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Diffstat (limited to 'opt.c')
| -rw-r--r-- | opt.c | 870 |
1 files changed, 0 insertions, 870 deletions
@@ -1,870 +0,0 @@ -/**************************************************************************** - * bfs * - * Copyright (C) 2017-2019 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 "cmdline.h" -#include "color.h" -#include "eval.h" -#include "expr.h" -#include <assert.h> -#include <limits.h> -#include <stdarg.h> -#include <stdio.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_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. */ - MAX_RANGE, -}; - -/** - * Data flow facts about an evaluation point. - */ -struct opt_facts { - /** The value ranges we track. */ - struct range ranges[MAX_RANGE]; - - /** Bitmask of possible file types. */ - enum bftw_typeflag types; - /** Bitmask of possible link target types. */ - enum bftw_typeflag xtypes; -}; - -/** Initialize some data flow facts. */ -static void facts_init(struct opt_facts *facts) { - for (int i = 0; i < MAX_RANGE; ++i) { - struct range *range = facts->ranges + i; - range->min = 0; // All ranges we currently track are non-negative - range->max = LLONG_MAX; - } - - 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 < MAX_RANGE; ++i) { - range_union(result->ranges + i, lhs->ranges + i, rhs->ranges + i); - } - - result->types = lhs->types | rhs->types; - result->xtypes = lhs->xtypes | rhs->xtypes; -} - -/** Determine whether a fact set is impossible. */ -static bool facts_impossible(const struct opt_facts *facts) { - for (int i = 0; i < MAX_RANGE; ++i) { - if (range_impossible(facts->ranges + i)) { - 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 < MAX_RANGE; ++i) { - set_range_impossible(facts->ranges + i); - } - - facts->types = 0; - facts->xtypes = 0; -} - -/** - * Optimizer state. - */ -struct opt_state { - /** The command line we're optimizing. */ - const struct cmdline *cmdline; - - /** 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. */ -static void debug_opt(const struct opt_state *state, const char *format, ...) { - if (!(state->cmdline->debug & DEBUG_OPT)) { - return; - } - - CFILE *cerr = state->cmdline->cerr; - - va_list args; - va_start(args, format); - - for (const char *i = format; *i != '\0'; ++i) { - if (*i == '%') { - switch (*++i) { - case 'd': - fprintf(cerr->file, "%d", va_arg(args, int)); - break; - - case 'e': - dump_expr(cerr, va_arg(args, const struct expr *), false); - break; - - case 'g': - cfprintf(cerr, "${ylw}%g${rs}", va_arg(args, double)); - break; - - default: - assert(false); - break; - } - } else { - fputc(*i, stderr); - } - } - - va_end(args); -} - -/** Extract a child expression, freeing the outer expression. */ -static struct expr *extract_child_expr(struct expr *expr, struct expr **child) { - struct expr *ret = *child; - *child = NULL; - free_expr(expr); - return ret; -} - -/** - * Negate an expression. - */ -static struct expr *negate_expr(struct expr *rhs, char **argv) { - if (rhs->eval == eval_not) { - return extract_child_expr(rhs, &rhs->rhs); - } - - struct expr *expr = new_expr(eval_not, 1, argv); - if (!expr) { - free_expr(rhs); - return NULL; - } - - expr->rhs = rhs; - return expr; -} - -static struct expr *optimize_not_expr(const struct opt_state *state, struct expr *expr); -static struct expr *optimize_and_expr(const struct opt_state *state, struct expr *expr); -static struct expr *optimize_or_expr(const struct opt_state *state, struct expr *expr); - -/** - * Apply De Morgan's laws. - */ -static struct expr *de_morgan(const struct opt_state *state, struct expr *expr, char **argv) { - debug_opt(state, "-O1: De Morgan's laws: %e ", expr); - - struct expr *parent = negate_expr(expr, argv); - if (!parent) { - return NULL; - } - - bool has_parent = true; - if (parent->eval != eval_not) { - expr = parent; - has_parent = false; - } - - if (expr->eval == eval_and) { - expr->eval = eval_or; - expr->argv = &fake_or_arg; - } else { - assert(expr->eval == eval_or); - expr->eval = eval_and; - expr->argv = &fake_and_arg; - } - - expr->lhs = negate_expr(expr->lhs, argv); - expr->rhs = negate_expr(expr->rhs, argv); - if (!expr->lhs || !expr->rhs) { - free_expr(parent); - return NULL; - } - - debug_opt(state, "<==> %e\n", parent); - - if (expr->lhs->eval == eval_not) { - expr->lhs = optimize_not_expr(state, expr->lhs); - } - if (expr->rhs->eval == eval_not) { - expr->rhs = optimize_not_expr(state, expr->rhs); - } - if (!expr->lhs || !expr->rhs) { - free_expr(parent); - return NULL; - } - - if (expr->eval == eval_and) { - expr = optimize_and_expr(state, expr); - } else { - expr = optimize_or_expr(state, expr); - } - if (!expr) { - if (has_parent) { - parent->rhs = NULL; - free_expr(parent); - } - return NULL; - } - - if (has_parent) { - parent = optimize_not_expr(state, parent); - } - return parent; -} - -/** Optimize an expression recursively. */ -static struct expr *optimize_expr_recursive(struct opt_state *state, struct expr *expr); - -/** - * Optimize a negation. - */ -static struct expr *optimize_not_expr(const struct opt_state *state, struct expr *expr) { - assert(expr->eval == eval_not); - - struct expr *rhs = expr->rhs; - - int optlevel = state->cmdline->optlevel; - if (optlevel >= 1) { - if (rhs == &expr_true) { - debug_opt(state, "-O1: constant propagation: %e <==> %e\n", expr, &expr_false); - free_expr(expr); - return &expr_false; - } else if (rhs == &expr_false) { - debug_opt(state, "-O1: constant propagation: %e <==> %e\n", expr, &expr_true); - free_expr(expr); - return &expr_true; - } else if (rhs->eval == eval_not) { - debug_opt(state, "-O1: double negation: %e <==> %e\n", expr, rhs->rhs); - return extract_child_expr(expr, &rhs->rhs); - } else if (expr_never_returns(rhs)) { - debug_opt(state, "-O1: reachability: %e <==> %e\n", expr, rhs); - return extract_child_expr(expr, &expr->rhs); - } else if ((rhs->eval == eval_and || rhs->eval == eval_or) - && (rhs->lhs->eval == eval_not || rhs->rhs->eval == 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 expr *optimize_not_expr_recursive(struct opt_state *state, struct 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: - free_expr(expr); - return NULL; -} - -/** Optimize a conjunction. */ -static struct expr *optimize_and_expr(const struct opt_state *state, struct expr *expr) { - assert(expr->eval == eval_and); - - struct expr *lhs = expr->lhs; - struct expr *rhs = expr->rhs; - - int optlevel = state->cmdline->optlevel; - if (optlevel >= 1) { - if (lhs == &expr_true) { - debug_opt(state, "-O1: conjunction elimination: %e <==> %e\n", expr, rhs); - return extract_child_expr(expr, &expr->rhs); - } else if (rhs == &expr_true) { - debug_opt(state, "-O1: conjunction elimination: %e <==> %e\n", expr, lhs); - return extract_child_expr(expr, &expr->lhs); - } else if (lhs->always_false) { - debug_opt(state, "-O1: short-circuit: %e <==> %e\n", expr, lhs); - return extract_child_expr(expr, &expr->lhs); - } else if (lhs->always_true && rhs == &expr_false) { - debug_opt(state, "-O1: strength reduction: %e <==> ", expr); - struct expr *ret = extract_child_expr(expr, &expr->lhs); - ret = negate_expr(ret, &fake_not_arg); - if (ret) { - debug_opt(state, "%e\n", ret); - } - return ret; - } else if (optlevel >= 2 && lhs->pure && rhs == &expr_false) { - debug_opt(state, "-O2: purity: %e <==> %e\n", expr, rhs); - return extract_child_expr(expr, &expr->rhs); - } else if (lhs->eval == eval_not && rhs->eval == 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 expr *optimize_and_expr_recursive(struct opt_state *state, struct 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: - free_expr(expr); - return NULL; -} - -/** Optimize a disjunction. */ -static struct expr *optimize_or_expr(const struct opt_state *state, struct expr *expr) { - assert(expr->eval == eval_or); - - struct expr *lhs = expr->lhs; - struct expr *rhs = expr->rhs; - - int optlevel = state->cmdline->optlevel; - if (optlevel >= 1) { - if (lhs->always_true) { - debug_opt(state, "-O1: short-circuit: %e <==> %e\n", expr, lhs); - return extract_child_expr(expr, &expr->lhs); - } else if (lhs == &expr_false) { - debug_opt(state, "-O1: disjunctive syllogism: %e <==> %e\n", expr, rhs); - return extract_child_expr(expr, &expr->rhs); - } else if (rhs == &expr_false) { - debug_opt(state, "-O1: disjunctive syllogism: %e <==> %e\n", expr, lhs); - return extract_child_expr(expr, &expr->lhs); - } else if (lhs->always_false && rhs == &expr_true) { - debug_opt(state, "-O1: strength reduction: %e <==> ", expr); - struct expr *ret = extract_child_expr(expr, &expr->lhs); - ret = negate_expr(ret, &fake_not_arg); - if (ret) { - debug_opt(state, "%e\n", ret); - } - return ret; - } else if (optlevel >= 2 && lhs->pure && rhs == &expr_true) { - debug_opt(state, "-O2: purity: %e <==> %e\n", expr, rhs); - return extract_child_expr(expr, &expr->rhs); - } else if (lhs->eval == eval_not && rhs->eval == 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 expr *optimize_or_expr_recursive(struct opt_state *state, struct 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: - free_expr(expr); - return NULL; -} - -/** Optimize an expression in an ignored-result context. */ -static struct expr *ignore_result(const struct opt_state *state, struct expr *expr) { - int optlevel = state->cmdline->optlevel; - - if (optlevel >= 1) { - while (true) { - if (expr->eval == eval_not) { - debug_opt(state, "-O1: ignored result: %e --> %e\n", expr, expr->rhs); - expr = extract_child_expr(expr, &expr->rhs); - } else if (optlevel >= 2 - && (expr->eval == eval_and || expr->eval == eval_or || expr->eval == eval_comma) - && expr->rhs->pure) { - debug_opt(state, "-O2: ignored result: %e --> %e\n", expr, expr->lhs); - expr = extract_child_expr(expr, &expr->lhs); - } else { - break; - } - } - - if (optlevel >= 2 && expr->pure && expr != &expr_false) { - debug_opt(state, "-O2: ignored result: %e --> %e\n", expr, &expr_false); - free_expr(expr); - expr = &expr_false; - } - } - - return expr; -} - -/** Optimize a comma expression. */ -static struct expr *optimize_comma_expr(const struct opt_state *state, struct expr *expr) { - assert(expr->eval == eval_comma); - - struct expr *lhs = expr->lhs; - struct expr *rhs = expr->rhs; - - int optlevel = state->cmdline->optlevel; - if (optlevel >= 1) { - lhs = expr->lhs = ignore_result(state, lhs); - - if (expr_never_returns(lhs)) { - debug_opt(state, "-O1: reachability: %e <==> %e\n", expr, lhs); - return extract_child_expr(expr, &expr->lhs); - } else if ((lhs->always_true && rhs == &expr_true) - || (lhs->always_false && rhs == &expr_false)) { - debug_opt(state, "-O1: redundancy elimination: %e <==> %e\n", expr, lhs); - return extract_child_expr(expr, &expr->lhs); - } else if (optlevel >= 2 && lhs->pure) { - debug_opt(state, "-O2: purity: %e <==> %e\n", expr, rhs); - return extract_child_expr(expr, &expr->rhs); - } - } - - expr->pure = lhs->pure && rhs->pure; - expr->always_true = expr_never_returns(lhs) || rhs->always_true; - expr->always_false = 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 expr *optimize_comma_expr_recursive(struct opt_state *state, struct 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: - free_expr(expr); - return NULL; -} - -/** Infer data flow facts about an icmp-style ([+-]N) expression */ -static void infer_icmp_facts(struct opt_state *state, const struct 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->idata; - - switch (expr->cmp_flag) { - case CMP_EXACT: - constrain_min(range_when_true, value); - constrain_max(range_when_true, value); - range_remove(range_when_false, value); - break; - - case CMP_LESS: - constrain_min(range_when_false, value); - constrain_max(range_when_true, value); - range_remove(range_when_true, value); - break; - - case CMP_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 -samefile expression. */ -static void infer_samefile_facts(struct opt_state *state, const struct 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 expr *expr) { - state->facts_when_true.types &= expr->idata; - state->facts_when_false.types &= ~expr->idata; -} - -/** Infer data flow facts about an -xtype expression. */ -static void infer_xtype_facts(struct opt_state *state, const struct expr *expr) { - state->facts_when_true.xtypes &= expr->idata; - state->facts_when_false.xtypes &= ~expr->idata; -} - -static struct expr *optimize_expr_recursive(struct opt_state *state, struct expr *expr) { - state->facts_when_true = state->facts; - state->facts_when_false = state->facts; - - if (expr->eval == eval_depth) { - infer_icmp_facts(state, expr, DEPTH_RANGE); - } else if (expr->eval == eval_gid) { - infer_icmp_facts(state, expr, GID_RANGE); - } else if (expr->eval == eval_inum) { - infer_icmp_facts(state, expr, INUM_RANGE); - } else if (expr->eval == eval_links) { - infer_icmp_facts(state, expr, LINKS_RANGE); - } else if (expr->eval == eval_samefile) { - infer_samefile_facts(state, expr); - } else if (expr->eval == eval_size) { - infer_icmp_facts(state, expr, SIZE_RANGE); - } else if (expr->eval == eval_type) { - infer_type_facts(state, expr); - } else if (expr->eval == eval_uid) { - infer_icmp_facts(state, expr, UID_RANGE); - } else if (expr->eval == eval_xtype) { - infer_xtype_facts(state, expr); - } else if (expr->eval == eval_not) { - expr = optimize_not_expr_recursive(state, expr); - } else if (expr->eval == eval_and) { - expr = optimize_and_expr_recursive(state, expr); - } else if (expr->eval == eval_or) { - expr = optimize_or_expr_recursive(state, expr); - } else if (expr->eval == eval_comma) { - expr = optimize_comma_expr_recursive(state, expr); - } else if (!expr->pure) { - facts_union(state->facts_when_impure, state->facts_when_impure, &state->facts); - } - - if (!expr) { - goto done; - } - - struct expr *lhs = expr->lhs; - struct 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 (state->cmdline->optlevel < 2 || expr == &expr_true || expr == &expr_false) { - goto done; - } - - if (facts_impossible(&state->facts_when_true)) { - if (expr->pure) { - debug_opt(state, "-O2: data flow: %e --> %e\n", expr, &expr_false); - free_expr(expr); - expr = &expr_false; - } else { - expr->always_false = true; - expr->probability = 0.0; - } - } else if (facts_impossible(&state->facts_when_false)) { - if (expr->pure) { - debug_opt(state, "-O2: data flow: %e --> %e\n", expr, &expr_true); - free_expr(expr); - expr = &expr_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 expr *expr, double swapped_cost) { - if (swapped_cost < expr->cost) { - debug_opt(state, "-O3: cost: %e", expr); - struct expr *lhs = expr->lhs; - expr->lhs = expr->rhs; - expr->rhs = lhs; - debug_opt(state, " <==> %e (~%g --> ~%g)\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 expr *expr) { - bool ret = false; - struct expr *lhs = expr->lhs; - struct expr *rhs = expr->rhs; - - if (lhs) { - ret |= reorder_expr_recursive(state, lhs); - } - if (rhs) { - ret |= reorder_expr_recursive(state, rhs); - } - - if (expr->eval == eval_and || expr->eval == eval_or) { - if (lhs->pure && rhs->pure) { - double rhs_prob = expr->eval == eval_and ? rhs->probability : 1.0 - rhs->probability; - double swapped_cost = rhs->cost + rhs_prob*lhs->cost; - ret |= reorder_expr(state, expr, swapped_cost); - } - } - - return ret; -} - -int optimize_cmdline(struct cmdline *cmdline) { - struct opt_facts facts_when_impure; - set_facts_impossible(&facts_when_impure); - - struct opt_state state = { - .cmdline = cmdline, - .facts_when_impure = &facts_when_impure, - }; - facts_init(&state.facts); - - struct range *depth = state.facts.ranges + DEPTH_RANGE; - depth->min = cmdline->mindepth; - depth->max = cmdline->maxdepth; - - int optlevel = cmdline->optlevel; - - cmdline->expr = optimize_expr_recursive(&state, cmdline->expr); - if (!cmdline->expr) { - return -1; - } - - if (optlevel >= 3 && reorder_expr_recursive(&state, cmdline->expr)) { - // Re-do optimizations to account for the new ordering - set_facts_impossible(&facts_when_impure); - cmdline->expr = optimize_expr_recursive(&state, cmdline->expr); - if (!cmdline->expr) { - return -1; - } - } - - cmdline->expr = ignore_result(&state, cmdline->expr); - - 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; - - if (optlevel >= 2 && mindepth > cmdline->mindepth) { - if (mindepth > INT_MAX) { - mindepth = INT_MAX; - } - cmdline->mindepth = mindepth; - debug_opt(&state, "-O2: data flow: mindepth --> %d\n", cmdline->mindepth); - } - - if (optlevel >= 4 && maxdepth < cmdline->maxdepth) { - if (maxdepth < INT_MIN) { - maxdepth = INT_MIN; - } - cmdline->maxdepth = maxdepth; - debug_opt(&state, "-O4: data flow: maxdepth --> %d\n", cmdline->maxdepth); - } - - return 0; -} |