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/* Calculate (post)dominators in slightly super-linear time. Copyright (C) 2000, 2003, 2004, 2005, 2007 Free Software Foundation, Inc. Contributed by Michael Matz (matz@ifh.de). 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/>. */ /* This file implements the well known algorithm from Lengauer and Tarjan to compute the dominators in a control flow graph. A basic block D is said to dominate another block X, when all paths from the entry node of the CFG to X go also over D. The dominance relation is a transitive reflexive relation and its minimal transitive reduction is a tree, called the dominator tree. So for each block X besides the entry block exists a block I(X), called the immediate dominator of X, which is the parent of X in the dominator tree. The algorithm computes this dominator tree implicitly by computing for each block its immediate dominator. We use tree balancing and path compression, so it's the O(e*a(e,v)) variant, where a(e,v) is the very slowly growing functional inverse of the Ackerman function. */ #include "config.h" #include "system.h" #include "coretypes.h" #include "tm.h" #include "rtl.h" #include "hard-reg-set.h" #include "obstack.h" #include "basic-block.h" #include "toplev.h" #include "et-forest.h" #include "timevar.h" /* Whether the dominators and the postdominators are available. */ enum dom_state dom_computed[2]; /* We name our nodes with integers, beginning with 1. Zero is reserved for 'undefined' or 'end of list'. The name of each node is given by the dfs number of the corresponding basic block. Please note, that we include the artificial ENTRY_BLOCK (or EXIT_BLOCK in the post-dom case) in our lists to support multiple entry points. Its dfs number is of course 1. */ /* Type of Basic Block aka. TBB */ typedef unsigned int TBB; /* We work in a poor-mans object oriented fashion, and carry an instance of this structure through all our 'methods'. It holds various arrays reflecting the (sub)structure of the flowgraph. Most of them are of type TBB and are also indexed by TBB. */ struct dom_info { /* The parent of a node in the DFS tree. */ TBB *dfs_parent; /* For a node x key[x] is roughly the node nearest to the root from which exists a way to x only over nodes behind x. Such a node is also called semidominator. */ TBB *key; /* The value in path_min[x] is the node y on the path from x to the root of the tree x is in with the smallest key[y]. */ TBB *path_min; /* bucket[x] points to the first node of the set of nodes having x as key. */ TBB *bucket; /* And next_bucket[x] points to the next node. */ TBB *next_bucket; /* After the algorithm is done, dom[x] contains the immediate dominator of x. */ TBB *dom; /* The following few fields implement the structures needed for disjoint sets. */ /* set_chain[x] is the next node on the path from x to the representant of the set containing x. If set_chain[x]==0 then x is a root. */ TBB *set_chain; /* set_size[x] is the number of elements in the set named by x. */ unsigned int *set_size; /* set_child[x] is used for balancing the tree representing a set. It can be understood as the next sibling of x. */ TBB *set_child; /* If b is the number of a basic block (BB->index), dfs_order[b] is the number of that node in DFS order counted from 1. This is an index into most of the other arrays in this structure. */ TBB *dfs_order; /* If x is the DFS-index of a node which corresponds with a basic block, dfs_to_bb[x] is that basic block. Note, that in our structure there are more nodes that basic blocks, so only dfs_to_bb[dfs_order[bb->index]]==bb is true for every basic block bb, but not the opposite. */ basic_block *dfs_to_bb; /* This is the next free DFS number when creating the DFS tree. */ unsigned int dfsnum; /* The number of nodes in the DFS tree (==dfsnum-1). */ unsigned int nodes; /* Blocks with bits set here have a fake edge to EXIT. These are used to turn a DFS forest into a proper tree. */ bitmap fake_exit_edge; }; static void init_dom_info (struct dom_info *, enum cdi_direction); static void free_dom_info (struct dom_info *); static void calc_dfs_tree_nonrec (struct dom_info *, basic_block, enum cdi_direction); static void calc_dfs_tree (struct dom_info *, enum cdi_direction); static void compress (struct dom_info *, TBB); static TBB eval (struct dom_info *, TBB); static void link_roots (struct dom_info *, TBB, TBB); static void calc_idoms (struct dom_info *, enum cdi_direction); void debug_dominance_info (enum cdi_direction); /* Keeps track of the*/ static unsigned n_bbs_in_dom_tree[2]; /* Helper macro for allocating and initializing an array, for aesthetic reasons. */ #define init_ar(var, type, num, content) \ do \ { \ unsigned int i = 1; /* Catch content == i. */ \ if (! (content)) \ (var) = XCNEWVEC (type, num); \ else \ { \ (var) = XNEWVEC (type, (num)); \ for (i = 0; i < num; i++) \ (var)[i] = (content); \ } \ } \ while (0) /* Allocate all needed memory in a pessimistic fashion (so we round up). This initializes the contents of DI, which already must be allocated. */ static void init_dom_info (struct dom_info *di, enum cdi_direction dir) { unsigned int num = n_basic_blocks; init_ar (di->dfs_parent, TBB, num, 0); init_ar (di->path_min, TBB, num, i); init_ar (di->key, TBB, num, i); init_ar (di->dom, TBB, num, 0); init_ar (di->bucket, TBB, num, 0); init_ar (di->next_bucket, TBB, num, 0); init_ar (di->set_chain, TBB, num, 0); init_ar (di->set_size, unsigned int, num, 1); init_ar (di->set_child, TBB, num, 0); init_ar (di->dfs_order, TBB, (unsigned int) last_basic_block + 1, 0); init_ar (di->dfs_to_bb, basic_block, num, 0); di->dfsnum = 1; di->nodes = 0; di->fake_exit_edge = dir ? BITMAP_ALLOC (NULL) : NULL; } #undef init_ar /* Free all allocated memory in DI, but not DI itself. */ static void free_dom_info (struct dom_info *di) { free (di->dfs_parent); free (di->path_min); free (di->key); free (di->dom); free (di->bucket); free (di->next_bucket); free (di->set_chain); free (di->set_size); free (di->set_child); free (di->dfs_order); free (di->dfs_to_bb); BITMAP_FREE (di->fake_exit_edge); } /* The nonrecursive variant of creating a DFS tree. DI is our working structure, BB the starting basic block for this tree and REVERSE is true, if predecessors should be visited instead of successors of a node. After this is done all nodes reachable from BB were visited, have assigned their dfs number and are linked together to form a tree. */ static void calc_dfs_tree_nonrec (struct dom_info *di, basic_block bb, enum cdi_direction reverse) { /* We call this _only_ if bb is not already visited. */ edge e; TBB child_i, my_i = 0; edge_iterator *stack; edge_iterator ei, einext; int sp; /* Start block (ENTRY_BLOCK_PTR for forward problem, EXIT_BLOCK for backward problem). */ basic_block en_block; /* Ending block. */ basic_block ex_block; stack = XNEWVEC (edge_iterator, n_basic_blocks + 1); sp = 0; /* Initialize our border blocks, and the first edge. */ if (reverse) { ei = ei_start (bb->preds); en_block = EXIT_BLOCK_PTR; ex_block = ENTRY_BLOCK_PTR; } else { ei = ei_start (bb->succs); en_block = ENTRY_BLOCK_PTR; ex_block = EXIT_BLOCK_PTR; } /* When the stack is empty we break out of this loop. */ while (1) { basic_block bn; /* This loop traverses edges e in depth first manner, and fills the stack. */ while (!ei_end_p (ei)) { e = ei_edge (ei); /* Deduce from E the current and the next block (BB and BN), and the next edge. */ if (reverse) { bn = e->src; /* If the next node BN is either already visited or a border block the current edge is useless, and simply overwritten with the next edge out of the current node. */ if (bn == ex_block || di->dfs_order[bn->index]) { ei_next (&ei); continue; } bb = e->dest; einext = ei_start (bn->preds); } else { bn = e->dest; if (bn == ex_block || di->dfs_order[bn->index]) { ei_next (&ei); continue; } bb = e->src; einext = ei_start (bn->succs); } gcc_assert (bn != en_block); /* Fill the DFS tree info calculatable _before_ recursing. */ if (bb != en_block) my_i = di->dfs_order[bb->index]; else my_i = di->dfs_order[last_basic_block]; child_i = di->dfs_order[bn->index] = di->dfsnum++; di->dfs_to_bb[child_i] = bn; di->dfs_parent[child_i] = my_i; /* Save the current point in the CFG on the stack, and recurse. */ stack[sp++] = ei; ei = einext; } if (!sp) break; ei = stack[--sp]; /* OK. The edge-list was exhausted, meaning normally we would end the recursion. After returning from the recursive call, there were (may be) other statements which were run after a child node was completely considered by DFS. Here is the point to do it in the non-recursive variant. E.g. The block just completed is in e->dest for forward DFS, the block not yet completed (the parent of the one above) in e->src. This could be used e.g. for computing the number of descendants or the tree depth. */ ei_next (&ei); } free (stack); } /* The main entry for calculating the DFS tree or forest. DI is our working structure and REVERSE is true, if we are interested in the reverse flow graph. In that case the result is not necessarily a tree but a forest, because there may be nodes from which the EXIT_BLOCK is unreachable. */ static void calc_dfs_tree (struct dom_info *di, enum cdi_direction reverse) { /* The first block is the ENTRY_BLOCK (or EXIT_BLOCK if REVERSE). */ basic_block begin = reverse ? EXIT_BLOCK_PTR : ENTRY_BLOCK_PTR; di->dfs_order[last_basic_block] = di->dfsnum; di->dfs_to_bb[di->dfsnum] = begin; di->dfsnum++; calc_dfs_tree_nonrec (di, begin, reverse); if (reverse) { /* In the post-dom case we may have nodes without a path to EXIT_BLOCK. They are reverse-unreachable. In the dom-case we disallow such nodes, but in post-dom we have to deal with them. There are two situations in which this occurs. First, noreturn functions. Second, infinite loops. In the first case we need to pretend that there is an edge to the exit block. In the second case, we wind up with a forest. We need to process all noreturn blocks before we know if we've got any infinite loops. */ basic_block b; bool saw_unconnected = false; FOR_EACH_BB_REVERSE (b) { if (EDGE_COUNT (b->succs) > 0) { if (di->dfs_order[b->index] == 0) saw_unconnected = true; continue; } bitmap_set_bit (di->fake_exit_edge, b->index); di->dfs_order[b->index] = di->dfsnum; di->dfs_to_bb[di->dfsnum] = b; di->dfs_parent[di->dfsnum] = di->dfs_order[last_basic_block]; di->dfsnum++; calc_dfs_tree_nonrec (di, b, reverse); } if (saw_unconnected) { FOR_EACH_BB_REVERSE (b) { if (di->dfs_order[b->index]) continue; bitmap_set_bit (di->fake_exit_edge, b->index); di->dfs_order[b->index] = di->dfsnum; di->dfs_to_bb[di->dfsnum] = b; di->dfs_parent[di->dfsnum] = di->dfs_order[last_basic_block]; di->dfsnum++; calc_dfs_tree_nonrec (di, b, reverse); } } } di->nodes = di->dfsnum - 1; /* This aborts e.g. when there is _no_ path from ENTRY to EXIT at all. */ gcc_assert (di->nodes == (unsigned int) n_basic_blocks - 1); } /* Compress the path from V to the root of its set and update path_min at the same time. After compress(di, V) set_chain[V] is the root of the set V is in and path_min[V] is the node with the smallest key[] value on the path from V to that root. */ static void compress (struct dom_info *di, TBB v) { /* Btw. It's not worth to unrecurse compress() as the depth is usually not greater than 5 even for huge graphs (I've not seen call depth > 4). Also performance wise compress() ranges _far_ behind eval(). */ TBB parent = di->set_chain[v]; if (di->set_chain[parent]) { compress (di, parent); if (di->key[di->path_min[parent]] < di->key[di->path_min[v]]) di->path_min[v] = di->path_min[parent]; di->set_chain[v] = di->set_chain[parent]; } } /* Compress the path from V to the set root of V if needed (when the root has changed since the last call). Returns the node with the smallest key[] value on the path from V to the root. */ static inline TBB eval (struct dom_info *di, TBB v) { /* The representant of the set V is in, also called root (as the set representation is a tree). */ TBB rep = di->set_chain[v]; /* V itself is the root. */ if (!rep) return di->path_min[v]; /* Compress only if necessary. */ if (di->set_chain[rep]) { compress (di, v); rep = di->set_chain[v]; } if (di->key[di->path_min[rep]] >= di->key[di->path_min[v]]) return di->path_min[v]; else return di->path_min[rep]; } /* This essentially merges the two sets of V and W, giving a single set with the new root V. The internal representation of these disjoint sets is a balanced tree. Currently link(V,W) is only used with V being the parent of W. */ static void link_roots (struct dom_info *di, TBB v, TBB w) { TBB s = w; /* Rebalance the tree. */ while (di->key[di->path_min[w]] < di->key[di->path_min[di->set_child[s]]]) { if (di->set_size[s] + di->set_size[di->set_child[di->set_child[s]]] >= 2 * di->set_size[di->set_child[s]]) { di->set_chain[di->set_child[s]] = s; di->set_child[s] = di->set_child[di->set_child[s]]; } else { di->set_size[di->set_child[s]] = di->set_size[s]; s = di->set_chain[s] = di->set_child[s]; } } di->path_min[s] = di->path_min[w]; di->set_size[v] += di->set_size[w]; if (di->set_size[v] < 2 * di->set_size[w]) { TBB tmp = s; s = di->set_child[v]; di->set_child[v] = tmp; } /* Merge all subtrees. */ while (s) { di->set_chain[s] = v; s = di->set_child[s]; } } /* This calculates the immediate dominators (or post-dominators if REVERSE is true). DI is our working structure and should hold the DFS forest. On return the immediate dominator to node V is in di->dom[V]. */ static void calc_idoms (struct dom_info *di, enum cdi_direction reverse) { TBB v, w, k, par; basic_block en_block; edge_iterator ei, einext; if (reverse) en_block = EXIT_BLOCK_PTR; else en_block = ENTRY_BLOCK_PTR; /* Go backwards in DFS order, to first look at the leafs. */ v = di->nodes; while (v > 1) { basic_block bb = di->dfs_to_bb[v]; edge e; par = di->dfs_parent[v]; k = v; ei = (reverse) ? ei_start (bb->succs) : ei_start (bb->preds); if (reverse) { /* If this block has a fake edge to exit, process that first. */ if (bitmap_bit_p (di->fake_exit_edge, bb->index)) { einext = ei; einext.index = 0; goto do_fake_exit_edge; } } /* Search all direct predecessors for the smallest node with a path to them. That way we have the smallest node with also a path to us only over nodes behind us. In effect we search for our semidominator. */ while (!ei_end_p (ei)) { TBB k1; basic_block b; e = ei_edge (ei); b = (reverse) ? e->dest : e->src; einext = ei; ei_next (&einext); if (b == en_block) { do_fake_exit_edge: k1 = di->dfs_order[last_basic_block]; } else k1 = di->dfs_order[b->index]; /* Call eval() only if really needed. If k1 is above V in DFS tree, then we know, that eval(k1) == k1 and key[k1] == k1. */ if (k1 > v) k1 = di->key[eval (di, k1)]; if (k1 < k) k = k1; ei = einext; } di->key[v] = k; link_roots (di, par, v); di->next_bucket[v] = di->bucket[k]; di->bucket[k] = v; /* Transform semidominators into dominators. */ for (w = di->bucket[par]; w; w = di->next_bucket[w]) { k = eval (di, w); if (di->key[k] < di->key[w]) di->dom[w] = k; else di->dom[w] = par; } /* We don't need to cleanup next_bucket[]. */ di->bucket[par] = 0; v--; } /* Explicitly define the dominators. */ di->dom[1] = 0; for (v = 2; v <= di->nodes; v++) if (di->dom[v] != di->key[v]) di->dom[v] = di->dom[di->dom[v]]; } /* Assign dfs numbers starting from NUM to NODE and its sons. */ static void assign_dfs_numbers (struct et_node *node, int *num) { struct et_node *son; node->dfs_num_in = (*num)++; if (node->son) { assign_dfs_numbers (node->son, num); for (son = node->son->right; son != node->son; son = son->right) assign_dfs_numbers (son, num); } node->dfs_num_out = (*num)++; } /* Compute the data necessary for fast resolving of dominator queries in a static dominator tree. */ static void compute_dom_fast_query (enum cdi_direction dir) { int num = 0; basic_block bb; gcc_assert (dom_info_available_p (dir)); if (dom_computed[dir] == DOM_OK) return; FOR_ALL_BB (bb) { if (!bb->dom[dir]->father) assign_dfs_numbers (bb->dom[dir], &num); } dom_computed[dir] = DOM_OK; } /* The main entry point into this module. DIR is set depending on whether we want to compute dominators or postdominators. */ void calculate_dominance_info (enum cdi_direction dir) { struct dom_info di; basic_block b; if (dom_computed[dir] == DOM_OK) return; timevar_push (TV_DOMINANCE); if (!dom_info_available_p (dir)) { gcc_assert (!n_bbs_in_dom_tree[dir]); FOR_ALL_BB (b) { b->dom[dir] = et_new_tree (b); } n_bbs_in_dom_tree[dir] = n_basic_blocks; init_dom_info (&di, dir); calc_dfs_tree (&di, dir); calc_idoms (&di, dir); FOR_EACH_BB (b) { TBB d = di.dom[di.dfs_order[b->index]]; if (di.dfs_to_bb[d]) et_set_father (b->dom[dir], di.dfs_to_bb[d]->dom[dir]); } free_dom_info (&di); dom_computed[dir] = DOM_NO_FAST_QUERY; } compute_dom_fast_query (dir); timevar_pop (TV_DOMINANCE); } /* Free dominance information for direction DIR. */ void free_dominance_info (enum cdi_direction dir) { basic_block bb; if (!dom_info_available_p (dir)) return; FOR_ALL_BB (bb) { et_free_tree_force (bb->dom[dir]); bb->dom[dir] = NULL; } et_free_pools (); n_bbs_in_dom_tree[dir] = 0; dom_computed[dir] = DOM_NONE; } /* Return the immediate dominator of basic block BB. */ basic_block get_immediate_dominator (enum cdi_direction dir, basic_block bb) { struct et_node *node = bb->dom[dir]; gcc_assert (dom_computed[dir]); if (!node->father) return NULL; return node->father->data; } /* Set the immediate dominator of the block possibly removing existing edge. NULL can be used to remove any edge. */ inline void set_immediate_dominator (enum cdi_direction dir, basic_block bb, basic_block dominated_by) { struct et_node *node = bb->dom[dir]; gcc_assert (dom_computed[dir]); if (node->father) { if (node->father->data == dominated_by) return; et_split (node); } if (dominated_by) et_set_father (node, dominated_by->dom[dir]); if (dom_computed[dir] == DOM_OK) dom_computed[dir] = DOM_NO_FAST_QUERY; } /* Store all basic blocks immediately dominated by BB into BBS and return their number. */ int get_dominated_by (enum cdi_direction dir, basic_block bb, basic_block **bbs) { int n; struct et_node *node = bb->dom[dir], *son = node->son, *ason; gcc_assert (dom_computed[dir]); if (!son) { *bbs = NULL; return 0; } for (ason = son->right, n = 1; ason != son; ason = ason->right) n++; *bbs = XNEWVEC (basic_block, n); (*bbs)[0] = son->data; for (ason = son->right, n = 1; ason != son; ason = ason->right) (*bbs)[n++] = ason->data; return n; } /* Find all basic blocks that are immediately dominated (in direction DIR) by some block between N_REGION ones stored in REGION, except for blocks in the REGION itself. The found blocks are stored to DOMS and their number is returned. */ unsigned get_dominated_by_region (enum cdi_direction dir, basic_block *region, unsigned n_region, basic_block *doms) { unsigned n_doms = 0, i; basic_block dom; for (i = 0; i < n_region; i++) region[i]->flags |= BB_DUPLICATED; for (i = 0; i < n_region; i++) for (dom = first_dom_son (dir, region[i]); dom; dom = next_dom_son (dir, dom)) if (!(dom->flags & BB_DUPLICATED)) doms[n_doms++] = dom; for (i = 0; i < n_region; i++) region[i]->flags &= ~BB_DUPLICATED; return n_doms; } /* Redirect all edges pointing to BB to TO. */ void redirect_immediate_dominators (enum cdi_direction dir, basic_block bb, basic_block to) { struct et_node *bb_node = bb->dom[dir], *to_node = to->dom[dir], *son; gcc_assert (dom_computed[dir]); if (!bb_node->son) return; while (bb_node->son) { son = bb_node->son; et_split (son); et_set_father (son, to_node); } if (dom_computed[dir] == DOM_OK) dom_computed[dir] = DOM_NO_FAST_QUERY; } /* Find first basic block in the tree dominating both BB1 and BB2. */ basic_block nearest_common_dominator (enum cdi_direction dir, basic_block bb1, basic_block bb2) { gcc_assert (dom_computed[dir]); if (!bb1) return bb2; if (!bb2) return bb1; return et_nca (bb1->dom[dir], bb2->dom[dir])->data; } /* Find the nearest common dominator for the basic blocks in BLOCKS, using dominance direction DIR. */ basic_block nearest_common_dominator_for_set (enum cdi_direction dir, bitmap blocks) { unsigned i, first; bitmap_iterator bi; basic_block dom; first = bitmap_first_set_bit (blocks); dom = BASIC_BLOCK (first); EXECUTE_IF_SET_IN_BITMAP (blocks, 0, i, bi) if (dom != BASIC_BLOCK (i)) dom = nearest_common_dominator (dir, dom, BASIC_BLOCK (i)); return dom; } /* Given a dominator tree, we can determine whether one thing dominates another in constant time by using two DFS numbers: 1. The number for when we visit a node on the way down the tree 2. The number for when we visit a node on the way back up the tree You can view these as bounds for the range of dfs numbers the nodes in the subtree of the dominator tree rooted at that node will contain. The dominator tree is always a simple acyclic tree, so there are only three possible relations two nodes in the dominator tree have to each other: 1. Node A is above Node B (and thus, Node A dominates node B) A | C / \ B D In the above case, DFS_Number_In of A will be <= DFS_Number_In of B, and DFS_Number_Out of A will be >= DFS_Number_Out of B. This is because we must hit A in the dominator tree *before* B on the walk down, and we will hit A *after* B on the walk back up 2. Node A is below node B (and thus, node B dominates node A) B | A / \ C D In the above case, DFS_Number_In of A will be >= DFS_Number_In of B, and DFS_Number_Out of A will be <= DFS_Number_Out of B. This is because we must hit A in the dominator tree *after* B on the walk down, and we will hit A *before* B on the walk back up 3. Node A and B are siblings (and thus, neither dominates the other) C | D / \ A B In the above case, DFS_Number_In of A will *always* be <= DFS_Number_In of B, and DFS_Number_Out of A will *always* be <= DFS_Number_Out of B. This is because we will always finish the dfs walk of one of the subtrees before the other, and thus, the dfs numbers for one subtree can't intersect with the range of dfs numbers for the other subtree. If you swap A and B's position in the dominator tree, the comparison changes direction, but the point is that both comparisons will always go the same way if there is no dominance relationship. Thus, it is sufficient to write A_Dominates_B (node A, node B) { return DFS_Number_In(A) <= DFS_Number_In(B) && DFS_Number_Out (A) >= DFS_Number_Out(B); } A_Dominated_by_B (node A, node B) { return DFS_Number_In(A) >= DFS_Number_In(A) && DFS_Number_Out (A) <= DFS_Number_Out(B); } */ /* Return TRUE in case BB1 is dominated by BB2. */ bool dominated_by_p (enum cdi_direction dir, basic_block bb1, basic_block bb2) { struct et_node *n1 = bb1->dom[dir], *n2 = bb2->dom[dir]; gcc_assert (dom_computed[dir]); if (dom_computed[dir] == DOM_OK) return (n1->dfs_num_in >= n2->dfs_num_in && n1->dfs_num_out <= n2->dfs_num_out); return et_below (n1, n2); } /* Returns the entry dfs number for basic block BB, in the direction DIR. */ unsigned bb_dom_dfs_in (enum cdi_direction dir, basic_block bb) { struct et_node *n = bb->dom[dir]; gcc_assert (dom_computed[dir] == DOM_OK); return n->dfs_num_in; } /* Returns the exit dfs number for basic block BB, in the direction DIR. */ unsigned bb_dom_dfs_out (enum cdi_direction dir, basic_block bb) { struct et_node *n = bb->dom[dir]; gcc_assert (dom_computed[dir] == DOM_OK); return n->dfs_num_out; } /* Verify invariants of dominator structure. */ void verify_dominators (enum cdi_direction dir) { int err = 0; basic_block bb; gcc_assert (dom_info_available_p (dir)); FOR_EACH_BB (bb) { basic_block dom_bb; basic_block imm_bb; dom_bb = recount_dominator (dir, bb); imm_bb = get_immediate_dominator (dir, bb); if (dom_bb != imm_bb) { if ((dom_bb == NULL) || (imm_bb == NULL)) error ("dominator of %d status unknown", bb->index); else error ("dominator of %d should be %d, not %d", bb->index, dom_bb->index, imm_bb->index); err = 1; } } if (dir == CDI_DOMINATORS) { FOR_EACH_BB (bb) { if (!dominated_by_p (dir, bb, ENTRY_BLOCK_PTR)) { error ("ENTRY does not dominate bb %d", bb->index); err = 1; } } } gcc_assert (!err); } /* Determine immediate dominator (or postdominator, according to DIR) of BB, assuming that dominators of other blocks are correct. We also use it to recompute the dominators in a restricted area, by iterating it until it reaches a fixed point. */ basic_block recount_dominator (enum cdi_direction dir, basic_block bb) { basic_block dom_bb = NULL; edge e; edge_iterator ei; gcc_assert (dom_computed[dir]); if (dir == CDI_DOMINATORS) { FOR_EACH_EDGE (e, ei, bb->preds) { /* Ignore the predecessors that either are not reachable from the entry block, or whose dominator was not determined yet. */ if (!dominated_by_p (dir, e->src, ENTRY_BLOCK_PTR)) continue; if (!dominated_by_p (dir, e->src, bb)) dom_bb = nearest_common_dominator (dir, dom_bb, e->src); } } else { FOR_EACH_EDGE (e, ei, bb->succs) { if (!dominated_by_p (dir, e->dest, bb)) dom_bb = nearest_common_dominator (dir, dom_bb, e->dest); } } return dom_bb; } /* Iteratively recount dominators of BBS. The change is supposed to be local and not to grow further. */ void iterate_fix_dominators (enum cdi_direction dir, basic_block *bbs, int n) { int i, changed = 1; basic_block old_dom, new_dom; gcc_assert (dom_computed[dir]); for (i = 0; i < n; i++) set_immediate_dominator (dir, bbs[i], NULL); while (changed) { changed = 0; for (i = 0; i < n; i++) { old_dom = get_immediate_dominator (dir, bbs[i]); new_dom = recount_dominator (dir, bbs[i]); if (old_dom != new_dom) { changed = 1; set_immediate_dominator (dir, bbs[i], new_dom); } } } for (i = 0; i < n; i++) gcc_assert (get_immediate_dominator (dir, bbs[i])); } void add_to_dominance_info (enum cdi_direction dir, basic_block bb) { gcc_assert (dom_computed[dir]); gcc_assert (!bb->dom[dir]); n_bbs_in_dom_tree[dir]++; bb->dom[dir] = et_new_tree (bb); if (dom_computed[dir] == DOM_OK) dom_computed[dir] = DOM_NO_FAST_QUERY; } void delete_from_dominance_info (enum cdi_direction dir, basic_block bb) { gcc_assert (dom_computed[dir]); et_free_tree (bb->dom[dir]); bb->dom[dir] = NULL; n_bbs_in_dom_tree[dir]--; if (dom_computed[dir] == DOM_OK) dom_computed[dir] = DOM_NO_FAST_QUERY; } /* Returns the first son of BB in the dominator or postdominator tree as determined by DIR. */ basic_block first_dom_son (enum cdi_direction dir, basic_block bb) { struct et_node *son = bb->dom[dir]->son; return son ? son->data : NULL; } /* Returns the next dominance son after BB in the dominator or postdominator tree as determined by DIR, or NULL if it was the last one. */ basic_block next_dom_son (enum cdi_direction dir, basic_block bb) { struct et_node *next = bb->dom[dir]->right; return next->father->son == next ? NULL : next->data; } /* Returns true if dominance information for direction DIR is available. */ bool dom_info_available_p (enum cdi_direction dir) { return dom_computed[dir] != DOM_NONE; } void debug_dominance_info (enum cdi_direction dir) { basic_block bb, bb2; FOR_EACH_BB (bb) if ((bb2 = get_immediate_dominator (dir, bb))) fprintf (stderr, "%i %i\n", bb->index, bb2->index); }
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