Remove unused temporaries from taken map

If the result has no uses we need to allocate it when visiting the
defining instruction. However, we should still go through the
logic to remove the temporary from the taken map afterwards,
as the temporary can still be reused prior to the defining
instruction.

Author: nikic

Zend/Optimizer/optimize_temp_vars_5.c

@@ -150,31 +150,27 @@ void zend_optimize_temporary_variables(zend_op_array *op_array, zend_optimizer_c
 
 		if (opline->result_type & (IS_VAR | IS_TMP_VAR)) {
 			currT = VAR_NUM(opline->result.var) - offset;
-			if (zend_bitset_in(valid_T, currT)) {
-				if (start_of_T[currT] == opline) {
-					/* ZEND_FAST_CALL can not share temporary var with others
-					 * since the fast_var could also be set by ZEND_HANDLE_EXCEPTION
-					 * which could be ahead of it */
-					if (opline->opcode != ZEND_FAST_CALL) {
-						zend_bitset_excl(taken_T, map_T[currT]);
-					}
+			if (!zend_bitset_in(valid_T, currT)) {
+				/* As a result of DCE, an opcode may have an unused result. */
+				GET_AVAILABLE_T();
+				map_T[currT] = i;
+				zend_bitset_incl(valid_T, currT);
+			}
+			opline->result.var = NUM_VAR(map_T[currT] + offset);
+			if (start_of_T[currT] == opline) {
+				/* ZEND_FAST_CALL can not share temporary var with others
+				 * since the fast_var could also be set by ZEND_HANDLE_EXCEPTION
+				 * which could be ahead of it */
+				if (opline->opcode != ZEND_FAST_CALL) {
+					zend_bitset_excl(taken_T, map_T[currT]);
 				}
-				opline->result.var = NUM_VAR(map_T[currT] + offset);
 				if (opline->opcode == ZEND_ROPE_INIT) {
-					if (start_of_T[currT] == opline) {
-						uint32_t num = ((opline->extended_value * sizeof(zend_string*)) + (sizeof(zval) - 1)) / sizeof(zval);
-						while (num > 1) {
-							num--;
-							zend_bitset_excl(taken_T, map_T[currT]+num);
-						}
+					uint32_t num = ((opline->extended_value * sizeof(zend_string*)) + (sizeof(zval) - 1)) / sizeof(zval);
+					while (num > 1) {
+						num--;
+						zend_bitset_excl(taken_T, map_T[currT]+num);
 					}
 				}
-			} else {
-				/* Code which gets here is using a wrongly built opcode such as RECV() */
-				GET_AVAILABLE_T();
-				map_T[currT] = i;
-				zend_bitset_incl(valid_T, currT);
-				opline->result.var = NUM_VAR(i + offset);
 			}
 		}