X-Git-Url: https://jxself.org/git/?p=carl9170fw.git;a=blobdiff_plain;f=config%2Fexpr.c;h=2ba332b3fed788f6bbdceb707b2a5bf8938feca1;hp=2b85ddf65aba4fb9119101aa8e58230161b36554;hb=51d27eb001f336dd8c665853383ad6f3b2498168;hpb=e72388a0aa23da8bc8e24a0cbe9d523c5a9ce294

diff --git a/config/expr.c b/config/expr.c
index 2b85ddf..2ba332b 100644
--- a/config/expr.c
+++ b/config/expr.c
@@ -7,15 +7,16 @@
 #include <stdlib.h>
 #include <string.h>
 
-#define LKC_DIRECT_LINK
 #include "lkc.h"
 
 #define DEBUG_EXPR	0
 
+static int expr_eq(struct expr *e1, struct expr *e2);
+static struct expr *expr_eliminate_yn(struct expr *e);
+
 struct expr *expr_alloc_symbol(struct symbol *sym)
 {
-	struct expr *e = malloc(sizeof(*e));
-	memset(e, 0, sizeof(*e));
+	struct expr *e = xcalloc(1, sizeof(*e));
 	e->type = E_SYMBOL;
 	e->left.sym = sym;
 	return e;
@@ -23,8 +24,7 @@ struct expr *expr_alloc_symbol(struct symbol *sym)
 
 struct expr *expr_alloc_one(enum expr_type type, struct expr *ce)
 {
-	struct expr *e = malloc(sizeof(*e));
-	memset(e, 0, sizeof(*e));
+	struct expr *e = xcalloc(1, sizeof(*e));
 	e->type = type;
 	e->left.expr = ce;
 	return e;
@@ -32,8 +32,7 @@ struct expr *expr_alloc_one(enum expr_type type, struct expr *ce)
 
 struct expr *expr_alloc_two(enum expr_type type, struct expr *e1, struct expr *e2)
 {
-	struct expr *e = malloc(sizeof(*e));
-	memset(e, 0, sizeof(*e));
+	struct expr *e = xcalloc(1, sizeof(*e));
 	e->type = type;
 	e->left.expr = e1;
 	e->right.expr = e2;
@@ -42,8 +41,7 @@ struct expr *expr_alloc_two(enum expr_type type, struct expr *e1, struct expr *e
 
 struct expr *expr_alloc_comp(enum expr_type type, struct symbol *s1, struct symbol *s2)
 {
-	struct expr *e = malloc(sizeof(*e));
-	memset(e, 0, sizeof(*e));
+	struct expr *e = xcalloc(1, sizeof(*e));
 	e->type = type;
 	e->left.sym = s1;
 	e->right.sym = s2;
@@ -64,14 +62,14 @@ struct expr *expr_alloc_or(struct expr *e1, struct expr *e2)
 	return e2 ? expr_alloc_two(E_OR, e1, e2) : e1;
 }
 
-struct expr *expr_copy(struct expr *org)
+struct expr *expr_copy(const struct expr *org)
 {
 	struct expr *e;
 
 	if (!org)
 		return NULL;
 
-	e = malloc(sizeof(*org));
+	e = xmalloc(sizeof(*org));
 	memcpy(e, org, sizeof(*org));
 	switch (org->type) {
 	case E_SYMBOL:
@@ -81,6 +79,10 @@ struct expr *expr_copy(struct expr *org)
 		e->left.expr = expr_copy(org->left.expr);
 		break;
 	case E_EQUAL:
+	case E_GEQ:
+	case E_GTH:
+	case E_LEQ:
+	case E_LTH:
 	case E_UNEQUAL:
 		e->left.sym = org->left.sym;
 		e->right.sym = org->right.sym;
@@ -111,8 +113,12 @@ void expr_free(struct expr *e)
 		break;
 	case E_NOT:
 		expr_free(e->left.expr);
-		return;
+		break;
 	case E_EQUAL:
+	case E_GEQ:
+	case E_GTH:
+	case E_LEQ:
+	case E_LTH:
 	case E_UNEQUAL:
 		break;
 	case E_OR:
@@ -132,8 +138,18 @@ static int trans_count;
 #define e1 (*ep1)
 #define e2 (*ep2)
 
+/*
+ * expr_eliminate_eq() helper.
+ *
+ * Walks the two expression trees given in 'ep1' and 'ep2'. Any node that does
+ * not have type 'type' (E_OR/E_AND) is considered a leaf, and is compared
+ * against all other leaves. Two equal leaves are both replaced with either 'y'
+ * or 'n' as appropriate for 'type', to be eliminated later.
+ */
 static void __expr_eliminate_eq(enum expr_type type, struct expr **ep1, struct expr **ep2)
 {
+	/* Recurse down to leaves */
+
 	if (e1->type == type) {
 		__expr_eliminate_eq(type, &e1->left.expr, &e2);
 		__expr_eliminate_eq(type, &e1->right.expr, &e2);
@@ -144,12 +160,18 @@ static void __expr_eliminate_eq(enum expr_type type, struct expr **ep1, struct e
 		__expr_eliminate_eq(type, &e1, &e2->right.expr);
 		return;
 	}
+
+	/* e1 and e2 are leaves. Compare them. */
+
 	if (e1->type == E_SYMBOL && e2->type == E_SYMBOL &&
 	    e1->left.sym == e2->left.sym &&
 	    (e1->left.sym == &symbol_yes || e1->left.sym == &symbol_no))
 		return;
 	if (!expr_eq(e1, e2))
 		return;
+
+	/* e1 and e2 are equal leaves. Prepare them for elimination. */
+
 	trans_count++;
 	expr_free(e1); expr_free(e2);
 	switch (type) {
@@ -166,6 +188,35 @@ static void __expr_eliminate_eq(enum expr_type type, struct expr **ep1, struct e
 	}
 }
 
+/*
+ * Rewrites the expressions 'ep1' and 'ep2' to remove operands common to both.
+ * Example reductions:
+ *
+ *	ep1: A && B           ->  ep1: y
+ *	ep2: A && B && C      ->  ep2: C
+ *
+ *	ep1: A || B           ->  ep1: n
+ *	ep2: A || B || C      ->  ep2: C
+ *
+ *	ep1: A && (B && FOO)  ->  ep1: FOO
+ *	ep2: (BAR && B) && A  ->  ep2: BAR
+ *
+ *	ep1: A && (B || C)    ->  ep1: y
+ *	ep2: (C || B) && A    ->  ep2: y
+ *
+ * Comparisons are done between all operands at the same "level" of && or ||.
+ * For example, in the expression 'e1 && (e2 || e3) && (e4 || e5)', the
+ * following operands will be compared:
+ *
+ *	- 'e1', 'e2 || e3', and 'e4 || e5', against each other
+ *	- e2 against e3
+ *	- e4 against e5
+ *
+ * Parentheses are irrelevant within a single level. 'e1 && (e2 && e3)' and
+ * '(e1 && e2) && e3' are both a single level.
+ *
+ * See __expr_eliminate_eq() as well.
+ */
 void expr_eliminate_eq(struct expr **ep1, struct expr **ep2)
 {
 	if (!e1 || !e2)
@@ -177,18 +228,13 @@ void expr_eliminate_eq(struct expr **ep1, struct expr **ep2)
 	default:
 		;
 	}
-
-	if (e1->type != e2->type) {
-		switch (e2->type) {
-		case E_OR:
-		case E_AND:
-			__expr_eliminate_eq(e2->type, ep1, ep2);
-		default:
-			;
-
-		}
+	if (e1->type != e2->type) switch (e2->type) {
+	case E_OR:
+	case E_AND:
+		__expr_eliminate_eq(e2->type, ep1, ep2);
+	default:
+		;
 	}
-
 	e1 = expr_eliminate_yn(e1);
 	e2 = expr_eliminate_yn(e2);
 }
@@ -196,7 +242,13 @@ void expr_eliminate_eq(struct expr **ep1, struct expr **ep2)
 #undef e1
 #undef e2
 
-int expr_eq(struct expr *e1, struct expr *e2)
+/*
+ * Returns true if 'e1' and 'e2' are equal, after minor simplification. Two
+ * &&/|| expressions are considered equal if every operand in one expression
+ * equals some operand in the other (operands do not need to appear in the same
+ * order), recursively.
+ */
+static int expr_eq(struct expr *e1, struct expr *e2)
 {
 	int res, old_count;
 
@@ -204,6 +256,10 @@ int expr_eq(struct expr *e1, struct expr *e2)
 		return 0;
 	switch (e1->type) {
 	case E_EQUAL:
+	case E_GEQ:
+	case E_GTH:
+	case E_LEQ:
+	case E_LTH:
 	case E_UNEQUAL:
 		return e1->left.sym == e2->left.sym && e1->right.sym == e2->right.sym;
 	case E_SYMBOL:
@@ -238,14 +294,22 @@ int expr_eq(struct expr *e1, struct expr *e2)
 	return 0;
 }
 
-struct expr *expr_eliminate_yn(struct expr *e)
+/*
+ * Recursively performs the following simplifications in-place (as well as the
+ * corresponding simplifications with swapped operands):
+ *
+ *	expr && n  ->  n
+ *	expr && y  ->  expr
+ *	expr || n  ->  expr
+ *	expr || y  ->  y
+ *
+ * Returns the optimized expression.
+ */
+static struct expr *expr_eliminate_yn(struct expr *e)
 {
 	struct expr *tmp;
 
-	if (!e)
-		return NULL;
-
-	switch (e->type) {
+	if (e) switch (e->type) {
 	case E_AND:
 		e->left.expr = expr_eliminate_yn(e->left.expr);
 		e->right.expr = expr_eliminate_yn(e->right.expr);
@@ -265,7 +329,6 @@ struct expr *expr_eliminate_yn(struct expr *e)
 				return e;
 			}
 		}
-
 		if (e->right.expr->type == E_SYMBOL) {
 			if (e->right.expr->left.sym == &symbol_no) {
 				expr_free(e->left.expr);
@@ -283,7 +346,6 @@ struct expr *expr_eliminate_yn(struct expr *e)
 			}
 		}
 		break;
-
 	case E_OR:
 		e->left.expr = expr_eliminate_yn(e->left.expr);
 		e->right.expr = expr_eliminate_yn(e->right.expr);
@@ -303,7 +365,6 @@ struct expr *expr_eliminate_yn(struct expr *e)
 				return e;
 			}
 		}
-
 		if (e->right.expr->type == E_SYMBOL) {
 			if (e->right.expr->left.sym == &symbol_no) {
 				free(e->right.expr);
@@ -322,7 +383,7 @@ struct expr *expr_eliminate_yn(struct expr *e)
 		}
 		break;
 	default:
-		break;
+		;
 	}
 	return e;
 }
@@ -334,7 +395,6 @@ struct expr *expr_trans_bool(struct expr *e)
 {
 	if (!e)
 		return NULL;
-
 	switch (e->type) {
 	case E_AND:
 	case E_OR:
@@ -343,7 +403,7 @@ struct expr *expr_trans_bool(struct expr *e)
 		e->right.expr = expr_trans_bool(e->right.expr);
 		break;
 	case E_UNEQUAL:
-		/* FOO!=n -> FOO */
+		// FOO!=n -> FOO
 		if (e->left.sym->type == S_TRISTATE) {
 			if (e->right.sym == &symbol_no) {
 				e->type = E_SYMBOL;
@@ -392,19 +452,19 @@ static struct expr *expr_join_or(struct expr *e1, struct expr *e2)
 		if (e1->type == E_EQUAL && e2->type == E_EQUAL &&
 		    ((e1->right.sym == &symbol_yes && e2->right.sym == &symbol_mod) ||
 		     (e1->right.sym == &symbol_mod && e2->right.sym == &symbol_yes))) {
-			/* (a='y') || (a='m') -> (a!='n') */
+			// (a='y') || (a='m') -> (a!='n')
 			return expr_alloc_comp(E_UNEQUAL, sym1, &symbol_no);
 		}
 		if (e1->type == E_EQUAL && e2->type == E_EQUAL &&
 		    ((e1->right.sym == &symbol_yes && e2->right.sym == &symbol_no) ||
 		     (e1->right.sym == &symbol_no && e2->right.sym == &symbol_yes))) {
-			/* (a='y') || (a='n') -> (a!='m') */
+			// (a='y') || (a='n') -> (a!='m')
 			return expr_alloc_comp(E_UNEQUAL, sym1, &symbol_mod);
 		}
 		if (e1->type == E_EQUAL && e2->type == E_EQUAL &&
 		    ((e1->right.sym == &symbol_mod && e2->right.sym == &symbol_no) ||
 		     (e1->right.sym == &symbol_no && e2->right.sym == &symbol_mod))) {
-			/* (a='m') || (a='n') -> (a!='y') */
+			// (a='m') || (a='n') -> (a!='y')
 			return expr_alloc_comp(E_UNEQUAL, sym1, &symbol_yes);
 		}
 	}
@@ -455,29 +515,29 @@ static struct expr *expr_join_and(struct expr *e1, struct expr *e2)
 
 	if ((e1->type == E_SYMBOL && e2->type == E_EQUAL && e2->right.sym == &symbol_yes) ||
 	    (e2->type == E_SYMBOL && e1->type == E_EQUAL && e1->right.sym == &symbol_yes))
-		/* (a) && (a='y') -> (a='y') */
+		// (a) && (a='y') -> (a='y')
 		return expr_alloc_comp(E_EQUAL, sym1, &symbol_yes);
 
 	if ((e1->type == E_SYMBOL && e2->type == E_UNEQUAL && e2->right.sym == &symbol_no) ||
 	    (e2->type == E_SYMBOL && e1->type == E_UNEQUAL && e1->right.sym == &symbol_no))
-		/* (a) && (a!='n') -> (a) */
+		// (a) && (a!='n') -> (a)
 		return expr_alloc_symbol(sym1);
 
 	if ((e1->type == E_SYMBOL && e2->type == E_UNEQUAL && e2->right.sym == &symbol_mod) ||
 	    (e2->type == E_SYMBOL && e1->type == E_UNEQUAL && e1->right.sym == &symbol_mod))
-		/* (a) && (a!='m') -> (a='y') */
+		// (a) && (a!='m') -> (a='y')
 		return expr_alloc_comp(E_EQUAL, sym1, &symbol_yes);
 
 	if (sym1->type == S_TRISTATE) {
 		if (e1->type == E_EQUAL && e2->type == E_UNEQUAL) {
-			/* (a='b') && (a!='c') -> 'b'='c' ? 'n' : a='b' */
+			// (a='b') && (a!='c') -> 'b'='c' ? 'n' : a='b'
 			sym2 = e1->right.sym;
 			if ((e2->right.sym->flags & SYMBOL_CONST) && (sym2->flags & SYMBOL_CONST))
 				return sym2 != e2->right.sym ? expr_alloc_comp(E_EQUAL, sym1, sym2)
 							     : expr_alloc_symbol(&symbol_no);
 		}
 		if (e1->type == E_UNEQUAL && e2->type == E_EQUAL) {
-			/* (a='b') && (a!='c') -> 'b'='c' ? 'n' : a='b' */
+			// (a='b') && (a!='c') -> 'b'='c' ? 'n' : a='b'
 			sym2 = e2->right.sym;
 			if ((e1->right.sym->flags & SYMBOL_CONST) && (sym2->flags & SYMBOL_CONST))
 				return sym2 != e1->right.sym ? expr_alloc_comp(E_EQUAL, sym1, sym2)
@@ -486,19 +546,19 @@ static struct expr *expr_join_and(struct expr *e1, struct expr *e2)
 		if (e1->type == E_UNEQUAL && e2->type == E_UNEQUAL &&
 			   ((e1->right.sym == &symbol_yes && e2->right.sym == &symbol_no) ||
 			    (e1->right.sym == &symbol_no && e2->right.sym == &symbol_yes)))
-			/* (a!='y') && (a!='n') -> (a='m') */
+			// (a!='y') && (a!='n') -> (a='m')
 			return expr_alloc_comp(E_EQUAL, sym1, &symbol_mod);
 
 		if (e1->type == E_UNEQUAL && e2->type == E_UNEQUAL &&
 			   ((e1->right.sym == &symbol_yes && e2->right.sym == &symbol_mod) ||
 			    (e1->right.sym == &symbol_mod && e2->right.sym == &symbol_yes)))
-			/* (a!='y') && (a!='m') -> (a='n') */
+			// (a!='y') && (a!='m') -> (a='n')
 			return expr_alloc_comp(E_EQUAL, sym1, &symbol_no);
 
 		if (e1->type == E_UNEQUAL && e2->type == E_UNEQUAL &&
 			   ((e1->right.sym == &symbol_mod && e2->right.sym == &symbol_no) ||
 			    (e1->right.sym == &symbol_no && e2->right.sym == &symbol_mod)))
-			/* (a!='m') && (a!='n') -> (a='m') */
+			// (a!='m') && (a!='n') -> (a='m')
 			return expr_alloc_comp(E_EQUAL, sym1, &symbol_yes);
 
 		if ((e1->type == E_SYMBOL && e2->type == E_EQUAL && e2->right.sym == &symbol_mod) ||
@@ -518,12 +578,21 @@ static struct expr *expr_join_and(struct expr *e1, struct expr *e2)
 	return NULL;
 }
 
+/*
+ * expr_eliminate_dups() helper.
+ *
+ * Walks the two expression trees given in 'ep1' and 'ep2'. Any node that does
+ * not have type 'type' (E_OR/E_AND) is considered a leaf, and is compared
+ * against all other leaves to look for simplifications.
+ */
 static void expr_eliminate_dups1(enum expr_type type, struct expr **ep1, struct expr **ep2)
 {
 #define e1 (*ep1)
 #define e2 (*ep2)
 	struct expr *tmp;
 
+	/* Recurse down to leaves */
+
 	if (e1->type == type) {
 		expr_eliminate_dups1(type, &e1->left.expr, &e2);
 		expr_eliminate_dups1(type, &e1->right.expr, &e2);
@@ -534,6 +603,9 @@ static void expr_eliminate_dups1(enum expr_type type, struct expr **ep1, struct
 		expr_eliminate_dups1(type, &e1, &e2->right.expr);
 		return;
 	}
+
+	/* e1 and e2 are leaves. Compare and process them. */
+
 	if (e1 == e2)
 		return;
 
@@ -570,62 +642,17 @@ static void expr_eliminate_dups1(enum expr_type type, struct expr **ep1, struct
 #undef e2
 }
 
-static void expr_eliminate_dups2(enum expr_type type, struct expr **ep1, struct expr **ep2)
-{
-#define e1 (*ep1)
-#define e2 (*ep2)
-	struct expr *tmp, *tmp1, *tmp2;
-
-	if (e1->type == type) {
-		expr_eliminate_dups2(type, &e1->left.expr, &e2);
-		expr_eliminate_dups2(type, &e1->right.expr, &e2);
-		return;
-	}
-	if (e2->type == type) {
-		expr_eliminate_dups2(type, &e1, &e2->left.expr);
-		expr_eliminate_dups2(type, &e1, &e2->right.expr);
-	}
-	if (e1 == e2)
-		return;
-
-	switch (e1->type) {
-	case E_OR:
-		expr_eliminate_dups2(e1->type, &e1, &e1);
-		/* (FOO || BAR) && (!FOO && !BAR) -> n */
-		tmp1 = expr_transform(expr_alloc_one(E_NOT, expr_copy(e1)));
-		tmp2 = expr_copy(e2);
-		tmp = expr_extract_eq_and(&tmp1, &tmp2);
-		if (expr_is_yes(tmp1)) {
-			expr_free(e1);
-			e1 = expr_alloc_symbol(&symbol_no);
-			trans_count++;
-		}
-		expr_free(tmp2);
-		expr_free(tmp1);
-		expr_free(tmp);
-		break;
-	case E_AND:
-		expr_eliminate_dups2(e1->type, &e1, &e1);
-		/* (FOO && BAR) || (!FOO || !BAR) -> y */
-		tmp1 = expr_transform(expr_alloc_one(E_NOT, expr_copy(e1)));
-		tmp2 = expr_copy(e2);
-		tmp = expr_extract_eq_or(&tmp1, &tmp2);
-		if (expr_is_no(tmp1)) {
-			expr_free(e1);
-			e1 = expr_alloc_symbol(&symbol_yes);
-			trans_count++;
-		}
-		expr_free(tmp2);
-		expr_free(tmp1);
-		expr_free(tmp);
-		break;
-	default:
-		;
-	}
-#undef e1
-#undef e2
-}
-
+/*
+ * Rewrites 'e' in-place to remove ("join") duplicate and other redundant
+ * operands.
+ *
+ * Example simplifications:
+ *
+ *	A || B || A    ->  A || B
+ *	A && B && A=y  ->  A=y && B
+ *
+ * Returns the deduplicated expression.
+ */
 struct expr *expr_eliminate_dups(struct expr *e)
 {
 	int oldcount;
@@ -638,11 +665,11 @@ struct expr *expr_eliminate_dups(struct expr *e)
 		switch (e->type) {
 		case E_OR: case E_AND:
 			expr_eliminate_dups1(e->type, &e, &e);
-			expr_eliminate_dups2(e->type, &e, &e);
 		default:
 			;
 		}
 		if (!trans_count)
+			/* No simplifications done in this pass. We're done */
 			break;
 		e = expr_eliminate_yn(e);
 	}
@@ -650,6 +677,12 @@ struct expr *expr_eliminate_dups(struct expr *e)
 	return e;
 }
 
+/*
+ * Performs various simplifications involving logical operators and
+ * comparisons.
+ *
+ * Allocates and returns a new expression.
+ */
 struct expr *expr_transform(struct expr *e)
 {
 	struct expr *tmp;
@@ -658,6 +691,10 @@ struct expr *expr_transform(struct expr *e)
 		return NULL;
 	switch (e->type) {
 	case E_EQUAL:
+	case E_GEQ:
+	case E_GTH:
+	case E_LEQ:
+	case E_LTH:
 	case E_UNEQUAL:
 	case E_SYMBOL:
 	case E_LIST:
@@ -715,7 +752,7 @@ struct expr *expr_transform(struct expr *e)
 	case E_NOT:
 		switch (e->left.expr->type) {
 		case E_NOT:
-			/* !!a -> a */
+			// !!a -> a
 			tmp = e->left.expr->left.expr;
 			free(e->left.expr);
 			free(e);
@@ -724,14 +761,30 @@ struct expr *expr_transform(struct expr *e)
 			break;
 		case E_EQUAL:
 		case E_UNEQUAL:
-			/* !a='x' -> a!='x' */
+			// !a='x' -> a!='x'
 			tmp = e->left.expr;
 			free(e);
 			e = tmp;
 			e->type = e->type == E_EQUAL ? E_UNEQUAL : E_EQUAL;
 			break;
+		case E_LEQ:
+		case E_GEQ:
+			// !a<='x' -> a>'x'
+			tmp = e->left.expr;
+			free(e);
+			e = tmp;
+			e->type = e->type == E_LEQ ? E_GTH : E_LTH;
+			break;
+		case E_LTH:
+		case E_GTH:
+			// !a<'x' -> a>='x'
+			tmp = e->left.expr;
+			free(e);
+			e = tmp;
+			e->type = e->type == E_LTH ? E_GEQ : E_LEQ;
+			break;
 		case E_OR:
-			/* !(a || b) -> !a && !b */
+			// !(a || b) -> !a && !b
 			tmp = e->left.expr;
 			e->type = E_AND;
 			e->right.expr = expr_alloc_one(E_NOT, tmp->right.expr);
@@ -740,7 +793,7 @@ struct expr *expr_transform(struct expr *e)
 			e = expr_transform(e);
 			break;
 		case E_AND:
-			/* !(a && b) -> !a || !b */
+			// !(a && b) -> !a || !b
 			tmp = e->left.expr;
 			e->type = E_OR;
 			e->right.expr = expr_alloc_one(E_NOT, tmp->right.expr);
@@ -750,7 +803,7 @@ struct expr *expr_transform(struct expr *e)
 			break;
 		case E_SYMBOL:
 			if (e->left.expr->left.sym == &symbol_yes) {
-				/* !'y' -> 'n' */
+				// !'y' -> 'n'
 				tmp = e->left.expr;
 				free(e);
 				e = tmp;
@@ -759,7 +812,7 @@ struct expr *expr_transform(struct expr *e)
 				break;
 			}
 			if (e->left.expr->left.sym == &symbol_mod) {
-				/* !'m' -> 'm' */
+				// !'m' -> 'm'
 				tmp = e->left.expr;
 				free(e);
 				e = tmp;
@@ -768,7 +821,7 @@ struct expr *expr_transform(struct expr *e)
 				break;
 			}
 			if (e->left.expr->left.sym == &symbol_no) {
-				/* !'n' -> 'y' */
+				// !'n' -> 'y'
 				tmp = e->left.expr;
 				free(e);
 				e = tmp;
@@ -800,6 +853,10 @@ int expr_contains_symbol(struct expr *dep, struct symbol *sym)
 	case E_SYMBOL:
 		return dep->left.sym == sym;
 	case E_EQUAL:
+	case E_GEQ:
+	case E_GTH:
+	case E_LEQ:
+	case E_LTH:
 	case E_UNEQUAL:
 		return dep->left.sym == sym ||
 		       dep->right.sym == sym;
@@ -837,60 +894,23 @@ bool expr_depends_symbol(struct expr *dep, struct symbol *sym)
 	default:
 		;
 	}
-	return false;
-}
-
-struct expr *expr_extract_eq_and(struct expr **ep1, struct expr **ep2)
-{
-	struct expr *tmp = NULL;
-	expr_extract_eq(E_AND, &tmp, ep1, ep2);
-	if (tmp) {
-		*ep1 = expr_eliminate_yn(*ep1);
-		*ep2 = expr_eliminate_yn(*ep2);
-	}
-	return tmp;
-}
-
-struct expr *expr_extract_eq_or(struct expr **ep1, struct expr **ep2)
-{
-	struct expr *tmp = NULL;
-	expr_extract_eq(E_OR, &tmp, ep1, ep2);
-	if (tmp) {
-		*ep1 = expr_eliminate_yn(*ep1);
-		*ep2 = expr_eliminate_yn(*ep2);
-	}
-	return tmp;
-}
-
-void expr_extract_eq(enum expr_type type, struct expr **ep, struct expr **ep1, struct expr **ep2)
-{
-#define e1 (*ep1)
-#define e2 (*ep2)
-	if (e1->type == type) {
-		expr_extract_eq(type, ep, &e1->left.expr, &e2);
-		expr_extract_eq(type, ep, &e1->right.expr, &e2);
-		return;
-	}
-	if (e2->type == type) {
-		expr_extract_eq(type, ep, ep1, &e2->left.expr);
-		expr_extract_eq(type, ep, ep1, &e2->right.expr);
-		return;
-	}
-	if (expr_eq(e1, e2)) {
-		*ep = *ep ? expr_alloc_two(type, *ep, e1) : e1;
-		expr_free(e2);
-		if (type == E_AND) {
-			e1 = expr_alloc_symbol(&symbol_yes);
-			e2 = expr_alloc_symbol(&symbol_yes);
-		} else if (type == E_OR) {
-			e1 = expr_alloc_symbol(&symbol_no);
-			e2 = expr_alloc_symbol(&symbol_no);
-		}
-	}
-#undef e1
-#undef e2
+ 	return false;
 }
 
+/*
+ * Inserts explicit comparisons of type 'type' to symbol 'sym' into the
+ * expression 'e'.
+ *
+ * Examples transformations for type == E_UNEQUAL, sym == &symbol_no:
+ *
+ *	A              ->  A!=n
+ *	!A             ->  A=n
+ *	A && B         ->  !(A=n || B=n)
+ *	A || B         ->  !(A=n && B=n)
+ *	A && (B || C)  ->  !(A=n || (B=n && C=n))
+ *
+ * Allocates and returns a new expression.
+ */
 struct expr *expr_trans_compare(struct expr *e, enum expr_type type, struct symbol *sym)
 {
 	struct expr *e1, *e2;
@@ -925,6 +945,10 @@ struct expr *expr_trans_compare(struct expr *e, enum expr_type type, struct symb
 	case E_NOT:
 		return expr_trans_compare(e->left.expr, type == E_EQUAL ? E_UNEQUAL : E_EQUAL, sym);
 	case E_UNEQUAL:
+	case E_LTH:
+	case E_LEQ:
+	case E_GTH:
+	case E_GEQ:
 	case E_EQUAL:
 		if (type == E_EQUAL) {
 			if (sym == &symbol_yes)
@@ -952,10 +976,60 @@ struct expr *expr_trans_compare(struct expr *e, enum expr_type type, struct symb
 	return NULL;
 }
 
+enum string_value_kind {
+	k_string,
+	k_signed,
+	k_unsigned,
+	k_invalid
+};
+
+union string_value {
+	unsigned long long u;
+	signed long long s;
+};
+
+static enum string_value_kind expr_parse_string(const char *str,
+						enum symbol_type type,
+						union string_value *val)
+{
+	char *tail;
+	enum string_value_kind kind;
+
+	errno = 0;
+	switch (type) {
+	case S_BOOLEAN:
+	case S_TRISTATE:
+		val->s = !strcmp(str, "n") ? 0 :
+			 !strcmp(str, "m") ? 1 :
+			 !strcmp(str, "y") ? 2 : -1;
+		return k_signed;
+	case S_INT:
+		val->s = strtoll(str, &tail, 10);
+		kind = k_signed;
+		break;
+	case S_HEX:
+		val->u = strtoull(str, &tail, 16);
+		kind = k_unsigned;
+		break;
+	case S_STRING:
+	case S_UNKNOWN:
+		val->s = strtoll(str, &tail, 0);
+		kind = k_signed;
+		break;
+	default:
+		return k_invalid;
+	}
+	return !errno && !*tail && tail > str && isxdigit(tail[-1])
+	       ? kind : k_string;
+}
+
 tristate expr_calc_value(struct expr *e)
 {
 	tristate val1, val2;
 	const char *str1, *str2;
+	enum string_value_kind k1 = k_string, k2 = k_string;
+	union string_value lval = {}, rval = {};
+	int res;
 
 	if (!e)
 		return yes;
@@ -976,31 +1050,70 @@ tristate expr_calc_value(struct expr *e)
 		val1 = expr_calc_value(e->left.expr);
 		return EXPR_NOT(val1);
 	case E_EQUAL:
-		sym_calc_value(e->left.sym);
-		sym_calc_value(e->right.sym);
-		str1 = sym_get_string_value(e->left.sym);
-		str2 = sym_get_string_value(e->right.sym);
-		return !strcmp(str1, str2) ? yes : no;
+	case E_GEQ:
+	case E_GTH:
+	case E_LEQ:
+	case E_LTH:
 	case E_UNEQUAL:
-		sym_calc_value(e->left.sym);
-		sym_calc_value(e->right.sym);
-		str1 = sym_get_string_value(e->left.sym);
-		str2 = sym_get_string_value(e->right.sym);
-		return !strcmp(str1, str2) ? no : yes;
+		break;
 	default:
 		printf("expr_calc_value: %d?\n", e->type);
 		return no;
 	}
+
+	sym_calc_value(e->left.sym);
+	sym_calc_value(e->right.sym);
+	str1 = sym_get_string_value(e->left.sym);
+	str2 = sym_get_string_value(e->right.sym);
+
+	if (e->left.sym->type != S_STRING || e->right.sym->type != S_STRING) {
+		k1 = expr_parse_string(str1, e->left.sym->type, &lval);
+		k2 = expr_parse_string(str2, e->right.sym->type, &rval);
+	}
+
+	if (k1 == k_string || k2 == k_string)
+		res = strcmp(str1, str2);
+	else if (k1 == k_invalid || k2 == k_invalid) {
+		if (e->type != E_EQUAL && e->type != E_UNEQUAL) {
+			printf("Cannot compare \"%s\" and \"%s\"\n", str1, str2);
+			return no;
+		}
+		res = strcmp(str1, str2);
+	} else if (k1 == k_unsigned || k2 == k_unsigned)
+		res = (lval.u > rval.u) - (lval.u < rval.u);
+	else /* if (k1 == k_signed && k2 == k_signed) */
+		res = (lval.s > rval.s) - (lval.s < rval.s);
+
+	switch(e->type) {
+	case E_EQUAL:
+		return res ? no : yes;
+	case E_GEQ:
+		return res >= 0 ? yes : no;
+	case E_GTH:
+		return res > 0 ? yes : no;
+	case E_LEQ:
+		return res <= 0 ? yes : no;
+	case E_LTH:
+		return res < 0 ? yes : no;
+	case E_UNEQUAL:
+		return res ? yes : no;
+	default:
+		printf("expr_calc_value: relation %d?\n", e->type);
+		return no;
+	}
 }
 
-int expr_compare_type(enum expr_type t1, enum expr_type t2)
+static int expr_compare_type(enum expr_type t1, enum expr_type t2)
 {
-#if 0
-	return 1;
-#else
 	if (t1 == t2)
 		return 0;
 	switch (t1) {
+	case E_LEQ:
+	case E_LTH:
+	case E_GEQ:
+	case E_GTH:
+		if (t2 == E_EQUAL || t2 == E_UNEQUAL)
+			return 1;
 	case E_EQUAL:
 	case E_UNEQUAL:
 		if (t2 == E_NOT)
@@ -1022,10 +1135,51 @@ int expr_compare_type(enum expr_type t1, enum expr_type t2)
 	}
 	printf("[%dgt%d?]", t1, t2);
 	return 0;
-#endif
 }
 
-void expr_print(struct expr *e, void (*fn)(void *, struct symbol *, const char *), void *data, int prevtoken)
+static inline struct expr *
+expr_get_leftmost_symbol(const struct expr *e)
+{
+
+	if (e == NULL)
+		return NULL;
+
+	while (e->type != E_SYMBOL)
+		e = e->left.expr;
+
+	return expr_copy(e);
+}
+
+/*
+ * Given expression `e1' and `e2', returns the leaf of the longest
+ * sub-expression of `e1' not containing 'e2.
+ */
+struct expr *expr_simplify_unmet_dep(struct expr *e1, struct expr *e2)
+{
+	struct expr *ret;
+
+	switch (e1->type) {
+	case E_OR:
+		return expr_alloc_and(
+		    expr_simplify_unmet_dep(e1->left.expr, e2),
+		    expr_simplify_unmet_dep(e1->right.expr, e2));
+	case E_AND: {
+		struct expr *e;
+		e = expr_alloc_and(expr_copy(e1), expr_copy(e2));
+		e = expr_eliminate_dups(e);
+		ret = (!expr_eq(e, e1)) ? e1 : NULL;
+		expr_free(e);
+		break;
+		}
+	default:
+		ret = e1;
+		break;
+	}
+
+	return expr_get_leftmost_symbol(ret);
+}
+
+static void __expr_print(struct expr *e, void (*fn)(void *, struct symbol *, const char *), void *data, int prevtoken, bool revdep)
 {
 	if (!e) {
 		fn(data, NULL, "y");
@@ -1053,6 +1207,24 @@ void expr_print(struct expr *e, void (*fn)(void *, struct symbol *, const char *
 		fn(data, NULL, "=");
 		fn(data, e->right.sym, e->right.sym->name);
 		break;
+	case E_LEQ:
+	case E_LTH:
+		if (e->left.sym->name)
+			fn(data, e->left.sym, e->left.sym->name);
+		else
+			fn(data, NULL, "<choice>");
+		fn(data, NULL, e->type == E_LEQ ? "<=" : "<");
+		fn(data, e->right.sym, e->right.sym->name);
+		break;
+	case E_GEQ:
+	case E_GTH:
+		if (e->left.sym->name)
+			fn(data, e->left.sym, e->left.sym->name);
+		else
+			fn(data, NULL, "<choice>");
+		fn(data, NULL, e->type == E_GEQ ? ">=" : ">");
+		fn(data, e->right.sym, e->right.sym->name);
+		break;
 	case E_UNEQUAL:
 		if (e->left.sym->name)
 			fn(data, e->left.sym, e->left.sym->name);
@@ -1062,9 +1234,14 @@ void expr_print(struct expr *e, void (*fn)(void *, struct symbol *, const char *
 		fn(data, e->right.sym, e->right.sym->name);
 		break;
 	case E_OR:
-		expr_print(e->left.expr, fn, data, E_OR);
-		fn(data, NULL, " || ");
-		expr_print(e->right.expr, fn, data, E_OR);
+		if (revdep && e->left.expr->type != E_OR)
+			fn(data, NULL, "\n  - ");
+		__expr_print(e->left.expr, fn, data, E_OR, revdep);
+		if (revdep)
+			fn(data, NULL, "\n  - ");
+		else
+			fn(data, NULL, " || ");
+		__expr_print(e->right.expr, fn, data, E_OR, revdep);
 		break;
 	case E_AND:
 		expr_print(e->left.expr, fn, data, E_AND);
@@ -1097,9 +1274,14 @@ void expr_print(struct expr *e, void (*fn)(void *, struct symbol *, const char *
 		fn(data, NULL, ")");
 }
 
+void expr_print(struct expr *e, void (*fn)(void *, struct symbol *, const char *), void *data, int prevtoken)
+{
+	__expr_print(e, fn, data, prevtoken, false);
+}
+
 static void expr_print_file_helper(void *data, struct symbol *sym, const char *str)
 {
-	fwrite(str, strlen(str), 1, data);
+	xfwrite(str, strlen(str), 1, data);
 }
 
 void expr_fprint(struct expr *e, FILE *out)
@@ -1109,12 +1291,45 @@ void expr_fprint(struct expr *e, FILE *out)
 
 static void expr_print_gstr_helper(void *data, struct symbol *sym, const char *str)
 {
-	str_append((struct gstr *)data, str);
+	struct gstr *gs = (struct gstr*)data;
+	const char *sym_str = NULL;
+
 	if (sym)
-		str_printf((struct gstr *)data, " [=%s]", sym_get_string_value(sym));
+		sym_str = sym_get_string_value(sym);
+
+	if (gs->max_width) {
+		unsigned extra_length = strlen(str);
+		const char *last_cr = strrchr(gs->s, '\n');
+		unsigned last_line_length;
+
+		if (sym_str)
+			extra_length += 4 + strlen(sym_str);
+
+		if (!last_cr)
+			last_cr = gs->s;
+
+		last_line_length = strlen(gs->s) - (last_cr - gs->s);
+
+		if ((last_line_length + extra_length) > gs->max_width)
+			str_append(gs, "\\\n");
+	}
+
+	str_append(gs, str);
+	if (sym && sym->type != S_UNKNOWN)
+		str_printf(gs, " [=%s]", sym_str);
 }
 
 void expr_gstr_print(struct expr *e, struct gstr *gs)
 {
 	expr_print(e, expr_print_gstr_helper, gs, E_NONE);
 }
+
+/*
+ * Transform the top level "||" tokens into newlines and prepend each
+ * line with a minus. This makes expressions much easier to read.
+ * Suitable for reverse dependency expressions.
+ */
+void expr_gstr_print_revdep(struct expr *e, struct gstr *gs)
+{
+	__expr_print(e, expr_print_gstr_helper, gs, E_NONE, true);
+}