/* Basic block reordering routines for the GNU compiler.
- Copyright (C) 2000, 2002 Free Software Foundation, Inc.
+ Copyright (C) 2000, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
This file is part of GCC.
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. */
-
-/* References:
-
- "Profile Guided Code Positioning"
- Pettis and Hanson; PLDI '90.
-
- TODO:
-
- (1) Consider:
-
- if (p) goto A; // predict taken
- foo ();
- A:
- if (q) goto B; // predict taken
- bar ();
- B:
- baz ();
- return;
-
- We'll currently reorder this as
-
- if (!p) goto C;
- A:
- if (!q) goto D;
- B:
- baz ();
- return;
- D:
- bar ();
- goto B;
- C:
- foo ();
- goto A;
-
- A better ordering is
-
- if (!p) goto C;
- if (!q) goto D;
- B:
- baz ();
- return;
- C:
- foo ();
- if (q) goto B;
- D:
- bar ();
- goto B;
-
- This requires that we be able to duplicate the jump at A, and
- adjust the graph traversal such that greedy placement doesn't
- fix D before C is considered.
-
- (2) Coordinate with shorten_branches to minimize the number of
- long branches.
-
- (3) Invent a method by which sufficiently non-predicted code can
- be moved to either the end of the section or another section
- entirely. Some sort of NOTE_INSN note would work fine.
-
- This completely scroggs all debugging formats, so the user
- would have to explicitly ask for it.
+ Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
+ 02110-1301, USA. */
+
+/* This (greedy) algorithm constructs traces in several rounds.
+ The construction starts from "seeds". The seed for the first round
+ is the entry point of function. When there are more than one seed
+ that one is selected first that has the lowest key in the heap
+ (see function bb_to_key). Then the algorithm repeatedly adds the most
+ probable successor to the end of a trace. Finally it connects the traces.
+
+ There are two parameters: Branch Threshold and Exec Threshold.
+ If the edge to a successor of the actual basic block is lower than
+ Branch Threshold or the frequency of the successor is lower than
+ Exec Threshold the successor will be the seed in one of the next rounds.
+ Each round has these parameters lower than the previous one.
+ The last round has to have these parameters set to zero
+ so that the remaining blocks are picked up.
+
+ The algorithm selects the most probable successor from all unvisited
+ successors and successors that have been added to this trace.
+ The other successors (that has not been "sent" to the next round) will be
+ other seeds for this round and the secondary traces will start in them.
+ If the successor has not been visited in this trace it is added to the trace
+ (however, there is some heuristic for simple branches).
+ If the successor has been visited in this trace the loop has been found.
+ If the loop has many iterations the loop is rotated so that the
+ source block of the most probable edge going out from the loop
+ is the last block of the trace.
+ If the loop has few iterations and there is no edge from the last block of
+ the loop going out from loop the loop header is duplicated.
+ Finally, the construction of the trace is terminated.
+
+ When connecting traces it first checks whether there is an edge from the
+ last block of one trace to the first block of another trace.
+ When there are still some unconnected traces it checks whether there exists
+ a basic block BB such that BB is a successor of the last bb of one trace
+ and BB is a predecessor of the first block of another trace. In this case,
+ BB is duplicated and the traces are connected through this duplicate.
+ The rest of traces are simply connected so there will be a jump to the
+ beginning of the rest of trace.
+
+
+ References:
+
+ "Software Trace Cache"
+ A. Ramirez, J. Larriba-Pey, C. Navarro, J. Torrellas and M. Valero; 1999
+ http://citeseer.nj.nec.com/15361.html
+
*/
#include "config.h"
#include "system.h"
-#include "tree.h"
+#include "coretypes.h"
+#include "tm.h"
#include "rtl.h"
-#include "hard-reg-set.h"
-#include "basic-block.h"
+#include "regs.h"
#include "flags.h"
+#include "timevar.h"
#include "output.h"
#include "cfglayout.h"
+#include "fibheap.h"
#include "target.h"
+#include "function.h"
+#include "tm_p.h"
+#include "obstack.h"
+#include "expr.h"
+#include "params.h"
+#include "toplev.h"
+#include "tree-pass.h"
+
+#ifndef HAVE_conditional_execution
+#define HAVE_conditional_execution 0
+#endif
+
+/* The number of rounds. In most cases there will only be 4 rounds, but
+ when partitioning hot and cold basic blocks into separate sections of
+ the .o file there will be an extra round.*/
+#define N_ROUNDS 5
+
+/* Stubs in case we don't have a return insn.
+ We have to check at runtime too, not only compiletime. */
+
+#ifndef HAVE_return
+#define HAVE_return 0
+#define gen_return() NULL_RTX
+#endif
+
+
+/* Branch thresholds in thousandths (per mille) of the REG_BR_PROB_BASE. */
+static int branch_threshold[N_ROUNDS] = {400, 200, 100, 0, 0};
+
+/* Exec thresholds in thousandths (per mille) of the frequency of bb 0. */
+static int exec_threshold[N_ROUNDS] = {500, 200, 50, 0, 0};
+
+/* If edge frequency is lower than DUPLICATION_THRESHOLD per mille of entry
+ block the edge destination is not duplicated while connecting traces. */
+#define DUPLICATION_THRESHOLD 100
+
+/* Length of unconditional jump instruction. */
+static int uncond_jump_length;
+
+/* Structure to hold needed information for each basic block. */
+typedef struct bbro_basic_block_data_def
+{
+ /* Which trace is the bb start of (-1 means it is not a start of a trace). */
+ int start_of_trace;
+
+ /* Which trace is the bb end of (-1 means it is not an end of a trace). */
+ int end_of_trace;
+
+ /* Which trace is the bb in? */
+ int in_trace;
+
+ /* Which heap is BB in (if any)? */
+ fibheap_t heap;
+
+ /* Which heap node is BB in (if any)? */
+ fibnode_t node;
+} bbro_basic_block_data;
+
+/* The current size of the following dynamic array. */
+static int array_size;
+
+/* The array which holds needed information for basic blocks. */
+static bbro_basic_block_data *bbd;
+
+/* To avoid frequent reallocation the size of arrays is greater than needed,
+ the number of elements is (not less than) 1.25 * size_wanted. */
+#define GET_ARRAY_SIZE(X) ((((X) / 4) + 1) * 5)
+
+/* Free the memory and set the pointer to NULL. */
+#define FREE(P) (gcc_assert (P), free (P), P = 0)
+
+/* Structure for holding information about a trace. */
+struct trace
+{
+ /* First and last basic block of the trace. */
+ basic_block first, last;
+
+ /* The round of the STC creation which this trace was found in. */
+ int round;
+
+ /* The length (i.e. the number of basic blocks) of the trace. */
+ int length;
+};
+
+/* Maximum frequency and count of one of the entry blocks. */
+static int max_entry_frequency;
+static gcov_type max_entry_count;
/* Local function prototypes. */
-static void make_reorder_chain PARAMS ((void));
-static basic_block make_reorder_chain_1 PARAMS ((basic_block, basic_block));
+static void find_traces (int *, struct trace *);
+static basic_block rotate_loop (edge, struct trace *, int);
+static void mark_bb_visited (basic_block, int);
+static void find_traces_1_round (int, int, gcov_type, struct trace *, int *,
+ int, fibheap_t *, int);
+static basic_block copy_bb (basic_block, edge, basic_block, int);
+static fibheapkey_t bb_to_key (basic_block);
+static bool better_edge_p (basic_block, edge, int, int, int, int, edge);
+static void connect_traces (int, struct trace *);
+static bool copy_bb_p (basic_block, int);
+static int get_uncond_jump_length (void);
+static bool push_to_next_round_p (basic_block, int, int, int, gcov_type);
+static void find_rarely_executed_basic_blocks_and_crossing_edges (edge *,
+ int *,
+ int *);
+static void add_labels_and_missing_jumps (edge *, int);
+static void add_reg_crossing_jump_notes (void);
+static void fix_up_fall_thru_edges (void);
+static void fix_edges_for_rarely_executed_code (edge *, int);
+static void fix_crossing_conditional_branches (void);
+static void fix_crossing_unconditional_branches (void);
\f
-/* Compute an ordering for a subgraph beginning with block BB. Record the
- ordering in RBI()->index and chained through RBI()->next. */
+/* Check to see if bb should be pushed into the next round of trace
+ collections or not. Reasons for pushing the block forward are 1).
+ If the block is cold, we are doing partitioning, and there will be
+ another round (cold partition blocks are not supposed to be
+ collected into traces until the very last round); or 2). There will
+ be another round, and the basic block is not "hot enough" for the
+ current round of trace collection. */
+
+static bool
+push_to_next_round_p (basic_block bb, int round, int number_of_rounds,
+ int exec_th, gcov_type count_th)
+{
+ bool there_exists_another_round;
+ bool block_not_hot_enough;
+
+ there_exists_another_round = round < number_of_rounds - 1;
+
+ block_not_hot_enough = (bb->frequency < exec_th
+ || bb->count < count_th
+ || probably_never_executed_bb_p (bb));
+
+ if (there_exists_another_round
+ && block_not_hot_enough)
+ return true;
+ else
+ return false;
+}
+
+/* Find the traces for Software Trace Cache. Chain each trace through
+ RBI()->next. Store the number of traces to N_TRACES and description of
+ traces to TRACES. */
static void
-make_reorder_chain ()
+find_traces (int *n_traces, struct trace *traces)
{
- basic_block prev = NULL;
- int nbb_m1 = n_basic_blocks - 1;
- basic_block next;
+ int i;
+ int number_of_rounds;
+ edge e;
+ edge_iterator ei;
+ fibheap_t heap;
- /* Loop until we've placed every block. */
- do
+ /* Add one extra round of trace collection when partitioning hot/cold
+ basic blocks into separate sections. The last round is for all the
+ cold blocks (and ONLY the cold blocks). */
+
+ number_of_rounds = N_ROUNDS - 1;
+
+ /* Insert entry points of function into heap. */
+ heap = fibheap_new ();
+ max_entry_frequency = 0;
+ max_entry_count = 0;
+ FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR->succs)
{
- int i;
+ bbd[e->dest->index].heap = heap;
+ bbd[e->dest->index].node = fibheap_insert (heap, bb_to_key (e->dest),
+ e->dest);
+ if (e->dest->frequency > max_entry_frequency)
+ max_entry_frequency = e->dest->frequency;
+ if (e->dest->count > max_entry_count)
+ max_entry_count = e->dest->count;
+ }
- next = NULL;
+ /* Find the traces. */
+ for (i = 0; i < number_of_rounds; i++)
+ {
+ gcov_type count_threshold;
- /* Find the next unplaced block. */
- /* ??? Get rid of this loop, and track which blocks are not yet
- placed more directly, so as to avoid the O(N^2) worst case.
- Perhaps keep a doubly-linked list of all to-be-placed blocks;
- remove from the list as we place. The head of that list is
- what we're looking for here. */
+ if (dump_file)
+ fprintf (dump_file, "STC - round %d\n", i + 1);
- for (i = 0; i <= nbb_m1 && !next; ++i)
+ if (max_entry_count < INT_MAX / 1000)
+ count_threshold = max_entry_count * exec_threshold[i] / 1000;
+ else
+ count_threshold = max_entry_count / 1000 * exec_threshold[i];
+
+ find_traces_1_round (REG_BR_PROB_BASE * branch_threshold[i] / 1000,
+ max_entry_frequency * exec_threshold[i] / 1000,
+ count_threshold, traces, n_traces, i, &heap,
+ number_of_rounds);
+ }
+ fibheap_delete (heap);
+
+ if (dump_file)
+ {
+ for (i = 0; i < *n_traces; i++)
{
- basic_block bb = BASIC_BLOCK (i);
- if (! RBI (bb)->visited)
- next = bb;
+ basic_block bb;
+ fprintf (dump_file, "Trace %d (round %d): ", i + 1,
+ traces[i].round + 1);
+ for (bb = traces[i].first; bb != traces[i].last; bb = bb->aux)
+ fprintf (dump_file, "%d [%d] ", bb->index, bb->frequency);
+ fprintf (dump_file, "%d [%d]\n", bb->index, bb->frequency);
}
- if (next)
- prev = make_reorder_chain_1 (next, prev);
+ fflush (dump_file);
}
- while (next);
- RBI (prev)->next = NULL;
}
-/* A helper function for make_reorder_chain.
+/* Rotate loop whose back edge is BACK_EDGE in the tail of trace TRACE
+ (with sequential number TRACE_N). */
+
+static basic_block
+rotate_loop (edge back_edge, struct trace *trace, int trace_n)
+{
+ basic_block bb;
+
+ /* Information about the best end (end after rotation) of the loop. */
+ basic_block best_bb = NULL;
+ edge best_edge = NULL;
+ int best_freq = -1;
+ gcov_type best_count = -1;
+ /* The best edge is preferred when its destination is not visited yet
+ or is a start block of some trace. */
+ bool is_preferred = false;
+
+ /* Find the most frequent edge that goes out from current trace. */
+ bb = back_edge->dest;
+ do
+ {
+ edge e;
+ edge_iterator ei;
+
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ if (e->dest != EXIT_BLOCK_PTR
+ && e->dest->il.rtl->visited != trace_n
+ && (e->flags & EDGE_CAN_FALLTHRU)
+ && !(e->flags & EDGE_COMPLEX))
+ {
+ if (is_preferred)
+ {
+ /* The best edge is preferred. */
+ if (!e->dest->il.rtl->visited
+ || bbd[e->dest->index].start_of_trace >= 0)
+ {
+ /* The current edge E is also preferred. */
+ int freq = EDGE_FREQUENCY (e);
+ if (freq > best_freq || e->count > best_count)
+ {
+ best_freq = freq;
+ best_count = e->count;
+ best_edge = e;
+ best_bb = bb;
+ }
+ }
+ }
+ else
+ {
+ if (!e->dest->il.rtl->visited
+ || bbd[e->dest->index].start_of_trace >= 0)
+ {
+ /* The current edge E is preferred. */
+ is_preferred = true;
+ best_freq = EDGE_FREQUENCY (e);
+ best_count = e->count;
+ best_edge = e;
+ best_bb = bb;
+ }
+ else
+ {
+ int freq = EDGE_FREQUENCY (e);
+ if (!best_edge || freq > best_freq || e->count > best_count)
+ {
+ best_freq = freq;
+ best_count = e->count;
+ best_edge = e;
+ best_bb = bb;
+ }
+ }
+ }
+ }
+ bb = bb->aux;
+ }
+ while (bb != back_edge->dest);
+
+ if (best_bb)
+ {
+ /* Rotate the loop so that the BEST_EDGE goes out from the last block of
+ the trace. */
+ if (back_edge->dest == trace->first)
+ {
+ trace->first = best_bb->aux;
+ }
+ else
+ {
+ basic_block prev_bb;
+
+ for (prev_bb = trace->first;
+ prev_bb->aux != back_edge->dest;
+ prev_bb = prev_bb->aux)
+ ;
+ prev_bb->aux = best_bb->aux;
+
+ /* Try to get rid of uncond jump to cond jump. */
+ if (single_succ_p (prev_bb))
+ {
+ basic_block header = single_succ (prev_bb);
+
+ /* Duplicate HEADER if it is a small block containing cond jump
+ in the end. */
+ if (any_condjump_p (BB_END (header)) && copy_bb_p (header, 0)
+ && !find_reg_note (BB_END (header), REG_CROSSING_JUMP,
+ NULL_RTX))
+ copy_bb (header, single_succ_edge (prev_bb), prev_bb, trace_n);
+ }
+ }
+ }
+ else
+ {
+ /* We have not found suitable loop tail so do no rotation. */
+ best_bb = back_edge->src;
+ }
+ best_bb->aux = NULL;
+ return best_bb;
+}
+
+/* This function marks BB that it was visited in trace number TRACE. */
+
+static void
+mark_bb_visited (basic_block bb, int trace)
+{
+ bb->il.rtl->visited = trace;
+ if (bbd[bb->index].heap)
+ {
+ fibheap_delete_node (bbd[bb->index].heap, bbd[bb->index].node);
+ bbd[bb->index].heap = NULL;
+ bbd[bb->index].node = NULL;
+ }
+}
+
+/* One round of finding traces. Find traces for BRANCH_TH and EXEC_TH i.e. do
+ not include basic blocks their probability is lower than BRANCH_TH or their
+ frequency is lower than EXEC_TH into traces (or count is lower than
+ COUNT_TH). It stores the new traces into TRACES and modifies the number of
+ traces *N_TRACES. Sets the round (which the trace belongs to) to ROUND. It
+ expects that starting basic blocks are in *HEAP and at the end it deletes
+ *HEAP and stores starting points for the next round into new *HEAP. */
+
+static void
+find_traces_1_round (int branch_th, int exec_th, gcov_type count_th,
+ struct trace *traces, int *n_traces, int round,
+ fibheap_t *heap, int number_of_rounds)
+{
+ /* Heap for discarded basic blocks which are possible starting points for
+ the next round. */
+ fibheap_t new_heap = fibheap_new ();
+
+ while (!fibheap_empty (*heap))
+ {
+ basic_block bb;
+ struct trace *trace;
+ edge best_edge, e;
+ fibheapkey_t key;
+ edge_iterator ei;
+
+ bb = fibheap_extract_min (*heap);
+ bbd[bb->index].heap = NULL;
+ bbd[bb->index].node = NULL;
+
+ if (dump_file)
+ fprintf (dump_file, "Getting bb %d\n", bb->index);
+
+ /* If the BB's frequency is too low send BB to the next round. When
+ partitioning hot/cold blocks into separate sections, make sure all
+ the cold blocks (and ONLY the cold blocks) go into the (extra) final
+ round. */
+
+ if (push_to_next_round_p (bb, round, number_of_rounds, exec_th,
+ count_th))
+ {
+ int key = bb_to_key (bb);
+ bbd[bb->index].heap = new_heap;
+ bbd[bb->index].node = fibheap_insert (new_heap, key, bb);
+
+ if (dump_file)
+ fprintf (dump_file,
+ " Possible start point of next round: %d (key: %d)\n",
+ bb->index, key);
+ continue;
+ }
+
+ trace = traces + *n_traces;
+ trace->first = bb;
+ trace->round = round;
+ trace->length = 0;
+ bbd[bb->index].in_trace = *n_traces;
+ (*n_traces)++;
+
+ do
+ {
+ int prob, freq;
+ bool ends_in_call;
+
+ /* The probability and frequency of the best edge. */
+ int best_prob = INT_MIN / 2;
+ int best_freq = INT_MIN / 2;
+
+ best_edge = NULL;
+ mark_bb_visited (bb, *n_traces);
+ trace->length++;
+
+ if (dump_file)
+ fprintf (dump_file, "Basic block %d was visited in trace %d\n",
+ bb->index, *n_traces - 1);
+
+ ends_in_call = block_ends_with_call_p (bb);
+
+ /* Select the successor that will be placed after BB. */
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ {
+ gcc_assert (!(e->flags & EDGE_FAKE));
- We do not follow EH edges, or non-fallthru edges to noreturn blocks.
- These are assumed to be the error condition and we wish to cluster
- all of them at the very end of the function for the benefit of cache
- locality for the rest of the function.
+ if (e->dest == EXIT_BLOCK_PTR)
+ continue;
- ??? We could do slightly better by noticing earlier that some subgraph
- has all paths leading to noreturn functions, but for there to be more
- than one block in such a subgraph is rare. */
+ if (e->dest->il.rtl->visited
+ && e->dest->il.rtl->visited != *n_traces)
+ continue;
+
+ if (BB_PARTITION (e->dest) != BB_PARTITION (bb))
+ continue;
+
+ prob = e->probability;
+ freq = e->dest->frequency;
+
+ /* The only sensible preference for a call instruction is the
+ fallthru edge. Don't bother selecting anything else. */
+ if (ends_in_call)
+ {
+ if (e->flags & EDGE_CAN_FALLTHRU)
+ {
+ best_edge = e;
+ best_prob = prob;
+ best_freq = freq;
+ }
+ continue;
+ }
+
+ /* Edge that cannot be fallthru or improbable or infrequent
+ successor (i.e. it is unsuitable successor). */
+ if (!(e->flags & EDGE_CAN_FALLTHRU) || (e->flags & EDGE_COMPLEX)
+ || prob < branch_th || EDGE_FREQUENCY (e) < exec_th
+ || e->count < count_th)
+ continue;
+
+ /* If partitioning hot/cold basic blocks, don't consider edges
+ that cross section boundaries. */
+
+ if (better_edge_p (bb, e, prob, freq, best_prob, best_freq,
+ best_edge))
+ {
+ best_edge = e;
+ best_prob = prob;
+ best_freq = freq;
+ }
+ }
+
+ /* If the best destination has multiple predecessors, and can be
+ duplicated cheaper than a jump, don't allow it to be added
+ to a trace. We'll duplicate it when connecting traces. */
+ if (best_edge && EDGE_COUNT (best_edge->dest->preds) >= 2
+ && copy_bb_p (best_edge->dest, 0))
+ best_edge = NULL;
+
+ /* Add all non-selected successors to the heaps. */
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ {
+ if (e == best_edge
+ || e->dest == EXIT_BLOCK_PTR
+ || e->dest->il.rtl->visited)
+ continue;
+
+ key = bb_to_key (e->dest);
+
+ if (bbd[e->dest->index].heap)
+ {
+ /* E->DEST is already in some heap. */
+ if (key != bbd[e->dest->index].node->key)
+ {
+ if (dump_file)
+ {
+ fprintf (dump_file,
+ "Changing key for bb %d from %ld to %ld.\n",
+ e->dest->index,
+ (long) bbd[e->dest->index].node->key,
+ key);
+ }
+ fibheap_replace_key (bbd[e->dest->index].heap,
+ bbd[e->dest->index].node, key);
+ }
+ }
+ else
+ {
+ fibheap_t which_heap = *heap;
+
+ prob = e->probability;
+ freq = EDGE_FREQUENCY (e);
+
+ if (!(e->flags & EDGE_CAN_FALLTHRU)
+ || (e->flags & EDGE_COMPLEX)
+ || prob < branch_th || freq < exec_th
+ || e->count < count_th)
+ {
+ /* When partitioning hot/cold basic blocks, make sure
+ the cold blocks (and only the cold blocks) all get
+ pushed to the last round of trace collection. */
+
+ if (push_to_next_round_p (e->dest, round,
+ number_of_rounds,
+ exec_th, count_th))
+ which_heap = new_heap;
+ }
+
+ bbd[e->dest->index].heap = which_heap;
+ bbd[e->dest->index].node = fibheap_insert (which_heap,
+ key, e->dest);
+
+ if (dump_file)
+ {
+ fprintf (dump_file,
+ " Possible start of %s round: %d (key: %ld)\n",
+ (which_heap == new_heap) ? "next" : "this",
+ e->dest->index, (long) key);
+ }
+
+ }
+ }
+
+ if (best_edge) /* Suitable successor was found. */
+ {
+ if (best_edge->dest->il.rtl->visited == *n_traces)
+ {
+ /* We do nothing with one basic block loops. */
+ if (best_edge->dest != bb)
+ {
+ if (EDGE_FREQUENCY (best_edge)
+ > 4 * best_edge->dest->frequency / 5)
+ {
+ /* The loop has at least 4 iterations. If the loop
+ header is not the first block of the function
+ we can rotate the loop. */
+
+ if (best_edge->dest != ENTRY_BLOCK_PTR->next_bb)
+ {
+ if (dump_file)
+ {
+ fprintf (dump_file,
+ "Rotating loop %d - %d\n",
+ best_edge->dest->index, bb->index);
+ }
+ bb->aux = best_edge->dest;
+ bbd[best_edge->dest->index].in_trace =
+ (*n_traces) - 1;
+ bb = rotate_loop (best_edge, trace, *n_traces);
+ }
+ }
+ else
+ {
+ /* The loop has less than 4 iterations. */
+
+ if (single_succ_p (bb)
+ && copy_bb_p (best_edge->dest, !optimize_size))
+ {
+ bb = copy_bb (best_edge->dest, best_edge, bb,
+ *n_traces);
+ trace->length++;
+ }
+ }
+ }
+
+ /* Terminate the trace. */
+ break;
+ }
+ else
+ {
+ /* Check for a situation
+
+ A
+ /|
+ B |
+ \|
+ C
+
+ where
+ EDGE_FREQUENCY (AB) + EDGE_FREQUENCY (BC)
+ >= EDGE_FREQUENCY (AC).
+ (i.e. 2 * B->frequency >= EDGE_FREQUENCY (AC) )
+ Best ordering is then A B C.
+
+ This situation is created for example by:
+
+ if (A) B;
+ C;
+
+ */
+
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ if (e != best_edge
+ && (e->flags & EDGE_CAN_FALLTHRU)
+ && !(e->flags & EDGE_COMPLEX)
+ && !e->dest->il.rtl->visited
+ && single_pred_p (e->dest)
+ && !(e->flags & EDGE_CROSSING)
+ && single_succ_p (e->dest)
+ && (single_succ_edge (e->dest)->flags
+ & EDGE_CAN_FALLTHRU)
+ && !(single_succ_edge (e->dest)->flags & EDGE_COMPLEX)
+ && single_succ (e->dest) == best_edge->dest
+ && 2 * e->dest->frequency >= EDGE_FREQUENCY (best_edge))
+ {
+ best_edge = e;
+ if (dump_file)
+ fprintf (dump_file, "Selecting BB %d\n",
+ best_edge->dest->index);
+ break;
+ }
+
+ bb->aux = best_edge->dest;
+ bbd[best_edge->dest->index].in_trace = (*n_traces) - 1;
+ bb = best_edge->dest;
+ }
+ }
+ }
+ while (best_edge);
+ trace->last = bb;
+ bbd[trace->first->index].start_of_trace = *n_traces - 1;
+ bbd[trace->last->index].end_of_trace = *n_traces - 1;
+
+ /* The trace is terminated so we have to recount the keys in heap
+ (some block can have a lower key because now one of its predecessors
+ is an end of the trace). */
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ {
+ if (e->dest == EXIT_BLOCK_PTR
+ || e->dest->il.rtl->visited)
+ continue;
+
+ if (bbd[e->dest->index].heap)
+ {
+ key = bb_to_key (e->dest);
+ if (key != bbd[e->dest->index].node->key)
+ {
+ if (dump_file)
+ {
+ fprintf (dump_file,
+ "Changing key for bb %d from %ld to %ld.\n",
+ e->dest->index,
+ (long) bbd[e->dest->index].node->key, key);
+ }
+ fibheap_replace_key (bbd[e->dest->index].heap,
+ bbd[e->dest->index].node,
+ key);
+ }
+ }
+ }
+ }
+
+ fibheap_delete (*heap);
+
+ /* "Return" the new heap. */
+ *heap = new_heap;
+}
+
+/* Create a duplicate of the basic block OLD_BB and redirect edge E to it, add
+ it to trace after BB, mark OLD_BB visited and update pass' data structures
+ (TRACE is a number of trace which OLD_BB is duplicated to). */
static basic_block
-make_reorder_chain_1 (bb, prev)
- basic_block bb;
- basic_block prev;
+copy_bb (basic_block old_bb, edge e, basic_block bb, int trace)
+{
+ basic_block new_bb;
+
+ new_bb = duplicate_block (old_bb, e, bb);
+ BB_COPY_PARTITION (new_bb, old_bb);
+
+ gcc_assert (e->dest == new_bb);
+ gcc_assert (!e->dest->il.rtl->visited);
+
+ if (dump_file)
+ fprintf (dump_file,
+ "Duplicated bb %d (created bb %d)\n",
+ old_bb->index, new_bb->index);
+ new_bb->il.rtl->visited = trace;
+ new_bb->aux = bb->aux;
+ bb->aux = new_bb;
+
+ if (new_bb->index >= array_size || last_basic_block > array_size)
+ {
+ int i;
+ int new_size;
+
+ new_size = MAX (last_basic_block, new_bb->index + 1);
+ new_size = GET_ARRAY_SIZE (new_size);
+ bbd = xrealloc (bbd, new_size * sizeof (bbro_basic_block_data));
+ for (i = array_size; i < new_size; i++)
+ {
+ bbd[i].start_of_trace = -1;
+ bbd[i].in_trace = -1;
+ bbd[i].end_of_trace = -1;
+ bbd[i].heap = NULL;
+ bbd[i].node = NULL;
+ }
+ array_size = new_size;
+
+ if (dump_file)
+ {
+ fprintf (dump_file,
+ "Growing the dynamic array to %d elements.\n",
+ array_size);
+ }
+ }
+
+ bbd[new_bb->index].in_trace = trace;
+
+ return new_bb;
+}
+
+/* Compute and return the key (for the heap) of the basic block BB. */
+
+static fibheapkey_t
+bb_to_key (basic_block bb)
{
edge e;
- basic_block next;
- rtx note;
+ edge_iterator ei;
+ int priority = 0;
- /* Mark this block visited. */
- if (prev)
+ /* Do not start in probably never executed blocks. */
+
+ if (BB_PARTITION (bb) == BB_COLD_PARTITION
+ || probably_never_executed_bb_p (bb))
+ return BB_FREQ_MAX;
+
+ /* Prefer blocks whose predecessor is an end of some trace
+ or whose predecessor edge is EDGE_DFS_BACK. */
+ FOR_EACH_EDGE (e, ei, bb->preds)
{
- restart:
- RBI (prev)->next = bb;
+ if ((e->src != ENTRY_BLOCK_PTR && bbd[e->src->index].end_of_trace >= 0)
+ || (e->flags & EDGE_DFS_BACK))
+ {
+ int edge_freq = EDGE_FREQUENCY (e);
- if (rtl_dump_file && prev->index + 1 != bb->index)
- fprintf (rtl_dump_file, "Reordering block %d after %d\n",
- bb->index, prev->index);
+ if (edge_freq > priority)
+ priority = edge_freq;
+ }
}
+
+ if (priority)
+ /* The block with priority should have significantly lower key. */
+ return -(100 * BB_FREQ_MAX + 100 * priority + bb->frequency);
+ return -bb->frequency;
+}
+
+/* Return true when the edge E from basic block BB is better than the temporary
+ best edge (details are in function). The probability of edge E is PROB. The
+ frequency of the successor is FREQ. The current best probability is
+ BEST_PROB, the best frequency is BEST_FREQ.
+ The edge is considered to be equivalent when PROB does not differ much from
+ BEST_PROB; similarly for frequency. */
+
+static bool
+better_edge_p (basic_block bb, edge e, int prob, int freq, int best_prob,
+ int best_freq, edge cur_best_edge)
+{
+ bool is_better_edge;
+
+ /* The BEST_* values do not have to be best, but can be a bit smaller than
+ maximum values. */
+ int diff_prob = best_prob / 10;
+ int diff_freq = best_freq / 10;
+
+ if (prob > best_prob + diff_prob)
+ /* The edge has higher probability than the temporary best edge. */
+ is_better_edge = true;
+ else if (prob < best_prob - diff_prob)
+ /* The edge has lower probability than the temporary best edge. */
+ is_better_edge = false;
+ else if (freq < best_freq - diff_freq)
+ /* The edge and the temporary best edge have almost equivalent
+ probabilities. The higher frequency of a successor now means
+ that there is another edge going into that successor.
+ This successor has lower frequency so it is better. */
+ is_better_edge = true;
+ else if (freq > best_freq + diff_freq)
+ /* This successor has higher frequency so it is worse. */
+ is_better_edge = false;
+ else if (e->dest->prev_bb == bb)
+ /* The edges have equivalent probabilities and the successors
+ have equivalent frequencies. Select the previous successor. */
+ is_better_edge = true;
else
+ is_better_edge = false;
+
+ /* If we are doing hot/cold partitioning, make sure that we always favor
+ non-crossing edges over crossing edges. */
+
+ if (!is_better_edge
+ && flag_reorder_blocks_and_partition
+ && cur_best_edge
+ && (cur_best_edge->flags & EDGE_CROSSING)
+ && !(e->flags & EDGE_CROSSING))
+ is_better_edge = true;
+
+ return is_better_edge;
+}
+
+/* Connect traces in array TRACES, N_TRACES is the count of traces. */
+
+static void
+connect_traces (int n_traces, struct trace *traces)
+{
+ int i;
+ bool *connected;
+ bool two_passes;
+ int last_trace;
+ int current_pass;
+ int current_partition;
+ int freq_threshold;
+ gcov_type count_threshold;
+
+ freq_threshold = max_entry_frequency * DUPLICATION_THRESHOLD / 1000;
+ if (max_entry_count < INT_MAX / 1000)
+ count_threshold = max_entry_count * DUPLICATION_THRESHOLD / 1000;
+ else
+ count_threshold = max_entry_count / 1000 * DUPLICATION_THRESHOLD;
+
+ connected = xcalloc (n_traces, sizeof (bool));
+ last_trace = -1;
+ current_pass = 1;
+ current_partition = BB_PARTITION (traces[0].first);
+ two_passes = false;
+
+ if (flag_reorder_blocks_and_partition)
+ for (i = 0; i < n_traces && !two_passes; i++)
+ if (BB_PARTITION (traces[0].first)
+ != BB_PARTITION (traces[i].first))
+ two_passes = true;
+
+ for (i = 0; i < n_traces || (two_passes && current_pass == 1) ; i++)
+ {
+ int t = i;
+ int t2;
+ edge e, best;
+ int best_len;
+
+ if (i >= n_traces)
+ {
+ gcc_assert (two_passes && current_pass == 1);
+ i = 0;
+ t = i;
+ current_pass = 2;
+ if (current_partition == BB_HOT_PARTITION)
+ current_partition = BB_COLD_PARTITION;
+ else
+ current_partition = BB_HOT_PARTITION;
+ }
+
+ if (connected[t])
+ continue;
+
+ if (two_passes
+ && BB_PARTITION (traces[t].first) != current_partition)
+ continue;
+
+ connected[t] = true;
+
+ /* Find the predecessor traces. */
+ for (t2 = t; t2 > 0;)
+ {
+ edge_iterator ei;
+ best = NULL;
+ best_len = 0;
+ FOR_EACH_EDGE (e, ei, traces[t2].first->preds)
+ {
+ int si = e->src->index;
+
+ if (e->src != ENTRY_BLOCK_PTR
+ && (e->flags & EDGE_CAN_FALLTHRU)
+ && !(e->flags & EDGE_COMPLEX)
+ && bbd[si].end_of_trace >= 0
+ && !connected[bbd[si].end_of_trace]
+ && (BB_PARTITION (e->src) == current_partition)
+ && (!best
+ || e->probability > best->probability
+ || (e->probability == best->probability
+ && traces[bbd[si].end_of_trace].length > best_len)))
+ {
+ best = e;
+ best_len = traces[bbd[si].end_of_trace].length;
+ }
+ }
+ if (best)
+ {
+ best->src->aux = best->dest;
+ t2 = bbd[best->src->index].end_of_trace;
+ connected[t2] = true;
+
+ if (dump_file)
+ {
+ fprintf (dump_file, "Connection: %d %d\n",
+ best->src->index, best->dest->index);
+ }
+ }
+ else
+ break;
+ }
+
+ if (last_trace >= 0)
+ traces[last_trace].last->aux = traces[t2].first;
+ last_trace = t;
+
+ /* Find the successor traces. */
+ while (1)
+ {
+ /* Find the continuation of the chain. */
+ edge_iterator ei;
+ best = NULL;
+ best_len = 0;
+ FOR_EACH_EDGE (e, ei, traces[t].last->succs)
+ {
+ int di = e->dest->index;
+
+ if (e->dest != EXIT_BLOCK_PTR
+ && (e->flags & EDGE_CAN_FALLTHRU)
+ && !(e->flags & EDGE_COMPLEX)
+ && bbd[di].start_of_trace >= 0
+ && !connected[bbd[di].start_of_trace]
+ && (BB_PARTITION (e->dest) == current_partition)
+ && (!best
+ || e->probability > best->probability
+ || (e->probability == best->probability
+ && traces[bbd[di].start_of_trace].length > best_len)))
+ {
+ best = e;
+ best_len = traces[bbd[di].start_of_trace].length;
+ }
+ }
+
+ if (best)
+ {
+ if (dump_file)
+ {
+ fprintf (dump_file, "Connection: %d %d\n",
+ best->src->index, best->dest->index);
+ }
+ t = bbd[best->dest->index].start_of_trace;
+ traces[last_trace].last->aux = traces[t].first;
+ connected[t] = true;
+ last_trace = t;
+ }
+ else
+ {
+ /* Try to connect the traces by duplication of 1 block. */
+ edge e2;
+ basic_block next_bb = NULL;
+ bool try_copy = false;
+
+ FOR_EACH_EDGE (e, ei, traces[t].last->succs)
+ if (e->dest != EXIT_BLOCK_PTR
+ && (e->flags & EDGE_CAN_FALLTHRU)
+ && !(e->flags & EDGE_COMPLEX)
+ && (!best || e->probability > best->probability))
+ {
+ edge_iterator ei;
+ edge best2 = NULL;
+ int best2_len = 0;
+
+ /* If the destination is a start of a trace which is only
+ one block long, then no need to search the successor
+ blocks of the trace. Accept it. */
+ if (bbd[e->dest->index].start_of_trace >= 0
+ && traces[bbd[e->dest->index].start_of_trace].length
+ == 1)
+ {
+ best = e;
+ try_copy = true;
+ continue;
+ }
+
+ FOR_EACH_EDGE (e2, ei, e->dest->succs)
+ {
+ int di = e2->dest->index;
+
+ if (e2->dest == EXIT_BLOCK_PTR
+ || ((e2->flags & EDGE_CAN_FALLTHRU)
+ && !(e2->flags & EDGE_COMPLEX)
+ && bbd[di].start_of_trace >= 0
+ && !connected[bbd[di].start_of_trace]
+ && (BB_PARTITION (e2->dest) == current_partition)
+ && (EDGE_FREQUENCY (e2) >= freq_threshold)
+ && (e2->count >= count_threshold)
+ && (!best2
+ || e2->probability > best2->probability
+ || (e2->probability == best2->probability
+ && traces[bbd[di].start_of_trace].length
+ > best2_len))))
+ {
+ best = e;
+ best2 = e2;
+ if (e2->dest != EXIT_BLOCK_PTR)
+ best2_len = traces[bbd[di].start_of_trace].length;
+ else
+ best2_len = INT_MAX;
+ next_bb = e2->dest;
+ try_copy = true;
+ }
+ }
+ }
+
+ if (flag_reorder_blocks_and_partition)
+ try_copy = false;
+
+ /* Copy tiny blocks always; copy larger blocks only when the
+ edge is traversed frequently enough. */
+ if (try_copy
+ && copy_bb_p (best->dest,
+ !optimize_size
+ && EDGE_FREQUENCY (best) >= freq_threshold
+ && best->count >= count_threshold))
+ {
+ basic_block new_bb;
+
+ if (dump_file)
+ {
+ fprintf (dump_file, "Connection: %d %d ",
+ traces[t].last->index, best->dest->index);
+ if (!next_bb)
+ fputc ('\n', dump_file);
+ else if (next_bb == EXIT_BLOCK_PTR)
+ fprintf (dump_file, "exit\n");
+ else
+ fprintf (dump_file, "%d\n", next_bb->index);
+ }
+
+ new_bb = copy_bb (best->dest, best, traces[t].last, t);
+ traces[t].last = new_bb;
+ if (next_bb && next_bb != EXIT_BLOCK_PTR)
+ {
+ t = bbd[next_bb->index].start_of_trace;
+ traces[last_trace].last->aux = traces[t].first;
+ connected[t] = true;
+ last_trace = t;
+ }
+ else
+ break; /* Stop finding the successor traces. */
+ }
+ else
+ break; /* Stop finding the successor traces. */
+ }
+ }
+ }
+
+ if (dump_file)
{
- if (bb->index != 0)
- abort ();
+ basic_block bb;
+
+ fprintf (dump_file, "Final order:\n");
+ for (bb = traces[0].first; bb; bb = bb->aux)
+ fprintf (dump_file, "%d ", bb->index);
+ fprintf (dump_file, "\n");
+ fflush (dump_file);
}
- RBI (bb)->visited = 1;
- prev = bb;
- if (bb->succ == NULL)
- return prev;
+ FREE (connected);
+}
+
+/* Return true when BB can and should be copied. CODE_MAY_GROW is true
+ when code size is allowed to grow by duplication. */
+
+static bool
+copy_bb_p (basic_block bb, int code_may_grow)
+{
+ int size = 0;
+ int max_size = uncond_jump_length;
+ rtx insn;
+
+ if (!bb->frequency)
+ return false;
+ if (EDGE_COUNT (bb->preds) < 2)
+ return false;
+ if (!can_duplicate_block_p (bb))
+ return false;
+
+ /* Avoid duplicating blocks which have many successors (PR/13430). */
+ if (EDGE_COUNT (bb->succs) > 8)
+ return false;
+
+ if (code_may_grow && maybe_hot_bb_p (bb))
+ max_size *= PARAM_VALUE (PARAM_MAX_GROW_COPY_BB_INSNS);
- /* Find the most probable block. */
+ FOR_BB_INSNS (bb, insn)
+ {
+ if (INSN_P (insn))
+ size += get_attr_min_length (insn);
+ }
- next = NULL;
- if (any_condjump_p (bb->end)
- && (note = find_reg_note (bb->end, REG_BR_PROB, 0)) != NULL)
+ if (size <= max_size)
+ return true;
+
+ if (dump_file)
{
- int taken, probability;
- edge e_taken, e_fall;
+ fprintf (dump_file,
+ "Block %d can't be copied because its size = %d.\n",
+ bb->index, size);
+ }
- probability = INTVAL (XEXP (note, 0));
- taken = probability > REG_BR_PROB_BASE / 2;
+ return false;
+}
+
+/* Return the length of unconditional jump instruction. */
- /* Find the normal taken edge and the normal fallthru edge.
+static int
+get_uncond_jump_length (void)
+{
+ rtx label, jump;
+ int length;
- Note, conditional jumps with other side effects may not
- be fully optimized. In this case it is possible for
- the conditional jump to branch to the same location as
- the fallthru path.
+ label = emit_label_before (gen_label_rtx (), get_insns ());
+ jump = emit_jump_insn (gen_jump (label));
- We should probably work to improve optimization of that
- case; however, it seems silly not to also deal with such
- problems here if they happen to occur. */
+ length = get_attr_min_length (jump);
+
+ delete_insn (jump);
+ delete_insn (label);
+ return length;
+}
+
+/* Find the basic blocks that are rarely executed and need to be moved to
+ a separate section of the .o file (to cut down on paging and improve
+ cache locality). */
+
+static void
+find_rarely_executed_basic_blocks_and_crossing_edges (edge *crossing_edges,
+ int *n_crossing_edges,
+ int *max_idx)
+{
+ basic_block bb;
+ bool has_hot_blocks = false;
+ edge e;
+ int i;
+ edge_iterator ei;
- e_taken = e_fall = NULL;
- for (e = bb->succ; e ; e = e->succ_next)
+ /* Mark which partition (hot/cold) each basic block belongs in. */
+
+ FOR_EACH_BB (bb)
+ {
+ if (probably_never_executed_bb_p (bb))
+ BB_SET_PARTITION (bb, BB_COLD_PARTITION);
+ else
{
- if (e->flags & EDGE_FALLTHRU)
- e_fall = e;
- else if (! (e->flags & EDGE_EH))
- e_taken = e;
+ BB_SET_PARTITION (bb, BB_HOT_PARTITION);
+ has_hot_blocks = true;
}
+ }
+
+ /* Mark every edge that crosses between sections. */
- next = (taken ? e_taken : e_fall)->dest;
+ i = 0;
+ FOR_EACH_BB (bb)
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ {
+ if (e->src != ENTRY_BLOCK_PTR
+ && e->dest != EXIT_BLOCK_PTR
+ && BB_PARTITION (e->src) != BB_PARTITION (e->dest))
+ {
+ e->flags |= EDGE_CROSSING;
+ if (i == *max_idx)
+ {
+ *max_idx *= 2;
+ crossing_edges = xrealloc (crossing_edges,
+ (*max_idx) * sizeof (edge));
+ }
+ crossing_edges[i++] = e;
+ }
+ else
+ e->flags &= ~EDGE_CROSSING;
}
+ *n_crossing_edges = i;
+}
+
+/* If any destination of a crossing edge does not have a label, add label;
+ Convert any fall-through crossing edges (for blocks that do not contain
+ a jump) to unconditional jumps. */
- /* In the absence of a prediction, disturb things as little as possible
- by selecting the old "next" block from the list of successors. If
- there had been a fallthru edge, that will be the one. */
- if (! next)
+static void
+add_labels_and_missing_jumps (edge *crossing_edges, int n_crossing_edges)
+{
+ int i;
+ basic_block src;
+ basic_block dest;
+ rtx label;
+ rtx barrier;
+ rtx new_jump;
+
+ for (i=0; i < n_crossing_edges; i++)
{
- for (e = bb->succ; e ; e = e->succ_next)
- if (e->dest->index == bb->index + 1)
- {
- if ((e->flags & EDGE_FALLTHRU)
- || (e->dest->succ
- && ! (e->flags & (EDGE_ABNORMAL_CALL | EDGE_EH))))
- next = e->dest;
- break;
- }
+ if (crossing_edges[i])
+ {
+ src = crossing_edges[i]->src;
+ dest = crossing_edges[i]->dest;
+
+ /* Make sure dest has a label. */
+
+ if (dest && (dest != EXIT_BLOCK_PTR))
+ {
+ label = block_label (dest);
+
+ /* Make sure source block ends with a jump. */
+
+ if (src && (src != ENTRY_BLOCK_PTR))
+ {
+ if (!JUMP_P (BB_END (src)))
+ /* bb just falls through. */
+ {
+ /* make sure there's only one successor */
+ gcc_assert (single_succ_p (src));
+
+ /* Find label in dest block. */
+ label = block_label (dest);
+
+ new_jump = emit_jump_insn_after (gen_jump (label),
+ BB_END (src));
+ barrier = emit_barrier_after (new_jump);
+ JUMP_LABEL (new_jump) = label;
+ LABEL_NUSES (label) += 1;
+ src->il.rtl->footer = unlink_insn_chain (barrier, barrier);
+ /* Mark edge as non-fallthru. */
+ crossing_edges[i]->flags &= ~EDGE_FALLTHRU;
+ } /* end: 'if (GET_CODE ... ' */
+ } /* end: 'if (src && src->index...' */
+ } /* end: 'if (dest && dest->index...' */
+ } /* end: 'if (crossing_edges[i]...' */
+ } /* end for loop */
+}
+
+/* Find any bb's where the fall-through edge is a crossing edge (note that
+ these bb's must also contain a conditional jump; we've already
+ dealt with fall-through edges for blocks that didn't have a
+ conditional jump in the call to add_labels_and_missing_jumps).
+ Convert the fall-through edge to non-crossing edge by inserting a
+ new bb to fall-through into. The new bb will contain an
+ unconditional jump (crossing edge) to the original fall through
+ destination. */
+
+static void
+fix_up_fall_thru_edges (void)
+{
+ basic_block cur_bb;
+ basic_block new_bb;
+ edge succ1;
+ edge succ2;
+ edge fall_thru;
+ edge cond_jump = NULL;
+ edge e;
+ bool cond_jump_crosses;
+ int invert_worked;
+ rtx old_jump;
+ rtx fall_thru_label;
+ rtx barrier;
+
+ FOR_EACH_BB (cur_bb)
+ {
+ fall_thru = NULL;
+ if (EDGE_COUNT (cur_bb->succs) > 0)
+ succ1 = EDGE_SUCC (cur_bb, 0);
+ else
+ succ1 = NULL;
+
+ if (EDGE_COUNT (cur_bb->succs) > 1)
+ succ2 = EDGE_SUCC (cur_bb, 1);
+ else
+ succ2 = NULL;
+
+ /* Find the fall-through edge. */
+
+ if (succ1
+ && (succ1->flags & EDGE_FALLTHRU))
+ {
+ fall_thru = succ1;
+ cond_jump = succ2;
+ }
+ else if (succ2
+ && (succ2->flags & EDGE_FALLTHRU))
+ {
+ fall_thru = succ2;
+ cond_jump = succ1;
+ }
+
+ if (fall_thru && (fall_thru->dest != EXIT_BLOCK_PTR))
+ {
+ /* Check to see if the fall-thru edge is a crossing edge. */
+
+ if (fall_thru->flags & EDGE_CROSSING)
+ {
+ /* The fall_thru edge crosses; now check the cond jump edge, if
+ it exists. */
+
+ cond_jump_crosses = true;
+ invert_worked = 0;
+ old_jump = BB_END (cur_bb);
+
+ /* Find the jump instruction, if there is one. */
+
+ if (cond_jump)
+ {
+ if (!(cond_jump->flags & EDGE_CROSSING))
+ cond_jump_crosses = false;
+
+ /* We know the fall-thru edge crosses; if the cond
+ jump edge does NOT cross, and its destination is the
+ next block in the bb order, invert the jump
+ (i.e. fix it so the fall thru does not cross and
+ the cond jump does). */
+
+ if (!cond_jump_crosses
+ && cur_bb->aux == cond_jump->dest)
+ {
+ /* Find label in fall_thru block. We've already added
+ any missing labels, so there must be one. */
+
+ fall_thru_label = block_label (fall_thru->dest);
+
+ if (old_jump && fall_thru_label)
+ invert_worked = invert_jump (old_jump,
+ fall_thru_label,0);
+ if (invert_worked)
+ {
+ fall_thru->flags &= ~EDGE_FALLTHRU;
+ cond_jump->flags |= EDGE_FALLTHRU;
+ update_br_prob_note (cur_bb);
+ e = fall_thru;
+ fall_thru = cond_jump;
+ cond_jump = e;
+ cond_jump->flags |= EDGE_CROSSING;
+ fall_thru->flags &= ~EDGE_CROSSING;
+ }
+ }
+ }
+
+ if (cond_jump_crosses || !invert_worked)
+ {
+ /* This is the case where both edges out of the basic
+ block are crossing edges. Here we will fix up the
+ fall through edge. The jump edge will be taken care
+ of later. */
+
+ new_bb = force_nonfallthru (fall_thru);
+
+ if (new_bb)
+ {
+ new_bb->aux = cur_bb->aux;
+ cur_bb->aux = new_bb;
+
+ /* Make sure new fall-through bb is in same
+ partition as bb it's falling through from. */
+
+ BB_COPY_PARTITION (new_bb, cur_bb);
+ single_succ_edge (new_bb)->flags |= EDGE_CROSSING;
+ }
+
+ /* Add barrier after new jump */
+
+ if (new_bb)
+ {
+ barrier = emit_barrier_after (BB_END (new_bb));
+ new_bb->il.rtl->footer = unlink_insn_chain (barrier,
+ barrier);
+ }
+ else
+ {
+ barrier = emit_barrier_after (BB_END (cur_bb));
+ cur_bb->il.rtl->footer = unlink_insn_chain (barrier,
+ barrier);
+ }
+ }
+ }
+ }
}
+}
- /* Make sure we didn't select a silly next block. */
- if (! next || next == EXIT_BLOCK_PTR || RBI (next)->visited)
- next = NULL;
-
- /* Recurse on the successors. Unroll the last call, as the normal
- case is exactly one or two edges, and we can tail recurse. */
- for (e = bb->succ; e; e = e->succ_next)
- if (e->dest != EXIT_BLOCK_PTR
- && ! RBI (e->dest)->visited
- && e->dest->succ
- && ! (e->flags & (EDGE_ABNORMAL_CALL | EDGE_EH)))
+/* This function checks the destination blockof a "crossing jump" to
+ see if it has any crossing predecessors that begin with a code label
+ and end with an unconditional jump. If so, it returns that predecessor
+ block. (This is to avoid creating lots of new basic blocks that all
+ contain unconditional jumps to the same destination). */
+
+static basic_block
+find_jump_block (basic_block jump_dest)
+{
+ basic_block source_bb = NULL;
+ edge e;
+ rtx insn;
+ edge_iterator ei;
+
+ FOR_EACH_EDGE (e, ei, jump_dest->preds)
+ if (e->flags & EDGE_CROSSING)
{
- if (next)
- {
- prev = make_reorder_chain_1 (next, prev);
- next = RBI (e->dest)->visited ? NULL : e->dest;
- }
- else
- next = e->dest;
+ basic_block src = e->src;
+
+ /* Check each predecessor to see if it has a label, and contains
+ only one executable instruction, which is an unconditional jump.
+ If so, we can use it. */
+
+ if (LABEL_P (BB_HEAD (src)))
+ for (insn = BB_HEAD (src);
+ !INSN_P (insn) && insn != NEXT_INSN (BB_END (src));
+ insn = NEXT_INSN (insn))
+ {
+ if (INSN_P (insn)
+ && insn == BB_END (src)
+ && JUMP_P (insn)
+ && !any_condjump_p (insn))
+ {
+ source_bb = src;
+ break;
+ }
+ }
+
+ if (source_bb)
+ break;
}
- if (next)
+
+ return source_bb;
+}
+
+/* Find all BB's with conditional jumps that are crossing edges;
+ insert a new bb and make the conditional jump branch to the new
+ bb instead (make the new bb same color so conditional branch won't
+ be a 'crossing' edge). Insert an unconditional jump from the
+ new bb to the original destination of the conditional jump. */
+
+static void
+fix_crossing_conditional_branches (void)
+{
+ basic_block cur_bb;
+ basic_block new_bb;
+ basic_block last_bb;
+ basic_block dest;
+ basic_block prev_bb;
+ edge succ1;
+ edge succ2;
+ edge crossing_edge;
+ edge new_edge;
+ rtx old_jump;
+ rtx set_src;
+ rtx old_label = NULL_RTX;
+ rtx new_label;
+ rtx new_jump;
+ rtx barrier;
+
+ last_bb = EXIT_BLOCK_PTR->prev_bb;
+
+ FOR_EACH_BB (cur_bb)
{
- bb = next;
- goto restart;
+ crossing_edge = NULL;
+ if (EDGE_COUNT (cur_bb->succs) > 0)
+ succ1 = EDGE_SUCC (cur_bb, 0);
+ else
+ succ1 = NULL;
+
+ if (EDGE_COUNT (cur_bb->succs) > 1)
+ succ2 = EDGE_SUCC (cur_bb, 1);
+ else
+ succ2 = NULL;
+
+ /* We already took care of fall-through edges, so only one successor
+ can be a crossing edge. */
+
+ if (succ1 && (succ1->flags & EDGE_CROSSING))
+ crossing_edge = succ1;
+ else if (succ2 && (succ2->flags & EDGE_CROSSING))
+ crossing_edge = succ2;
+
+ if (crossing_edge)
+ {
+ old_jump = BB_END (cur_bb);
+
+ /* Check to make sure the jump instruction is a
+ conditional jump. */
+
+ set_src = NULL_RTX;
+
+ if (any_condjump_p (old_jump))
+ {
+ if (GET_CODE (PATTERN (old_jump)) == SET)
+ set_src = SET_SRC (PATTERN (old_jump));
+ else if (GET_CODE (PATTERN (old_jump)) == PARALLEL)
+ {
+ set_src = XVECEXP (PATTERN (old_jump), 0,0);
+ if (GET_CODE (set_src) == SET)
+ set_src = SET_SRC (set_src);
+ else
+ set_src = NULL_RTX;
+ }
+ }
+
+ if (set_src && (GET_CODE (set_src) == IF_THEN_ELSE))
+ {
+ if (GET_CODE (XEXP (set_src, 1)) == PC)
+ old_label = XEXP (set_src, 2);
+ else if (GET_CODE (XEXP (set_src, 2)) == PC)
+ old_label = XEXP (set_src, 1);
+
+ /* Check to see if new bb for jumping to that dest has
+ already been created; if so, use it; if not, create
+ a new one. */
+
+ new_bb = find_jump_block (crossing_edge->dest);
+
+ if (new_bb)
+ new_label = block_label (new_bb);
+ else
+ {
+ /* Create new basic block to be dest for
+ conditional jump. */
+
+ new_bb = create_basic_block (NULL, NULL, last_bb);
+ new_bb->aux = last_bb->aux;
+ last_bb->aux = new_bb;
+ prev_bb = last_bb;
+ last_bb = new_bb;
+
+ /* Update register liveness information. */
+
+ new_bb->il.rtl->global_live_at_start = ALLOC_REG_SET (®_obstack);
+ new_bb->il.rtl->global_live_at_end = ALLOC_REG_SET (®_obstack);
+ COPY_REG_SET (new_bb->il.rtl->global_live_at_end,
+ prev_bb->il.rtl->global_live_at_end);
+ COPY_REG_SET (new_bb->il.rtl->global_live_at_start,
+ prev_bb->il.rtl->global_live_at_end);
+
+ /* Put appropriate instructions in new bb. */
+
+ new_label = gen_label_rtx ();
+ emit_label_before (new_label, BB_HEAD (new_bb));
+ BB_HEAD (new_bb) = new_label;
+
+ if (GET_CODE (old_label) == LABEL_REF)
+ {
+ old_label = JUMP_LABEL (old_jump);
+ new_jump = emit_jump_insn_after (gen_jump
+ (old_label),
+ BB_END (new_bb));
+ }
+ else
+ {
+ gcc_assert (HAVE_return
+ && GET_CODE (old_label) == RETURN);
+ new_jump = emit_jump_insn_after (gen_return (),
+ BB_END (new_bb));
+ }
+
+ barrier = emit_barrier_after (new_jump);
+ JUMP_LABEL (new_jump) = old_label;
+ new_bb->il.rtl->footer = unlink_insn_chain (barrier,
+ barrier);
+
+ /* Make sure new bb is in same partition as source
+ of conditional branch. */
+ BB_COPY_PARTITION (new_bb, cur_bb);
+ }
+
+ /* Make old jump branch to new bb. */
+
+ redirect_jump (old_jump, new_label, 0);
+
+ /* Remove crossing_edge as predecessor of 'dest'. */
+
+ dest = crossing_edge->dest;
+
+ redirect_edge_succ (crossing_edge, new_bb);
+
+ /* Make a new edge from new_bb to old dest; new edge
+ will be a successor for new_bb and a predecessor
+ for 'dest'. */
+
+ if (EDGE_COUNT (new_bb->succs) == 0)
+ new_edge = make_edge (new_bb, dest, 0);
+ else
+ new_edge = EDGE_SUCC (new_bb, 0);
+
+ crossing_edge->flags &= ~EDGE_CROSSING;
+ new_edge->flags |= EDGE_CROSSING;
+ }
+ }
}
+}
+
+/* Find any unconditional branches that cross between hot and cold
+ sections. Convert them into indirect jumps instead. */
+
+static void
+fix_crossing_unconditional_branches (void)
+{
+ basic_block cur_bb;
+ rtx last_insn;
+ rtx label;
+ rtx label_addr;
+ rtx indirect_jump_sequence;
+ rtx jump_insn = NULL_RTX;
+ rtx new_reg;
+ rtx cur_insn;
+ edge succ;
+
+ FOR_EACH_BB (cur_bb)
+ {
+ last_insn = BB_END (cur_bb);
+
+ if (EDGE_COUNT (cur_bb->succs) < 1)
+ continue;
+
+ succ = EDGE_SUCC (cur_bb, 0);
+
+ /* Check to see if bb ends in a crossing (unconditional) jump. At
+ this point, no crossing jumps should be conditional. */
+
+ if (JUMP_P (last_insn)
+ && (succ->flags & EDGE_CROSSING))
+ {
+ rtx label2, table;
+
+ gcc_assert (!any_condjump_p (last_insn));
- return prev;
+ /* Make sure the jump is not already an indirect or table jump. */
+
+ if (!computed_jump_p (last_insn)
+ && !tablejump_p (last_insn, &label2, &table))
+ {
+ /* We have found a "crossing" unconditional branch. Now
+ we must convert it to an indirect jump. First create
+ reference of label, as target for jump. */
+
+ label = JUMP_LABEL (last_insn);
+ label_addr = gen_rtx_LABEL_REF (Pmode, label);
+ LABEL_NUSES (label) += 1;
+
+ /* Get a register to use for the indirect jump. */
+
+ new_reg = gen_reg_rtx (Pmode);
+
+ /* Generate indirect the jump sequence. */
+
+ start_sequence ();
+ emit_move_insn (new_reg, label_addr);
+ emit_indirect_jump (new_reg);
+ indirect_jump_sequence = get_insns ();
+ end_sequence ();
+
+ /* Make sure every instruction in the new jump sequence has
+ its basic block set to be cur_bb. */
+
+ for (cur_insn = indirect_jump_sequence; cur_insn;
+ cur_insn = NEXT_INSN (cur_insn))
+ {
+ if (!BARRIER_P (cur_insn))
+ BLOCK_FOR_INSN (cur_insn) = cur_bb;
+ if (JUMP_P (cur_insn))
+ jump_insn = cur_insn;
+ }
+
+ /* Insert the new (indirect) jump sequence immediately before
+ the unconditional jump, then delete the unconditional jump. */
+
+ emit_insn_before (indirect_jump_sequence, last_insn);
+ delete_insn (last_insn);
+
+ /* Make BB_END for cur_bb be the jump instruction (NOT the
+ barrier instruction at the end of the sequence...). */
+
+ BB_END (cur_bb) = jump_insn;
+ }
+ }
+ }
+}
+
+/* Add REG_CROSSING_JUMP note to all crossing jump insns. */
+
+static void
+add_reg_crossing_jump_notes (void)
+{
+ basic_block bb;
+ edge e;
+ edge_iterator ei;
+
+ FOR_EACH_BB (bb)
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ if ((e->flags & EDGE_CROSSING)
+ && JUMP_P (BB_END (e->src)))
+ REG_NOTES (BB_END (e->src)) = gen_rtx_EXPR_LIST (REG_CROSSING_JUMP,
+ NULL_RTX,
+ REG_NOTES (BB_END
+ (e->src)));
+}
+
+/* Hot and cold basic blocks are partitioned and put in separate
+ sections of the .o file, to reduce paging and improve cache
+ performance (hopefully). This can result in bits of code from the
+ same function being widely separated in the .o file. However this
+ is not obvious to the current bb structure. Therefore we must take
+ care to ensure that: 1). There are no fall_thru edges that cross
+ between sections; 2). For those architectures which have "short"
+ conditional branches, all conditional branches that attempt to
+ cross between sections are converted to unconditional branches;
+ and, 3). For those architectures which have "short" unconditional
+ branches, all unconditional branches that attempt to cross between
+ sections are converted to indirect jumps.
+
+ The code for fixing up fall_thru edges that cross between hot and
+ cold basic blocks does so by creating new basic blocks containing
+ unconditional branches to the appropriate label in the "other"
+ section. The new basic block is then put in the same (hot or cold)
+ section as the original conditional branch, and the fall_thru edge
+ is modified to fall into the new basic block instead. By adding
+ this level of indirection we end up with only unconditional branches
+ crossing between hot and cold sections.
+
+ Conditional branches are dealt with by adding a level of indirection.
+ A new basic block is added in the same (hot/cold) section as the
+ conditional branch, and the conditional branch is retargeted to the
+ new basic block. The new basic block contains an unconditional branch
+ to the original target of the conditional branch (in the other section).
+
+ Unconditional branches are dealt with by converting them into
+ indirect jumps. */
+
+static void
+fix_edges_for_rarely_executed_code (edge *crossing_edges,
+ int n_crossing_edges)
+{
+ /* Make sure the source of any crossing edge ends in a jump and the
+ destination of any crossing edge has a label. */
+
+ add_labels_and_missing_jumps (crossing_edges, n_crossing_edges);
+
+ /* Convert all crossing fall_thru edges to non-crossing fall
+ thrus to unconditional jumps (that jump to the original fall
+ thru dest). */
+
+ fix_up_fall_thru_edges ();
+
+ /* If the architecture does not have conditional branches that can
+ span all of memory, convert crossing conditional branches into
+ crossing unconditional branches. */
+
+ if (!HAS_LONG_COND_BRANCH)
+ fix_crossing_conditional_branches ();
+
+ /* If the architecture does not have unconditional branches that
+ can span all of memory, convert crossing unconditional branches
+ into indirect jumps. Since adding an indirect jump also adds
+ a new register usage, update the register usage information as
+ well. */
+
+ if (!HAS_LONG_UNCOND_BRANCH)
+ {
+ fix_crossing_unconditional_branches ();
+ reg_scan (get_insns(), max_reg_num ());
+ }
+
+ add_reg_crossing_jump_notes ();
+}
+
+/* Verify, in the basic block chain, that there is at most one switch
+ between hot/cold partitions. This is modelled on
+ rtl_verify_flow_info_1, but it cannot go inside that function
+ because this condition will not be true until after
+ reorder_basic_blocks is called. */
+
+static void
+verify_hot_cold_block_grouping (void)
+{
+ basic_block bb;
+ int err = 0;
+ bool switched_sections = false;
+ int current_partition = 0;
+
+ FOR_EACH_BB (bb)
+ {
+ if (!current_partition)
+ current_partition = BB_PARTITION (bb);
+ if (BB_PARTITION (bb) != current_partition)
+ {
+ if (switched_sections)
+ {
+ error ("multiple hot/cold transitions found (bb %i)",
+ bb->index);
+ err = 1;
+ }
+ else
+ {
+ switched_sections = true;
+ current_partition = BB_PARTITION (bb);
+ }
+ }
+ }
+
+ gcc_assert(!err);
}
-/* Reorder basic blocks. The main entry point to this file. */
+/* Reorder basic blocks. The main entry point to this file. FLAGS is
+ the set of flags to pass to cfg_layout_initialize(). */
void
-reorder_basic_blocks ()
+reorder_basic_blocks (unsigned int flags)
{
+ int n_traces;
+ int i;
+ struct trace *traces;
+
if (n_basic_blocks <= 1)
return;
- if ((* targetm.cannot_modify_jumps_p) ())
+ if (targetm.cannot_modify_jumps_p ())
return;
- cfg_layout_initialize ();
+ cfg_layout_initialize (flags);
+
+ set_edge_can_fallthru_flag ();
+ mark_dfs_back_edges ();
- make_reorder_chain ();
+ /* We are estimating the length of uncond jump insn only once since the code
+ for getting the insn length always returns the minimal length now. */
+ if (uncond_jump_length == 0)
+ uncond_jump_length = get_uncond_jump_length ();
+
+ /* We need to know some information for each basic block. */
+ array_size = GET_ARRAY_SIZE (last_basic_block);
+ bbd = xmalloc (array_size * sizeof (bbro_basic_block_data));
+ for (i = 0; i < array_size; i++)
+ {
+ bbd[i].start_of_trace = -1;
+ bbd[i].in_trace = -1;
+ bbd[i].end_of_trace = -1;
+ bbd[i].heap = NULL;
+ bbd[i].node = NULL;
+ }
- if (rtl_dump_file)
- dump_flow_info (rtl_dump_file);
+ traces = xmalloc (n_basic_blocks * sizeof (struct trace));
+ n_traces = 0;
+ find_traces (&n_traces, traces);
+ connect_traces (n_traces, traces);
+ FREE (traces);
+ FREE (bbd);
+
+ if (dump_file)
+ dump_flow_info (dump_file);
cfg_layout_finalize ();
+ if (flag_reorder_blocks_and_partition)
+ verify_hot_cold_block_grouping ();
+}
+
+/* Determine which partition the first basic block in the function
+ belongs to, then find the first basic block in the current function
+ that belongs to a different section, and insert a
+ NOTE_INSN_SWITCH_TEXT_SECTIONS note immediately before it in the
+ instruction stream. When writing out the assembly code,
+ encountering this note will make the compiler switch between the
+ hot and cold text sections. */
+
+static void
+insert_section_boundary_note (void)
+{
+ basic_block bb;
+ rtx new_note;
+ int first_partition = 0;
+
+ if (flag_reorder_blocks_and_partition)
+ FOR_EACH_BB (bb)
+ {
+ if (!first_partition)
+ first_partition = BB_PARTITION (bb);
+ if (BB_PARTITION (bb) != first_partition)
+ {
+ new_note = emit_note_before (NOTE_INSN_SWITCH_TEXT_SECTIONS,
+ BB_HEAD (bb));
+ break;
+ }
+ }
}
+
+/* Duplicate the blocks containing computed gotos. This basically unfactors
+ computed gotos that were factored early on in the compilation process to
+ speed up edge based data flow. We used to not unfactoring them again,
+ which can seriously pessimize code with many computed jumps in the source
+ code, such as interpreters. See e.g. PR15242. */
+
+static bool
+gate_duplicate_computed_gotos (void)
+{
+ return (optimize > 0 && flag_expensive_optimizations && !optimize_size);
+}
+
+
+static void
+duplicate_computed_gotos (void)
+{
+ basic_block bb, new_bb;
+ bitmap candidates;
+ int max_size;
+
+ if (n_basic_blocks <= 1)
+ return;
+
+ if (targetm.cannot_modify_jumps_p ())
+ return;
+
+ cfg_layout_initialize (0);
+
+ /* We are estimating the length of uncond jump insn only once
+ since the code for getting the insn length always returns
+ the minimal length now. */
+ if (uncond_jump_length == 0)
+ uncond_jump_length = get_uncond_jump_length ();
+
+ max_size = uncond_jump_length * PARAM_VALUE (PARAM_MAX_GOTO_DUPLICATION_INSNS);
+ candidates = BITMAP_ALLOC (NULL);
+
+ /* Look for blocks that end in a computed jump, and see if such blocks
+ are suitable for unfactoring. If a block is a candidate for unfactoring,
+ mark it in the candidates. */
+ FOR_EACH_BB (bb)
+ {
+ rtx insn;
+ edge e;
+ edge_iterator ei;
+ int size, all_flags;
+
+ /* Build the reorder chain for the original order of blocks. */
+ if (bb->next_bb != EXIT_BLOCK_PTR)
+ bb->aux = bb->next_bb;
+
+ /* Obviously the block has to end in a computed jump. */
+ if (!computed_jump_p (BB_END (bb)))
+ continue;
+
+ /* Only consider blocks that can be duplicated. */
+ if (find_reg_note (BB_END (bb), REG_CROSSING_JUMP, NULL_RTX)
+ || !can_duplicate_block_p (bb))
+ continue;
+
+ /* Make sure that the block is small enough. */
+ size = 0;
+ FOR_BB_INSNS (bb, insn)
+ if (INSN_P (insn))
+ {
+ size += get_attr_min_length (insn);
+ if (size > max_size)
+ break;
+ }
+ if (size > max_size)
+ continue;
+
+ /* Final check: there must not be any incoming abnormal edges. */
+ all_flags = 0;
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ all_flags |= e->flags;
+ if (all_flags & EDGE_COMPLEX)
+ continue;
+
+ bitmap_set_bit (candidates, bb->index);
+ }
+
+ /* Nothing to do if there is no computed jump here. */
+ if (bitmap_empty_p (candidates))
+ goto done;
+
+ /* Duplicate computed gotos. */
+ FOR_EACH_BB (bb)
+ {
+ if (bb->il.rtl->visited)
+ continue;
+
+ bb->il.rtl->visited = 1;
+
+ /* BB must have one outgoing edge. That edge must not lead to
+ the exit block or the next block.
+ The destination must have more than one predecessor. */
+ if (!single_succ_p (bb)
+ || single_succ (bb) == EXIT_BLOCK_PTR
+ || single_succ (bb) == bb->next_bb
+ || single_pred_p (single_succ (bb)))
+ continue;
+
+ /* The successor block has to be a duplication candidate. */
+ if (!bitmap_bit_p (candidates, single_succ (bb)->index))
+ continue;
+
+ new_bb = duplicate_block (single_succ (bb), single_succ_edge (bb), bb);
+ new_bb->aux = bb->aux;
+ bb->aux = new_bb;
+ new_bb->il.rtl->visited = 1;
+ }
+
+done:
+ cfg_layout_finalize ();
+
+ BITMAP_FREE (candidates);
+}
+
+struct tree_opt_pass pass_duplicate_computed_gotos =
+{
+ "compgotos", /* name */
+ gate_duplicate_computed_gotos, /* gate */
+ duplicate_computed_gotos, /* execute */
+ NULL, /* sub */
+ NULL, /* next */
+ 0, /* static_pass_number */
+ TV_REORDER_BLOCKS, /* tv_id */
+ 0, /* properties_required */
+ 0, /* properties_provided */
+ 0, /* properties_destroyed */
+ 0, /* todo_flags_start */
+ TODO_dump_func, /* todo_flags_finish */
+ 0 /* letter */
+};
+
+
+/* This function is the main 'entrance' for the optimization that
+ partitions hot and cold basic blocks into separate sections of the
+ .o file (to improve performance and cache locality). Ideally it
+ would be called after all optimizations that rearrange the CFG have
+ been called. However part of this optimization may introduce new
+ register usage, so it must be called before register allocation has
+ occurred. This means that this optimization is actually called
+ well before the optimization that reorders basic blocks (see
+ function above).
+
+ This optimization checks the feedback information to determine
+ which basic blocks are hot/cold, updates flags on the basic blocks
+ to indicate which section they belong in. This information is
+ later used for writing out sections in the .o file. Because hot
+ and cold sections can be arbitrarily large (within the bounds of
+ memory), far beyond the size of a single function, it is necessary
+ to fix up all edges that cross section boundaries, to make sure the
+ instructions used can actually span the required distance. The
+ fixes are described below.
+
+ Fall-through edges must be changed into jumps; it is not safe or
+ legal to fall through across a section boundary. Whenever a
+ fall-through edge crossing a section boundary is encountered, a new
+ basic block is inserted (in the same section as the fall-through
+ source), and the fall through edge is redirected to the new basic
+ block. The new basic block contains an unconditional jump to the
+ original fall-through target. (If the unconditional jump is
+ insufficient to cross section boundaries, that is dealt with a
+ little later, see below).
+
+ In order to deal with architectures that have short conditional
+ branches (which cannot span all of memory) we take any conditional
+ jump that attempts to cross a section boundary and add a level of
+ indirection: it becomes a conditional jump to a new basic block, in
+ the same section. The new basic block contains an unconditional
+ jump to the original target, in the other section.
+
+ For those architectures whose unconditional branch is also
+ incapable of reaching all of memory, those unconditional jumps are
+ converted into indirect jumps, through a register.
+
+ IMPORTANT NOTE: This optimization causes some messy interactions
+ with the cfg cleanup optimizations; those optimizations want to
+ merge blocks wherever possible, and to collapse indirect jump
+ sequences (change "A jumps to B jumps to C" directly into "A jumps
+ to C"). Those optimizations can undo the jump fixes that
+ partitioning is required to make (see above), in order to ensure
+ that jumps attempting to cross section boundaries are really able
+ to cover whatever distance the jump requires (on many architectures
+ conditional or unconditional jumps are not able to reach all of
+ memory). Therefore tests have to be inserted into each such
+ optimization to make sure that it does not undo stuff necessary to
+ cross partition boundaries. This would be much less of a problem
+ if we could perform this optimization later in the compilation, but
+ unfortunately the fact that we may need to create indirect jumps
+ (through registers) requires that this optimization be performed
+ before register allocation. */
+
+void
+partition_hot_cold_basic_blocks (void)
+{
+ basic_block cur_bb;
+ edge *crossing_edges;
+ int n_crossing_edges;
+ int max_edges = 2 * last_basic_block;
+
+ if (n_basic_blocks <= 1)
+ return;
+
+ crossing_edges = xcalloc (max_edges, sizeof (edge));
+
+ cfg_layout_initialize (0);
+
+ FOR_EACH_BB (cur_bb)
+ if (cur_bb->index >= 0
+ && cur_bb->next_bb->index >= 0)
+ cur_bb->aux = cur_bb->next_bb;
+
+ find_rarely_executed_basic_blocks_and_crossing_edges (crossing_edges,
+ &n_crossing_edges,
+ &max_edges);
+
+ if (n_crossing_edges > 0)
+ fix_edges_for_rarely_executed_code (crossing_edges, n_crossing_edges);
+
+ free (crossing_edges);
+
+ cfg_layout_finalize();
+}
+\f
+static bool
+gate_handle_reorder_blocks (void)
+{
+ return (optimize > 0);
+}
+
+
+/* Reorder basic blocks. */
+static void
+rest_of_handle_reorder_blocks (void)
+{
+ bool changed;
+ unsigned int liveness_flags;
+
+ /* Last attempt to optimize CFG, as scheduling, peepholing and insn
+ splitting possibly introduced more crossjumping opportunities. */
+ liveness_flags = (!HAVE_conditional_execution ? CLEANUP_UPDATE_LIFE : 0);
+ changed = cleanup_cfg (CLEANUP_EXPENSIVE | liveness_flags);
+
+ if (flag_sched2_use_traces && flag_schedule_insns_after_reload)
+ {
+ timevar_push (TV_TRACER);
+ tracer (liveness_flags);
+ timevar_pop (TV_TRACER);
+ }
+
+ if (flag_reorder_blocks || flag_reorder_blocks_and_partition)
+ reorder_basic_blocks (liveness_flags);
+ if (flag_reorder_blocks || flag_reorder_blocks_and_partition
+ || (flag_sched2_use_traces && flag_schedule_insns_after_reload))
+ changed |= cleanup_cfg (CLEANUP_EXPENSIVE | liveness_flags);
+
+ /* On conditional execution targets we can not update the life cheaply, so
+ we deffer the updating to after both cleanups. This may lose some cases
+ but should not be terribly bad. */
+ if (changed && HAVE_conditional_execution)
+ update_life_info (NULL, UPDATE_LIFE_GLOBAL_RM_NOTES,
+ PROP_DEATH_NOTES);
+
+ /* Add NOTE_INSN_SWITCH_TEXT_SECTIONS notes. */
+ insert_section_boundary_note ();
+}
+
+struct tree_opt_pass pass_reorder_blocks =
+{
+ "bbro", /* name */
+ gate_handle_reorder_blocks, /* gate */
+ rest_of_handle_reorder_blocks, /* execute */
+ NULL, /* sub */
+ NULL, /* next */
+ 0, /* static_pass_number */
+ TV_REORDER_BLOCKS, /* tv_id */
+ 0, /* properties_required */
+ 0, /* properties_provided */
+ 0, /* properties_destroyed */
+ 0, /* todo_flags_start */
+ TODO_dump_func, /* todo_flags_finish */
+ 'B' /* letter */
+};
+
+static bool
+gate_handle_partition_blocks (void)
+{
+ /* The optimization to partition hot/cold basic blocks into separate
+ sections of the .o file does not work well with linkonce or with
+ user defined section attributes. Don't call it if either case
+ arises. */
+
+ return (flag_reorder_blocks_and_partition
+ && !DECL_ONE_ONLY (current_function_decl)
+ && !user_defined_section_attribute);
+}
+
+/* Partition hot and cold basic blocks. */
+static void
+rest_of_handle_partition_blocks (void)
+{
+ no_new_pseudos = 0;
+ partition_hot_cold_basic_blocks ();
+ allocate_reg_life_data ();
+ update_life_info (NULL, UPDATE_LIFE_GLOBAL_RM_NOTES,
+ PROP_LOG_LINKS | PROP_REG_INFO | PROP_DEATH_NOTES);
+ no_new_pseudos = 1;
+}
+
+struct tree_opt_pass pass_partition_blocks =
+{
+ "bbpart", /* name */
+ gate_handle_partition_blocks, /* gate */
+ rest_of_handle_partition_blocks, /* execute */
+ NULL, /* sub */
+ NULL, /* next */
+ 0, /* static_pass_number */
+ TV_REORDER_BLOCKS, /* tv_id */
+ 0, /* properties_required */
+ 0, /* properties_provided */
+ 0, /* properties_destroyed */
+ 0, /* todo_flags_start */
+ TODO_dump_func, /* todo_flags_finish */
+ 0 /* letter */
+};
+
+
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