Source / Include Folder (#88)

Moved Source Files Into `src` Folder

1 files changed, 0 insertions, 1088 deletions

diff --git a/opt.c b/opt.c
deleted file mode 100644
index f8c0ba3..0000000
--- a/opt.c
+++ /dev/null
@@ -1,1088 +0,0 @@
-/****************************************************************************
- * bfs                                                                      *
- * Copyright (C) 2017-2022 Tavian Barnes <tavianator@tavianator.com>        *
- *                                                                          *
- * Permission to use, copy, modify, and/or distribute this software for any *
- * purpose with or without fee is hereby granted.                           *
- *                                                                          *
- * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES *
- * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF         *
- * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR  *
- * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES   *
- * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN    *
- * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF  *
- * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.           *
- ****************************************************************************/
-
-/**
- * The expression optimizer.  Different optimization levels are supported:
- *
- * -O1: basic logical simplifications, like folding (-true -and -foo) to -foo.
- *
- * -O2: dead code elimination and data flow analysis.  struct opt_facts is used
- * to record data flow facts that are true at various points of evaluation.
- * Specifically, struct opt_facts records the facts that must be true before an
- * expression is evaluated (state->facts), and those that must be true after the
- * expression is evaluated, given that it returns true (state->facts_when_true)
- * or false (state->facts_when_true).  Additionally, state->facts_when_impure
- * records the possible data flow facts before any expressions with side effects
- * are evaluated.
- *
- * -O3: expression re-ordering to reduce expected cost.  In an expression like
- * (-foo -and -bar), if both -foo and -bar are pure (no side effects), they can
- * be re-ordered to (-bar -and -foo).  This is profitable if the expected cost
- * is lower for the re-ordered expression, for example if -foo is very slow or
- * -bar is likely to return false.
- *
- * -O4/-Ofast: aggressive optimizations that may affect correctness in corner
- * cases.  The main effect is to use facts_when_impure to determine if any side-
- * effects are reachable at all, and skipping the traversal if not.
- */
-
-#include "opt.h"
-#include "color.h"
-#include "ctx.h"
-#include "diag.h"
-#include "eval.h"
-#include "expr.h"
-#include "pwcache.h"
-#include "util.h"
-#include <assert.h>
-#include <limits.h>
-#include <stdarg.h>
-#include <stdbool.h>
-#include <stdint.h>
-#include <stdio.h>
-#include <string.h>
-#include <unistd.h>
-
-static char *fake_and_arg = "-a";
-static char *fake_or_arg = "-o";
-static char *fake_not_arg = "!";
-
-/**
- * A contrained integer range.
- */
-struct range {
-	/** The (inclusive) minimum value. */
-	long long min;
-	/** The (inclusive) maximum value. */
-	long long max;
-};
-
-/** Compute the minimum of two values. */
-static long long min_value(long long a, long long b) {
-	if (a < b) {
-		return a;
-	} else {
-		return b;
-	}
-}
-
-/** Compute the maximum of two values. */
-static long long max_value(long long a, long long b) {
-	if (a > b) {
-		return a;
-	} else {
-		return b;
-	}
-}
-
-/** Constrain the minimum of a range. */
-static void constrain_min(struct range *range, long long value) {
-	range->min = max_value(range->min, value);
-}
-
-/** Contrain the maximum of a range. */
-static void constrain_max(struct range *range, long long value) {
-	range->max = min_value(range->max, value);
-}
-
-/** Remove a single value from a range. */
-static void range_remove(struct range *range, long long value) {
-	if (range->min == value) {
-		if (range->min == LLONG_MAX) {
-			range->max = LLONG_MIN;
-		} else {
-			++range->min;
-		}
-	}
-
-	if (range->max == value) {
-		if (range->max == LLONG_MIN) {
-			range->min = LLONG_MAX;
-		} else {
-			--range->max;
-		}
-	}
-}
-
-/** Compute the union of two ranges. */
-static void range_union(struct range *result, const struct range *lhs, const struct range *rhs) {
-	result->min = min_value(lhs->min, rhs->min);
-	result->max = max_value(lhs->max, rhs->max);
-}
-
-/** Check if a range contains no values. */
-static bool range_is_impossible(const struct range *range) {
-	return range->min > range->max;
-}
-
-/** Set a range to contain no values. */
-static void set_range_impossible(struct range *range) {
-	range->min = LLONG_MAX;
-	range->max = LLONG_MIN;
-}
-
-/**
- * Types of ranges we track.
- */
-enum range_type {
-	/** Search tree depth. */
-	DEPTH_RANGE,
-	/** Group ID. */
-	GID_RANGE,
-	/** Inode number.  */
-	INUM_RANGE,
-	/** Hard link count. */
-	LINKS_RANGE,
-	/** File size. */
-	SIZE_RANGE,
-	/** User ID. */
-	UID_RANGE,
-	/** The number of range_types. */
-	RANGE_TYPES,
-};
-
-/**
- * A possibly-known value of a predicate.
- */
-enum known_pred {
-	/** The state is impossible to reach. */
-	PRED_IMPOSSIBLE = -2,
-	/** The value of the predicate is not known. */
-	PRED_UNKNOWN = -1,
-	/** The predicate is known to be false. */
-	PRED_FALSE = false,
-	/** The predicate is known to be true. */
-	PRED_TRUE = true,
-};
-
-/** Make a predicate known. */
-static void constrain_pred(enum known_pred *pred, bool value) {
-	if (*pred == PRED_UNKNOWN) {
-		*pred = value;
-	} else if (*pred == !value) {
-		*pred = PRED_IMPOSSIBLE;
-	}
-}
-
-/** Compute the union of two known predicates. */
-static enum known_pred pred_union(enum known_pred lhs, enum known_pred rhs) {
-	if (lhs == PRED_IMPOSSIBLE) {
-		return rhs;
-	} else if (rhs == PRED_IMPOSSIBLE) {
-		return lhs;
-	} else if (lhs == rhs) {
-		return lhs;
-	} else {
-		return PRED_UNKNOWN;
-	}
-}
-
-/**
- * Types of predicates we track.
- */
-enum pred_type {
-	/** -readable */
-	READABLE_PRED,
-	/** -writable */
-	WRITABLE_PRED,
-	/** -executable */
-	EXECUTABLE_PRED,
-	/** -acl */
-	ACL_PRED,
-	/** -capable */
-	CAPABLE_PRED,
-	/** -empty */
-	EMPTY_PRED,
-	/** -hidden */
-	HIDDEN_PRED,
-	/** -nogroup */
-	NOGROUP_PRED,
-	/** -nouser */
-	NOUSER_PRED,
-	/** -sparse */
-	SPARSE_PRED,
-	/** -xattr */
-	XATTR_PRED,
-	/** The number of pred_types. */
-	PRED_TYPES,
-};
-
-/**
- * Data flow facts about an evaluation point.
- */
-struct opt_facts {
-	/** The value ranges we track. */
-	struct range ranges[RANGE_TYPES];
-
-	/** The predicates we track. */
-	enum known_pred preds[PRED_TYPES];
-
-	/** Bitmask of possible file types. */
-	unsigned int types;
-	/** Bitmask of possible link target types. */
-	unsigned int xtypes;
-};
-
-/** Initialize some data flow facts. */
-static void facts_init(struct opt_facts *facts) {
-	for (int i = 0; i < RANGE_TYPES; ++i) {
-		struct range *range = &facts->ranges[i];
-		range->min = 0; // All ranges we currently track are non-negative
-		range->max = LLONG_MAX;
-	}
-
-	for (int i = 0; i < PRED_TYPES; ++i) {
-		facts->preds[i] = PRED_UNKNOWN;
-	}
-
-	facts->types = ~0;
-	facts->xtypes = ~0;
-}
-
-/** Compute the union of two fact sets. */
-static void facts_union(struct opt_facts *result, const struct opt_facts *lhs, const struct opt_facts *rhs) {
-	for (int i = 0; i < RANGE_TYPES; ++i) {
-		range_union(&result->ranges[i], &lhs->ranges[i], &rhs->ranges[i]);
-	}
-
-	for (int i = 0; i < PRED_TYPES; ++i) {
-		result->preds[i] = pred_union(lhs->preds[i], rhs->preds[i]);
-	}
-
-	result->types = lhs->types | rhs->types;
-	result->xtypes = lhs->xtypes | rhs->xtypes;
-}
-
-/** Determine whether a fact set is impossible. */
-static bool facts_are_impossible(const struct opt_facts *facts) {
-	for (int i = 0; i < RANGE_TYPES; ++i) {
-		if (range_is_impossible(&facts->ranges[i])) {
-			return true;
-		}
-	}
-
-	for (int i = 0; i < PRED_TYPES; ++i) {
-		if (facts->preds[i] == PRED_IMPOSSIBLE) {
-			return true;
-		}
-	}
-
-	if (!facts->types || !facts->xtypes) {
-		return true;
-	}
-
-	return false;
-}
-
-/** Set some facts to be impossible. */
-static void set_facts_impossible(struct opt_facts *facts) {
-	for (int i = 0; i < RANGE_TYPES; ++i) {
-		set_range_impossible(&facts->ranges[i]);
-	}
-
-	for (int i = 0; i < PRED_TYPES; ++i) {
-		facts->preds[i] = PRED_IMPOSSIBLE;
-	}
-
-	facts->types = 0;
-	facts->xtypes = 0;
-}
-
-/**
- * Optimizer state.
- */
-struct opt_state {
-	/** The context we're optimizing. */
-	const struct bfs_ctx *ctx;
-
-	/** Data flow facts before this expression is evaluated. */
-	struct opt_facts facts;
-	/** Data flow facts after this expression returns true. */
-	struct opt_facts facts_when_true;
-	/** Data flow facts after this expression returns false. */
-	struct opt_facts facts_when_false;
-	/** Data flow facts before any side-effecting expressions are evaluated. */
-	struct opt_facts *facts_when_impure;
-};
-
-/** Log an optimization. */
-BFS_FORMATTER(3, 4)
-static bool opt_debug(const struct opt_state *state, int level, const char *format, ...) {
-	assert(state->ctx->optlevel >= level);
-
-	if (bfs_debug(state->ctx, DEBUG_OPT, "${cyn}-O%d${rs}: ", level)) {
-		va_list args;
-		va_start(args, format);
-		cvfprintf(state->ctx->cerr, format, args);
-		va_end(args);
-		return true;
-	} else {
-		return false;
-	}
-}
-
-/** Warn about an expression. */
-BFS_FORMATTER(3, 4)
-static void opt_warning(const struct opt_state *state, const struct bfs_expr *expr, const char *format, ...) {
-	if (bfs_expr_warning(state->ctx, expr)) {
-		va_list args;
-		va_start(args, format);
-		bfs_warning(state->ctx, format, args);
-		va_end(args);
-	}
-}
-
-/** Extract a child expression, freeing the outer expression. */
-static struct bfs_expr *extract_child_expr(struct bfs_expr *expr, struct bfs_expr **child) {
-	struct bfs_expr *ret = *child;
-	*child = NULL;
-	bfs_expr_free(expr);
-	return ret;
-}
-
-/**
- * Negate an expression.
- */
-static struct bfs_expr *negate_expr(struct bfs_expr *rhs, char **argv) {
-	if (rhs->eval_fn == eval_not) {
-		return extract_child_expr(rhs, &rhs->rhs);
-	}
-
-	struct bfs_expr *expr = bfs_expr_new(eval_not, 1, argv);
-	if (!expr) {
-		bfs_expr_free(rhs);
-		return NULL;
-	}
-
-	if (argv == &fake_not_arg) {
-		expr->synthetic = true;
-	}
-
-	expr->lhs = NULL;
-	expr->rhs = rhs;
-	return expr;
-}
-
-static struct bfs_expr *optimize_not_expr(const struct opt_state *state, struct bfs_expr *expr);
-static struct bfs_expr *optimize_and_expr(const struct opt_state *state, struct bfs_expr *expr);
-static struct bfs_expr *optimize_or_expr(const struct opt_state *state, struct bfs_expr *expr);
-
-/**
- * Apply De Morgan's laws.
- */
-static struct bfs_expr *de_morgan(const struct opt_state *state, struct bfs_expr *expr, char **argv) {
-	bool debug = opt_debug(state, 1, "De Morgan's laws: %pe ", expr);
-
-	struct bfs_expr *parent = negate_expr(expr, argv);
-	if (!parent) {
-		return NULL;
-	}
-
-	bool has_parent = true;
-	if (parent->eval_fn != eval_not) {
-		expr = parent;
-		has_parent = false;
-	}
-
-	assert(expr->eval_fn == eval_and || expr->eval_fn == eval_or);
-	if (expr->eval_fn == eval_and) {
-		expr->eval_fn = eval_or;
-		expr->argv = &fake_or_arg;
-	} else {
-		expr->eval_fn = eval_and;
-		expr->argv = &fake_and_arg;
-	}
-	expr->synthetic = true;
-
-	expr->lhs = negate_expr(expr->lhs, argv);
-	expr->rhs = negate_expr(expr->rhs, argv);
-	if (!expr->lhs || !expr->rhs) {
-		bfs_expr_free(parent);
-		return NULL;
-	}
-
-	if (debug) {
-		cfprintf(state->ctx->cerr, "<==> %pe\n", parent);
-	}
-
-	if (expr->lhs->eval_fn == eval_not) {
-		expr->lhs = optimize_not_expr(state, expr->lhs);
-	}
-	if (expr->rhs->eval_fn == eval_not) {
-		expr->rhs = optimize_not_expr(state, expr->rhs);
-	}
-	if (!expr->lhs || !expr->rhs) {
-		bfs_expr_free(parent);
-		return NULL;
-	}
-
-	if (expr->eval_fn == eval_and) {
-		expr = optimize_and_expr(state, expr);
-	} else {
-		expr = optimize_or_expr(state, expr);
-	}
-	if (has_parent) {
-		parent->rhs = expr;
-	} else {
-		parent = expr;
-	}
-	if (!expr) {
-		bfs_expr_free(parent);
-		return NULL;
-	}
-
-	if (has_parent) {
-		parent = optimize_not_expr(state, parent);
-	}
-	return parent;
-}
-
-/** Optimize an expression recursively. */
-static struct bfs_expr *optimize_expr_recursive(struct opt_state *state, struct bfs_expr *expr);
-
-/**
- * Optimize a negation.
- */
-static struct bfs_expr *optimize_not_expr(const struct opt_state *state, struct bfs_expr *expr) {
-	assert(expr->eval_fn == eval_not);
-
-	struct bfs_expr *rhs = expr->rhs;
-
-	int optlevel = state->ctx->optlevel;
-	if (optlevel >= 1) {
-		if (rhs == &bfs_true) {
-			opt_debug(state, 1, "constant propagation: %pe <==> %pe\n", expr, &bfs_false);
-			bfs_expr_free(expr);
-			return &bfs_false;
-		} else if (rhs == &bfs_false) {
-			opt_debug(state, 1, "constant propagation: %pe <==> %pe\n", expr, &bfs_true);
-			bfs_expr_free(expr);
-			return &bfs_true;
-		} else if (rhs->eval_fn == eval_not) {
-			opt_debug(state, 1, "double negation: %pe <==> %pe\n", expr, rhs->rhs);
-			return extract_child_expr(expr, &rhs->rhs);
-		} else if (bfs_expr_never_returns(rhs)) {
-			opt_debug(state, 1, "reachability: %pe <==> %pe\n", expr, rhs);
-			return extract_child_expr(expr, &expr->rhs);
-		} else if ((rhs->eval_fn == eval_and || rhs->eval_fn == eval_or)
-			   && (rhs->lhs->eval_fn == eval_not || rhs->rhs->eval_fn == eval_not)) {
-			return de_morgan(state, expr, expr->argv);
-		}
-	}
-
-	expr->pure = rhs->pure;
-	expr->always_true = rhs->always_false;
-	expr->always_false = rhs->always_true;
-	expr->cost = rhs->cost;
-	expr->probability = 1.0 - rhs->probability;
-
-	return expr;
-}
-
-/** Optimize a negation recursively. */
-static struct bfs_expr *optimize_not_expr_recursive(struct opt_state *state, struct bfs_expr *expr) {
-	struct opt_state rhs_state = *state;
-	expr->rhs = optimize_expr_recursive(&rhs_state, expr->rhs);
-	if (!expr->rhs) {
-		goto fail;
-	}
-
-	state->facts_when_true = rhs_state.facts_when_false;
-	state->facts_when_false = rhs_state.facts_when_true;
-
-	return optimize_not_expr(state, expr);
-
-fail:
-	bfs_expr_free(expr);
-	return NULL;
-}
-
-/** Optimize a conjunction. */
-static struct bfs_expr *optimize_and_expr(const struct opt_state *state, struct bfs_expr *expr) {
-	assert(expr->eval_fn == eval_and);
-
-	struct bfs_expr *lhs = expr->lhs;
-	struct bfs_expr *rhs = expr->rhs;
-
-	const struct bfs_ctx *ctx = state->ctx;
-	int optlevel = ctx->optlevel;
-	if (optlevel >= 1) {
-		if (lhs == &bfs_true) {
-			opt_debug(state, 1, "conjunction elimination: %pe <==> %pe\n", expr, rhs);
-			return extract_child_expr(expr, &expr->rhs);
-		} else if (rhs == &bfs_true) {
-			opt_debug(state, 1, "conjunction elimination: %pe <==> %pe\n", expr, lhs);
-			return extract_child_expr(expr, &expr->lhs);
-		} else if (lhs->always_false) {
-			opt_debug(state, 1, "short-circuit: %pe <==> %pe\n", expr, lhs);
-			opt_warning(state, expr->rhs, "This expression is unreachable.\n\n");
-			return extract_child_expr(expr, &expr->lhs);
-		} else if (lhs->always_true && rhs == &bfs_false) {
-			bool debug = opt_debug(state, 1, "strength reduction: %pe <==> ", expr);
-			struct bfs_expr *ret = extract_child_expr(expr, &expr->lhs);
-			ret = negate_expr(ret, &fake_not_arg);
-			if (debug && ret) {
-				cfprintf(ctx->cerr, "%pe\n", ret);
-			}
-			return ret;
-		} else if (optlevel >= 2 && lhs->pure && rhs == &bfs_false) {
-			opt_debug(state, 2, "purity: %pe <==> %pe\n", expr, rhs);
-			opt_warning(state, expr->lhs, "The result of this expression is ignored.\n\n");
-			return extract_child_expr(expr, &expr->rhs);
-		} else if (lhs->eval_fn == eval_not && rhs->eval_fn == eval_not) {
-			return de_morgan(state, expr, expr->lhs->argv);
-		}
-	}
-
-	expr->pure = lhs->pure && rhs->pure;
-	expr->always_true = lhs->always_true && rhs->always_true;
-	expr->always_false = lhs->always_false || rhs->always_false;
-	expr->cost = lhs->cost + lhs->probability*rhs->cost;
-	expr->probability = lhs->probability*rhs->probability;
-
-	return expr;
-}
-
-/** Optimize a conjunction recursively. */
-static struct bfs_expr *optimize_and_expr_recursive(struct opt_state *state, struct bfs_expr *expr) {
-	struct opt_state lhs_state = *state;
-	expr->lhs = optimize_expr_recursive(&lhs_state, expr->lhs);
-	if (!expr->lhs) {
-		goto fail;
-	}
-
-	struct opt_state rhs_state = *state;
-	rhs_state.facts = lhs_state.facts_when_true;
-	expr->rhs = optimize_expr_recursive(&rhs_state, expr->rhs);
-	if (!expr->rhs) {
-		goto fail;
-	}
-
-	state->facts_when_true = rhs_state.facts_when_true;
-	facts_union(&state->facts_when_false, &lhs_state.facts_when_false, &rhs_state.facts_when_false);
-
-	return optimize_and_expr(state, expr);
-
-fail:
-	bfs_expr_free(expr);
-	return NULL;
-}
-
-/** Optimize a disjunction. */
-static struct bfs_expr *optimize_or_expr(const struct opt_state *state, struct bfs_expr *expr) {
-	assert(expr->eval_fn == eval_or);
-
-	struct bfs_expr *lhs = expr->lhs;
-	struct bfs_expr *rhs = expr->rhs;
-
-	const struct bfs_ctx *ctx = state->ctx;
-	int optlevel = ctx->optlevel;
-	if (optlevel >= 1) {
-		if (lhs->always_true) {
-			opt_debug(state, 1, "short-circuit: %pe <==> %pe\n", expr, lhs);
-			opt_warning(state, expr->rhs, "This expression is unreachable.\n\n");
-			return extract_child_expr(expr, &expr->lhs);
-		} else if (lhs == &bfs_false) {
-			opt_debug(state, 1, "disjunctive syllogism: %pe <==> %pe\n", expr, rhs);
-			return extract_child_expr(expr, &expr->rhs);
-		} else if (rhs == &bfs_false) {
-			opt_debug(state, 1, "disjunctive syllogism: %pe <==> %pe\n", expr, lhs);
-			return extract_child_expr(expr, &expr->lhs);
-		} else if (lhs->always_false && rhs == &bfs_true) {
-			bool debug = opt_debug(state, 1, "strength reduction: %pe <==> ", expr);
-			struct bfs_expr *ret = extract_child_expr(expr, &expr->lhs);
-			ret = negate_expr(ret, &fake_not_arg);
-			if (debug && ret) {
-				cfprintf(ctx->cerr, "%pe\n", ret);
-			}
-			return ret;
-		} else if (optlevel >= 2 && lhs->pure && rhs == &bfs_true) {
-			opt_debug(state, 2, "purity: %pe <==> %pe\n", expr, rhs);
-			opt_warning(state, expr->lhs, "The result of this expression is ignored.\n\n");
-			return extract_child_expr(expr, &expr->rhs);
-		} else if (lhs->eval_fn == eval_not && rhs->eval_fn == eval_not) {
-			return de_morgan(state, expr, expr->lhs->argv);
-		}
-	}
-
-	expr->pure = lhs->pure && rhs->pure;
-	expr->always_true = lhs->always_true || rhs->always_true;
-	expr->always_false = lhs->always_false && rhs->always_false;
-	expr->cost = lhs->cost + (1 - lhs->probability)*rhs->cost;
-	expr->probability = lhs->probability + rhs->probability - lhs->probability*rhs->probability;
-
-	return expr;
-}
-
-/** Optimize a disjunction recursively. */
-static struct bfs_expr *optimize_or_expr_recursive(struct opt_state *state, struct bfs_expr *expr) {
-	struct opt_state lhs_state = *state;
-	expr->lhs = optimize_expr_recursive(&lhs_state, expr->lhs);
-	if (!expr->lhs) {
-		goto fail;
-	}
-
-	struct opt_state rhs_state = *state;
-	rhs_state.facts = lhs_state.facts_when_false;
-	expr->rhs = optimize_expr_recursive(&rhs_state, expr->rhs);
-	if (!expr->rhs) {
-		goto fail;
-	}
-
-	facts_union(&state->facts_when_true, &lhs_state.facts_when_true, &rhs_state.facts_when_true);
-	state->facts_when_false = rhs_state.facts_when_false;
-
-	return optimize_or_expr(state, expr);
-
-fail:
-	bfs_expr_free(expr);
-	return NULL;
-}
-
-/** Optimize an expression in an ignored-result context. */
-static struct bfs_expr *ignore_result(const struct opt_state *state, struct bfs_expr *expr) {
-	int optlevel = state->ctx->optlevel;
-
-	if (optlevel >= 1) {
-		while (true) {
-			if (expr->eval_fn == eval_not) {
-				opt_debug(state, 1, "ignored result: %pe --> %pe\n", expr, expr->rhs);
-				opt_warning(state, expr, "The result of this expression is ignored.\n\n");
-				expr = extract_child_expr(expr, &expr->rhs);
-			} else if (optlevel >= 2
-			           && (expr->eval_fn == eval_and || expr->eval_fn == eval_or || expr->eval_fn == eval_comma)
-			           && expr->rhs->pure) {
-				opt_debug(state, 2, "ignored result: %pe --> %pe\n", expr, expr->lhs);
-				opt_warning(state, expr->rhs, "The result of this expression is ignored.\n\n");
-				expr = extract_child_expr(expr, &expr->lhs);
-			} else {
-				break;
-			}
-		}
-
-		if (optlevel >= 2 && expr->pure && expr != &bfs_false) {
-			opt_debug(state, 2, "ignored result: %pe --> %pe\n", expr, &bfs_false);
-			opt_warning(state, expr, "The result of this expression is ignored.\n\n");
-			bfs_expr_free(expr);
-			expr = &bfs_false;
-		}
-	}
-
-	return expr;
-}
-
-/** Optimize a comma expression. */
-static struct bfs_expr *optimize_comma_expr(const struct opt_state *state, struct bfs_expr *expr) {
-	assert(expr->eval_fn == eval_comma);
-
-	struct bfs_expr *lhs = expr->lhs;
-	struct bfs_expr *rhs = expr->rhs;
-
-	int optlevel = state->ctx->optlevel;
-	if (optlevel >= 1) {
-		lhs = expr->lhs = ignore_result(state, lhs);
-
-		if (bfs_expr_never_returns(lhs)) {
-			opt_debug(state, 1, "reachability: %pe <==> %pe\n", expr, lhs);
-			opt_warning(state, expr->rhs, "This expression is unreachable.\n\n");
-			return extract_child_expr(expr, &expr->lhs);
-		} else if ((lhs->always_true && rhs == &bfs_true)
-			   || (lhs->always_false && rhs == &bfs_false)) {
-			opt_debug(state, 1, "redundancy elimination: %pe <==> %pe\n", expr, lhs);
-			return extract_child_expr(expr, &expr->lhs);
-		} else if (optlevel >= 2 && lhs->pure) {
-			opt_debug(state, 2, "purity: %pe <==> %pe\n", expr, rhs);
-			opt_warning(state, expr->lhs, "The result of this expression is ignored.\n\n");
-			return extract_child_expr(expr, &expr->rhs);
-		}
-	}
-
-	expr->pure = lhs->pure && rhs->pure;
-	expr->always_true = bfs_expr_never_returns(lhs) || rhs->always_true;
-	expr->always_false = bfs_expr_never_returns(lhs) || rhs->always_false;
-	expr->cost = lhs->cost + rhs->cost;
-	expr->probability = rhs->probability;
-
-	return expr;
-}
-
-/** Optimize a comma expression recursively. */
-static struct bfs_expr *optimize_comma_expr_recursive(struct opt_state *state, struct bfs_expr *expr) {
-	struct opt_state lhs_state = *state;
-	expr->lhs = optimize_expr_recursive(&lhs_state, expr->lhs);
-	if (!expr->lhs) {
-		goto fail;
-	}
-
-	struct opt_state rhs_state = *state;
-	facts_union(&rhs_state.facts, &lhs_state.facts_when_true, &lhs_state.facts_when_false);
-	expr->rhs = optimize_expr_recursive(&rhs_state, expr->rhs);
-	if (!expr->rhs) {
-		goto fail;
-	}
-
-	return optimize_comma_expr(state, expr);
-
-fail:
-	bfs_expr_free(expr);
-	return NULL;
-}
-
-/** Infer data flow facts about a predicate. */
-static void infer_pred_facts(struct opt_state *state, enum pred_type pred) {
-	constrain_pred(&state->facts_when_true.preds[pred], true);
-	constrain_pred(&state->facts_when_false.preds[pred], false);
-}
-
-/** Infer data flow facts about an -{execut,read,writ}able expression. */
-static void infer_access_facts(struct opt_state *state, const struct bfs_expr *expr) {
-	if (expr->num & R_OK) {
-		infer_pred_facts(state, READABLE_PRED);
-	}
-	if (expr->num & W_OK) {
-		infer_pred_facts(state, WRITABLE_PRED);
-	}
-	if (expr->num & X_OK) {
-		infer_pred_facts(state, EXECUTABLE_PRED);
-	}
-}
-
-/** Infer data flow facts about an icmp-style ([+-]N) expression. */
-static void infer_icmp_facts(struct opt_state *state, const struct bfs_expr *expr, enum range_type type) {
-	struct range *range_when_true = &state->facts_when_true.ranges[type];
-	struct range *range_when_false = &state->facts_when_false.ranges[type];
-	long long value = expr->num;
-
-	switch (expr->int_cmp) {
-	case BFS_INT_EQUAL:
-		constrain_min(range_when_true, value);
-		constrain_max(range_when_true, value);
-		range_remove(range_when_false, value);
-		break;
-
-	case BFS_INT_LESS:
-		constrain_min(range_when_false, value);
-		constrain_max(range_when_true, value);
-		range_remove(range_when_true, value);
-		break;
-
-	case BFS_INT_GREATER:
-		constrain_max(range_when_false, value);
-		constrain_min(range_when_true, value);
-		range_remove(range_when_true, value);
-		break;
-	}
-}
-
-/** Infer data flow facts about a -gid expression. */
-static void infer_gid_facts(struct opt_state *state, const struct bfs_expr *expr) {
-	infer_icmp_facts(state, expr, GID_RANGE);
-
-	const struct bfs_groups *groups = bfs_ctx_groups(state->ctx);
-	struct range *range = &state->facts_when_true.ranges[GID_RANGE];
-	if (groups && range->min == range->max) {
-		gid_t gid = range->min;
-		bool nogroup = !bfs_getgrgid(groups, gid);
-		constrain_pred(&state->facts_when_true.preds[NOGROUP_PRED], nogroup);
-	}
-}
-
-/** Infer data flow facts about a -uid expression. */
-static void infer_uid_facts(struct opt_state *state, const struct bfs_expr *expr) {
-	infer_icmp_facts(state, expr, UID_RANGE);
-
-	const struct bfs_users *users = bfs_ctx_users(state->ctx);
-	struct range *range = &state->facts_when_true.ranges[UID_RANGE];
-	if (users && range->min == range->max) {
-		uid_t uid = range->min;
-		bool nouser = !bfs_getpwuid(users, uid);
-		constrain_pred(&state->facts_when_true.preds[NOUSER_PRED], nouser);
-	}
-}
-
-/** Infer data flow facts about a -samefile expression. */
-static void infer_samefile_facts(struct opt_state *state, const struct bfs_expr *expr) {
-	struct range *range_when_true = &state->facts_when_true.ranges[INUM_RANGE];
-	constrain_min(range_when_true, expr->ino);
-	constrain_max(range_when_true, expr->ino);
-}
-
-/** Infer data flow facts about a -type expression. */
-static void infer_type_facts(struct opt_state *state, const struct bfs_expr *expr) {
-	state->facts_when_true.types &= expr->num;
-	state->facts_when_false.types &= ~expr->num;
-}
-
-/** Infer data flow facts about an -xtype expression. */
-static void infer_xtype_facts(struct opt_state *state, const struct bfs_expr *expr) {
-	state->facts_when_true.xtypes &= expr->num;
-	state->facts_when_false.xtypes &= ~expr->num;
-}
-
-static struct bfs_expr *optimize_expr_recursive(struct opt_state *state, struct bfs_expr *expr) {
-	int optlevel = state->ctx->optlevel;
-
-	state->facts_when_true = state->facts;
-	state->facts_when_false = state->facts;
-
-	if (optlevel >= 2 && facts_are_impossible(&state->facts)) {
-		opt_debug(state, 2, "reachability: %pe --> %pe\n", expr, &bfs_false);
-		opt_warning(state, expr, "This expression is unreachable.\n\n");
-		bfs_expr_free(expr);
-		expr = &bfs_false;
-		goto done;
-	}
-
-	if (!bfs_expr_has_children(expr) && !expr->pure) {
-		facts_union(state->facts_when_impure, state->facts_when_impure, &state->facts);
-	}
-
-	if (expr->eval_fn == eval_access) {
-		infer_access_facts(state, expr);
-	} else if (expr->eval_fn == eval_acl) {
-		infer_pred_facts(state, ACL_PRED);
-	} else if (expr->eval_fn == eval_capable) {
-		infer_pred_facts(state, CAPABLE_PRED);
-	} else if (expr->eval_fn == eval_depth) {
-		infer_icmp_facts(state, expr, DEPTH_RANGE);
-	} else if (expr->eval_fn == eval_empty) {
-		infer_pred_facts(state, EMPTY_PRED);
-	} else if (expr->eval_fn == eval_gid) {
-		infer_gid_facts(state, expr);
-	} else if (expr->eval_fn == eval_hidden) {
-		infer_pred_facts(state, HIDDEN_PRED);
-	} else if (expr->eval_fn == eval_inum) {
-		infer_icmp_facts(state, expr, INUM_RANGE);
-	} else if (expr->eval_fn == eval_links) {
-		infer_icmp_facts(state, expr, LINKS_RANGE);
-	} else if (expr->eval_fn == eval_nogroup) {
-		infer_pred_facts(state, NOGROUP_PRED);
-	} else if (expr->eval_fn == eval_nouser) {
-		infer_pred_facts(state, NOUSER_PRED);
-	} else if (expr->eval_fn == eval_samefile) {
-		infer_samefile_facts(state, expr);
-	} else if (expr->eval_fn == eval_size) {
-		infer_icmp_facts(state, expr, SIZE_RANGE);
-	} else if (expr->eval_fn == eval_sparse) {
-		infer_pred_facts(state, SPARSE_PRED);
-	} else if (expr->eval_fn == eval_type) {
-		infer_type_facts(state, expr);
-	} else if (expr->eval_fn == eval_uid) {
-		infer_uid_facts(state, expr);
-	} else if (expr->eval_fn == eval_xattr) {
-		infer_pred_facts(state, XATTR_PRED);
-	} else if (expr->eval_fn == eval_xtype) {
-		infer_xtype_facts(state, expr);
-	} else if (expr->eval_fn == eval_not) {
-		expr = optimize_not_expr_recursive(state, expr);
-	} else if (expr->eval_fn == eval_and) {
-		expr = optimize_and_expr_recursive(state, expr);
-	} else if (expr->eval_fn == eval_or) {
-		expr = optimize_or_expr_recursive(state, expr);
-	} else if (expr->eval_fn == eval_comma) {
-		expr = optimize_comma_expr_recursive(state, expr);
-	}
-
-	if (!expr) {
-		goto done;
-	}
-
-	if (bfs_expr_has_children(expr)) {
-		struct bfs_expr *lhs = expr->lhs;
-		struct bfs_expr *rhs = expr->rhs;
-		if (rhs) {
-			expr->persistent_fds = rhs->persistent_fds;
-			expr->ephemeral_fds = rhs->ephemeral_fds;
-		}
-		if (lhs) {
-			expr->persistent_fds += lhs->persistent_fds;
-			if (lhs->ephemeral_fds > expr->ephemeral_fds) {
-				expr->ephemeral_fds = lhs->ephemeral_fds;
-			}
-		}
-	}
-
-	if (expr->always_true) {
-		set_facts_impossible(&state->facts_when_false);
-	}
-	if (expr->always_false) {
-		set_facts_impossible(&state->facts_when_true);
-	}
-
-	if (optlevel < 2 || expr == &bfs_true || expr == &bfs_false) {
-		goto done;
-	}
-
-	if (facts_are_impossible(&state->facts_when_true)) {
-		if (expr->pure) {
-			opt_debug(state, 2, "data flow: %pe --> %pe\n", expr, &bfs_false);
-			opt_warning(state, expr, "This expression is always false.\n\n");
-			bfs_expr_free(expr);
-			expr = &bfs_false;
-		} else {
-			expr->always_false = true;
-			expr->probability = 0.0;
-		}
-	} else if (facts_are_impossible(&state->facts_when_false)) {
-		if (expr->pure) {
-			opt_debug(state, 2, "data flow: %pe --> %pe\n", expr, &bfs_true);
-			opt_warning(state, expr, "This expression is always true.\n\n");
-			bfs_expr_free(expr);
-			expr = &bfs_true;
-		} else {
-			expr->always_true = true;
-			expr->probability = 1.0;
-		}
-	}
-
-done:
-	return expr;
-}
-
-/** Swap the children of a binary expression if it would reduce the cost. */
-static bool reorder_expr(const struct opt_state *state, struct bfs_expr *expr, float swapped_cost) {
-	if (swapped_cost < expr->cost) {
-		bool debug = opt_debug(state, 3, "cost: %pe <==> ", expr);
-		struct bfs_expr *lhs = expr->lhs;
-		expr->lhs = expr->rhs;
-		expr->rhs = lhs;
-		if (debug) {
-			cfprintf(state->ctx->cerr, "%pe (~${ylw}%g${rs} --> ~${ylw}%g${rs})\n", expr, expr->cost, swapped_cost);
-		}
-		expr->cost = swapped_cost;
-		return true;
-	} else {
-		return false;
-	}
-}
-
-/**
- * Recursively reorder sub-expressions to reduce the overall cost.
- *
- * @param expr
- *         The expression to optimize.
- * @return
- *         Whether any subexpression was reordered.
- */
-static bool reorder_expr_recursive(const struct opt_state *state, struct bfs_expr *expr) {
-	if (!bfs_expr_has_children(expr)) {
-		return false;
-	}
-
-	struct bfs_expr *lhs = expr->lhs;
-	struct bfs_expr *rhs = expr->rhs;
-
-	bool ret = false;
-	if (lhs) {
-		ret |= reorder_expr_recursive(state, lhs);
-	}
-	if (rhs) {
-		ret |= reorder_expr_recursive(state, rhs);
-	}
-
-	if (expr->eval_fn == eval_and || expr->eval_fn == eval_or) {
-		if (lhs->pure && rhs->pure) {
-			float rhs_prob = expr->eval_fn == eval_and ? rhs->probability : 1.0 - rhs->probability;
-			float swapped_cost = rhs->cost + rhs_prob*lhs->cost;
-			ret |= reorder_expr(state, expr, swapped_cost);
-		}
-	}
-
-	return ret;
-}
-
-/**
- * Optimize a top-level expression.
- */
-static struct bfs_expr *optimize_expr(struct opt_state *state, struct bfs_expr *expr) {
-	struct opt_facts saved_impure = *state->facts_when_impure;
-
-	expr = optimize_expr_recursive(state, expr);
-	if (!expr) {
-		return NULL;
-	}
-
-	if (state->ctx->optlevel >= 3 && reorder_expr_recursive(state, expr)) {
-		// Re-do optimizations to account for the new ordering
-		*state->facts_when_impure = saved_impure;
-		expr = optimize_expr_recursive(state, expr);
-		if (!expr) {
-			return NULL;
-		}
-	}
-
-	return expr;
-}
-
-int bfs_optimize(struct bfs_ctx *ctx) {
-	bfs_ctx_dump(ctx, DEBUG_OPT);
-
-	struct opt_facts facts_when_impure;
-	set_facts_impossible(&facts_when_impure);
-
-	struct opt_state state = {
-		.ctx = ctx,
-		.facts_when_impure = &facts_when_impure,
-	};
-	facts_init(&state.facts);
-
-	ctx->exclude = optimize_expr(&state, ctx->exclude);
-	if (!ctx->exclude) {
-		return -1;
-	}
-
-	// Only non-excluded files are evaluated
-	state.facts = state.facts_when_false;
-
-	struct range *depth = &state.facts.ranges[DEPTH_RANGE];
-	constrain_min(depth, ctx->mindepth);
-	constrain_max(depth, ctx->maxdepth);
-
-	ctx->expr = optimize_expr(&state, ctx->expr);
-	if (!ctx->expr) {
-		return -1;
-	}
-
-	ctx->expr = ignore_result(&state, ctx->expr);
-
-	if (facts_are_impossible(&facts_when_impure)) {
-		bfs_warning(ctx, "This command won't do anything.\n\n");
-	}
-
-	const struct range *depth_when_impure = &facts_when_impure.ranges[DEPTH_RANGE];
-	long long mindepth = depth_when_impure->min;
-	long long maxdepth = depth_when_impure->max;
-
-	int optlevel = ctx->optlevel;
-
-	if (optlevel >= 2 && mindepth > ctx->mindepth) {
-		if (mindepth > INT_MAX) {
-			mindepth = INT_MAX;
-		}
-		ctx->mindepth = mindepth;
-		opt_debug(&state, 2, "data flow: mindepth --> %d\n", ctx->mindepth);
-	}
-
-	if (optlevel >= 4 && maxdepth < ctx->maxdepth) {
-		if (maxdepth < INT_MIN) {
-			maxdepth = INT_MIN;
-		}
-		ctx->maxdepth = maxdepth;
-		opt_debug(&state, 4, "data flow: maxdepth --> %d\n", ctx->maxdepth);
-	}
-
-	return 0;
-}