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Diffstat (limited to 'gcc-4.9/gcc/tree-ssa-loop-ivcanon.c')
-rw-r--r-- | gcc-4.9/gcc/tree-ssa-loop-ivcanon.c | 1434 |
1 files changed, 1434 insertions, 0 deletions
diff --git a/gcc-4.9/gcc/tree-ssa-loop-ivcanon.c b/gcc-4.9/gcc/tree-ssa-loop-ivcanon.c new file mode 100644 index 000000000..b475b067b --- /dev/null +++ b/gcc-4.9/gcc/tree-ssa-loop-ivcanon.c @@ -0,0 +1,1434 @@ +/* Induction variable canonicalization and loop peeling. + Copyright (C) 2004-2014 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/>. */ + +/* This pass detects the loops that iterate a constant number of times, + adds a canonical induction variable (step -1, tested against 0) + and replaces the exit test. This enables the less powerful rtl + level analysis to use this information. + + This might spoil the code in some cases (by increasing register pressure). + Note that in the case the new variable is not needed, ivopts will get rid + of it, so it might only be a problem when there are no other linear induction + variables. In that case the created optimization possibilities are likely + to pay up. + + Additionally in case we detect that it is beneficial to unroll the + loop completely, we do it right here to expose the optimization + possibilities to the following passes. */ + +#include "config.h" +#include "system.h" +#include "coretypes.h" +#include "tm.h" +#include "tree.h" +#include "tm_p.h" +#include "basic-block.h" +#include "gimple-pretty-print.h" +#include "tree-ssa-alias.h" +#include "internal-fn.h" +#include "gimple-fold.h" +#include "tree-eh.h" +#include "gimple-expr.h" +#include "is-a.h" +#include "gimple.h" +#include "gimple-iterator.h" +#include "gimple-ssa.h" +#include "cgraph.h" +#include "tree-cfg.h" +#include "tree-phinodes.h" +#include "ssa-iterators.h" +#include "stringpool.h" +#include "tree-ssanames.h" +#include "tree-ssa-loop-manip.h" +#include "tree-ssa-loop-niter.h" +#include "tree-ssa-loop.h" +#include "tree-into-ssa.h" +#include "cfgloop.h" +#include "tree-pass.h" +#include "tree-chrec.h" +#include "tree-scalar-evolution.h" +#include "params.h" +#include "flags.h" +#include "tree-inline.h" +#include "target.h" +#include "tree-cfgcleanup.h" + +/* Specifies types of loops that may be unrolled. */ + +enum unroll_level +{ + UL_SINGLE_ITER, /* Only loops that exit immediately in the first + iteration. */ + UL_NO_GROWTH, /* Only loops whose unrolling will not cause increase + of code size. */ + UL_ALL /* All suitable loops. */ +}; + +/* Adds a canonical induction variable to LOOP iterating NITER times. EXIT + is the exit edge whose condition is replaced. */ + +static void +create_canonical_iv (struct loop *loop, edge exit, tree niter) +{ + edge in; + tree type, var; + gimple cond; + gimple_stmt_iterator incr_at; + enum tree_code cmp; + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "Added canonical iv to loop %d, ", loop->num); + print_generic_expr (dump_file, niter, TDF_SLIM); + fprintf (dump_file, " iterations.\n"); + } + + cond = last_stmt (exit->src); + in = EDGE_SUCC (exit->src, 0); + if (in == exit) + in = EDGE_SUCC (exit->src, 1); + + /* Note that we do not need to worry about overflows, since + type of niter is always unsigned and all comparisons are + just for equality/nonequality -- i.e. everything works + with a modulo arithmetics. */ + + type = TREE_TYPE (niter); + niter = fold_build2 (PLUS_EXPR, type, + niter, + build_int_cst (type, 1)); + incr_at = gsi_last_bb (in->src); + create_iv (niter, + build_int_cst (type, -1), + NULL_TREE, loop, + &incr_at, false, NULL, &var); + + cmp = (exit->flags & EDGE_TRUE_VALUE) ? EQ_EXPR : NE_EXPR; + gimple_cond_set_code (cond, cmp); + gimple_cond_set_lhs (cond, var); + gimple_cond_set_rhs (cond, build_int_cst (type, 0)); + update_stmt (cond); +} + +/* Describe size of loop as detected by tree_estimate_loop_size. */ +struct loop_size +{ + /* Number of instructions in the loop. */ + int overall; + + /* Number of instructions that will be likely optimized out in + peeled iterations of loop (i.e. computation based on induction + variable where induction variable starts at known constant.) */ + int eliminated_by_peeling; + + /* Same statistics for last iteration of loop: it is smaller because + instructions after exit are not executed. */ + int last_iteration; + int last_iteration_eliminated_by_peeling; + + /* If some IV computation will become constant. */ + bool constant_iv; + + /* Number of call stmts that are not a builtin and are pure or const + present on the hot path. */ + int num_pure_calls_on_hot_path; + /* Number of call stmts that are not a builtin and are not pure nor const + present on the hot path. */ + int num_non_pure_calls_on_hot_path; + /* Number of statements other than calls in the loop. */ + int non_call_stmts_on_hot_path; + /* Number of branches seen on the hot path. */ + int num_branches_on_hot_path; +}; + +/* Return true if OP in STMT will be constant after peeling LOOP. */ + +static bool +constant_after_peeling (tree op, gimple stmt, struct loop *loop) +{ + affine_iv iv; + + if (is_gimple_min_invariant (op)) + return true; + + /* We can still fold accesses to constant arrays when index is known. */ + if (TREE_CODE (op) != SSA_NAME) + { + tree base = op; + + /* First make fast look if we see constant array inside. */ + while (handled_component_p (base)) + base = TREE_OPERAND (base, 0); + if ((DECL_P (base) + && ctor_for_folding (base) != error_mark_node) + || CONSTANT_CLASS_P (base)) + { + /* If so, see if we understand all the indices. */ + base = op; + while (handled_component_p (base)) + { + if (TREE_CODE (base) == ARRAY_REF + && !constant_after_peeling (TREE_OPERAND (base, 1), stmt, loop)) + return false; + base = TREE_OPERAND (base, 0); + } + return true; + } + return false; + } + + /* Induction variables are constants. */ + if (!simple_iv (loop, loop_containing_stmt (stmt), op, &iv, false)) + return false; + if (!is_gimple_min_invariant (iv.base)) + return false; + if (!is_gimple_min_invariant (iv.step)) + return false; + return true; +} + +/* Computes an estimated number of insns in LOOP. + EXIT (if non-NULL) is an exite edge that will be eliminated in all but last + iteration of the loop. + EDGE_TO_CANCEL (if non-NULL) is an non-exit edge eliminated in the last iteration + of loop. + Return results in SIZE, estimate benefits for complete unrolling exiting by EXIT. + Stop estimating after UPPER_BOUND is met. Return true in this case. */ + +static bool +tree_estimate_loop_size (struct loop *loop, edge exit, edge edge_to_cancel, struct loop_size *size, + int upper_bound) +{ + basic_block *body = get_loop_body (loop); + gimple_stmt_iterator gsi; + unsigned int i; + bool after_exit; + vec<basic_block> path = get_loop_hot_path (loop); + + size->overall = 0; + size->eliminated_by_peeling = 0; + size->last_iteration = 0; + size->last_iteration_eliminated_by_peeling = 0; + size->num_pure_calls_on_hot_path = 0; + size->num_non_pure_calls_on_hot_path = 0; + size->non_call_stmts_on_hot_path = 0; + size->num_branches_on_hot_path = 0; + size->constant_iv = 0; + + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, "Estimating sizes for loop %i\n", loop->num); + for (i = 0; i < loop->num_nodes; i++) + { + if (edge_to_cancel && body[i] != edge_to_cancel->src + && dominated_by_p (CDI_DOMINATORS, body[i], edge_to_cancel->src)) + after_exit = true; + else + after_exit = false; + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, " BB: %i, after_exit: %i\n", body[i]->index, after_exit); + + for (gsi = gsi_start_bb (body[i]); !gsi_end_p (gsi); gsi_next (&gsi)) + { + gimple stmt = gsi_stmt (gsi); + int num = estimate_num_insns (stmt, &eni_size_weights); + bool likely_eliminated = false; + bool likely_eliminated_last = false; + bool likely_eliminated_peeled = false; + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, " size: %3i ", num); + print_gimple_stmt (dump_file, gsi_stmt (gsi), 0, 0); + } + + /* Look for reasons why we might optimize this stmt away. */ + + if (gimple_has_side_effects (stmt)) + ; + /* Exit conditional. */ + else if (exit && body[i] == exit->src + && stmt == last_stmt (exit->src)) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, " Exit condition will be eliminated " + "in peeled copies.\n"); + likely_eliminated_peeled = true; + } + else if (edge_to_cancel && body[i] == edge_to_cancel->src + && stmt == last_stmt (edge_to_cancel->src)) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, " Exit condition will be eliminated " + "in last copy.\n"); + likely_eliminated_last = true; + } + /* Sets of IV variables */ + else if (gimple_code (stmt) == GIMPLE_ASSIGN + && constant_after_peeling (gimple_assign_lhs (stmt), stmt, loop)) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, " Induction variable computation will" + " be folded away.\n"); + likely_eliminated = true; + } + /* Assignments of IV variables. */ + else if (gimple_code (stmt) == GIMPLE_ASSIGN + && TREE_CODE (gimple_assign_lhs (stmt)) == SSA_NAME + && constant_after_peeling (gimple_assign_rhs1 (stmt), stmt, loop) + && (gimple_assign_rhs_class (stmt) != GIMPLE_BINARY_RHS + || constant_after_peeling (gimple_assign_rhs2 (stmt), + stmt, loop))) + { + size->constant_iv = true; + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, " Constant expression will be folded away.\n"); + likely_eliminated = true; + } + /* Conditionals. */ + else if ((gimple_code (stmt) == GIMPLE_COND + && constant_after_peeling (gimple_cond_lhs (stmt), stmt, loop) + && constant_after_peeling (gimple_cond_rhs (stmt), stmt, loop)) + || (gimple_code (stmt) == GIMPLE_SWITCH + && constant_after_peeling (gimple_switch_index (stmt), stmt, loop))) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, " Constant conditional.\n"); + likely_eliminated = true; + } + + size->overall += num; + if (likely_eliminated || likely_eliminated_peeled) + size->eliminated_by_peeling += num; + if (!after_exit) + { + size->last_iteration += num; + if (likely_eliminated || likely_eliminated_last) + size->last_iteration_eliminated_by_peeling += num; + } + if ((size->overall * 3 / 2 - size->eliminated_by_peeling + - size->last_iteration_eliminated_by_peeling) > upper_bound) + { + free (body); + path.release (); + return true; + } + } + } + while (path.length ()) + { + basic_block bb = path.pop (); + for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) + { + gimple stmt = gsi_stmt (gsi); + if (gimple_code (stmt) == GIMPLE_CALL) + { + int flags = gimple_call_flags (stmt); + tree decl = gimple_call_fndecl (stmt); + + if (decl && DECL_IS_BUILTIN (decl) + && is_inexpensive_builtin (decl)) + ; + else if (flags & (ECF_PURE | ECF_CONST)) + size->num_pure_calls_on_hot_path++; + else + size->num_non_pure_calls_on_hot_path++; + size->num_branches_on_hot_path ++; + } + else if (gimple_code (stmt) != GIMPLE_CALL + && gimple_code (stmt) != GIMPLE_DEBUG) + size->non_call_stmts_on_hot_path++; + if (((gimple_code (stmt) == GIMPLE_COND + && (!constant_after_peeling (gimple_cond_lhs (stmt), stmt, loop) + || constant_after_peeling (gimple_cond_rhs (stmt), stmt, loop))) + || (gimple_code (stmt) == GIMPLE_SWITCH + && !constant_after_peeling (gimple_switch_index (stmt), stmt, loop))) + && (!exit || bb != exit->src)) + size->num_branches_on_hot_path++; + } + } + path.release (); + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, "size: %i-%i, last_iteration: %i-%i\n", size->overall, + size->eliminated_by_peeling, size->last_iteration, + size->last_iteration_eliminated_by_peeling); + + free (body); + return false; +} + +/* Estimate number of insns of completely unrolled loop. + It is (NUNROLL + 1) * size of loop body with taking into account + the fact that in last copy everything after exit conditional + is dead and that some instructions will be eliminated after + peeling. + + Loop body is likely going to simplify further, this is difficult + to guess, we just decrease the result by 1/3. */ + +static unsigned HOST_WIDE_INT +estimated_unrolled_size (struct loop_size *size, + unsigned HOST_WIDE_INT nunroll) +{ + HOST_WIDE_INT unr_insns = ((nunroll) + * (HOST_WIDE_INT) (size->overall + - size->eliminated_by_peeling)); + if (!nunroll) + unr_insns = 0; + unr_insns += size->last_iteration - size->last_iteration_eliminated_by_peeling; + + unr_insns = unr_insns * 2 / 3; + if (unr_insns <= 0) + unr_insns = 1; + + return unr_insns; +} + +/* Loop LOOP is known to not loop. See if there is an edge in the loop + body that can be remove to make the loop to always exit and at + the same time it does not make any code potentially executed + during the last iteration dead. + + After complette unrolling we still may get rid of the conditional + on the exit in the last copy even if we have no idea what it does. + This is quite common case for loops of form + + int a[5]; + for (i=0;i<b;i++) + a[i]=0; + + Here we prove the loop to iterate 5 times but we do not know + it from induction variable. + + For now we handle only simple case where there is exit condition + just before the latch block and the latch block contains no statements + with side effect that may otherwise terminate the execution of loop + (such as by EH or by terminating the program or longjmp). + + In the general case we may want to cancel the paths leading to statements + loop-niter identified as having undefined effect in the last iteration. + The other cases are hopefully rare and will be cleaned up later. */ + +static edge +loop_edge_to_cancel (struct loop *loop) +{ + vec<edge> exits; + unsigned i; + edge edge_to_cancel; + gimple_stmt_iterator gsi; + + /* We want only one predecestor of the loop. */ + if (EDGE_COUNT (loop->latch->preds) > 1) + return NULL; + + exits = get_loop_exit_edges (loop); + + FOR_EACH_VEC_ELT (exits, i, edge_to_cancel) + { + /* Find the other edge than the loop exit + leaving the conditoinal. */ + if (EDGE_COUNT (edge_to_cancel->src->succs) != 2) + continue; + if (EDGE_SUCC (edge_to_cancel->src, 0) == edge_to_cancel) + edge_to_cancel = EDGE_SUCC (edge_to_cancel->src, 1); + else + edge_to_cancel = EDGE_SUCC (edge_to_cancel->src, 0); + + /* We only can handle conditionals. */ + if (!(edge_to_cancel->flags & (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE))) + continue; + + /* We should never have conditionals in the loop latch. */ + gcc_assert (edge_to_cancel->dest != loop->header); + + /* Check that it leads to loop latch. */ + if (edge_to_cancel->dest != loop->latch) + continue; + + exits.release (); + + /* Verify that the code in loop latch does nothing that may end program + execution without really reaching the exit. This may include + non-pure/const function calls, EH statements, volatile ASMs etc. */ + for (gsi = gsi_start_bb (loop->latch); !gsi_end_p (gsi); gsi_next (&gsi)) + if (gimple_has_side_effects (gsi_stmt (gsi))) + return NULL; + return edge_to_cancel; + } + exits.release (); + return NULL; +} + +/* Remove all tests for exits that are known to be taken after LOOP was + peeled NPEELED times. Put gcc_unreachable before every statement + known to not be executed. */ + +static bool +remove_exits_and_undefined_stmts (struct loop *loop, unsigned int npeeled) +{ + struct nb_iter_bound *elt; + bool changed = false; + + for (elt = loop->bounds; elt; elt = elt->next) + { + /* If statement is known to be undefined after peeling, turn it + into unreachable (or trap when debugging experience is supposed + to be good). */ + if (!elt->is_exit + && elt->bound.ult (double_int::from_uhwi (npeeled))) + { + gimple_stmt_iterator gsi = gsi_for_stmt (elt->stmt); + gimple stmt = gimple_build_call + (builtin_decl_implicit (BUILT_IN_UNREACHABLE), 0); + + gimple_set_location (stmt, gimple_location (elt->stmt)); + gsi_insert_before (&gsi, stmt, GSI_NEW_STMT); + changed = true; + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "Forced statement unreachable: "); + print_gimple_stmt (dump_file, elt->stmt, 0, 0); + } + } + /* If we know the exit will be taken after peeling, update. */ + else if (elt->is_exit + && elt->bound.ule (double_int::from_uhwi (npeeled))) + { + basic_block bb = gimple_bb (elt->stmt); + edge exit_edge = EDGE_SUCC (bb, 0); + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "Forced exit to be taken: "); + print_gimple_stmt (dump_file, elt->stmt, 0, 0); + } + if (!loop_exit_edge_p (loop, exit_edge)) + exit_edge = EDGE_SUCC (bb, 1); + gcc_checking_assert (loop_exit_edge_p (loop, exit_edge)); + if (exit_edge->flags & EDGE_TRUE_VALUE) + gimple_cond_make_true (elt->stmt); + else + gimple_cond_make_false (elt->stmt); + update_stmt (elt->stmt); + changed = true; + } + } + return changed; +} + +/* Remove all exits that are known to be never taken because of the loop bound + discovered. */ + +static bool +remove_redundant_iv_tests (struct loop *loop) +{ + struct nb_iter_bound *elt; + bool changed = false; + + if (!loop->any_upper_bound) + return false; + for (elt = loop->bounds; elt; elt = elt->next) + { + /* Exit is pointless if it won't be taken before loop reaches + upper bound. */ + if (elt->is_exit && loop->any_upper_bound + && loop->nb_iterations_upper_bound.ult (elt->bound)) + { + basic_block bb = gimple_bb (elt->stmt); + edge exit_edge = EDGE_SUCC (bb, 0); + struct tree_niter_desc niter; + + if (!loop_exit_edge_p (loop, exit_edge)) + exit_edge = EDGE_SUCC (bb, 1); + + /* Only when we know the actual number of iterations, not + just a bound, we can remove the exit. */ + if (!number_of_iterations_exit (loop, exit_edge, + &niter, false, false) + || !integer_onep (niter.assumptions) + || !integer_zerop (niter.may_be_zero) + || !niter.niter + || TREE_CODE (niter.niter) != INTEGER_CST + || !loop->nb_iterations_upper_bound.ult + (tree_to_double_int (niter.niter))) + continue; + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "Removed pointless exit: "); + print_gimple_stmt (dump_file, elt->stmt, 0, 0); + } + if (exit_edge->flags & EDGE_TRUE_VALUE) + gimple_cond_make_false (elt->stmt); + else + gimple_cond_make_true (elt->stmt); + update_stmt (elt->stmt); + changed = true; + } + } + return changed; +} + +/* Stores loops that will be unlooped after we process whole loop tree. */ +static vec<loop_p> loops_to_unloop; +static vec<int> loops_to_unloop_nunroll; + +/* Cancel all fully unrolled loops by putting __builtin_unreachable + on the latch edge. + We do it after all unrolling since unlooping moves basic blocks + across loop boundaries trashing loop closed SSA form as well + as SCEV info needed to be intact during unrolling. + + IRRED_INVALIDATED is used to bookkeep if information about + irreducible regions may become invalid as a result + of the transformation. + LOOP_CLOSED_SSA_INVALIDATED is used to bookkepp the case + when we need to go into loop closed SSA form. */ + +static void +unloop_loops (bitmap loop_closed_ssa_invalidated, + bool *irred_invalidated) +{ + while (loops_to_unloop.length ()) + { + struct loop *loop = loops_to_unloop.pop (); + int n_unroll = loops_to_unloop_nunroll.pop (); + basic_block latch = loop->latch; + edge latch_edge = loop_latch_edge (loop); + int flags = latch_edge->flags; + location_t locus = latch_edge->goto_locus; + gimple stmt; + gimple_stmt_iterator gsi; + + remove_exits_and_undefined_stmts (loop, n_unroll); + + /* Unloop destroys the latch edge. */ + unloop (loop, irred_invalidated, loop_closed_ssa_invalidated); + + /* Create new basic block for the latch edge destination and wire + it in. */ + stmt = gimple_build_call (builtin_decl_implicit (BUILT_IN_UNREACHABLE), 0); + latch_edge = make_edge (latch, create_basic_block (NULL, NULL, latch), flags); + latch_edge->probability = 0; + latch_edge->count = 0; + latch_edge->flags |= flags; + latch_edge->goto_locus = locus; + + latch_edge->dest->loop_father = current_loops->tree_root; + latch_edge->dest->count = 0; + latch_edge->dest->frequency = 0; + set_immediate_dominator (CDI_DOMINATORS, latch_edge->dest, latch_edge->src); + + gsi = gsi_start_bb (latch_edge->dest); + gsi_insert_after (&gsi, stmt, GSI_NEW_STMT); + } + loops_to_unloop.release (); + loops_to_unloop_nunroll.release (); +} + +/* Tries to unroll LOOP completely, i.e. NITER times. + UL determines which loops we are allowed to unroll. + EXIT is the exit of the loop that should be eliminated. + MAXITER specfy bound on number of iterations, -1 if it is + not known or too large for HOST_WIDE_INT. The location + LOCUS corresponding to the loop is used when emitting + a summary of the unroll to the dump file. */ + +static bool +try_unroll_loop_completely (struct loop *loop, + edge exit, tree niter, + enum unroll_level ul, + HOST_WIDE_INT maxiter, + location_t locus) +{ + unsigned HOST_WIDE_INT n_unroll, ninsns, max_unroll, unr_insns; + gimple cond; + struct loop_size size; + bool n_unroll_found = false; + edge edge_to_cancel = NULL; + + /* See if we proved number of iterations to be low constant. + + EXIT is an edge that will be removed in all but last iteration of + the loop. + + EDGE_TO_CACNEL is an edge that will be removed from the last iteration + of the unrolled sequence and is expected to make the final loop not + rolling. + + If the number of execution of loop is determined by standard induction + variable test, then EXIT and EDGE_TO_CANCEL are the two edges leaving + from the iv test. */ + if (tree_fits_uhwi_p (niter)) + { + n_unroll = tree_to_uhwi (niter); + n_unroll_found = true; + edge_to_cancel = EDGE_SUCC (exit->src, 0); + if (edge_to_cancel == exit) + edge_to_cancel = EDGE_SUCC (exit->src, 1); + } + /* We do not know the number of iterations and thus we can not eliminate + the EXIT edge. */ + else + exit = NULL; + + /* See if we can improve our estimate by using recorded loop bounds. */ + if (maxiter >= 0 + && (!n_unroll_found || (unsigned HOST_WIDE_INT)maxiter < n_unroll)) + { + n_unroll = maxiter; + n_unroll_found = true; + /* Loop terminates before the IV variable test, so we can not + remove it in the last iteration. */ + edge_to_cancel = NULL; + } + + if (!n_unroll_found) + return false; + + max_unroll = PARAM_VALUE (PARAM_MAX_COMPLETELY_PEEL_TIMES); + if (n_unroll > max_unroll) + return false; + + if (!edge_to_cancel) + edge_to_cancel = loop_edge_to_cancel (loop); + + if (n_unroll) + { + sbitmap wont_exit; + edge e; + unsigned i; + bool large; + vec<edge> to_remove = vNULL; + if (ul == UL_SINGLE_ITER) + return false; + + large = tree_estimate_loop_size + (loop, exit, edge_to_cancel, &size, + PARAM_VALUE (PARAM_MAX_COMPLETELY_PEELED_INSNS)); + ninsns = size.overall; + if (large) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, "Not unrolling loop %d: it is too large.\n", + loop->num); + return false; + } + + unr_insns = estimated_unrolled_size (&size, n_unroll); + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, " Loop size: %d\n", (int) ninsns); + fprintf (dump_file, " Estimated size after unrolling: %d\n", + (int) unr_insns); + } + + /* If the code is going to shrink, we don't need to be extra cautious + on guessing if the unrolling is going to be profitable. */ + if (unr_insns + /* If there is IV variable that will become constant, we save + one instruction in the loop prologue we do not account + otherwise. */ + <= ninsns + (size.constant_iv != false)) + ; + /* We unroll only inner loops, because we do not consider it profitable + otheriwse. We still can cancel loopback edge of not rolling loop; + this is always a good idea. */ + else if (ul == UL_NO_GROWTH) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, "Not unrolling loop %d: size would grow.\n", + loop->num); + return false; + } + /* Outer loops tend to be less interesting candidates for complette + unrolling unless we can do a lot of propagation into the inner loop + body. For now we disable outer loop unrolling when the code would + grow. */ + else if (loop->inner) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, "Not unrolling loop %d: " + "it is not innermost and code would grow.\n", + loop->num); + return false; + } + /* If there is call on a hot path through the loop, then + there is most probably not much to optimize. */ + else if (size.num_non_pure_calls_on_hot_path) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, "Not unrolling loop %d: " + "contains call and code would grow.\n", + loop->num); + return false; + } + /* If there is pure/const call in the function, then we + can still optimize the unrolled loop body if it contains + some other interesting code than the calls and code + storing or cumulating the return value. */ + else if (size.num_pure_calls_on_hot_path + /* One IV increment, one test, one ivtmp store + and one useful stmt. That is about minimal loop + doing pure call. */ + && (size.non_call_stmts_on_hot_path + <= 3 + size.num_pure_calls_on_hot_path)) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, "Not unrolling loop %d: " + "contains just pure calls and code would grow.\n", + loop->num); + return false; + } + /* Complette unrolling is major win when control flow is removed and + one big basic block is created. If the loop contains control flow + the optimization may still be a win because of eliminating the loop + overhead but it also may blow the branch predictor tables. + Limit number of branches on the hot path through the peeled + sequence. */ + else if (size.num_branches_on_hot_path * (int)n_unroll + > PARAM_VALUE (PARAM_MAX_PEEL_BRANCHES)) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, "Not unrolling loop %d: " + " number of branches on hot path in the unrolled sequence" + " reach --param max-peel-branches limit.\n", + loop->num); + return false; + } + else if (unr_insns + > (unsigned) PARAM_VALUE (PARAM_MAX_COMPLETELY_PEELED_INSNS)) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, "Not unrolling loop %d: " + "(--param max-completely-peeled-insns limit reached).\n", + loop->num); + return false; + } + + initialize_original_copy_tables (); + wont_exit = sbitmap_alloc (n_unroll + 1); + bitmap_ones (wont_exit); + bitmap_clear_bit (wont_exit, 0); + + if (!gimple_duplicate_loop_to_header_edge (loop, loop_preheader_edge (loop), + n_unroll, wont_exit, + exit, &to_remove, + DLTHE_FLAG_UPDATE_FREQ + | DLTHE_FLAG_COMPLETTE_PEEL)) + { + free_original_copy_tables (); + free (wont_exit); + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, "Failed to duplicate the loop\n"); + return false; + } + + FOR_EACH_VEC_ELT (to_remove, i, e) + { + bool ok = remove_path (e); + gcc_assert (ok); + } + + to_remove.release (); + free (wont_exit); + free_original_copy_tables (); + } + + + /* Remove the conditional from the last copy of the loop. */ + if (edge_to_cancel) + { + cond = last_stmt (edge_to_cancel->src); + if (edge_to_cancel->flags & EDGE_TRUE_VALUE) + gimple_cond_make_false (cond); + else + gimple_cond_make_true (cond); + update_stmt (cond); + /* Do not remove the path. Doing so may remove outer loop + and confuse bookkeeping code in tree_unroll_loops_completelly. */ + } + + /* Store the loop for later unlooping and exit removal. */ + loops_to_unloop.safe_push (loop); + loops_to_unloop_nunroll.safe_push (n_unroll); + + if (dump_enabled_p ()) + { + if (!n_unroll) + dump_printf_loc (MSG_OPTIMIZED_LOCATIONS | TDF_DETAILS, locus, + "loop turned into non-loop; it never loops\n"); + else + { + dump_printf_loc (MSG_OPTIMIZED_LOCATIONS | TDF_DETAILS, locus, + "loop with %d iterations completely unrolled", + (int) (n_unroll + 1)); + if (profile_info) + dump_printf (MSG_OPTIMIZED_LOCATIONS | TDF_DETAILS, + " (header execution count %d)", + (int)loop->header->count); + dump_printf (MSG_OPTIMIZED_LOCATIONS | TDF_DETAILS, "\n"); + } + } + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + if (exit) + fprintf (dump_file, "Exit condition of peeled iterations was " + "eliminated.\n"); + if (edge_to_cancel) + fprintf (dump_file, "Last iteration exit edge was proved true.\n"); + else + fprintf (dump_file, "Latch of last iteration was marked by " + "__builtin_unreachable ().\n"); + } + + return true; +} + +/* Adds a canonical induction variable to LOOP if suitable. + CREATE_IV is true if we may create a new iv. UL determines + which loops we are allowed to completely unroll. If TRY_EVAL is true, we try + to determine the number of iterations of a loop by direct evaluation. + Returns true if cfg is changed. */ + +static bool +canonicalize_loop_induction_variables (struct loop *loop, + bool create_iv, enum unroll_level ul, + bool try_eval) +{ + edge exit = NULL; + tree niter; + HOST_WIDE_INT maxiter; + bool modified = false; + location_t locus = UNKNOWN_LOCATION; + + niter = number_of_latch_executions (loop); + exit = single_exit (loop); + if (TREE_CODE (niter) == INTEGER_CST) + locus = gimple_location (last_stmt (exit->src)); + else + { + /* If the loop has more than one exit, try checking all of them + for # of iterations determinable through scev. */ + if (!exit) + niter = find_loop_niter (loop, &exit); + + /* Finally if everything else fails, try brute force evaluation. */ + if (try_eval + && (chrec_contains_undetermined (niter) + || TREE_CODE (niter) != INTEGER_CST)) + niter = find_loop_niter_by_eval (loop, &exit); + + if (exit) + locus = gimple_location (last_stmt (exit->src)); + + if (TREE_CODE (niter) != INTEGER_CST) + exit = NULL; + } + + /* We work exceptionally hard here to estimate the bound + by find_loop_niter_by_eval. Be sure to keep it for future. */ + if (niter && TREE_CODE (niter) == INTEGER_CST) + { + record_niter_bound (loop, tree_to_double_int (niter), + exit == single_likely_exit (loop), true); + } + + /* Force re-computation of loop bounds so we can remove redundant exits. */ + maxiter = max_loop_iterations_int (loop); + + if (dump_file && (dump_flags & TDF_DETAILS) + && TREE_CODE (niter) == INTEGER_CST) + { + fprintf (dump_file, "Loop %d iterates ", loop->num); + print_generic_expr (dump_file, niter, TDF_SLIM); + fprintf (dump_file, " times.\n"); + } + if (dump_file && (dump_flags & TDF_DETAILS) + && maxiter >= 0) + { + fprintf (dump_file, "Loop %d iterates at most %i times.\n", loop->num, + (int)maxiter); + } + + /* Remove exits that are known to be never taken based on loop bound. + Needs to be called after compilation of max_loop_iterations_int that + populates the loop bounds. */ + modified |= remove_redundant_iv_tests (loop); + + if (try_unroll_loop_completely (loop, exit, niter, ul, maxiter, locus)) + return true; + + if (create_iv + && niter && !chrec_contains_undetermined (niter) + && exit && just_once_each_iteration_p (loop, exit->src)) + create_canonical_iv (loop, exit, niter); + + return modified; +} + +/* The main entry point of the pass. Adds canonical induction variables + to the suitable loops. */ + +unsigned int +canonicalize_induction_variables (void) +{ + struct loop *loop; + bool changed = false; + bool irred_invalidated = false; + bitmap loop_closed_ssa_invalidated = BITMAP_ALLOC (NULL); + + free_numbers_of_iterations_estimates (); + estimate_numbers_of_iterations (); + + FOR_EACH_LOOP (loop, LI_FROM_INNERMOST) + { + changed |= canonicalize_loop_induction_variables (loop, + true, UL_SINGLE_ITER, + true); + } + gcc_assert (!need_ssa_update_p (cfun)); + + unloop_loops (loop_closed_ssa_invalidated, &irred_invalidated); + if (irred_invalidated + && loops_state_satisfies_p (LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)) + mark_irreducible_loops (); + + /* Clean up the information about numbers of iterations, since brute force + evaluation could reveal new information. */ + scev_reset (); + + if (!bitmap_empty_p (loop_closed_ssa_invalidated)) + { + gcc_checking_assert (loops_state_satisfies_p (LOOP_CLOSED_SSA)); + rewrite_into_loop_closed_ssa (NULL, TODO_update_ssa); + } + BITMAP_FREE (loop_closed_ssa_invalidated); + + if (changed) + return TODO_cleanup_cfg; + return 0; +} + +/* Propagate VAL into all uses of SSA_NAME. */ + +static void +propagate_into_all_uses (tree ssa_name, tree val) +{ + imm_use_iterator iter; + gimple use_stmt; + + FOR_EACH_IMM_USE_STMT (use_stmt, iter, ssa_name) + { + gimple_stmt_iterator use_stmt_gsi = gsi_for_stmt (use_stmt); + use_operand_p use; + + FOR_EACH_IMM_USE_ON_STMT (use, iter) + SET_USE (use, val); + + if (is_gimple_assign (use_stmt) + && get_gimple_rhs_class (gimple_assign_rhs_code (use_stmt)) + == GIMPLE_SINGLE_RHS) + { + tree rhs = gimple_assign_rhs1 (use_stmt); + + if (TREE_CODE (rhs) == ADDR_EXPR) + recompute_tree_invariant_for_addr_expr (rhs); + } + + fold_stmt_inplace (&use_stmt_gsi); + update_stmt (use_stmt); + maybe_clean_or_replace_eh_stmt (use_stmt, use_stmt); + } +} + +/* Propagate constant SSA_NAMEs defined in basic block BB. */ + +static void +propagate_constants_for_unrolling (basic_block bb) +{ + gimple_stmt_iterator gsi; + + /* Look for degenerate PHI nodes with constant argument. */ + for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); ) + { + gimple phi = gsi_stmt (gsi); + tree result = gimple_phi_result (phi); + tree arg = gimple_phi_arg_def (phi, 0); + + if (gimple_phi_num_args (phi) == 1 && TREE_CODE (arg) == INTEGER_CST) + { + propagate_into_all_uses (result, arg); + gsi_remove (&gsi, true); + release_ssa_name (result); + } + else + gsi_next (&gsi); + } + + /* Look for assignments to SSA names with constant RHS. */ + for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); ) + { + gimple stmt = gsi_stmt (gsi); + tree lhs; + + if (is_gimple_assign (stmt) + && gimple_assign_rhs_code (stmt) == INTEGER_CST + && (lhs = gimple_assign_lhs (stmt), TREE_CODE (lhs) == SSA_NAME) + && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs)) + { + propagate_into_all_uses (lhs, gimple_assign_rhs1 (stmt)); + gsi_remove (&gsi, true); + release_ssa_name (lhs); + } + else + gsi_next (&gsi); + } +} + +/* Process loops from innermost to outer, stopping at the innermost + loop we unrolled. */ + +static bool +tree_unroll_loops_completely_1 (bool may_increase_size, bool unroll_outer, + vec<loop_p, va_heap>& father_stack, + struct loop *loop) +{ + struct loop *loop_father; + bool changed = false; + struct loop *inner; + enum unroll_level ul; + + /* Process inner loops first. */ + for (inner = loop->inner; inner != NULL; inner = inner->next) + changed |= tree_unroll_loops_completely_1 (may_increase_size, + unroll_outer, father_stack, + inner); + + /* If we changed an inner loop we cannot process outer loops in this + iteration because SSA form is not up-to-date. Continue with + siblings of outer loops instead. */ + if (changed) + return true; + + /* Don't unroll #pragma omp simd loops until the vectorizer + attempts to vectorize those. */ + if (loop->force_vect) + return false; + + /* Try to unroll this loop. */ + loop_father = loop_outer (loop); + if (!loop_father) + return false; + + if (may_increase_size && optimize_loop_nest_for_speed_p (loop) + /* Unroll outermost loops only if asked to do so or they do + not cause code growth. */ + && (unroll_outer || loop_outer (loop_father))) + ul = UL_ALL; + else + ul = UL_NO_GROWTH; + + if (canonicalize_loop_induction_variables + (loop, false, ul, !flag_tree_loop_ivcanon)) + { + /* If we'll continue unrolling, we need to propagate constants + within the new basic blocks to fold away induction variable + computations; otherwise, the size might blow up before the + iteration is complete and the IR eventually cleaned up. */ + if (loop_outer (loop_father) && !loop_father->aux) + { + father_stack.safe_push (loop_father); + loop_father->aux = loop_father; + } + + return true; + } + + return false; +} + +/* Unroll LOOPS completely if they iterate just few times. Unless + MAY_INCREASE_SIZE is true, perform the unrolling only if the + size of the code does not increase. */ + +unsigned int +tree_unroll_loops_completely (bool may_increase_size, bool unroll_outer) +{ + auto_vec<loop_p, 16> father_stack; + bool changed; + int iteration = 0; + bool irred_invalidated = false; + + do + { + changed = false; + bitmap loop_closed_ssa_invalidated = NULL; + + if (loops_state_satisfies_p (LOOP_CLOSED_SSA)) + loop_closed_ssa_invalidated = BITMAP_ALLOC (NULL); + + free_numbers_of_iterations_estimates (); + estimate_numbers_of_iterations (); + + changed = tree_unroll_loops_completely_1 (may_increase_size, + unroll_outer, father_stack, + current_loops->tree_root); + if (changed) + { + struct loop **iter; + unsigned i; + + /* Be sure to skip unlooped loops while procesing father_stack + array. */ + FOR_EACH_VEC_ELT (loops_to_unloop, i, iter) + (*iter)->aux = NULL; + FOR_EACH_VEC_ELT (father_stack, i, iter) + if (!(*iter)->aux) + *iter = NULL; + unloop_loops (loop_closed_ssa_invalidated, &irred_invalidated); + + /* We can not use TODO_update_ssa_no_phi because VOPS gets confused. */ + if (loop_closed_ssa_invalidated + && !bitmap_empty_p (loop_closed_ssa_invalidated)) + rewrite_into_loop_closed_ssa (loop_closed_ssa_invalidated, + TODO_update_ssa); + else + update_ssa (TODO_update_ssa); + + /* Propagate the constants within the new basic blocks. */ + FOR_EACH_VEC_ELT (father_stack, i, iter) + if (*iter) + { + unsigned j; + basic_block *body = get_loop_body_in_dom_order (*iter); + for (j = 0; j < (*iter)->num_nodes; j++) + propagate_constants_for_unrolling (body[j]); + free (body); + (*iter)->aux = NULL; + } + father_stack.truncate (0); + + /* This will take care of removing completely unrolled loops + from the loop structures so we can continue unrolling now + innermost loops. */ + if (cleanup_tree_cfg ()) + update_ssa (TODO_update_ssa_only_virtuals); + + /* Clean up the information about numbers of iterations, since + complete unrolling might have invalidated it. */ + scev_reset (); +#ifdef ENABLE_CHECKING + if (loops_state_satisfies_p (LOOP_CLOSED_SSA)) + verify_loop_closed_ssa (true); +#endif + } + if (loop_closed_ssa_invalidated) + BITMAP_FREE (loop_closed_ssa_invalidated); + } + while (changed + && ++iteration <= PARAM_VALUE (PARAM_MAX_UNROLL_ITERATIONS)); + + father_stack.release (); + + if (irred_invalidated + && loops_state_satisfies_p (LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)) + mark_irreducible_loops (); + + return 0; +} + +/* Canonical induction variable creation pass. */ + +static unsigned int +tree_ssa_loop_ivcanon (void) +{ + if (number_of_loops (cfun) <= 1) + return 0; + + return canonicalize_induction_variables (); +} + +static bool +gate_tree_ssa_loop_ivcanon (void) +{ + return flag_tree_loop_ivcanon != 0; +} + +namespace { + +const pass_data pass_data_iv_canon = +{ + GIMPLE_PASS, /* type */ + "ivcanon", /* name */ + OPTGROUP_LOOP, /* optinfo_flags */ + true, /* has_gate */ + true, /* has_execute */ + TV_TREE_LOOP_IVCANON, /* tv_id */ + ( PROP_cfg | PROP_ssa ), /* properties_required */ + 0, /* properties_provided */ + 0, /* properties_destroyed */ + 0, /* todo_flags_start */ + 0, /* todo_flags_finish */ +}; + +class pass_iv_canon : public gimple_opt_pass +{ +public: + pass_iv_canon (gcc::context *ctxt) + : gimple_opt_pass (pass_data_iv_canon, ctxt) + {} + + /* opt_pass methods: */ + bool gate () { return gate_tree_ssa_loop_ivcanon (); } + unsigned int execute () { return tree_ssa_loop_ivcanon (); } + +}; // class pass_iv_canon + +} // anon namespace + +gimple_opt_pass * +make_pass_iv_canon (gcc::context *ctxt) +{ + return new pass_iv_canon (ctxt); +} + +/* Complete unrolling of loops. */ + +static unsigned int +tree_complete_unroll (void) +{ + if (number_of_loops (cfun) <= 1) + return 0; + + return tree_unroll_loops_completely (flag_unroll_loops + || flag_peel_loops + || optimize >= 3, true); +} + +static bool +gate_tree_complete_unroll (void) +{ + return true; +} + +namespace { + +const pass_data pass_data_complete_unroll = +{ + GIMPLE_PASS, /* type */ + "cunroll", /* name */ + OPTGROUP_LOOP, /* optinfo_flags */ + true, /* has_gate */ + true, /* has_execute */ + TV_COMPLETE_UNROLL, /* tv_id */ + ( PROP_cfg | PROP_ssa ), /* properties_required */ + 0, /* properties_provided */ + 0, /* properties_destroyed */ + 0, /* todo_flags_start */ + 0, /* todo_flags_finish */ +}; + +class pass_complete_unroll : public gimple_opt_pass +{ +public: + pass_complete_unroll (gcc::context *ctxt) + : gimple_opt_pass (pass_data_complete_unroll, ctxt) + {} + + /* opt_pass methods: */ + bool gate () { return gate_tree_complete_unroll (); } + unsigned int execute () { return tree_complete_unroll (); } + +}; // class pass_complete_unroll + +} // anon namespace + +gimple_opt_pass * +make_pass_complete_unroll (gcc::context *ctxt) +{ + return new pass_complete_unroll (ctxt); +} + +/* Complete unrolling of inner loops. */ + +static unsigned int +tree_complete_unroll_inner (void) +{ + unsigned ret = 0; + + loop_optimizer_init (LOOPS_NORMAL + | LOOPS_HAVE_RECORDED_EXITS); + if (number_of_loops (cfun) > 1) + { + scev_initialize (); + ret = tree_unroll_loops_completely (optimize >= 3, false); + free_numbers_of_iterations_estimates (); + scev_finalize (); + } + loop_optimizer_finalize (); + + return ret; +} + +static bool +gate_tree_complete_unroll_inner (void) +{ + return optimize >= 2; +} + +namespace { + +const pass_data pass_data_complete_unrolli = +{ + GIMPLE_PASS, /* type */ + "cunrolli", /* name */ + OPTGROUP_LOOP, /* optinfo_flags */ + true, /* has_gate */ + true, /* has_execute */ + TV_COMPLETE_UNROLL, /* tv_id */ + ( PROP_cfg | PROP_ssa ), /* properties_required */ + 0, /* properties_provided */ + 0, /* properties_destroyed */ + 0, /* todo_flags_start */ + TODO_verify_flow, /* todo_flags_finish */ +}; + +class pass_complete_unrolli : public gimple_opt_pass +{ +public: + pass_complete_unrolli (gcc::context *ctxt) + : gimple_opt_pass (pass_data_complete_unrolli, ctxt) + {} + + /* opt_pass methods: */ + bool gate () { return gate_tree_complete_unroll_inner (); } + unsigned int execute () { return tree_complete_unroll_inner (); } + +}; // class pass_complete_unrolli + +} // anon namespace + +gimple_opt_pass * +make_pass_complete_unrolli (gcc::context *ctxt) +{ + return new pass_complete_unrolli (ctxt); +} + + |