From 47e52194f339aeaca369ef31528e618b91390424 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Sun, 27 Mar 2022 13:17:39 -0400
Subject: opt: Add some more warnings

---
 opt.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/opt.c b/opt.c
index e82e3c1..e21a7ad 100644
--- a/opt.c
+++ b/opt.c
@@ -528,6 +528,7 @@ static struct bfs_expr *optimize_and_expr(const struct opt_state *state, struct
 			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);
@@ -539,6 +540,7 @@ static struct bfs_expr *optimize_and_expr(const struct opt_state *state, struct
 			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);
@@ -591,6 +593,7 @@ static struct bfs_expr *optimize_or_expr(const struct opt_state *state, struct b
 	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);
@@ -608,6 +611,7 @@ static struct bfs_expr *optimize_or_expr(const struct opt_state *state, struct b
 			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);
@@ -656,6 +660,7 @@ static struct bfs_expr *ignore_result(const struct opt_state *state, struct bfs_
 		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)
@@ -700,6 +705,7 @@ static struct bfs_expr *optimize_comma_expr(const struct opt_state *state, struc
 			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);
 		}
 	}
-- 
cgit v1.2.3