/* Induction variable canonicalization.
- Copyright (C) 2004 Free Software Foundation, Inc.
+ Copyright (C) 2004, 2005, 2007 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 2, or (at your option) any
+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
for more details.
You should have received a copy of the GNU General Public License
-along with GCC; see the file COPYING. If not, write to the Free
-Software Foundation, 59 Temple Place - Suite 330, Boston, MA
-02111-1307, USA. */
+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)
#include "flags.h"
#include "tree-inline.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. */
}
cond = last_stmt (exit->src);
- in = exit->src->succ;
+ in = EDGE_SUCC (exit->src, 0);
if (in == exit)
- in = in->succ_next;
+ 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
with a modulo arithmetics. */
type = TREE_TYPE (niter);
- niter = fold (build2 (PLUS_EXPR, type,
- niter,
- build_int_cst (type, 1)));
+ niter = fold_build2 (PLUS_EXPR, type,
+ niter,
+ build_int_cst (type, 1));
incr_at = bsi_last (in->src);
create_iv (niter,
- fold_convert (type, integer_minus_one_node),
+ build_int_cst (type, -1),
NULL_TREE, loop,
&incr_at, false, NULL, &var);
COND_EXPR_COND (cond) = build2 (cmp, boolean_type_node,
var,
build_int_cst (type, 0));
- modify_stmt (cond);
+ update_stmt (cond);
}
-/* Computes an estimated number of insns in LOOP. */
+/* Computes an estimated number of insns in LOOP, weighted by WEIGHTS. */
unsigned
-tree_num_loop_insns (struct loop *loop)
+tree_num_loop_insns (struct loop *loop, eni_weights *weights)
{
basic_block *body = get_loop_body (loop);
block_stmt_iterator bsi;
for (i = 0; i < loop->num_nodes; i++)
for (bsi = bsi_start (body[i]); !bsi_end_p (bsi); bsi_next (&bsi))
- size += estimate_num_insns (bsi_stmt (bsi));
+ size += estimate_num_insns (bsi_stmt (bsi), weights);
free (body);
return size;
}
-/* Tries to unroll LOOP completely, i.e. NITER times. LOOPS is the
- loop tree. COMPLETELY_UNROLL is true if we should unroll the loop
- even if it may cause code growth. EXIT is the exit of the loop
- that should be eliminated. */
+/* Estimate number of insns of completely unrolled loop. We assume
+ that the size of the unrolled loop is decreased in the
+ following way (the numbers of insns are based on what
+ estimate_num_insns returns for appropriate statements):
+
+ 1) exit condition gets removed (2 insns)
+ 2) increment of the control variable gets removed (2 insns)
+ 3) All remaining statements are likely to get simplified
+ due to constant propagation. Hard to estimate; just
+ as a heuristics we decrease the rest by 1/3.
+
+ NINSNS is the number of insns in the loop before unrolling.
+ NUNROLL is the number of times the loop is unrolled. */
+
+static unsigned HOST_WIDE_INT
+estimated_unrolled_size (unsigned HOST_WIDE_INT ninsns,
+ unsigned HOST_WIDE_INT nunroll)
+{
+ HOST_WIDE_INT unr_insns = 2 * ((HOST_WIDE_INT) ninsns - 4) / 3;
+ if (unr_insns <= 0)
+ unr_insns = 1;
+ unr_insns *= (nunroll + 1);
+
+ return unr_insns;
+}
+
+/* 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. */
static bool
-try_unroll_loop_completely (struct loops *loops ATTRIBUTE_UNUSED,
- struct loop *loop,
+try_unroll_loop_completely (struct loop *loop,
edge exit, tree niter,
- bool completely_unroll)
+ enum unroll_level ul)
{
- unsigned HOST_WIDE_INT n_unroll, ninsns, max_unroll;
- tree old_cond, cond, dont_exit, do_exit;
+ unsigned HOST_WIDE_INT n_unroll, ninsns, max_unroll, unr_insns;
+ tree cond;
if (loop->inner)
return false;
if (n_unroll)
{
- if (!completely_unroll)
+ if (ul == UL_SINGLE_ITER)
return false;
- ninsns = tree_num_loop_insns (loop);
+ ninsns = tree_num_loop_insns (loop, &eni_size_weights);
if (n_unroll * ninsns
> (unsigned) PARAM_VALUE (PARAM_MAX_COMPLETELY_PEELED_INSNS))
return false;
- }
- if (exit->flags & EDGE_TRUE_VALUE)
- {
- dont_exit = boolean_false_node;
- do_exit = boolean_true_node;
- }
- else
- {
- dont_exit = boolean_true_node;
- do_exit = boolean_false_node;
+ if (ul == UL_NO_GROWTH)
+ {
+ unr_insns = estimated_unrolled_size (ninsns, 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 (unr_insns > ninsns)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "Not unrolling loop %d:\n", loop->num);
+ return false;
+ }
+ }
}
- cond = last_stmt (exit->src);
-
+
if (n_unroll)
{
- if (!flag_unroll_loops)
- return false;
+ sbitmap wont_exit;
+ edge e;
+ unsigned i;
+ VEC (edge, heap) *to_remove = NULL;
- old_cond = COND_EXPR_COND (cond);
- COND_EXPR_COND (cond) = dont_exit;
- modify_stmt (cond);
+ initialize_original_copy_tables ();
+ wont_exit = sbitmap_alloc (n_unroll + 1);
+ sbitmap_ones (wont_exit);
+ RESET_BIT (wont_exit, 0);
-#if 0
- /* The necessary infrastructure is not in yet. */
if (!tree_duplicate_loop_to_header_edge (loop, loop_preheader_edge (loop),
- loops, n_unroll, NULL,
- NULL, NULL, NULL, 0))
-#endif
+ n_unroll, wont_exit,
+ exit, &to_remove,
+ DLTHE_FLAG_UPDATE_FREQ
+ | DLTHE_FLAG_COMPLETTE_PEEL))
{
- COND_EXPR_COND (cond) = old_cond;
+ free_original_copy_tables ();
+ free (wont_exit);
return false;
}
+
+ for (i = 0; VEC_iterate (edge, to_remove, i, e); i++)
+ {
+ bool ok = remove_path (e);
+ gcc_assert (ok);
+ }
+
+ VEC_free (edge, heap, to_remove);
+ free (wont_exit);
+ free_original_copy_tables ();
}
-
- COND_EXPR_COND (cond) = do_exit;
- modify_stmt (cond);
+
+ cond = last_stmt (exit->src);
+ COND_EXPR_COND (cond) = (exit->flags & EDGE_TRUE_VALUE) ? boolean_true_node
+ : boolean_false_node;
+ update_stmt (cond);
+ update_ssa (TODO_update_ssa);
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Unrolled loop %d completely.\n", loop->num);
return true;
}
-/* Adds a canonical induction variable to LOOP if suitable. LOOPS is the loops
- tree. CREATE_IV is true if we may create a new iv. COMPLETELY_UNROLL is
- true if we should do complete unrolling even if it may cause the code
- growth. 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. */
+/* 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 loops *loops, struct loop *loop,
- bool create_iv, bool completely_unroll,
+canonicalize_loop_induction_variables (struct loop *loop,
+ bool create_iv, enum unroll_level ul,
bool try_eval)
{
edge exit = NULL;
tree niter;
- niter = number_of_iterations_in_loop (loop);
+ niter = number_of_latch_executions (loop);
if (TREE_CODE (niter) == INTEGER_CST)
{
- exit = loop->single_exit;
+ exit = single_exit (loop);
if (!just_once_each_iteration_p (loop, exit->src))
return false;
-
- /* The result of number_of_iterations_in_loop is by one higher than
- we expect (i.e. it returns number of executions of the exit
- condition, not of the loop latch edge). */
- niter = fold (build2 (MINUS_EXPR, TREE_TYPE (niter), niter,
- build_int_cst (TREE_TYPE (niter), 1)));
}
- else if (try_eval)
- niter = find_loop_niter_by_eval (loop, &exit);
-
- if (chrec_contains_undetermined (niter)
- || TREE_CODE (niter) != INTEGER_CST)
- return false;
+ else
+ {
+ /* If the loop has more than one exit, try checking all of them
+ for # of iterations determinable through scev. */
+ if (!single_exit (loop))
+ 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 (chrec_contains_undetermined (niter)
+ || TREE_CODE (niter) != INTEGER_CST)
+ return false;
+ }
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, " times.\n");
}
- if (try_unroll_loop_completely (loops, loop, exit, niter, completely_unroll))
+ if (try_unroll_loop_completely (loop, exit, niter, ul))
return true;
if (create_iv)
}
/* The main entry point of the pass. Adds canonical induction variables
- to the suitable LOOPS. */
+ to the suitable loops. */
-void
-canonicalize_induction_variables (struct loops *loops)
+unsigned int
+canonicalize_induction_variables (void)
{
- unsigned i;
+ loop_iterator li;
struct loop *loop;
+ bool changed = false;
- for (i = 1; i < loops->num; i++)
+ FOR_EACH_LOOP (li, loop, 0)
{
- loop = loops->parray[i];
-
- if (loop)
- canonicalize_loop_induction_variables (loops, loop, true, false, true);
+ changed |= canonicalize_loop_induction_variables (loop,
+ true, UL_SINGLE_ITER,
+ true);
}
-#if 0
- /* The necessary infrastructure is not in yet. */
+ /* Clean up the information about numbers of iterations, since brute force
+ evaluation could reveal new information. */
+ scev_reset ();
+
if (changed)
- cleanup_tree_cfg_loop ();
-#endif
+ return TODO_cleanup_cfg;
+ return 0;
}
-/* Unroll LOOPS completely if they iterate just few times. */
+/* 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. */
-void
-tree_unroll_loops_completely (struct loops *loops)
+unsigned int
+tree_unroll_loops_completely (bool may_increase_size)
{
- unsigned i;
+ loop_iterator li;
struct loop *loop;
bool changed = false;
+ enum unroll_level ul;
- for (i = 1; i < loops->num; i++)
+ FOR_EACH_LOOP (li, loop, 0)
{
- loop = loops->parray[i];
+ if (may_increase_size && maybe_hot_bb_p (loop->header))
+ ul = UL_ALL;
+ else
+ ul = UL_NO_GROWTH;
+ changed |= canonicalize_loop_induction_variables (loop,
+ false, ul,
+ !flag_tree_loop_ivcanon);
+ }
+
+ /* Clean up the information about numbers of iterations, since complete
+ unrolling might have invalidated it. */
+ scev_reset ();
+
+ if (changed)
+ return TODO_cleanup_cfg;
+ return 0;
+}
+
+/* Checks whether LOOP is empty. */
+
+static bool
+empty_loop_p (struct loop *loop)
+{
+ edge exit;
+ struct tree_niter_desc niter;
+ tree phi, def;
+ basic_block *body;
+ block_stmt_iterator bsi;
+ unsigned i;
+ tree stmt;
- if (!loop)
+ /* If the loop has multiple exits, it is too hard for us to handle.
+ Similarly, if the exit is not dominating, we cannot determine
+ whether the loop is not infinite. */
+ exit = single_dom_exit (loop);
+ if (!exit)
+ return false;
+
+ /* The loop must be finite. */
+ if (!number_of_iterations_exit (loop, exit, &niter, false))
+ return false;
+
+ /* Values of all loop exit phi nodes must be invariants. */
+ for (phi = phi_nodes (exit->dest); phi; phi = PHI_CHAIN (phi))
+ {
+ if (!is_gimple_reg (PHI_RESULT (phi)))
continue;
- changed |= canonicalize_loop_induction_variables (loops, loop,
- false, true,
- !flag_ivcanon);
+ def = PHI_ARG_DEF_FROM_EDGE (phi, exit);
+
+ if (!expr_invariant_in_loop_p (loop, def))
+ return false;
+ }
+
+ /* And there should be no memory modifying or from other reasons
+ unremovable statements. */
+ body = get_loop_body (loop);
+ for (i = 0; i < loop->num_nodes; i++)
+ {
+ /* Irreducible region might be infinite. */
+ if (body[i]->flags & BB_IRREDUCIBLE_LOOP)
+ {
+ free (body);
+ return false;
+ }
+
+ for (bsi = bsi_start (body[i]); !bsi_end_p (bsi); bsi_next (&bsi))
+ {
+ stmt = bsi_stmt (bsi);
+ if (!ZERO_SSA_OPERANDS (stmt, SSA_OP_VIRTUAL_DEFS)
+ || stmt_ann (stmt)->has_volatile_ops)
+ {
+ free (body);
+ return false;
+ }
+
+ /* Also, asm statements and calls may have side effects and we
+ cannot change the number of times they are executed. */
+ switch (TREE_CODE (stmt))
+ {
+ case RETURN_EXPR:
+ case GIMPLE_MODIFY_STMT:
+ stmt = get_call_expr_in (stmt);
+ if (!stmt)
+ break;
+
+ case CALL_EXPR:
+ if (TREE_SIDE_EFFECTS (stmt))
+ {
+ free (body);
+ return false;
+ }
+ break;
+
+ case ASM_EXPR:
+ /* We cannot remove volatile assembler. */
+ if (ASM_VOLATILE_P (stmt))
+ {
+ free (body);
+ return false;
+ }
+ break;
+
+ default:
+ break;
+ }
+ }
+ }
+ free (body);
+
+ return true;
+}
+
+/* Remove LOOP by making it exit in the first iteration. */
+
+static void
+remove_empty_loop (struct loop *loop)
+{
+ edge exit = single_dom_exit (loop), non_exit;
+ tree cond_stmt = last_stmt (exit->src);
+ tree do_exit;
+ basic_block *body;
+ unsigned n_before, freq_in, freq_h;
+ gcov_type exit_count = exit->count;
+
+ if (dump_file)
+ fprintf (dump_file, "Removing empty loop %d\n", loop->num);
+
+ non_exit = EDGE_SUCC (exit->src, 0);
+ if (non_exit == exit)
+ non_exit = EDGE_SUCC (exit->src, 1);
+
+ if (exit->flags & EDGE_TRUE_VALUE)
+ do_exit = boolean_true_node;
+ else
+ do_exit = boolean_false_node;
+
+ COND_EXPR_COND (cond_stmt) = do_exit;
+ update_stmt (cond_stmt);
+
+ /* Let us set the probabilities of the edges coming from the exit block. */
+ exit->probability = REG_BR_PROB_BASE;
+ non_exit->probability = 0;
+ non_exit->count = 0;
+
+ /* Update frequencies and counts. Everything before
+ the exit needs to be scaled FREQ_IN/FREQ_H times,
+ where FREQ_IN is the frequency of the entry edge
+ and FREQ_H is the frequency of the loop header.
+ Everything after the exit has zero frequency. */
+ freq_h = loop->header->frequency;
+ freq_in = EDGE_FREQUENCY (loop_preheader_edge (loop));
+ if (freq_h != 0)
+ {
+ body = get_loop_body_in_dom_order (loop);
+ for (n_before = 1; n_before <= loop->num_nodes; n_before++)
+ if (body[n_before - 1] == exit->src)
+ break;
+ scale_bbs_frequencies_int (body, n_before, freq_in, freq_h);
+ scale_bbs_frequencies_int (body + n_before, loop->num_nodes - n_before,
+ 0, 1);
+ free (body);
}
-#if 0
- /* The necessary infrastructure is not in yet. */
+ /* Number of executions of exit is not changed, thus we need to restore
+ the original value. */
+ exit->count = exit_count;
+}
+
+/* Removes LOOP if it is empty. Returns true if LOOP is removed. CHANGED
+ is set to true if LOOP or any of its subloops is removed. */
+
+static bool
+try_remove_empty_loop (struct loop *loop, bool *changed)
+{
+ bool nonempty_subloop = false;
+ struct loop *sub;
+
+ /* First, all subloops must be removed. */
+ for (sub = loop->inner; sub; sub = sub->next)
+ nonempty_subloop |= !try_remove_empty_loop (sub, changed);
+
+ if (nonempty_subloop || !empty_loop_p (loop))
+ return false;
+
+ remove_empty_loop (loop);
+ *changed = true;
+ return true;
+}
+
+/* Remove the empty loops. */
+
+unsigned int
+remove_empty_loops (void)
+{
+ bool changed = false;
+ struct loop *loop;
+
+ for (loop = current_loops->tree_root->inner; loop; loop = loop->next)
+ try_remove_empty_loop (loop, &changed);
+
if (changed)
- cleanup_tree_cfg_loop ();
-#endif
+ {
+ scev_reset ();
+ return TODO_cleanup_cfg;
+ }
+ return 0;
}
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