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. */
+Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301, USA. */
/* 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. */
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),
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. */
return size;
}
+/* 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. 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. */
+ loop tree. 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,
edge exit, tree niter,
- bool completely_unroll)
+ enum unroll_level ul)
{
- unsigned HOST_WIDE_INT n_unroll, ninsns, max_unroll;
+ unsigned HOST_WIDE_INT n_unroll, ninsns, max_unroll, unr_insns;
tree old_cond, cond, dont_exit, do_exit;
if (loop->inner)
if (n_unroll)
{
- if (!completely_unroll)
+ if (ul == UL_SINGLE_ITER)
return false;
ninsns = tree_num_loop_insns (loop);
if (n_unroll * ninsns
> (unsigned) PARAM_VALUE (PARAM_MAX_COMPLETELY_PEELED_INSNS))
return false;
+
+ 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;
+ }
+ }
}
if (exit->flags & EDGE_TRUE_VALUE)
if (n_unroll)
{
- if (!flag_unroll_loops)
- return false;
+ sbitmap wont_exit;
+ edge *edges_to_remove = xmalloc (sizeof (edge *) * n_unroll);
+ unsigned int n_to_remove = 0;
old_cond = COND_EXPR_COND (cond);
COND_EXPR_COND (cond) = dont_exit;
- modify_stmt (cond);
+ update_stmt (cond);
+ initialize_original_copy_tables ();
+
+ wont_exit = sbitmap_alloc (n_unroll + 1);
+ sbitmap_ones (wont_exit);
+ RESET_BIT (wont_exit, 0);
if (!tree_duplicate_loop_to_header_edge (loop, loop_preheader_edge (loop),
- loops, n_unroll, NULL,
- NULL, NULL, NULL, 0))
+ loops, n_unroll, wont_exit,
+ exit, edges_to_remove,
+ &n_to_remove,
+ DLTHE_FLAG_UPDATE_FREQ
+ | DLTHE_FLAG_COMPLETTE_PEEL))
{
COND_EXPR_COND (cond) = old_cond;
+ update_stmt (cond);
+ free_original_copy_tables ();
+ free (wont_exit);
+ free (edges_to_remove);
return false;
}
+ free (wont_exit);
+ free (edges_to_remove);
+ free_original_copy_tables ();
}
COND_EXPR_COND (cond) = do_exit;
- modify_stmt (cond);
+ 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);
}
/* 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. */
+ tree. 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,
+ bool create_iv, enum unroll_level ul,
bool try_eval)
{
edge exit = NULL;
/* 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)));
+ niter = fold_build2 (MINUS_EXPR, TREE_TYPE (niter), niter,
+ build_int_cst (TREE_TYPE (niter), 1));
}
else
{
fprintf (dump_file, " times.\n");
}
- if (try_unroll_loop_completely (loops, loop, exit, niter, completely_unroll))
+ if (try_unroll_loop_completely (loops, loop, exit, niter, ul))
return true;
if (create_iv)
if (loop)
changed |= canonicalize_loop_induction_variables (loops, loop,
- true, false, true);
+ true, UL_SINGLE_ITER,
+ true);
}
/* Clean up the information about numbers of iterations, since brute force
cleanup_tree_cfg_loop ();
}
-/* 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)
+tree_unroll_loops_completely (struct loops *loops, bool may_increase_size)
{
unsigned i;
struct loop *loop;
bool changed = false;
+ enum unroll_level ul;
for (i = 1; i < loops->num; i++)
{
if (!loop)
continue;
+ if (may_increase_size && maybe_hot_bb_p (loop->header))
+ ul = UL_ALL;
+ else
+ ul = UL_NO_GROWTH;
changed |= canonicalize_loop_induction_variables (loops, loop,
- false, true,
+ false, ul,
!flag_tree_loop_ivcanon);
}
if (changed)
cleanup_tree_cfg_loop ();
}
+
+/* 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 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;
+
+ 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 MODIFY_EXPR:
+ 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;
+
+ 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);
+ }
+
+ /* 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. */
+
+void
+remove_empty_loops (struct loops *loops)
+{
+ bool changed = false;
+ struct loop *loop;
+
+ for (loop = loops->tree_root->inner; loop; loop = loop->next)
+ try_remove_empty_loop (loop, &changed);
+
+ if (changed)
+ {
+ scev_reset ();
+ cleanup_tree_cfg_loop ();
+ }
+}
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