Initial commit of Kconfig build tool.
[seabios.git] / tools / kconfig / expr.c
diff --git a/tools/kconfig/expr.c b/tools/kconfig/expr.c
new file mode 100644 (file)
index 0000000..0010034
--- /dev/null
@@ -0,0 +1,1173 @@
+/*
+ * Copyright (C) 2002 Roman Zippel <zippel@linux-m68k.org>
+ * Released under the terms of the GNU GPL v2.0.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define LKC_DIRECT_LINK
+#include "lkc.h"
+
+#define DEBUG_EXPR     0
+
+struct expr *expr_alloc_symbol(struct symbol *sym)
+{
+       struct expr *e = malloc(sizeof(*e));
+       memset(e, 0, sizeof(*e));
+       e->type = E_SYMBOL;
+       e->left.sym = sym;
+       return e;
+}
+
+struct expr *expr_alloc_one(enum expr_type type, struct expr *ce)
+{
+       struct expr *e = malloc(sizeof(*e));
+       memset(e, 0, sizeof(*e));
+       e->type = type;
+       e->left.expr = ce;
+       return e;
+}
+
+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));
+       e->type = type;
+       e->left.expr = e1;
+       e->right.expr = e2;
+       return 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));
+       e->type = type;
+       e->left.sym = s1;
+       e->right.sym = s2;
+       return e;
+}
+
+struct expr *expr_alloc_and(struct expr *e1, struct expr *e2)
+{
+       if (!e1)
+               return e2;
+       return e2 ? expr_alloc_two(E_AND, e1, e2) : e1;
+}
+
+struct expr *expr_alloc_or(struct expr *e1, struct expr *e2)
+{
+       if (!e1)
+               return e2;
+       return e2 ? expr_alloc_two(E_OR, e1, e2) : e1;
+}
+
+struct expr *expr_copy(const struct expr *org)
+{
+       struct expr *e;
+
+       if (!org)
+               return NULL;
+
+       e = malloc(sizeof(*org));
+       memcpy(e, org, sizeof(*org));
+       switch (org->type) {
+       case E_SYMBOL:
+               e->left = org->left;
+               break;
+       case E_NOT:
+               e->left.expr = expr_copy(org->left.expr);
+               break;
+       case E_EQUAL:
+       case E_UNEQUAL:
+               e->left.sym = org->left.sym;
+               e->right.sym = org->right.sym;
+               break;
+       case E_AND:
+       case E_OR:
+       case E_LIST:
+               e->left.expr = expr_copy(org->left.expr);
+               e->right.expr = expr_copy(org->right.expr);
+               break;
+       default:
+               printf("can't copy type %d\n", e->type);
+               free(e);
+               e = NULL;
+               break;
+       }
+
+       return e;
+}
+
+void expr_free(struct expr *e)
+{
+       if (!e)
+               return;
+
+       switch (e->type) {
+       case E_SYMBOL:
+               break;
+       case E_NOT:
+               expr_free(e->left.expr);
+               return;
+       case E_EQUAL:
+       case E_UNEQUAL:
+               break;
+       case E_OR:
+       case E_AND:
+               expr_free(e->left.expr);
+               expr_free(e->right.expr);
+               break;
+       default:
+               printf("how to free type %d?\n", e->type);
+               break;
+       }
+       free(e);
+}
+
+static int trans_count;
+
+#define e1 (*ep1)
+#define e2 (*ep2)
+
+static void __expr_eliminate_eq(enum expr_type type, struct expr **ep1, struct expr **ep2)
+{
+       if (e1->type == type) {
+               __expr_eliminate_eq(type, &e1->left.expr, &e2);
+               __expr_eliminate_eq(type, &e1->right.expr, &e2);
+               return;
+       }
+       if (e2->type == type) {
+               __expr_eliminate_eq(type, &e1, &e2->left.expr);
+               __expr_eliminate_eq(type, &e1, &e2->right.expr);
+               return;
+       }
+       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;
+       trans_count++;
+       expr_free(e1); expr_free(e2);
+       switch (type) {
+       case E_OR:
+               e1 = expr_alloc_symbol(&symbol_no);
+               e2 = expr_alloc_symbol(&symbol_no);
+               break;
+       case E_AND:
+               e1 = expr_alloc_symbol(&symbol_yes);
+               e2 = expr_alloc_symbol(&symbol_yes);
+               break;
+       default:
+               ;
+       }
+}
+
+void expr_eliminate_eq(struct expr **ep1, struct expr **ep2)
+{
+       if (!e1 || !e2)
+               return;
+       switch (e1->type) {
+       case E_OR:
+       case E_AND:
+               __expr_eliminate_eq(e1->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);
+}
+
+#undef e1
+#undef e2
+
+int expr_eq(struct expr *e1, struct expr *e2)
+{
+       int res, old_count;
+
+       if (e1->type != e2->type)
+               return 0;
+       switch (e1->type) {
+       case E_EQUAL:
+       case E_UNEQUAL:
+               return e1->left.sym == e2->left.sym && e1->right.sym == e2->right.sym;
+       case E_SYMBOL:
+               return e1->left.sym == e2->left.sym;
+       case E_NOT:
+               return expr_eq(e1->left.expr, e2->left.expr);
+       case E_AND:
+       case E_OR:
+               e1 = expr_copy(e1);
+               e2 = expr_copy(e2);
+               old_count = trans_count;
+               expr_eliminate_eq(&e1, &e2);
+               res = (e1->type == E_SYMBOL && e2->type == E_SYMBOL &&
+                      e1->left.sym == e2->left.sym);
+               expr_free(e1);
+               expr_free(e2);
+               trans_count = old_count;
+               return res;
+       case E_LIST:
+       case E_RANGE:
+       case E_NONE:
+               /* panic */;
+       }
+
+       if (DEBUG_EXPR) {
+               expr_fprint(e1, stdout);
+               printf(" = ");
+               expr_fprint(e2, stdout);
+               printf(" ?\n");
+       }
+
+       return 0;
+}
+
+struct expr *expr_eliminate_yn(struct expr *e)
+{
+       struct expr *tmp;
+
+       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);
+               if (e->left.expr->type == E_SYMBOL) {
+                       if (e->left.expr->left.sym == &symbol_no) {
+                               expr_free(e->left.expr);
+                               expr_free(e->right.expr);
+                               e->type = E_SYMBOL;
+                               e->left.sym = &symbol_no;
+                               e->right.expr = NULL;
+                               return e;
+                       } else if (e->left.expr->left.sym == &symbol_yes) {
+                               free(e->left.expr);
+                               tmp = e->right.expr;
+                               *e = *(e->right.expr);
+                               free(tmp);
+                               return e;
+                       }
+               }
+               if (e->right.expr->type == E_SYMBOL) {
+                       if (e->right.expr->left.sym == &symbol_no) {
+                               expr_free(e->left.expr);
+                               expr_free(e->right.expr);
+                               e->type = E_SYMBOL;
+                               e->left.sym = &symbol_no;
+                               e->right.expr = NULL;
+                               return e;
+                       } else if (e->right.expr->left.sym == &symbol_yes) {
+                               free(e->right.expr);
+                               tmp = e->left.expr;
+                               *e = *(e->left.expr);
+                               free(tmp);
+                               return e;
+                       }
+               }
+               break;
+       case E_OR:
+               e->left.expr = expr_eliminate_yn(e->left.expr);
+               e->right.expr = expr_eliminate_yn(e->right.expr);
+               if (e->left.expr->type == E_SYMBOL) {
+                       if (e->left.expr->left.sym == &symbol_no) {
+                               free(e->left.expr);
+                               tmp = e->right.expr;
+                               *e = *(e->right.expr);
+                               free(tmp);
+                               return e;
+                       } else if (e->left.expr->left.sym == &symbol_yes) {
+                               expr_free(e->left.expr);
+                               expr_free(e->right.expr);
+                               e->type = E_SYMBOL;
+                               e->left.sym = &symbol_yes;
+                               e->right.expr = NULL;
+                               return e;
+                       }
+               }
+               if (e->right.expr->type == E_SYMBOL) {
+                       if (e->right.expr->left.sym == &symbol_no) {
+                               free(e->right.expr);
+                               tmp = e->left.expr;
+                               *e = *(e->left.expr);
+                               free(tmp);
+                               return e;
+                       } else if (e->right.expr->left.sym == &symbol_yes) {
+                               expr_free(e->left.expr);
+                               expr_free(e->right.expr);
+                               e->type = E_SYMBOL;
+                               e->left.sym = &symbol_yes;
+                               e->right.expr = NULL;
+                               return e;
+                       }
+               }
+               break;
+       default:
+               ;
+       }
+       return e;
+}
+
+/*
+ * bool FOO!=n => FOO
+ */
+struct expr *expr_trans_bool(struct expr *e)
+{
+       if (!e)
+               return NULL;
+       switch (e->type) {
+       case E_AND:
+       case E_OR:
+       case E_NOT:
+               e->left.expr = expr_trans_bool(e->left.expr);
+               e->right.expr = expr_trans_bool(e->right.expr);
+               break;
+       case E_UNEQUAL:
+               // FOO!=n -> FOO
+               if (e->left.sym->type == S_TRISTATE) {
+                       if (e->right.sym == &symbol_no) {
+                               e->type = E_SYMBOL;
+                               e->right.sym = NULL;
+                       }
+               }
+               break;
+       default:
+               ;
+       }
+       return e;
+}
+
+/*
+ * e1 || e2 -> ?
+ */
+static struct expr *expr_join_or(struct expr *e1, struct expr *e2)
+{
+       struct expr *tmp;
+       struct symbol *sym1, *sym2;
+
+       if (expr_eq(e1, e2))
+               return expr_copy(e1);
+       if (e1->type != E_EQUAL && e1->type != E_UNEQUAL && e1->type != E_SYMBOL && e1->type != E_NOT)
+               return NULL;
+       if (e2->type != E_EQUAL && e2->type != E_UNEQUAL && e2->type != E_SYMBOL && e2->type != E_NOT)
+               return NULL;
+       if (e1->type == E_NOT) {
+               tmp = e1->left.expr;
+               if (tmp->type != E_EQUAL && tmp->type != E_UNEQUAL && tmp->type != E_SYMBOL)
+                       return NULL;
+               sym1 = tmp->left.sym;
+       } else
+               sym1 = e1->left.sym;
+       if (e2->type == E_NOT) {
+               if (e2->left.expr->type != E_SYMBOL)
+                       return NULL;
+               sym2 = e2->left.expr->left.sym;
+       } else
+               sym2 = e2->left.sym;
+       if (sym1 != sym2)
+               return NULL;
+       if (sym1->type != S_BOOLEAN && sym1->type != S_TRISTATE)
+               return NULL;
+       if (sym1->type == S_TRISTATE) {
+               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')
+                       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')
+                       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')
+                       return expr_alloc_comp(E_UNEQUAL, sym1, &symbol_yes);
+               }
+       }
+       if (sym1->type == S_BOOLEAN && sym1 == sym2) {
+               if ((e1->type == E_NOT && e1->left.expr->type == E_SYMBOL && e2->type == E_SYMBOL) ||
+                   (e2->type == E_NOT && e2->left.expr->type == E_SYMBOL && e1->type == E_SYMBOL))
+                       return expr_alloc_symbol(&symbol_yes);
+       }
+
+       if (DEBUG_EXPR) {
+               printf("optimize (");
+               expr_fprint(e1, stdout);
+               printf(") || (");
+               expr_fprint(e2, stdout);
+               printf(")?\n");
+       }
+       return NULL;
+}
+
+static struct expr *expr_join_and(struct expr *e1, struct expr *e2)
+{
+       struct expr *tmp;
+       struct symbol *sym1, *sym2;
+
+       if (expr_eq(e1, e2))
+               return expr_copy(e1);
+       if (e1->type != E_EQUAL && e1->type != E_UNEQUAL && e1->type != E_SYMBOL && e1->type != E_NOT)
+               return NULL;
+       if (e2->type != E_EQUAL && e2->type != E_UNEQUAL && e2->type != E_SYMBOL && e2->type != E_NOT)
+               return NULL;
+       if (e1->type == E_NOT) {
+               tmp = e1->left.expr;
+               if (tmp->type != E_EQUAL && tmp->type != E_UNEQUAL && tmp->type != E_SYMBOL)
+                       return NULL;
+               sym1 = tmp->left.sym;
+       } else
+               sym1 = e1->left.sym;
+       if (e2->type == E_NOT) {
+               if (e2->left.expr->type != E_SYMBOL)
+                       return NULL;
+               sym2 = e2->left.expr->left.sym;
+       } else
+               sym2 = e2->left.sym;
+       if (sym1 != sym2)
+               return NULL;
+       if (sym1->type != S_BOOLEAN && sym1->type != S_TRISTATE)
+               return NULL;
+
+       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')
+               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)
+               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')
+               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'
+                       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'
+                       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)
+                                                            : expr_alloc_symbol(&symbol_no);
+               }
+               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')
+                       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')
+                       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')
+                       return expr_alloc_comp(E_EQUAL, sym1, &symbol_yes);
+
+               if ((e1->type == E_SYMBOL && e2->type == E_EQUAL && e2->right.sym == &symbol_mod) ||
+                   (e2->type == E_SYMBOL && e1->type == E_EQUAL && e1->right.sym == &symbol_mod) ||
+                   (e1->type == E_SYMBOL && e2->type == E_UNEQUAL && e2->right.sym == &symbol_yes) ||
+                   (e2->type == E_SYMBOL && e1->type == E_UNEQUAL && e1->right.sym == &symbol_yes))
+                       return NULL;
+       }
+
+       if (DEBUG_EXPR) {
+               printf("optimize (");
+               expr_fprint(e1, stdout);
+               printf(") && (");
+               expr_fprint(e2, stdout);
+               printf(")?\n");
+       }
+       return NULL;
+}
+
+static void expr_eliminate_dups1(enum expr_type type, struct expr **ep1, struct expr **ep2)
+{
+#define e1 (*ep1)
+#define e2 (*ep2)
+       struct expr *tmp;
+
+       if (e1->type == type) {
+               expr_eliminate_dups1(type, &e1->left.expr, &e2);
+               expr_eliminate_dups1(type, &e1->right.expr, &e2);
+               return;
+       }
+       if (e2->type == type) {
+               expr_eliminate_dups1(type, &e1, &e2->left.expr);
+               expr_eliminate_dups1(type, &e1, &e2->right.expr);
+               return;
+       }
+       if (e1 == e2)
+               return;
+
+       switch (e1->type) {
+       case E_OR: case E_AND:
+               expr_eliminate_dups1(e1->type, &e1, &e1);
+       default:
+               ;
+       }
+
+       switch (type) {
+       case E_OR:
+               tmp = expr_join_or(e1, e2);
+               if (tmp) {
+                       expr_free(e1); expr_free(e2);
+                       e1 = expr_alloc_symbol(&symbol_no);
+                       e2 = tmp;
+                       trans_count++;
+               }
+               break;
+       case E_AND:
+               tmp = expr_join_and(e1, e2);
+               if (tmp) {
+                       expr_free(e1); expr_free(e2);
+                       e1 = expr_alloc_symbol(&symbol_yes);
+                       e2 = tmp;
+                       trans_count++;
+               }
+               break;
+       default:
+               ;
+       }
+#undef e1
+#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
+}
+
+struct expr *expr_eliminate_dups(struct expr *e)
+{
+       int oldcount;
+       if (!e)
+               return e;
+
+       oldcount = trans_count;
+       while (1) {
+               trans_count = 0;
+               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)
+                       break;
+               e = expr_eliminate_yn(e);
+       }
+       trans_count = oldcount;
+       return e;
+}
+
+struct expr *expr_transform(struct expr *e)
+{
+       struct expr *tmp;
+
+       if (!e)
+               return NULL;
+       switch (e->type) {
+       case E_EQUAL:
+       case E_UNEQUAL:
+       case E_SYMBOL:
+       case E_LIST:
+               break;
+       default:
+               e->left.expr = expr_transform(e->left.expr);
+               e->right.expr = expr_transform(e->right.expr);
+       }
+
+       switch (e->type) {
+       case E_EQUAL:
+               if (e->left.sym->type != S_BOOLEAN)
+                       break;
+               if (e->right.sym == &symbol_no) {
+                       e->type = E_NOT;
+                       e->left.expr = expr_alloc_symbol(e->left.sym);
+                       e->right.sym = NULL;
+                       break;
+               }
+               if (e->right.sym == &symbol_mod) {
+                       printf("boolean symbol %s tested for 'm'? test forced to 'n'\n", e->left.sym->name);
+                       e->type = E_SYMBOL;
+                       e->left.sym = &symbol_no;
+                       e->right.sym = NULL;
+                       break;
+               }
+               if (e->right.sym == &symbol_yes) {
+                       e->type = E_SYMBOL;
+                       e->right.sym = NULL;
+                       break;
+               }
+               break;
+       case E_UNEQUAL:
+               if (e->left.sym->type != S_BOOLEAN)
+                       break;
+               if (e->right.sym == &symbol_no) {
+                       e->type = E_SYMBOL;
+                       e->right.sym = NULL;
+                       break;
+               }
+               if (e->right.sym == &symbol_mod) {
+                       printf("boolean symbol %s tested for 'm'? test forced to 'y'\n", e->left.sym->name);
+                       e->type = E_SYMBOL;
+                       e->left.sym = &symbol_yes;
+                       e->right.sym = NULL;
+                       break;
+               }
+               if (e->right.sym == &symbol_yes) {
+                       e->type = E_NOT;
+                       e->left.expr = expr_alloc_symbol(e->left.sym);
+                       e->right.sym = NULL;
+                       break;
+               }
+               break;
+       case E_NOT:
+               switch (e->left.expr->type) {
+               case E_NOT:
+                       // !!a -> a
+                       tmp = e->left.expr->left.expr;
+                       free(e->left.expr);
+                       free(e);
+                       e = tmp;
+                       e = expr_transform(e);
+                       break;
+               case E_EQUAL:
+               case E_UNEQUAL:
+                       // !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_OR:
+                       // !(a || b) -> !a && !b
+                       tmp = e->left.expr;
+                       e->type = E_AND;
+                       e->right.expr = expr_alloc_one(E_NOT, tmp->right.expr);
+                       tmp->type = E_NOT;
+                       tmp->right.expr = NULL;
+                       e = expr_transform(e);
+                       break;
+               case E_AND:
+                       // !(a && b) -> !a || !b
+                       tmp = e->left.expr;
+                       e->type = E_OR;
+                       e->right.expr = expr_alloc_one(E_NOT, tmp->right.expr);
+                       tmp->type = E_NOT;
+                       tmp->right.expr = NULL;
+                       e = expr_transform(e);
+                       break;
+               case E_SYMBOL:
+                       if (e->left.expr->left.sym == &symbol_yes) {
+                               // !'y' -> 'n'
+                               tmp = e->left.expr;
+                               free(e);
+                               e = tmp;
+                               e->type = E_SYMBOL;
+                               e->left.sym = &symbol_no;
+                               break;
+                       }
+                       if (e->left.expr->left.sym == &symbol_mod) {
+                               // !'m' -> 'm'
+                               tmp = e->left.expr;
+                               free(e);
+                               e = tmp;
+                               e->type = E_SYMBOL;
+                               e->left.sym = &symbol_mod;
+                               break;
+                       }
+                       if (e->left.expr->left.sym == &symbol_no) {
+                               // !'n' -> 'y'
+                               tmp = e->left.expr;
+                               free(e);
+                               e = tmp;
+                               e->type = E_SYMBOL;
+                               e->left.sym = &symbol_yes;
+                               break;
+                       }
+                       break;
+               default:
+                       ;
+               }
+               break;
+       default:
+               ;
+       }
+       return e;
+}
+
+int expr_contains_symbol(struct expr *dep, struct symbol *sym)
+{
+       if (!dep)
+               return 0;
+
+       switch (dep->type) {
+       case E_AND:
+       case E_OR:
+               return expr_contains_symbol(dep->left.expr, sym) ||
+                      expr_contains_symbol(dep->right.expr, sym);
+       case E_SYMBOL:
+               return dep->left.sym == sym;
+       case E_EQUAL:
+       case E_UNEQUAL:
+               return dep->left.sym == sym ||
+                      dep->right.sym == sym;
+       case E_NOT:
+               return expr_contains_symbol(dep->left.expr, sym);
+       default:
+               ;
+       }
+       return 0;
+}
+
+bool expr_depends_symbol(struct expr *dep, struct symbol *sym)
+{
+       if (!dep)
+               return false;
+
+       switch (dep->type) {
+       case E_AND:
+               return expr_depends_symbol(dep->left.expr, sym) ||
+                      expr_depends_symbol(dep->right.expr, sym);
+       case E_SYMBOL:
+               return dep->left.sym == sym;
+       case E_EQUAL:
+               if (dep->left.sym == sym) {
+                       if (dep->right.sym == &symbol_yes || dep->right.sym == &symbol_mod)
+                               return true;
+               }
+               break;
+       case E_UNEQUAL:
+               if (dep->left.sym == sym) {
+                       if (dep->right.sym == &symbol_no)
+                               return true;
+               }
+               break;
+       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
+}
+
+struct expr *expr_trans_compare(struct expr *e, enum expr_type type, struct symbol *sym)
+{
+       struct expr *e1, *e2;
+
+       if (!e) {
+               e = expr_alloc_symbol(sym);
+               if (type == E_UNEQUAL)
+                       e = expr_alloc_one(E_NOT, e);
+               return e;
+       }
+       switch (e->type) {
+       case E_AND:
+               e1 = expr_trans_compare(e->left.expr, E_EQUAL, sym);
+               e2 = expr_trans_compare(e->right.expr, E_EQUAL, sym);
+               if (sym == &symbol_yes)
+                       e = expr_alloc_two(E_AND, e1, e2);
+               if (sym == &symbol_no)
+                       e = expr_alloc_two(E_OR, e1, e2);
+               if (type == E_UNEQUAL)
+                       e = expr_alloc_one(E_NOT, e);
+               return e;
+       case E_OR:
+               e1 = expr_trans_compare(e->left.expr, E_EQUAL, sym);
+               e2 = expr_trans_compare(e->right.expr, E_EQUAL, sym);
+               if (sym == &symbol_yes)
+                       e = expr_alloc_two(E_OR, e1, e2);
+               if (sym == &symbol_no)
+                       e = expr_alloc_two(E_AND, e1, e2);
+               if (type == E_UNEQUAL)
+                       e = expr_alloc_one(E_NOT, e);
+               return e;
+       case E_NOT:
+               return expr_trans_compare(e->left.expr, type == E_EQUAL ? E_UNEQUAL : E_EQUAL, sym);
+       case E_UNEQUAL:
+       case E_EQUAL:
+               if (type == E_EQUAL) {
+                       if (sym == &symbol_yes)
+                               return expr_copy(e);
+                       if (sym == &symbol_mod)
+                               return expr_alloc_symbol(&symbol_no);
+                       if (sym == &symbol_no)
+                               return expr_alloc_one(E_NOT, expr_copy(e));
+               } else {
+                       if (sym == &symbol_yes)
+                               return expr_alloc_one(E_NOT, expr_copy(e));
+                       if (sym == &symbol_mod)
+                               return expr_alloc_symbol(&symbol_yes);
+                       if (sym == &symbol_no)
+                               return expr_copy(e);
+               }
+               break;
+       case E_SYMBOL:
+               return expr_alloc_comp(type, e->left.sym, sym);
+       case E_LIST:
+       case E_RANGE:
+       case E_NONE:
+               /* panic */;
+       }
+       return NULL;
+}
+
+tristate expr_calc_value(struct expr *e)
+{
+       tristate val1, val2;
+       const char *str1, *str2;
+
+       if (!e)
+               return yes;
+
+       switch (e->type) {
+       case E_SYMBOL:
+               sym_calc_value(e->left.sym);
+               return e->left.sym->curr.tri;
+       case E_AND:
+               val1 = expr_calc_value(e->left.expr);
+               val2 = expr_calc_value(e->right.expr);
+               return EXPR_AND(val1, val2);
+       case E_OR:
+               val1 = expr_calc_value(e->left.expr);
+               val2 = expr_calc_value(e->right.expr);
+               return EXPR_OR(val1, val2);
+       case E_NOT:
+               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_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;
+       default:
+               printf("expr_calc_value: %d?\n", e->type);
+               return no;
+       }
+}
+
+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_EQUAL:
+       case E_UNEQUAL:
+               if (t2 == E_NOT)
+                       return 1;
+       case E_NOT:
+               if (t2 == E_AND)
+                       return 1;
+       case E_AND:
+               if (t2 == E_OR)
+                       return 1;
+       case E_OR:
+               if (t2 == E_LIST)
+                       return 1;
+       case E_LIST:
+               if (t2 == 0)
+                       return 1;
+       default:
+               return -1;
+       }
+       printf("[%dgt%d?]", t1, t2);
+       return 0;
+#endif
+}
+
+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);
+}
+
+void expr_print(struct expr *e, void (*fn)(void *, struct symbol *, const char *), void *data, int prevtoken)
+{
+       if (!e) {
+               fn(data, NULL, "y");
+               return;
+       }
+
+       if (expr_compare_type(prevtoken, e->type) > 0)
+               fn(data, NULL, "(");
+       switch (e->type) {
+       case E_SYMBOL:
+               if (e->left.sym->name)
+                       fn(data, e->left.sym, e->left.sym->name);
+               else
+                       fn(data, NULL, "<choice>");
+               break;
+       case E_NOT:
+               fn(data, NULL, "!");
+               expr_print(e->left.expr, fn, data, E_NOT);
+               break;
+       case E_EQUAL:
+               if (e->left.sym->name)
+                       fn(data, e->left.sym, e->left.sym->name);
+               else
+                       fn(data, NULL, "<choice>");
+               fn(data, NULL, "=");
+               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);
+               else
+                       fn(data, NULL, "<choice>");
+               fn(data, NULL, "!=");
+               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);
+               break;
+       case E_AND:
+               expr_print(e->left.expr, fn, data, E_AND);
+               fn(data, NULL, " && ");
+               expr_print(e->right.expr, fn, data, E_AND);
+               break;
+       case E_LIST:
+               fn(data, e->right.sym, e->right.sym->name);
+               if (e->left.expr) {
+                       fn(data, NULL, " ^ ");
+                       expr_print(e->left.expr, fn, data, E_LIST);
+               }
+               break;
+       case E_RANGE:
+               fn(data, NULL, "[");
+               fn(data, e->left.sym, e->left.sym->name);
+               fn(data, NULL, " ");
+               fn(data, e->right.sym, e->right.sym->name);
+               fn(data, NULL, "]");
+               break;
+       default:
+         {
+               char buf[32];
+               sprintf(buf, "<unknown type %d>", e->type);
+               fn(data, NULL, buf);
+               break;
+         }
+       }
+       if (expr_compare_type(prevtoken, e->type) > 0)
+               fn(data, NULL, ")");
+}
+
+static void expr_print_file_helper(void *data, struct symbol *sym, const char *str)
+{
+       xfwrite(str, strlen(str), 1, data);
+}
+
+void expr_fprint(struct expr *e, FILE *out)
+{
+       expr_print(e, expr_print_file_helper, out, E_NONE);
+}
+
+static void expr_print_gstr_helper(void *data, struct symbol *sym, const char *str)
+{
+       struct gstr *gs = (struct gstr*)data;
+       const char *sym_str = NULL;
+
+       if (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);
+}