+/* Predicate handling.
+
+ We construct from the machine description a table mapping each
+ predicate to a list of the rtl codes it can possibly match. The
+ function 'maybe_both_true' uses it to deduce that there are no
+ expressions that can be matches by certain pairs of tree nodes.
+ Also, if a predicate can match only one code, we can hardwire that
+ code into the node testing the predicate.
+
+ Some predicates are flagged as special. validate_pattern will not
+ warn about modeless match_operand expressions if they have a
+ special predicate. Predicates that allow only constants are also
+ treated as special, for this purpose.
+
+ validate_pattern will warn about predicates that allow non-lvalues
+ when they appear in destination operands.
+
+ Calculating the set of rtx codes that can possibly be accepted by a
+ predicate expression EXP requires a three-state logic: any given
+ subexpression may definitively accept a code C (Y), definitively
+ reject a code C (N), or may have an indeterminate effect (I). N
+ and I is N; Y or I is Y; Y and I, N or I are both I. Here are full
+ truth tables.
+
+ a b a&b a|b
+ Y Y Y Y
+ N Y N Y
+ N N N N
+ I Y I Y
+ I N N I
+ I I I I
+
+ We represent Y with 1, N with 0, I with 2. If any code is left in
+ an I state by the complete expression, we must assume that that
+ code can be accepted. */
+
+#define N 0
+#define Y 1
+#define I 2
+
+#define TRISTATE_AND(a,b) \
+ ((a) == I ? ((b) == N ? N : I) : \
+ (b) == I ? ((a) == N ? N : I) : \
+ (a) && (b))
+
+#define TRISTATE_OR(a,b) \
+ ((a) == I ? ((b) == Y ? Y : I) : \
+ (b) == I ? ((a) == Y ? Y : I) : \
+ (a) || (b))
+
+#define TRISTATE_NOT(a) \
+ ((a) == I ? I : !(a))
+
+/* 0 means no warning about that code yet, 1 means warned. */
+static char did_you_mean_codes[NUM_RTX_CODE];
+
+/* Recursively calculate the set of rtx codes accepted by the
+ predicate expression EXP, writing the result to CODES. */
+static void
+compute_predicate_codes (rtx exp, char codes[NUM_RTX_CODE])
+{
+ char op0_codes[NUM_RTX_CODE];
+ char op1_codes[NUM_RTX_CODE];
+ char op2_codes[NUM_RTX_CODE];
+ int i;
+
+ switch (GET_CODE (exp))
+ {
+ case AND:
+ compute_predicate_codes (XEXP (exp, 0), op0_codes);
+ compute_predicate_codes (XEXP (exp, 1), op1_codes);
+ for (i = 0; i < NUM_RTX_CODE; i++)
+ codes[i] = TRISTATE_AND (op0_codes[i], op1_codes[i]);
+ break;
+
+ case IOR:
+ compute_predicate_codes (XEXP (exp, 0), op0_codes);
+ compute_predicate_codes (XEXP (exp, 1), op1_codes);
+ for (i = 0; i < NUM_RTX_CODE; i++)
+ codes[i] = TRISTATE_OR (op0_codes[i], op1_codes[i]);
+ break;
+ case NOT:
+ compute_predicate_codes (XEXP (exp, 0), op0_codes);
+ for (i = 0; i < NUM_RTX_CODE; i++)
+ codes[i] = TRISTATE_NOT (op0_codes[i]);
+ break;
+
+ case IF_THEN_ELSE:
+ /* a ? b : c accepts the same codes as (a & b) | (!a & c). */
+ compute_predicate_codes (XEXP (exp, 0), op0_codes);
+ compute_predicate_codes (XEXP (exp, 1), op1_codes);
+ compute_predicate_codes (XEXP (exp, 2), op2_codes);
+ for (i = 0; i < NUM_RTX_CODE; i++)
+ codes[i] = TRISTATE_OR (TRISTATE_AND (op0_codes[i], op1_codes[i]),
+ TRISTATE_AND (TRISTATE_NOT (op0_codes[i]),
+ op2_codes[i]));
+ break;
+
+ case MATCH_CODE:
+ /* MATCH_CODE allows a specified list of codes. However, if it
+ does not apply to the top level of the expression, it does not
+ constrain the set of codes for the top level. */
+ if (XSTR (exp, 1)[0] != '\0')
+ {
+ memset (codes, Y, NUM_RTX_CODE);
+ break;
+ }
+
+ memset (codes, N, NUM_RTX_CODE);
+ {
+ const char *next_code = XSTR (exp, 0);
+ const char *code;
+
+ if (*next_code == '\0')
+ {
+ message_with_line (pattern_lineno, "empty match_code expression");
+ error_count++;
+ break;
+ }
+
+ while ((code = scan_comma_elt (&next_code)) != 0)
+ {
+ size_t n = next_code - code;
+ int found_it = 0;
+
+ for (i = 0; i < NUM_RTX_CODE; i++)
+ if (!strncmp (code, GET_RTX_NAME (i), n)
+ && GET_RTX_NAME (i)[n] == '\0')
+ {
+ codes[i] = Y;
+ found_it = 1;
+ break;
+ }
+ if (!found_it)
+ {
+ message_with_line (pattern_lineno, "match_code \"%.*s\" matches nothing",
+ (int) n, code);
+ error_count ++;
+ for (i = 0; i < NUM_RTX_CODE; i++)
+ if (!strncasecmp (code, GET_RTX_NAME (i), n)
+ && GET_RTX_NAME (i)[n] == '\0'
+ && !did_you_mean_codes[i])
+ {
+ did_you_mean_codes[i] = 1;
+ message_with_line (pattern_lineno, "(did you mean \"%s\"?)", GET_RTX_NAME (i));
+ }
+ }
+
+ }
+ }
+ break;
+
+ case MATCH_OPERAND:
+ /* MATCH_OPERAND disallows the set of codes that the named predicate
+ disallows, and is indeterminate for the codes that it does allow. */
+ {
+ struct pred_data *p = lookup_predicate (XSTR (exp, 1));
+ if (!p)
+ {
+ message_with_line (pattern_lineno,
+ "reference to unknown predicate '%s'",
+ XSTR (exp, 1));
+ error_count++;
+ break;
+ }
+ for (i = 0; i < NUM_RTX_CODE; i++)
+ codes[i] = p->codes[i] ? I : N;
+ }
+ break;
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