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Diffstat (limited to 'gcc-4.2.1-5666.3/gcc/dominance.c')
| -rw-r--r-- | gcc-4.2.1-5666.3/gcc/dominance.c | 1111 |
1 files changed, 0 insertions, 1111 deletions
diff --git a/gcc-4.2.1-5666.3/gcc/dominance.c b/gcc-4.2.1-5666.3/gcc/dominance.c deleted file mode 100644 index 819e7d450..000000000 --- a/gcc-4.2.1-5666.3/gcc/dominance.c +++ /dev/null @@ -1,1111 +0,0 @@ -/* Calculate (post)dominators in slightly super-linear time. - Copyright (C) 2000, 2003, 2004, 2005 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 2, or (at your option) - any later version. - - GCC is distributed in the hope that it will be useful, but WITHOUT - ANY WARRANTY; without even the implied warranty of MERCHANTABILITY - or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public - License for more details. - - You should have received a copy of the GNU General Public License - along with GCC; see the file COPYING. If not, write to the Free - Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA - 02110-1301, USA. */ - -/* 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); -} |