break;
case E_NOT:
expr_free(e->left.expr);
- return;
+ break;
case E_EQUAL:
case E_GEQ:
case E_GTH:
#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);
__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) {
}
}
+/*
+ * 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)
#undef e1
#undef 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;
return 0;
}
+/*
+ * 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;
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);
expr_eliminate_dups1(type, &e1, &e2->right.expr);
return;
}
+
+ /* e1 and e2 are leaves. Compare and process them. */
+
if (e1 == e2)
return;
#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;
;
}
if (!trans_count)
+ /* No simplifications done in this pass. We're done */
break;
e = expr_eliminate_yn(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;
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;
return expr_get_leftmost_symbol(ret);
}
-void expr_print(struct expr *e, void (*fn)(void *, struct symbol *, const char *), void *data, int prevtoken)
+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");
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);
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)
{
xfwrite(str, strlen(str), 1, data);
{
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);
+}
git.samba.org / sfrench / cifs-2.6.git / blobdiff