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author | Ben Cheng <bccheng@google.com> | 2014-03-25 22:37:19 -0700 |
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committer | Ben Cheng <bccheng@google.com> | 2014-03-25 22:37:19 -0700 |
commit | 1bc5aee63eb72b341f506ad058502cd0361f0d10 (patch) | |
tree | c607e8252f3405424ff15bc2d00aa38dadbb2518 /gcc-4.9/gcc/tree-phinodes.c | |
parent | 283a0bf58fcf333c58a2a92c3ebbc41fb9eb1fdb (diff) | |
download | toolchain_gcc-1bc5aee63eb72b341f506ad058502cd0361f0d10.tar.gz toolchain_gcc-1bc5aee63eb72b341f506ad058502cd0361f0d10.tar.bz2 toolchain_gcc-1bc5aee63eb72b341f506ad058502cd0361f0d10.zip |
Initial checkin of GCC 4.9.0 from trunk (r208799).
Change-Id: I48a3c08bb98542aa215912a75f03c0890e497dba
Diffstat (limited to 'gcc-4.9/gcc/tree-phinodes.c')
-rw-r--r-- | gcc-4.9/gcc/tree-phinodes.c | 529 |
1 files changed, 529 insertions, 0 deletions
diff --git a/gcc-4.9/gcc/tree-phinodes.c b/gcc-4.9/gcc/tree-phinodes.c new file mode 100644 index 000000000..9dff6ad6a --- /dev/null +++ b/gcc-4.9/gcc/tree-phinodes.c @@ -0,0 +1,529 @@ +/* Generic routines for manipulating PHIs + Copyright (C) 2003-2014 Free Software Foundation, Inc. + +This file is part of GCC. + +GCC is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 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/>. */ + +#include "config.h" +#include "system.h" +#include "coretypes.h" +#include "tm.h" +#include "tree.h" +#include "basic-block.h" +#include "tree-ssa-alias.h" +#include "internal-fn.h" +#include "gimple-expr.h" +#include "is-a.h" +#include "gimple.h" +#include "gimple-iterator.h" +#include "gimple-ssa.h" +#include "tree-phinodes.h" +#include "ssa-iterators.h" +#include "stringpool.h" +#include "tree-ssanames.h" +#include "tree-ssa.h" +#include "diagnostic-core.h" + +/* Rewriting a function into SSA form can create a huge number of PHIs + many of which may be thrown away shortly after their creation if jumps + were threaded through PHI nodes. + + While our garbage collection mechanisms will handle this situation, it + is extremely wasteful to create nodes and throw them away, especially + when the nodes can be reused. + + For PR 8361, we can significantly reduce the number of nodes allocated + and thus the total amount of memory allocated by managing PHIs a + little. This additionally helps reduce the amount of work done by the + garbage collector. Similar results have been seen on a wider variety + of tests (such as the compiler itself). + + PHI nodes have different sizes, so we can't have a single list of all + the PHI nodes as it would be too expensive to walk down that list to + find a PHI of a suitable size. + + Instead we have an array of lists of free PHI nodes. The array is + indexed by the number of PHI alternatives that PHI node can hold. + Except for the last array member, which holds all remaining PHI + nodes. + + So to find a free PHI node, we compute its index into the free PHI + node array and see if there are any elements with an exact match. + If so, then we are done. Otherwise, we test the next larger size + up and continue until we are in the last array element. + + We do not actually walk members of the last array element. While it + might allow us to pick up a few reusable PHI nodes, it could potentially + be very expensive if the program has released a bunch of large PHI nodes, + but keeps asking for even larger PHI nodes. Experiments have shown that + walking the elements of the last array entry would result in finding less + than .1% additional reusable PHI nodes. + + Note that we can never have less than two PHI argument slots. Thus, + the -2 on all the calculations below. */ + +#define NUM_BUCKETS 10 +static GTY ((deletable (""))) vec<gimple, va_gc> *free_phinodes[NUM_BUCKETS - 2]; +static unsigned long free_phinode_count; + +static int ideal_phi_node_len (int); + +unsigned int phi_nodes_reused; +unsigned int phi_nodes_created; + +/* Dump some simple statistics regarding the re-use of PHI nodes. */ + +void +phinodes_print_statistics (void) +{ + fprintf (stderr, "PHI nodes allocated: %u\n", phi_nodes_created); + fprintf (stderr, "PHI nodes reused: %u\n", phi_nodes_reused); +} + +/* Allocate a PHI node with at least LEN arguments. If the free list + happens to contain a PHI node with LEN arguments or more, return + that one. */ + +static inline gimple_statement_phi * +allocate_phi_node (size_t len) +{ + gimple_statement_phi *phi; + size_t bucket = NUM_BUCKETS - 2; + size_t size = sizeof (struct gimple_statement_phi) + + (len - 1) * sizeof (struct phi_arg_d); + + if (free_phinode_count) + for (bucket = len - 2; bucket < NUM_BUCKETS - 2; bucket++) + if (free_phinodes[bucket]) + break; + + /* If our free list has an element, then use it. */ + if (bucket < NUM_BUCKETS - 2 + && gimple_phi_capacity ((*free_phinodes[bucket])[0]) >= len) + { + free_phinode_count--; + phi = as_a <gimple_statement_phi> (free_phinodes[bucket]->pop ()); + if (free_phinodes[bucket]->is_empty ()) + vec_free (free_phinodes[bucket]); + if (GATHER_STATISTICS) + phi_nodes_reused++; + } + else + { + phi = static_cast <gimple_statement_phi *> ( + ggc_internal_alloc_stat (size MEM_STAT_INFO)); + if (GATHER_STATISTICS) + { + enum gimple_alloc_kind kind = gimple_alloc_kind (GIMPLE_PHI); + phi_nodes_created++; + gimple_alloc_counts[(int) kind]++; + gimple_alloc_sizes[(int) kind] += size; + } + } + + return phi; +} + +/* Given LEN, the original number of requested PHI arguments, return + a new, "ideal" length for the PHI node. The "ideal" length rounds + the total size of the PHI node up to the next power of two bytes. + + Rounding up will not result in wasting any memory since the size request + will be rounded up by the GC system anyway. [ Note this is not entirely + true since the original length might have fit on one of the special + GC pages. ] By rounding up, we may avoid the need to reallocate the + PHI node later if we increase the number of arguments for the PHI. */ + +static int +ideal_phi_node_len (int len) +{ + size_t size, new_size; + int log2, new_len; + + /* We do not support allocations of less than two PHI argument slots. */ + if (len < 2) + len = 2; + + /* Compute the number of bytes of the original request. */ + size = sizeof (struct gimple_statement_phi) + + (len - 1) * sizeof (struct phi_arg_d); + + /* Round it up to the next power of two. */ + log2 = ceil_log2 (size); + new_size = 1 << log2; + + /* Now compute and return the number of PHI argument slots given an + ideal size allocation. */ + new_len = len + (new_size - size) / sizeof (struct phi_arg_d); + return new_len; +} + +/* Return a PHI node with LEN argument slots for variable VAR. */ + +static gimple +make_phi_node (tree var, int len) +{ + gimple_statement_phi *phi; + int capacity, i; + + capacity = ideal_phi_node_len (len); + + phi = allocate_phi_node (capacity); + + /* We need to clear the entire PHI node, including the argument + portion, because we represent a "missing PHI argument" by placing + NULL_TREE in PHI_ARG_DEF. */ + memset (phi, 0, (sizeof (struct gimple_statement_phi) + - sizeof (struct phi_arg_d) + + sizeof (struct phi_arg_d) * len)); + phi->code = GIMPLE_PHI; + gimple_init_singleton (phi); + phi->nargs = len; + phi->capacity = capacity; + if (!var) + ; + else if (TREE_CODE (var) == SSA_NAME) + gimple_phi_set_result (phi, var); + else + gimple_phi_set_result (phi, make_ssa_name (var, phi)); + + for (i = 0; i < capacity; i++) + { + use_operand_p imm; + + gimple_phi_arg_set_location (phi, i, UNKNOWN_LOCATION); + imm = gimple_phi_arg_imm_use_ptr (phi, i); + imm->use = gimple_phi_arg_def_ptr (phi, i); + imm->prev = NULL; + imm->next = NULL; + imm->loc.stmt = phi; + } + + return phi; +} + +/* We no longer need PHI, release it so that it may be reused. */ + +void +release_phi_node (gimple phi) +{ + size_t bucket; + size_t len = gimple_phi_capacity (phi); + size_t x; + + for (x = 0; x < gimple_phi_num_args (phi); x++) + { + use_operand_p imm; + imm = gimple_phi_arg_imm_use_ptr (phi, x); + delink_imm_use (imm); + } + + bucket = len > NUM_BUCKETS - 1 ? NUM_BUCKETS - 1 : len; + bucket -= 2; + vec_safe_push (free_phinodes[bucket], phi); + free_phinode_count++; +} + + +/* Resize an existing PHI node. The only way is up. Return the + possibly relocated phi. */ + +static gimple_statement_phi * +resize_phi_node (gimple_statement_phi *phi, size_t len) +{ + size_t old_size, i; + gimple_statement_phi *new_phi; + + gcc_assert (len > gimple_phi_capacity (phi)); + + /* The garbage collector will not look at the PHI node beyond the + first PHI_NUM_ARGS elements. Therefore, all we have to copy is a + portion of the PHI node currently in use. */ + old_size = sizeof (struct gimple_statement_phi) + + (gimple_phi_num_args (phi) - 1) * sizeof (struct phi_arg_d); + + new_phi = allocate_phi_node (len); + + memcpy (new_phi, phi, old_size); + + for (i = 0; i < gimple_phi_num_args (new_phi); i++) + { + use_operand_p imm, old_imm; + imm = gimple_phi_arg_imm_use_ptr (new_phi, i); + old_imm = gimple_phi_arg_imm_use_ptr (phi, i); + imm->use = gimple_phi_arg_def_ptr (new_phi, i); + relink_imm_use_stmt (imm, old_imm, new_phi); + } + + new_phi->capacity = len; + + for (i = gimple_phi_num_args (new_phi); i < len; i++) + { + use_operand_p imm; + + gimple_phi_arg_set_location (new_phi, i, UNKNOWN_LOCATION); + imm = gimple_phi_arg_imm_use_ptr (new_phi, i); + imm->use = gimple_phi_arg_def_ptr (new_phi, i); + imm->prev = NULL; + imm->next = NULL; + imm->loc.stmt = new_phi; + } + + return new_phi; +} + +/* Reserve PHI arguments for a new edge to basic block BB. */ + +void +reserve_phi_args_for_new_edge (basic_block bb) +{ + size_t len = EDGE_COUNT (bb->preds); + size_t cap = ideal_phi_node_len (len + 4); + gimple_stmt_iterator gsi; + + for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) + { + gimple_statement_phi *stmt = + as_a <gimple_statement_phi> (gsi_stmt (gsi)); + + if (len > gimple_phi_capacity (stmt)) + { + gimple_statement_phi *new_phi = resize_phi_node (stmt, cap); + + /* The result of the PHI is defined by this PHI node. */ + SSA_NAME_DEF_STMT (gimple_phi_result (new_phi)) = new_phi; + gsi_set_stmt (&gsi, new_phi); + + release_phi_node (stmt); + stmt = new_phi; + } + + /* We represent a "missing PHI argument" by placing NULL_TREE in + the corresponding slot. If PHI arguments were added + immediately after an edge is created, this zeroing would not + be necessary, but unfortunately this is not the case. For + example, the loop optimizer duplicates several basic blocks, + redirects edges, and then fixes up PHI arguments later in + batch. */ + SET_PHI_ARG_DEF (stmt, len - 1, NULL_TREE); + gimple_phi_arg_set_location (stmt, len - 1, UNKNOWN_LOCATION); + + stmt->nargs++; + } +} + +/* Adds PHI to BB. */ + +void +add_phi_node_to_bb (gimple phi, basic_block bb) +{ + gimple_seq seq = phi_nodes (bb); + /* Add the new PHI node to the list of PHI nodes for block BB. */ + if (seq == NULL) + set_phi_nodes (bb, gimple_seq_alloc_with_stmt (phi)); + else + { + gimple_seq_add_stmt (&seq, phi); + gcc_assert (seq == phi_nodes (bb)); + } + + /* Associate BB to the PHI node. */ + gimple_set_bb (phi, bb); + +} + +/* Create a new PHI node for variable VAR at basic block BB. */ + +gimple +create_phi_node (tree var, basic_block bb) +{ + gimple phi = make_phi_node (var, EDGE_COUNT (bb->preds)); + + add_phi_node_to_bb (phi, bb); + return phi; +} + + +/* Add a new argument to PHI node PHI. DEF is the incoming reaching + definition and E is the edge through which DEF reaches PHI. The new + argument is added at the end of the argument list. + If PHI has reached its maximum capacity, add a few slots. In this case, + PHI points to the reallocated phi node when we return. */ + +void +add_phi_arg (gimple phi, tree def, edge e, source_location locus) +{ + basic_block bb = e->dest; + + gcc_assert (bb == gimple_bb (phi)); + + /* We resize PHI nodes upon edge creation. We should always have + enough room at this point. */ + gcc_assert (gimple_phi_num_args (phi) <= gimple_phi_capacity (phi)); + + /* We resize PHI nodes upon edge creation. We should always have + enough room at this point. */ + gcc_assert (e->dest_idx < gimple_phi_num_args (phi)); + + /* Copy propagation needs to know what object occur in abnormal + PHI nodes. This is a convenient place to record such information. */ + if (e->flags & EDGE_ABNORMAL) + { + SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def) = 1; + SSA_NAME_OCCURS_IN_ABNORMAL_PHI (PHI_RESULT (phi)) = 1; + } + + SET_PHI_ARG_DEF (phi, e->dest_idx, def); + gimple_phi_arg_set_location (phi, e->dest_idx, locus); +} + + +/* Remove the Ith argument from PHI's argument list. This routine + implements removal by swapping the last alternative with the + alternative we want to delete and then shrinking the vector, which + is consistent with how we remove an edge from the edge vector. */ + +static void +remove_phi_arg_num (gimple_statement_phi *phi, int i) +{ + int num_elem = gimple_phi_num_args (phi); + + gcc_assert (i < num_elem); + + /* Delink the item which is being removed. */ + delink_imm_use (gimple_phi_arg_imm_use_ptr (phi, i)); + + /* If it is not the last element, move the last element + to the element we want to delete, resetting all the links. */ + if (i != num_elem - 1) + { + use_operand_p old_p, new_p; + old_p = gimple_phi_arg_imm_use_ptr (phi, num_elem - 1); + new_p = gimple_phi_arg_imm_use_ptr (phi, i); + /* Set use on new node, and link into last element's place. */ + *(new_p->use) = *(old_p->use); + relink_imm_use (new_p, old_p); + /* Move the location as well. */ + gimple_phi_arg_set_location (phi, i, + gimple_phi_arg_location (phi, num_elem - 1)); + } + + /* Shrink the vector and return. Note that we do not have to clear + PHI_ARG_DEF because the garbage collector will not look at those + elements beyond the first PHI_NUM_ARGS elements of the array. */ + phi->nargs--; +} + + +/* Remove all PHI arguments associated with edge E. */ + +void +remove_phi_args (edge e) +{ + gimple_stmt_iterator gsi; + + for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi); gsi_next (&gsi)) + remove_phi_arg_num (as_a <gimple_statement_phi> (gsi_stmt (gsi)), + e->dest_idx); +} + + +/* Remove the PHI node pointed-to by iterator GSI from basic block BB. After + removal, iterator GSI is updated to point to the next PHI node in the + sequence. If RELEASE_LHS_P is true, the LHS of this PHI node is released + into the free pool of SSA names. */ + +void +remove_phi_node (gimple_stmt_iterator *gsi, bool release_lhs_p) +{ + gimple phi = gsi_stmt (*gsi); + + if (release_lhs_p) + insert_debug_temps_for_defs (gsi); + + gsi_remove (gsi, false); + + /* If we are deleting the PHI node, then we should release the + SSA_NAME node so that it can be reused. */ + release_phi_node (phi); + if (release_lhs_p) + release_ssa_name (gimple_phi_result (phi)); +} + +/* Remove all the phi nodes from BB. */ + +void +remove_phi_nodes (basic_block bb) +{ + gimple_stmt_iterator gsi; + + for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); ) + remove_phi_node (&gsi, true); + + set_phi_nodes (bb, NULL); +} + +/* Given PHI, return its RHS if the PHI is a degenerate, otherwise return + NULL. */ + +tree +degenerate_phi_result (gimple phi) +{ + tree lhs = gimple_phi_result (phi); + tree val = NULL; + size_t i; + + /* Ignoring arguments which are the same as LHS, if all the remaining + arguments are the same, then the PHI is a degenerate and has the + value of that common argument. */ + for (i = 0; i < gimple_phi_num_args (phi); i++) + { + tree arg = gimple_phi_arg_def (phi, i); + + if (arg == lhs) + continue; + else if (!arg) + break; + else if (!val) + val = arg; + else if (arg == val) + continue; + /* We bring in some of operand_equal_p not only to speed things + up, but also to avoid crashing when dereferencing the type of + a released SSA name. */ + else if (TREE_CODE (val) != TREE_CODE (arg) + || TREE_CODE (val) == SSA_NAME + || !operand_equal_p (arg, val, 0)) + break; + } + return (i == gimple_phi_num_args (phi) ? val : NULL); +} + +/* Set PHI nodes of a basic block BB to SEQ. */ + +void +set_phi_nodes (basic_block bb, gimple_seq seq) +{ + gimple_stmt_iterator i; + + gcc_checking_assert (!(bb->flags & BB_RTL)); + bb->il.gimple.phi_nodes = seq; + if (seq) + for (i = gsi_start (seq); !gsi_end_p (i); gsi_next (&i)) + gimple_set_bb (gsi_stmt (i), bb); +} + +#include "gt-tree-phinodes.h" |