/*
* matiec - a compiler for the programming languages defined in IEC 61131-3
*
* Copyright (C) 2003-2011 Mario de Sousa (msousa@fe.up.pt)
* Copyright (C) 2012 Manuele Conti (conti.ma@alice.it)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*
* This code is made available on the understanding that it will not be
* used in safety-critical situations without a full and competent review.
*/
/*
* An IEC 61131-3 compiler.
*
* Based on the
* FINAL DRAFT - IEC 61131-3, 2nd Ed. (2001-12-10)
*
*/
/* TODO:
* - Add support for comparison (= and !=) of enumeration literals!
* We will need to add another const_value entry to the symbol_c, containing the
* possible enumeration value of the enum constant!
* Doing this will allow us to more easily implement a constant_propagation_c later on!
*
* - Add support for comparison (= and !=) of the exact same variable
* (e.g. if (int_v = int_v) then ...)
*/
/* Do constant folding...
*
* I.e., Determine the value of all expressions in which only constant values (i.e. literals) are used.
* The (constant) result of each operation is stored (annotated) in the respective operation symbol
* (e.g.: add_expression_c) in the abstract syntax tree,
*
* For example:
* 2 + 3 -> the constant value '5' is stored in the add_expression_c symbol.
* 22.2 - 5.0 -> the constant value '17.2' is stored in the add_expression_c symbol.
* etc...
*
*
* NOTE 1
* Some operations and constants can have multiple data types. For example,
* 1 AND 0
* may be either a BOOL, BYTE, WORD or LWORD.
*
* The same happens with
* 1 + 2
* which may be signed (e.g. INT) or unsigned (UINT)
*
* For the above reason, instead of storing a single constant value, we actually store 4:
* - bool
* - uint64
* - int64
* - real64
*
* Additionally, since the result of an operation may result in an overflow, we actually
* store the result inside a struct (defined in absyntax.hh)
*
* ** During stage 3 (semantic analysis/checking) we will be doing constant folding.
* * That algorithm will anotate the abstract syntax tree with the result of operations
* * on literals (i.e. 44 + 55 will store the result 99).
* * Since the same source code (e.g. 1 + 0) may actually be a BOOL or an ANY_INT,
* * or an ANY_BIT, we need to handle all possibilities, and determine the result of the
* * operation assuming each type.
* * For this reason, we have one entry for each possible type, with some expressions
* * having more than one entry filled in!
* **
* typedef enum { cs_undefined, // not defined --> const_value is not valid!
* cs_const_value, // const value is valid
* cs_overflow // result produced overflow or underflow --> const_value is not valid!
* } const_status_t;
*
* typedef struct {
* const_status_t status;
* real64_t value;
* } const_value_real64_t;
* const_value_real64_t *const_value_real64; // when NULL --> UNDEFINED
*
* typedef struct {
* const_status_t status;
* int64_t value;
* } const_value_int64_t;
* const_value_int64_t *const_value_int64; // when NULL --> UNDEFINED
*
* typedef struct {
* const_status_t status;
* uint64_t value;
* } const_value_uint64_t;
* const_value_uint64_t *const_value_uint64; // when NULL --> UNDEFINED
*
* typedef struct {
* const_status_t status;
* bool value;
* } const_value_bool_t;
* const_value_bool_t *const_value_bool; // when NULL --> UNDEFINED
*
*
*
* NOTE 2
* This file does not print out any error messages!
* We cannot really print out error messages when we find an overflow. Since each operation
* (symbol in the absract syntax tree for that operation) will have up to 4 constant results,
* it may happen that some of them overflow, while other do not.
* We must wait for data type checking to determine the exact data type of each expression
* before we can decide whether or not we should print out an overflow error message.
*
* For this reason, this visitor merely annotates the abstract syntax tree, and leaves the
* actuall printing of errors for the print_datatype_errors_c class!
*/
#include "constant_folding.hh"
#include <stdlib.h> /* required for malloc() */
#include <string.h> /* required for strlen() */
// #include <stdlib.h> /* required for atoi() */
#include <errno.h> /* required for errno */
#include "../main.hh" // required for uint8_t, real_64_t, ..., and the macros NAN, INFINITY, INT8_MAX, REAL32_MAX, ... */
#define FIRST_(symbol1, symbol2) (((symbol1)->first_order < (symbol2)->first_order) ? (symbol1) : (symbol2))
#define LAST_(symbol1, symbol2) (((symbol1)->last_order > (symbol2)->last_order) ? (symbol1) : (symbol2))
#define STAGE3_ERROR(error_level, symbol1, symbol2, ...) { \
if (current_display_error_level >= error_level) { \
fprintf(stderr, "%s:%d-%d..%d-%d: error: ", \
FIRST_(symbol1,symbol2)->first_file, FIRST_(symbol1,symbol2)->first_line, FIRST_(symbol1,symbol2)->first_column,\
LAST_(symbol1,symbol2) ->last_line, LAST_(symbol1,symbol2) ->last_column);\
fprintf(stderr, __VA_ARGS__); \
fprintf(stderr, "\n"); \
error_count++; \
} \
}
#define STAGE3_WARNING(symbol1, symbol2, ...) { \
fprintf(stderr, "%s:%d-%d..%d-%d: warning: ", \
FIRST_(symbol1,symbol2)->first_file, FIRST_(symbol1,symbol2)->first_line, FIRST_(symbol1,symbol2)->first_column,\
LAST_(symbol1,symbol2) ->last_line, LAST_(symbol1,symbol2) ->last_column);\
fprintf(stderr, __VA_ARGS__); \
fprintf(stderr, "\n"); \
warning_found = true; \
}
#define SET_CVALUE(dtype, symbol, new_value) ((symbol)->const_value._##dtype.value) = new_value; ((symbol)->const_value._##dtype.status) = symbol_c::cs_const_value;
#define GET_CVALUE(dtype, symbol) ((symbol)->const_value._##dtype.value)
#define SET_OVFLOW(dtype, symbol) ((symbol)->const_value._##dtype.status) = symbol_c::cs_overflow
#define SET_NONCONST(dtype, symbol) ((symbol)->const_value._##dtype.status) = symbol_c::cs_non_const
#define VALID_CVALUE(dtype, symbol) (symbol_c::cs_const_value == (symbol)->const_value._##dtype.status)
#define ISZERO_CVALUE(dtype, symbol) ((VALID_CVALUE(dtype, symbol)) && (GET_CVALUE(dtype, symbol) == 0))
#define ISEQUAL_CVALUE(dtype, symbol1, symbol2) \
(VALID_CVALUE(dtype, symbol1) && VALID_CVALUE(dtype, symbol2) && (GET_CVALUE(dtype, symbol1) == GET_CVALUE(dtype, symbol2)))
#define DO_BINARY_OPER(dtype, oper, otype)\
if (VALID_CVALUE(dtype, symbol->r_exp) && VALID_CVALUE(dtype, symbol->l_exp)) { \
SET_CVALUE(otype, symbol, GET_CVALUE(dtype, symbol->l_exp) oper GET_CVALUE(dtype, symbol->r_exp)); \
}
#define DO_BINARY_OPER_(oper_type, operation, res_type, operand1, operand2)\
if (VALID_CVALUE(oper_type, operand1) && VALID_CVALUE(oper_type, operand2)) { \
SET_CVALUE(res_type, symbol, GET_CVALUE(oper_type, operand1) operation GET_CVALUE(oper_type, operand2)); \
}
#define DO_UNARY_OPER(dtype, operation, operand)\
if (VALID_CVALUE(dtype, operand)) { \
SET_CVALUE(dtype, symbol, operation GET_CVALUE(dtype, operand)); \
}
/***********************************************************************/
/***********************************************************************/
/***********************************************************************/
/*** convert string to numerical value ***/
/***********************************************************************/
/***********************************************************************/
/***********************************************************************/
/* To allow the compiler to be portable, we cannot assume that int64_t is mapped onto long long int,
* so we cannot call strtoll() and strtoull() in extract_int64() and extract_uint64().
*
* So, we create our own strtouint64() and strtoint64() functions.
* (We actually call them matiec_strtoint64() so they will not clash with any function
* that may be added to the standard library in the future).
* We actually create several of each, and let the compiler choose which is the correct one,
* by having it resolve the call to the overloaded function. For the C++ compiler to be able
* to resolve this ambiguity, we need to add a dummy parameter to each function!
*
* TODO: support platforms (where the compiler will run) in which int64_t is mapped onto int !!
* Is this really needed?
* Currently, when trying to compile matiec on sych a platform, the C++ compiler will not
* find any apropriate matiec_strtoint64() to call, so matiec will not be able to be compiled.
* If you need this, you are welcome to fix it yourself...
*/
static int64_t matiec_strtoint64 ( long int *dummy, const char *nptr, char **endptr, int base) {return strtol (nptr, endptr, base);}
static int64_t matiec_strtoint64 ( long long int *dummy, const char *nptr, char **endptr, int base) {return strtoll (nptr, endptr, base);}
static uint64_t matiec_strtouint64(unsigned long int *dummy, const char *nptr, char **endptr, int base) {return strtoul (nptr, endptr, base);}
static uint64_t matiec_strtouint64(unsigned long long int *dummy, const char *nptr, char **endptr, int base) {return strtoull(nptr, endptr, base);}
/* extract the value of an integer from an integer_c object !! */
/* NOTE: it must ignore underscores! */
/* NOTE: To follow the basic structure used throughout the compiler's code, we should really be
* writing this as a visitor_c (and do away with the dynamic casts!), but since we only have 3 distinct
* symbol class types to handle, it is probably easier to read if we write it as a standard function...
*/
int64_t extract_int64_value(symbol_c *sym, bool *overflow) {
int64_t ret;
std::string str = "";
char *endptr;
const char *value;
int base;
integer_c *integer;
hex_integer_c *hex_integer;
octal_integer_c *octal_integer;
binary_integer_c *binary_integer;
if ((integer = dynamic_cast<integer_c *>(sym)) != NULL) {value = integer ->value + 0; base = 10;}
else if ((hex_integer = dynamic_cast<hex_integer_c *>(sym)) != NULL) {value = hex_integer ->value + 3; base = 16;}
else if ((octal_integer = dynamic_cast<octal_integer_c *>(sym)) != NULL) {value = octal_integer ->value + 2; base = 8;}
else if ((binary_integer = dynamic_cast<binary_integer_c *>(sym)) != NULL) {value = binary_integer->value + 2; base = 2;}
else ERROR;
for(unsigned int i = 0; i < strlen(value); i++)
if (value[i] != '_') str += value[i];
errno = 0; // since strtoXX() may legally return 0, we must set errno to 0 to detect errors correctly!
ret = matiec_strtoint64((int64_t *)NULL, str.c_str(), &endptr, base);
if (overflow != NULL)
*overflow = (errno == ERANGE);
if (((errno != 0) && (errno != ERANGE)) || (*endptr != '\0'))
ERROR;
return ret;
}
uint64_t extract_uint64_value(symbol_c *sym, bool *overflow) {
uint64_t ret;
std::string str = "";
char *endptr;
const char *value;
int base;
integer_c *integer;
hex_integer_c *hex_integer;
octal_integer_c *octal_integer;
binary_integer_c *binary_integer;
if ((integer = dynamic_cast<integer_c *>(sym)) != NULL) {value = integer ->value + 0; base = 10;}
else if ((hex_integer = dynamic_cast<hex_integer_c *>(sym)) != NULL) {value = hex_integer ->value + 3; base = 16;}
else if ((octal_integer = dynamic_cast<octal_integer_c *>(sym)) != NULL) {value = octal_integer ->value + 2; base = 8;}
else if ((binary_integer = dynamic_cast<binary_integer_c *>(sym)) != NULL) {value = binary_integer->value + 2; base = 2;}
else ERROR;
for(unsigned int i = 0; i < strlen(value); i++)
if (value[i] != '_') str += value[i];
errno = 0; // since strtoXX() may legally return 0, we must set errno to 0 to detect errors correctly!
ret = matiec_strtouint64((uint64_t *)NULL, str.c_str(), &endptr, base);
if (overflow != NULL)
*overflow = (errno == ERANGE);
if (((errno != 0) && (errno != ERANGE)) || (*endptr != '\0'))
ERROR;
return ret;
}
/* extract the value of a real from an real_c object !! */
/* NOTE: it must ignore underscores! */
/* From iec_bison.yy
* real:
* real_token {$$ = new real_c($1, locloc(@$));}
* | fixed_point_token {$$ = new real_c($1, locloc(@$));}
*
* From iec_flex.ll
* {real} {yylval.ID=strdup(yytext); return real_token;}
* {fixed_point} {yylval.ID=strdup(yytext); return fixed_point_token;}
*
* real {integer}\.{integer}{exponent}
* fixed_point {integer}\.{integer}
* exponent [Ee]([+-]?){integer}
* integer {digit}((_?{digit})*)
*/
real64_t extract_real_value(symbol_c *sym, bool *overflow) {
std::string str = "";
real_c *real_sym;
char *endptr;
real64_t ret;
if ((real_sym = dynamic_cast<real_c *>(sym)) == NULL) ERROR;
for(unsigned int i = 0; i < strlen(real_sym->value); i++)
if (real_sym->value[i] != '_') str += real_sym->value[i];
errno = 0; // since strtoXX() may legally return 0, we must set errno to 0 to detect errors correctly!
#if (real64_t == float)
ret = strtof(str.c_str(), &endptr);
#elif (real64_t == double)
ret = strtod(str.c_str(), &endptr);
#elif (real64_t == long_double)
ret = strtold(str.c_str(), &endptr);
#else
#error Could not determine which data type is being used for real64_t (defined in absyntax.hh). Aborting!
#endif
if (overflow != NULL)
*overflow = (errno == ERANGE);
if (((errno != 0) && (errno != ERANGE)) || (*endptr != '\0'))
ERROR;
return ret;
}
/***********************************************************************/
/***********************************************************************/
/***********************************************************************/
/*** Functions to check for overflow situation ***/
/***********************************************************************/
/***********************************************************************/
/***********************************************************************/
/* NOTE:
* Most of the conditions to detect overflows on signed and unsigned integer operations were adapted from
* https://www.securecoding.cert.org/confluence/display/seccode/INT32-C.+Ensure+that+operations+on+signed+integers+do+not+result+in+overflow?showComments=false
* https://www.securecoding.cert.org/confluence/display/seccode/INT30-C.+Ensure+that+unsigned+integer+operations+do+not+wrap
*/
/* NOTE: If at all possible, all overflow tests are done by pre-condition tests, i.e. tests that
* can be run _before_ the operation is executed, and therefore without accessing the result!
*
* The exception is for real/floating point values, that simply test if the result is NaN (not a number).
*/
/* res = a + b */
static void CHECK_OVERFLOW_uint64_SUM(symbol_c *res, symbol_c *a, symbol_c *b) {
if (!VALID_CVALUE(uint64, res))
return;
/* Test by post-condition: If sum is smaller than either operand => overflow! */
// if (GET_CVALUE(uint64, res) < GET_CVALUE(uint64, a))
/* Test by pre-condition: If (UINT64_MAX - a) < b => overflow! */
if ((UINT64_MAX - GET_CVALUE(uint64, a)) < GET_CVALUE(uint64, b))
SET_OVFLOW(uint64, res);
}
/* res = a - b */
static void CHECK_OVERFLOW_uint64_SUB(symbol_c *res, symbol_c *a, symbol_c *b) {
if (!VALID_CVALUE(uint64, res))
return;
/* Test by post-condition: If diference is larger than a => overflow! */
// if (GET_CVALUE(uint64, res) > GET_CVALUE(uint64, a))
/* Test by pre-condition: if b > a => overflow! */
if (GET_CVALUE(uint64, b) > GET_CVALUE(uint64, a))
SET_OVFLOW(uint64, res);
}
/* res = a * b */
static void CHECK_OVERFLOW_uint64_MUL(symbol_c *res, symbol_c *a, symbol_c *b) {
if (!VALID_CVALUE(uint64, res))
return;
/* Test by pre-condition: If (UINT64_MAX / a) < b => overflow! */
if ((UINT64_MAX / GET_CVALUE(uint64, a)) < GET_CVALUE(uint64, b))
SET_OVFLOW(uint64, res);
}
/* res = a / b */
static void CHECK_OVERFLOW_uint64_DIV(symbol_c *res, symbol_c *a, symbol_c *b) {
if (!VALID_CVALUE(uint64, res))
return;
if (GET_CVALUE(uint64, b) == 0) /* division by zero! */
SET_OVFLOW(uint64, res);
}
/* res = a MOD b */
static void CHECK_OVERFLOW_uint64_MOD(symbol_c *res, symbol_c *a, symbol_c *b) {
if (!VALID_CVALUE(uint64, res))
return;
/* no overflow condition exists, including division by zero, which IEC 61131-3 considers legal for MOD operation! */
if (false)
SET_OVFLOW(uint64, res);
}
/* res = a + b */
static void CHECK_OVERFLOW_int64_SUM(symbol_c *res, symbol_c *a_ptr, symbol_c *b_ptr) {
if (!VALID_CVALUE(int64, res))
return;
int64_t a = GET_CVALUE(int64, a_ptr);
int64_t b = GET_CVALUE(int64, b_ptr);
/* The following test is valid no matter what representation is being used (e.g. two's complement, etc...) */
if (((b > 0) && (a > (INT64_MAX - b)))
|| ((b < 0) && (a < (INT64_MIN - b))))
SET_OVFLOW(int64, res);
}
/* res = a - b */
static void CHECK_OVERFLOW_int64_SUB(symbol_c *res, symbol_c *a_ptr, symbol_c *b_ptr) {
if (!VALID_CVALUE(int64, res))
return;
int64_t a = GET_CVALUE(int64, a_ptr);
int64_t b = GET_CVALUE(int64, b_ptr);
/* The following test is valid no matter what representation is being used (e.g. two's complement, etc...) */
if (((b > 0) && (a < (INT64_MIN + b)))
|| ((b < 0) && (a > (INT64_MAX + b))))
SET_OVFLOW(int64, res);
}
/* res = a * b */
static void CHECK_OVERFLOW_int64_MUL(symbol_c *res, symbol_c *a_ptr, symbol_c *b_ptr) {
if (!VALID_CVALUE(int64, res))
return;
int64_t a = GET_CVALUE(int64, a_ptr);
int64_t b = GET_CVALUE(int64, b_ptr);
if ( ( (a > 0) && (b > 0) && (a > (INT64_MAX / b)))
|| ( (a > 0) && !(b > 0) && (b < (INT64_MIN / a)))
|| (!(a > 0) && (b > 0) && (a < (INT64_MIN / b)))
|| (!(a > 0) && !(b > 0) && (a != 0) && (b < (INT64_MAX / a))))
SET_OVFLOW(int64, res);
}
/* res = a / b */
static void CHECK_OVERFLOW_int64_DIV(symbol_c *res, symbol_c *a_ptr, symbol_c *b_ptr) {
if (!VALID_CVALUE(int64, res))
return;
int64_t a = GET_CVALUE(int64, a_ptr);
int64_t b = GET_CVALUE(int64, b_ptr);
if ((b == 0) || ((a == INT64_MIN) && (b == -1)))
SET_OVFLOW(int64, res);
}
/* res = a MOD b */
static void CHECK_OVERFLOW_int64_MOD(symbol_c *res, symbol_c *a_ptr, symbol_c *b_ptr) {
if (!VALID_CVALUE(int64, res))
return;
int64_t a = GET_CVALUE(int64, a_ptr);
int64_t b = GET_CVALUE(int64, b_ptr);
/* IEC 61131-3 standard says IN1 MOD IN2 must be equivalent to
* IF (IN2 = 0) THEN OUT:=0 ; ELSE OUT:=IN1 - (IN1/IN2)*IN2 ; END_IF
*
* Note that, when IN1 = INT64_MIN, and IN2 = -1, an overflow occurs in the division,
* so although the MOD operation should be OK, acording to the above definition, we actually have an overflow!!
*
* On the other hand, division by 0 is OK!!
*/
if ((a == INT64_MIN) && (b == -1))
SET_OVFLOW(int64, res);
}
/* res = - a */
static void CHECK_OVERFLOW_int64_NEG(symbol_c *res, symbol_c *a_ptr) {
if (!VALID_CVALUE(int64, res))
return;
int64_t a = GET_CVALUE(int64, a_ptr);
if (a == INT64_MIN)
SET_OVFLOW(int64, res);
}
static void CHECK_OVERFLOW_real64(symbol_c *res_ptr) {
if (!VALID_CVALUE(real64, res_ptr))
return;
real64_t res = GET_CVALUE(real64, res_ptr);
/* NaN => underflow, overflow, number is a higher precision format, is a complex number (IEEE standard) */
/* The IEC 61131-3 clearly states in section '2.5.1.5.2 Numerical functions':
* "It is an error if the result of evaluation of one of these [numerical] functions exceeds the range of values
* specified for the data type of the function output, or if division by zero is attempted."
* For this reason, any operation that has as a result a positive or negative inifinity, is also an error!
*/
if ((isnan(res)) || (res == INFINITY) || (res == -INFINITY))
SET_OVFLOW(real64, res_ptr);
}
/***********************************************************************/
/***********************************************************************/
/***********************************************************************/
/*** Functions to execute operations on the const values ***/
/***********************************************************************/
/***********************************************************************/
/***********************************************************************/
/* static void *handle_cmp(symbol_c *symbol, symbol_c *oper1, symbol_c *oper2, OPERATION) */
#define handle_cmp(symbol, oper1, oper2, operation) { \
if ((NULL == oper1) || (NULL == oper2)) return NULL; \
DO_BINARY_OPER_( bool, operation, bool, oper1, oper2); \
DO_BINARY_OPER_(uint64, operation, bool, oper1, oper2); \
DO_BINARY_OPER_( int64, operation, bool, oper1, oper2); \
DO_BINARY_OPER_(real64, operation, bool, oper1, oper2); \
return NULL; \
}
/* NOTE: the MOVE standard function is equivalent to the ':=' in ST syntax */
static void *handle_move(symbol_c *to, symbol_c *from) {
if (NULL == from) return NULL;
to->const_value = from->const_value;
return NULL;
}
/* unary negation (multiply by -1) */
static void *handle_neg(symbol_c *symbol, symbol_c *oper) {
DO_UNARY_OPER( int64, -, oper); CHECK_OVERFLOW_int64_NEG(symbol, oper);
/*
* NOTE : The syntax: uint_v := -<INT_MIN> may occur inside a neg_expression_c, but would always
* result in a data type error (in-> INT, out -> UINT). So, although we could handle it here,
* it is not really necessary as it will later be caught by the data type checking classes.
*/
DO_UNARY_OPER(real64, -, oper); CHECK_OVERFLOW_real64(symbol);
return NULL;
}
/* unary boolean negation (NOT) */
static void *handle_not(symbol_c *symbol, symbol_c *oper) {
if (NULL == oper) return NULL;
DO_UNARY_OPER( bool, !, oper);
DO_UNARY_OPER(uint64, ~, oper);
return NULL;
}
static void *handle_or (symbol_c *symbol, symbol_c *oper1, symbol_c *oper2) {
if ((NULL == oper1) || (NULL == oper2)) return NULL;
DO_BINARY_OPER_( bool, ||, bool , oper1, oper2);
DO_BINARY_OPER_(uint64, | , uint64, oper1, oper2);
return NULL;
}
static void *handle_xor(symbol_c *symbol, symbol_c *oper1, symbol_c *oper2) {
if ((NULL == oper1) || (NULL == oper2)) return NULL;
DO_BINARY_OPER_( bool, ^, bool , oper1, oper2);
DO_BINARY_OPER_(uint64, ^, uint64, oper1, oper2);
return NULL;
}
static void *handle_and(symbol_c *symbol, symbol_c *oper1, symbol_c *oper2) {
if ((NULL == oper1) || (NULL == oper2)) return NULL;
DO_BINARY_OPER_( bool, &&, bool, oper1, oper2);
DO_BINARY_OPER_(uint64, & , uint64, oper1, oper2);
return NULL;
}
static void *handle_add(symbol_c *symbol, symbol_c *oper1, symbol_c *oper2) {
if ((NULL == oper1) || (NULL == oper2)) return NULL;
DO_BINARY_OPER_(uint64, +, uint64, oper1, oper2); CHECK_OVERFLOW_uint64_SUM(symbol, oper1, oper2);
DO_BINARY_OPER_( int64, +, int64, oper1, oper2); CHECK_OVERFLOW_int64_SUM (symbol, oper1, oper2);
DO_BINARY_OPER_(real64, +, real64, oper1, oper2); CHECK_OVERFLOW_real64 (symbol);
return NULL;
}
static void *handle_sub(symbol_c *symbol, symbol_c *oper1, symbol_c *oper2) {
if ((NULL == oper1) || (NULL == oper2)) return NULL;
DO_BINARY_OPER_(uint64, -, uint64, oper1, oper2); CHECK_OVERFLOW_uint64_SUB(symbol, oper1, oper2);
DO_BINARY_OPER_( int64, -, int64, oper1, oper2); CHECK_OVERFLOW_int64_SUB (symbol, oper1, oper2);
DO_BINARY_OPER_(real64, -, real64, oper1, oper2); CHECK_OVERFLOW_real64 (symbol);
return NULL;
}
static void *handle_mul(symbol_c *symbol, symbol_c *oper1, symbol_c *oper2) {
if ((NULL == oper1) || (NULL == oper2)) return NULL;
DO_BINARY_OPER_(uint64, *, uint64, oper1, oper2); CHECK_OVERFLOW_uint64_MUL(symbol, oper1, oper2);
DO_BINARY_OPER_( int64, *, int64, oper1, oper2); CHECK_OVERFLOW_int64_MUL (symbol, oper1, oper2);
DO_BINARY_OPER_(real64, *, real64, oper1, oper2); CHECK_OVERFLOW_real64 (symbol);
return NULL;
}
static void *handle_div(symbol_c *symbol, symbol_c *oper1, symbol_c *oper2) {
if ((NULL == oper1) || (NULL == oper2)) return NULL;
if (ISZERO_CVALUE(uint64, oper2)) {SET_OVFLOW(uint64, symbol);} else {DO_BINARY_OPER_(uint64, /, uint64, oper1, oper2); CHECK_OVERFLOW_uint64_DIV(symbol, oper1, oper2);};
if (ISZERO_CVALUE( int64, oper2)) {SET_OVFLOW( int64, symbol);} else {DO_BINARY_OPER_( int64, /, int64, oper1, oper2); CHECK_OVERFLOW_int64_DIV (symbol, oper1, oper2);};
if (ISZERO_CVALUE(real64, oper2)) {SET_OVFLOW(real64, symbol);} else {DO_BINARY_OPER_(real64, /, real64, oper1, oper2); CHECK_OVERFLOW_real64(symbol);};
return NULL;
}
static void *handle_mod(symbol_c *symbol, symbol_c *oper1, symbol_c *oper2) {
if ((NULL == oper1) || (NULL == oper2)) return NULL;
/* IEC 61131-3 standard says IN1 MOD IN2 must be equivalent to
* IF (IN2 = 0) THEN OUT:=0 ; ELSE OUT:=IN1 - (IN1/IN2)*IN2 ; END_IF
*
* Note that, when IN1 = INT64_MIN, and IN2 = -1, an overflow occurs in the division,
* so although the MOD operation should be OK, acording to the above definition, we actually have an overflow!!
*/
if (ISZERO_CVALUE(uint64, oper2)) {SET_CVALUE(uint64, symbol, 0);} else {DO_BINARY_OPER_(uint64, %, uint64, oper1, oper2); CHECK_OVERFLOW_uint64_MOD(symbol, oper1, oper2);};
if (ISZERO_CVALUE( int64, oper2)) {SET_CVALUE( int64, symbol, 0);} else {DO_BINARY_OPER_( int64, %, int64, oper1, oper2); CHECK_OVERFLOW_int64_MOD (symbol, oper1, oper2);};
return NULL;
}
static void *handle_pow(symbol_c *symbol, symbol_c *oper1, symbol_c *oper2) {
/* NOTE: If the const_value in symbol->r_exp is within the limits of both int64 and uint64, then we do both operations.
* That is OK, as the result should be identicial (we do create an unnecessary CVALUE variable, but who cares?).
* If only one is valid, then that is the oper we will do!
*/
if (VALID_CVALUE(real64, oper1) && VALID_CVALUE( int64, oper2))
SET_CVALUE(real64, symbol, pow(GET_CVALUE(real64, oper1), GET_CVALUE( int64, oper2)));
if (VALID_CVALUE(real64, oper1) && VALID_CVALUE(uint64, oper2))
SET_CVALUE(real64, symbol, pow(GET_CVALUE(real64, oper1), GET_CVALUE(uint64, oper2)));
CHECK_OVERFLOW_real64(symbol);
return NULL;
}
/***********************************************************************/
/***********************************************************************/
/***********************************************************************/
/*** Helper functions for handling IL instruction lists. ***/
/***********************************************************************/
/***********************************************************************/
/***********************************************************************/
/* If the cvalues of all the prev_il_intructions have the same VALID value, then set the local cvalue to that value, otherwise, set it to NONCONST! */
#define intersect_prev_CVALUE_(dtype, symbol) { \
symbol->const_value._##dtype = symbol->prev_il_instruction[0]->const_value._##dtype; \
for (unsigned int i = 1; i < symbol->prev_il_instruction.size(); i++) { \
if (!ISEQUAL_CVALUE(dtype, symbol, symbol->prev_il_instruction[i])) \
{SET_NONCONST(dtype, symbol); break;} \
} \
}
static void intersect_prev_cvalues(il_instruction_c *symbol) {
if (symbol->prev_il_instruction.empty())
return;
intersect_prev_CVALUE_(real64, symbol);
intersect_prev_CVALUE_(uint64, symbol);
intersect_prev_CVALUE_( int64, symbol);
intersect_prev_CVALUE_( bool, symbol);
}
/***********************************************************************/
/***********************************************************************/
/***********************************************************************/
/*** The constant_folding_c ***/
/***********************************************************************/
/***********************************************************************/
/***********************************************************************/
constant_folding_c::constant_folding_c(symbol_c *symbol) {
error_count = 0;
warning_found = false;
current_display_error_level = 0;
/* check whether the platform on which the compiler is being run implements IEC 559 floating point data types. */
symbol_c null_symbol;
if (! (std::numeric_limits<real64_t>::is_iec559) )
STAGE3_WARNING(&null_symbol, &null_symbol, "The platform running the compiler does not implement IEC 60559 floating point numbers. "
"Any error and/or warning messages related to overflow/underflow of the result of operations on REAL/LREAL literals "
"(i.e. constant folding) may themselves be erroneous, although are most probably correct."
"However, more likely is the possible existance of overflow/underflow errors that are not detected.");
}
constant_folding_c::~constant_folding_c(void) {
}
int constant_folding_c::get_error_count() {
return error_count;
}
/*********************/
/* B 1.2 - Constants */
/*********************/
/******************************/
/* B 1.2.1 - Numeric Literals */
/******************************/
void *constant_folding_c::visit(real_c *symbol) {
bool overflow;
SET_CVALUE(real64, symbol, extract_real_value(symbol, &overflow));
if (overflow) SET_OVFLOW(real64, symbol);
return NULL;
}
void *constant_folding_c::visit(integer_c *symbol) {
bool overflow;
SET_CVALUE( int64, symbol, extract_int64_value (symbol, &overflow));
if (overflow) SET_OVFLOW(int64, symbol);
SET_CVALUE(uint64, symbol, extract_uint64_value(symbol, &overflow));
if (overflow) SET_OVFLOW(uint64, symbol);
return NULL;
}
void *constant_folding_c::visit(neg_real_c *symbol) {
symbol->exp->accept(*this);
DO_UNARY_OPER(real64, -, symbol->exp);
CHECK_OVERFLOW_real64(symbol);
return NULL;
}
/* | '-' integer {$$ = new neg_integer_c($2, locloc(@$));} */
void *constant_folding_c::visit(neg_integer_c *symbol) {
symbol->exp->accept(*this);
DO_UNARY_OPER(int64, -, symbol->exp);
CHECK_OVERFLOW_int64_NEG(symbol, symbol->exp);
/* NOTE 1: INT64_MIN = -(INT64_MAX + 1) ---> assuming two's complement representation!!!
* NOTE 2: if the user happens to want INT_MIN, that value will first be parsed as a positive integer, before being negated here.
* However, the positive value cannot be stored inside an int64! So, in this case, we will get the value from the uint64 cvalue.
*/
// if (INT64_MIN == -INT64_MAX - 1) // We do not really need to check that the platform uses two's complement
if (VALID_CVALUE(uint64, symbol->exp) && (GET_CVALUE(uint64, symbol->exp) == (uint64_t)INT64_MAX+1)) {
SET_CVALUE(int64, symbol, INT64_MIN);
}
/* NOTE 3: The standard allows considers the following strange syntax correct:
* int_v = ----------42;
* However, it will be parsed as multiple neg_expression_c, with a single final neg_integer_c.
* So, when parsing a neg_integer_c, we are guaranteed to always have a positive value in symbol->exp
* --> Conclusion:
* We do not need to handle the situation where we are negating the INT_MIN value, whose
* result can only be stored inside an UINT (remember that INT_MIN is < 0 !!).
*
* NOTE 4: The syntax: uint_v := -<INT_MIN> may occur inside a neg_expression_c, but would always
* result in a data type error. So, although we could handle it here, it is not really
* necessary as it will later be caught by the data type checking classes.
*/
return NULL;
}
void *constant_folding_c::visit(binary_integer_c *symbol) {
bool overflow;
SET_CVALUE( int64, symbol, extract_int64_value (symbol, &overflow));
if (overflow) SET_OVFLOW(int64, symbol);
SET_CVALUE(uint64, symbol, extract_uint64_value(symbol, &overflow));
if (overflow) SET_OVFLOW(uint64, symbol);
return NULL;
}
void *constant_folding_c::visit(octal_integer_c *symbol) {
bool overflow;
SET_CVALUE( int64, symbol, extract_int64_value (symbol, &overflow));
if (overflow) SET_OVFLOW(int64, symbol);
SET_CVALUE(uint64, symbol, extract_uint64_value(symbol, &overflow));
if (overflow) SET_OVFLOW(uint64, symbol);
return NULL;
}
void *constant_folding_c::visit(hex_integer_c *symbol) {
bool overflow;
SET_CVALUE( int64, symbol, extract_int64_value (symbol, &overflow));
if (overflow) SET_OVFLOW(int64, symbol);
SET_CVALUE(uint64, symbol, extract_uint64_value(symbol, &overflow));
if (overflow) SET_OVFLOW(uint64, symbol);
return NULL;
}
/*
integer_literal:
integer_type_name '#' signed_integer {$$ = new integer_literal_c($1, $3, locloc(@$));}
| integer_type_name '#' binary_integer {$$ = new integer_literal_c($1, $3, locloc(@$));}
| integer_type_name '#' octal_integer {$$ = new integer_literal_c($1, $3, locloc(@$));}
| integer_type_name '#' hex_integer {$$ = new integer_literal_c($1, $3, locloc(@$));}
*/
// SYM_REF2(integer_literal_c, type, value)
void *constant_folding_c::visit(integer_literal_c *symbol) {
symbol->value->accept(*this);
DO_UNARY_OPER( int64, /* none */, symbol->value);
DO_UNARY_OPER(uint64, /* none */, symbol->value);
return NULL;
}
void *constant_folding_c::visit(real_literal_c *symbol) {
symbol->value->accept(*this);
DO_UNARY_OPER(real64, /* none */, symbol->value);
return NULL;
}
void *constant_folding_c::visit(bit_string_literal_c *symbol) {
return NULL;
}
void *constant_folding_c::visit(boolean_literal_c *symbol) {
symbol->value->accept(*this);
DO_UNARY_OPER(bool, /* none */, symbol->value);
return NULL;
}
void *constant_folding_c::visit(boolean_true_c *symbol) {
SET_CVALUE(bool, symbol, true);
return NULL;
}
void *constant_folding_c::visit(boolean_false_c *symbol) {
SET_CVALUE(bool, symbol, false);
return NULL;
}
/****************************************/
/* B.2 - Language IL (Instruction List) */
/****************************************/
/***********************************/
/* B 2.1 Instructions and Operands */
/***********************************/
/* Not needed, since we inherit from iterator_visitor_c */
/*| instruction_list il_instruction */
// SYM_LIST(instruction_list_c)
// void *constant_folding_c::visit(instruction_list_c *symbol) {}
/* | label ':' [il_incomplete_instruction] eol_list */
// SYM_REF2(il_instruction_c, label, il_instruction)
// void *visit(instruction_list_c *symbol);
void *constant_folding_c::visit(il_instruction_c *symbol) {
if (NULL == symbol->il_instruction) {
/* This empty/null il_instruction does not change the value of the current/default IL variable.
* So it inherits the candidate_datatypes from it's previous IL instructions!
*/
intersect_prev_cvalues(symbol);
} else {
il_instruction_c fake_prev_il_instruction = *symbol;
intersect_prev_cvalues(&fake_prev_il_instruction);
if (symbol->prev_il_instruction.size() == 0) prev_il_instruction = NULL;
else prev_il_instruction = &fake_prev_il_instruction;
symbol->il_instruction->accept(*this);
prev_il_instruction = NULL;
/* This object has (inherits) the same cvalues as the il_instruction */
symbol->const_value = symbol->il_instruction->const_value;
}
return NULL;
}
void *constant_folding_c::visit(il_simple_operation_c *symbol) {
/* determine the cvalue of the operand */
if (NULL != symbol->il_operand) {
symbol->il_operand->accept(*this);
}
/* determine the cvalue resulting from executing the il_operator... */
il_operand = symbol->il_operand;
symbol->il_simple_operator->accept(*this);
il_operand = NULL;
/* This object has (inherits) the same cvalues as the il_instruction */
symbol->const_value = symbol->il_simple_operator->const_value;
return NULL;
}
/* TODO: handle function invocations... */
/* | function_name [il_operand_list] */
/* NOTE: The parameters 'called_function_declaration' and 'extensible_param_count' are used to pass data between the stage 3 and stage 4. */
// SYM_REF2(il_function_call_c, function_name, il_operand_list, symbol_c *called_function_declaration; int extensible_param_count;)
// void *constant_folding_c::visit(il_function_call_c *symbol) {}
/* | il_expr_operator '(' [il_operand] eol_list [simple_instr_list] ')' */
// SYM_REF3(il_expression_c, il_expr_operator, il_operand, simple_instr_list);
void *constant_folding_c::visit(il_expression_c *symbol) {
symbol_c *prev_il_instruction_backup = prev_il_instruction;
if (NULL != symbol->il_operand)
symbol->il_operand->accept(*this);
if(symbol->simple_instr_list != NULL)
symbol->simple_instr_list->accept(*this);
/* Now do the operation, */
il_operand = symbol->simple_instr_list;
prev_il_instruction = prev_il_instruction_backup;
symbol->il_expr_operator->accept(*this);
il_operand = NULL;
/* This object has (inherits) the same cvalues as the il_instruction */
symbol->const_value = symbol->il_expr_operator->const_value;
return NULL;
}
void *constant_folding_c::visit(il_jump_operation_c *symbol) {
/* recursive call to fill const values... */
il_operand = NULL;
symbol->il_jump_operator->accept(*this);
il_operand = NULL;
/* This object has (inherits) the same cvalues as the il_jump_operator */
symbol->const_value = symbol->il_jump_operator->const_value;
return NULL;
}
/* FB calls leave the value in the accumulator unchanged */
/* il_call_operator prev_declared_fb_name
* | il_call_operator prev_declared_fb_name '(' ')'
* | il_call_operator prev_declared_fb_name '(' eol_list ')'
* | il_call_operator prev_declared_fb_name '(' il_operand_list ')'
* | il_call_operator prev_declared_fb_name '(' eol_list il_param_list ')'
*/
/* NOTE: The parameter 'called_fb_declaration'is used to pass data between stage 3 and stage4 (although currently it is not used in stage 4 */
// SYM_REF4(il_fb_call_c, il_call_operator, fb_name, il_operand_list, il_param_list, symbol_c *called_fb_declaration)
void *constant_folding_c::visit(il_fb_call_c *symbol) {return handle_move(symbol, prev_il_instruction);}
/* TODO: handle function invocations... */
/* | function_name '(' eol_list [il_param_list] ')' */
/* NOTE: The parameter 'called_function_declaration' is used to pass data between the stage 3 and stage 4. */
// SYM_REF2(il_formal_funct_call_c, function_name, il_param_list, symbol_c *called_function_declaration; int extensible_param_count;)
// void *constant_folding_c::visit(il_formal_funct_call_c *symbol) {return NULL;}
/* Not needed, since we inherit from iterator_visitor_c */
// void *constant_folding_c::visit(il_operand_list_c *symbol);
/* | simple_instr_list il_simple_instruction */
/* This object is referenced by il_expression_c objects */
void *constant_folding_c::visit(simple_instr_list_c *symbol) {
if (symbol->n <= 0)
return NULL; /* List is empty! Nothing to do. */
for(int i = 0; i < symbol->n; i++)
symbol->elements[i]->accept(*this);
/* This object has (inherits) the same cvalues as the il_jump_operator */
symbol->const_value = symbol->elements[symbol->n-1]->const_value;
return NULL;
}
// SYM_REF1(il_simple_instruction_c, il_simple_instruction, symbol_c *prev_il_instruction;)
void *constant_folding_c::visit(il_simple_instruction_c *symbol) {
if (symbol->prev_il_instruction.size() > 1) ERROR; /* There should be no labeled insructions inside an IL expression! */
if (symbol->prev_il_instruction.size() == 0) prev_il_instruction = NULL;
else prev_il_instruction = symbol->prev_il_instruction[0];
symbol->il_simple_instruction->accept(*this);
prev_il_instruction = NULL;
/* This object has (inherits) the same cvalues as the il_jump_operator */
symbol->const_value = symbol->il_simple_instruction->const_value;
return NULL;
}
/*
void *visit(il_param_list_c *symbol);
void *visit(il_param_assignment_c *symbol);
void *visit(il_param_out_assignment_c *symbol);
*/
/*******************/
/* B 2.2 Operators */
/*******************/
void *constant_folding_c::visit( LD_operator_c *symbol) {return handle_move(symbol, il_operand);}
void *constant_folding_c::visit( LDN_operator_c *symbol) {return handle_not (symbol, il_operand);}
/* NOTE: we are implementing a constant folding algorithm, not a constant propagation algorithm.
* For the constant propagation algorithm, the correct implementation of ST(N)_operator_c would be...
*/
//void *constant_folding_c::visit( ST_operator_c *symbol) {return handle_move(il_operand, symbol);}
//void *constant_folding_c::visit( STN_operator_c *symbol) {return handle_not (il_operand, symbol);}
void *constant_folding_c::visit( ST_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
void *constant_folding_c::visit( STN_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
/* NOTE: the standard allows syntax in which the NOT operator is followed by an optional <il_operand>
* NOT [<il_operand>]
* However, it does not define the semantic of the NOT operation when the <il_operand> is specified.
* We therefore consider it an error if an il_operand is specified! This error will be caught elsewhere!
*/
void *constant_folding_c::visit( NOT_operator_c *symbol) {return handle_not(symbol, prev_il_instruction);}
/* NOTE: Since we are only implementing a constant folding algorithm, and not a constant propagation algorithm,
* the following IL instructions do not change/set the value of the il_operand!
*/
void *constant_folding_c::visit( S_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
void *constant_folding_c::visit( R_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
/* FB calls leave the value in the accumulator unchanged */
void *constant_folding_c::visit( S1_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
void *constant_folding_c::visit( R1_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
void *constant_folding_c::visit( CLK_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
void *constant_folding_c::visit( CU_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
void *constant_folding_c::visit( CD_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
void *constant_folding_c::visit( PV_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
void *constant_folding_c::visit( IN_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
void *constant_folding_c::visit( PT_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
void *constant_folding_c::visit( AND_operator_c *symbol) {return handle_and (symbol, prev_il_instruction, il_operand);}
void *constant_folding_c::visit( OR_operator_c *symbol) {return handle_or (symbol, prev_il_instruction, il_operand);}
void *constant_folding_c::visit( XOR_operator_c *symbol) {return handle_xor (symbol, prev_il_instruction, il_operand);}
void *constant_folding_c::visit( ANDN_operator_c *symbol) { handle_and (symbol, prev_il_instruction, il_operand); return handle_not(symbol, symbol);}
void *constant_folding_c::visit( ORN_operator_c *symbol) { handle_or (symbol, prev_il_instruction, il_operand); return handle_not(symbol, symbol);}
void *constant_folding_c::visit( XORN_operator_c *symbol) { handle_xor (symbol, prev_il_instruction, il_operand); return handle_not(symbol, symbol);}
void *constant_folding_c::visit( ADD_operator_c *symbol) {return handle_add (symbol, prev_il_instruction, il_operand);}
void *constant_folding_c::visit( SUB_operator_c *symbol) {return handle_sub (symbol, prev_il_instruction, il_operand);}
void *constant_folding_c::visit( MUL_operator_c *symbol) {return handle_mul (symbol, prev_il_instruction, il_operand);}
void *constant_folding_c::visit( DIV_operator_c *symbol) {return handle_div (symbol, prev_il_instruction, il_operand);}
void *constant_folding_c::visit( MOD_operator_c *symbol) {return handle_mod (symbol, prev_il_instruction, il_operand);}
void *constant_folding_c::visit( GT_operator_c *symbol) { handle_cmp (symbol, prev_il_instruction, il_operand, > );}
void *constant_folding_c::visit( GE_operator_c *symbol) { handle_cmp (symbol, prev_il_instruction, il_operand, >=);}
void *constant_folding_c::visit( EQ_operator_c *symbol) { handle_cmp (symbol, prev_il_instruction, il_operand, ==);}
void *constant_folding_c::visit( LT_operator_c *symbol) { handle_cmp (symbol, prev_il_instruction, il_operand, < );}
void *constant_folding_c::visit( LE_operator_c *symbol) { handle_cmp (symbol, prev_il_instruction, il_operand, <=);}
void *constant_folding_c::visit( NE_operator_c *symbol) { handle_cmp (symbol, prev_il_instruction, il_operand, !=);}
void *constant_folding_c::visit( CAL_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
void *constant_folding_c::visit( RET_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
void *constant_folding_c::visit( JMP_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
void *constant_folding_c::visit( CALC_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
void *constant_folding_c::visit(CALCN_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
void *constant_folding_c::visit( RETC_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
void *constant_folding_c::visit(RETCN_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
void *constant_folding_c::visit( JMPC_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
void *constant_folding_c::visit(JMPCN_operator_c *symbol) {return handle_move(symbol, prev_il_instruction);}
/***************************************/
/* B.3 - Language ST (Structured Text) */
/***************************************/
/***********************/
/* B 3.1 - Expressions */
/***********************/
void *constant_folding_c::visit( or_expression_c *symbol) {symbol->l_exp->accept(*this); symbol->r_exp->accept(*this); return handle_or (symbol, symbol->l_exp, symbol->r_exp);}
void *constant_folding_c::visit( xor_expression_c *symbol) {symbol->l_exp->accept(*this); symbol->r_exp->accept(*this); return handle_xor(symbol, symbol->l_exp, symbol->r_exp);}
void *constant_folding_c::visit( and_expression_c *symbol) {symbol->l_exp->accept(*this); symbol->r_exp->accept(*this); return handle_and(symbol, symbol->l_exp, symbol->r_exp);}
void *constant_folding_c::visit( equ_expression_c *symbol) {symbol->l_exp->accept(*this); symbol->r_exp->accept(*this); handle_cmp (symbol, symbol->l_exp, symbol->r_exp, ==);}
void *constant_folding_c::visit(notequ_expression_c *symbol) {symbol->l_exp->accept(*this); symbol->r_exp->accept(*this); handle_cmp (symbol, symbol->l_exp, symbol->r_exp, !=);}
void *constant_folding_c::visit( lt_expression_c *symbol) {symbol->l_exp->accept(*this); symbol->r_exp->accept(*this); handle_cmp (symbol, symbol->l_exp, symbol->r_exp, < );}
void *constant_folding_c::visit( gt_expression_c *symbol) {symbol->l_exp->accept(*this); symbol->r_exp->accept(*this); handle_cmp (symbol, symbol->l_exp, symbol->r_exp, > );}
void *constant_folding_c::visit( le_expression_c *symbol) {symbol->l_exp->accept(*this); symbol->r_exp->accept(*this); handle_cmp (symbol, symbol->l_exp, symbol->r_exp, <=);}
void *constant_folding_c::visit( ge_expression_c *symbol) {symbol->l_exp->accept(*this); symbol->r_exp->accept(*this); handle_cmp (symbol, symbol->l_exp, symbol->r_exp, >=);}
void *constant_folding_c::visit( add_expression_c *symbol) {symbol->l_exp->accept(*this); symbol->r_exp->accept(*this); return handle_add(symbol, symbol->l_exp, symbol->r_exp);}
void *constant_folding_c::visit( sub_expression_c *symbol) {symbol->l_exp->accept(*this); symbol->r_exp->accept(*this); return handle_sub(symbol, symbol->l_exp, symbol->r_exp);}
void *constant_folding_c::visit( mul_expression_c *symbol) {symbol->l_exp->accept(*this); symbol->r_exp->accept(*this); return handle_mul(symbol, symbol->l_exp, symbol->r_exp);}
void *constant_folding_c::visit( div_expression_c *symbol) {symbol->l_exp->accept(*this); symbol->r_exp->accept(*this); return handle_div(symbol, symbol->l_exp, symbol->r_exp);}
void *constant_folding_c::visit( mod_expression_c *symbol) {symbol->l_exp->accept(*this); symbol->r_exp->accept(*this); return handle_mod(symbol, symbol->l_exp, symbol->r_exp);}
void *constant_folding_c::visit( power_expression_c *symbol) {symbol->l_exp->accept(*this); symbol->r_exp->accept(*this); return handle_pow(symbol, symbol->l_exp, symbol->r_exp);}
void *constant_folding_c::visit( neg_expression_c *symbol) {symbol-> exp->accept(*this); return handle_neg(symbol, symbol->exp);}
void *constant_folding_c::visit( not_expression_c *symbol) {symbol-> exp->accept(*this); return handle_not(symbol, symbol->exp);}
/* TODO: handle function invocations... */
// void *fill_candidate_datatypes_c::visit(function_invocation_c *symbol) {}