irconsconfirm.c

/*
 * Copyright (C) 1995-2008 University of Karlsruhe.  All right reserved.
 *
 * This file is part of libFirm.
 *
 * This file may be distributed and/or modified under the terms of the
 * GNU General Public License version 2 as published by the Free Software
 * Foundation and appearing in the file LICENSE.GPL included in the
 * packaging of this file.
 *
 * Licensees holding valid libFirm Professional Edition licenses may use
 * this file in accordance with the libFirm Commercial License.
 * Agreement provided with the Software.
 *
 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE.
 */

/**
 * @file
 * @brief    Construction of Confirm nodes
 * @author   Michael Beck
 * @date     6.2005
 * @version  $Id$
 */
#include "config.h"

#include "irgraph_t.h"
#include "irnode_t.h"
#include "ircons_t.h"
#include "irgmod.h"
#include "iropt_dbg.h"
#include "iredges_t.h"
#include "irgwalk.h"
#include "irprintf.h"
#include "irgopt.h"
#include "irtools.h"
#include "array_t.h"
#include "debug.h"
#include "irflag.h"

/**
 * Walker environment.
 */
typedef struct _env_t {
	unsigned num_confirms;  /**< Number of inserted Confirm nodes. */
	unsigned num_consts;    /**< Number of constants placed. */
	unsigned num_eq;        /**< Number of equalities placed. */
	unsigned num_non_null;  /**< Number of non-null Confirms. */
} env_t;

/** The debug handle. */
DEBUG_ONLY(static firm_dbg_module_t *dbg;)

/**
 * Return the effective use block of a node and it's predecessor on
 * position pos.
 *
 * @param node  the node
 * @param pos   the position of the used input
 *
 * This handles correctly Phi nodes.
 */
static ir_node *get_effective_use_block(ir_node *node, int pos) {
	if (is_Phi(node)) {
		/* the effective use of a Phi argument is in its predecessor block */
		node = get_nodes_block(node);
		return get_Block_cfgpred_block(node, pos);
	}
	return get_nodes_block(node);
}

/**
 * Handle a CASE-branch.
 *
 * @param block   the block which is entered by the branch
 * @param irn     the node expressing the switch value
 * @param nr      the branch label
 * @param env     statistical environment
 *
 * Branch labels are a simple case. We can replace the value
 * by a Const with the branch label.
 */
static void handle_case(ir_node *block, ir_node *irn, long nr, env_t *env) {
	const ir_edge_t *edge, *next;
	ir_node *c = NULL;

	if (is_Bad(irn))
		return;

	for (edge = get_irn_out_edge_first(irn); edge; edge = next) {
		ir_node *succ = get_edge_src_irn(edge);
		int     pos   = get_edge_src_pos(edge);
		ir_node *blk  = get_effective_use_block(succ, pos);

		next = get_irn_out_edge_next(irn, edge);

		if (block_dominates(block, blk)) {
			/*
			 * Ok, we found a user of irn that is placed
			 * in a block dominated by the branch block.
			 * We can replace the input with the Constant
			 * branch label.
			 */

			if (! c) {
				ir_mode *mode = get_irn_mode(irn);
				ir_type *tp   = get_irn_type(irn);
				tarval *tv    = new_tarval_from_long(nr, mode);
				c = new_r_Const_type(current_ir_graph, tv, tp);
			}

			set_irn_n(succ, pos, c);
			DBG_OPT_CONFIRM_C(irn, c);
			DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));

			env->num_consts += 1;
		}
	}
}  /* handle_case */

/**
 * Handle a mode_b input of Cond nodes.
 *
 * @param block     the block which is entered by the branch
 * @param selector  the mode_b node expressing the branch condition
 * @param pnc       the true/false condition branch
 * @param env       statistical environment
 */
static void handle_modeb(ir_node *block, ir_node *selector, pn_Cond pnc, env_t *env) {
	ir_node *cond, *old, *cond_block = NULL, *other_blk = NULL, *con = NULL;
	ir_node *c_b = NULL, *c_o = NULL;
	const ir_edge_t *edge, *next;

	for (edge = get_irn_out_edge_first(selector); edge; edge = next) {
		ir_node *user     = get_edge_src_irn(edge);
		int     pos       = get_edge_src_pos(edge);
		ir_node *user_blk = get_effective_use_block(user, pos);

		next = get_irn_out_edge_next(selector, edge);
		if (block_dominates(block, user_blk)) {
			/*
			 * Ok, we found a usage of selector in a block
			 * dominated by the branch block.
			 * We can replace the input with true/false.
			 */
			if (con == NULL) {
				con = new_Const(pnc == pn_Cond_true ? tarval_b_true : tarval_b_false);
			}
			old = get_irn_n(user, pos);
			set_irn_n(user, pos, con);
			DBG_OPT_CONFIRM_C(old, con);

			DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, user, con));

			env->num_consts += 1;
		} else {
			int i, n;

			/* get the other block */
			if (other_blk == NULL) {
				/* we have already tested, that block has only ONE Cond predecessor */
				cond = get_Proj_pred(get_Block_cfgpred(block, 0));
				cond_block = get_nodes_block(cond);
				foreach_out_edge(cond, edge) {
					ir_node *proj = get_edge_src_irn(edge);
					if (get_Proj_proj(proj) == (long)pnc)
						continue;
					edge = get_irn_out_edge_first(proj);
					other_blk = get_edge_src_irn(edge);
					break;
				}
				assert(other_blk);

			 	/*
				 * Note the special case here: if block is a then, there might be no else
				 * block. In that case the other_block is the user_blk itself and pred_block
				 * is the cond_block ...
				 *
				 * Best would be to introduce a block here, removing this critical edge.
				 * For some reasons I cannot repair dominance here, so I have to remove
				 * ALL critical edges...
				 * FIXME: This should not be needed if we could repair dominance ...
				 */
			}

			n = get_Block_n_cfgpreds(user_blk);

			/*
			 * We have found a user in a non-dominated block:
			 * check, if all its block predecessors are dominated.
			 * If yes, place a Phi.
			 */
			for (i = n - 1; i >= 0; --i) {
				ir_node *pred_blk = get_Block_cfgpred_block(user_blk, i);

				if (!block_dominates(block, pred_blk) &&
				    !block_dominates(other_blk, pred_blk)) {
					/* can't do anything */
					break;
				}
			}
			if (i < 0) {
				ir_node *phi, **in;

				NEW_ARR_A(ir_node *, in, n);
				/* ok, ALL predecessors are either dominated by block OR other block */
				if (c_b == NULL) {
					ir_node *c_true  = new_Const(tarval_b_true);
					ir_node *c_false = new_Const(tarval_b_false);
					if (pnc == pn_Cond_true) {
						c_b = c_true;
						c_o = c_false;
					} else {
						c_b = c_false;
						c_o = c_true;
					}
				}
				for (i = n - 1; i >= 0; --i) {
					ir_node *pred_blk = get_Block_cfgpred_block(user_blk, i);

					if (block_dominates(block, pred_blk))
						in[i] = c_b;
					else
						in[i] = c_o;
				}
				phi = new_r_Phi(current_ir_graph, user_blk, n, in, mode_b);
				set_irn_n(user, pos, phi);
			}
		}
	}
}

/**
 * Handle an IF-branch.
 *
 * @param block   the block which is entered by the branch
 * @param cmp     the Cmp node expressing the branch condition
 * @param pnc     the Compare relation for taking this branch
 * @param env     statistical environment
 */
static void handle_if(ir_node *block, ir_node *cmp, pn_Cmp pnc, env_t *env) {
	ir_node *left  = get_Cmp_left(cmp);
	ir_node *right = get_Cmp_right(cmp);
	ir_node *cond_block;
	ir_op *op;
	const ir_edge_t *edge, *next;

	/* Beware of Bads */
	if (is_Bad(left) || is_Bad(right))
		return;

	op = get_irn_op(left);

	/* Do not create Confirm nodes for Cmp(Const, Const) constructs.
	   These are removed anyway */
	if (op == op_Const && is_Const(right))
		return;

	/* try to place the constant on the right side for a Confirm */
	if (op == op_Const || op == op_SymConst) {
		ir_node *t = left;

		left  = right;
		right = t;

		pnc = get_inversed_pnc(pnc);
	}

	/*
	 * First case: both values are identical.
	 * replace the left one by the right (potentially const) one.
	 */
	if (pnc == pn_Cmp_Eq) {
		cond_block = get_Block_cfgpred_block(block, 0);
		for (edge = get_irn_out_edge_first(left); edge; edge = next) {
			ir_node *user = get_edge_src_irn(edge);
			int     pos   = get_edge_src_pos(edge);
			ir_node *blk  = get_effective_use_block(user, pos);

			next = get_irn_out_edge_next(left, edge);
			if (block_dominates(block, blk)) {
				/*
				 * Ok, we found a usage of left in a block
				 * dominated by the branch block.
				 * We can replace the input with right.
				 */
				set_irn_n(user, pos, right);
				DBG_OPT_CONFIRM(left, right);

				DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, user, right));

				env->num_eq += 1;
			} else if (block_dominates(blk, cond_block)) {
				if (is_Const(right) && get_irn_pinned(user) == op_pin_state_floats) {
					/*
					 * left == Const and we found a movable user of left in a
					 * dominator of the Cond block
					 */
					const ir_edge_t *edge, *next;
					for (edge = get_irn_out_edge_first(user); edge; edge = next) {
						ir_node *usr_of_usr = get_edge_src_irn(edge);
						int      npos = get_edge_src_pos(edge);
						ir_node *blk  = get_effective_use_block(usr_of_usr, npos);

						next = get_irn_out_edge_next(user, edge);
						if (block_dominates(block, blk)) {
							/*
							 * The user of the user is dominated by our true/false
							 * block. So, create a copy of user WITH the constant
							 * replacing it's pos'th input.
							 *
							 * This is always good for unop's and might be good
							 * for binops.
							 *
							 * If user has other user in the false/true block, code
							 * placement will move it down.
							 * If there are users in cond block or upper, we create
							 * "redundant ops", because one will have a const op,
							 * the other no const ...
							 */
							ir_node *new_op = exact_copy(user);
							set_nodes_block(new_op, block);
							set_irn_n(new_op, pos, right);
							set_irn_n(usr_of_usr, npos, new_op);
						}
					}
				}
			}
		}
	} else { /* not pn_Cmp_Eq cases */
		ir_node *c = NULL;

		foreach_out_edge_safe(left, edge, next) {
			ir_node *succ = get_edge_src_irn(edge);
			int     pos   = get_edge_src_pos(edge);
			ir_node *blk  = get_effective_use_block(succ, pos);

			if (block_dominates(block, blk)) {
				/*
				 * Ok, we found a usage of left in a block
				 * dominated by the branch block.
				 * We can replace the input with a Confirm(left, pnc, right).
				 */
				if (! c)
					c = new_r_Confirm(current_ir_graph, block, left, right, pnc);

				pos = get_edge_src_pos(edge);
				set_irn_n(succ, pos, c);
				DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));

				env->num_confirms += 1;
			}
		}

		if (! is_Const(right)) {
			/* also construct inverse Confirms */
			ir_node *rc = NULL;

			pnc = get_inversed_pnc(pnc);
			foreach_out_edge_safe(right, edge, next) {
				ir_node *succ = get_edge_src_irn(edge);
				int     pos;
				ir_node *blk;

				if (succ == c)
					continue;

				pos  = get_edge_src_pos(edge);
				blk  = get_effective_use_block(succ, pos);

				if (block_dominates(block, blk)) {
					/*
					 * Ok, we found a usage of right in a block
					 * dominated by the branch block.
					 * We can replace the input with a Confirm(right, pnc^-1, left).
					 */
					if (! rc)
						rc = new_r_Confirm(current_ir_graph, block, right, left, pnc);

					pos = get_edge_src_pos(edge);
					set_irn_n(succ, pos, rc);
					DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, rc));

					env->num_confirms += 1;
				}
			}
		}
	}
}  /* handle_if */

/**
 * Pre-block-walker: Called for every block to insert Confirm nodes
 */
static void insert_Confirm_in_block(ir_node *block, void *env) {
	ir_node *cond, *proj, *selector;
	ir_mode *mode;

	/*
	 * we can only handle blocks with only ONE control flow
	 * predecessor yet.
	 */
	if (get_Block_n_cfgpreds(block) != 1)
		return;

	proj = get_Block_cfgpred(block, 0);
	if (! is_Proj(proj))
		return;

	cond = get_Proj_pred(proj);
	if (! is_Cond(cond))
		return;

	selector = get_Cond_selector(cond);
	mode = get_irn_mode(selector);

	if (mode == mode_b) {
		ir_node *cmp;
		pn_Cmp pnc;

		handle_modeb(block, selector, get_Proj_proj(proj), env);

		/* this should be an IF, check this */
		if (! is_Proj(selector))
			return;

		cmp = get_Proj_pred(selector);
		if (! is_Cmp(cmp))
			return;

		pnc = get_Proj_proj(selector);

		if (get_Proj_proj(proj) != pn_Cond_true) {
			/* it's the false branch */
			mode = get_irn_mode(get_Cmp_left(cmp));
			pnc = get_negated_pnc(pnc, mode);
		}
		DB((dbg, LEVEL_2, "At %+F using %+F Confirm %=\n", block, cmp, pnc));

		handle_if(block, cmp, pnc, env);
	} else if (mode_is_int(mode)) {
		long proj_nr = get_Proj_proj(proj);

		/* this is a CASE, but we cannot handle the default case */
		if (proj_nr == get_Cond_default_proj(cond))
			return;

		handle_case(block, get_Cond_selector(cond), proj_nr, env);
	}
}  /* insert_Confirm_in_block */

/**
 * Checks if a node is a non-null Confirm.
 */
static int is_non_null_Confirm(const ir_node *ptr) {
	for (;;) {
		if (! is_Confirm(ptr))
			break;
		if (get_Confirm_cmp(ptr) == pn_Cmp_Lg) {
			ir_node *bound = get_Confirm_bound(ptr);

			if (is_Const(bound) && is_Const_null(bound))
				return 1;
		}
		ptr = get_Confirm_value(ptr);
	}
	/*
	 * While a SymConst is not a Confirm, it is non-null
	 * anyway. This helps to reduce the number of
	 * constructed Confirms.
	 */
	if (is_SymConst_addr_ent(ptr))
		return 1;
	return 0;
}  /* is_non_null_Confirm */

/**
 * The given pointer will be dereferenced, add non-null Confirms.
 *
 * @param ptr    a node representing an address
 * @param block  the block of the dereferencing instruction
 * @param env    environment
 */
static void insert_non_null(ir_node *ptr, ir_node *block, env_t *env) {
	const ir_edge_t *edge, *next;
	ir_node         *c = NULL;

	foreach_out_edge_safe(ptr, edge, next) {
		ir_node *succ = get_edge_src_irn(edge);
		int     pos;
		ir_node *blk;


		/* for now, we place a Confirm only in front of a Cmp */
		if (! is_Cmp(succ))
			continue;

		pos = get_edge_src_pos(edge);
		blk = get_effective_use_block(succ, pos);

		if (block_dominates(block, blk)) {
			/*
			 * Ok, we found a usage of ptr in a block
			 * dominated by the Load/Store block.
			 * We can replace the input with a Confirm(ptr, !=, NULL).
			 */
			if (c == NULL) {
				ir_mode *mode = get_irn_mode(ptr);
				c = new_Const(get_mode_null(mode));

				c = new_r_Confirm(current_ir_graph, block, ptr, c, pn_Cmp_Lg);
			}

			set_irn_n(succ, pos, c);
			DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));

			env->num_non_null += 1;
			env->num_confirms += 1;
		}
	}
}  /* insert_non_null */

/**
 * Pre-walker: Called for every node to insert Confirm nodes
 */
static void insert_Confirm(ir_node *node, void *env) {
	ir_node *ptr;

	switch (get_irn_opcode(node)) {
	case iro_Block:
		insert_Confirm_in_block(node, env);
		break;
	case iro_Load:
		ptr = get_Load_ptr(node);
		if (! is_non_null_Confirm(ptr))
			insert_non_null(ptr, get_nodes_block(node), env);
		break;
	case iro_Store:
		ptr = get_Store_ptr(node);
		if (! is_non_null_Confirm(ptr))
			insert_non_null(ptr, get_nodes_block(node), env);
		break;
	default:
		break;
	}
}  /* insert_Confirm */

/*
 * Construct Confirm nodes
 */
void construct_confirms(ir_graph *irg) {
	env_t env;
	int edges_active = edges_activated(irg);


	FIRM_DBG_REGISTER(dbg, "firm.ana.confirm");

	remove_critical_cf_edges(irg);

	/* we need dominance info */
	assure_doms(irg);

	assert(get_irg_pinned(irg) == op_pin_state_pinned &&
	       "Nodes must be placed to insert Confirms");

	if (! edges_active) {
		/* We need edges */
		edges_activate(irg);
	}

	env.num_confirms = 0;
	env.num_consts   = 0;
	env.num_eq       = 0;
	env.num_non_null = 0;

	if (get_opt_global_null_ptr_elimination()) {
		/* do global NULL test elimination */
		irg_walk_graph(irg, insert_Confirm, NULL, &env);
	} else {
		/* now, visit all blocks and add Confirms where possible */
		irg_block_walk_graph(irg, insert_Confirm_in_block, NULL, &env);
	}

	if (env.num_confirms | env.num_consts | env.num_eq) {
		/* we have add nodes or changed DF edges */
		set_irg_outs_inconsistent(irg);

		/* the new nodes are not in the loop info */
		set_irg_loopinfo_inconsistent(irg);
	}

	DB((dbg, LEVEL_1, "# Confirms inserted : %u\n", env.num_confirms));
	DB((dbg, LEVEL_1, "# Const replacements: %u\n", env.num_consts));
	DB((dbg, LEVEL_1, "# node equalities   : %u\n", env.num_eq));
	DB((dbg, LEVEL_1, "# non-null Confirms : %u\n", env.num_non_null));

	/* deactivate edges if they where off */
	if (! edges_active)
		edges_deactivate(irg);
}  /* construct_confirms */

#if 0
/**
 * Post-walker: Remove Confirm nodes
 */
static void rem_Confirm(ir_node *n, void *env) {
	(void) env;
	if (is_Confirm(n)) {
		ir_node *value = get_Confirm_value(n);
		if (value != n)
			exchange(n, value);
		else {
			/*
			 * Strange: a Confirm is its own bound. This can happen
			 * in dead blocks when Phi nodes are already removed.
			 */
			exchange(n, new_Bad());
		}
	}
}  /* rem_Confirm */
#endif

/*
 * Remove all Confirm nodes from a graph.
 */
void remove_confirms(ir_graph *irg) {
	int rem = get_opt_remove_confirm();

	set_opt_remove_confirm(1);
	optimize_graph_df(irg);
	set_opt_remove_confirm(rem);
}  /* remove_confirms */