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/*
                 Crown Copyright (c) 1997
    
    This TenDRA(r) Computer Program is subject to Copyright
    owned by the United Kingdom Secretary of State for Defence
    acting through the Defence Evaluation and Research Agency
    (DERA).  It is made available to Recipients with a
    royalty-free licence for its use, reproduction, transfer
    to other parties and amendment for any purpose not excluding
    product development provided that any such use et cetera
    shall be deemed to be acceptance of the following conditions:-
    
        (1) Its Recipients shall ensure that this Notice is
        reproduced upon any copies or amended versions of it;
    
        (2) Any amended version of it shall be clearly marked to
        show both the nature of and the organisation responsible
        for the relevant amendment or amendments;
    
        (3) Its onward transfer from a recipient to another
        party shall be deemed to be that party's acceptance of
        these conditions;
    
        (4) DERA gives no warranty or assurance as to its
        quality or suitability for any purpose and DERA accepts
        no liability whatsoever in relation to any use to which
        it may be put.
*/


#include "config.h"
#include "c_types.h"
#include "exp_ops.h"
#include "error.h"
#include "catalog.h"
#include "operator.h"
#include "quality.h"
#include "syntax.h"


/*
    CHECKING CONTROL FLAG

    This flag may be set to true to temporarily disable the checks in
    this module.
*/

int suppress_quality = 0 ;


/*
    TABLE OF OPERATIONS

    This table gives the list of operations checked by check_paren.  They
    are listed in order of decreasing precedence.  Calls to check_paren
    give an entry point into this table beyond which checks are applied.
    For example, left shift operations are checked from PAREN_PLUS which
    detects 'a << b + c', 'a << b - c', 'a + b << c' and 'a - b << c'.
*/

static struct {
    unsigned tag ;
    int op ;
} paren_ops [] = {
    { exp_or_tag, lex_or_H1 },          /* PAREN_OR */
    { exp_xor_tag, lex_xor_H1 },                /* PAREN_XOR */
    { exp_and_tag, lex_and_H1 },                /* PAREN_AND */
    { exp_compare_tag, lex_eq },        /* PAREN_EQUALITY */
    { exp_test_tag, lex_eq },           /* PAREN_RELATION */
    { exp_plus_tag, lex_plus },         /* PAREN_PLUS */
    { exp_minus_tag, lex_minus }        /* PAREN_MINUS */
} ;


/*
    FIND AN EXPRESSION TAG

    This routine finds the tag associated with the expression e for unusual
    parenthesis analysis etc.  Note that an integer constant expression may
    have been evaluated to give a simple integer constant, however the top
    level operation giving rise to this constant is held in the etag field.
*/

static unsigned exp_tag
    PROTO_N ( ( e ) )
    PROTO_T ( EXP e )
{
    unsigned tag = TAG_exp ( e ) ;
    if ( tag == exp_int_lit_tag ) {
        /* Allow for evaluated constants */
        tag = DEREF_unsigned ( exp_int_lit_etag ( e ) ) ;
    }
    return ( tag ) ;
}


/*
    CHECK FOR DUBIOUS SHIFTS AND BIT OPERATIONS

    For various pairs of operations, op1 and op2, the resolution of the
    expression 'a op1 b op2 c' to '( a op1 b ) op2 c' or 'a op1 ( b op2 c )'
    is not obvious.  This routine checks whether the expression 'a op b'
    is of this form, checking the operations starting from position n in
    the table paren_ops.
*/

void check_paren
    PROTO_N ( ( n, op, a, b ) )
    PROTO_T ( int n X int op X EXP a X EXP b )
{
    if ( !suppress_quality ) {
        int i ;

        /* Check first operand */
        unsigned tag = exp_tag ( a ) ;
        for ( i = n ; i < array_size ( paren_ops ) ; i++ ) {
            if ( tag == paren_ops [i].tag ) {
                int op1 = paren_ops [i].op ;
                if ( op1 == lex_eq ) op1 = op_token ( a, op1 ) ;
                report ( crt_loc, ERR_expr_paren_left ( op1, op ) ) ;
                break ;
            }
        }

        /* Check second operand */
        tag = exp_tag ( b ) ;
        for ( i = n ; i < array_size ( paren_ops ) ; i++ ) {
            if ( tag == paren_ops [i].tag ) {
                int op2 = paren_ops [i].op ;
                if ( op2 == lex_eq ) op2 = op_token ( b, op2 ) ;
                report ( crt_loc, ERR_expr_paren_right ( op, op2 ) ) ;
                break ;
            }
        }
    }
    return ;
}


/*
    CHECK FOR DUBIOUS RELATIONS

    This routine checks for dubious relations such as 'a < b < c' which
    do not have their mathematical meaning.
*/

void check_relation
    PROTO_N ( ( op, a, b ) )
    PROTO_T ( int op X EXP a X EXP b )
{
    if ( !suppress_quality ) {
        /* Check first operand */
        unsigned tag = exp_tag ( a ) ;
        if ( tag == exp_compare_tag ) {
            int tst = op_token ( a, op ) ;
            report ( crt_loc, ERR_expr_rel_paren ( tst, op ) ) ;
        } else if ( tag == exp_test_tag ) {
            int tst = op_token ( a, op ) ;
            report ( crt_loc, ERR_expr_rel_paren ( tst, op ) ) ;
        }

        /* Check second operand */
        tag = exp_tag ( b ) ;
        if ( tag == exp_compare_tag ) {
            int tst = op_token ( b, op ) ;
            report ( crt_loc, ERR_expr_rel_paren ( op, tst ) ) ;
        } else if ( tag == exp_test_tag ) {
            int tst = op_token ( b, op ) ;
            report ( crt_loc, ERR_expr_rel_paren ( op, tst ) ) ;
        }
    }
    return ;
}


/*
    CHECK FOR DUBIOUS LOGICAL EXPRESSIONS

    The resolution of 'a && b || c' to '( a && b ) || c' is odd.  This
    routine checks a logical or expression to see if it is of this form.
*/

void check_logic
    PROTO_N ( ( a, b ) )
    PROTO_T ( EXP a X EXP b )
{
    if ( !suppress_quality ) {
        if ( exp_tag ( a ) == exp_log_and_tag ) {
            int op1 = lex_logical_Hand_H1 ;
            int op2 = lex_logical_Hor_H1 ;
            report ( crt_loc, ERR_expr_paren_left ( op1, op2 ) ) ;
        }
        if ( exp_tag ( b ) == exp_log_and_tag ) {
            int op1 = lex_logical_Hor_H1 ;
            int op2 = lex_logical_Hand_H1 ;
            report ( crt_loc, ERR_expr_paren_right ( op1, op2 ) ) ;
        }
    }
    return ;
}