/* Basic block reordering routines for the GNU compiler.
- Copyright (C) 2000, 2002 Free Software Foundation, Inc.
+ Copyright (C) 2000, 2002, 2003 Free Software Foundation, Inc.
This file is part of GCC.
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.
+/* 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 "flags.h"
#include "output.h"
#include "cfglayout.h"
+#include "fibheap.h"
#include "target.h"
+/* The number of rounds. */
+#define N_ROUNDS 4
+
+/* Branch thresholds in thousandths (per mille) of the REG_BR_PROB_BASE. */
+static int branch_threshold[N_ROUNDS] = {400, 200, 100, 0};
+
+/* Exec thresholds in thousandths (per mille) of the frequency of bb 0. */
+static int exec_threshold[N_ROUNDS] = {500, 200, 50, 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 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) \
+ do { if (P) { free (P); P = 0; } else { abort (); } } while (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. */
+int max_entry_frequency;
+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 *);
+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);
+static void connect_traces (int, struct trace *);
+static bool copy_bb_p (basic_block, int);
+static int get_uncond_jump_length (void);
\f
-/* Compute an ordering for a subgraph beginning with block BB. Record the
- ordering in RBI()->index and chained through RBI()->next. */
+/* 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;
- basic_block next, bb;
+ int i;
+ edge e;
+ fibheap_t heap;
- /* Loop until we've placed every block. */
- do
+ /* Insert entry points of function into heap. */
+ heap = fibheap_new ();
+ max_entry_frequency = 0;
+ max_entry_count = 0;
+ for (e = ENTRY_BLOCK_PTR->succ; e; e = e->succ_next)
{
- next = NULL;
-
- /* 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. */
-
- FOR_ALL_BB (bb)
- if (! RBI (bb)->visited)
- {
- next = bb;
- break;
- }
-
- if (next)
- prev = make_reorder_chain_1 (next, prev);
+ 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;
}
- while (next);
- RBI (prev)->next = NULL;
-}
-/* A helper function for make_reorder_chain.
+ /* Find the traces. */
+ for (i = 0; i < N_ROUNDS; i++)
+ {
+ gcov_type count_threshold;
- 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 (rtl_dump_file)
+ fprintf (rtl_dump_file, "STC - round %d\n", i + 1);
- ??? 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 (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);
+ }
+ fibheap_delete (heap);
+
+ if (rtl_dump_file)
+ {
+ for (i = 0; i < *n_traces; i++)
+ {
+ basic_block bb;
+ fprintf (rtl_dump_file, "Trace %d (round %d): ", i + 1,
+ traces[i].round + 1);
+ for (bb = traces[i].first; bb != traces[i].last; bb = bb->rbi->next)
+ fprintf (rtl_dump_file, "%d [%d] ", bb->index, bb->frequency);
+ fprintf (rtl_dump_file, "%d [%d]\n", bb->index, bb->frequency);
+ }
+ fflush (rtl_dump_file);
+ }
+}
+
+/* Rotate loop whose back edge is BACK_EDGE in the tail of trace TRACE
+ (with sequential number TRACE_N). */
static basic_block
-make_reorder_chain_1 (bb, prev)
- basic_block bb;
- basic_block prev;
+rotate_loop (edge back_edge, struct trace *trace, int trace_n)
{
- edge e;
- basic_block next;
- rtx note;
+ 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;
- /* Mark this block visited. */
- if (prev)
+ /* Find the most frequent edge that goes out from current trace. */
+ bb = back_edge->dest;
+ do
{
- restart:
- RBI (prev)->next = bb;
+ edge e;
+ for (e = bb->succ; e; e = e->succ_next)
+ if (e->dest != EXIT_BLOCK_PTR
+ && e->dest->rbi->visited != trace_n
+ && (e->flags & EDGE_CAN_FALLTHRU)
+ && !(e->flags & EDGE_COMPLEX))
+ {
+ if (is_preferred)
+ {
+ /* The best edge is preferred. */
+ if (!e->dest->rbi->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->rbi->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->rbi->next;
+ }
+ while (bb != back_edge->dest);
- if (rtl_dump_file && prev->next_bb != bb)
- fprintf (rtl_dump_file, "Reordering block %d after %d\n",
- bb->sindex, prev->sindex);
+ 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->rbi->next;
+ }
+ else
+ {
+ basic_block prev_bb;
+
+ for (prev_bb = trace->first;
+ prev_bb->rbi->next != back_edge->dest;
+ prev_bb = prev_bb->rbi->next)
+ ;
+ prev_bb->rbi->next = best_bb->rbi->next;
+
+ /* Try to get rid of uncond jump to cond jump. */
+ if (prev_bb->succ && !prev_bb->succ->succ_next)
+ {
+ basic_block header = prev_bb->succ->dest;
+
+ /* Duplicate HEADER if it is a small block containing cond jump
+ in the end. */
+ if (any_condjump_p (header->end) && copy_bb_p (header, 0))
+ {
+ copy_bb (header, prev_bb->succ, prev_bb, trace_n);
+ }
+ }
+ }
}
else
{
- if (bb->prev_bb != ENTRY_BLOCK_PTR)
- abort ();
+ /* We have not found suitable loop tail so do no rotation. */
+ best_bb = back_edge->src;
}
- RBI (bb)->visited = 1;
- prev = bb;
+ best_bb->rbi->next = NULL;
+ return best_bb;
+}
- if (bb->succ == NULL)
- return prev;
+/* This function marks BB that it was visited in trace number TRACE. */
- /* Find the most probable block. */
+static void
+mark_bb_visited (basic_block bb, int trace)
+{
+ bb->rbi->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. */
- next = NULL;
- if (any_condjump_p (bb->end)
- && (note = find_reg_note (bb->end, REG_BR_PROB, 0)) != NULL)
+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)
+{
+ /* Heap for discarded basic blocks which are possible starting points for
+ the next round. */
+ fibheap_t new_heap = fibheap_new ();
+
+ while (!fibheap_empty (*heap))
{
- int taken, probability;
- edge e_taken, e_fall;
+ basic_block bb;
+ struct trace *trace;
+ edge best_edge, e;
+ fibheapkey_t key;
+
+ bb = fibheap_extract_min (*heap);
+ bbd[bb->index].heap = NULL;
+ bbd[bb->index].node = NULL;
+
+ if (rtl_dump_file)
+ fprintf (rtl_dump_file, "Getting bb %d\n", bb->index);
+
+ /* If the BB's frequency is too low send BB to the next round. */
+ if (round < N_ROUNDS - 1
+ && (bb->frequency < exec_th || bb->count < count_th
+ || probably_never_executed_bb_p (bb)))
+ {
+ int key = bb_to_key (bb);
+ bbd[bb->index].heap = new_heap;
+ bbd[bb->index].node = fibheap_insert (new_heap, key, bb);
+
+ if (rtl_dump_file)
+ fprintf (rtl_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;
+ (*n_traces)++;
+
+ do
+ {
+ int prob, freq;
+
+ /* 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 (rtl_dump_file)
+ fprintf (rtl_dump_file, "Basic block %d was visited in trace %d\n",
+ bb->index, *n_traces - 1);
+
+ /* Select the successor that will be placed after BB. */
+ for (e = bb->succ; e; e = e->succ_next)
+ {
+ if (e->flags & EDGE_FAKE)
+ abort ();
+
+ if (e->dest == EXIT_BLOCK_PTR)
+ continue;
+
+ if (e->dest->rbi->visited
+ && e->dest->rbi->visited != *n_traces)
+ continue;
+
+ prob = e->probability;
+ freq = EDGE_FREQUENCY (e);
+
+ /* Edge that cannot be fallthru or improbable or infrequent
+ successor (ie. it is unsuitable successor). */
+ if (!(e->flags & EDGE_CAN_FALLTHRU) || (e->flags & EDGE_COMPLEX)
+ || prob < branch_th || freq < exec_th || e->count < count_th)
+ continue;
+
+ if (better_edge_p (bb, e, prob, freq, best_prob, best_freq))
+ {
+ 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 && best_edge->dest->pred->pred_next
+ && copy_bb_p (best_edge->dest, 0))
+ best_edge = NULL;
+
+ /* Add all non-selected successors to the heaps. */
+ for (e = bb->succ; e; e = e->succ_next)
+ {
+ if (e == best_edge
+ || e->dest == EXIT_BLOCK_PTR
+ || e->dest->rbi->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 (rtl_dump_file)
+ {
+ fprintf (rtl_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)
+ {
+ if (round < N_ROUNDS - 1)
+ which_heap = new_heap;
+ }
+
+ bbd[e->dest->index].heap = which_heap;
+ bbd[e->dest->index].node = fibheap_insert (which_heap,
+ key, e->dest);
+
+ if (rtl_dump_file)
+ {
+ fprintf (rtl_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->rbi->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 (rtl_dump_file)
+ {
+ fprintf (rtl_dump_file,
+ "Rotating loop %d - %d\n",
+ best_edge->dest->index, bb->index);
+ }
+ bb->rbi->next = best_edge->dest;
+ bb = rotate_loop (best_edge, trace, *n_traces);
+ }
+ }
+ else
+ {
+ /* The loop has less than 4 iterations. */
+
+ /* Check whether there is another edge from BB. */
+ edge another_edge;
+ for (another_edge = bb->succ;
+ another_edge;
+ another_edge = another_edge->succ_next)
+ if (another_edge != best_edge)
+ break;
+
+ if (!another_edge && copy_bb_p (best_edge->dest,
+ !optimize_size))
+ {
+ bb = copy_bb (best_edge->dest, best_edge, bb,
+ *n_traces);
+ }
+ }
+ }
+
+ /* 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.
- probability = INTVAL (XEXP (note, 0));
- taken = probability > REG_BR_PROB_BASE / 2;
+ This situation is created for example by:
- /* Find the normal taken edge and the normal fallthru edge.
+ if (A) B;
+ C;
- 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.
+ */
- 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. */
+ for (e = bb->succ; e; e = e->succ_next)
+ if (e != best_edge
+ && (e->flags & EDGE_CAN_FALLTHRU)
+ && !(e->flags & EDGE_COMPLEX)
+ && !e->dest->rbi->visited
+ && !e->dest->pred->pred_next
+ && e->dest->succ
+ && (e->dest->succ->flags & EDGE_CAN_FALLTHRU)
+ && !(e->dest->succ->flags & EDGE_COMPLEX)
+ && !e->dest->succ->succ_next
+ && e->dest->succ->dest == best_edge->dest
+ && 2 * e->dest->frequency >= EDGE_FREQUENCY (best_edge))
+ {
+ best_edge = e;
+ if (rtl_dump_file)
+ fprintf (rtl_dump_file, "Selecting BB %d\n",
+ best_edge->dest->index);
+ break;
+ }
- e_taken = e_fall = NULL;
- for (e = bb->succ; e ; e = e->succ_next)
+ bb->rbi->next = best_edge->dest;
+ 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 (e = bb->succ; e; e = e->succ_next)
{
- if (e->flags & EDGE_FALLTHRU)
- e_fall = e;
- else if (! (e->flags & EDGE_EH))
- e_taken = e;
+ if (e->dest == EXIT_BLOCK_PTR
+ || e->dest->rbi->visited)
+ continue;
+
+ if (bbd[e->dest->index].heap)
+ {
+ key = bb_to_key (e->dest);
+ if (key != bbd[e->dest->index].node->key)
+ {
+ if (rtl_dump_file)
+ {
+ fprintf (rtl_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
+copy_bb (basic_block old_bb, edge e, basic_block bb, int trace)
+{
+ basic_block new_bb;
+
+ new_bb = cfg_layout_duplicate_bb (old_bb, e);
+ if (e->dest != new_bb)
+ abort ();
+ if (e->dest->rbi->visited)
+ abort ();
+ if (rtl_dump_file)
+ fprintf (rtl_dump_file,
+ "Duplicated bb %d (created bb %d)\n",
+ old_bb->index, new_bb->index);
+ new_bb->rbi->visited = trace;
+ new_bb->rbi->next = bb->rbi->next;
+ bb->rbi->next = 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].end_of_trace = -1;
+ bbd[i].heap = NULL;
+ bbd[i].node = NULL;
+ }
+ array_size = new_size;
+
+ if (rtl_dump_file)
+ {
+ fprintf (rtl_dump_file,
+ "Growing the dynamic array to %d elements.\n",
+ array_size);
+ }
+ }
+
+ return new_bb;
+}
+
+/* Compute and return the key (for the heap) of the basic block BB. */
- next = ((taken && e_taken) ? e_taken : e_fall)->dest;
+static fibheapkey_t
+bb_to_key (basic_block bb)
+{
+ edge e;
+
+ int priority = 0;
+
+ /* Do not start in probably never executed blocks. */
+ if (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 (e = bb->pred; e; e = e->pred_next)
+ {
+ 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 (edge_freq > priority)
+ priority = edge_freq;
+ }
}
- /* 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)
+ 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)
+{
+ 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;
+
+ 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;
+ int last_trace;
+ 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;
+ for (i = 0; i < n_traces; i++)
{
- for (e = bb->succ; e ; e = e->succ_next)
- if (e->dest == bb->next_bb)
- {
- if ((e->flags & EDGE_FALLTHRU)
- || (e->dest->succ
- && ! (e->flags & (EDGE_ABNORMAL_CALL | EDGE_EH))))
- next = e->dest;
+ int t = i;
+ int t2;
+ edge e, best;
+ int best_len;
+
+ if (connected[t])
+ continue;
+
+ connected[t] = true;
+
+ /* Find the predecessor traces. */
+ for (t2 = t; t2 > 0;)
+ {
+ best = NULL;
+ best_len = 0;
+ for (e = traces[t2].first->pred; e; e = e->pred_next)
+ {
+ 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]
+ && (!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->rbi->next = best->dest;
+ t2 = bbd[best->src->index].end_of_trace;
+ connected[t2] = true;
+ if (rtl_dump_file)
+ {
+ fprintf (rtl_dump_file, "Connection: %d %d\n",
+ best->src->index, best->dest->index);
+ }
+ }
+ else
break;
- }
+ }
+
+ if (last_trace >= 0)
+ traces[last_trace].last->rbi->next = traces[t2].first;
+ last_trace = t;
+
+ /* Find the successor traces. */
+ while (1)
+ {
+ /* Find the continuation of the chain. */
+ best = NULL;
+ best_len = 0;
+ for (e = traces[t].last->succ; e; e = e->succ_next)
+ {
+ 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]
+ && (!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 (rtl_dump_file)
+ {
+ fprintf (rtl_dump_file, "Connection: %d %d\n",
+ best->src->index, best->dest->index);
+ }
+ t = bbd[best->dest->index].start_of_trace;
+ traces[last_trace].last->rbi->next = 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 (e = traces[t].last->succ; e; e = e->succ_next)
+ if (e->dest != EXIT_BLOCK_PTR
+ && (e->flags & EDGE_CAN_FALLTHRU)
+ && !(e->flags & EDGE_COMPLEX)
+ && (!best || e->probability > best->probability))
+ {
+ 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 (e2 = e->dest->succ; e2; e2 = e2->succ_next)
+ {
+ 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]
+ && (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;
+ }
+ }
+ }
+
+ /* 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 (rtl_dump_file)
+ {
+ fprintf (rtl_dump_file, "Connection: %d %d ",
+ traces[t].last->index, best->dest->index);
+ if (!next_bb)
+ fputc ('\n', rtl_dump_file);
+ else if (next_bb == EXIT_BLOCK_PTR)
+ fprintf (rtl_dump_file, "exit\n");
+ else
+ fprintf (rtl_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->rbi->next = traces[t].first;
+ connected[t] = true;
+ last_trace = t;
+ }
+ else
+ break; /* Stop finding the successor traces. */
+ }
+ else
+ break; /* Stop finding the successor traces. */
+ }
+ }
}
- /* 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)))
- {
- if (next)
- {
- prev = make_reorder_chain_1 (next, prev);
- next = RBI (e->dest)->visited ? NULL : e->dest;
- }
- else
- next = e->dest;
- }
- if (next)
+ if (rtl_dump_file)
{
- bb = next;
- goto restart;
+ basic_block bb;
+
+ fprintf (rtl_dump_file, "Final order:\n");
+ for (bb = traces[0].first; bb; bb = bb->rbi->next)
+ fprintf (rtl_dump_file, "%d ", bb->index);
+ fprintf (rtl_dump_file, "\n");
+ fflush (rtl_dump_file);
}
- 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 (!bb->pred || !bb->pred->pred_next)
+ return false;
+ if (!cfg_layout_can_duplicate_bb_p (bb))
+ return false;
+
+ if (code_may_grow && maybe_hot_bb_p (bb))
+ max_size *= 8;
+
+ for (insn = bb->head; insn != NEXT_INSN (bb->end);
+ insn = NEXT_INSN (insn))
+ {
+ if (INSN_P (insn))
+ size += get_attr_length (insn);
+ }
+
+ if (size <= max_size)
+ return true;
+
+ if (rtl_dump_file)
+ {
+ fprintf (rtl_dump_file,
+ "Block %d can't be copied because its size = %d.\n",
+ bb->index, size);
+ }
+
+ return false;
+}
+
+/* Return the length of unconditional jump instruction. */
+
+static int
+get_uncond_jump_length (void)
+{
+ rtx label, jump;
+ int length;
+
+ label = emit_label_before (gen_label_rtx (), get_insns ());
+ jump = emit_jump_insn (gen_jump (label));
+
+ length = get_attr_length (jump);
+
+ delete_insn (jump);
+ delete_insn (label);
+ return length;
}
/* Reorder basic blocks. The main entry point to this file. */
void
-reorder_basic_blocks ()
+reorder_basic_blocks (void)
{
- if (num_basic_blocks <= 1)
+ int n_traces;
+ int i;
+ struct trace *traces;
+
+ if (n_basic_blocks <= 1)
return;
if ((* targetm.cannot_modify_jumps_p) ())
cfg_layout_initialize ();
- make_reorder_chain ();
+ set_edge_can_fallthru_flag ();
+ mark_dfs_back_edges ();
+
+ /* 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].end_of_trace = -1;
+ bbd[i].heap = NULL;
+ bbd[i].node = NULL;
+ }
+
+ 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 (rtl_dump_file)
dump_flow_info (rtl_dump_file);
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