/* SSA-PRE for trees. Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc. Contributed by Daniel Berlin and Steven Bosscher 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, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #include "config.h" #include "system.h" #include "coretypes.h" #include "tm.h" #include "errors.h" #include "ggc.h" #include "tree.h" /* These RTL headers are needed for basic-block.h. */ #include "rtl.h" #include "tm_p.h" #include "hard-reg-set.h" #include "basic-block.h" #include "diagnostic.h" #include "tree-inline.h" #include "tree-flow.h" #include "tree-gimple.h" #include "tree-dump.h" #include "timevar.h" #include "fibheap.h" #include "hashtab.h" #include "tree-iterator.h" #include "real.h" #include "alloc-pool.h" #include "tree-pass.h" #include "flags.h" #include "splay-tree.h" #include "bitmap.h" #include "langhooks.h" /* TODO: 1. Implement load value numbering. 2. Speed up insert_aux so that we can use it all the time. It spends most of it's time in quadratic value replacement. 3. Avail sets can be shared by making an avail_find_leader that walks up the dominator tree and looks in those avail sets. This might affect code optimality, it's unclear right now. 4. Load motion can be performed by value numbering the loads the same as we do other expressions. This requires iterative hashing the vuses into the values. Right now we simply assign a new value every time we see a statement with a vuse. 5. Strength reduction can be performed by anticipating expressions we can repair later on. */ /* For ease of terminology, "expression node" in the below refers to every expression node but MODIFY_EXPR, because MODIFY_EXPR's represent the actual statement containing the expressions we care about, and we cache the value number by putting it in the expression. */ /* Basic algorithm First we walk the statements to generate the AVAIL sets, the EXP_GEN sets, and the tmp_gen sets. AVAIL is a forward dataflow problem. EXP_GEN sets represent the generation of values/expressions by a given block. We use them when computing the ANTIC sets. The AVAIL sets consist of SSA_NAME's that represent values, so we know what values are available in what blocks. In SSA, values are never killed, so we don't need a kill set, or a fixpoint iteration, in order to calculate the AVAIL sets. In traditional parlance, AVAIL sets tell us the downsafety of the expressions/values. Next, we generate the ANTIC sets. ANTIC is a backwards dataflow problem. These sets represent the anticipatable expressions. An expression is anticipatable in a given block if it could be generated in that block. This means that if we had to perform an insertion in that block, of the value of that expression, we could. Calculating the ANTIC sets requires phi translation of expressions, because the flow goes backwards through phis. We must iterate to a fixpoint of the ANTIC sets, because we have a kill set. Even in SSA form, values are not live over the entire function, only from their definition point onwards. So we have to remove values from the ANTIC set once we go past the definition point of the leaders that make them up. compute_antic/compute_antic_aux performs this computation. Third, we perform insertions to make partially redundant expressions fully redundant. An expression is partially redundant (excluding partial anticipation) if: 1. It is AVAIL in some, but not all, of the predecessors of a given block. 2. It is ANTIC in all the predecessors. In order to make it fully redundant, we insert the expression into the predecessors where it is not available, but is ANTIC. insert/insert_aux performs this insertion. Fourth, we eliminate fully redundant expressions. This is a simple statement walk that replaces redundant calculations with the now available values. */ /* Representations of value numbers: Value numbers are represented using the "value handle" approach. This means that each SSA_NAME (and for other reasons to be disclosed in a moment, expression nodes and constant nodes) has a value handle that can be retrieved through get_value_handle. This value handle, *is* the value number of the SSA_NAME. You can pointer compare the value handles for equivalence purposes. For debugging reasons, the value handle is internally more than just a number, it is a VAR_DECL named "value.x", where x is a unique number for each value number in use. This allows expressions with SSA_NAMES replaced by value handles to still be pretty printed in a sane way. They simply print as "value.3 * value.5", etc. Expression nodes have value handles associated with them as a cache. Otherwise, we'd have to look them up again in the hash table This makes significant difference (factor of two or more) on some test cases. They can be thrown away after the Constants have value handles associated with them so that they aren't special cased everywhere, and for consistency sake. This may be changed depending on memory usage vs code maintenance tradeoff. */ /* Representation of expressions on value numbers: In some portions of this code, you will notice we allocate "fake" analogues to the expression we are value numbering, and replace the operands with the values of the expression. Since we work on values, and not just names, we canonicalize expressions to value expressions for use in the ANTIC sets, the EXP_GEN set, etc. This is theoretically unnecessary, it just saves a bunch of repeated get_value_handle and find_leader calls in the remainder of the code, trading off temporary memory usage for speed. The tree nodes aren't actually creating more garbage, since they are allocated in a special pools which are thrown away at the end of this pass. All of this also means that if you print the EXP_GEN or ANTIC sets, you will see "value.5 + value.7" in the set, instead of "a_55 + b_66" or something. The only thing that actually cares about seeing the value leaders is phi translation, and it needs to be able to find the leader for a value in an arbitrary block, so this "value expression" form is perfect for it (otherwise you'd do get_value_handle->find_leader->translate->get_value_handle->find_leader).*/ /* Representation of sets: Sets are represented as doubly linked lists kept in topological order, with an optional supporting bitmap of values present in the set. The sets represent values, and the elements can be constants, values, or expressions. The elements can appear in different sets, but each element can only appear once in each set. Since each node in the set represents a value, we also want to be able to map expression, set pairs to something that tells us whether the value is present is a set. We use a per-set bitmap for that. The value handles also point to a linked list of the expressions they represent via a tree annotation. This is mainly useful only for debugging, since we don't do identity lookups. */ /* A value set element. Basically a single linked list of expressions/constants/values. */ typedef struct value_set_node { tree expr; struct value_set_node *next; } *value_set_node_t; /* A value set, which is the head of the linked list, and we also keep the tail because we have to append for the topolofical sort. */ typedef struct value_set { value_set_node_t head; value_set_node_t tail; size_t length; bool indexed; bitmap values; } *value_set_t; /* All of the following sets, except for TMP_GEN, are indexed. TMP_GEN is only ever iterated over, we never check what values exist in it. */ typedef struct bb_value_sets { value_set_t exp_gen; value_set_t phi_gen; value_set_t tmp_gen; value_set_t avail_out; value_set_t antic_in; value_set_t new_sets; } *bb_value_sets_t; #define EXP_GEN(BB) ((bb_value_sets_t) ((BB)->aux))->exp_gen #define PHI_GEN(BB) ((bb_value_sets_t) ((BB)->aux))->phi_gen #define TMP_GEN(BB) ((bb_value_sets_t) ((BB)->aux))->tmp_gen #define AVAIL_OUT(BB) ((bb_value_sets_t) ((BB)->aux))->avail_out #define ANTIC_IN(BB) ((bb_value_sets_t) ((BB)->aux))->antic_in #define NEW_SETS(BB) ((bb_value_sets_t) ((BB)->aux))->new_sets static struct { int eliminations; int insertions; int phis; } pre_stats; static tree find_leader (value_set_t, tree); static void value_insert_into_set (value_set_t, tree); static void insert_into_set (value_set_t, tree); static void add_to_value (tree, tree); static value_set_t set_new (bool); static bool is_undefined_value (tree); /* We can add and remove elements and entries to and from sets and hash tables, so we use alloc pools for them. */ static alloc_pool value_set_pool; static alloc_pool value_set_node_pool; static alloc_pool binary_node_pool; static alloc_pool unary_node_pool; /* The value table that maps expressions to values. */ static htab_t value_table; /* The phi_translate_table caches phi translations for a given expression and predecessor. */ static htab_t phi_translate_table; /* Map expressions to values. These are simple pairs of expressions and the values they represent. To find the value represented by an expression, we use a hash table where the elements are {e,v} pairs, and the expression is the key. */ typedef struct val_expr_pair_d { tree v, e; hashval_t hashcode; } *val_expr_pair_t; /* Hash a {v,e} pair. We really only hash the expression. */ static hashval_t val_expr_pair_hash (const void *p) { const val_expr_pair_t ve = (val_expr_pair_t) p; return ve->hashcode; } /* Are {e2,v2} and {e1,v1} the same? Again, only the expression matters. */ static int val_expr_pair_expr_eq (const void *p1, const void *p2) { const val_expr_pair_t ve1 = (val_expr_pair_t) p1; const val_expr_pair_t ve2 = (val_expr_pair_t) p2; tree e1 = ve1->e; tree e2 = ve2->e; tree te1; tree te2; if (e1 == e2) return true; te1 = TREE_TYPE (e1); te2 = TREE_TYPE (e2); if (TREE_CODE (e1) == TREE_CODE (e2) && (te1 == te2 || lang_hooks.types_compatible_p (te1, te2)) && operand_equal_p (e1, e2, 0)) return true; return false; } /* Get the value handle of EXPR. This is the only correct way to get the value handle for a "thing". */ tree get_value_handle (tree expr) { /* We should never see these. */ if (DECL_P (expr)) abort (); else if (TREE_CODE (expr) == SSA_NAME) { return SSA_NAME_VALUE (expr); } else if (TREE_CODE_CLASS (TREE_CODE (expr)) == 'c') { cst_ann_t ann = cst_ann (expr); if (ann) return ann->common.value_handle; return NULL; } else if (EXPR_P (expr)) { expr_ann_t ann = expr_ann (expr); if (ann) return ann->common.value_handle; return NULL; } abort (); } /* Set the value handle for E to V */ void set_value_handle (tree e, tree v) { if (DECL_P (e)) abort (); else if (TREE_CODE (e) == SSA_NAME) SSA_NAME_VALUE (e) = v; else if (TREE_CODE_CLASS (TREE_CODE (e)) == 'c') get_cst_ann (e)->common.value_handle = v; else if (EXPR_P (e)) get_expr_ann (e)->common.value_handle = v; } /* A three tuple {e, pred, v} used to cache phi translations in the phi_translate_table. */ typedef struct expr_pred_trans_d { tree e; basic_block pred; tree v; hashval_t hashcode; } *expr_pred_trans_t; /* Return the hash value for a phi translation table entry. */ static hashval_t expr_pred_trans_hash (const void *p) { const expr_pred_trans_t ve = (expr_pred_trans_t) p; return ve->hashcode; } /* Return true if two phi translation table entries are the same. */ static int expr_pred_trans_eq (const void *p1, const void *p2) { const expr_pred_trans_t ve1 = (expr_pred_trans_t) p1; const expr_pred_trans_t ve2 = (expr_pred_trans_t) p2; tree e1 = ve1->e; tree e2 = ve2->e; basic_block b1 = ve1->pred; basic_block b2 = ve2->pred; tree te1; tree te2; if (b1 != b2) return false; if (e1 == e2) return true; te1 = TREE_TYPE (e1); te2 = TREE_TYPE (e2); if (TREE_CODE (e1) == TREE_CODE (e2) && (te1 == te2 || lang_hooks.types_compatible_p (te1, te2)) && operand_equal_p (e1, e2, 0)) return true; return false; } /* Search in the phi translation table for the translation of E in PRED. Return the translated value, if found, NULL otherwise. */ static inline tree phi_trans_lookup (tree e, basic_block pred) { void **slot; struct expr_pred_trans_d ugly; ugly.e = e; ugly.pred = pred; ugly.hashcode = iterative_hash_expr (e, (unsigned long) pred); slot = htab_find_slot_with_hash (phi_translate_table, &ugly, ugly.hashcode, NO_INSERT); if (!slot) return NULL; else return ((expr_pred_trans_t) *slot)->v; } /* Add the tuple mapping {e, pred}->v to the phi translation table. */ static inline void phi_trans_add (tree e, tree v, basic_block pred) { void **slot; expr_pred_trans_t new_pair = xmalloc (sizeof (*new_pair)); new_pair->e = e; new_pair->pred = pred; new_pair->v = v; new_pair->hashcode = iterative_hash_expr (e, (unsigned long) pred); slot = htab_find_slot_with_hash (phi_translate_table, new_pair, new_pair->hashcode, INSERT); if (*slot) free (*slot); *slot = (void *) new_pair; } /* Search in TABLE for an existing instance of expression E, and return its value, or NULL if none has been set. */ static inline tree lookup (htab_t table, tree e) { void **slot; struct val_expr_pair_d ugly = {NULL, NULL, 0}; ugly.e = e; ugly.hashcode = iterative_hash_expr (e,0); slot = htab_find_slot_with_hash (table, &ugly, ugly.hashcode, NO_INSERT); if (!slot) return NULL_TREE; else return ((val_expr_pair_t) *slot)->v; } /* Add E to the expression set of V. */ static inline void add_to_value (tree v, tree e) { #if DEBUG_VALUE_EXPRESSIONS var_ann_t va = var_ann (v); #endif /* For values representing numerical constants, we mark TREE_CONSTANT as true and set the tree chain to the actual constant. This is because unlike values involving expressions, which are only available to use where the expressions are live, a constant can be remade anywhere, and thus, is available everywhere. */ if (TREE_CODE_CLASS (TREE_CODE (e)) == 'c') { TREE_CONSTANT (v) = true; TREE_CHAIN (v) = e; } else if (is_gimple_min_invariant (e)) { TREE_CONSTANT (v) = true; TREE_CHAIN (v) = e; } #if DEBUG_VALUE_EXPRESSIONS if (va->expr_set == NULL) va->expr_set = set_new (false); insert_into_set (va->expr_set, e); #endif } /* Insert E into TABLE with value V, and add E to the value set for V. */ static inline void add (htab_t table, tree e, tree v) { void **slot; val_expr_pair_t new_pair = xmalloc (sizeof (struct val_expr_pair_d)); new_pair->e = e; new_pair->v = v; new_pair->hashcode = iterative_hash_expr (e, 0); slot = htab_find_slot_with_hash (table, new_pair, new_pair->hashcode, INSERT); if (*slot) free (*slot); *slot = (void *) new_pair; set_value_handle (e, v); add_to_value (v, e); } static int pre_uid; /* Create a new value handle for EXPR. */ static tree create_new_value (tree expr) { tree a = create_tmp_var_raw (TREE_TYPE (expr), "value"); create_var_ann (a); var_ann (a)->uid = pre_uid++; if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Created value "); print_generic_expr (dump_file, a, dump_flags); fprintf (dump_file, " for "); print_generic_expr (dump_file, expr, dump_flags); fprintf (dump_file, "\n"); } return a; } /* Like lookup, but adds V as the value for E if E does not have a value. */ static inline tree lookup_or_add (htab_t table, tree e) { tree x = lookup (table, e); if (x == NULL_TREE) { tree v; v = create_new_value (e); add (table, e, v); x = v; } set_value_handle (e, x); return x; } /* Search in the bitmap for SET to see if E exists. */ static inline bool value_exists_in_set_bitmap (value_set_t set, tree e) { if (TREE_CODE (e) != VAR_DECL) abort (); if (!set->values) return false; return bitmap_bit_p (set->values, get_var_ann (e)->uid); } /* Remove E from the bitmap for SET. */ static void value_remove_from_set_bitmap (value_set_t set, tree e) { if (TREE_CODE (e) != VAR_DECL) abort (); #ifdef ENABLE_CHECKING if (!set->indexed) abort (); #endif if (!set->values) return; bitmap_clear_bit (set->values, get_var_ann (e)->uid); } /* Insert the value number E into the bitmap of values existing in SET. */ static inline void value_insert_into_set_bitmap (value_set_t set, tree e) { if (TREE_CODE (e) != VAR_DECL) abort (); #ifdef ENABLE_CHECKING if (!set->indexed) abort (); #endif if (set->values == NULL) { set->values = BITMAP_GGC_ALLOC (); bitmap_clear (set->values); } bitmap_set_bit (set->values, get_var_ann (e)->uid); } /* Create a new set. */ static value_set_t set_new (bool indexed) { value_set_t ret; ret = pool_alloc (value_set_pool); ret->head = ret->tail = NULL; ret->length = 0; ret->indexed = indexed; ret->values = NULL; return ret; } /* Insert EXPR into SET. */ static void insert_into_set (value_set_t set, tree expr) { value_set_node_t newnode = pool_alloc (value_set_node_pool); tree val = get_value_handle (expr); if (DECL_P (expr)) abort (); if (val == NULL) abort (); /* For indexed sets, insert the value into the set value bitmap. For all sets, add it to the linked list and increment the list length. */ if (set->indexed) value_insert_into_set_bitmap (set, val); newnode->next = NULL; newnode->expr = expr; set->length ++; if (set->head == NULL) { set->head = set->tail = newnode; } else { set->tail->next = newnode; set->tail = newnode; } } /* Copy the set ORIG to the set DEST. */ static void set_copy (value_set_t dest, value_set_t orig) { value_set_node_t node; if (!orig || !orig->head) return; for (node = orig->head; node; node = node->next) { insert_into_set (dest, node->expr); } } /* Remove EXPR from SET. */ static void set_remove (value_set_t set, tree expr) { value_set_node_t node, prev; /* Remove the value of EXPR from the bitmap, decrement the set length, and remove it from the actual double linked list. */ value_remove_from_set_bitmap (set, get_value_handle (expr)); set->length--; prev = NULL; for (node = set->head; node != NULL; prev = node, node = node->next) { if (node->expr == expr) { if (prev == NULL) set->head = node->next; else prev->next= node->next; if (node == set->tail) set->tail = prev; pool_free (value_set_node_pool, node); return; } } } /* Return true if SET contains the value VAL. */ static bool set_contains_value (value_set_t set, tree val) { /* This is only referring to the flag above that we set on values referring to numerical constants, because we know that we are dealing with one of the value handles we created. */ if (TREE_CONSTANT (val)) return true; if (set->length == 0) return false; return value_exists_in_set_bitmap (set, val); } /* Replace the leader for the value LOOKFOR in SET with EXPR. */ static void set_replace_value (value_set_t set, tree lookfor, tree expr) { value_set_node_t node = set->head; /* The lookup is probably more expensive than walking the linked list when we have only a small number of nodes. */ if (!set_contains_value (set, lookfor)) return; for (node = set->head; node; node = node->next) { if (get_value_handle (node->expr) == lookfor) { node->expr = expr; return; } } } /* Return true if the set contains expression (not value) EXPR. */ static bool set_contains (value_set_t set, tree expr) { value_set_node_t node; for (node = set->head; node; node = node->next) { if (operand_equal_p (node->expr, expr, 0)) return true; } return false; } /* Subtract set B from set A, and return the new set. */ static value_set_t set_subtract (value_set_t a, value_set_t b, bool indexed) { value_set_t ret = set_new (indexed); value_set_node_t node; for (node = a->head; node; node = node->next) { if (!set_contains (b, node->expr)) insert_into_set (ret, node->expr); } return ret; } /* Return true if two sets are equal. */ static bool set_equal (value_set_t a, value_set_t b) { value_set_node_t node; if (a->length != b->length) return false; for (node = a->head; node; node = node->next) { if (!set_contains_value (b, get_value_handle (node->expr))) return false; } return true; } /* Replace the value for EXPR in SET with EXPR. */ static void value_replace_in_set (value_set_t set, tree expr) { tree val = get_value_handle (expr); if (set->length == 0) return; set_replace_value (set, val, expr); } /* Insert the value for EXPR into SET, if it doesn't exist already. */ static void value_insert_into_set (value_set_t set, tree expr) { tree val = get_value_handle (expr); /* Constant values exist everywhere. */ if (TREE_CONSTANT (val)) return; if (!set_contains_value (set, val)) insert_into_set (set, expr); } /* Print out the value_set SET to OUTFILE. */ static void print_value_set (FILE *outfile, value_set_t set, const char *setname, int blockindex) { value_set_node_t node; fprintf (outfile, "%s[%d] := { ", setname, blockindex); if (set) { for (node = set->head; node; node = node->next) { print_generic_expr (outfile, node->expr, 0); if (node->next) fprintf (outfile, ", "); } } fprintf (outfile, " }\n"); } /* Print out the expressions that have VAL to OUTFILE. */ void print_value_expressions (FILE *outfile, tree val) { var_ann_t va = var_ann (val); if (va && va->expr_set) print_value_set (outfile, va->expr_set, IDENTIFIER_POINTER (DECL_NAME (val)), 0); } void debug_value_expressions (tree val) { print_value_expressions (stderr, val); } void debug_value_set (value_set_t, const char *, int); void debug_value_set (value_set_t set, const char *setname, int blockindex) { print_value_set (stderr, set, setname, blockindex); } /* Translate EXPR using phis in PHIBLOCK, so that it has the values of the phis in PRED. Return NULL if we can't find a leader for each part of the translated expression. */ static tree phi_translate (tree expr, value_set_t set, basic_block pred, basic_block phiblock) { tree phitrans = NULL; tree oldexpr = expr; if (expr == NULL) return NULL; /* Phi translations of a given expression don't change, */ phitrans = phi_trans_lookup (expr, pred); if (phitrans) return phitrans; switch (TREE_CODE_CLASS (TREE_CODE (expr))) { case '2': { tree oldop1 = TREE_OPERAND (expr, 0); tree oldop2 = TREE_OPERAND (expr, 1); tree newop1; tree newop2; tree newexpr; newop1 = phi_translate (find_leader (set, oldop1), set, pred, phiblock); if (newop1 == NULL) return NULL; newop2 = phi_translate (find_leader (set, oldop2), set, pred, phiblock); if (newop2 == NULL) return NULL; if (newop1 != oldop1 || newop2 != oldop2) { newexpr = pool_alloc (binary_node_pool); memcpy (newexpr, expr, tree_size (expr)); create_expr_ann (newexpr); TREE_OPERAND (newexpr, 0) = newop1 == oldop1 ? oldop1 : get_value_handle (newop1); TREE_OPERAND (newexpr, 1) = newop2 == oldop2 ? oldop2 : get_value_handle (newop2); lookup_or_add (value_table, newexpr); expr = newexpr; phi_trans_add (oldexpr, newexpr, pred); } } break; case '1': { tree oldop1 = TREE_OPERAND (expr, 0); tree newop1; tree newexpr; newop1 = phi_translate (find_leader (set, oldop1), set, pred, phiblock); if (newop1 == NULL) return NULL; if (newop1 != oldop1) { newexpr = pool_alloc (unary_node_pool); memcpy (newexpr, expr, tree_size (expr)); create_expr_ann (newexpr); TREE_OPERAND (newexpr, 0) = get_value_handle (newop1); lookup_or_add (value_table, newexpr); expr = newexpr; phi_trans_add (oldexpr, newexpr, pred); } } break; case 'd': abort (); case 'x': { tree phi = NULL; int i; if (TREE_CODE (expr) != SSA_NAME) abort (); if (TREE_CODE (SSA_NAME_DEF_STMT (expr)) == PHI_NODE) phi = SSA_NAME_DEF_STMT (expr); else return expr; for (i = 0; i < PHI_NUM_ARGS (phi); i++) if (PHI_ARG_EDGE (phi, i)->src == pred) { tree val; if (is_undefined_value (PHI_ARG_DEF (phi, i))) return NULL; val = lookup_or_add (value_table, PHI_ARG_DEF (phi, i)); return PHI_ARG_DEF (phi, i); } } break; } return expr; } static void phi_translate_set (value_set_t dest, value_set_t set, basic_block pred, basic_block phiblock) { value_set_node_t node; for (node = set->head; node; node = node->next) { tree translated; translated = phi_translate (node->expr, set, pred, phiblock); phi_trans_add (node->expr, translated, pred); if (translated != NULL) value_insert_into_set (dest, translated); } } /* Find the leader for a value (IE the name representing that value) in a given set, and return it. Return NULL if no leader is found. */ static tree find_leader (value_set_t set, tree val) { value_set_node_t node; if (val == NULL) return NULL; if (TREE_CONSTANT (val)) return TREE_CHAIN (val); if (set->length == 0) return NULL; if (value_exists_in_set_bitmap (set, val)) { for (node = set->head; node; node = node->next) { if (get_value_handle (node->expr) == val) return node->expr; } } return NULL; } /* Determine if the expression EXPR is valid in SET. This means that we have a leader for each part of the expression (if it consists of values), or the expression is an SSA_NAME. NB: We never should run into a case where we have SSA_NAME + SSA_NAME or SSA_NAME + value. The sets valid_in_set is called on, the ANTIC sets, will only ever have SSA_NAME's or binary value expression (IE VALUE1 + VALUE2) */ static bool valid_in_set (value_set_t set, tree expr) { switch (TREE_CODE_CLASS (TREE_CODE (expr))) { case '2': { tree op1 = TREE_OPERAND (expr, 0); tree op2 = TREE_OPERAND (expr, 1); return set_contains_value (set, op1) && set_contains_value (set, op2); } break; case '1': { tree op1 = TREE_OPERAND (expr, 0); return set_contains_value (set, op1); } break; case 'x': { if (TREE_CODE (expr) == SSA_NAME) return true; abort (); } case 'c': abort (); } return false; } /* Clean the set of expressions that are no longer valid in the specified set. This means expressions that are made up of values we have no leaders for in the current set, etc. */ static void clean (value_set_t set) { value_set_node_t node; value_set_node_t next; node = set->head; while (node) { next = node->next; if (!valid_in_set (set, node->expr)) set_remove (set, node->expr); node = next; } } /* Compute the ANTIC set for BLOCK. ANTIC_OUT[BLOCK] = intersection of ANTIC_IN[b] for all succ(BLOCK), if succs(BLOCK) > 1 ANTIC_OUT[BLOCK] = phi_translate (ANTIC_IN[succ(BLOCK)]) if succs(BLOCK) == 1 ANTIC_IN[BLOCK] = clean(ANTIC_OUT[BLOCK] U EXP_GEN[BLOCK] - TMP_GEN[BLOCK]) Iterate until fixpointed. XXX: It would be nice to either write a set_clear, and use it for antic_out, or to mark the antic_out set as deleted at the end of this routine, so that the pool can hand the same memory back out again for the next antic_out. */ static bool compute_antic_aux (basic_block block) { basic_block son; edge e; bool changed = false; value_set_t S, old, ANTIC_OUT; value_set_node_t node; ANTIC_OUT = S = NULL; /* If any edges from predecessors are abnormal, antic_in is empty, so punt. Remember that the block has an incoming abnormal edge by setting the BB_VISITED flag. */ if (! (block->flags & BB_VISITED)) { for (e = block->pred; e; e = e->pred_next) if (e->flags & EDGE_ABNORMAL) { block->flags |= BB_VISITED; break; } } if (block->flags & BB_VISITED) { S = NULL; goto visit_sons; } old = set_new (false); set_copy (old, ANTIC_IN (block)); ANTIC_OUT = set_new (true); /* If the block has no successors, ANTIC_OUT is empty, because it is the exit block. */ if (block->succ == NULL); /* If we have one successor, we could have some phi nodes to translate through. */ else if (block->succ->succ_next == NULL) { phi_translate_set (ANTIC_OUT, ANTIC_IN(block->succ->dest), block, block->succ->dest); } /* If we have multiple successors, we take the intersection of all of them. */ else { varray_type worklist; edge e; size_t i; basic_block bprime, first; VARRAY_BB_INIT (worklist, 1, "succ"); e = block->succ; while (e) { VARRAY_PUSH_BB (worklist, e->dest); e = e->succ_next; } first = VARRAY_BB (worklist, 0); set_copy (ANTIC_OUT, ANTIC_IN (first)); for (i = 1; i < VARRAY_ACTIVE_SIZE (worklist); i++) { bprime = VARRAY_BB (worklist, i); node = ANTIC_OUT->head; while (node) { tree val; value_set_node_t next = node->next; val = get_value_handle (node->expr); if (!set_contains_value (ANTIC_IN (bprime), val)) set_remove (ANTIC_OUT, node->expr); node = next; } } VARRAY_CLEAR (worklist); } /* Generate ANTIC_OUT - TMP_GEN */ S = set_subtract (ANTIC_OUT, TMP_GEN (block), false); /* Start ANTIC_IN with EXP_GEN - TMP_GEN */ ANTIC_IN (block) = set_subtract (EXP_GEN (block),TMP_GEN (block), true); /* Then union in the ANTIC_OUT - TMP_GEN values, to get ANTIC_OUT U EXP_GEN - TMP_GEN */ for (node = S->head; node; node = node->next) { value_insert_into_set (ANTIC_IN (block), node->expr); } clean (ANTIC_IN (block)); if (!set_equal (old, ANTIC_IN (block))) changed = true; visit_sons: if (dump_file && (dump_flags & TDF_DETAILS)) { if (ANTIC_OUT) print_value_set (dump_file, ANTIC_OUT, "ANTIC_OUT", block->index); print_value_set (dump_file, ANTIC_IN (block), "ANTIC_IN", block->index); if (S) print_value_set (dump_file, S, "S", block->index); } for (son = first_dom_son (CDI_POST_DOMINATORS, block); son; son = next_dom_son (CDI_POST_DOMINATORS, son)) { changed |= compute_antic_aux (son); } return changed; } /* Compute ANTIC sets. */ static void compute_antic (void) { bool changed = true; basic_block bb; int num_iterations = 0; FOR_ALL_BB (bb) { ANTIC_IN (bb) = set_new (true); bb->flags &= ~BB_VISITED; } while (changed) { num_iterations++; changed = false; changed = compute_antic_aux (EXIT_BLOCK_PTR); } if (num_iterations > 2 && dump_file && (dump_flags & TDF_STATS)) fprintf (dump_file, "compute_antic required %d iterations\n", num_iterations); } /* Perform insertion of partially redundant values. For BLOCK, do the following: 1. Propagate the NEW_SETS of the dominator into the current block. If the block has multiple predecessors, 2a. Iterate over the ANTIC expressions for the block to see if any of them are partially redundant. 2b. If so, insert them into the necessary predecessors to make the expression fully redundant. 2c. Insert a new PHI merging the values of the predecessors. 2d. Insert the new PHI, and the new expressions, into the NEW_SETS set. 3. Recursively call ourselves on the dominator children of BLOCK. */ static bool insert_aux (basic_block block) { basic_block son; bool new_stuff = false; if (block) { value_set_node_t e; basic_block dom; dom = get_immediate_dominator (CDI_DOMINATORS, block); if (dom) { e = NEW_SETS (dom)->head; while (e) { insert_into_set (NEW_SETS (block), e->expr); value_replace_in_set (AVAIL_OUT (block), e->expr); e = e->next; } if (block->pred->pred_next) { value_set_node_t node; for (node = ANTIC_IN (block)->head; node; node = node->next) { if (TREE_CODE_CLASS (TREE_CODE (node->expr)) == '2' || TREE_CODE_CLASS (TREE_CODE (node->expr)) == '1') { tree *avail; tree val; bool by_some = false; bool all_same = true; tree first_s = NULL; edge pred; basic_block bprime; tree eprime; val = get_value_handle (node->expr); if (set_contains_value (PHI_GEN (block), val)) continue; if (set_contains_value (AVAIL_OUT (dom), val)) { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Found fully redundant value\n"); continue; } avail = xcalloc (last_basic_block, sizeof (tree)); for (pred = block->pred; pred; pred = pred->pred_next) { tree vprime; tree edoubleprime; bprime = pred->src; eprime = phi_translate (node->expr, ANTIC_IN (block), bprime, block); if (eprime == NULL) continue; vprime = get_value_handle (eprime); if (!vprime) abort (); edoubleprime = find_leader (AVAIL_OUT (bprime), vprime); if (edoubleprime == NULL) { avail[bprime->index] = eprime; all_same = false; } else { avail[bprime->index] = edoubleprime; by_some = true; if (first_s == NULL) first_s = edoubleprime; else if (first_s != edoubleprime) all_same = false; if (first_s != edoubleprime && operand_equal_p (first_s, edoubleprime, 0)) abort (); } } if (!all_same && by_some) { tree temp; tree type = TREE_TYPE (avail[block->pred->src->index]); tree v; if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Found partial redundancy for expression "); print_generic_expr (dump_file, node->expr, 0); fprintf (dump_file, "\n"); } /* Make the necessary insertions. */ for (pred = block->pred; pred; pred = pred->pred_next) { bprime = pred->src; eprime = avail[bprime->index]; if (TREE_CODE_CLASS (TREE_CODE (eprime)) == '2') { tree s1, s2; tree newexpr; s1 = find_leader (AVAIL_OUT (bprime), TREE_OPERAND (eprime, 0)); /* Depending on the order we process DOM branches in, the value may not have propagated to all the dom children yet during this iteration. In this case, the value will always be in the NEW_SETS for *our* dominator */ if (!s1) s1 = find_leader (NEW_SETS (dom), TREE_OPERAND (eprime, 0)); if (!s1) abort (); s2 = find_leader (AVAIL_OUT (bprime), TREE_OPERAND (eprime, 1)); if (!s2) s2 = find_leader (NEW_SETS (dom), TREE_OPERAND (eprime, 1)); if (!s2) abort (); temp = create_tmp_var (TREE_TYPE (eprime), "pretmp"); add_referenced_tmp_var (temp); newexpr = build (TREE_CODE (eprime), TREE_TYPE (eprime), s1, s2); newexpr = build (MODIFY_EXPR, TREE_TYPE (eprime), temp, newexpr); temp = make_ssa_name (temp, newexpr); TREE_OPERAND (newexpr, 0) = temp; bsi_insert_on_edge (pred, newexpr); bsi_commit_edge_inserts (NULL); if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Inserted "); print_generic_expr (dump_file, newexpr, 0); fprintf (dump_file, " in predecessor %d\n", pred->src->index); } pre_stats.insertions++; v = lookup_or_add (value_table, eprime); add (value_table, temp, v); insert_into_set (NEW_SETS (bprime), temp); value_insert_into_set (AVAIL_OUT (bprime), temp); avail[bprime->index] = temp; } else if (TREE_CODE_CLASS (TREE_CODE (eprime)) == '1') { tree s1; tree newexpr; s1 = find_leader (AVAIL_OUT (bprime), TREE_OPERAND (eprime, 0)); /* Depending on the order we process DOM branches in, the value may not have propagated to all the dom children yet in the current iteration, but it will be in NEW_SETS if it is not yet propagated. */ if (!s1) s1 = find_leader (NEW_SETS (dom), TREE_OPERAND (eprime, 0)); if (!s1) abort (); temp = create_tmp_var (TREE_TYPE (eprime), "pretmp"); add_referenced_tmp_var (temp); newexpr = build (TREE_CODE (eprime), TREE_TYPE (eprime), s1); newexpr = build (MODIFY_EXPR, TREE_TYPE (eprime), temp, newexpr); temp = make_ssa_name (temp, newexpr); TREE_OPERAND (newexpr, 0) = temp; bsi_insert_on_edge (pred, newexpr); bsi_commit_edge_inserts (NULL); if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Inserted "); print_generic_expr (dump_file, newexpr, 0); fprintf (dump_file, " in predecessor %d\n", pred->src->index); } pre_stats.insertions++; v = lookup_or_add (value_table, eprime); add (value_table, temp, v); insert_into_set (NEW_SETS (bprime), temp); value_insert_into_set (AVAIL_OUT (bprime), temp); avail[bprime->index] = temp; } } /* Now build a phi for the new variable. */ temp = create_tmp_var (type, "prephitmp"); add_referenced_tmp_var (temp); temp = create_phi_node (temp, block); add (value_table, PHI_RESULT (temp), val); #if 0 if (!set_contains_value (AVAIL_OUT (block), val)) insert_into_set (AVAIL_OUT (block), PHI_RESULT (temp)); else #endif value_replace_in_set (AVAIL_OUT (block), PHI_RESULT (temp)); for (pred = block->pred; pred; pred = pred->pred_next) { add_phi_arg (&temp, avail[pred->src->index], pred); } if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Created phi "); print_generic_expr (dump_file, temp, 0); fprintf (dump_file, " in block %d\n", block->index); } pre_stats.phis++; new_stuff = true; insert_into_set (NEW_SETS (block), PHI_RESULT (temp)); insert_into_set (PHI_GEN (block), PHI_RESULT (temp)); } free (avail); } } } } } for (son = first_dom_son (CDI_DOMINATORS, block); son; son = next_dom_son (CDI_DOMINATORS, son)) { new_stuff |= insert_aux (son); } return new_stuff; } /* Perform insertion of partially redundant values. */ static void insert (void) { bool new_stuff = true; basic_block bb; int num_iterations = 0; FOR_ALL_BB (bb) NEW_SETS (bb) = set_new (true); while (new_stuff) { num_iterations++; new_stuff = false; new_stuff = insert_aux (ENTRY_BLOCK_PTR); } if (num_iterations > 2 && dump_file && (dump_flags & TDF_STATS)) fprintf (dump_file, "insert required %d iterations\n", num_iterations); } /* Return true if EXPR has no defining statement in this procedure, *AND* isn't a live-on-entry parameter. */ static bool is_undefined_value (tree expr) { #ifdef ENABLE_CHECKING /* We should never be handed DECL's */ if (DECL_P (expr)) abort (); #endif if (TREE_CODE (expr) == SSA_NAME) { /* XXX: Is this the correct test? */ if (TREE_CODE (SSA_NAME_VAR (expr)) == PARM_DECL) return false; if (IS_EMPTY_STMT (SSA_NAME_DEF_STMT (expr))) return true; } return false; } /* Compute the AVAIL set for BLOCK. This function performs value numbering of the statements in BLOCK. The AVAIL sets are built from information we glean while doing this value numbering, since the AVAIL sets contain only entry per value. AVAIL_IN[BLOCK] = AVAIL_OUT[dom(BLOCK)]. AVAIL_OUT[BLOCK] = AVAIL_IN[BLOCK] U PHI_GEN[BLOCK] U TMP_GEN[BLOCK]. */ static void compute_avail (basic_block block) { basic_block son; /* For arguments with default definitions, we pretend they are defined in the entry block. */ if (block == ENTRY_BLOCK_PTR) { tree param; for (param = DECL_ARGUMENTS (current_function_decl); param; param = TREE_CHAIN (param)) { if (default_def (param) != NULL) { tree val; tree def = default_def (param); val = lookup_or_add (value_table, def); insert_into_set (TMP_GEN (block), def); value_insert_into_set (AVAIL_OUT (block), def); } } } else if (block) { block_stmt_iterator bsi; tree stmt, phi; basic_block dom; dom = get_immediate_dominator (CDI_DOMINATORS, block); if (dom) set_copy (AVAIL_OUT (block), AVAIL_OUT (dom)); for (phi = phi_nodes (block); phi; phi = TREE_CHAIN (phi)) { /* Ignore virtual PHIs until we can do PRE on expressions with virtual operands. */ if (!is_gimple_reg (SSA_NAME_VAR (PHI_RESULT (phi)))) continue; lookup_or_add (value_table, PHI_RESULT (phi)); value_insert_into_set (AVAIL_OUT (block), PHI_RESULT (phi)); insert_into_set (PHI_GEN (block), PHI_RESULT (phi)); } for (bsi = bsi_start (block); !bsi_end_p (bsi); bsi_next (&bsi)) { tree op0, op1; stmt = bsi_stmt (bsi); get_stmt_operands (stmt); if (NUM_VUSES (STMT_VUSE_OPS (stmt)) || NUM_V_MUST_DEFS (STMT_V_MUST_DEF_OPS (stmt)) || NUM_V_MAY_DEFS (STMT_V_MAY_DEF_OPS (stmt)) || stmt_ann (stmt)->has_volatile_ops) { size_t j; for (j = 0; j < NUM_DEFS (STMT_DEF_OPS (stmt)); j++) { tree def = DEF_OP (STMT_DEF_OPS (stmt), j); lookup_or_add (value_table, def); insert_into_set (TMP_GEN (block), def); value_insert_into_set (AVAIL_OUT (block), def); } continue; } else if (TREE_CODE (stmt) == RETURN_EXPR && TREE_OPERAND (stmt, 0) && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR) stmt = TREE_OPERAND (stmt, 0); if (TREE_CODE (stmt) == MODIFY_EXPR) { op0 = TREE_OPERAND (stmt, 0); if (TREE_CODE (op0) != SSA_NAME) continue; if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op0)) continue; op1 = TREE_OPERAND (stmt, 1); if (TREE_CODE_CLASS (TREE_CODE (op1)) == 'c') { add (value_table, op0, lookup_or_add (value_table, op1)); insert_into_set (TMP_GEN (block), op0); value_insert_into_set (AVAIL_OUT (block), op0); } else if (TREE_CODE_CLASS (TREE_CODE (op1)) == '2') { tree bop1, bop2; tree val, val1, val2; tree newt; bop1 = TREE_OPERAND (op1, 0); bop2 = TREE_OPERAND (op1, 1); val1 = lookup_or_add (value_table, bop1); val2 = lookup_or_add (value_table, bop2); newt = pool_alloc (binary_node_pool); memcpy (newt, op1, tree_size (op1)); TREE_OPERAND (newt, 0) = val1; TREE_OPERAND (newt, 1) = val2; val = lookup_or_add (value_table, newt); add (value_table, op0, val); if (!is_undefined_value (bop1)) value_insert_into_set (EXP_GEN (block), bop1); if (!is_undefined_value (bop2)) value_insert_into_set (EXP_GEN (block), bop2); value_insert_into_set (EXP_GEN (block), newt); insert_into_set (TMP_GEN (block), op0); value_insert_into_set (AVAIL_OUT (block), op0); } else if (TREE_CODE_CLASS (TREE_CODE (op1)) == '1') { tree uop; tree val, val1; tree newt; uop = TREE_OPERAND (op1, 0); val1 = lookup_or_add (value_table, uop); newt = pool_alloc (unary_node_pool); memcpy (newt, op1, tree_size (op1)); TREE_OPERAND (newt, 0) = val1; val = lookup_or_add (value_table, newt); add (value_table, op0, val); if (!is_undefined_value (uop)) value_insert_into_set (EXP_GEN (block), uop); value_insert_into_set (EXP_GEN (block), newt); insert_into_set (TMP_GEN (block), op0); value_insert_into_set (AVAIL_OUT (block), op0); } else if (TREE_CODE (op1) == SSA_NAME) { tree val = lookup_or_add (value_table, op1); add (value_table, op0, val); if (!is_undefined_value (op1)) value_insert_into_set (EXP_GEN (block), op1); insert_into_set (TMP_GEN (block), op0); value_insert_into_set (AVAIL_OUT (block), op0); } else { size_t j; for (j = 0; j < NUM_DEFS (STMT_DEF_OPS (stmt)); j++) { tree def = DEF_OP (STMT_DEF_OPS (stmt), j); lookup_or_add (value_table, def); insert_into_set (TMP_GEN (block), def); value_insert_into_set (AVAIL_OUT (block), def); value_insert_into_set (AVAIL_OUT (block), op0); } } } else { size_t j; for (j = 0; j < NUM_DEFS (STMT_DEF_OPS (stmt)); j++) { tree def = DEF_OP (STMT_DEF_OPS (stmt), j); lookup_or_add (value_table, def); insert_into_set (TMP_GEN (block), def); value_insert_into_set (AVAIL_OUT (block), def); } } } } for (son = first_dom_son (CDI_DOMINATORS, block); son; son = next_dom_son (CDI_DOMINATORS, son)) compute_avail (son); } /* Eliminate fully redundant computations. */ static void eliminate (void) { basic_block b; FOR_EACH_BB (b) { block_stmt_iterator i; for (i = bsi_start (b); !bsi_end_p (i); bsi_next (&i)) { tree stmt = bsi_stmt (i); if (NUM_VUSES (STMT_VUSE_OPS (stmt)) || NUM_V_MUST_DEFS (STMT_V_MUST_DEF_OPS (stmt)) || NUM_V_MAY_DEFS (STMT_V_MAY_DEF_OPS (stmt)) || stmt_ann (stmt)->has_volatile_ops) continue; /* Lookup the RHS of the expression, see if we have an available computation for it. If so, replace the RHS with the available computation. */ if (TREE_CODE (stmt) == MODIFY_EXPR) { tree t = TREE_OPERAND (stmt, 0); tree expr = TREE_OPERAND (stmt, 1); tree sprime; /* There is no point in eliminating NOP_EXPR, it isn't supposed to generate any code. */ if (TREE_CODE (expr) == NOP_EXPR || (TREE_CODE_CLASS (TREE_CODE (expr)) != '2' && TREE_CODE_CLASS (TREE_CODE (expr)) != '1')) continue; sprime = find_leader (AVAIL_OUT (b), lookup (value_table, t)); if (sprime && sprime != t && may_propagate_copy (sprime, TREE_OPERAND (stmt, 1))) { if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Replaced "); print_generic_expr (dump_file, expr, 0); fprintf (dump_file, " with "); print_generic_expr (dump_file, sprime, 0); fprintf (dump_file, " in "); print_generic_stmt (dump_file, stmt, 0); } pre_stats.eliminations++; propagate_value (&TREE_OPERAND (stmt, 1), sprime); modify_stmt (stmt); } } } } } /* Main entry point to the SSA-PRE pass. PHASE indicates which dump file from the DUMP_FILES array to use when dumping debugging information. */ static void execute_pre (void) { size_t tsize; basic_block bb; pre_uid = num_referenced_vars; memset (&pre_stats, 0, sizeof (pre_stats)); FOR_ALL_BB (bb) { bb->aux = xcalloc (1, sizeof (struct bb_value_sets)); } phi_translate_table = htab_create (511, expr_pred_trans_hash, expr_pred_trans_eq, free); value_table = htab_create (511, val_expr_pair_hash, val_expr_pair_expr_eq, free); value_set_pool = create_alloc_pool ("Value sets", sizeof (struct value_set), 30); value_set_node_pool = create_alloc_pool ("Value set nodes", sizeof (struct value_set_node), 30); calculate_dominance_info (CDI_POST_DOMINATORS); calculate_dominance_info (CDI_DOMINATORS); tsize = tree_size (build (PLUS_EXPR, void_type_node, NULL_TREE, NULL_TREE)); binary_node_pool = create_alloc_pool ("Binary tree nodes", tsize, 30); tsize = tree_size (build1 (NEGATE_EXPR, void_type_node, NULL_TREE)); unary_node_pool = create_alloc_pool ("Unary tree nodes", tsize, 30); FOR_ALL_BB (bb) { EXP_GEN (bb) = set_new (true); PHI_GEN (bb) = set_new (true); TMP_GEN (bb) = set_new (false); AVAIL_OUT (bb) = set_new (true); } compute_avail (ENTRY_BLOCK_PTR); if (dump_file && (dump_flags & TDF_DETAILS)) { FOR_ALL_BB (bb) { print_value_set (dump_file, EXP_GEN (bb), "exp_gen", bb->index); print_value_set (dump_file, TMP_GEN (bb), "tmp_gen", bb->index); print_value_set (dump_file, AVAIL_OUT (bb), "avail_out", bb->index); } } /* Insert can get quite slow on an incredibly large number of basic blocks due to some quadratic behavior. Until this behavior is fixed, don't run it when he have an incredibly large number of bb's. If we aren't going to run insert, there is no point in computing ANTIC, either, even though it's plenty fast. */ if (n_basic_blocks < 4000) { compute_antic (); insert (); } eliminate (); if (dump_file && (dump_flags & TDF_STATS)) { fprintf (dump_file, "Insertions:%d\n", pre_stats.insertions); fprintf (dump_file, "New PHIs:%d\n", pre_stats.phis); fprintf (dump_file, "Eliminated:%d\n", pre_stats.eliminations); } free_alloc_pool (value_set_pool); free_alloc_pool (value_set_node_pool); free_alloc_pool (binary_node_pool); free_alloc_pool (unary_node_pool); htab_delete (value_table); htab_delete (phi_translate_table); FOR_ALL_BB (bb) { free (bb->aux); bb->aux = NULL; } free_dominance_info (CDI_POST_DOMINATORS); } static bool gate_pre (void) { return flag_tree_pre != 0; } struct tree_opt_pass pass_pre = { "pre", /* name */ gate_pre, /* gate */ execute_pre, /* execute */ NULL, /* sub */ NULL, /* next */ 0, /* static_pass_number */ TV_TREE_PRE, /* tv_id */ PROP_no_crit_edges | PROP_cfg | PROP_ssa,/* properties_required */ 0, /* properties_provided */ 0, /* properties_destroyed */ 0, /* todo_flags_start */ TODO_dump_func | TODO_ggc_collect | TODO_verify_ssa /* todo_flags_finish */ };