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/* Reassociation for trees. Copyright (C) 2005, 2007 Free Software Foundation, Inc. Contributed by Daniel Berlin <dan@dberlin.org> 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 "errors.h" #include "ggc.h" #include "tree.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 "tree-iterator.h" #include "tree-pass.h" #include "alloc-pool.h" #include "vec.h" #include "langhooks.h" /* This is a simple global reassociation pass. It is, in part, based on the LLVM pass of the same name (They do some things more/less than we do, in different orders, etc). It consists of five steps: 1. Breaking up subtract operations into addition + negate, where it would promote the reassociation of adds. 2. Left linearization of the expression trees, so that (A+B)+(C+D) becomes (((A+B)+C)+D), which is easier for us to rewrite later. During linearization, we place the operands of the binary expressions into a vector of operand_entry_t 3. Optimization of the operand lists, eliminating things like a + -a, a & a, etc. 4. Rewrite the expression trees we linearized and optimized so they are in proper rank order. 5. Repropagate negates, as nothing else will clean it up ATM. A bit of theory on #4, since nobody seems to write anything down about why it makes sense to do it the way they do it: We could do this much nicer theoretically, but don't (for reasons explained after how to do it theoretically nice :P). In order to promote the most redundancy elimination, you want binary expressions whose operands are the same rank (or preferably, the same value) exposed to the redundancy eliminator, for possible elimination. So the way to do this if we really cared, is to build the new op tree from the leaves to the roots, merging as you go, and putting the new op on the end of the worklist, until you are left with one thing on the worklist. IE if you have to rewrite the following set of operands (listed with rank in parentheses), with opcode PLUS_EXPR: a (1), b (1), c (1), d (2), e (2) We start with our merge worklist empty, and the ops list with all of those on it. You want to first merge all leaves of the same rank, as much as possible. So first build a binary op of mergetmp = a + b, and put "mergetmp" on the merge worklist. Because there is no three operand form of PLUS_EXPR, c is not going to be exposed to redundancy elimination as a rank 1 operand. So you might as well throw it on the merge worklist (you could also consider it to now be a rank two operand, and merge it with d and e, but in this case, you then have evicted e from a binary op. So at least in this situation, you can't win.) Then build a binary op of d + e mergetmp2 = d + e and put mergetmp2 on the merge worklist. so merge worklist = {mergetmp, c, mergetmp2} Continue building binary ops of these operations until you have only one operation left on the worklist. So we have build binary op mergetmp3 = mergetmp + c worklist = {mergetmp2, mergetmp3} mergetmp4 = mergetmp2 + mergetmp3 worklist = {mergetmp4} because we have one operation left, we can now just set the original statement equal to the result of that operation. This will at least expose a + b and d + e to redundancy elimination as binary operations. For extra points, you can reuse the old statements to build the mergetmps, since you shouldn't run out. So why don't we do this? Because it's expensive, and rarely will help. Most trees we are reassociating have 3 or less ops. If they have 2 ops, they already will be written into a nice single binary op. If you have 3 ops, a single simple check suffices to tell you whether the first two are of the same rank. If so, you know to order it mergetmp = op1 + op2 newstmt = mergetmp + op3 instead of mergetmp = op2 + op3 newstmt = mergetmp + op1 If all three are of the same rank, you can't expose them all in a single binary operator anyway, so the above is *still* the best you can do. Thus, this is what we do. When we have three ops left, we check to see what order to put them in, and call it a day. As a nod to vector sum reduction, we check if any of ops are a really a phi node that is a destructive update for the associating op, and keep the destructive update together for vector sum reduction recognition. */ /* Statistics */ static struct { int linearized; int constants_eliminated; int ops_eliminated; int rewritten; } reassociate_stats; /* Operator, rank pair. */ typedef struct operand_entry { unsigned int rank; tree op; } *operand_entry_t; static alloc_pool operand_entry_pool; /* Starting rank number for a given basic block, so that we can rank operations using unmovable instructions in that BB based on the bb depth. */ static unsigned int *bb_rank; /* Operand->rank hashtable. */ static htab_t operand_rank; /* Look up the operand rank structure for expression E. */ static operand_entry_t find_operand_rank (tree e) { void **slot; struct operand_entry vrd; vrd.op = e; slot = htab_find_slot (operand_rank, &vrd, NO_INSERT); if (!slot) return NULL; return ((operand_entry_t) *slot); } /* Insert {E,RANK} into the operand rank hashtable. */ static void insert_operand_rank (tree e, unsigned int rank) { void **slot; operand_entry_t new_pair = pool_alloc (operand_entry_pool); new_pair->op = e; new_pair->rank = rank; slot = htab_find_slot (operand_rank, new_pair, INSERT); gcc_assert (*slot == NULL); *slot = new_pair; } /* Return the hash value for a operand rank structure */ static hashval_t operand_entry_hash (const void *p) { const operand_entry_t vr = (operand_entry_t) p; return iterative_hash_expr (vr->op, 0); } /* Return true if two operand rank structures are equal. */ static int operand_entry_eq (const void *p1, const void *p2) { const operand_entry_t vr1 = (operand_entry_t) p1; const operand_entry_t vr2 = (operand_entry_t) p2; return vr1->op == vr2->op; } /* Given an expression E, return the rank of the expression. */ static unsigned int get_rank (tree e) { operand_entry_t vr; /* Constants have rank 0. */ if (is_gimple_min_invariant (e)) return 0; /* SSA_NAME's have the rank of the expression they are the result of. For globals and uninitialized values, the rank is 0. For function arguments, use the pre-setup rank. For PHI nodes, stores, asm statements, etc, we use the rank of the BB. For simple operations, the rank is the maximum rank of any of its operands, or the bb_rank, whichever is less. I make no claims that this is optimal, however, it gives good results. */ if (TREE_CODE (e) == SSA_NAME) { tree stmt; tree rhs; unsigned int rank, maxrank; int i; if (TREE_CODE (SSA_NAME_VAR (e)) == PARM_DECL && e == default_def (SSA_NAME_VAR (e))) return find_operand_rank (e)->rank; stmt = SSA_NAME_DEF_STMT (e); if (bb_for_stmt (stmt) == NULL) return 0; if (TREE_CODE (stmt) != MODIFY_EXPR || !ZERO_SSA_OPERANDS (stmt, SSA_OP_VIRTUAL_DEFS)) return bb_rank[bb_for_stmt (stmt)->index]; /* If we already have a rank for this expression, use that. */ vr = find_operand_rank (e); if (vr) return vr->rank; /* Otherwise, find the maximum rank for the operands, or the bb rank, whichever is less. */ rank = 0; maxrank = bb_rank[bb_for_stmt(stmt)->index]; rhs = TREE_OPERAND (stmt, 1); if (TREE_CODE_LENGTH (TREE_CODE (rhs)) == 0) rank = MAX (rank, get_rank (rhs)); else { for (i = 0; i < TREE_CODE_LENGTH (TREE_CODE (rhs)) && TREE_OPERAND (rhs, i) && rank != maxrank; i++) rank = MAX(rank, get_rank (TREE_OPERAND (rhs, i))); } if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Rank for "); print_generic_expr (dump_file, e, 0); fprintf (dump_file, " is %d\n", (rank + 1)); } /* Note the rank in the hashtable so we don't recompute it. */ insert_operand_rank (e, (rank + 1)); return (rank + 1); } /* Globals, etc, are rank 0 */ return 0; } DEF_VEC_P(operand_entry_t); DEF_VEC_ALLOC_P(operand_entry_t, heap); /* We want integer ones to end up last no matter what, since they are the ones we can do the most with. */ #define INTEGER_CONST_TYPE 1 << 3 #define FLOAT_CONST_TYPE 1 << 2 #define OTHER_CONST_TYPE 1 << 1 /* Classify an invariant tree into integer, float, or other, so that we can sort them to be near other constants of the same type. */ static inline int constant_type (tree t) { if (INTEGRAL_TYPE_P (TREE_TYPE (t))) return INTEGER_CONST_TYPE; else if (SCALAR_FLOAT_TYPE_P (TREE_TYPE (t))) return FLOAT_CONST_TYPE; else return OTHER_CONST_TYPE; } /* qsort comparison function to sort operand entries PA and PB by rank so that the sorted array is ordered by rank in decreasing order. */ static int sort_by_operand_rank (const void *pa, const void *pb) { const operand_entry_t oea = *(const operand_entry_t *)pa; const operand_entry_t oeb = *(const operand_entry_t *)pb; /* It's nicer for optimize_expression if constants that are likely to fold when added/multiplied//whatever are put next to each other. Since all constants have rank 0, order them by type. */ if (oeb->rank == 0 && oea->rank == 0) return constant_type (oeb->op) - constant_type (oea->op); /* Lastly, make sure the versions that are the same go next to each other. We use SSA_NAME_VERSION because it's stable. */ if ((oeb->rank - oea->rank == 0) && TREE_CODE (oea->op) == SSA_NAME && TREE_CODE (oeb->op) == SSA_NAME) return SSA_NAME_VERSION (oeb->op) - SSA_NAME_VERSION (oea->op); return oeb->rank - oea->rank; } /* Add an operand entry to *OPS for the tree operand OP. */ static void add_to_ops_vec (VEC(operand_entry_t, heap) **ops, tree op) { operand_entry_t oe = pool_alloc (operand_entry_pool); oe->op = op; oe->rank = get_rank (op); VEC_safe_push (operand_entry_t, heap, *ops, oe); } /* Return true if STMT is reassociable operation containing a binary operation with tree code CODE. */ static bool is_reassociable_op (tree stmt, enum tree_code code) { if (!IS_EMPTY_STMT (stmt) && TREE_CODE (stmt) == MODIFY_EXPR && TREE_CODE (TREE_OPERAND (stmt, 1)) == code && has_single_use (TREE_OPERAND (stmt, 0))) return true; return false; } /* Given NAME, if NAME is defined by a unary operation OPCODE, return the operand of the negate operation. Otherwise, return NULL. */ static tree get_unary_op (tree name, enum tree_code opcode) { tree stmt = SSA_NAME_DEF_STMT (name); tree rhs; if (TREE_CODE (stmt) != MODIFY_EXPR) return NULL_TREE; rhs = TREE_OPERAND (stmt, 1); if (TREE_CODE (rhs) == opcode) return TREE_OPERAND (rhs, 0); return NULL_TREE; } /* If CURR and LAST are a pair of ops that OPCODE allows us to eliminate through equivalences, do so, remove them from OPS, and return true. Otherwise, return false. */ static bool eliminate_duplicate_pair (enum tree_code opcode, VEC (operand_entry_t, heap) **ops, bool *all_done, unsigned int i, operand_entry_t curr, operand_entry_t last) { /* If we have two of the same op, and the opcode is & |, min, or max, we can eliminate one of them. If we have two of the same op, and the opcode is ^, we can eliminate both of them. */ if (last && last->op == curr->op) { switch (opcode) { case MAX_EXPR: case MIN_EXPR: case BIT_IOR_EXPR: case BIT_AND_EXPR: if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Equivalence: "); print_generic_expr (dump_file, curr->op, 0); fprintf (dump_file, " [&|minmax] "); print_generic_expr (dump_file, last->op, 0); fprintf (dump_file, " -> "); print_generic_stmt (dump_file, last->op, 0); } VEC_ordered_remove (operand_entry_t, *ops, i); reassociate_stats.ops_eliminated ++; return true; case BIT_XOR_EXPR: if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Equivalence: "); print_generic_expr (dump_file, curr->op, 0); fprintf (dump_file, " ^ "); print_generic_expr (dump_file, last->op, 0); fprintf (dump_file, " -> nothing\n"); } reassociate_stats.ops_eliminated += 2; if (VEC_length (operand_entry_t, *ops) == 2) { VEC_free (operand_entry_t, heap, *ops); *ops = NULL; add_to_ops_vec (ops, fold_convert (TREE_TYPE (last->op), integer_zero_node)); *all_done = true; } else { VEC_ordered_remove (operand_entry_t, *ops, i-1); VEC_ordered_remove (operand_entry_t, *ops, i-1); } return true; default: break; } } return false; } /* If OPCODE is PLUS_EXPR, CURR->OP is really a negate expression, look in OPS for a corresponding positive operation to cancel it out. If we find one, remove the other from OPS, replace OPS[CURRINDEX] with 0, and return true. Otherwise, return false. */ static bool eliminate_plus_minus_pair (enum tree_code opcode, VEC (operand_entry_t, heap) **ops, unsigned int currindex, operand_entry_t curr) { tree negateop; unsigned int i; operand_entry_t oe; if (opcode != PLUS_EXPR || TREE_CODE (curr->op) != SSA_NAME) return false; negateop = get_unary_op (curr->op, NEGATE_EXPR); if (negateop == NULL_TREE) return false; /* Any non-negated version will have a rank that is one less than the current rank. So once we hit those ranks, if we don't find one, we can stop. */ for (i = currindex + 1; VEC_iterate (operand_entry_t, *ops, i, oe) && oe->rank >= curr->rank - 1 ; i++) { if (oe->op == negateop) { if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Equivalence: "); print_generic_expr (dump_file, negateop, 0); fprintf (dump_file, " + -"); print_generic_expr (dump_file, oe->op, 0); fprintf (dump_file, " -> 0\n"); } VEC_ordered_remove (operand_entry_t, *ops, i); add_to_ops_vec (ops, fold_convert(TREE_TYPE (oe->op), integer_zero_node)); VEC_ordered_remove (operand_entry_t, *ops, currindex); reassociate_stats.ops_eliminated ++; return true; } } return false; } /* If OPCODE is BIT_IOR_EXPR, BIT_AND_EXPR, and, CURR->OP is really a bitwise not expression, look in OPS for a corresponding operand to cancel it out. If we find one, remove the other from OPS, replace OPS[CURRINDEX] with 0, and return true. Otherwise, return false. */ static bool eliminate_not_pairs (enum tree_code opcode, VEC (operand_entry_t, heap) **ops, unsigned int currindex, operand_entry_t curr) { tree notop; unsigned int i; operand_entry_t oe; if ((opcode != BIT_IOR_EXPR && opcode != BIT_AND_EXPR) || TREE_CODE (curr->op) != SSA_NAME) return false; notop = get_unary_op (curr->op, BIT_NOT_EXPR); if (notop == NULL_TREE) return false; /* Any non-not version will have a rank that is one less than the current rank. So once we hit those ranks, if we don't find one, we can stop. */ for (i = currindex + 1; VEC_iterate (operand_entry_t, *ops, i, oe) && oe->rank >= curr->rank - 1; i++) { if (oe->op == notop) { if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Equivalence: "); print_generic_expr (dump_file, notop, 0); if (opcode == BIT_AND_EXPR) fprintf (dump_file, " & ~"); else if (opcode == BIT_IOR_EXPR) fprintf (dump_file, " | ~"); print_generic_expr (dump_file, oe->op, 0); if (opcode == BIT_AND_EXPR) fprintf (dump_file, " -> 0\n"); else if (opcode == BIT_IOR_EXPR) fprintf (dump_file, " -> -1\n"); } if (opcode == BIT_AND_EXPR) oe->op = fold_convert (TREE_TYPE (oe->op), integer_zero_node); else if (opcode == BIT_IOR_EXPR) oe->op = build_low_bits_mask (TREE_TYPE (oe->op), TYPE_PRECISION (TREE_TYPE (oe->op))); reassociate_stats.ops_eliminated += VEC_length (operand_entry_t, *ops) - 1; VEC_free (operand_entry_t, heap, *ops); *ops = NULL; VEC_safe_push (operand_entry_t, heap, *ops, oe); return true; } } return false; } /* Use constant value that may be present in OPS to try to eliminate operands. Note that this function is only really used when we've eliminated ops for other reasons, or merged constants. Across single statements, fold already does all of this, plus more. There is little point in duplicating logic, so I've only included the identities that I could ever construct testcases to trigger. */ static void eliminate_using_constants (enum tree_code opcode, VEC(operand_entry_t, heap) **ops) { operand_entry_t oelast = VEC_last (operand_entry_t, *ops); if (oelast->rank == 0 && INTEGRAL_TYPE_P (TREE_TYPE (oelast->op))) { switch (opcode) { case BIT_AND_EXPR: if (integer_zerop (oelast->op)) { if (VEC_length (operand_entry_t, *ops) != 1) { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Found & 0, removing all other ops\n"); reassociate_stats.ops_eliminated += VEC_length (operand_entry_t, *ops) - 1; VEC_free (operand_entry_t, heap, *ops); *ops = NULL; VEC_safe_push (operand_entry_t, heap, *ops, oelast); return; } } else if (integer_all_onesp (oelast->op)) { if (VEC_length (operand_entry_t, *ops) != 1) { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Found & -1, removing\n"); VEC_pop (operand_entry_t, *ops); reassociate_stats.ops_eliminated++; } } break; case BIT_IOR_EXPR: if (integer_all_onesp (oelast->op)) { if (VEC_length (operand_entry_t, *ops) != 1) { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Found | -1, removing all other ops\n"); reassociate_stats.ops_eliminated += VEC_length (operand_entry_t, *ops) - 1; VEC_free (operand_entry_t, heap, *ops); *ops = NULL; VEC_safe_push (operand_entry_t, heap, *ops, oelast); return; } } else if (integer_zerop (oelast->op)) { if (VEC_length (operand_entry_t, *ops) != 1) { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Found | 0, removing\n"); VEC_pop (operand_entry_t, *ops); reassociate_stats.ops_eliminated++; } } break; case MULT_EXPR: if (integer_zerop (oelast->op)) { if (VEC_length (operand_entry_t, *ops) != 1) { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Found * 0, removing all other ops\n"); reassociate_stats.ops_eliminated += VEC_length (operand_entry_t, *ops) - 1; VEC_free (operand_entry_t, heap, *ops); *ops = NULL; VEC_safe_push (operand_entry_t, heap, *ops, oelast); return; } } else if (integer_onep (oelast->op)) { if (VEC_length (operand_entry_t, *ops) != 1) { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Found * 1, removing\n"); VEC_pop (operand_entry_t, *ops); reassociate_stats.ops_eliminated++; return; } } break; case BIT_XOR_EXPR: case PLUS_EXPR: case MINUS_EXPR: if (integer_zerop (oelast->op)) { if (VEC_length (operand_entry_t, *ops) != 1) { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Found [|^+] 0, removing\n"); VEC_pop (operand_entry_t, *ops); reassociate_stats.ops_eliminated++; return; } } break; default: break; } } } /* Perform various identities and other optimizations on the list of operand entries, stored in OPS. The tree code for the binary operation between all the operands is OPCODE. */ static void optimize_ops_list (enum tree_code opcode, VEC (operand_entry_t, heap) **ops) { unsigned int length = VEC_length (operand_entry_t, *ops); unsigned int i; operand_entry_t oe; operand_entry_t oelast = NULL; bool iterate = false; if (length == 1) return; oelast = VEC_last (operand_entry_t, *ops); /* If the last two are constants, pop the constants off, merge them and try the next two. */ if (oelast->rank == 0 && is_gimple_min_invariant (oelast->op)) { operand_entry_t oelm1 = VEC_index (operand_entry_t, *ops, length - 2); if (oelm1->rank == 0 && is_gimple_min_invariant (oelm1->op) && lang_hooks.types_compatible_p (TREE_TYPE (oelm1->op), TREE_TYPE (oelast->op))) { tree folded = fold_binary (opcode, TREE_TYPE (oelm1->op), oelm1->op, oelast->op); if (folded && is_gimple_min_invariant (folded)) { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Merging constants\n"); VEC_pop (operand_entry_t, *ops); VEC_pop (operand_entry_t, *ops); add_to_ops_vec (ops, folded); reassociate_stats.constants_eliminated++; optimize_ops_list (opcode, ops); return; } } } eliminate_using_constants (opcode, ops); oelast = NULL; for (i = 0; VEC_iterate (operand_entry_t, *ops, i, oe);) { bool done = false; if (eliminate_not_pairs (opcode, ops, i, oe)) return; if (eliminate_duplicate_pair (opcode, ops, &done, i, oe, oelast) || (!done && eliminate_plus_minus_pair (opcode, ops, i, oe))) { if (done) return; iterate = true; oelast = NULL; continue; } oelast = oe; i++; } length = VEC_length (operand_entry_t, *ops); oelast = VEC_last (operand_entry_t, *ops); if (iterate) optimize_ops_list (opcode, ops); } /* Return true if OPERAND is defined by a PHI node which uses the LHS of STMT in it's operands. This is also known as a "destructive update" operation. */ static bool is_phi_for_stmt (tree stmt, tree operand) { tree def_stmt; tree lhs = TREE_OPERAND (stmt, 0); use_operand_p arg_p; ssa_op_iter i; if (TREE_CODE (operand) != SSA_NAME) return false; def_stmt = SSA_NAME_DEF_STMT (operand); if (TREE_CODE (def_stmt) != PHI_NODE) return false; FOR_EACH_PHI_ARG (arg_p, def_stmt, i, SSA_OP_USE) if (lhs == USE_FROM_PTR (arg_p)) return true; return false; } /* Recursively rewrite our linearized statements so that the operators match those in OPS[OPINDEX], putting the computation in rank order. */ static void rewrite_expr_tree (tree stmt, unsigned int opindex, VEC(operand_entry_t, heap) * ops) { tree rhs = TREE_OPERAND (stmt, 1); operand_entry_t oe; /* If we have three operands left, then we want to make sure the one that gets the double binary op are the ones with the same rank. The alternative we try is to see if this is a destructive update style statement, which is like: b = phi (a, ...) a = c + b; In that case, we want to use the destructive update form to expose the possible vectorizer sum reduction opportunity. In that case, the third operand will be the phi node. We could, of course, try to be better as noted above, and do a lot of work to try to find these opportunities in >3 operand cases, but it is unlikely to be worth it. */ if (opindex + 3 == VEC_length (operand_entry_t, ops)) { operand_entry_t oe1, oe2, oe3; oe1 = VEC_index (operand_entry_t, ops, opindex); oe2 = VEC_index (operand_entry_t, ops, opindex + 1); oe3 = VEC_index (operand_entry_t, ops, opindex + 2); if ((oe1->rank == oe2->rank && oe2->rank != oe3->rank) || (is_phi_for_stmt (stmt, oe3->op) && !is_phi_for_stmt (stmt, oe1->op) && !is_phi_for_stmt (stmt, oe2->op))) { struct operand_entry temp = *oe3; oe3->op = oe1->op; oe3->rank = oe1->rank; oe1->op = temp.op; oe1->rank= temp.rank; } } /* The final recursion case for this function is that you have exactly two operations left. If we had one exactly one op in the entire list to start with, we would have never called this function, and the tail recursion rewrites them one at a time. */ if (opindex + 2 == VEC_length (operand_entry_t, ops)) { operand_entry_t oe1, oe2; oe1 = VEC_index (operand_entry_t, ops, opindex); oe2 = VEC_index (operand_entry_t, ops, opindex + 1); if (TREE_OPERAND (rhs, 0) != oe1->op || TREE_OPERAND (rhs, 1) != oe2->op) { if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Transforming "); print_generic_expr (dump_file, rhs, 0); } TREE_OPERAND (rhs, 0) = oe1->op; TREE_OPERAND (rhs, 1) = oe2->op; update_stmt (stmt); if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, " into "); print_generic_stmt (dump_file, rhs, 0); } } return; } /* If we hit here, we should have 3 or more ops left. */ gcc_assert (opindex + 2 < VEC_length (operand_entry_t, ops)); /* Rewrite the next operator. */ oe = VEC_index (operand_entry_t, ops, opindex); if (oe->op != TREE_OPERAND (rhs, 1)) { if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Transforming "); print_generic_expr (dump_file, rhs, 0); } TREE_OPERAND (rhs, 1) = oe->op; update_stmt (stmt); if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, " into "); print_generic_stmt (dump_file, rhs, 0); } } /* Recurse on the LHS of the binary operator, which is guaranteed to be the non-leaf side. */ rewrite_expr_tree (SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0)), opindex + 1, ops); } /* Transform STMT, which is really (A +B) + (C + D) into the left linear form, ((A+B)+C)+D. Recurse on D if necessary. */ static void linearize_expr (tree stmt) { block_stmt_iterator bsinow, bsirhs; tree rhs = TREE_OPERAND (stmt, 1); enum tree_code rhscode = TREE_CODE (rhs); tree binrhs = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 1)); tree binlhs = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0)); tree newbinrhs = NULL_TREE; gcc_assert (is_reassociable_op (binlhs, TREE_CODE (rhs)) && is_reassociable_op (binrhs, TREE_CODE (rhs))); bsinow = bsi_for_stmt (stmt); bsirhs = bsi_for_stmt (binrhs); bsi_move_before (&bsirhs, &bsinow); TREE_OPERAND (rhs, 1) = TREE_OPERAND (TREE_OPERAND (binrhs, 1), 0); if (TREE_CODE (TREE_OPERAND (rhs, 1)) == SSA_NAME) newbinrhs = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 1)); TREE_OPERAND (TREE_OPERAND (binrhs, 1), 0) = TREE_OPERAND (binlhs, 0); TREE_OPERAND (rhs, 0) = TREE_OPERAND (binrhs, 0); if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Linearized: "); print_generic_stmt (dump_file, rhs, 0); } reassociate_stats.linearized++; update_stmt (binrhs); update_stmt (binlhs); update_stmt (stmt); TREE_VISITED (binrhs) = 1; TREE_VISITED (binlhs) = 1; TREE_VISITED (stmt) = 1; /* Tail recurse on the new rhs if it still needs reassociation. */ if (newbinrhs && is_reassociable_op (newbinrhs, rhscode)) linearize_expr (stmt); } /* If LHS has a single immediate use that is a MODIFY_EXPR, return it. Otherwise, return NULL. */ static tree get_single_immediate_use (tree lhs) { use_operand_p immuse; tree immusestmt; if (TREE_CODE (lhs) == SSA_NAME && single_imm_use (lhs, &immuse, &immusestmt)) { if (TREE_CODE (immusestmt) == RETURN_EXPR) immusestmt = TREE_OPERAND (immusestmt, 0); if (TREE_CODE (immusestmt) == MODIFY_EXPR) return immusestmt; } return NULL_TREE; } static VEC(tree, heap) *broken_up_subtracts; /* Recursively negate the value of TONEGATE, and return the SSA_NAME representing the negated value. Insertions of any necessary instructions go before BSI. This function is recursive in that, if you hand it "a_5" as the value to negate, and a_5 is defined by "a_5 = b_3 + b_4", it will transform b_3 + b_4 into a_5 = -b_3 + -b_4. */ static tree negate_value (tree tonegate, block_stmt_iterator *bsi) { tree negatedef = tonegate; tree resultofnegate; if (TREE_CODE (tonegate) == SSA_NAME) negatedef = SSA_NAME_DEF_STMT (tonegate); /* If we are trying to negate a name, defined by an add, negate the add operands instead. */ if (TREE_CODE (tonegate) == SSA_NAME && TREE_CODE (negatedef) == MODIFY_EXPR && TREE_CODE (TREE_OPERAND (negatedef, 0)) == SSA_NAME && has_single_use (TREE_OPERAND (negatedef, 0)) && TREE_CODE (TREE_OPERAND (negatedef, 1)) == PLUS_EXPR) { block_stmt_iterator bsi; tree binop = TREE_OPERAND (negatedef, 1); bsi = bsi_for_stmt (negatedef); TREE_OPERAND (binop, 0) = negate_value (TREE_OPERAND (binop, 0), &bsi); bsi = bsi_for_stmt (negatedef); TREE_OPERAND (binop, 1) = negate_value (TREE_OPERAND (binop, 1), &bsi); update_stmt (negatedef); return TREE_OPERAND (negatedef, 0); } tonegate = fold_build1 (NEGATE_EXPR, TREE_TYPE (tonegate), tonegate); resultofnegate = force_gimple_operand_bsi (bsi, tonegate, true, NULL_TREE); VEC_safe_push (tree, heap, broken_up_subtracts, resultofnegate); return resultofnegate; } /* Return true if we should break up the subtract in STMT into an add with negate. This is true when we the subtract operands are really adds, or the subtract itself is used in an add expression. In either case, breaking up the subtract into an add with negate exposes the adds to reassociation. */ static bool should_break_up_subtract (tree stmt) { tree lhs = TREE_OPERAND (stmt, 0); tree rhs = TREE_OPERAND (stmt, 1); tree binlhs = TREE_OPERAND (rhs, 0); tree binrhs = TREE_OPERAND (rhs, 1); tree immusestmt; if (TREE_CODE (binlhs) == SSA_NAME && is_reassociable_op (SSA_NAME_DEF_STMT (binlhs), PLUS_EXPR)) return true; if (TREE_CODE (binrhs) == SSA_NAME && is_reassociable_op (SSA_NAME_DEF_STMT (binrhs), PLUS_EXPR)) return true; if (TREE_CODE (lhs) == SSA_NAME && (immusestmt = get_single_immediate_use (lhs)) && TREE_CODE (TREE_OPERAND (immusestmt, 1)) == PLUS_EXPR) return true; return false; } /* Transform STMT from A - B into A + -B. */ static void break_up_subtract (tree stmt, block_stmt_iterator *bsi) { tree rhs = TREE_OPERAND (stmt, 1); if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Breaking up subtract "); print_generic_stmt (dump_file, stmt, 0); } TREE_SET_CODE (TREE_OPERAND (stmt, 1), PLUS_EXPR); TREE_OPERAND (rhs, 1) = negate_value (TREE_OPERAND (rhs, 1), bsi); update_stmt (stmt); } /* Recursively linearize a binary expression that is the RHS of STMT. Place the operands of the expression tree in the vector named OPS. */ static void linearize_expr_tree (VEC(operand_entry_t, heap) **ops, tree stmt) { block_stmt_iterator bsinow, bsilhs; tree rhs = TREE_OPERAND (stmt, 1); tree binrhs = TREE_OPERAND (rhs, 1); tree binlhs = TREE_OPERAND (rhs, 0); tree binlhsdef, binrhsdef; bool binlhsisreassoc = false; bool binrhsisreassoc = false; enum tree_code rhscode = TREE_CODE (rhs); TREE_VISITED (stmt) = 1; if (TREE_CODE (binlhs) == SSA_NAME) { binlhsdef = SSA_NAME_DEF_STMT (binlhs); binlhsisreassoc = is_reassociable_op (binlhsdef, rhscode); } if (TREE_CODE (binrhs) == SSA_NAME) { binrhsdef = SSA_NAME_DEF_STMT (binrhs); binrhsisreassoc = is_reassociable_op (binrhsdef, rhscode); } /* If the LHS is not reassociable, but the RHS is, we need to swap them. If neither is reassociable, there is nothing we can do, so just put them in the ops vector. If the LHS is reassociable, linearize it. If both are reassociable, then linearize the RHS and the LHS. */ if (!binlhsisreassoc) { tree temp; if (!binrhsisreassoc) { add_to_ops_vec (ops, binrhs); add_to_ops_vec (ops, binlhs); return; } if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "swapping operands of "); print_generic_expr (dump_file, stmt, 0); } swap_tree_operands (stmt, &TREE_OPERAND (rhs, 0), &TREE_OPERAND (rhs, 1)); update_stmt (stmt); if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, " is now "); print_generic_stmt (dump_file, stmt, 0); } /* We want to make it so the lhs is always the reassociative op, so swap. */ temp = binlhs; binlhs = binrhs; binrhs = temp; } else if (binrhsisreassoc) { linearize_expr (stmt); gcc_assert (rhs == TREE_OPERAND (stmt, 1)); binlhs = TREE_OPERAND (rhs, 0); binrhs = TREE_OPERAND (rhs, 1); } gcc_assert (TREE_CODE (binrhs) != SSA_NAME || !is_reassociable_op (SSA_NAME_DEF_STMT (binrhs), rhscode)); bsinow = bsi_for_stmt (stmt); bsilhs = bsi_for_stmt (SSA_NAME_DEF_STMT (binlhs)); bsi_move_before (&bsilhs, &bsinow); linearize_expr_tree (ops, SSA_NAME_DEF_STMT (binlhs)); add_to_ops_vec (ops, binrhs); } /* Repropagate the negates back into subtracts, since no other pass currently does it. */ static void repropagate_negates (void) { unsigned int i = 0; tree negate; for (i = 0; VEC_iterate (tree, broken_up_subtracts, i, negate); i++) { tree user = get_single_immediate_use (negate); /* The negate operand can be either operand of a PLUS_EXPR (it can be the LHS if the RHS is a constant for example). Force the negate operand to the RHS of the PLUS_EXPR, then transform the PLUS_EXPR into a MINUS_EXPR. */ if (user && TREE_CODE (user) == MODIFY_EXPR && TREE_CODE (TREE_OPERAND (user, 1)) == PLUS_EXPR) { tree rhs = TREE_OPERAND (user, 1); /* If the negated operand appears on the LHS of the PLUS_EXPR, exchange the operands of the PLUS_EXPR to force the negated operand to the RHS of the PLUS_EXPR. */ if (TREE_OPERAND (TREE_OPERAND (user, 1), 0) == negate) { tree temp = TREE_OPERAND (rhs, 0); TREE_OPERAND (rhs, 0) = TREE_OPERAND (rhs, 1); TREE_OPERAND (rhs, 1) = temp; } /* Now transform the PLUS_EXPR into a MINUS_EXPR and replace the RHS of the PLUS_EXPR with the operand of the NEGATE_EXPR. */ if (TREE_OPERAND (TREE_OPERAND (user, 1), 1) == negate) { TREE_SET_CODE (rhs, MINUS_EXPR); TREE_OPERAND (rhs, 1) = get_unary_op (negate, NEGATE_EXPR); update_stmt (user); } } } } /* Break up subtract operations in block BB. We do this top down because we don't know whether the subtract is part of a possible chain of reassociation except at the top. IE given d = f + g c = a + e b = c - d q = b - r k = t - q we want to break up k = t - q, but we won't until we've transformed q = b - r, which won't be broken up until we transform b = c - d. */ static void break_up_subtract_bb (basic_block bb) { block_stmt_iterator bsi; basic_block son; for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) { tree stmt = bsi_stmt (bsi); if (TREE_CODE (stmt) == MODIFY_EXPR) { tree lhs = TREE_OPERAND (stmt, 0); tree rhs = TREE_OPERAND (stmt, 1); TREE_VISITED (stmt) = 0; /* If unsafe math optimizations we can do reassociation for non-integral types. */ if ((!INTEGRAL_TYPE_P (TREE_TYPE (lhs)) || !INTEGRAL_TYPE_P (TREE_TYPE (rhs))) && (!SCALAR_FLOAT_TYPE_P (TREE_TYPE (rhs)) || !SCALAR_FLOAT_TYPE_P (TREE_TYPE(lhs)) || !flag_unsafe_math_optimizations)) continue; /* Check for a subtract used only in an addition. If this is the case, transform it into add of a negate for better reassociation. IE transform C = A-B into C = A + -B if C is only used in an addition. */ if (TREE_CODE (rhs) == MINUS_EXPR) if (should_break_up_subtract (stmt)) break_up_subtract (stmt, &bsi); } } for (son = first_dom_son (CDI_DOMINATORS, bb); son; son = next_dom_son (CDI_DOMINATORS, son)) break_up_subtract_bb (son); } /* Reassociate expressions in basic block BB and its post-dominator as children. */ static void reassociate_bb (basic_block bb) { block_stmt_iterator bsi; basic_block son; for (bsi = bsi_last (bb); !bsi_end_p (bsi); bsi_prev (&bsi)) { tree stmt = bsi_stmt (bsi); if (TREE_CODE (stmt) == MODIFY_EXPR) { tree lhs = TREE_OPERAND (stmt, 0); tree rhs = TREE_OPERAND (stmt, 1); /* If this was part of an already processed tree, we don't need to touch it again. */ if (TREE_VISITED (stmt)) continue; /* If unsafe math optimizations we can do reassociation for non-integral types. */ if ((!INTEGRAL_TYPE_P (TREE_TYPE (lhs)) || !INTEGRAL_TYPE_P (TREE_TYPE (rhs))) && (!SCALAR_FLOAT_TYPE_P (TREE_TYPE (rhs)) || !SCALAR_FLOAT_TYPE_P (TREE_TYPE(lhs)) || !flag_unsafe_math_optimizations)) continue; if (associative_tree_code (TREE_CODE (rhs))) { VEC(operand_entry_t, heap) *ops = NULL; /* There may be no immediate uses left by the time we get here because we may have eliminated them all. */ if (TREE_CODE (lhs) == SSA_NAME && has_zero_uses (lhs)) continue; TREE_VISITED (stmt) = 1; linearize_expr_tree (&ops, stmt); qsort (VEC_address (operand_entry_t, ops), VEC_length (operand_entry_t, ops), sizeof (operand_entry_t), sort_by_operand_rank); optimize_ops_list (TREE_CODE (rhs), &ops); if (VEC_length (operand_entry_t, ops) == 1) { if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Transforming "); print_generic_expr (dump_file, rhs, 0); } TREE_OPERAND (stmt, 1) = VEC_last (operand_entry_t, ops)->op; update_stmt (stmt); if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, " into "); print_generic_stmt (dump_file, TREE_OPERAND (stmt, 1), 0); } } else { rewrite_expr_tree (stmt, 0, ops); } VEC_free (operand_entry_t, heap, ops); } } } for (son = first_dom_son (CDI_POST_DOMINATORS, bb); son; son = next_dom_son (CDI_POST_DOMINATORS, son)) reassociate_bb (son); } void dump_ops_vector (FILE *file, VEC (operand_entry_t, heap) *ops); void debug_ops_vector (VEC (operand_entry_t, heap) *ops); /* Dump the operand entry vector OPS to FILE. */ void dump_ops_vector (FILE *file, VEC (operand_entry_t, heap) *ops) { operand_entry_t oe; unsigned int i; for (i = 0; VEC_iterate (operand_entry_t, ops, i, oe); i++) { fprintf (file, "Op %d -> rank: %d, tree: ", i, oe->rank); print_generic_stmt (file, oe->op, 0); } } /* Dump the operand entry vector OPS to STDERR. */ void debug_ops_vector (VEC (operand_entry_t, heap) *ops) { dump_ops_vector (stderr, ops); } static void do_reassoc (void) { break_up_subtract_bb (ENTRY_BLOCK_PTR); reassociate_bb (EXIT_BLOCK_PTR); } /* Initialize the reassociation pass. */ static void init_reassoc (void) { int i; unsigned int rank = 2; tree param; int *bbs = XNEWVEC (int, last_basic_block + 1); memset (&reassociate_stats, 0, sizeof (reassociate_stats)); operand_entry_pool = create_alloc_pool ("operand entry pool", sizeof (struct operand_entry), 30); /* Reverse RPO (Reverse Post Order) will give us something where deeper loops come later. */ pre_and_rev_post_order_compute (NULL, bbs, false); bb_rank = XCNEWVEC (unsigned int, last_basic_block + 1); operand_rank = htab_create (511, operand_entry_hash, operand_entry_eq, 0); /* Give each argument a distinct rank. */ for (param = DECL_ARGUMENTS (current_function_decl); param; param = TREE_CHAIN (param)) { if (default_def (param) != NULL) { tree def = default_def (param); insert_operand_rank (def, ++rank); } } /* Give the chain decl a distinct rank. */ if (cfun->static_chain_decl != NULL) { tree def = default_def (cfun->static_chain_decl); if (def != NULL) insert_operand_rank (def, ++rank); } /* Set up rank for each BB */ for (i = 0; i < n_basic_blocks - NUM_FIXED_BLOCKS; i++) bb_rank[bbs[i]] = ++rank << 16; free (bbs); calculate_dominance_info (CDI_DOMINATORS); calculate_dominance_info (CDI_POST_DOMINATORS); broken_up_subtracts = NULL; } /* Cleanup after the reassociation pass, and print stats if requested. */ static void fini_reassoc (void) { if (dump_file && (dump_flags & TDF_STATS)) { fprintf (dump_file, "Reassociation stats:\n"); fprintf (dump_file, "Linearized: %d\n", reassociate_stats.linearized); fprintf (dump_file, "Constants eliminated: %d\n", reassociate_stats.constants_eliminated); fprintf (dump_file, "Ops eliminated: %d\n", reassociate_stats.ops_eliminated); fprintf (dump_file, "Statements rewritten: %d\n", reassociate_stats.rewritten); } htab_delete (operand_rank); free_alloc_pool (operand_entry_pool); free (bb_rank); VEC_free (tree, heap, broken_up_subtracts); free_dominance_info (CDI_POST_DOMINATORS); } /* Gate and execute functions for Reassociation. */ static unsigned int execute_reassoc (void) { init_reassoc (); do_reassoc (); repropagate_negates (); fini_reassoc (); return 0; } struct tree_opt_pass pass_reassoc = { "reassoc", /* name */ NULL, /* gate */ execute_reassoc, /* execute */ NULL, /* sub */ NULL, /* next */ 0, /* static_pass_number */ TV_TREE_REASSOC, /* tv_id */ PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */ 0, /* properties_provided */ 0, /* properties_destroyed */ 0, /* todo_flags_start */ TODO_dump_func | TODO_ggc_collect | TODO_verify_ssa, /* todo_flags_finish */ 0 /* letter */ };
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