmts, true, NULL_TREE);
1102       if (stmts)
1103 	gsi_insert_seq_on_edge_immediate (loop_preheader_edge (loop), stmts);
1104     }
1105   *enter_cond = cond;
1106 
1107   base = force_gimple_operand (unshare_expr (base), &stmts, true, NULL_TREE);
1108   if (stmts)
1109     gsi_insert_seq_on_edge_immediate (loop_preheader_edge (loop), stmts);
1110   bound = force_gimple_operand (unshare_expr (bound), &stmts, true, NULL_TREE);
1111   if (stmts)
1112     gsi_insert_seq_on_edge_immediate (loop_preheader_edge (loop), stmts);
1113 
1114   *exit_base = base;
1115   *exit_step = bigstep;
1116   *exit_cmp = cmp;
1117   *exit_bound = bound;
1118 }
1119 
1120 /* Scales the frequencies of all basic blocks in LOOP that are strictly
1121    dominated by BB by NUM/DEN.  */
1122 
1123 static void
scale_dominated_blocks_in_loop(class loop * loop,basic_block bb,profile_count num,profile_count den)1124 scale_dominated_blocks_in_loop (class loop *loop, basic_block bb,
1125 				profile_count num, profile_count den)
1126 {
1127   basic_block son;
1128 
1129   if (!den.nonzero_p () && !(num == profile_count::zero ()))
1130     return;
1131 
1132   for (son = first_dom_son (CDI_DOMINATORS, bb);
1133        son;
1134        son = next_dom_son (CDI_DOMINATORS, son))
1135     {
1136       if (!flow_bb_inside_loop_p (loop, son))
1137 	continue;
1138       scale_bbs_frequencies_profile_count (&son, 1, num, den);
1139       scale_dominated_blocks_in_loop (loop, son, num, den);
1140     }
1141 }
1142 
1143 /* Return estimated niter for LOOP after unrolling by FACTOR times.  */
1144 
1145 gcov_type
niter_for_unrolled_loop(class loop * loop,unsigned factor)1146 niter_for_unrolled_loop (class loop *loop, unsigned factor)
1147 {
1148   gcc_assert (factor != 0);
1149   bool profile_p = false;
1150   gcov_type est_niter = expected_loop_iterations_unbounded (loop, &profile_p);
1151   /* Note that this is really CEIL (est_niter + 1, factor) - 1, where the
1152      "+ 1" converts latch iterations to loop iterations and the "- 1"
1153      converts back.  */
1154   gcov_type new_est_niter = est_niter / factor;
1155 
1156   if (est_niter == -1)
1157     return -1;
1158 
1159   /* Without profile feedback, loops for which we do not know a better estimate
1160      are assumed to roll 10 times.  When we unroll such loop, it appears to
1161      roll too little, and it may even seem to be cold.  To avoid this, we
1162      ensure that the created loop appears to roll at least 5 times (but at
1163      most as many times as before unrolling).  Don't do adjustment if profile
1164      feedback is present.  */
1165   if (new_est_niter < 5 && !profile_p)
1166     {
1167       if (est_niter < 5)
1168 	new_est_niter = est_niter;
1169       else
1170 	new_est_niter = 5;
1171     }
1172 
1173   if (loop->any_upper_bound)
1174     {
1175       /* As above, this is really CEIL (upper_bound + 1, factor) - 1.  */
1176       widest_int bound = wi::udiv_floor (loop->nb_iterations_upper_bound,
1177 					 factor);
1178       if (wi::ltu_p (bound, new_est_niter))
1179 	new_est_niter = bound.to_uhwi ();
1180     }
1181 
1182   return new_est_niter;
1183 }
1184 
1185 /* Unroll LOOP FACTOR times.  LOOP is known to have a single exit edge
1186    whose source block dominates the latch.  DESC describes the number of
1187    iterations of LOOP.
1188 
1189    If N is number of iterations of the loop and MAY_BE_ZERO is the condition
1190    under that loop exits in the first iteration even if N != 0,
1191 
1192    while (1)
1193      {
1194        x = phi (init, next);
1195 
1196        pre;
1197        if (st)
1198          break;
1199        post;
1200      }
1201 
1202    becomes (with possibly the exit conditions formulated a bit differently,
1203    avoiding the need to create a new iv):
1204 
1205    if (MAY_BE_ZERO || N < FACTOR)
1206      goto rest;
1207 
1208    do
1209      {
1210        x = phi (init, next);
1211 
1212        pre;
1213        post;
1214        pre;
1215        post;
1216        ...
1217        pre;
1218        post;
1219        N -= FACTOR;
1220 
1221      } while (N >= FACTOR);
1222 
1223    rest:
1224      init' = phi (init, x);
1225 
1226    while (1)
1227      {
1228        x = phi (init', next);
1229 
1230        pre;
1231        if (st)
1232          break;
1233        post;
1234      }
1235 
1236    Before the loop is unrolled, TRANSFORM is called for it (only for the
1237    unrolled loop, but not for its versioned copy).  DATA is passed to
1238    TRANSFORM.  */
1239 
1240 /* Probability in % that the unrolled loop is entered.  Just a guess.  */
1241 #define PROB_UNROLLED_LOOP_ENTERED 90
1242 
1243 void
tree_transform_and_unroll_loop(class loop * loop,unsigned factor,class tree_niter_desc * desc,transform_callback transform,void * data)1244 tree_transform_and_unroll_loop (class loop *loop, unsigned factor,
1245 				class tree_niter_desc *desc,
1246 				transform_callback transform,
1247 				void *data)
1248 {
1249   gcov_type new_est_niter = niter_for_unrolled_loop (loop, factor);
1250   unsigned irr = loop_preheader_edge (loop)->flags & EDGE_IRREDUCIBLE_LOOP;
1251 
1252   enum tree_code exit_cmp;
1253   tree enter_main_cond, exit_base, exit_step, exit_bound;
1254   determine_exit_conditions (loop, desc, factor,
1255 			     &enter_main_cond, &exit_base, &exit_step,
1256 			     &exit_cmp, &exit_bound);
1257   bool single_loop_p = !exit_base;
1258 
1259   /* Let us assume that the unrolled loop is quite likely to be entered.  */
1260   profile_probability prob_entry;
1261   if (integer_nonzerop (enter_main_cond))
1262     prob_entry = profile_probability::always ();
1263   else
1264     prob_entry = profile_probability::guessed_always ()
1265 			.apply_scale (PROB_UNROLLED_LOOP_ENTERED, 100);
1266 
1267   gcond *exit_if = nullptr;
1268   class loop *new_loop = nullptr;
1269   edge new_exit;
1270   if (!single_loop_p)
1271     {
1272       edge exit = single_dom_exit (loop);
1273 
1274       /* The values for scales should keep profile consistent, and somewhat
1275 	 close to correct.
1276 
1277 	 TODO: The current value of SCALE_REST makes it appear that the loop
1278 	 that is created by splitting the remaining iterations of the unrolled
1279 	 loop is executed the same number of times as the original loop, and
1280 	 with the same frequencies, which is obviously wrong.  This does not
1281 	 appear to cause problems, so we do not bother with fixing it for now.
1282 	 To make the profile correct, we would need to change the probability
1283 	 of the exit edge of the loop, and recompute the distribution of
1284 	 frequencies in its body because of this change (scale the frequencies
1285 	 of blocks before and after the exit by appropriate factors).  */
1286       profile_probability scale_unrolled = prob_entry;
1287       new_loop = loop_version (loop, enter_main_cond, NULL, prob_entry,
1288 			       prob_entry.invert (), scale_unrolled,
1289 			       profile_probability::guessed_always (),
1290 			       true);
1291       gcc_assert (new_loop != NULL);
1292       update_ssa (TODO_update_ssa);
1293 
1294       /* Prepare the cfg and update the phi nodes.  Move the loop exit to the
1295 	 loop latch (and make its condition dummy, for the moment).  */
1296       basic_block rest = loop_preheader_edge (new_loop)->src;
1297       edge precond_edge = single_pred_edge (rest);
1298       split_edge (loop_latch_edge (loop));
1299       basic_block exit_bb = single_pred (loop->latch);
1300 
1301       /* Since the exit edge will be removed, the frequency of all the blocks
1302 	 in the loop that are dominated by it must be scaled by
1303 	 1 / (1 - exit->probability).  */
1304       if (exit->probability.initialized_p ())
1305 	scale_dominated_blocks_in_loop (loop, exit->src,
1306 					/* We are scaling up here so
1307 					   probability does not fit.  */
1308 					loop->header->count,
1309 					loop->header->count
1310 					- loop->header->count.apply_probability
1311 					    (exit->probability));
1312 
1313       gimple_stmt_iterator bsi = gsi_last_bb (exit_bb);
1314       exit_if = gimple_build_cond (EQ_EXPR, integer_zero_node,
1315 				   integer_zero_node,
1316 				   NULL_TREE, NULL_TREE);
1317 
1318       gsi_insert_after (&bsi, exit_if, GSI_NEW_STMT);
1319       new_exit = make_edge (exit_bb, rest, EDGE_FALSE_VALUE | irr);
1320       rescan_loop_exit (new_exit, true, false);
1321 
1322       /* Set the probability of new exit to the same of the old one.  Fix
1323 	 the frequency of the latch block, by scaling it back by
1324 	 1 - exit->probability.  */
1325       new_exit->probability = exit->probability;
1326       edge new_nonexit = single_pred_edge (loop->latch);
1327       new_nonexit->probability = exit->probability.invert ();
1328       new_nonexit->flags = EDGE_TRUE_VALUE;
1329       if (new_nonexit->probability.initialized_p ())
1330 	scale_bbs_frequencies (&loop->latch, 1, new_nonexit->probability);
1331 
1332       edge old_entry = loop_preheader_edge (loop);
1333       edge new_entry = loop_preheader_edge (new_loop);
1334       edge old_latch = loop_latch_edge (loop);
1335       for (gphi_iterator psi_old_loop = gsi_start_phis (loop->header),
1336 	     psi_new_loop = gsi_start_phis (new_loop->header);
1337 	   !gsi_end_p (psi_old_loop);
1338 	   gsi_next (&psi_old_loop), gsi_next (&psi_new_loop))
1339 	{
1340 	  gphi *phi_old_loop = psi_old_loop.phi ();
1341 	  gphi *phi_new_loop = psi_new_loop.phi ();
1342 
1343 	  tree init = PHI_ARG_DEF_FROM_EDGE (phi_old_loop, old_entry);
1344 	  use_operand_p op
1345 	    = PHI_ARG_DEF_PTR_FROM_EDGE (phi_new_loop, new_entry);
1346 	  gcc_assert (operand_equal_for_phi_arg_p (init, USE_FROM_PTR (op)));
1347 	  tree next = PHI_ARG_DEF_FROM_EDGE (phi_old_loop, old_latch);
1348 
1349 	  /* Prefer using original variable as a base for the new ssa name.
1350 	     This is necessary for virtual ops, and useful in order to avoid
1351 	     losing debug info for real ops.  */
1352 	  tree new_init;
1353 	  if (TREE_CODE (next) == SSA_NAME
1354 	      && useless_type_conversion_p (TREE_TYPE (next),
1355 					    TREE_TYPE (init)))
1356 	    new_init = copy_ssa_name (next);
1357 	  else if (TREE_CODE (init) == SSA_NAME
1358 		   && useless_type_conversion_p (TREE_TYPE (init),
1359 						 TREE_TYPE (next)))
1360 	    new_init = copy_ssa_name (init);
1361 	  else if (useless_type_conversion_p (TREE_TYPE (next),
1362 					      TREE_TYPE (init)))
1363 	    new_init = make_temp_ssa_name (TREE_TYPE (next), NULL,
1364 					   "unrinittmp");
1365 	  else
1366 	    new_init = make_temp_ssa_name (TREE_TYPE (init), NULL,
1367 					   "unrinittmp");
1368 
1369 	  gphi *phi_rest = create_phi_node (new_init, rest);
1370 	  add_phi_arg (phi_rest, init, precond_edge, UNKNOWN_LOCATION);
1371 	  add_phi_arg (phi_rest, next, new_exit, UNKNOWN_LOCATION);
1372 	  SET_USE (op, new_init);
1373 	}
1374 
1375       remove_path (exit);
1376     }
1377   else
1378     new_exit = single_dom_exit (loop);
1379 
1380   /* Transform the loop.  */
1381   if (transform)
1382     (*transform) (loop, data);
1383 
1384   /* Unroll the loop and remove the exits in all iterations except for the
1385      last one.  */
1386   auto_sbitmap wont_exit (factor);
1387   bitmap_ones (wont_exit);
1388   bitmap_clear_bit (wont_exit, factor - 1);
1389 
1390   auto_vec<edge> to_remove;
1391   bool ok
1392     = gimple_duplicate_loop_body_to_header_edge (loop, loop_latch_edge (loop),
1393 						 factor - 1, wont_exit,
1394 						 new_exit, &to_remove,
1395 						 DLTHE_FLAG_UPDATE_FREQ);
1396   gcc_assert (ok);
1397 
1398   for (edge e : to_remove)
1399     {
1400       ok = remove_path (e);
1401       gcc_assert (ok);
1402     }
1403   update_ssa (TODO_update_ssa);
1404 
1405   new_exit = single_dom_exit (loop);
1406   if (!single_loop_p)
1407     {
1408       /* Ensure that the frequencies in the loop match the new estimated
1409 	 number of iterations, and change the probability of the new
1410 	 exit edge.  */
1411 
1412       profile_count freq_h = loop->header->count;
1413       profile_count freq_e = (loop_preheader_edge (loop))->count ();
1414       if (freq_h.nonzero_p ())
1415 	{
1416 	  /* Avoid dropping loop body profile counter to 0 because of zero
1417 	     count in loop's preheader.  */
1418 	  if (freq_h.nonzero_p () && !(freq_e == profile_count::zero ()))
1419 	    freq_e = freq_e.force_nonzero ();
1420 	  scale_loop_frequencies (loop, freq_e.probability_in (freq_h));
1421 	}
1422 
1423       basic_block rest = new_exit->dest;
1424       new_exit->probability = profile_probability::always ()
1425 	.apply_scale (1, new_est_niter + 1);
1426 
1427       rest->count += new_exit->count ();
1428 
1429       edge new_nonexit = single_pred_edge (loop->latch);
1430       profile_probability prob = new_nonexit->probability;
1431       new_nonexit->probability = new_exit->probability.invert ();
1432       prob = new_nonexit->probability / prob;
1433       if (prob.initialized_p ())
1434 	scale_bbs_frequencies (&loop->latch, 1, prob);
1435 
1436       /* Finally create the new counter for number of iterations and add
1437 	 the new exit instruction.  */
1438       tree ctr_before, ctr_after;
1439       gimple_stmt_iterator bsi = gsi_last_nondebug_bb (new_exit->src);
1440       exit_if = as_a <gcond *> (gsi_stmt (bsi));
1441       create_iv (exit_base, exit_step, NULL_TREE, loop,
1442 		 &bsi, false, &ctr_before, &ctr_after);
1443       gimple_cond_set_code (exit_if, exit_cmp);
1444       gimple_cond_set_lhs (exit_if, ctr_after);
1445       gimple_cond_set_rhs (exit_if, exit_bound);
1446       update_stmt (exit_if);
1447     }
1448   else
1449     {
1450       /* gimple_duplicate_loop_to_header_edge has adjusted the loop body's
1451 	 original profile counts in line with the unroll factor.  However,
1452 	 the old counts might not have been consistent with the old
1453 	 iteration count.
1454 
1455 	 Therefore, if the iteration count is known exactly, make sure that the
1456 	 profile counts of the loop header (and any other blocks that might be
1457 	 executed in the final iteration) are consistent with the combination
1458 	 of (a) the incoming profile count and (b) the new iteration count.  */
1459       profile_count in_count = loop_preheader_edge (loop)->count ();
1460       profile_count old_header_count = loop->header->count;
1461       if (in_count.nonzero_p ()
1462 	  && old_header_count.nonzero_p ()
1463 	  && TREE_CODE (desc->niter) == INTEGER_CST)
1464 	{
1465 	  /* The + 1 converts latch counts to iteration counts.  */
1466 	  profile_count new_header_count
1467 	    = (in_count.apply_scale (new_est_niter + 1, 1));
1468 	  basic_block *body = get_loop_body (loop);
1469 	  scale_bbs_frequencies_profile_count (body, loop->num_nodes,
1470 					       new_header_count,
1471 					       old_header_count);
1472 	  free (body);
1473 	}
1474 
1475       /* gimple_duplicate_loop_to_header_edge discarded FACTOR - 1
1476 	 exit edges and adjusted the loop body's profile counts for the
1477 	 new probabilities of the remaining non-exit edges.  However,
1478 	 the remaining exit edge still has the same probability as it
1479 	 did before, even though it is now more likely.
1480 
1481 	 Therefore, all blocks executed after a failed exit test now have
1482 	 a profile count that is too high, and the sum of the profile counts
1483 	 for the header's incoming edges is greater than the profile count
1484 	 of the header itself.
1485 
1486 	 Adjust the profile counts of all code in the loop body after
1487 	 the exit test so that the sum of the counts on entry to the
1488 	 header agree.  */
1489       profile_count old_latch_count = loop_latch_edge (loop)->count ();
1490       profile_count new_latch_count = loop->header->count - in_count;
1491       if (old_latch_count.nonzero_p () && new_latch_count.nonzero_p ())
1492 	scale_dominated_blocks_in_loop (loop, new_exit->src, new_latch_count,
1493 					old_latch_count);
1494 
1495       /* Set the probability of the exit edge based on NEW_EST_NITER
1496 	 (which estimates latch counts rather than iteration counts).
1497 	 Update the probabilities of other edges to match.
1498 
1499 	 If the profile counts are large enough to give the required
1500 	 precision, the updates above will have made
1501 
1502 	    e->dest->count / e->src->count ~= new e->probability
1503 
1504 	 for every outgoing edge e of NEW_EXIT->src.  */
1505       profile_probability new_exit_prob = profile_probability::always ()
1506 	.apply_scale (1, new_est_niter + 1);
1507       change_edge_frequency (new_exit, new_exit_prob);
1508     }
1509 
1510   checking_verify_flow_info ();
1511   checking_verify_loop_structure ();
1512   checking_verify_loop_closed_ssa (true, loop);
1513   checking_verify_loop_closed_ssa (true, new_loop);
1514 }
1515 
1516 /* Wrapper over tree_transform_and_unroll_loop for case we do not
1517    want to transform the loop before unrolling.  The meaning
1518    of the arguments is the same as for tree_transform_and_unroll_loop.  */
1519 
1520 void
tree_unroll_loop(class loop * loop,unsigned factor,class tree_niter_desc * desc)1521 tree_unroll_loop (class loop *loop, unsigned factor,
1522 		  class tree_niter_desc *desc)
1523 {
1524   tree_transform_and_unroll_loop (loop, factor, desc, NULL, NULL);
1525 }
1526 
1527 /* Rewrite the phi node at position PSI in function of the main
1528    induction variable MAIN_IV and insert the generated code at GSI.  */
1529 
1530 static void
rewrite_phi_with_iv(loop_p loop,gphi_iterator * psi,gimple_stmt_iterator * gsi,tree main_iv)1531 rewrite_phi_with_iv (loop_p loop,
1532 		     gphi_iterator *psi,
1533 		     gimple_stmt_iterator *gsi,
1534 		     tree main_iv)
1535 {
1536   affine_iv iv;
1537   gassign *stmt;
1538   gphi *phi = psi->phi ();
1539   tree atype, mtype, val, res = PHI_RESULT (phi);
1540 
1541   if (virtual_operand_p (res) || res == main_iv)
1542     {
1543       gsi_next (psi);
1544       return;
1545     }
1546 
1547   if (!simple_iv (loop, loop, res, &iv, true))
1548     {
1549       gsi_next (psi);
1550       return;
1551     }
1552 
1553   remove_phi_node (psi, false);
1554 
1555   atype = TREE_TYPE (res);
1556   mtype = POINTER_TYPE_P (atype) ? sizetype : atype;
1557   val = fold_build2 (MULT_EXPR, mtype, unshare_expr (iv.step),
1558 		     fold_convert (mtype, main_iv));
1559   val = fold_build2 (POINTER_TYPE_P (atype)
1560 		     ? POINTER_PLUS_EXPR : PLUS_EXPR,
1561 		     atype, unshare_expr (iv.base), val);
1562   val = force_gimple_operand_gsi (gsi, val, false, NULL_TREE, true,
1563 				  GSI_SAME_STMT);
1564   stmt = gimple_build_assign (res, val);
1565   gsi_insert_before (gsi, stmt, GSI_SAME_STMT);
1566 }
1567 
1568 /* Rewrite all the phi nodes of LOOP in function of the main induction
1569    variable MAIN_IV.  */
1570 
1571 static void
rewrite_all_phi_nodes_with_iv(loop_p loop,tree main_iv)1572 rewrite_all_phi_nodes_with_iv (loop_p loop, tree main_iv)
1573 {
1574   unsigned i;
1575   basic_block *bbs = get_loop_body_in_dom_order (loop);
1576   gphi_iterator psi;
1577 
1578   for (i = 0; i < loop->num_nodes; i++)
1579     {
1580       basic_block bb = bbs[i];
1581       gimple_stmt_iterator gsi = gsi_after_labels (bb);
1582 
1583       if (bb->loop_father != loop)
1584 	continue;
1585 
1586       for (psi = gsi_start_phis (bb); !gsi_end_p (psi); )
1587 	rewrite_phi_with_iv (loop, &psi, &gsi, main_iv);
1588     }
1589 
1590   free (bbs);
1591 }
1592 
1593 /* Bases all the induction variables in LOOP on a single induction variable
1594    (with base 0 and step 1), whose final value is compared with *NIT.  When the
1595    IV type precision has to be larger than *NIT type precision, *NIT is
1596    converted to the larger type, the conversion code is inserted before the
1597    loop, and *NIT is updated to the new definition.  When BUMP_IN_LATCH is true,
1598    the induction variable is incremented in the loop latch, otherwise it is
1599    incremented in the loop header.  Return the induction variable that was
1600    created.  */
1601 
1602 tree
canonicalize_loop_ivs(class loop * loop,tree * nit,bool bump_in_latch)1603 canonicalize_loop_ivs (class loop *loop, tree *nit, bool bump_in_latch)
1604 {
1605   unsigned precision = TYPE_PRECISION (TREE_TYPE (*nit));
1606   unsigned original_precision = precision;
1607   tree type, var_before;
1608   gimple_stmt_iterator gsi;
1609   gphi_iterator psi;
1610   gcond *stmt;
1611   edge exit = single_dom_exit (loop);
1612   gimple_seq stmts;
1613   bool unsigned_p = false;
1614 
1615   for (psi = gsi_start_phis (loop->header);
1616        !gsi_end_p (psi); gsi_next (&psi))
1617     {
1618       gphi *phi = psi.phi ();
1619       tree res = PHI_RESULT (phi);
1620       bool uns;
1621 
1622       type = TREE_TYPE (res);
1623       if (virtual_operand_p (res)
1624 	  || (!INTEGRAL_TYPE_P (type)
1625 	      && !POINTER_TYPE_P (type))
1626 	  || TYPE_PRECISION (type) < precision)
1627 	continue;
1628 
1629       uns = POINTER_TYPE_P (type) | TYPE_UNSIGNED (type);
1630 
1631       if (TYPE_PRECISION (type) > precision)
1632 	unsigned_p = uns;
1633       else
1634 	unsigned_p |= uns;
1635 
1636       precision = TYPE_PRECISION (type);
1637     }
1638 
1639   scalar_int_mode mode = smallest_int_mode_for_size (precision);
1640   precision = GET_MODE_PRECISION (mode);
1641   type = build_nonstandard_integer_type (precision, unsigned_p);
1642 
1643   if (original_precision != precision
1644       || TYPE_UNSIGNED (TREE_TYPE (*nit)) != unsigned_p)
1645     {
1646       *nit = fold_convert (type, *nit);
1647       *nit = force_gimple_operand (*nit, &stmts, true, NULL_TREE);
1648       if (stmts)
1649 	gsi_insert_seq_on_edge_immediate (loop_preheader_edge (loop), stmts);
1650     }
1651 
1652   if (bump_in_latch)
1653     gsi = gsi_last_bb (loop->latch);
1654   else
1655     gsi = gsi_last_nondebug_bb (loop->header);
1656   create_iv (build_int_cst_type (type, 0), build_int_cst (type, 1), NULL_TREE,
1657 	     loop, &gsi, bump_in_latch, &var_before, NULL);
1658 
1659   rewrite_all_phi_nodes_with_iv (loop, var_before);
1660 
1661   stmt = as_a <gcond *> (last_stmt (exit->src));
1662   /* Make the loop exit if the control condition is not satisfied.  */
1663   if (exit->flags & EDGE_TRUE_VALUE)
1664     {
1665       edge te, fe;
1666 
1667       extract_true_false_edges_from_block (exit->src, &te, &fe);
1668       te->flags = EDGE_FALSE_VALUE;
1669       fe->flags = EDGE_TRUE_VALUE;
1670     }
1671   gimple_cond_set_code (stmt, LT_EXPR);
1672   gimple_cond_set_lhs (stmt, var_before);
1673   gimple_cond_set_rhs (stmt, *nit);
1674   update_stmt (stmt);
1675 
1676   return var_before;
1677 }
1678