1 /* High-level loop manipulation functions.
2 Copyright (C) 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
4 This file is part of GCC.
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 2, or (at your option) any
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
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING. If not, write to the Free
18 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
23 #include "coretypes.h"
28 #include "hard-reg-set.h"
29 #include "basic-block.h"
31 #include "diagnostic.h"
32 #include "tree-flow.h"
33 #include "tree-dump.h"
36 #include "tree-pass.h"
37 #include "cfglayout.h"
38 #include "tree-scalar-evolution.h"
40 #include "tree-inline.h"
42 /* Creates an induction variable with value BASE + STEP * iteration in LOOP.
43 It is expected that neither BASE nor STEP are shared with other expressions
44 (unless the sharing rules allow this). Use VAR as a base var_decl for it
45 (if NULL, a new temporary will be created). The increment will occur at
46 INCR_POS (after it if AFTER is true, before it otherwise). INCR_POS and
47 AFTER can be computed using standard_iv_increment_position. The ssa versions
48 of the variable before and after increment will be stored in VAR_BEFORE and
49 VAR_AFTER (unless they are NULL). */
52 create_iv (tree base, tree step, tree var, struct loop *loop,
53 block_stmt_iterator *incr_pos, bool after,
54 tree *var_before, tree *var_after)
56 tree stmt, initial, step1, stmts;
58 enum tree_code incr_op = PLUS_EXPR;
59 edge pe = loop_preheader_edge (loop);
63 var = create_tmp_var (TREE_TYPE (base), "ivtmp");
64 add_referenced_var (var);
67 vb = make_ssa_name (var, NULL_TREE);
70 va = make_ssa_name (var, NULL_TREE);
74 /* For easier readability of the created code, produce MINUS_EXPRs
76 if (TREE_CODE (step) == INTEGER_CST)
78 if (TYPE_UNSIGNED (TREE_TYPE (step)))
80 step1 = fold_build1 (NEGATE_EXPR, TREE_TYPE (step), step);
81 if (tree_int_cst_lt (step1, step))
91 if (!tree_expr_nonnegative_warnv_p (step, &ovf)
92 && may_negate_without_overflow_p (step))
95 step = fold_build1 (NEGATE_EXPR, TREE_TYPE (step), step);
100 /* Gimplify the step if necessary. We put the computations in front of the
101 loop (i.e. the step should be loop invariant). */
102 step = force_gimple_operand (step, &stmts, true, var);
104 bsi_insert_on_edge_immediate (pe, stmts);
106 stmt = build_gimple_modify_stmt (va,
107 build2 (incr_op, TREE_TYPE (base),
109 SSA_NAME_DEF_STMT (va) = stmt;
111 bsi_insert_after (incr_pos, stmt, BSI_NEW_STMT);
113 bsi_insert_before (incr_pos, stmt, BSI_NEW_STMT);
115 initial = force_gimple_operand (base, &stmts, true, var);
117 bsi_insert_on_edge_immediate (pe, stmts);
119 stmt = create_phi_node (vb, loop->header);
120 SSA_NAME_DEF_STMT (vb) = stmt;
121 add_phi_arg (stmt, initial, loop_preheader_edge (loop));
122 add_phi_arg (stmt, va, loop_latch_edge (loop));
125 /* Add exit phis for the USE on EXIT. */
128 add_exit_phis_edge (basic_block exit, tree use)
130 tree phi, def_stmt = SSA_NAME_DEF_STMT (use);
131 basic_block def_bb = bb_for_stmt (def_stmt);
132 struct loop *def_loop;
136 /* Check that some of the edges entering the EXIT block exits a loop in
137 that USE is defined. */
138 FOR_EACH_EDGE (e, ei, exit->preds)
140 def_loop = find_common_loop (def_bb->loop_father, e->src->loop_father);
141 if (!flow_bb_inside_loop_p (def_loop, e->dest))
148 phi = create_phi_node (use, exit);
149 create_new_def_for (PHI_RESULT (phi), phi, PHI_RESULT_PTR (phi));
150 FOR_EACH_EDGE (e, ei, exit->preds)
151 add_phi_arg (phi, use, e);
154 /* Add exit phis for VAR that is used in LIVEIN.
155 Exits of the loops are stored in EXITS. */
158 add_exit_phis_var (tree var, bitmap livein, bitmap exits)
162 basic_block def_bb = bb_for_stmt (SSA_NAME_DEF_STMT (var));
165 if (is_gimple_reg (var))
166 bitmap_clear_bit (livein, def_bb->index);
168 bitmap_set_bit (livein, def_bb->index);
170 def = BITMAP_ALLOC (NULL);
171 bitmap_set_bit (def, def_bb->index);
172 compute_global_livein (livein, def);
175 EXECUTE_IF_AND_IN_BITMAP (exits, livein, 0, index, bi)
177 add_exit_phis_edge (BASIC_BLOCK (index), var);
181 /* Add exit phis for the names marked in NAMES_TO_RENAME.
182 Exits of the loops are stored in EXITS. Sets of blocks where the ssa
183 names are used are stored in USE_BLOCKS. */
186 add_exit_phis (bitmap names_to_rename, bitmap *use_blocks, bitmap loop_exits)
191 EXECUTE_IF_SET_IN_BITMAP (names_to_rename, 0, i, bi)
193 add_exit_phis_var (ssa_name (i), use_blocks[i], loop_exits);
197 /* Returns a bitmap of all loop exit edge targets. */
200 get_loops_exits (void)
202 bitmap exits = BITMAP_ALLOC (NULL);
209 FOR_EACH_EDGE (e, ei, bb->preds)
210 if (e->src != ENTRY_BLOCK_PTR
211 && !flow_bb_inside_loop_p (e->src->loop_father, bb))
213 bitmap_set_bit (exits, bb->index);
221 /* For USE in BB, if it is used outside of the loop it is defined in,
222 mark it for rewrite. Record basic block BB where it is used
223 to USE_BLOCKS. Record the ssa name index to NEED_PHIS bitmap. */
226 find_uses_to_rename_use (basic_block bb, tree use, bitmap *use_blocks,
231 struct loop *def_loop;
233 if (TREE_CODE (use) != SSA_NAME)
236 /* We don't need to keep virtual operands in loop-closed form. */
237 if (!is_gimple_reg (use))
240 ver = SSA_NAME_VERSION (use);
241 def_bb = bb_for_stmt (SSA_NAME_DEF_STMT (use));
244 def_loop = def_bb->loop_father;
246 /* If the definition is not inside loop, it is not interesting. */
247 if (!def_loop->outer)
250 if (!use_blocks[ver])
251 use_blocks[ver] = BITMAP_ALLOC (NULL);
252 bitmap_set_bit (use_blocks[ver], bb->index);
254 bitmap_set_bit (need_phis, ver);
257 /* For uses in STMT, mark names that are used outside of the loop they are
258 defined to rewrite. Record the set of blocks in that the ssa
259 names are defined to USE_BLOCKS and the ssa names themselves to
263 find_uses_to_rename_stmt (tree stmt, bitmap *use_blocks, bitmap need_phis)
267 basic_block bb = bb_for_stmt (stmt);
269 FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, SSA_OP_ALL_USES)
270 find_uses_to_rename_use (bb, var, use_blocks, need_phis);
273 /* Marks names that are used in BB and outside of the loop they are
274 defined in for rewrite. Records the set of blocks in that the ssa
275 names are defined to USE_BLOCKS. Record the SSA names that will
276 need exit PHIs in NEED_PHIS. */
279 find_uses_to_rename_bb (basic_block bb, bitmap *use_blocks, bitmap need_phis)
281 block_stmt_iterator bsi;
286 FOR_EACH_EDGE (e, ei, bb->succs)
287 for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
288 find_uses_to_rename_use (bb, PHI_ARG_DEF_FROM_EDGE (phi, e),
289 use_blocks, need_phis);
291 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
292 find_uses_to_rename_stmt (bsi_stmt (bsi), use_blocks, need_phis);
295 /* Marks names that are used outside of the loop they are defined in
296 for rewrite. Records the set of blocks in that the ssa
297 names are defined to USE_BLOCKS. If CHANGED_BBS is not NULL,
298 scan only blocks in this set. */
301 find_uses_to_rename (bitmap changed_bbs, bitmap *use_blocks, bitmap need_phis)
307 if (changed_bbs && !bitmap_empty_p (changed_bbs))
309 EXECUTE_IF_SET_IN_BITMAP (changed_bbs, 0, index, bi)
311 find_uses_to_rename_bb (BASIC_BLOCK (index), use_blocks, need_phis);
318 find_uses_to_rename_bb (bb, use_blocks, need_phis);
323 /* Rewrites the program into a loop closed ssa form -- i.e. inserts extra
324 phi nodes to ensure that no variable is used outside the loop it is
327 This strengthening of the basic ssa form has several advantages:
329 1) Updating it during unrolling/peeling/versioning is trivial, since
330 we do not need to care about the uses outside of the loop.
331 2) The behavior of all uses of an induction variable is the same.
332 Without this, you need to distinguish the case when the variable
333 is used outside of the loop it is defined in, for example
335 for (i = 0; i < 100; i++)
337 for (j = 0; j < 100; j++)
345 Looking from the outer loop with the normal SSA form, the first use of k
346 is not well-behaved, while the second one is an induction variable with
349 If CHANGED_BBS is not NULL, we look for uses outside loops only in
350 the basic blocks in this set.
352 UPDATE_FLAG is used in the call to update_ssa. See
353 TODO_update_ssa* for documentation. */
356 rewrite_into_loop_closed_ssa (bitmap changed_bbs, unsigned update_flag)
360 unsigned i, old_num_ssa_names;
361 bitmap names_to_rename;
366 loop_exits = get_loops_exits ();
367 names_to_rename = BITMAP_ALLOC (NULL);
369 /* If the pass has caused the SSA form to be out-of-date, update it
371 update_ssa (update_flag);
373 old_num_ssa_names = num_ssa_names;
374 use_blocks = XCNEWVEC (bitmap, old_num_ssa_names);
376 /* Find the uses outside loops. */
377 find_uses_to_rename (changed_bbs, use_blocks, names_to_rename);
379 /* Add the PHI nodes on exits of the loops for the names we need to
381 add_exit_phis (names_to_rename, use_blocks, loop_exits);
383 for (i = 0; i < old_num_ssa_names; i++)
384 BITMAP_FREE (use_blocks[i]);
386 BITMAP_FREE (loop_exits);
387 BITMAP_FREE (names_to_rename);
389 /* Fix up all the names found to be used outside their original
391 update_ssa (TODO_update_ssa);
393 current_loops->state |= LOOP_CLOSED_SSA;
396 /* Check invariants of the loop closed ssa form for the USE in BB. */
399 check_loop_closed_ssa_use (basic_block bb, tree use)
404 if (TREE_CODE (use) != SSA_NAME || !is_gimple_reg (use))
407 def = SSA_NAME_DEF_STMT (use);
408 def_bb = bb_for_stmt (def);
410 || flow_bb_inside_loop_p (def_bb->loop_father, bb));
413 /* Checks invariants of loop closed ssa form in statement STMT in BB. */
416 check_loop_closed_ssa_stmt (basic_block bb, tree stmt)
421 FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, SSA_OP_ALL_USES)
422 check_loop_closed_ssa_use (bb, var);
425 /* Checks that invariants of the loop closed ssa form are preserved. */
428 verify_loop_closed_ssa (void)
431 block_stmt_iterator bsi;
435 if (current_loops == NULL)
442 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
443 for (i = 0; i < (unsigned) PHI_NUM_ARGS (phi); i++)
444 check_loop_closed_ssa_use (PHI_ARG_EDGE (phi, i)->src,
445 PHI_ARG_DEF (phi, i));
447 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
448 check_loop_closed_ssa_stmt (bb, bsi_stmt (bsi));
452 /* Split loop exit edge EXIT. The things are a bit complicated by a need to
453 preserve the loop closed ssa form. */
456 split_loop_exit_edge (edge exit)
458 basic_block dest = exit->dest;
459 basic_block bb = split_edge (exit);
460 tree phi, new_phi, new_name, name;
463 for (phi = phi_nodes (dest); phi; phi = PHI_CHAIN (phi))
465 op_p = PHI_ARG_DEF_PTR_FROM_EDGE (phi, single_succ_edge (bb));
467 name = USE_FROM_PTR (op_p);
469 /* If the argument of the PHI node is a constant, we do not need
470 to keep it inside loop. */
471 if (TREE_CODE (name) != SSA_NAME)
474 /* Otherwise create an auxiliary phi node that will copy the value
475 of the SSA name out of the loop. */
476 new_name = duplicate_ssa_name (name, NULL);
477 new_phi = create_phi_node (new_name, bb);
478 SSA_NAME_DEF_STMT (new_name) = new_phi;
479 add_phi_arg (new_phi, name, exit);
480 SET_USE (op_p, new_name);
484 /* Returns the basic block in that statements should be emitted for induction
485 variables incremented at the end of the LOOP. */
488 ip_end_pos (struct loop *loop)
493 /* Returns the basic block in that statements should be emitted for induction
494 variables incremented just before exit condition of a LOOP. */
497 ip_normal_pos (struct loop *loop)
503 if (!single_pred_p (loop->latch))
506 bb = single_pred (loop->latch);
507 last = last_stmt (bb);
508 if (TREE_CODE (last) != COND_EXPR)
511 exit = EDGE_SUCC (bb, 0);
512 if (exit->dest == loop->latch)
513 exit = EDGE_SUCC (bb, 1);
515 if (flow_bb_inside_loop_p (loop, exit->dest))
521 /* Stores the standard position for induction variable increment in LOOP
522 (just before the exit condition if it is available and latch block is empty,
523 end of the latch block otherwise) to BSI. INSERT_AFTER is set to true if
524 the increment should be inserted after *BSI. */
527 standard_iv_increment_position (struct loop *loop, block_stmt_iterator *bsi,
530 basic_block bb = ip_normal_pos (loop), latch = ip_end_pos (loop);
531 tree last = last_stmt (latch);
534 || (last && TREE_CODE (last) != LABEL_EXPR))
536 *bsi = bsi_last (latch);
537 *insert_after = true;
541 *bsi = bsi_last (bb);
542 *insert_after = false;
546 /* Copies phi node arguments for duplicated blocks. The index of the first
547 duplicated block is FIRST_NEW_BLOCK. */
550 copy_phi_node_args (unsigned first_new_block)
554 for (i = first_new_block; i < (unsigned) last_basic_block; i++)
555 BASIC_BLOCK (i)->flags |= BB_DUPLICATED;
557 for (i = first_new_block; i < (unsigned) last_basic_block; i++)
558 add_phi_args_after_copy_bb (BASIC_BLOCK (i));
560 for (i = first_new_block; i < (unsigned) last_basic_block; i++)
561 BASIC_BLOCK (i)->flags &= ~BB_DUPLICATED;
565 /* The same as cfgloopmanip.c:duplicate_loop_to_header_edge, but also
566 updates the PHI nodes at start of the copied region. In order to
567 achieve this, only loops whose exits all lead to the same location
570 Notice that we do not completely update the SSA web after
571 duplication. The caller is responsible for calling update_ssa
572 after the loop has been duplicated. */
575 tree_duplicate_loop_to_header_edge (struct loop *loop, edge e,
576 unsigned int ndupl, sbitmap wont_exit,
577 edge orig, VEC (edge, heap) **to_remove,
580 unsigned first_new_block;
582 if (!(current_loops->state & LOOPS_HAVE_SIMPLE_LATCHES))
584 if (!(current_loops->state & LOOPS_HAVE_PREHEADERS))
587 #ifdef ENABLE_CHECKING
588 verify_loop_closed_ssa ();
591 first_new_block = last_basic_block;
592 if (!duplicate_loop_to_header_edge (loop, e, ndupl, wont_exit,
593 orig, to_remove, flags))
596 /* Readd the removed phi args for e. */
597 flush_pending_stmts (e);
599 /* Copy the phi node arguments. */
600 copy_phi_node_args (first_new_block);
607 /* Build if (COND) goto THEN_LABEL; else goto ELSE_LABEL; */
610 build_if_stmt (tree cond, tree then_label, tree else_label)
612 return build3 (COND_EXPR, void_type_node,
614 build1 (GOTO_EXPR, void_type_node, then_label),
615 build1 (GOTO_EXPR, void_type_node, else_label));
618 /* Returns true if we can unroll LOOP FACTOR times. Number
619 of iterations of the loop is returned in NITER. */
622 can_unroll_loop_p (struct loop *loop, unsigned factor,
623 struct tree_niter_desc *niter)
627 /* Check whether unrolling is possible. We only want to unroll loops
628 for that we are able to determine number of iterations. We also
629 want to split the extra iterations of the loop from its end,
630 therefore we require that the loop has precisely one
633 exit = single_dom_exit (loop);
637 if (!number_of_iterations_exit (loop, exit, niter, false)
638 || niter->cmp == ERROR_MARK
639 /* Scalar evolutions analysis might have copy propagated
640 the abnormal ssa names into these expressions, hence
641 emitting the computations based on them during loop
642 unrolling might create overlapping life ranges for
643 them, and failures in out-of-ssa. */
644 || contains_abnormal_ssa_name_p (niter->may_be_zero)
645 || contains_abnormal_ssa_name_p (niter->control.base)
646 || contains_abnormal_ssa_name_p (niter->control.step)
647 || contains_abnormal_ssa_name_p (niter->bound))
650 /* And of course, we must be able to duplicate the loop. */
651 if (!can_duplicate_loop_p (loop))
654 /* The final loop should be small enough. */
655 if (tree_num_loop_insns (loop, &eni_size_weights) * factor
656 > (unsigned) PARAM_VALUE (PARAM_MAX_UNROLLED_INSNS))
662 /* Determines the conditions that control execution of LOOP unrolled FACTOR
663 times. DESC is number of iterations of LOOP. ENTER_COND is set to
664 condition that must be true if the main loop can be entered.
665 EXIT_BASE, EXIT_STEP, EXIT_CMP and EXIT_BOUND are set to values describing
666 how the exit from the unrolled loop should be controlled. */
669 determine_exit_conditions (struct loop *loop, struct tree_niter_desc *desc,
670 unsigned factor, tree *enter_cond,
671 tree *exit_base, tree *exit_step,
672 enum tree_code *exit_cmp, tree *exit_bound)
675 tree base = desc->control.base;
676 tree step = desc->control.step;
677 tree bound = desc->bound;
678 tree type = TREE_TYPE (base);
680 tree min = lower_bound_in_type (type, type);
681 tree max = upper_bound_in_type (type, type);
682 enum tree_code cmp = desc->cmp;
683 tree cond = boolean_true_node, assum;
685 *enter_cond = boolean_false_node;
686 *exit_base = NULL_TREE;
687 *exit_step = NULL_TREE;
688 *exit_cmp = ERROR_MARK;
689 *exit_bound = NULL_TREE;
690 gcc_assert (cmp != ERROR_MARK);
692 /* We only need to be correct when we answer question
693 "Do at least FACTOR more iterations remain?" in the unrolled loop.
694 Thus, transforming BASE + STEP * i <> BOUND to
695 BASE + STEP * i < BOUND is ok. */
698 if (tree_int_cst_sign_bit (step))
703 else if (cmp == LT_EXPR)
705 gcc_assert (!tree_int_cst_sign_bit (step));
707 else if (cmp == GT_EXPR)
709 gcc_assert (tree_int_cst_sign_bit (step));
714 /* The main body of the loop may be entered iff:
716 1) desc->may_be_zero is false.
717 2) it is possible to check that there are at least FACTOR iterations
718 of the loop, i.e., BOUND - step * FACTOR does not overflow.
719 3) # of iterations is at least FACTOR */
721 if (!integer_zerop (desc->may_be_zero))
722 cond = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
723 invert_truthvalue (desc->may_be_zero),
726 bigstep = fold_build2 (MULT_EXPR, type, step,
727 build_int_cst_type (type, factor));
728 delta = fold_build2 (MINUS_EXPR, type, bigstep, step);
730 assum = fold_build2 (GE_EXPR, boolean_type_node,
732 fold_build2 (PLUS_EXPR, type, min, delta));
734 assum = fold_build2 (LE_EXPR, boolean_type_node,
736 fold_build2 (PLUS_EXPR, type, max, delta));
737 cond = fold_build2 (TRUTH_AND_EXPR, boolean_type_node, assum, cond);
739 bound = fold_build2 (MINUS_EXPR, type, bound, delta);
740 assum = fold_build2 (cmp, boolean_type_node, base, bound);
741 cond = fold_build2 (TRUTH_AND_EXPR, boolean_type_node, assum, cond);
743 cond = force_gimple_operand (unshare_expr (cond), &stmts, false, NULL_TREE);
745 bsi_insert_on_edge_immediate (loop_preheader_edge (loop), stmts);
746 /* cond now may be a gimple comparison, which would be OK, but also any
747 other gimple rhs (say a && b). In this case we need to force it to
749 if (!is_gimple_condexpr (cond))
751 cond = force_gimple_operand (cond, &stmts, true, NULL_TREE);
753 bsi_insert_on_edge_immediate (loop_preheader_edge (loop), stmts);
757 base = force_gimple_operand (unshare_expr (base), &stmts, true, NULL_TREE);
759 bsi_insert_on_edge_immediate (loop_preheader_edge (loop), stmts);
760 bound = force_gimple_operand (unshare_expr (bound), &stmts, true, NULL_TREE);
762 bsi_insert_on_edge_immediate (loop_preheader_edge (loop), stmts);
765 *exit_step = bigstep;
770 /* Scales the frequencies of all basic blocks in LOOP that are strictly
771 dominated by BB by NUM/DEN. */
774 scale_dominated_blocks_in_loop (struct loop *loop, basic_block bb,
782 for (son = first_dom_son (CDI_DOMINATORS, bb);
784 son = next_dom_son (CDI_DOMINATORS, son))
786 if (!flow_bb_inside_loop_p (loop, son))
788 scale_bbs_frequencies_int (&son, 1, num, den);
789 scale_dominated_blocks_in_loop (loop, son, num, den);
793 /* Unroll LOOP FACTOR times. DESC describes number of iterations of LOOP.
794 EXIT is the exit of the loop to that DESC corresponds.
796 If N is number of iterations of the loop and MAY_BE_ZERO is the condition
797 under that loop exits in the first iteration even if N != 0,
801 x = phi (init, next);
809 becomes (with possibly the exit conditions formulated a bit differently,
810 avoiding the need to create a new iv):
812 if (MAY_BE_ZERO || N < FACTOR)
817 x = phi (init, next);
828 } while (N >= FACTOR);
831 init' = phi (init, x);
835 x = phi (init', next);
843 Before the loop is unrolled, TRANSFORM is called for it (only for the
844 unrolled loop, but not for its versioned copy). DATA is passed to
847 /* Probability in % that the unrolled loop is entered. Just a guess. */
848 #define PROB_UNROLLED_LOOP_ENTERED 90
851 tree_transform_and_unroll_loop (struct loop *loop, unsigned factor,
852 edge exit, struct tree_niter_desc *desc,
853 transform_callback transform,
856 tree exit_if, ctr_before, ctr_after;
857 tree enter_main_cond, exit_base, exit_step, exit_bound;
858 enum tree_code exit_cmp;
859 tree phi_old_loop, phi_new_loop, phi_rest, init, next, new_init, var;
860 struct loop *new_loop;
861 basic_block rest, exit_bb;
862 edge old_entry, new_entry, old_latch, precond_edge, new_exit;
864 block_stmt_iterator bsi;
867 unsigned est_niter, prob_entry, scale_unrolled, scale_rest, freq_e, freq_h;
868 unsigned new_est_niter, i, prob;
869 unsigned irr = loop_preheader_edge (loop)->flags & EDGE_IRREDUCIBLE_LOOP;
871 VEC (edge, heap) *to_remove = NULL;
873 est_niter = expected_loop_iterations (loop);
874 determine_exit_conditions (loop, desc, factor,
875 &enter_main_cond, &exit_base, &exit_step,
876 &exit_cmp, &exit_bound);
878 /* Let us assume that the unrolled loop is quite likely to be entered. */
879 if (integer_nonzerop (enter_main_cond))
880 prob_entry = REG_BR_PROB_BASE;
882 prob_entry = PROB_UNROLLED_LOOP_ENTERED * REG_BR_PROB_BASE / 100;
884 /* The values for scales should keep profile consistent, and somewhat close
887 TODO: The current value of SCALE_REST makes it appear that the loop that
888 is created by splitting the remaining iterations of the unrolled loop is
889 executed the same number of times as the original loop, and with the same
890 frequencies, which is obviously wrong. This does not appear to cause
891 problems, so we do not bother with fixing it for now. To make the profile
892 correct, we would need to change the probability of the exit edge of the
893 loop, and recompute the distribution of frequencies in its body because
894 of this change (scale the frequencies of blocks before and after the exit
895 by appropriate factors). */
896 scale_unrolled = prob_entry;
897 scale_rest = REG_BR_PROB_BASE;
899 new_loop = loop_version (loop, enter_main_cond, NULL,
900 prob_entry, scale_unrolled, scale_rest, true);
901 gcc_assert (new_loop != NULL);
902 update_ssa (TODO_update_ssa);
904 /* Determine the probability of the exit edge of the unrolled loop. */
905 new_est_niter = est_niter / factor;
907 /* Without profile feedback, loops for that we do not know a better estimate
908 are assumed to roll 10 times. When we unroll such loop, it appears to
909 roll too little, and it may even seem to be cold. To avoid this, we
910 ensure that the created loop appears to roll at least 5 times (but at
911 most as many times as before unrolling). */
912 if (new_est_niter < 5)
915 new_est_niter = est_niter;
920 /* Prepare the cfg and update the phi nodes. Move the loop exit to the
921 loop latch (and make its condition dummy, for the moment). */
922 rest = loop_preheader_edge (new_loop)->src;
923 precond_edge = single_pred_edge (rest);
924 split_edge (loop_latch_edge (loop));
925 exit_bb = single_pred (loop->latch);
927 /* Since the exit edge will be removed, the frequency of all the blocks
928 in the loop that are dominated by it must be scaled by
929 1 / (1 - exit->probability). */
930 scale_dominated_blocks_in_loop (loop, exit->src,
932 REG_BR_PROB_BASE - exit->probability);
934 bsi = bsi_last (exit_bb);
935 exit_if = build_if_stmt (boolean_true_node,
936 tree_block_label (loop->latch),
937 tree_block_label (rest));
938 bsi_insert_after (&bsi, exit_if, BSI_NEW_STMT);
939 new_exit = make_edge (exit_bb, rest, EDGE_FALSE_VALUE | irr);
940 rescan_loop_exit (new_exit, true, false);
942 /* Set the probability of new exit to the same of the old one. Fix
943 the frequency of the latch block, by scaling it back by
944 1 - exit->probability. */
945 new_exit->count = exit->count;
946 new_exit->probability = exit->probability;
947 new_nonexit = single_pred_edge (loop->latch);
948 new_nonexit->probability = REG_BR_PROB_BASE - exit->probability;
949 new_nonexit->flags = EDGE_TRUE_VALUE;
950 new_nonexit->count -= exit->count;
951 if (new_nonexit->count < 0)
952 new_nonexit->count = 0;
953 scale_bbs_frequencies_int (&loop->latch, 1, new_nonexit->probability,
956 old_entry = loop_preheader_edge (loop);
957 new_entry = loop_preheader_edge (new_loop);
958 old_latch = loop_latch_edge (loop);
959 for (phi_old_loop = phi_nodes (loop->header),
960 phi_new_loop = phi_nodes (new_loop->header);
962 phi_old_loop = PHI_CHAIN (phi_old_loop),
963 phi_new_loop = PHI_CHAIN (phi_new_loop))
965 init = PHI_ARG_DEF_FROM_EDGE (phi_old_loop, old_entry);
966 op = PHI_ARG_DEF_PTR_FROM_EDGE (phi_new_loop, new_entry);
967 gcc_assert (operand_equal_for_phi_arg_p (init, USE_FROM_PTR (op)));
968 next = PHI_ARG_DEF_FROM_EDGE (phi_old_loop, old_latch);
970 /* Prefer using original variable as a base for the new ssa name.
971 This is necessary for virtual ops, and useful in order to avoid
972 losing debug info for real ops. */
973 if (TREE_CODE (next) == SSA_NAME)
974 var = SSA_NAME_VAR (next);
975 else if (TREE_CODE (init) == SSA_NAME)
976 var = SSA_NAME_VAR (init);
979 var = create_tmp_var (TREE_TYPE (init), "unrinittmp");
980 add_referenced_var (var);
983 new_init = make_ssa_name (var, NULL_TREE);
984 phi_rest = create_phi_node (new_init, rest);
985 SSA_NAME_DEF_STMT (new_init) = phi_rest;
987 add_phi_arg (phi_rest, init, precond_edge);
988 add_phi_arg (phi_rest, next, new_exit);
989 SET_USE (op, new_init);
994 /* Transform the loop. */
996 (*transform) (loop, data);
998 /* Unroll the loop and remove the exits in all iterations except for the
1000 wont_exit = sbitmap_alloc (factor);
1001 sbitmap_ones (wont_exit);
1002 RESET_BIT (wont_exit, factor - 1);
1004 ok = tree_duplicate_loop_to_header_edge
1005 (loop, loop_latch_edge (loop), factor - 1,
1006 wont_exit, new_exit, &to_remove, DLTHE_FLAG_UPDATE_FREQ);
1010 for (i = 0; VEC_iterate (edge, to_remove, i, e); i++)
1012 ok = remove_path (e);
1015 VEC_free (edge, heap, to_remove);
1016 update_ssa (TODO_update_ssa);
1018 /* Ensure that the frequencies in the loop match the new estimated
1019 number of iterations, and change the probability of the new
1021 freq_h = loop->header->frequency;
1022 freq_e = EDGE_FREQUENCY (loop_preheader_edge (loop));
1024 scale_loop_frequencies (loop, freq_e * (new_est_niter + 1), freq_h);
1026 exit_bb = single_pred (loop->latch);
1027 new_exit = find_edge (exit_bb, rest);
1028 new_exit->count = loop_preheader_edge (loop)->count;
1029 new_exit->probability = REG_BR_PROB_BASE / (new_est_niter + 1);
1031 rest->count += new_exit->count;
1032 rest->frequency += EDGE_FREQUENCY (new_exit);
1034 new_nonexit = single_pred_edge (loop->latch);
1035 prob = new_nonexit->probability;
1036 new_nonexit->probability = REG_BR_PROB_BASE - new_exit->probability;
1037 new_nonexit->count = exit_bb->count - new_exit->count;
1038 if (new_nonexit->count < 0)
1039 new_nonexit->count = 0;
1040 scale_bbs_frequencies_int (&loop->latch, 1, new_nonexit->probability,
1043 /* Finally create the new counter for number of iterations and add the new
1044 exit instruction. */
1045 bsi = bsi_last (exit_bb);
1046 exit_if = bsi_stmt (bsi);
1047 create_iv (exit_base, exit_step, NULL_TREE, loop,
1048 &bsi, false, &ctr_before, &ctr_after);
1049 COND_EXPR_COND (exit_if) = build2 (exit_cmp, boolean_type_node, ctr_after,
1051 update_stmt (exit_if);
1053 #ifdef ENABLE_CHECKING
1054 verify_flow_info ();
1055 verify_dominators (CDI_DOMINATORS);
1056 verify_loop_structure ();
1057 verify_loop_closed_ssa ();
1061 /* Wrapper over tree_transform_and_unroll_loop for case we do not
1062 want to transform the loop before unrolling. The meaning
1063 of the arguments is the same as for tree_transform_and_unroll_loop. */
1066 tree_unroll_loop (struct loop *loop, unsigned factor,
1067 edge exit, struct tree_niter_desc *desc)
1069 tree_transform_and_unroll_loop (loop, factor, exit, desc,