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-/****************************************************************************
- * 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;
-}