diff options
-rw-r--r-- | bfs.h | 4 | ||||
-rw-r--r-- | parse.c | 52 |
2 files changed, 42 insertions, 14 deletions
@@ -202,6 +202,10 @@ struct expr { /** Whether this expression has no side effects. */ bool pure; + /** Whether this expression always evaluates to true. */ + bool always_true; + /** Whether this expression always evaluates to false. */ + bool always_false; /** Number of times this predicate was executed. */ size_t evaluations; @@ -46,6 +46,7 @@ static struct expr expr_true = { .lhs = NULL, .rhs = NULL, .pure = true, + .always_true = true, .argc = 1, .argv = &fake_true_arg, }; @@ -58,6 +59,7 @@ static struct expr expr_false = { .lhs = NULL, .rhs = NULL, .pure = true, + .always_false = true, .argc = 1, .argv = &fake_false_arg, }; @@ -100,6 +102,8 @@ static struct expr *new_expr(eval_fn *eval, bool pure, size_t argc, char **argv) expr->lhs = NULL; expr->rhs = NULL; expr->pure = pure; + expr->always_true = false; + expr->always_false = false; expr->evaluations = 0; expr->successes = 0; expr->elapsed.tv_sec = 0; @@ -2124,7 +2128,12 @@ static struct expr *new_not_expr(const struct parser_state *state, struct expr * } } - return new_unary_expr(eval_not, rhs, argv); + struct expr *expr = new_unary_expr(eval_not, rhs, argv); + if (expr) { + expr->always_true = rhs->always_false; + expr->always_false = rhs->always_true; + } + return expr; } /** @@ -2188,14 +2197,14 @@ static struct expr *new_and_expr(const struct parser_state *state, struct expr * if (lhs == &expr_true) { debug_opt(state, "-O1: conjunction elimination: (%s %e %e) <==> %e\n", argv[0], lhs, rhs, rhs); return rhs; - } else if (lhs == &expr_false) { - debug_opt(state, "-O1: short-circuit: (%s %e %e) <==> %e\n", argv[0], lhs, rhs, lhs); - free_expr(rhs); - return lhs; } else if (rhs == &expr_true) { debug_opt(state, "-O1: conjunction elimination: (%s %e %e) <==> %e\n", argv[0], lhs, rhs, lhs); return lhs; - } else if (optlevel >= 2 && rhs == &expr_false && lhs->pure) { + } else if (lhs->always_false) { + debug_opt(state, "-O1: short-circuit: (%s %e %e) <==> %e\n", argv[0], lhs, rhs, lhs); + free_expr(rhs); + return lhs; + } else if (optlevel >= 2 && rhs->always_false && lhs->pure) { debug_opt(state, "-O2: purity: (%s %e %e) <==> %e\n", argv[0], lhs, rhs, rhs); free_expr(lhs); return rhs; @@ -2218,7 +2227,12 @@ static struct expr *new_and_expr(const struct parser_state *state, struct expr * } } - return new_binary_expr(eval_and, lhs, rhs, argv); + struct expr *expr = new_binary_expr(eval_and, lhs, rhs, argv); + if (expr) { + expr->always_true = lhs->always_true && rhs->always_true; + expr->always_false = lhs->always_false || rhs->always_false; + } + return expr; } /** @@ -2271,20 +2285,20 @@ static struct expr *parse_term(struct parser_state *state) { static struct expr *new_or_expr(const struct parser_state *state, struct expr *lhs, struct expr *rhs, char **argv) { int optlevel = state->cmdline->optlevel; if (optlevel >= 1) { - if (lhs == &expr_true) { + if (lhs->always_true) { debug_opt(state, "-O1: short-circuit: (%s %e %e) <==> %e\n", argv[0], lhs, rhs, lhs); free_expr(rhs); return lhs; } else if (lhs == &expr_false) { debug_opt(state, "-O1: disjunctive syllogism: (%s %e %e) <==> %e\n", argv[0], lhs, rhs, rhs); return rhs; - } else if (optlevel >= 2 && rhs == &expr_true && lhs->pure) { - debug_opt(state, "-O2: purity: (%s %e %e) <==> %e\n", argv[0], lhs, rhs, rhs); - free_expr(lhs); - return rhs; } else if (rhs == &expr_false) { debug_opt(state, "-O1: disjunctive syllogism: (%s %e %e) <==> %e\n", argv[0], lhs, rhs, lhs); return lhs; + } else if (optlevel >= 2 && rhs->always_true && lhs->pure) { + debug_opt(state, "-O2: purity: (%s %e %e) <==> %e\n", argv[0], lhs, rhs, rhs); + free_expr(lhs); + return rhs; } else if (lhs->eval == eval_not && rhs->eval == eval_not) { char **not_arg = lhs->argv; debug_opt(state, "-O1: De Morgan's laws: (%s %e %e) <==> (%s (%s %e %e))\n", @@ -2304,7 +2318,12 @@ static struct expr *new_or_expr(const struct parser_state *state, struct expr *l } } - return new_binary_expr(eval_or, lhs, rhs, argv); + struct expr *expr = new_binary_expr(eval_or, lhs, rhs, argv); + if (expr) { + expr->always_true = lhs->always_true || rhs->always_true; + expr->always_false = lhs->always_false && rhs->always_false; + } + return expr; } /** @@ -2369,7 +2388,12 @@ static struct expr *new_comma_expr(const struct parser_state *state, struct expr } } - return new_binary_expr(eval_comma, lhs, rhs, argv); + struct expr *expr = new_binary_expr(eval_comma, lhs, rhs, argv); + if (expr) { + expr->always_true = rhs->always_true; + expr->always_false = rhs->always_false; + } + return expr; } /** |