1080 lines
28 KiB
C
1080 lines
28 KiB
C
/* Control flow graph analysis code for GNU compiler.
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Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
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1999, 2000, 2001, 2003, 2004, 2005 Free Software Foundation, Inc.
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 2, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING. If not, write to the Free
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Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301, USA. */
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/* This file contains various simple utilities to analyze the CFG. */
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#include "config.h"
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#include "system.h"
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#include "coretypes.h"
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#include "tm.h"
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#include "rtl.h"
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#include "obstack.h"
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#include "hard-reg-set.h"
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#include "basic-block.h"
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#include "insn-config.h"
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#include "recog.h"
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#include "toplev.h"
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#include "tm_p.h"
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#include "timevar.h"
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/* Store the data structures necessary for depth-first search. */
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struct depth_first_search_dsS {
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/* stack for backtracking during the algorithm */
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basic_block *stack;
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/* number of edges in the stack. That is, positions 0, ..., sp-1
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have edges. */
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unsigned int sp;
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/* record of basic blocks already seen by depth-first search */
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sbitmap visited_blocks;
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};
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typedef struct depth_first_search_dsS *depth_first_search_ds;
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static void flow_dfs_compute_reverse_init (depth_first_search_ds);
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static void flow_dfs_compute_reverse_add_bb (depth_first_search_ds,
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basic_block);
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static basic_block flow_dfs_compute_reverse_execute (depth_first_search_ds,
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basic_block);
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static void flow_dfs_compute_reverse_finish (depth_first_search_ds);
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static bool flow_active_insn_p (rtx);
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/* Like active_insn_p, except keep the return value clobber around
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even after reload. */
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static bool
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flow_active_insn_p (rtx insn)
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{
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if (active_insn_p (insn))
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return true;
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/* A clobber of the function return value exists for buggy
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programs that fail to return a value. Its effect is to
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keep the return value from being live across the entire
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function. If we allow it to be skipped, we introduce the
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possibility for register lifetime confusion. */
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if (GET_CODE (PATTERN (insn)) == CLOBBER
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&& REG_P (XEXP (PATTERN (insn), 0))
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&& REG_FUNCTION_VALUE_P (XEXP (PATTERN (insn), 0)))
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return true;
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return false;
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}
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/* Return true if the block has no effect and only forwards control flow to
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its single destination. */
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bool
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forwarder_block_p (basic_block bb)
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{
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rtx insn;
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if (bb == EXIT_BLOCK_PTR || bb == ENTRY_BLOCK_PTR
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|| !single_succ_p (bb))
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return false;
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for (insn = BB_HEAD (bb); insn != BB_END (bb); insn = NEXT_INSN (insn))
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if (INSN_P (insn) && flow_active_insn_p (insn))
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return false;
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return (!INSN_P (insn)
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|| (JUMP_P (insn) && simplejump_p (insn))
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|| !flow_active_insn_p (insn));
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}
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/* Return nonzero if we can reach target from src by falling through. */
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bool
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can_fallthru (basic_block src, basic_block target)
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{
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rtx insn = BB_END (src);
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rtx insn2;
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edge e;
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edge_iterator ei;
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if (target == EXIT_BLOCK_PTR)
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return true;
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if (src->next_bb != target)
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return 0;
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FOR_EACH_EDGE (e, ei, src->succs)
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if (e->dest == EXIT_BLOCK_PTR
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&& e->flags & EDGE_FALLTHRU)
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return 0;
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insn2 = BB_HEAD (target);
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if (insn2 && !active_insn_p (insn2))
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insn2 = next_active_insn (insn2);
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/* ??? Later we may add code to move jump tables offline. */
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return next_active_insn (insn) == insn2;
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}
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/* Return nonzero if we could reach target from src by falling through,
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if the target was made adjacent. If we already have a fall-through
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edge to the exit block, we can't do that. */
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bool
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could_fall_through (basic_block src, basic_block target)
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{
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edge e;
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edge_iterator ei;
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if (target == EXIT_BLOCK_PTR)
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return true;
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FOR_EACH_EDGE (e, ei, src->succs)
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if (e->dest == EXIT_BLOCK_PTR
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&& e->flags & EDGE_FALLTHRU)
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return 0;
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return true;
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}
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/* Mark the back edges in DFS traversal.
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Return nonzero if a loop (natural or otherwise) is present.
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Inspired by Depth_First_Search_PP described in:
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Advanced Compiler Design and Implementation
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Steven Muchnick
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Morgan Kaufmann, 1997
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and heavily borrowed from pre_and_rev_post_order_compute. */
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bool
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mark_dfs_back_edges (void)
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{
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edge_iterator *stack;
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int *pre;
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int *post;
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int sp;
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int prenum = 1;
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int postnum = 1;
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sbitmap visited;
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bool found = false;
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/* Allocate the preorder and postorder number arrays. */
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pre = XCNEWVEC (int, last_basic_block);
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post = XCNEWVEC (int, last_basic_block);
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/* Allocate stack for back-tracking up CFG. */
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stack = XNEWVEC (edge_iterator, n_basic_blocks + 1);
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sp = 0;
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/* Allocate bitmap to track nodes that have been visited. */
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visited = sbitmap_alloc (last_basic_block);
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/* None of the nodes in the CFG have been visited yet. */
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sbitmap_zero (visited);
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/* Push the first edge on to the stack. */
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stack[sp++] = ei_start (ENTRY_BLOCK_PTR->succs);
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while (sp)
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{
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edge_iterator ei;
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basic_block src;
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basic_block dest;
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/* Look at the edge on the top of the stack. */
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ei = stack[sp - 1];
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src = ei_edge (ei)->src;
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dest = ei_edge (ei)->dest;
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ei_edge (ei)->flags &= ~EDGE_DFS_BACK;
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/* Check if the edge destination has been visited yet. */
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if (dest != EXIT_BLOCK_PTR && ! TEST_BIT (visited, dest->index))
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{
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/* Mark that we have visited the destination. */
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SET_BIT (visited, dest->index);
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pre[dest->index] = prenum++;
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if (EDGE_COUNT (dest->succs) > 0)
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{
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/* Since the DEST node has been visited for the first
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time, check its successors. */
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stack[sp++] = ei_start (dest->succs);
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}
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else
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post[dest->index] = postnum++;
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}
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else
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{
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if (dest != EXIT_BLOCK_PTR && src != ENTRY_BLOCK_PTR
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&& pre[src->index] >= pre[dest->index]
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&& post[dest->index] == 0)
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ei_edge (ei)->flags |= EDGE_DFS_BACK, found = true;
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if (ei_one_before_end_p (ei) && src != ENTRY_BLOCK_PTR)
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post[src->index] = postnum++;
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if (!ei_one_before_end_p (ei))
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ei_next (&stack[sp - 1]);
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else
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sp--;
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}
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}
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free (pre);
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free (post);
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free (stack);
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sbitmap_free (visited);
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return found;
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}
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/* Set the flag EDGE_CAN_FALLTHRU for edges that can be fallthru. */
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void
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set_edge_can_fallthru_flag (void)
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{
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basic_block bb;
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FOR_EACH_BB (bb)
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{
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edge e;
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edge_iterator ei;
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FOR_EACH_EDGE (e, ei, bb->succs)
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{
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e->flags &= ~EDGE_CAN_FALLTHRU;
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/* The FALLTHRU edge is also CAN_FALLTHRU edge. */
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if (e->flags & EDGE_FALLTHRU)
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e->flags |= EDGE_CAN_FALLTHRU;
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}
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/* If the BB ends with an invertible condjump all (2) edges are
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CAN_FALLTHRU edges. */
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if (EDGE_COUNT (bb->succs) != 2)
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continue;
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if (!any_condjump_p (BB_END (bb)))
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continue;
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if (!invert_jump (BB_END (bb), JUMP_LABEL (BB_END (bb)), 0))
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continue;
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invert_jump (BB_END (bb), JUMP_LABEL (BB_END (bb)), 0);
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EDGE_SUCC (bb, 0)->flags |= EDGE_CAN_FALLTHRU;
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EDGE_SUCC (bb, 1)->flags |= EDGE_CAN_FALLTHRU;
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}
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}
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/* Find unreachable blocks. An unreachable block will have 0 in
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the reachable bit in block->flags. A nonzero value indicates the
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block is reachable. */
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void
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find_unreachable_blocks (void)
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{
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edge e;
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edge_iterator ei;
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basic_block *tos, *worklist, bb;
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tos = worklist = XNEWVEC (basic_block, n_basic_blocks);
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/* Clear all the reachability flags. */
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FOR_EACH_BB (bb)
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bb->flags &= ~BB_REACHABLE;
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/* Add our starting points to the worklist. Almost always there will
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be only one. It isn't inconceivable that we might one day directly
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support Fortran alternate entry points. */
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FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR->succs)
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{
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*tos++ = e->dest;
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/* Mark the block reachable. */
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e->dest->flags |= BB_REACHABLE;
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}
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/* Iterate: find everything reachable from what we've already seen. */
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while (tos != worklist)
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{
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basic_block b = *--tos;
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FOR_EACH_EDGE (e, ei, b->succs)
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{
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basic_block dest = e->dest;
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if (!(dest->flags & BB_REACHABLE))
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{
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*tos++ = dest;
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dest->flags |= BB_REACHABLE;
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}
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}
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}
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free (worklist);
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}
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/* Functions to access an edge list with a vector representation.
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Enough data is kept such that given an index number, the
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pred and succ that edge represents can be determined, or
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given a pred and a succ, its index number can be returned.
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This allows algorithms which consume a lot of memory to
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represent the normally full matrix of edge (pred,succ) with a
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single indexed vector, edge (EDGE_INDEX (pred, succ)), with no
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wasted space in the client code due to sparse flow graphs. */
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/* This functions initializes the edge list. Basically the entire
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flowgraph is processed, and all edges are assigned a number,
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and the data structure is filled in. */
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struct edge_list *
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create_edge_list (void)
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{
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struct edge_list *elist;
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edge e;
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int num_edges;
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int block_count;
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basic_block bb;
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edge_iterator ei;
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block_count = n_basic_blocks; /* Include the entry and exit blocks. */
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num_edges = 0;
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/* Determine the number of edges in the flow graph by counting successor
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edges on each basic block. */
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FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
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{
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num_edges += EDGE_COUNT (bb->succs);
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}
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elist = XNEW (struct edge_list);
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elist->num_blocks = block_count;
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elist->num_edges = num_edges;
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elist->index_to_edge = XNEWVEC (edge, num_edges);
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num_edges = 0;
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/* Follow successors of blocks, and register these edges. */
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FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
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FOR_EACH_EDGE (e, ei, bb->succs)
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elist->index_to_edge[num_edges++] = e;
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return elist;
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}
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/* This function free's memory associated with an edge list. */
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void
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free_edge_list (struct edge_list *elist)
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{
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if (elist)
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{
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free (elist->index_to_edge);
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free (elist);
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}
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}
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/* This function provides debug output showing an edge list. */
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void
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print_edge_list (FILE *f, struct edge_list *elist)
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{
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int x;
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fprintf (f, "Compressed edge list, %d BBs + entry & exit, and %d edges\n",
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elist->num_blocks, elist->num_edges);
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for (x = 0; x < elist->num_edges; x++)
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{
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fprintf (f, " %-4d - edge(", x);
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if (INDEX_EDGE_PRED_BB (elist, x) == ENTRY_BLOCK_PTR)
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fprintf (f, "entry,");
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else
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fprintf (f, "%d,", INDEX_EDGE_PRED_BB (elist, x)->index);
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if (INDEX_EDGE_SUCC_BB (elist, x) == EXIT_BLOCK_PTR)
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fprintf (f, "exit)\n");
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else
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fprintf (f, "%d)\n", INDEX_EDGE_SUCC_BB (elist, x)->index);
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}
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}
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/* This function provides an internal consistency check of an edge list,
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verifying that all edges are present, and that there are no
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extra edges. */
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void
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verify_edge_list (FILE *f, struct edge_list *elist)
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{
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int pred, succ, index;
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edge e;
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basic_block bb, p, s;
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edge_iterator ei;
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FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
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{
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FOR_EACH_EDGE (e, ei, bb->succs)
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{
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pred = e->src->index;
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succ = e->dest->index;
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index = EDGE_INDEX (elist, e->src, e->dest);
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if (index == EDGE_INDEX_NO_EDGE)
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{
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fprintf (f, "*p* No index for edge from %d to %d\n", pred, succ);
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continue;
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}
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if (INDEX_EDGE_PRED_BB (elist, index)->index != pred)
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fprintf (f, "*p* Pred for index %d should be %d not %d\n",
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index, pred, INDEX_EDGE_PRED_BB (elist, index)->index);
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if (INDEX_EDGE_SUCC_BB (elist, index)->index != succ)
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fprintf (f, "*p* Succ for index %d should be %d not %d\n",
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index, succ, INDEX_EDGE_SUCC_BB (elist, index)->index);
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}
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}
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/* We've verified that all the edges are in the list, now lets make sure
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there are no spurious edges in the list. */
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FOR_BB_BETWEEN (p, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
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FOR_BB_BETWEEN (s, ENTRY_BLOCK_PTR->next_bb, NULL, next_bb)
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{
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int found_edge = 0;
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FOR_EACH_EDGE (e, ei, p->succs)
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if (e->dest == s)
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{
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found_edge = 1;
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break;
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}
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FOR_EACH_EDGE (e, ei, s->preds)
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if (e->src == p)
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{
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found_edge = 1;
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break;
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}
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if (EDGE_INDEX (elist, p, s)
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== EDGE_INDEX_NO_EDGE && found_edge != 0)
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fprintf (f, "*** Edge (%d, %d) appears to not have an index\n",
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p->index, s->index);
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if (EDGE_INDEX (elist, p, s)
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!= EDGE_INDEX_NO_EDGE && found_edge == 0)
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fprintf (f, "*** Edge (%d, %d) has index %d, but there is no edge\n",
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p->index, s->index, EDGE_INDEX (elist, p, s));
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}
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}
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/* Given PRED and SUCC blocks, return the edge which connects the blocks.
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If no such edge exists, return NULL. */
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edge
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find_edge (basic_block pred, basic_block succ)
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{
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edge e;
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edge_iterator ei;
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if (EDGE_COUNT (pred->succs) <= EDGE_COUNT (succ->preds))
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{
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FOR_EACH_EDGE (e, ei, pred->succs)
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if (e->dest == succ)
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return e;
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}
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else
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{
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FOR_EACH_EDGE (e, ei, succ->preds)
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if (e->src == pred)
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return e;
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}
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return NULL;
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}
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/* This routine will determine what, if any, edge there is between
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a specified predecessor and successor. */
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int
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find_edge_index (struct edge_list *edge_list, basic_block pred, basic_block succ)
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{
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int x;
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for (x = 0; x < NUM_EDGES (edge_list); x++)
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if (INDEX_EDGE_PRED_BB (edge_list, x) == pred
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&& INDEX_EDGE_SUCC_BB (edge_list, x) == succ)
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return x;
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return (EDGE_INDEX_NO_EDGE);
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}
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/* Dump the list of basic blocks in the bitmap NODES. */
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void
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flow_nodes_print (const char *str, const sbitmap nodes, FILE *file)
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{
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unsigned int node = 0;
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sbitmap_iterator sbi;
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if (! nodes)
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return;
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fprintf (file, "%s { ", str);
|
||
EXECUTE_IF_SET_IN_SBITMAP (nodes, 0, node, sbi)
|
||
fprintf (file, "%d ", node);
|
||
fputs ("}\n", file);
|
||
}
|
||
|
||
/* Dump the list of edges in the array EDGE_LIST. */
|
||
|
||
void
|
||
flow_edge_list_print (const char *str, const edge *edge_list, int num_edges, FILE *file)
|
||
{
|
||
int i;
|
||
|
||
if (! edge_list)
|
||
return;
|
||
|
||
fprintf (file, "%s { ", str);
|
||
for (i = 0; i < num_edges; i++)
|
||
fprintf (file, "%d->%d ", edge_list[i]->src->index,
|
||
edge_list[i]->dest->index);
|
||
|
||
fputs ("}\n", file);
|
||
}
|
||
|
||
|
||
/* This routine will remove any fake predecessor edges for a basic block.
|
||
When the edge is removed, it is also removed from whatever successor
|
||
list it is in. */
|
||
|
||
static void
|
||
remove_fake_predecessors (basic_block bb)
|
||
{
|
||
edge e;
|
||
edge_iterator ei;
|
||
|
||
for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei)); )
|
||
{
|
||
if ((e->flags & EDGE_FAKE) == EDGE_FAKE)
|
||
remove_edge (e);
|
||
else
|
||
ei_next (&ei);
|
||
}
|
||
}
|
||
|
||
/* This routine will remove all fake edges from the flow graph. If
|
||
we remove all fake successors, it will automatically remove all
|
||
fake predecessors. */
|
||
|
||
void
|
||
remove_fake_edges (void)
|
||
{
|
||
basic_block bb;
|
||
|
||
FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR->next_bb, NULL, next_bb)
|
||
remove_fake_predecessors (bb);
|
||
}
|
||
|
||
/* This routine will remove all fake edges to the EXIT_BLOCK. */
|
||
|
||
void
|
||
remove_fake_exit_edges (void)
|
||
{
|
||
remove_fake_predecessors (EXIT_BLOCK_PTR);
|
||
}
|
||
|
||
|
||
/* This function will add a fake edge between any block which has no
|
||
successors, and the exit block. Some data flow equations require these
|
||
edges to exist. */
|
||
|
||
void
|
||
add_noreturn_fake_exit_edges (void)
|
||
{
|
||
basic_block bb;
|
||
|
||
FOR_EACH_BB (bb)
|
||
if (EDGE_COUNT (bb->succs) == 0)
|
||
make_single_succ_edge (bb, EXIT_BLOCK_PTR, EDGE_FAKE);
|
||
}
|
||
|
||
/* This function adds a fake edge between any infinite loops to the
|
||
exit block. Some optimizations require a path from each node to
|
||
the exit node.
|
||
|
||
See also Morgan, Figure 3.10, pp. 82-83.
|
||
|
||
The current implementation is ugly, not attempting to minimize the
|
||
number of inserted fake edges. To reduce the number of fake edges
|
||
to insert, add fake edges from _innermost_ loops containing only
|
||
nodes not reachable from the exit block. */
|
||
|
||
void
|
||
connect_infinite_loops_to_exit (void)
|
||
{
|
||
basic_block unvisited_block = EXIT_BLOCK_PTR;
|
||
struct depth_first_search_dsS dfs_ds;
|
||
|
||
/* Perform depth-first search in the reverse graph to find nodes
|
||
reachable from the exit block. */
|
||
flow_dfs_compute_reverse_init (&dfs_ds);
|
||
flow_dfs_compute_reverse_add_bb (&dfs_ds, EXIT_BLOCK_PTR);
|
||
|
||
/* Repeatedly add fake edges, updating the unreachable nodes. */
|
||
while (1)
|
||
{
|
||
unvisited_block = flow_dfs_compute_reverse_execute (&dfs_ds,
|
||
unvisited_block);
|
||
if (!unvisited_block)
|
||
break;
|
||
|
||
make_edge (unvisited_block, EXIT_BLOCK_PTR, EDGE_FAKE);
|
||
flow_dfs_compute_reverse_add_bb (&dfs_ds, unvisited_block);
|
||
}
|
||
|
||
flow_dfs_compute_reverse_finish (&dfs_ds);
|
||
return;
|
||
}
|
||
|
||
/* Compute reverse top sort order.
|
||
This is computing a post order numbering of the graph. */
|
||
|
||
int
|
||
post_order_compute (int *post_order, bool include_entry_exit)
|
||
{
|
||
edge_iterator *stack;
|
||
int sp;
|
||
int post_order_num = 0;
|
||
sbitmap visited;
|
||
|
||
if (include_entry_exit)
|
||
post_order[post_order_num++] = EXIT_BLOCK;
|
||
|
||
/* Allocate stack for back-tracking up CFG. */
|
||
stack = XNEWVEC (edge_iterator, n_basic_blocks + 1);
|
||
sp = 0;
|
||
|
||
/* Allocate bitmap to track nodes that have been visited. */
|
||
visited = sbitmap_alloc (last_basic_block);
|
||
|
||
/* None of the nodes in the CFG have been visited yet. */
|
||
sbitmap_zero (visited);
|
||
|
||
/* Push the first edge on to the stack. */
|
||
stack[sp++] = ei_start (ENTRY_BLOCK_PTR->succs);
|
||
|
||
while (sp)
|
||
{
|
||
edge_iterator ei;
|
||
basic_block src;
|
||
basic_block dest;
|
||
|
||
/* Look at the edge on the top of the stack. */
|
||
ei = stack[sp - 1];
|
||
src = ei_edge (ei)->src;
|
||
dest = ei_edge (ei)->dest;
|
||
|
||
/* Check if the edge destination has been visited yet. */
|
||
if (dest != EXIT_BLOCK_PTR && ! TEST_BIT (visited, dest->index))
|
||
{
|
||
/* Mark that we have visited the destination. */
|
||
SET_BIT (visited, dest->index);
|
||
|
||
if (EDGE_COUNT (dest->succs) > 0)
|
||
/* Since the DEST node has been visited for the first
|
||
time, check its successors. */
|
||
stack[sp++] = ei_start (dest->succs);
|
||
else
|
||
post_order[post_order_num++] = dest->index;
|
||
}
|
||
else
|
||
{
|
||
if (ei_one_before_end_p (ei) && src != ENTRY_BLOCK_PTR)
|
||
post_order[post_order_num++] = src->index;
|
||
|
||
if (!ei_one_before_end_p (ei))
|
||
ei_next (&stack[sp - 1]);
|
||
else
|
||
sp--;
|
||
}
|
||
}
|
||
|
||
if (include_entry_exit)
|
||
post_order[post_order_num++] = ENTRY_BLOCK;
|
||
|
||
free (stack);
|
||
sbitmap_free (visited);
|
||
return post_order_num;
|
||
}
|
||
|
||
/* Compute the depth first search order and store in the array
|
||
PRE_ORDER if nonzero, marking the nodes visited in VISITED. If
|
||
REV_POST_ORDER is nonzero, return the reverse completion number for each
|
||
node. Returns the number of nodes visited. A depth first search
|
||
tries to get as far away from the starting point as quickly as
|
||
possible.
|
||
|
||
pre_order is a really a preorder numbering of the graph.
|
||
rev_post_order is really a reverse postorder numbering of the graph.
|
||
*/
|
||
|
||
int
|
||
pre_and_rev_post_order_compute (int *pre_order, int *rev_post_order,
|
||
bool include_entry_exit)
|
||
{
|
||
edge_iterator *stack;
|
||
int sp;
|
||
int pre_order_num = 0;
|
||
int rev_post_order_num = n_basic_blocks - 1;
|
||
sbitmap visited;
|
||
|
||
/* Allocate stack for back-tracking up CFG. */
|
||
stack = XNEWVEC (edge_iterator, n_basic_blocks + 1);
|
||
sp = 0;
|
||
|
||
if (include_entry_exit)
|
||
{
|
||
if (pre_order)
|
||
pre_order[pre_order_num] = ENTRY_BLOCK;
|
||
pre_order_num++;
|
||
if (rev_post_order)
|
||
rev_post_order[rev_post_order_num--] = ENTRY_BLOCK;
|
||
}
|
||
else
|
||
rev_post_order_num -= NUM_FIXED_BLOCKS;
|
||
|
||
/* Allocate bitmap to track nodes that have been visited. */
|
||
visited = sbitmap_alloc (last_basic_block);
|
||
|
||
/* None of the nodes in the CFG have been visited yet. */
|
||
sbitmap_zero (visited);
|
||
|
||
/* Push the first edge on to the stack. */
|
||
stack[sp++] = ei_start (ENTRY_BLOCK_PTR->succs);
|
||
|
||
while (sp)
|
||
{
|
||
edge_iterator ei;
|
||
basic_block src;
|
||
basic_block dest;
|
||
|
||
/* Look at the edge on the top of the stack. */
|
||
ei = stack[sp - 1];
|
||
src = ei_edge (ei)->src;
|
||
dest = ei_edge (ei)->dest;
|
||
|
||
/* Check if the edge destination has been visited yet. */
|
||
if (dest != EXIT_BLOCK_PTR && ! TEST_BIT (visited, dest->index))
|
||
{
|
||
/* Mark that we have visited the destination. */
|
||
SET_BIT (visited, dest->index);
|
||
|
||
if (pre_order)
|
||
pre_order[pre_order_num] = dest->index;
|
||
|
||
pre_order_num++;
|
||
|
||
if (EDGE_COUNT (dest->succs) > 0)
|
||
/* Since the DEST node has been visited for the first
|
||
time, check its successors. */
|
||
stack[sp++] = ei_start (dest->succs);
|
||
else if (rev_post_order)
|
||
/* There are no successors for the DEST node so assign
|
||
its reverse completion number. */
|
||
rev_post_order[rev_post_order_num--] = dest->index;
|
||
}
|
||
else
|
||
{
|
||
if (ei_one_before_end_p (ei) && src != ENTRY_BLOCK_PTR
|
||
&& rev_post_order)
|
||
/* There are no more successors for the SRC node
|
||
so assign its reverse completion number. */
|
||
rev_post_order[rev_post_order_num--] = src->index;
|
||
|
||
if (!ei_one_before_end_p (ei))
|
||
ei_next (&stack[sp - 1]);
|
||
else
|
||
sp--;
|
||
}
|
||
}
|
||
|
||
free (stack);
|
||
sbitmap_free (visited);
|
||
|
||
if (include_entry_exit)
|
||
{
|
||
if (pre_order)
|
||
pre_order[pre_order_num] = EXIT_BLOCK;
|
||
pre_order_num++;
|
||
if (rev_post_order)
|
||
rev_post_order[rev_post_order_num--] = EXIT_BLOCK;
|
||
/* The number of nodes visited should be the number of blocks. */
|
||
gcc_assert (pre_order_num == n_basic_blocks);
|
||
}
|
||
else
|
||
/* The number of nodes visited should be the number of blocks minus
|
||
the entry and exit blocks which are not visited here. */
|
||
gcc_assert (pre_order_num == n_basic_blocks - NUM_FIXED_BLOCKS);
|
||
|
||
return pre_order_num;
|
||
}
|
||
|
||
/* Compute the depth first search order on the _reverse_ graph and
|
||
store in the array DFS_ORDER, marking the nodes visited in VISITED.
|
||
Returns the number of nodes visited.
|
||
|
||
The computation is split into three pieces:
|
||
|
||
flow_dfs_compute_reverse_init () creates the necessary data
|
||
structures.
|
||
|
||
flow_dfs_compute_reverse_add_bb () adds a basic block to the data
|
||
structures. The block will start the search.
|
||
|
||
flow_dfs_compute_reverse_execute () continues (or starts) the
|
||
search using the block on the top of the stack, stopping when the
|
||
stack is empty.
|
||
|
||
flow_dfs_compute_reverse_finish () destroys the necessary data
|
||
structures.
|
||
|
||
Thus, the user will probably call ..._init(), call ..._add_bb() to
|
||
add a beginning basic block to the stack, call ..._execute(),
|
||
possibly add another bb to the stack and again call ..._execute(),
|
||
..., and finally call _finish(). */
|
||
|
||
/* Initialize the data structures used for depth-first search on the
|
||
reverse graph. If INITIALIZE_STACK is nonzero, the exit block is
|
||
added to the basic block stack. DATA is the current depth-first
|
||
search context. If INITIALIZE_STACK is nonzero, there is an
|
||
element on the stack. */
|
||
|
||
static void
|
||
flow_dfs_compute_reverse_init (depth_first_search_ds data)
|
||
{
|
||
/* Allocate stack for back-tracking up CFG. */
|
||
data->stack = XNEWVEC (basic_block, n_basic_blocks);
|
||
data->sp = 0;
|
||
|
||
/* Allocate bitmap to track nodes that have been visited. */
|
||
data->visited_blocks = sbitmap_alloc (last_basic_block);
|
||
|
||
/* None of the nodes in the CFG have been visited yet. */
|
||
sbitmap_zero (data->visited_blocks);
|
||
|
||
return;
|
||
}
|
||
|
||
/* Add the specified basic block to the top of the dfs data
|
||
structures. When the search continues, it will start at the
|
||
block. */
|
||
|
||
static void
|
||
flow_dfs_compute_reverse_add_bb (depth_first_search_ds data, basic_block bb)
|
||
{
|
||
data->stack[data->sp++] = bb;
|
||
SET_BIT (data->visited_blocks, bb->index);
|
||
}
|
||
|
||
/* Continue the depth-first search through the reverse graph starting with the
|
||
block at the stack's top and ending when the stack is empty. Visited nodes
|
||
are marked. Returns an unvisited basic block, or NULL if there is none
|
||
available. */
|
||
|
||
static basic_block
|
||
flow_dfs_compute_reverse_execute (depth_first_search_ds data,
|
||
basic_block last_unvisited)
|
||
{
|
||
basic_block bb;
|
||
edge e;
|
||
edge_iterator ei;
|
||
|
||
while (data->sp > 0)
|
||
{
|
||
bb = data->stack[--data->sp];
|
||
|
||
/* Perform depth-first search on adjacent vertices. */
|
||
FOR_EACH_EDGE (e, ei, bb->preds)
|
||
if (!TEST_BIT (data->visited_blocks, e->src->index))
|
||
flow_dfs_compute_reverse_add_bb (data, e->src);
|
||
}
|
||
|
||
/* Determine if there are unvisited basic blocks. */
|
||
FOR_BB_BETWEEN (bb, last_unvisited, NULL, prev_bb)
|
||
if (!TEST_BIT (data->visited_blocks, bb->index))
|
||
return bb;
|
||
|
||
return NULL;
|
||
}
|
||
|
||
/* Destroy the data structures needed for depth-first search on the
|
||
reverse graph. */
|
||
|
||
static void
|
||
flow_dfs_compute_reverse_finish (depth_first_search_ds data)
|
||
{
|
||
free (data->stack);
|
||
sbitmap_free (data->visited_blocks);
|
||
}
|
||
|
||
/* Performs dfs search from BB over vertices satisfying PREDICATE;
|
||
if REVERSE, go against direction of edges. Returns number of blocks
|
||
found and their list in RSLT. RSLT can contain at most RSLT_MAX items. */
|
||
int
|
||
dfs_enumerate_from (basic_block bb, int reverse,
|
||
bool (*predicate) (basic_block, void *),
|
||
basic_block *rslt, int rslt_max, void *data)
|
||
{
|
||
basic_block *st, lbb;
|
||
int sp = 0, tv = 0;
|
||
unsigned size;
|
||
|
||
/* A bitmap to keep track of visited blocks. Allocating it each time
|
||
this function is called is not possible, since dfs_enumerate_from
|
||
is often used on small (almost) disjoint parts of cfg (bodies of
|
||
loops), and allocating a large sbitmap would lead to quadratic
|
||
behavior. */
|
||
static sbitmap visited;
|
||
static unsigned v_size;
|
||
|
||
#define MARK_VISITED(BB) (SET_BIT (visited, (BB)->index))
|
||
#define UNMARK_VISITED(BB) (RESET_BIT (visited, (BB)->index))
|
||
#define VISITED_P(BB) (TEST_BIT (visited, (BB)->index))
|
||
|
||
/* Resize the VISITED sbitmap if necessary. */
|
||
size = last_basic_block;
|
||
if (size < 10)
|
||
size = 10;
|
||
|
||
if (!visited)
|
||
{
|
||
|
||
visited = sbitmap_alloc (size);
|
||
sbitmap_zero (visited);
|
||
v_size = size;
|
||
}
|
||
else if (v_size < size)
|
||
{
|
||
/* Ensure that we increase the size of the sbitmap exponentially. */
|
||
if (2 * v_size > size)
|
||
size = 2 * v_size;
|
||
|
||
visited = sbitmap_resize (visited, size, 0);
|
||
v_size = size;
|
||
}
|
||
|
||
st = XCNEWVEC (basic_block, rslt_max);
|
||
rslt[tv++] = st[sp++] = bb;
|
||
MARK_VISITED (bb);
|
||
while (sp)
|
||
{
|
||
edge e;
|
||
edge_iterator ei;
|
||
lbb = st[--sp];
|
||
if (reverse)
|
||
{
|
||
FOR_EACH_EDGE (e, ei, lbb->preds)
|
||
if (!VISITED_P (e->src) && predicate (e->src, data))
|
||
{
|
||
gcc_assert (tv != rslt_max);
|
||
rslt[tv++] = st[sp++] = e->src;
|
||
MARK_VISITED (e->src);
|
||
}
|
||
}
|
||
else
|
||
{
|
||
FOR_EACH_EDGE (e, ei, lbb->succs)
|
||
if (!VISITED_P (e->dest) && predicate (e->dest, data))
|
||
{
|
||
gcc_assert (tv != rslt_max);
|
||
rslt[tv++] = st[sp++] = e->dest;
|
||
MARK_VISITED (e->dest);
|
||
}
|
||
}
|
||
}
|
||
free (st);
|
||
for (sp = 0; sp < tv; sp++)
|
||
UNMARK_VISITED (rslt[sp]);
|
||
return tv;
|
||
#undef MARK_VISITED
|
||
#undef UNMARK_VISITED
|
||
#undef VISITED_P
|
||
}
|
||
|
||
|
||
/* Compute dominance frontiers, ala Harvey, Ferrante, et al.
|
||
|
||
This algorithm can be found in Timothy Harvey's PhD thesis, at
|
||
http://www.cs.rice.edu/~harv/dissertation.pdf in the section on iterative
|
||
dominance algorithms.
|
||
|
||
First, we identify each join point, j (any node with more than one
|
||
incoming edge is a join point).
|
||
|
||
We then examine each predecessor, p, of j and walk up the dominator tree
|
||
starting at p.
|
||
|
||
We stop the walk when we reach j's immediate dominator - j is in the
|
||
dominance frontier of each of the nodes in the walk, except for j's
|
||
immediate dominator. Intuitively, all of the rest of j's dominators are
|
||
shared by j's predecessors as well.
|
||
Since they dominate j, they will not have j in their dominance frontiers.
|
||
|
||
The number of nodes touched by this algorithm is equal to the size
|
||
of the dominance frontiers, no more, no less.
|
||
*/
|
||
|
||
|
||
static void
|
||
compute_dominance_frontiers_1 (bitmap *frontiers)
|
||
{
|
||
edge p;
|
||
edge_iterator ei;
|
||
basic_block b;
|
||
FOR_EACH_BB (b)
|
||
{
|
||
if (EDGE_COUNT (b->preds) >= 2)
|
||
{
|
||
FOR_EACH_EDGE (p, ei, b->preds)
|
||
{
|
||
basic_block runner = p->src;
|
||
basic_block domsb;
|
||
if (runner == ENTRY_BLOCK_PTR)
|
||
continue;
|
||
|
||
domsb = get_immediate_dominator (CDI_DOMINATORS, b);
|
||
while (runner != domsb)
|
||
{
|
||
if (bitmap_bit_p (frontiers[runner->index], b->index))
|
||
break;
|
||
bitmap_set_bit (frontiers[runner->index],
|
||
b->index);
|
||
runner = get_immediate_dominator (CDI_DOMINATORS,
|
||
runner);
|
||
}
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
|
||
void
|
||
compute_dominance_frontiers (bitmap *frontiers)
|
||
{
|
||
timevar_push (TV_DOM_FRONTIERS);
|
||
|
||
compute_dominance_frontiers_1 (frontiers);
|
||
|
||
timevar_pop (TV_DOM_FRONTIERS);
|
||
}
|
||
|