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Diffstat (limited to 'gcc-4.2.1-5666.3/gcc/tree-phinodes.c')
| -rw-r--r-- | gcc-4.2.1-5666.3/gcc/tree-phinodes.c | 488 |
1 files changed, 488 insertions, 0 deletions
diff --git a/gcc-4.2.1-5666.3/gcc/tree-phinodes.c b/gcc-4.2.1-5666.3/gcc/tree-phinodes.c new file mode 100644 index 000000000..98b011f89 --- /dev/null +++ b/gcc-4.2.1-5666.3/gcc/tree-phinodes.c @@ -0,0 +1,488 @@ +/* Generic routines for manipulating PHIs + Copyright (C) 2003, 2005 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 2, 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 COPYING. If not, write to +the Free Software Foundation, 51 Franklin Street, Fifth Floor, +Boston, MA 02110-1301, USA. */ + +#include "config.h" +#include "system.h" +#include "coretypes.h" +#include "tm.h" +#include "tree.h" +#include "rtl.h" +#include "varray.h" +#include "ggc.h" +#include "basic-block.h" +#include "tree-flow.h" +#include "toplev.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). + + Right now we maintain our free list on a per-function basis. It may + or may not make sense to maintain the free list for the duration of + a compilation unit. + + We could also use a zone allocator for these objects since they have + a very well defined lifetime. If someone wants to experiment with that + this is the place to try it. + + 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 (""))) tree free_phinodes[NUM_BUCKETS - 2]; +static unsigned long free_phinode_count; + +static int ideal_phi_node_len (int); +static void resize_phi_node (tree *, int); + +#ifdef GATHER_STATISTICS +unsigned int phi_nodes_reused; +unsigned int phi_nodes_created; +#endif + +/* Initialize management of PHIs. */ + +void +init_phinodes (void) +{ + int i; + + for (i = 0; i < NUM_BUCKETS - 2; i++) + free_phinodes[i] = NULL; + free_phinode_count = 0; +} + +/* Finalize management of PHIs. */ + +void +fini_phinodes (void) +{ + int i; + + for (i = 0; i < NUM_BUCKETS - 2; i++) + free_phinodes[i] = NULL; + free_phinode_count = 0; +} + +/* Dump some simple statistics regarding the re-use of PHI nodes. */ + +#ifdef GATHER_STATISTICS +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); +} +#endif + +/* 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 tree +allocate_phi_node (int len) +{ + tree phi; + int bucket = NUM_BUCKETS - 2; + int size = (sizeof (struct tree_phi_node) + + (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 + && PHI_ARG_CAPACITY (free_phinodes[bucket]) >= len) + { + free_phinode_count--; + phi = free_phinodes[bucket]; + free_phinodes[bucket] = PHI_CHAIN (free_phinodes[bucket]); +#ifdef GATHER_STATISTICS + phi_nodes_reused++; +#endif + } + else + { + phi = ggc_alloc (size); +#ifdef GATHER_STATISTICS + phi_nodes_created++; + tree_node_counts[(int) phi_kind]++; + tree_node_sizes[(int) phi_kind] += size; +#endif + } + + 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 tree_phi_node) + (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 tree +make_phi_node (tree var, int len) +{ + tree 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 tree_phi_node) - sizeof (struct phi_arg_d) + + sizeof (struct phi_arg_d) * len)); + TREE_SET_CODE (phi, PHI_NODE); + PHI_NUM_ARGS (phi) = len; + PHI_ARG_CAPACITY (phi) = capacity; + TREE_TYPE (phi) = TREE_TYPE (var); + if (TREE_CODE (var) == SSA_NAME) + SET_PHI_RESULT (phi, var); + else + SET_PHI_RESULT (phi, make_ssa_name (var, phi)); + + for (i = 0; i < capacity; i++) + { + use_operand_p imm; + imm = &(PHI_ARG_IMM_USE_NODE (phi, i)); + imm->use = &(PHI_ARG_DEF_TREE (phi, i)); + imm->prev = NULL; + imm->next = NULL; + imm->stmt = phi; + } + return phi; +} + +/* We no longer need PHI, release it so that it may be reused. */ + +void +release_phi_node (tree phi) +{ + int bucket; + int len = PHI_ARG_CAPACITY (phi); + int x; + + for (x = 0; x < PHI_NUM_ARGS (phi); x++) + { + use_operand_p imm; + imm = &(PHI_ARG_IMM_USE_NODE (phi, x)); + delink_imm_use (imm); + } + + bucket = len > NUM_BUCKETS - 1 ? NUM_BUCKETS - 1 : len; + bucket -= 2; + PHI_CHAIN (phi) = free_phinodes[bucket]; + free_phinodes[bucket] = phi; + free_phinode_count++; +} + +/* Resize an existing PHI node. The only way is up. Return the + possibly relocated phi. */ + +static void +resize_phi_node (tree *phi, int len) +{ + int old_size, i; + tree new_phi; + + gcc_assert (len > PHI_ARG_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 tree_phi_node) + + (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 < PHI_NUM_ARGS (new_phi); i++) + { + use_operand_p imm, old_imm; + imm = &(PHI_ARG_IMM_USE_NODE (new_phi, i)); + old_imm = &(PHI_ARG_IMM_USE_NODE (*phi, i)); + imm->use = &(PHI_ARG_DEF_TREE (new_phi, i)); + relink_imm_use_stmt (imm, old_imm, new_phi); + } + + PHI_ARG_CAPACITY (new_phi) = len; + + for (i = PHI_NUM_ARGS (new_phi); i < len; i++) + { + use_operand_p imm; + imm = &(PHI_ARG_IMM_USE_NODE (new_phi, i)); + imm->use = &(PHI_ARG_DEF_TREE (new_phi, i)); + imm->prev = NULL; + imm->next = NULL; + imm->stmt = new_phi; + } + + + *phi = new_phi; +} + +/* Reserve PHI arguments for a new edge to basic block BB. */ + +void +reserve_phi_args_for_new_edge (basic_block bb) +{ + tree *loc; + int len = EDGE_COUNT (bb->preds); + int cap = ideal_phi_node_len (len + 4); + + for (loc = &(bb->phi_nodes); + *loc; + loc = &PHI_CHAIN (*loc)) + { + if (len > PHI_ARG_CAPACITY (*loc)) + { + tree old_phi = *loc; + + resize_phi_node (loc, cap); + + /* The result of the phi is defined by this phi node. */ + SSA_NAME_DEF_STMT (PHI_RESULT (*loc)) = *loc; + + release_phi_node (old_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 (*loc, len - 1, NULL_TREE); + + PHI_NUM_ARGS (*loc)++; + } +} + +/* Create a new PHI node for variable VAR at basic block BB. */ + +tree +create_phi_node (tree var, basic_block bb) +{ + tree phi; + + phi = make_phi_node (var, EDGE_COUNT (bb->preds)); + + /* Add the new PHI node to the list of PHI nodes for block BB. */ + PHI_CHAIN (phi) = phi_nodes (bb); + bb->phi_nodes = phi; + + /* Associate BB to the PHI node. */ + set_bb_for_stmt (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 (tree phi, tree def, edge e) +{ + basic_block bb = e->dest; + + gcc_assert (bb == bb_for_stmt (phi)); + + /* We resize PHI nodes upon edge creation. We should always have + enough room at this point. */ + gcc_assert (PHI_NUM_ARGS (phi) <= PHI_ARG_CAPACITY (phi)); + + /* We resize PHI nodes upon edge creation. We should always have + enough room at this point. */ + gcc_assert (e->dest_idx < (unsigned int) 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); +} + +/* 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 (tree phi, int i) +{ + int num_elem = PHI_NUM_ARGS (phi); + + gcc_assert (i < num_elem); + + + /* Delink the item which is being removed. */ + delink_imm_use (&(PHI_ARG_IMM_USE_NODE (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 = &PHI_ARG_IMM_USE_NODE (phi, num_elem - 1); + new_p = &PHI_ARG_IMM_USE_NODE (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); + } + + /* 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_NUM_ARGS (phi)--; +} + +/* Remove all PHI arguments associated with edge E. */ + +void +remove_phi_args (edge e) +{ + tree phi; + + for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi)) + remove_phi_arg_num (phi, e->dest_idx); +} + +/* Remove PHI node PHI from basic block BB. If PREV is non-NULL, it is + used as the node immediately before PHI in the linked list. */ + +void +remove_phi_node (tree phi, tree prev) +{ + tree *loc; + + if (prev) + { + loc = &PHI_CHAIN (prev); + } + else + { + for (loc = &(bb_for_stmt (phi)->phi_nodes); + *loc != phi; + loc = &PHI_CHAIN (*loc)) + ; + } + + /* Remove PHI from the chain. */ + *loc = PHI_CHAIN (phi); + + /* 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); + release_ssa_name (PHI_RESULT (phi)); +} + + +/* Reverse the order of PHI nodes in the chain PHI. + Return the new head of the chain (old last PHI node). */ + +tree +phi_reverse (tree phi) +{ + tree prev = NULL_TREE, next; + for (; phi; phi = next) + { + next = PHI_CHAIN (phi); + PHI_CHAIN (phi) = prev; + prev = phi; + } + return prev; +} + +#include "gt-tree-phinodes.h" |