--- /dev/null
+/* Tail merging for gimple.
+ Copyright (C) 2011 Free Software Foundation, Inc.
+ Contributed by Tom de Vries (tom@codesourcery.com)
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
+
+/* Pass overview.
+
+
+ MOTIVATIONAL EXAMPLE
+
+ gimple representation of gcc/testsuite/gcc.dg/pr43864.c at
+
+ hprofStartupp (charD.1 * outputFileNameD.2600, charD.1 * ctxD.2601)
+ {
+ struct FILED.1638 * fpD.2605;
+ charD.1 fileNameD.2604[1000];
+ intD.0 D.3915;
+ const charD.1 * restrict outputFileName.0D.3914;
+
+ # BLOCK 2 freq:10000
+ # PRED: ENTRY [100.0%] (fallthru,exec)
+ # PT = nonlocal { D.3926 } (restr)
+ outputFileName.0D.3914_3
+ = (const charD.1 * restrict) outputFileNameD.2600_2(D);
+ # .MEMD.3923_13 = VDEF <.MEMD.3923_12(D)>
+ # USE = nonlocal null { fileNameD.2604 D.3926 } (restr)
+ # CLB = nonlocal null { fileNameD.2604 D.3926 } (restr)
+ sprintfD.759 (&fileNameD.2604, outputFileName.0D.3914_3);
+ # .MEMD.3923_14 = VDEF <.MEMD.3923_13>
+ # USE = nonlocal null { fileNameD.2604 D.3926 } (restr)
+ # CLB = nonlocal null { fileNameD.2604 D.3926 } (restr)
+ D.3915_4 = accessD.2606 (&fileNameD.2604, 1);
+ if (D.3915_4 == 0)
+ goto <bb 3>;
+ else
+ goto <bb 4>;
+ # SUCC: 3 [10.0%] (true,exec) 4 [90.0%] (false,exec)
+
+ # BLOCK 3 freq:1000
+ # PRED: 2 [10.0%] (true,exec)
+ # .MEMD.3923_15 = VDEF <.MEMD.3923_14>
+ # USE = nonlocal null { fileNameD.2604 D.3926 } (restr)
+ # CLB = nonlocal null { fileNameD.2604 D.3926 } (restr)
+ freeD.898 (ctxD.2601_5(D));
+ goto <bb 7>;
+ # SUCC: 7 [100.0%] (fallthru,exec)
+
+ # BLOCK 4 freq:9000
+ # PRED: 2 [90.0%] (false,exec)
+ # .MEMD.3923_16 = VDEF <.MEMD.3923_14>
+ # PT = nonlocal escaped
+ # USE = nonlocal null { fileNameD.2604 D.3926 } (restr)
+ # CLB = nonlocal null { fileNameD.2604 D.3926 } (restr)
+ fpD.2605_8 = fopenD.1805 (&fileNameD.2604[0], 0B);
+ if (fpD.2605_8 == 0B)
+ goto <bb 5>;
+ else
+ goto <bb 6>;
+ # SUCC: 5 [1.9%] (true,exec) 6 [98.1%] (false,exec)
+
+ # BLOCK 5 freq:173
+ # PRED: 4 [1.9%] (true,exec)
+ # .MEMD.3923_17 = VDEF <.MEMD.3923_16>
+ # USE = nonlocal null { fileNameD.2604 D.3926 } (restr)
+ # CLB = nonlocal null { fileNameD.2604 D.3926 } (restr)
+ freeD.898 (ctxD.2601_5(D));
+ goto <bb 7>;
+ # SUCC: 7 [100.0%] (fallthru,exec)
+
+ # BLOCK 6 freq:8827
+ # PRED: 4 [98.1%] (false,exec)
+ # .MEMD.3923_18 = VDEF <.MEMD.3923_16>
+ # USE = nonlocal null { fileNameD.2604 D.3926 } (restr)
+ # CLB = nonlocal null { fileNameD.2604 D.3926 } (restr)
+ fooD.2599 (outputFileNameD.2600_2(D), fpD.2605_8);
+ # SUCC: 7 [100.0%] (fallthru,exec)
+
+ # BLOCK 7 freq:10000
+ # PRED: 3 [100.0%] (fallthru,exec) 5 [100.0%] (fallthru,exec)
+ 6 [100.0%] (fallthru,exec)
+ # PT = nonlocal null
+
+ # ctxD.2601_1 = PHI <0B(3), 0B(5), ctxD.2601_5(D)(6)>
+ # .MEMD.3923_11 = PHI <.MEMD.3923_15(3), .MEMD.3923_17(5),
+ .MEMD.3923_18(6)>
+ # VUSE <.MEMD.3923_11>
+ return ctxD.2601_1;
+ # SUCC: EXIT [100.0%]
+ }
+
+ bb 3 and bb 5 can be merged. The blocks have different predecessors, but the
+ same successors, and the same operations.
+
+
+ CONTEXT
+
+ A technique called tail merging (or cross jumping) can fix the example
+ above. For a block, we look for common code at the end (the tail) of the
+ predecessor blocks, and insert jumps from one block to the other.
+ The example is a special case for tail merging, in that 2 whole blocks
+ can be merged, rather than just the end parts of it.
+ We currently only focus on whole block merging, so in that sense
+ calling this pass tail merge is a bit of a misnomer.
+
+ We distinguish 2 kinds of situations in which blocks can be merged:
+ - same operations, same predecessors. The successor edges coming from one
+ block are redirected to come from the other block.
+ - same operations, same successors. The predecessor edges entering one block
+ are redirected to enter the other block. Note that this operation might
+ involve introducing phi operations.
+
+ For efficient implementation, we would like to value numbers the blocks, and
+ have a comparison operator that tells us whether the blocks are equal.
+ Besides being runtime efficient, block value numbering should also abstract
+ from irrelevant differences in order of operations, much like normal value
+ numbering abstracts from irrelevant order of operations.
+
+ For the first situation (same_operations, same predecessors), normal value
+ numbering fits well. We can calculate a block value number based on the
+ value numbers of the defs and vdefs.
+
+ For the second situation (same operations, same successors), this approach
+ doesn't work so well. We can illustrate this using the example. The calls
+ to free use different vdefs: MEMD.3923_16 and MEMD.3923_14, and these will
+ remain different in value numbering, since they represent different memory
+ states. So the resulting vdefs of the frees will be different in value
+ numbering, so the block value numbers will be different.
+
+ The reason why we call the blocks equal is not because they define the same
+ values, but because uses in the blocks use (possibly different) defs in the
+ same way. To be able to detect this efficiently, we need to do some kind of
+ reverse value numbering, meaning number the uses rather than the defs, and
+ calculate a block value number based on the value number of the uses.
+ Ideally, a block comparison operator will also indicate which phis are needed
+ to merge the blocks.
+
+ For the moment, we don't do block value numbering, but we do insn-by-insn
+ matching, using scc value numbers to match operations with results, and
+ structural comparison otherwise, while ignoring vop mismatches.
+
+
+ IMPLEMENTATION
+
+ 1. The pass first determines all groups of blocks with the same successor
+ blocks.
+ 2. Within each group, it tries to determine clusters of equal basic blocks.
+ 3. The clusters are applied.
+ 4. The same successor groups are updated.
+ 5. This process is repeated from 2 onwards, until no more changes.
+
+
+ LIMITATIONS/TODO
+
+ - block only
+ - handles only 'same operations, same successors'.
+ It handles same predecessors as a special subcase though.
+ - does not implement the reverse value numbering and block value numbering.
+ - improve memory allocation: use garbage collected memory, obstacks,
+ allocpools where appropriate.
+ - no insertion of gimple_reg phis, We only introduce vop-phis.
+ - handle blocks with gimple_reg phi_nodes.
+
+
+ SWITCHES
+
+ - ftree-tail-merge. On at -O2. We may have to enable it only at -Os. */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tm.h"
+#include "tree.h"
+#include "tm_p.h"
+#include "basic-block.h"
+#include "output.h"
+#include "flags.h"
+#include "function.h"
+#include "tree-flow.h"
+#include "timevar.h"
+#include "bitmap.h"
+#include "tree-ssa-alias.h"
+#include "params.h"
+#include "tree-pretty-print.h"
+#include "hashtab.h"
+#include "gimple-pretty-print.h"
+#include "tree-ssa-sccvn.h"
+#include "tree-dump.h"
+
+/* Describes a group of bbs with the same successors. The successor bbs are
+ cached in succs, and the successor edge flags are cached in succ_flags.
+ If a bb has the EDGE_TRUE/VALSE_VALUE flags swapped compared to succ_flags,
+ it's marked in inverse.
+ Additionally, the hash value for the struct is cached in hashval, and
+ in_worklist indicates whether it's currently part of worklist. */
+
+struct same_succ_def
+{
+ /* The bbs that have the same successor bbs. */
+ bitmap bbs;
+ /* The successor bbs. */
+ bitmap succs;
+ /* Indicates whether the EDGE_TRUE/FALSE_VALUEs of succ_flags are swapped for
+ bb. */
+ bitmap inverse;
+ /* The edge flags for each of the successor bbs. */
+ VEC (int, heap) *succ_flags;
+ /* Indicates whether the struct is currently in the worklist. */
+ bool in_worklist;
+ /* The hash value of the struct. */
+ hashval_t hashval;
+};
+typedef struct same_succ_def *same_succ;
+typedef const struct same_succ_def *const_same_succ;
+
+/* A group of bbs where 1 bb from bbs can replace the other bbs. */
+
+struct bb_cluster_def
+{
+ /* The bbs in the cluster. */
+ bitmap bbs;
+ /* The preds of the bbs in the cluster. */
+ bitmap preds;
+ /* Index in all_clusters vector. */
+ int index;
+ /* The bb to replace the cluster with. */
+ basic_block rep_bb;
+};
+typedef struct bb_cluster_def *bb_cluster;
+typedef const struct bb_cluster_def *const_bb_cluster;
+
+/* Per bb-info. */
+
+struct aux_bb_info
+{
+ /* The number of non-debug statements in the bb. */
+ int size;
+ /* The same_succ that this bb is a member of. */
+ same_succ bb_same_succ;
+ /* The cluster that this bb is a member of. */
+ bb_cluster cluster;
+ /* The vop state at the exit of a bb. This is shortlived data, used to
+ communicate data between update_block_by and update_vuses. */
+ tree vop_at_exit;
+ /* The bb that either contains or is dominated by the dependencies of the
+ bb. */
+ basic_block dep_bb;
+};
+
+/* Macros to access the fields of struct aux_bb_info. */
+
+#define BB_SIZE(bb) (((struct aux_bb_info *)bb->aux)->size)
+#define BB_SAME_SUCC(bb) (((struct aux_bb_info *)bb->aux)->bb_same_succ)
+#define BB_CLUSTER(bb) (((struct aux_bb_info *)bb->aux)->cluster)
+#define BB_VOP_AT_EXIT(bb) (((struct aux_bb_info *)bb->aux)->vop_at_exit)
+#define BB_DEP_BB(bb) (((struct aux_bb_info *)bb->aux)->dep_bb)
+
+/* VAL1 and VAL2 are either:
+ - uses in BB1 and BB2, or
+ - phi alternatives for BB1 and BB2.
+ Return true if the uses have the same gvn value. */
+
+static bool
+gvn_uses_equal (tree val1, tree val2)
+{
+ gcc_checking_assert (val1 != NULL_TREE && val2 != NULL_TREE);
+
+ if (val1 == val2)
+ return true;
+
+ if (vn_valueize (val1) != vn_valueize (val2))
+ return false;
+
+ return ((TREE_CODE (val1) == SSA_NAME || CONSTANT_CLASS_P (val1))
+ && (TREE_CODE (val2) == SSA_NAME || CONSTANT_CLASS_P (val2)));
+}
+
+/* Prints E to FILE. */
+
+static void
+same_succ_print (FILE *file, const same_succ e)
+{
+ unsigned int i;
+ bitmap_print (file, e->bbs, "bbs:", "\n");
+ bitmap_print (file, e->succs, "succs:", "\n");
+ bitmap_print (file, e->inverse, "inverse:", "\n");
+ fprintf (file, "flags:");
+ for (i = 0; i < VEC_length (int, e->succ_flags); ++i)
+ fprintf (file, " %x", VEC_index (int, e->succ_flags, i));
+ fprintf (file, "\n");
+}
+
+/* Prints same_succ VE to VFILE. */
+
+static int
+same_succ_print_traverse (void **ve, void *vfile)
+{
+ const same_succ e = *((const same_succ *)ve);
+ FILE *file = ((FILE*)vfile);
+ same_succ_print (file, e);
+ return 1;
+}
+
+/* Update BB_DEP_BB (USE_BB), given a use of VAL in USE_BB. */
+
+static void
+update_dep_bb (basic_block use_bb, tree val)
+{
+ basic_block dep_bb;
+
+ /* Not a dep. */
+ if (TREE_CODE (val) != SSA_NAME)
+ return;
+
+ /* Skip use of global def. */
+ if (SSA_NAME_IS_DEFAULT_DEF (val))
+ return;
+
+ /* Skip use of local def. */
+ dep_bb = gimple_bb (SSA_NAME_DEF_STMT (val));
+ if (dep_bb == use_bb)
+ return;
+
+ if (BB_DEP_BB (use_bb) == NULL
+ || dominated_by_p (CDI_DOMINATORS, dep_bb, BB_DEP_BB (use_bb)))
+ BB_DEP_BB (use_bb) = dep_bb;
+}
+
+/* Update BB_DEP_BB, given the dependencies in STMT. */
+
+static void
+stmt_update_dep_bb (gimple stmt)
+{
+ ssa_op_iter iter;
+ use_operand_p use;
+
+ FOR_EACH_SSA_USE_OPERAND (use, stmt, iter, SSA_OP_USE)
+ update_dep_bb (gimple_bb (stmt), USE_FROM_PTR (use));
+}
+
+/* Returns whether VAL is used in the same bb as in which it is defined, or
+ in the phi of a successor bb. */
+
+static bool
+local_def (tree val)
+{
+ gimple stmt, def_stmt;
+ basic_block bb, def_bb;
+ imm_use_iterator iter;
+ bool res;
+
+ if (TREE_CODE (val) != SSA_NAME)
+ return false;
+ def_stmt = SSA_NAME_DEF_STMT (val);
+ def_bb = gimple_bb (def_stmt);
+
+ res = true;
+ FOR_EACH_IMM_USE_STMT (stmt, iter, val)
+ {
+ bb = gimple_bb (stmt);
+ if (bb == def_bb)
+ continue;
+ if (gimple_code (stmt) == GIMPLE_PHI
+ && find_edge (def_bb, bb))
+ continue;
+ res = false;
+ BREAK_FROM_IMM_USE_STMT (iter);
+ }
+ return res;
+}
+
+/* Calculates hash value for same_succ VE. */
+
+static hashval_t
+same_succ_hash (const void *ve)
+{
+ const_same_succ e = (const_same_succ)ve;
+ hashval_t hashval = bitmap_hash (e->succs);
+ int flags;
+ unsigned int i;
+ unsigned int first = bitmap_first_set_bit (e->bbs);
+ basic_block bb = BASIC_BLOCK (first);
+ int size = 0;
+ gimple_stmt_iterator gsi;
+ gimple stmt;
+ tree arg;
+ unsigned int s;
+ bitmap_iterator bs;
+
+ for (gsi = gsi_start_nondebug_bb (bb);
+ !gsi_end_p (gsi); gsi_next_nondebug (&gsi))
+ {
+ stmt = gsi_stmt (gsi);
+ stmt_update_dep_bb (stmt);
+ if (is_gimple_assign (stmt) && local_def (gimple_get_lhs (stmt))
+ && !gimple_has_side_effects (stmt))
+ continue;
+ size++;
+
+ hashval = iterative_hash_hashval_t (gimple_code (stmt), hashval);
+ if (is_gimple_assign (stmt))
+ hashval = iterative_hash_hashval_t (gimple_assign_rhs_code (stmt),
+ hashval);
+ if (!is_gimple_call (stmt))
+ continue;
+ if (gimple_call_internal_p (stmt))
+ hashval = iterative_hash_hashval_t
+ ((hashval_t) gimple_call_internal_fn (stmt), hashval);
+ else
+ hashval = iterative_hash_expr (gimple_call_fn (stmt), hashval);
+ for (i = 0; i < gimple_call_num_args (stmt); i++)
+ {
+ arg = gimple_call_arg (stmt, i);
+ arg = vn_valueize (arg);
+ hashval = iterative_hash_expr (arg, hashval);
+ }
+ }
+
+ hashval = iterative_hash_hashval_t (size, hashval);
+ BB_SIZE (bb) = size;
+
+ for (i = 0; i < VEC_length (int, e->succ_flags); ++i)
+ {
+ flags = VEC_index (int, e->succ_flags, i);
+ flags = flags & ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE);
+ hashval = iterative_hash_hashval_t (flags, hashval);
+ }
+
+ EXECUTE_IF_SET_IN_BITMAP (e->succs, 0, s, bs)
+ {
+ int n = find_edge (bb, BASIC_BLOCK (s))->dest_idx;
+ for (gsi = gsi_start_phis (BASIC_BLOCK (s)); !gsi_end_p (gsi);
+ gsi_next (&gsi))
+ {
+ gimple phi = gsi_stmt (gsi);
+ tree lhs = gimple_phi_result (phi);
+ tree val = gimple_phi_arg_def (phi, n);
+
+ if (!is_gimple_reg (lhs))
+ continue;
+ update_dep_bb (bb, val);
+ }
+ }
+
+ return hashval;
+}
+
+/* Returns true if E1 and E2 have 2 successors, and if the successor flags
+ are inverse for the EDGE_TRUE_VALUE and EDGE_FALSE_VALUE flags, and equal for
+ the other edge flags. */
+
+static bool
+inverse_flags (const_same_succ e1, const_same_succ e2)
+{
+ int f1a, f1b, f2a, f2b;
+ int mask = ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE);
+
+ if (VEC_length (int, e1->succ_flags) != 2)
+ return false;
+
+ f1a = VEC_index (int, e1->succ_flags, 0);
+ f1b = VEC_index (int, e1->succ_flags, 1);
+ f2a = VEC_index (int, e2->succ_flags, 0);
+ f2b = VEC_index (int, e2->succ_flags, 1);
+
+ if (f1a == f2a && f1b == f2b)
+ return false;
+
+ return (f1a & mask) == (f2a & mask) && (f1b & mask) == (f2b & mask);
+}
+
+/* Compares SAME_SUCCs VE1 and VE2. */
+
+static int
+same_succ_equal (const void *ve1, const void *ve2)
+{
+ const_same_succ e1 = (const_same_succ)ve1;
+ const_same_succ e2 = (const_same_succ)ve2;
+ unsigned int i, first1, first2;
+ gimple_stmt_iterator gsi1, gsi2;
+ gimple s1, s2;
+ basic_block bb1, bb2;
+
+ if (e1->hashval != e2->hashval)
+ return 0;
+
+ if (VEC_length (int, e1->succ_flags) != VEC_length (int, e2->succ_flags))
+ return 0;
+
+ if (!bitmap_equal_p (e1->succs, e2->succs))
+ return 0;
+
+ if (!inverse_flags (e1, e2))
+ {
+ for (i = 0; i < VEC_length (int, e1->succ_flags); ++i)
+ if (VEC_index (int, e1->succ_flags, i)
+ != VEC_index (int, e1->succ_flags, i))
+ return 0;
+ }
+
+ first1 = bitmap_first_set_bit (e1->bbs);
+ first2 = bitmap_first_set_bit (e2->bbs);
+
+ bb1 = BASIC_BLOCK (first1);
+ bb2 = BASIC_BLOCK (first2);
+
+ if (BB_SIZE (bb1) != BB_SIZE (bb2))
+ return 0;
+
+ gsi1 = gsi_start_nondebug_bb (bb1);
+ gsi2 = gsi_start_nondebug_bb (bb2);
+ while (!(gsi_end_p (gsi1) || gsi_end_p (gsi2)))
+ {
+ s1 = gsi_stmt (gsi1);
+ s2 = gsi_stmt (gsi2);
+ if (gimple_code (s1) != gimple_code (s2))
+ return 0;
+ if (is_gimple_call (s1) && !gimple_call_same_target_p (s1, s2))
+ return 0;
+ gsi_next_nondebug (&gsi1);
+ gsi_next_nondebug (&gsi2);
+ }
+
+ return 1;
+}
+
+/* Alloc and init a new SAME_SUCC. */
+
+static same_succ
+same_succ_alloc (void)
+{
+ same_succ same = XNEW (struct same_succ_def);
+
+ same->bbs = BITMAP_ALLOC (NULL);
+ same->succs = BITMAP_ALLOC (NULL);
+ same->inverse = BITMAP_ALLOC (NULL);
+ same->succ_flags = VEC_alloc (int, heap, 10);
+ same->in_worklist = false;
+
+ return same;
+}
+
+/* Delete same_succ VE. */
+
+static void
+same_succ_delete (void *ve)
+{
+ same_succ e = (same_succ)ve;
+
+ BITMAP_FREE (e->bbs);
+ BITMAP_FREE (e->succs);
+ BITMAP_FREE (e->inverse);
+ VEC_free (int, heap, e->succ_flags);
+
+ XDELETE (ve);
+}
+
+/* Reset same_succ SAME. */
+
+static void
+same_succ_reset (same_succ same)
+{
+ bitmap_clear (same->bbs);
+ bitmap_clear (same->succs);
+ bitmap_clear (same->inverse);
+ VEC_truncate (int, same->succ_flags, 0);
+}
+
+/* Hash table with all same_succ entries. */
+
+static htab_t same_succ_htab;
+
+/* Array that is used to store the edge flags for a successor. */
+
+static int *same_succ_edge_flags;
+
+/* Bitmap that is used to mark bbs that are recently deleted. */
+
+static bitmap deleted_bbs;
+
+/* Bitmap that is used to mark predecessors of bbs that are
+ deleted. */
+
+static bitmap deleted_bb_preds;
+
+/* Prints same_succ_htab to stderr. */
+
+extern void debug_same_succ (void);
+DEBUG_FUNCTION void
+debug_same_succ ( void)
+{
+ htab_traverse (same_succ_htab, same_succ_print_traverse, stderr);
+}
+
+DEF_VEC_P (same_succ);
+DEF_VEC_ALLOC_P (same_succ, heap);
+
+/* Vector of bbs to process. */
+
+static VEC (same_succ, heap) *worklist;
+
+/* Prints worklist to FILE. */
+
+static void
+print_worklist (FILE *file)
+{
+ unsigned int i;
+ for (i = 0; i < VEC_length (same_succ, worklist); ++i)
+ same_succ_print (file, VEC_index (same_succ, worklist, i));
+}
+
+/* Adds SAME to worklist. */
+
+static void
+add_to_worklist (same_succ same)
+{
+ if (same->in_worklist)
+ return;
+
+ if (bitmap_count_bits (same->bbs) < 2)
+ return;
+
+ same->in_worklist = true;
+ VEC_safe_push (same_succ, heap, worklist, same);
+}
+
+/* Add BB to same_succ_htab. */
+
+static void
+find_same_succ_bb (basic_block bb, same_succ *same_p)
+{
+ unsigned int j;
+ bitmap_iterator bj;
+ same_succ same = *same_p;
+ same_succ *slot;
+ edge_iterator ei;
+ edge e;
+
+ if (bb == NULL)
+ return;
+ bitmap_set_bit (same->bbs, bb->index);
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ {
+ int index = e->dest->index;
+ bitmap_set_bit (same->succs, index);
+ same_succ_edge_flags[index] = e->flags;
+ }
+ EXECUTE_IF_SET_IN_BITMAP (same->succs, 0, j, bj)
+ VEC_safe_push (int, heap, same->succ_flags, same_succ_edge_flags[j]);
+
+ same->hashval = same_succ_hash (same);
+
+ slot = (same_succ *) htab_find_slot_with_hash (same_succ_htab, same,
+ same->hashval, INSERT);
+ if (*slot == NULL)
+ {
+ *slot = same;
+ BB_SAME_SUCC (bb) = same;
+ add_to_worklist (same);
+ *same_p = NULL;
+ }
+ else
+ {
+ bitmap_set_bit ((*slot)->bbs, bb->index);
+ BB_SAME_SUCC (bb) = *slot;
+ add_to_worklist (*slot);
+ if (inverse_flags (same, *slot))
+ bitmap_set_bit ((*slot)->inverse, bb->index);
+ same_succ_reset (same);
+ }
+}
+
+/* Find bbs with same successors. */
+
+static void
+find_same_succ (void)
+{
+ same_succ same = same_succ_alloc ();
+ basic_block bb;
+
+ FOR_EACH_BB (bb)
+ {
+ find_same_succ_bb (bb, &same);
+ if (same == NULL)
+ same = same_succ_alloc ();
+ }
+
+ same_succ_delete (same);
+}
+
+/* Initializes worklist administration. */
+
+static void
+init_worklist (void)
+{
+ alloc_aux_for_blocks (sizeof (struct aux_bb_info));
+ same_succ_htab
+ = htab_create (n_basic_blocks, same_succ_hash, same_succ_equal,
+ same_succ_delete);
+ same_succ_edge_flags = XCNEWVEC (int, last_basic_block);
+ deleted_bbs = BITMAP_ALLOC (NULL);
+ deleted_bb_preds = BITMAP_ALLOC (NULL);
+ worklist = VEC_alloc (same_succ, heap, n_basic_blocks);
+ find_same_succ ();
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "initial worklist:\n");
+ print_worklist (dump_file);
+ }
+}
+
+/* Deletes worklist administration. */
+
+static void
+delete_worklist (void)
+{
+ free_aux_for_blocks ();
+ htab_delete (same_succ_htab);
+ same_succ_htab = NULL;
+ XDELETEVEC (same_succ_edge_flags);
+ same_succ_edge_flags = NULL;
+ BITMAP_FREE (deleted_bbs);
+ BITMAP_FREE (deleted_bb_preds);
+ VEC_free (same_succ, heap, worklist);
+}
+
+/* Mark BB as deleted, and mark its predecessors. */
+
+static void
+delete_basic_block_same_succ (basic_block bb)
+{
+ edge e;
+ edge_iterator ei;
+
+ bitmap_set_bit (deleted_bbs, bb->index);
+
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ bitmap_set_bit (deleted_bb_preds, e->src->index);
+}
+
+/* Removes all bbs in BBS from their corresponding same_succ. */
+
+static void
+same_succ_flush_bbs (bitmap bbs)
+{
+ unsigned int i;
+ bitmap_iterator bi;
+
+ EXECUTE_IF_SET_IN_BITMAP (bbs, 0, i, bi)
+ {
+ basic_block bb = BASIC_BLOCK (i);
+ same_succ same = BB_SAME_SUCC (bb);
+ BB_SAME_SUCC (bb) = NULL;
+ if (bitmap_single_bit_set_p (same->bbs))
+ htab_remove_elt_with_hash (same_succ_htab, same, same->hashval);
+ else
+ bitmap_clear_bit (same->bbs, i);
+ }
+}
+
+/* Delete all deleted_bbs. */
+
+static void
+purge_bbs (void)
+{
+ unsigned int i;
+ bitmap_iterator bi;
+
+ same_succ_flush_bbs (deleted_bbs);
+
+ EXECUTE_IF_SET_IN_BITMAP (deleted_bbs, 0, i, bi)
+ delete_basic_block (BASIC_BLOCK (i));
+
+ bitmap_and_compl_into (deleted_bb_preds, deleted_bbs);
+ bitmap_clear (deleted_bbs);
+}
+
+/* For deleted_bb_preds, find bbs with same successors. */
+
+static void
+update_worklist (void)
+{
+ unsigned int i;
+ bitmap_iterator bi;
+ basic_block bb;
+ same_succ same;
+
+ bitmap_clear_bit (deleted_bb_preds, ENTRY_BLOCK);
+ same_succ_flush_bbs (deleted_bb_preds);
+
+ same = same_succ_alloc ();
+ EXECUTE_IF_SET_IN_BITMAP (deleted_bb_preds, 0, i, bi)
+ {
+ bb = BASIC_BLOCK (i);
+ gcc_assert (bb != NULL);
+ find_same_succ_bb (bb, &same);
+ if (same == NULL)
+ same = same_succ_alloc ();
+ }
+ same_succ_delete (same);
+ bitmap_clear (deleted_bb_preds);
+}
+
+/* Prints cluster C to FILE. */
+
+static void
+print_cluster (FILE *file, bb_cluster c)
+{
+ if (c == NULL)
+ return;
+ bitmap_print (file, c->bbs, "bbs:", "\n");
+ bitmap_print (file, c->preds, "preds:", "\n");
+}
+
+/* Prints cluster C to stderr. */
+
+extern void debug_cluster (bb_cluster);
+DEBUG_FUNCTION void
+debug_cluster (bb_cluster c)
+{
+ print_cluster (stderr, c);
+}
+
+/* Update C->rep_bb, given that BB is added to the cluster. */
+
+static void
+update_rep_bb (bb_cluster c, basic_block bb)
+{
+ /* Initial. */
+ if (c->rep_bb == NULL)
+ {
+ c->rep_bb = bb;
+ return;
+ }
+
+ /* Current needs no deps, keep it. */
+ if (BB_DEP_BB (c->rep_bb) == NULL)
+ return;
+
+ /* Bb needs no deps, change rep_bb. */
+ if (BB_DEP_BB (bb) == NULL)
+ {
+ c->rep_bb = bb;
+ return;
+ }
+
+ /* Bb needs last deps earlier than current, change rep_bb. A potential
+ problem with this, is that the first deps might also be earlier, which
+ would mean we prefer longer lifetimes for the deps. To be able to check
+ for this, we would have to trace BB_FIRST_DEP_BB as well, besides
+ BB_DEP_BB, which is really BB_LAST_DEP_BB.
+ The benefit of choosing the bb with last deps earlier, is that it can
+ potentially be used as replacement for more bbs. */
+ if (dominated_by_p (CDI_DOMINATORS, BB_DEP_BB (c->rep_bb), BB_DEP_BB (bb)))
+ c->rep_bb = bb;
+}
+
+/* Add BB to cluster C. Sets BB in C->bbs, and preds of BB in C->preds. */
+
+static void
+add_bb_to_cluster (bb_cluster c, basic_block bb)
+{
+ edge e;
+ edge_iterator ei;
+
+ bitmap_set_bit (c->bbs, bb->index);
+
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ bitmap_set_bit (c->preds, e->src->index);
+
+ update_rep_bb (c, bb);
+}
+
+/* Allocate and init new cluster. */
+
+static bb_cluster
+new_cluster (void)
+{
+ bb_cluster c;
+ c = XCNEW (struct bb_cluster_def);
+ c->bbs = BITMAP_ALLOC (NULL);
+ c->preds = BITMAP_ALLOC (NULL);
+ c->rep_bb = NULL;
+ return c;
+}
+
+/* Delete clusters. */
+
+static void
+delete_cluster (bb_cluster c)
+{
+ if (c == NULL)
+ return;
+ BITMAP_FREE (c->bbs);
+ BITMAP_FREE (c->preds);
+ XDELETE (c);
+}
+
+DEF_VEC_P (bb_cluster);
+DEF_VEC_ALLOC_P (bb_cluster, heap);
+
+/* Array that contains all clusters. */
+
+static VEC (bb_cluster, heap) *all_clusters;
+
+/* Allocate all cluster vectors. */
+
+static void
+alloc_cluster_vectors (void)
+{
+ all_clusters = VEC_alloc (bb_cluster, heap, n_basic_blocks);
+}
+
+/* Reset all cluster vectors. */
+
+static void
+reset_cluster_vectors (void)
+{
+ unsigned int i;
+ basic_block bb;
+ for (i = 0; i < VEC_length (bb_cluster, all_clusters); ++i)
+ delete_cluster (VEC_index (bb_cluster, all_clusters, i));
+ VEC_truncate (bb_cluster, all_clusters, 0);
+ FOR_EACH_BB (bb)
+ BB_CLUSTER (bb) = NULL;
+}
+
+/* Delete all cluster vectors. */
+
+static void
+delete_cluster_vectors (void)
+{
+ unsigned int i;
+ for (i = 0; i < VEC_length (bb_cluster, all_clusters); ++i)
+ delete_cluster (VEC_index (bb_cluster, all_clusters, i));
+ VEC_free (bb_cluster, heap, all_clusters);
+}
+
+/* Merge cluster C2 into C1. */
+
+static void
+merge_clusters (bb_cluster c1, bb_cluster c2)
+{
+ bitmap_ior_into (c1->bbs, c2->bbs);
+ bitmap_ior_into (c1->preds, c2->preds);
+}
+
+/* Register equivalence of BB1 and BB2 (members of cluster C). Store c in
+ all_clusters, or merge c with existing cluster. */
+
+static void
+set_cluster (basic_block bb1, basic_block bb2)
+{
+ basic_block merge_bb, other_bb;
+ bb_cluster merge, old, c;
+
+ if (BB_CLUSTER (bb1) == NULL && BB_CLUSTER (bb2) == NULL)
+ {
+ c = new_cluster ();
+ add_bb_to_cluster (c, bb1);
+ add_bb_to_cluster (c, bb2);
+ BB_CLUSTER (bb1) = c;
+ BB_CLUSTER (bb2) = c;
+ c->index = VEC_length (bb_cluster, all_clusters);
+ VEC_safe_push (bb_cluster, heap, all_clusters, c);
+ }
+ else if (BB_CLUSTER (bb1) == NULL || BB_CLUSTER (bb2) == NULL)
+ {
+ merge_bb = BB_CLUSTER (bb1) == NULL ? bb2 : bb1;
+ other_bb = BB_CLUSTER (bb1) == NULL ? bb1 : bb2;
+ merge = BB_CLUSTER (merge_bb);
+ add_bb_to_cluster (merge, other_bb);
+ BB_CLUSTER (other_bb) = merge;
+ }
+ else if (BB_CLUSTER (bb1) != BB_CLUSTER (bb2))
+ {
+ unsigned int i;
+ bitmap_iterator bi;
+
+ old = BB_CLUSTER (bb2);
+ merge = BB_CLUSTER (bb1);
+ merge_clusters (merge, old);
+ EXECUTE_IF_SET_IN_BITMAP (old->bbs, 0, i, bi)
+ BB_CLUSTER (BASIC_BLOCK (i)) = merge;
+ VEC_replace (bb_cluster, all_clusters, old->index, NULL);
+ update_rep_bb (merge, old->rep_bb);
+ delete_cluster (old);
+ }
+ else
+ gcc_unreachable ();
+}
+
+/* Return true if gimple statements S1 and S2 are equal. Gimple_bb (s1) and
+ gimple_bb (s2) are members of SAME_SUCC. */
+
+static bool
+gimple_equal_p (same_succ same_succ, gimple s1, gimple s2)
+{
+ unsigned int i;
+ tree lhs1, lhs2;
+ basic_block bb1 = gimple_bb (s1), bb2 = gimple_bb (s2);
+ tree t1, t2;
+ bool equal, inv_cond;
+ enum tree_code code1, code2;
+
+ if (gimple_code (s1) != gimple_code (s2))
+ return false;
+
+ switch (gimple_code (s1))
+ {
+ case GIMPLE_CALL:
+ if (gimple_call_num_args (s1) != gimple_call_num_args (s2))
+ return false;
+ if (!gimple_call_same_target_p (s1, s2))
+ return false;
+
+ equal = true;
+ for (i = 0; i < gimple_call_num_args (s1); ++i)
+ {
+ t1 = gimple_call_arg (s1, i);
+ t2 = gimple_call_arg (s2, i);
+ if (operand_equal_p (t1, t2, 0))
+ continue;
+ if (gvn_uses_equal (t1, t2))
+ continue;
+ equal = false;
+ break;
+ }
+ if (equal)
+ return true;
+
+ lhs1 = gimple_get_lhs (s1);
+ lhs2 = gimple_get_lhs (s2);
+ return (lhs1 != NULL_TREE && lhs2 != NULL_TREE
+ && TREE_CODE (lhs1) == SSA_NAME && TREE_CODE (lhs2) == SSA_NAME
+ && vn_valueize (lhs1) == vn_valueize (lhs2));
+
+ case GIMPLE_ASSIGN:
+ lhs1 = gimple_get_lhs (s1);
+ lhs2 = gimple_get_lhs (s2);
+ return (TREE_CODE (lhs1) == SSA_NAME
+ && TREE_CODE (lhs2) == SSA_NAME
+ && vn_valueize (lhs1) == vn_valueize (lhs2));
+
+ case GIMPLE_COND:
+ t1 = gimple_cond_lhs (s1);
+ t2 = gimple_cond_lhs (s2);
+ if (!operand_equal_p (t1, t2, 0)
+ && !gvn_uses_equal (t1, t2))
+ return false;
+
+ t1 = gimple_cond_rhs (s1);
+ t2 = gimple_cond_rhs (s2);
+ if (!operand_equal_p (t1, t2, 0)
+ && !gvn_uses_equal (t1, t2))
+ return false;
+
+ code1 = gimple_expr_code (s1);
+ code2 = gimple_expr_code (s2);
+ inv_cond = (bitmap_bit_p (same_succ->inverse, bb1->index)
+ != bitmap_bit_p (same_succ->inverse, bb2->index));
+ if (inv_cond)
+ {
+ bool honor_nans
+ = HONOR_NANS (TYPE_MODE (TREE_TYPE (gimple_cond_lhs (s1))));
+ code2 = invert_tree_comparison (code2, honor_nans);
+ }
+ return code1 == code2;
+
+ default:
+ return false;
+ }
+}
+
+/* Let GSI skip backwards over local defs. */
+
+static void
+gsi_advance_bw_nondebug_nonlocal (gimple_stmt_iterator *gsi)
+{
+ gimple stmt;
+
+ while (true)
+ {
+ if (gsi_end_p (*gsi))
+ return;
+ stmt = gsi_stmt (*gsi);
+ if (!(is_gimple_assign (stmt) && local_def (gimple_get_lhs (stmt))
+ && !gimple_has_side_effects (stmt)))
+ return;
+ gsi_prev_nondebug (gsi);
+ }
+}
+
+/* Determines whether BB1 and BB2 (members of same_succ) are duplicates. If so,
+ clusters them. */
+
+static void
+find_duplicate (same_succ same_succ, basic_block bb1, basic_block bb2)
+{
+ gimple_stmt_iterator gsi1 = gsi_last_nondebug_bb (bb1);
+ gimple_stmt_iterator gsi2 = gsi_last_nondebug_bb (bb2);
+
+ gsi_advance_bw_nondebug_nonlocal (&gsi1);
+ gsi_advance_bw_nondebug_nonlocal (&gsi2);
+
+ while (!gsi_end_p (gsi1) && !gsi_end_p (gsi2))
+ {
+ if (!gimple_equal_p (same_succ, gsi_stmt (gsi1), gsi_stmt (gsi2)))
+ return;
+
+ gsi_prev_nondebug (&gsi1);
+ gsi_prev_nondebug (&gsi2);
+ gsi_advance_bw_nondebug_nonlocal (&gsi1);
+ gsi_advance_bw_nondebug_nonlocal (&gsi2);
+ }
+
+ if (!(gsi_end_p (gsi1) && gsi_end_p (gsi2)))
+ return;
+
+ if (dump_file)
+ fprintf (dump_file, "find_duplicates: <bb %d> duplicate of <bb %d>\n",
+ bb1->index, bb2->index);
+
+ set_cluster (bb1, bb2);
+}
+
+/* Returns whether for all phis in DEST the phi alternatives for E1 and
+ E2 are equal. */
+
+static bool
+same_phi_alternatives_1 (basic_block dest, edge e1, edge e2)
+{
+ int n1 = e1->dest_idx, n2 = e2->dest_idx;
+ gimple_stmt_iterator gsi;
+
+ for (gsi = gsi_start_phis (dest); !gsi_end_p (gsi); gsi_next (&gsi))
+ {
+ gimple phi = gsi_stmt (gsi);
+ tree lhs = gimple_phi_result (phi);
+ tree val1 = gimple_phi_arg_def (phi, n1);
+ tree val2 = gimple_phi_arg_def (phi, n2);
+
+ if (!is_gimple_reg (lhs))
+ continue;
+
+ if (operand_equal_for_phi_arg_p (val1, val2))
+ continue;
+ if (gvn_uses_equal (val1, val2))
+ continue;
+
+ return false;
+ }
+
+ return true;
+}
+
+/* Returns whether for all successors of BB1 and BB2 (members of SAME_SUCC), the
+ phi alternatives for BB1 and BB2 are equal. */
+
+static bool
+same_phi_alternatives (same_succ same_succ, basic_block bb1, basic_block bb2)
+{
+ unsigned int s;
+ bitmap_iterator bs;
+ edge e1, e2;
+ basic_block succ;
+
+ EXECUTE_IF_SET_IN_BITMAP (same_succ->succs, 0, s, bs)
+ {
+ succ = BASIC_BLOCK (s);
+ e1 = find_edge (bb1, succ);
+ e2 = find_edge (bb2, succ);
+ if (e1->flags & EDGE_COMPLEX
+ || e2->flags & EDGE_COMPLEX)
+ return false;
+
+ /* For all phis in bb, the phi alternatives for e1 and e2 need to have
+ the same value. */
+ if (!same_phi_alternatives_1 (succ, e1, e2))
+ return false;
+ }
+
+ return true;
+}
+
+/* Return true if BB has non-vop phis. */
+
+static bool
+bb_has_non_vop_phi (basic_block bb)
+{
+ gimple_seq phis = phi_nodes (bb);
+ gimple phi;
+
+ if (phis == NULL)
+ return false;
+
+ if (!gimple_seq_singleton_p (phis))
+ return true;
+
+ phi = gimple_seq_first_stmt (phis);
+ return is_gimple_reg (gimple_phi_result (phi));
+}
+
+/* Returns true if redirecting the incoming edges of FROM to TO maintains the
+ invariant that uses in FROM are dominates by their defs. */
+
+static bool
+deps_ok_for_redirect_from_bb_to_bb (basic_block from, basic_block to)
+{
+ basic_block cd, dep_bb = BB_DEP_BB (to);
+ edge_iterator ei;
+ edge e;
+ bitmap from_preds = BITMAP_ALLOC (NULL);
+
+ if (dep_bb == NULL)
+ return true;
+
+ FOR_EACH_EDGE (e, ei, from->preds)
+ bitmap_set_bit (from_preds, e->src->index);
+ cd = nearest_common_dominator_for_set (CDI_DOMINATORS, from_preds);
+ BITMAP_FREE (from_preds);
+
+ return dominated_by_p (CDI_DOMINATORS, dep_bb, cd);
+}
+
+/* Returns true if replacing BB1 (or its replacement bb) by BB2 (or its
+ replacement bb) and vice versa maintains the invariant that uses in the
+ replacement are dominates by their defs. */
+
+static bool
+deps_ok_for_redirect (basic_block bb1, basic_block bb2)
+{
+ if (BB_CLUSTER (bb1) != NULL)
+ bb1 = BB_CLUSTER (bb1)->rep_bb;
+
+ if (BB_CLUSTER (bb2) != NULL)
+ bb2 = BB_CLUSTER (bb2)->rep_bb;
+
+ return (deps_ok_for_redirect_from_bb_to_bb (bb1, bb2)
+ && deps_ok_for_redirect_from_bb_to_bb (bb2, bb1));
+}
+
+/* Within SAME_SUCC->bbs, find clusters of bbs which can be merged. */
+
+static void
+find_clusters_1 (same_succ same_succ)
+{
+ basic_block bb1, bb2;
+ unsigned int i, j;
+ bitmap_iterator bi, bj;
+ int nr_comparisons;
+ int max_comparisons = PARAM_VALUE (PARAM_MAX_TAIL_MERGE_COMPARISONS);
+
+ EXECUTE_IF_SET_IN_BITMAP (same_succ->bbs, 0, i, bi)
+ {
+ bb1 = BASIC_BLOCK (i);
+
+ /* TODO: handle blocks with phi-nodes. We'll have to find corresponding
+ phi-nodes in bb1 and bb2, with the same alternatives for the same
+ preds. */
+ if (bb_has_non_vop_phi (bb1))
+ continue;
+
+ nr_comparisons = 0;
+ EXECUTE_IF_SET_IN_BITMAP (same_succ->bbs, i + 1, j, bj)
+ {
+ bb2 = BASIC_BLOCK (j);
+
+ if (bb_has_non_vop_phi (bb2))
+ continue;
+
+ if (BB_CLUSTER (bb1) != NULL && BB_CLUSTER (bb1) == BB_CLUSTER (bb2))
+ continue;
+
+ /* Limit quadratic behaviour. */
+ nr_comparisons++;
+ if (nr_comparisons > max_comparisons)
+ break;
+
+ /* This is a conservative dependency check. We could test more
+ precise for allowed replacement direction. */
+ if (!deps_ok_for_redirect (bb1, bb2))
+ continue;
+
+ if (!(same_phi_alternatives (same_succ, bb1, bb2)))
+ continue;
+
+ find_duplicate (same_succ, bb1, bb2);
+ }
+ }
+}
+
+/* Find clusters of bbs which can be merged. */
+
+static void
+find_clusters (void)
+{
+ same_succ same;
+
+ while (!VEC_empty (same_succ, worklist))
+ {
+ same = VEC_pop (same_succ, worklist);
+ same->in_worklist = false;
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "processing worklist entry\n");
+ same_succ_print (dump_file, same);
+ }
+ find_clusters_1 (same);
+ }
+}
+
+/* Create or update a vop phi in BB2. Use VUSE1 arguments for all the
+ REDIRECTED_EDGES, or if VUSE1 is NULL_TREE, use BB_VOP_AT_EXIT. If a new
+ phis is created, use the phi instead of VUSE2 in BB2. */
+
+static void
+update_vuses (tree vuse1, tree vuse2, basic_block bb2,
+ VEC (edge,heap) *redirected_edges)
+{
+ gimple stmt, phi = NULL;
+ tree lhs = NULL_TREE, arg;
+ unsigned int i;
+ gimple def_stmt2;
+ imm_use_iterator iter;
+ use_operand_p use_p;
+ edge_iterator ei;
+ edge e;
+
+ def_stmt2 = SSA_NAME_DEF_STMT (vuse2);
+
+ if (gimple_bb (def_stmt2) == bb2)
+ /* Update existing phi. */
+ phi = def_stmt2;
+ else
+ {
+ /* No need to create a phi with 2 equal arguments. */
+ if (vuse1 == vuse2)
+ return;
+
+ /* Create a phi. */
+ lhs = make_ssa_name (SSA_NAME_VAR (vuse2), NULL);
+ VN_INFO_GET (lhs);
+ phi = create_phi_node (lhs, bb2);
+ SSA_NAME_DEF_STMT (lhs) = phi;
+
+ /* Set default argument vuse2 for all preds. */
+ FOR_EACH_EDGE (e, ei, bb2->preds)
+ add_phi_arg (phi, vuse2, e, UNKNOWN_LOCATION);
+ }
+
+ /* Update phi. */
+ for (i = 0; i < EDGE_COUNT (redirected_edges); ++i)
+ {
+ e = VEC_index (edge, redirected_edges, i);
+ if (vuse1 != NULL_TREE)
+ arg = vuse1;
+ else
+ arg = BB_VOP_AT_EXIT (e->src);
+ add_phi_arg (phi, arg, e, UNKNOWN_LOCATION);
+ }
+
+ /* Return if we updated an existing phi. */
+ if (gimple_bb (def_stmt2) == bb2)
+ return;
+
+ /* Replace relevant uses of vuse2 with the newly created phi. */
+ FOR_EACH_IMM_USE_STMT (stmt, iter, vuse2)
+ {
+ if (stmt == phi)
+ continue;
+ if (gimple_code (stmt) != GIMPLE_PHI)
+ if (gimple_bb (stmt) != bb2)
+ continue;
+
+ FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
+ {
+ if (gimple_code (stmt) == GIMPLE_PHI)
+ {
+ unsigned int pred_index = PHI_ARG_INDEX_FROM_USE (use_p);
+ basic_block pred = EDGE_PRED (gimple_bb (stmt), pred_index)->src;
+ if (pred != bb2)
+ continue;
+ }
+ SET_USE (use_p, lhs);
+ update_stmt (stmt);
+ }
+ }
+}
+
+/* Returns the vop phi of BB, if any. */
+
+static gimple
+vop_phi (basic_block bb)
+{
+ gimple stmt;
+ gimple_stmt_iterator gsi;
+ for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
+ {
+ stmt = gsi_stmt (gsi);
+ if (is_gimple_reg (gimple_phi_result (stmt)))
+ continue;
+ return stmt;
+ }
+ return NULL;
+}
+
+/* Returns the vop state at the entry of BB, if found in BB or a successor
+ bb. */
+
+static tree
+vop_at_entry (basic_block bb)
+{
+ gimple bb_phi, succ_phi;
+ gimple_stmt_iterator gsi;
+ gimple stmt;
+ tree vuse, vdef;
+ basic_block succ;
+
+ bb_phi = vop_phi (bb);
+ if (bb_phi != NULL)
+ return gimple_phi_result (bb_phi);
+
+ for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
+ {
+ stmt = gsi_stmt (gsi);
+ vuse = gimple_vuse (stmt);
+ vdef = gimple_vdef (stmt);
+ if (vuse != NULL_TREE)
+ return vuse;
+ if (vdef != NULL_TREE)
+ return NULL_TREE;
+ }
+
+ if (EDGE_COUNT (bb->succs) == 0)
+ return NULL_TREE;
+
+ succ = EDGE_SUCC (bb, 0)->dest;
+ succ_phi = vop_phi (succ);
+ return (succ_phi != NULL
+ ? PHI_ARG_DEF_FROM_EDGE (succ_phi, find_edge (bb, succ))
+ : NULL_TREE);
+}
+
+/* Redirect all edges from BB1 to BB2, marks BB1 for removal, and if
+ UPDATE_VOPS, inserts vop phis. */
+
+static void
+replace_block_by (basic_block bb1, basic_block bb2, bool update_vops)
+{
+ edge pred_edge;
+ unsigned int i;
+ tree phi_vuse1 = NULL_TREE, phi_vuse2 = NULL_TREE, arg;
+ VEC (edge,heap) *redirected_edges = NULL;
+ edge e;
+ edge_iterator ei;
+
+ if (update_vops)
+ {
+ /* Find the vops at entry of bb1 and bb2. */
+ phi_vuse1 = vop_at_entry (bb1);
+ phi_vuse2 = vop_at_entry (bb2);
+
+ /* If one of the 2 not found, it means there's no need to update. */
+ update_vops = phi_vuse1 != NULL_TREE && phi_vuse2 != NULL_TREE;
+ }
+
+ if (update_vops && gimple_bb (SSA_NAME_DEF_STMT (phi_vuse1)) == bb1)
+ {
+ /* If the vop at entry of bb1 is a phi, save the phi alternatives in
+ BB_VOP_AT_EXIT, before we lose that information by redirecting the
+ edges. */
+ FOR_EACH_EDGE (e, ei, bb1->preds)
+ {
+ arg = PHI_ARG_DEF_FROM_EDGE (SSA_NAME_DEF_STMT (phi_vuse1), e);
+ BB_VOP_AT_EXIT (e->src) = arg;
+ }
+ phi_vuse1 = NULL;
+ }
+
+ /* Mark the basic block for later deletion. */
+ delete_basic_block_same_succ (bb1);
+
+ if (update_vops)
+ redirected_edges = VEC_alloc (edge, heap, 10);
+
+ /* Redirect the incoming edges of bb1 to bb2. */
+ for (i = EDGE_COUNT (bb1->preds); i > 0 ; --i)
+ {
+ pred_edge = EDGE_PRED (bb1, i - 1);
+ pred_edge = redirect_edge_and_branch (pred_edge, bb2);
+ gcc_assert (pred_edge != NULL);
+ if (update_vops)
+ VEC_safe_push (edge, heap, redirected_edges, pred_edge);
+ }
+
+ /* Update the vops. */
+ if (update_vops)
+ {
+ update_vuses (phi_vuse1, phi_vuse2, bb2, redirected_edges);
+ VEC_free (edge, heap, redirected_edges);
+ }
+}
+
+/* Bbs for which update_debug_stmt need to be called. */
+
+static bitmap update_bbs;
+
+/* For each cluster in all_clusters, merge all cluster->bbs. Returns
+ number of bbs removed. Insert vop phis if UPDATE_VOPS. */
+
+static int
+apply_clusters (bool update_vops)
+{
+ basic_block bb1, bb2;
+ bb_cluster c;
+ unsigned int i, j;
+ bitmap_iterator bj;
+ int nr_bbs_removed = 0;
+
+ for (i = 0; i < VEC_length (bb_cluster, all_clusters); ++i)
+ {
+ c = VEC_index (bb_cluster, all_clusters, i);
+ if (c == NULL)
+ continue;
+
+ bb2 = c->rep_bb;
+ bitmap_set_bit (update_bbs, bb2->index);
+
+ bitmap_clear_bit (c->bbs, bb2->index);
+ EXECUTE_IF_SET_IN_BITMAP (c->bbs, 0, j, bj)
+ {
+ bb1 = BASIC_BLOCK (j);
+ bitmap_clear_bit (update_bbs, bb1->index);
+
+ replace_block_by (bb1, bb2, update_vops);
+ nr_bbs_removed++;
+ }
+ }
+
+ return nr_bbs_removed;
+}
+
+/* Resets debug statement STMT if it has uses that are not dominated by their
+ defs. */
+
+static void
+update_debug_stmt (gimple stmt)
+{
+ use_operand_p use_p;
+ ssa_op_iter oi;
+ basic_block bbdef, bbuse;
+ gimple def_stmt;
+ tree name;
+
+ if (!gimple_debug_bind_p (stmt))
+ return;
+
+ bbuse = gimple_bb (stmt);
+ FOR_EACH_PHI_OR_STMT_USE (use_p, stmt, oi, SSA_OP_USE)
+ {
+ name = USE_FROM_PTR (use_p);
+ gcc_assert (TREE_CODE (name) == SSA_NAME);
+
+ def_stmt = SSA_NAME_DEF_STMT (name);
+ gcc_assert (def_stmt != NULL);
+
+ bbdef = gimple_bb (def_stmt);
+ if (bbdef == NULL || bbuse == bbdef
+ || dominated_by_p (CDI_DOMINATORS, bbuse, bbdef))
+ continue;
+
+ gimple_debug_bind_reset_value (stmt);
+ update_stmt (stmt);
+ }
+}
+
+/* Resets all debug statements that have uses that are not
+ dominated by their defs. */
+
+static void
+update_debug_stmts (void)
+{
+ basic_block bb;
+ bitmap_iterator bi;
+ unsigned int i;
+
+ if (!MAY_HAVE_DEBUG_STMTS)
+ return;
+
+ EXECUTE_IF_SET_IN_BITMAP (update_bbs, 0, i, bi)
+ {
+ gimple stmt;
+ gimple_stmt_iterator gsi;
+
+ bb = BASIC_BLOCK (i);
+ for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
+ {
+ stmt = gsi_stmt (gsi);
+ if (!is_gimple_debug (stmt))
+ continue;
+ update_debug_stmt (stmt);
+ }
+ }
+}
+
+/* Runs tail merge optimization. */
+
+unsigned int
+tail_merge_optimize (unsigned int todo)
+{
+ int nr_bbs_removed_total = 0;
+ int nr_bbs_removed;
+ bool loop_entered = false;
+ int iteration_nr = 0;
+ bool update_vops = !symbol_marked_for_renaming (gimple_vop (cfun));
+ int max_iterations = PARAM_VALUE (PARAM_MAX_TAIL_MERGE_ITERATIONS);
+
+ if (!flag_tree_tail_merge || max_iterations == 0)
+ return 0;
+
+ timevar_push (TV_TREE_TAIL_MERGE);
+
+ calculate_dominance_info (CDI_DOMINATORS);
+ init_worklist ();
+
+ while (!VEC_empty (same_succ, worklist))
+ {
+ if (!loop_entered)
+ {
+ loop_entered = true;
+ alloc_cluster_vectors ();
+ update_bbs = BITMAP_ALLOC (NULL);
+ }
+ else
+ reset_cluster_vectors ();
+
+ iteration_nr++;
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "worklist iteration #%d\n", iteration_nr);
+
+ find_clusters ();
+ gcc_assert (VEC_empty (same_succ, worklist));
+ if (VEC_empty (bb_cluster, all_clusters))
+ break;
+
+ nr_bbs_removed = apply_clusters (update_vops);
+ nr_bbs_removed_total += nr_bbs_removed;
+ if (nr_bbs_removed == 0)
+ break;
+
+ free_dominance_info (CDI_DOMINATORS);
+ purge_bbs ();
+
+ if (iteration_nr == max_iterations)
+ break;
+
+ calculate_dominance_info (CDI_DOMINATORS);
+ update_worklist ();
+ }
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "htab collision / search: %f\n",
+ htab_collisions (same_succ_htab));
+
+ if (nr_bbs_removed_total > 0)
+ {
+ calculate_dominance_info (CDI_DOMINATORS);
+ update_debug_stmts ();
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "Before TODOs.\n");
+ dump_function_to_file (current_function_decl, dump_file, dump_flags);
+ }
+
+ todo |= (TODO_verify_ssa | TODO_verify_stmts | TODO_verify_flow
+ | TODO_dump_func);
+ }
+
+ delete_worklist ();
+ if (loop_entered)
+ {
+ delete_cluster_vectors ();
+ BITMAP_FREE (update_bbs);
+ }
+
+ timevar_pop (TV_TREE_TAIL_MERGE);
+
+ return todo;
+}
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