/* m2convert.cc provides GCC tree conversion for the Modula-2 language.

Copyright (C) 2012-2023 Free Software Foundation, Inc.
Contributed by Gaius Mulley <gaius@glam.ac.uk>.

This file is part of GNU Modula-2.

GNU Modula-2 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, or (at your option)
any later version.

GNU Modula-2 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 GNU Modula-2; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#include "gcc-consolidation.h"

#include "../gm2-lang.h"
#include "../m2-tree.h"

#define m2convert_c
#include "m2assert.h"
#include "m2block.h"
#include "m2convert.h"
#include "m2decl.h"
#include "m2expr.h"
#include "m2expr.h"
#include "m2statement.h"
#include "m2tree.h"
#include "m2treelib.h"
#include "m2type.h"

static tree const_to_ISO_type (location_t location, tree expr, tree iso_type);
static tree const_to_ISO_aggregate_type (location_t location, tree expr,
                                         tree iso_type);

/* These enumerators are possible types of unsafe conversions.
   SAFE_CONVERSION The conversion is safe UNSAFE_OTHER Another type of
   conversion with problems UNSAFE_SIGN Conversion between signed and
   unsigned integers which are all warned about immediately, so this is
   unused UNSAFE_REAL Conversions that reduce the precision of reals
   including conversions from reals to integers.  */
enum conversion_safety
{
  SAFE_CONVERSION = 0,
  UNSAFE_OTHER,
  UNSAFE_SIGN,
  UNSAFE_REAL
};

/* ConvertString - converts string, expr, into a string of type,
   type.  */

tree
m2convert_ConvertString (tree type, tree expr)
{
  const char *str = TREE_STRING_POINTER (expr);
  int len = TREE_STRING_LENGTH (expr);
  return m2decl_BuildStringConstantType (len, str, type);
}


/* (Taken from c-common.cc and trimmed for Modula-2)

   Checks if expression EXPR of real/integer type cannot be converted to
   the real/integer type TYPE.  Function returns non-zero when:
   EXPR is a constant which cannot be exactly converted to TYPE.
   EXPR is not a constant and size of EXPR's type > than size of
   TYPE, for EXPR type and TYPE being both integers or both real.
   EXPR is not a constant of real type and TYPE is an integer.
   EXPR is not a constant of integer type which cannot be exactly
   converted to real type.  Function allows conversions between types
   of different signedness and can return SAFE_CONVERSION (zero) in
   that case.  Function can produce signedness warnings if
   PRODUCE_WARNS is true.  */

enum conversion_safety
unsafe_conversion_p (location_t loc, tree type, tree expr, bool produce_warns)
{
  enum conversion_safety give_warning = SAFE_CONVERSION; /* Is 0 or false.  */
  tree expr_type = TREE_TYPE (expr);

  if (TREE_CODE (expr) == REAL_CST || TREE_CODE (expr) == INTEGER_CST)
    {

      /* Warn for real constant that is not an exact integer converted to
         integer type.  */
      if (TREE_CODE (expr_type) == REAL_TYPE
          && TREE_CODE (type) == INTEGER_TYPE)
        {
          if (!real_isinteger (TREE_REAL_CST_PTR (expr),
                               TYPE_MODE (expr_type)))
            give_warning = UNSAFE_REAL;
        }
      /* Warn for an integer constant that does not fit into integer type.  */
      else if (TREE_CODE (expr_type) == INTEGER_TYPE
               && TREE_CODE (type) == INTEGER_TYPE
               && !int_fits_type_p (expr, type))
        {
          if (TYPE_UNSIGNED (type) && !TYPE_UNSIGNED (expr_type)
              && tree_int_cst_sgn (expr) < 0)
            {
              if (produce_warns)
                warning_at (loc, OPT_Wsign_conversion,
                            "negative integer"
                            " implicitly converted to unsigned type");
            }
          else if (!TYPE_UNSIGNED (type) && TYPE_UNSIGNED (expr_type))
            {
              if (produce_warns)
                warning_at (loc, OPT_Wsign_conversion,
                            "conversion of unsigned"
                            " constant value to negative integer");
            }
          else
            give_warning = UNSAFE_OTHER;
        }
      else if (TREE_CODE (type) == REAL_TYPE)
        {
          /* Warn for an integer constant that does not fit into real type.  */
          if (TREE_CODE (expr_type) == INTEGER_TYPE)
            {
              REAL_VALUE_TYPE a = real_value_from_int_cst (0, expr);
              if (!exact_real_truncate (TYPE_MODE (type), &a))
                give_warning = UNSAFE_REAL;
            }

          /* Warn for a real constant that does not fit into a smaller real
          type.  */
          else if (TREE_CODE (expr_type) == REAL_TYPE
                   && TYPE_PRECISION (type) < TYPE_PRECISION (expr_type))
            {
              REAL_VALUE_TYPE a = TREE_REAL_CST (expr);
              if (!exact_real_truncate (TYPE_MODE (type), &a))
                give_warning = UNSAFE_REAL;
            }
        }
    }
  else
    {
      /* Warn for real types converted to integer types.  */
      if (TREE_CODE (expr_type) == REAL_TYPE
          && TREE_CODE (type) == INTEGER_TYPE)
        give_warning = UNSAFE_REAL;

    }

  return give_warning;
}

/* (Taken from c-common.cc and trimmed for Modula-2)

   Warns if the conversion of EXPR to TYPE may alter a value.  This is
   a helper function for warnings_for_convert_and_check.  */

static void
conversion_warning (location_t loc, tree type, tree expr)
{
  tree expr_type = TREE_TYPE (expr);
  enum conversion_safety conversion_kind;

  if (!warn_conversion && !warn_sign_conversion && !warn_float_conversion)
    return;

  switch (TREE_CODE (expr))
    {
    case EQ_EXPR:
    case NE_EXPR:
    case LE_EXPR:
    case GE_EXPR:
    case LT_EXPR:
    case GT_EXPR:
    case TRUTH_ANDIF_EXPR:
    case TRUTH_ORIF_EXPR:
    case TRUTH_AND_EXPR:
    case TRUTH_OR_EXPR:
    case TRUTH_XOR_EXPR:
    case TRUTH_NOT_EXPR:

      /* Conversion from boolean to a signed:1 bit-field (which only can
	 hold the values 0 and -1) doesn't lose information - but it does
	 change the value.  */
      if (TYPE_PRECISION (type) == 1 && !TYPE_UNSIGNED (type))
        warning_at (loc, OPT_Wconversion,
                    "conversion to %qT from boolean expression", type);
      return;

    case REAL_CST:
    case INTEGER_CST:
      conversion_kind = unsafe_conversion_p (loc, type, expr, true);
      if (conversion_kind == UNSAFE_REAL)
        warning_at (loc, OPT_Wfloat_conversion,
                    "conversion to %qT alters %qT constant value", type,
                    expr_type);
      else if (conversion_kind)
        warning_at (loc, OPT_Wconversion,
                    "conversion to %qT alters %qT constant value", type,
                    expr_type);
      return;

    case COND_EXPR:
      {

        /* In case of COND_EXPR, we do not care about the type of COND_EXPR,
	   only about the conversion of each operand.  */
        tree op1 = TREE_OPERAND (expr, 1);
        tree op2 = TREE_OPERAND (expr, 2);

        conversion_warning (loc, type, op1);
        conversion_warning (loc, type, op2);
        return;
      }

    default:  /* 'expr' is not a constant.  */
      conversion_kind = unsafe_conversion_p (loc, type, expr, true);
      if (conversion_kind == UNSAFE_REAL)
        warning_at (loc, OPT_Wfloat_conversion,
                    "conversion to %qT from %qT may alter its value", type,
                    expr_type);
      else if (conversion_kind)
        warning_at (loc, OPT_Wconversion,
                    "conversion to %qT from %qT may alter its value", type,
                    expr_type);
    }
}

/* (Taken from c-common.cc and trimmed for Modula-2)

   Produce warnings after a conversion.  RESULT is the result of
   converting EXPR to TYPE.  This is a helper function for
   convert_and_check and cp_convert_and_check.  */

void
warnings_for_convert_and_check (location_t loc, tree type, tree expr,
                                tree result)
{
  if (TREE_CODE (expr) == INTEGER_CST && (TREE_CODE (type) == INTEGER_TYPE
                                          || TREE_CODE (type) == ENUMERAL_TYPE)
      && !int_fits_type_p (expr, type))
    {

      /* Do not diagnose overflow in a constant expression merely because a
	 conversion overflowed.  */
      if (TREE_OVERFLOW (result))
        TREE_OVERFLOW (result) = TREE_OVERFLOW (expr);

      if (TYPE_UNSIGNED (type))
        {

          /* This detects cases like converting -129 or 256 to unsigned
	     char.  */
          if (!int_fits_type_p (expr, m2type_gm2_signed_type (type)))
            warning_at (loc, OPT_Woverflow,
                        "large integer implicitly truncated to unsigned type");
          else
            conversion_warning (loc, type, expr);
        }
      else if (!int_fits_type_p (expr, m2type_gm2_unsigned_type (type)))
        warning_at (loc, OPT_Woverflow,
                    "overflow in implicit constant conversion");
      /* No warning for converting 0x80000000 to int.  */
      else if (pedantic && (TREE_CODE (TREE_TYPE (expr)) != INTEGER_TYPE
                            || TYPE_PRECISION (TREE_TYPE (expr))
                                   != TYPE_PRECISION (type)))
        warning_at (loc, OPT_Woverflow,
                    "overflow in implicit constant conversion");

      else
        conversion_warning (loc, type, expr);
    }
  else if ((TREE_CODE (result) == INTEGER_CST
            || TREE_CODE (result) == FIXED_CST)
           && TREE_OVERFLOW (result))
    warning_at (loc, OPT_Woverflow,
                "overflow in implicit constant conversion");
  else
    conversion_warning (loc, type, expr);
}

/* (Taken from c-common.cc and trimmed for Modula-2)

   Convert EXPR to TYPE, warning about conversion problems with
   constants.  Invoke this function on every expression that is
   converted implicitly, i.e.  because of language rules and not
   because of an explicit cast.  */

static tree
convert_and_check (location_t loc, tree type, tree expr)
{
  tree result;
  tree expr_for_warning;

  /* Convert from a value with possible excess precision rather than
     via the semantic type, but do not warn about values not fitting
     exactly in the semantic type.  */
  if (TREE_CODE (expr) == EXCESS_PRECISION_EXPR)
    {
      tree orig_type = TREE_TYPE (expr);
      expr = TREE_OPERAND (expr, 0);
      expr_for_warning = convert (orig_type, expr);
      if (orig_type == type)
        return expr_for_warning;
    }
  else
    expr_for_warning = expr;

  if (TREE_TYPE (expr) == type)
    return expr;

  result = convert_loc (loc, type, expr);

  if (!TREE_OVERFLOW_P (expr) && result != error_mark_node)
    warnings_for_convert_and_check (loc, type, expr_for_warning, result);

  return result;
}


static tree
doOrdinal (tree value)
{
  if (TREE_CODE (value) == STRING_CST && (m2expr_StringLength (value) <= 1))
    {
      const char *p = TREE_STRING_POINTER (value);
      int i = p[0];

      return m2decl_BuildIntegerConstant (i);
    }
  return value;
}

static int
same_size_types (location_t location, tree t1, tree t2)
{
  tree n1 = m2expr_GetSizeOf (location, t1);
  tree n2 = m2expr_GetSizeOf (location, t2);

  return m2expr_CompareTrees (n1, n2) == 0;
}

static int
converting_ISO_generic (location_t location, tree type, tree value,
                        tree generic_type, tree *result)
{
  tree value_type = m2tree_skip_type_decl (TREE_TYPE (value));

  if (value_type == type)
    /* We let the caller deal with this.  */
    return false;

  if ((TREE_CODE (value) == INTEGER_CST) && (type == generic_type))
    {
      *result = const_to_ISO_type (location, value, generic_type);
      return true;
    }

  if (same_size_types (location, type, value_type))
    {
      if (value_type == generic_type)
        {
          tree pt = build_pointer_type (type);
          tree a = build1 (ADDR_EXPR, pt, value);
          tree t = build1 (INDIRECT_REF, type, a);
          *result = build1 (NOP_EXPR, type, t);
          return true;
        }
      else if (type == generic_type)
        {
          tree pt = build_pointer_type (type);
          tree a = build1 (ADDR_EXPR, pt, value);
          tree t = build1 (INDIRECT_REF, type, a);
          *result = build1 (NOP_EXPR, type, t);
          return true;
        }
    }
  return false;
}

/* convert_char_to_array - convert a single char, value, into an
   type.  The type will be array [..] of char.  The array type
   returned will have nuls appended to pad the single char to the
   correct array length.  */

static tree
convert_char_to_array (location_t location, tree type, tree value)
{
  tree i = m2decl_BuildIntegerConstant (0);
  struct struct_constructor *c
      = (struct struct_constructor *)m2type_BuildStartArrayConstructor (type);
  tree n = m2type_GetArrayNoOfElements (location, type);
  char nul[1];

  nul[0] = (char)0;

  /* Store the initial char.  */
  m2type_BuildArrayConstructorElement (c, value, i);
  i = m2expr_BuildAdd (location, i, m2decl_BuildIntegerConstant (1), false);

  /* Now pad out the remaining elements with nul chars.  */
  while (m2expr_CompareTrees (i, n) < 0)
    {
      m2type_BuildArrayConstructorElement (
          c, m2type_BuildCharConstant (location, &nul[0]), i);
      i = m2expr_BuildAdd (location, i, m2decl_BuildIntegerConstant (1),
                           false);
    }
  return m2type_BuildEndArrayConstructor (c);
}

/* convert_string_to_array - convert a STRING_CST into an array type.
   array [..] of char.  The array constant returned will have nuls
   appended to pad the contents to the correct length.  */

static tree
convert_string_to_array (location_t location, tree type, tree value)
{
  tree n = m2type_GetArrayNoOfElements (location, type);

  return m2type_BuildArrayStringConstructor (location, type, value, n);
}

/* BuildConvert - build and return tree VAL (type, value).
   checkOverflow determines whether we should suppress overflow
   checking.  */

tree
m2convert_BuildConvert (location_t location, tree type, tree value,
                        bool checkOverflow)
{
  type = m2tree_skip_type_decl (type);
  tree t;

  value = fold (value);
  STRIP_NOPS (value);
  value = m2expr_FoldAndStrip (value);

  if (TREE_CODE (value) == STRING_CST && (m2expr_StringLength (value) <= 1)
      && (m2tree_IsOrdinal (type)))
    value = doOrdinal (value);
  else if (TREE_CODE (value) == FUNCTION_DECL && TREE_TYPE (value) != type)
    value = m2expr_BuildAddr (0, value, false);

  if (converting_ISO_generic (location, type, value, m2type_GetByteType (), &t)
      || converting_ISO_generic (location, type, value,
                                 m2type_GetISOLocType (), &t)
      || converting_ISO_generic (location, type, value,
                                 m2type_GetISOByteType (), &t)
      || converting_ISO_generic (location, type, value,
                                 m2type_GetISOWordType (), &t)
      || converting_ISO_generic (location, type, value, m2type_GetM2Word16 (),
                                 &t)
      || converting_ISO_generic (location, type, value, m2type_GetM2Word32 (),
                                 &t)
      || converting_ISO_generic (location, type, value, m2type_GetM2Word64 (),
                                 &t))
    return t;

  if (TREE_CODE (type) == ARRAY_TYPE
      && TREE_TYPE (type) == m2type_GetM2CharType ())
    {
      if (TREE_TYPE (value) == m2type_GetM2CharType ())

        /* Passing a const char to an array [..] of char.  So we convert
	   const char into the correct length string.  */
        return convert_char_to_array (location, type, value);
      if (TREE_CODE (value) == STRING_CST)
        /* Convert a string into an array constant, padding with zeros if
           necessary.  */
        return convert_string_to_array (location, type, value);
    }

  if (checkOverflow)
    return convert_and_check (location, type, value);
  else
    return convert (type, value);
}

/* const_to_ISO_type - perform VAL (iso_type, expr).  */

static tree
const_to_ISO_type (location_t location, tree expr, tree iso_type)
{
  tree n = m2expr_GetSizeOf (location, iso_type);

  if ((m2expr_CompareTrees (n, m2decl_BuildIntegerConstant (1)) == 0)
      && (iso_type == m2type_GetByteType ()
          || iso_type == m2type_GetISOLocType ()
          || iso_type == m2type_GetISOByteType ()))
    return build1 (NOP_EXPR, iso_type, expr);
  return const_to_ISO_aggregate_type (location, expr, iso_type);
}

/* const_to_ISO_aggregate_type - perform VAL (iso_type, expr).  The
   iso_type will be declared by the SYSTEM module as: TYPE iso_type =
   ARRAY [0..n] OF LOC

   this function will store a constant into the iso_type in the correct
   endian order.  It converts the expr into a unsigned int or signed
   int and then strips it a byte at a time.  */

static tree
const_to_ISO_aggregate_type (location_t location, tree expr, tree iso_type)
{
  tree byte;
  m2type_Constructor c;
  tree i = m2decl_BuildIntegerConstant (0);
  tree n = m2expr_GetSizeOf (location, iso_type);
  tree max_uint = m2decl_BuildIntegerConstant (256);

  while (m2expr_CompareTrees (i, n) < 0)
    {
      max_uint = m2expr_BuildMult (location, max_uint,
                                   m2decl_BuildIntegerConstant (256), false);
      i = m2expr_BuildAdd (location, i, m2decl_BuildIntegerConstant (1),
                           false);
    }
  max_uint = m2expr_BuildDivFloor (location, max_uint,
                                   m2decl_BuildIntegerConstant (2), false);

  if (m2expr_CompareTrees (expr, m2decl_BuildIntegerConstant (0)) < 0)
    expr = m2expr_BuildAdd (location, expr, max_uint, false);

  i = m2decl_BuildIntegerConstant (0);
  c = m2type_BuildStartArrayConstructor (iso_type);
  while (m2expr_CompareTrees (i, n) < 0)
    {
      byte = m2expr_BuildModTrunc (location, expr,
                                   m2decl_BuildIntegerConstant (256), false);
      if (BYTES_BIG_ENDIAN)
        m2type_BuildArrayConstructorElement (
            c, m2convert_ToLoc (location, byte),
            m2expr_BuildSub (location, m2expr_BuildSub (location, n, i, false),
                             m2decl_BuildIntegerConstant (1), false));
      else
        m2type_BuildArrayConstructorElement (
            c, m2convert_ToLoc (location, byte), i);

      i = m2expr_BuildAdd (location, i, m2decl_BuildIntegerConstant (1),
                           false);
      expr = m2expr_BuildDivFloor (location, expr,
                                   m2decl_BuildIntegerConstant (256), false);
    }

  return m2type_BuildEndArrayConstructor (c);
}

/* ConvertConstantAndCheck - in Modula-2 sementics: RETURN( VAL(type,
   expr) ).  Only to be used for a constant expr, overflow checking
   is performed.  */

tree
m2convert_ConvertConstantAndCheck (location_t location, tree type, tree expr)
{
  tree etype;
  expr = fold (expr);
  STRIP_NOPS (expr);
  expr = m2expr_FoldAndStrip (expr);
  etype = TREE_TYPE (expr);

  m2assert_AssertLocation (location);
  if (etype == type)
    return expr;

  if (TREE_CODE (expr) == FUNCTION_DECL)
    expr = m2expr_BuildAddr (location, expr, false);

  type = m2tree_skip_type_decl (type);
  if (type == m2type_GetByteType () || type == m2type_GetISOLocType ()
      || type == m2type_GetISOByteType () || type == m2type_GetISOWordType ()
      || type == m2type_GetM2Word16 () || type == m2type_GetM2Word32 ()
      || type == m2type_GetM2Word64 ())
    return const_to_ISO_type (location, expr, type);

  return convert_and_check (location, type, m2expr_FoldAndStrip (expr));
}

/* ToWord - converts an expression (Integer or Ordinal type) into a
   WORD.  */

tree
m2convert_ToWord (location_t location, tree expr)
{
  return m2convert_BuildConvert (location, m2type_GetWordType (), expr, false);
}

/* ToCardinal - convert an expression, expr, to a CARDINAL.  */

tree
m2convert_ToCardinal (location_t location, tree expr)
{
  return m2convert_BuildConvert (location, m2type_GetCardinalType (), expr,
                                 false);
}

/* convertToPtr - if the type of tree, t, is not a ptr_type_node then
   convert it.  */

tree
m2convert_convertToPtr (location_t location, tree type)
{
  if (TREE_CODE (TREE_TYPE (type)) == POINTER_TYPE)
    return type;
  else
    return m2convert_BuildConvert (location, m2type_GetPointerType (), type,
                                   false);
}

/* ToInteger - convert an expression, expr, to an INTEGER.  */

tree
m2convert_ToInteger (location_t location, tree expr)
{
  return m2convert_BuildConvert (location, m2type_GetIntegerType (), expr,
                                 false);
}

/* ToBitset - convert an expression, expr, to a BITSET type.  */

tree
m2convert_ToBitset (location_t location, tree expr)
{
  return m2convert_BuildConvert (location, m2type_GetBitsetType (), expr,
                                 false);
}

/* ToLoc - convert an expression, expr, to a LOC.  */

tree
m2convert_ToLoc (location_t location, tree expr)
{
  return m2convert_BuildConvert (location, m2type_GetISOByteType (), expr,
                                 false);
}

/* GenericToType - converts, expr, into, type, providing that expr is
   a generic system type (byte, word etc).  Otherwise expr is
   returned unaltered.  */

tree
m2convert_GenericToType (location_t location, tree type, tree expr)
{
  tree etype = TREE_TYPE (expr);

  type = m2tree_skip_type_decl (type);
  if (type == etype)
    return expr;

  if (type == m2type_GetISOWordType () || type == m2type_GetM2Word16 ()
      || type == m2type_GetM2Word32 () || type == m2type_GetM2Word64 ())
    return const_to_ISO_type (location, expr, type);

  return expr;
}