Correct a function pre/postcondition [PR102403].

[thirdparty/gcc.git] / gcc / dfp.c

/* Decimal floating point support.
   Copyright (C) 2005-2021 Free Software Foundation, Inc.

This file is part of GCC.

GCC 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.

GCC 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 GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "tree.h"
#include "dfp.h"

/* The order of the following headers is important for making sure
   decNumber structure is large enough to hold decimal128 digits.  */

#include "decimal128.h"
#include "decimal64.h"
#include "decimal32.h"

#ifndef WORDS_BIGENDIAN
#define WORDS_BIGENDIAN 0
#endif

/* Initialize R (a real with the decimal flag set) from DN.  Can
   utilize status passed in via CONTEXT, if a previous operation had
   interesting status.  */

static void
decimal_from_decnumber (REAL_VALUE_TYPE *r, decNumber *dn, decContext *context)
{
  memset (r, 0, sizeof (REAL_VALUE_TYPE));

  r->cl = rvc_normal;
  if (decNumberIsNaN (dn))
    r->cl = rvc_nan;
  if (decNumberIsInfinite (dn))
    r->cl = rvc_inf;
  if (context->status & DEC_Overflow)
    r->cl = rvc_inf;
  if (decNumberIsNegative (dn))
    r->sign = 1;
  r->decimal = 1;

  if (r->cl != rvc_normal)
    return;

  decContextDefault (context, DEC_INIT_DECIMAL128);
  context->traps = 0;

  decimal128FromNumber ((decimal128 *) r->sig, dn, context);
}

/* Create decimal encoded R from string S.  */

void
decimal_real_from_string (REAL_VALUE_TYPE *r, const char *s)
{
  decNumber dn;
  decContext set;
  decContextDefault (&set, DEC_INIT_DECIMAL128);
  set.traps = 0;

  decNumberFromString (&dn, s, &set);

  /* It would be more efficient to store directly in decNumber format,
     but that is impractical from current data structure size.
     Encoding as a decimal128 is much more compact.  */
  decimal_from_decnumber (r, &dn, &set);
}

/* Initialize a decNumber from a REAL_VALUE_TYPE.  */

static void
decimal_to_decnumber (const REAL_VALUE_TYPE *r, decNumber *dn)
{
  decContext set;
  decContextDefault (&set, DEC_INIT_DECIMAL128);
  set.traps = 0;

  switch (r->cl)
    {
    case rvc_zero:
      decNumberZero (dn);
      break;
    case rvc_inf:
      decNumberFromString (dn, "Infinity", &set);
      break;
    case rvc_nan:
      if (r->signalling)
        decNumberFromString (dn, "snan", &set);
      else
        decNumberFromString (dn, "nan", &set);
      break;
    case rvc_normal:
      if (!r->decimal)
	{
	  /* dconst{1,2,m1,half} are used in various places in
	     the middle-end and optimizers, allow them here
	     as an exception by converting them to decimal.  */
	  if (memcmp (r, &dconst1, sizeof (*r)) == 0)
	    {
	      decNumberFromString (dn, "1", &set);
	      break;
	    }
	  if (memcmp (r, &dconst2, sizeof (*r)) == 0)
	    {
	      decNumberFromString (dn, "2", &set);
	      break;
	    }
	  if (memcmp (r, &dconstm1, sizeof (*r)) == 0)
	    {
	      decNumberFromString (dn, "-1", &set);
	      break;
	    }
	  if (memcmp (r, &dconsthalf, sizeof (*r)) == 0)
	    {
	      decNumberFromString (dn, "0.5", &set);
	      break;
	    }
	  gcc_unreachable ();
	}
      decimal128ToNumber ((const decimal128 *) r->sig, dn);
      break;
    default:
      gcc_unreachable ();
    }

  /* Fix up sign bit.  */
  if (r->sign != decNumberIsNegative (dn))
    dn->bits ^= DECNEG;
}

/* Encode a real into an IEEE 754 decimal32 type.  */

void
encode_decimal32 (const struct real_format *fmt ATTRIBUTE_UNUSED,
		  long *buf, const REAL_VALUE_TYPE *r)
{
  decNumber dn;
  decimal32 d32;
  decContext set;
  int32_t image;

  decContextDefault (&set, DEC_INIT_DECIMAL128);
  set.traps = 0;

  decimal_to_decnumber (r, &dn);
  decimal32FromNumber (&d32, &dn, &set);

  memcpy (&image, d32.bytes, sizeof (int32_t));
  buf[0] = image;
}

/* Decode an IEEE 754 decimal32 type into a real.  */

void
decode_decimal32 (const struct real_format *fmt ATTRIBUTE_UNUSED,
		  REAL_VALUE_TYPE *r, const long *buf)
{
  decNumber dn;
  decimal32 d32;
  decContext set;
  int32_t image;

  decContextDefault (&set, DEC_INIT_DECIMAL128);
  set.traps = 0;

  image = buf[0];
  memcpy (&d32.bytes, &image, sizeof (int32_t));

  decimal32ToNumber (&d32, &dn);
  decimal_from_decnumber (r, &dn, &set);
}

/* Encode a real into an IEEE 754 decimal64 type.  */

void
encode_decimal64 (const struct real_format *fmt ATTRIBUTE_UNUSED,
		  long *buf, const REAL_VALUE_TYPE *r)
{
  decNumber dn;
  decimal64 d64;
  decContext set;
  int32_t image;

  decContextDefault (&set, DEC_INIT_DECIMAL128);
  set.traps = 0;

  decimal_to_decnumber (r, &dn);
  decimal64FromNumber (&d64, &dn, &set);

  if (WORDS_BIGENDIAN == FLOAT_WORDS_BIG_ENDIAN)
    {
      memcpy (&image, &d64.bytes[0], sizeof (int32_t));
      buf[0] = image;
      memcpy (&image, &d64.bytes[4], sizeof (int32_t));
      buf[1] = image;
    }
  else
    {
      memcpy (&image, &d64.bytes[4], sizeof (int32_t));
      buf[0] = image;
      memcpy (&image, &d64.bytes[0], sizeof (int32_t));
      buf[1] = image;
    }
}

/* Decode an IEEE 754 decimal64 type into a real.  */

void
decode_decimal64 (const struct real_format *fmt ATTRIBUTE_UNUSED,
		  REAL_VALUE_TYPE *r, const long *buf)
{
  decNumber dn;
  decimal64 d64;
  decContext set;
  int32_t image;

  decContextDefault (&set, DEC_INIT_DECIMAL128);
  set.traps = 0;

  if (WORDS_BIGENDIAN == FLOAT_WORDS_BIG_ENDIAN)
    {
      image = buf[0];
      memcpy (&d64.bytes[0], &image, sizeof (int32_t));
      image = buf[1];
      memcpy (&d64.bytes[4], &image, sizeof (int32_t));
    }
  else
    {
      image = buf[1];
      memcpy (&d64.bytes[0], &image, sizeof (int32_t));
      image = buf[0];
      memcpy (&d64.bytes[4], &image, sizeof (int32_t));
    }

  decimal64ToNumber (&d64, &dn);
  decimal_from_decnumber (r, &dn, &set);
}

/* Encode a real into an IEEE 754 decimal128 type.  */

void
encode_decimal128 (const struct real_format *fmt ATTRIBUTE_UNUSED,
		   long *buf, const REAL_VALUE_TYPE *r)
{
  decNumber dn;
  decContext set;
  decimal128 d128;
  int32_t image;

  decContextDefault (&set, DEC_INIT_DECIMAL128);
  set.traps = 0;

  decimal_to_decnumber (r, &dn);
  decimal128FromNumber (&d128, &dn, &set);

  if (WORDS_BIGENDIAN == FLOAT_WORDS_BIG_ENDIAN)
    {
      memcpy (&image, &d128.bytes[0], sizeof (int32_t));
      buf[0] = image;
      memcpy (&image, &d128.bytes[4], sizeof (int32_t));
      buf[1] = image;
      memcpy (&image, &d128.bytes[8], sizeof (int32_t));
      buf[2] = image;
      memcpy (&image, &d128.bytes[12], sizeof (int32_t));
      buf[3] = image;
    }
  else
    {
      memcpy (&image, &d128.bytes[12], sizeof (int32_t));
      buf[0] = image;
      memcpy (&image, &d128.bytes[8], sizeof (int32_t));
      buf[1] = image;
      memcpy (&image, &d128.bytes[4], sizeof (int32_t));
      buf[2] = image;
      memcpy (&image, &d128.bytes[0], sizeof (int32_t));
      buf[3] = image;
    }
}

/* Decode an IEEE 754 decimal128 type into a real.  */

void
decode_decimal128 (const struct real_format *fmt ATTRIBUTE_UNUSED,
		   REAL_VALUE_TYPE *r, const long *buf)
{
  decNumber dn;
  decimal128 d128;
  decContext set;
  int32_t image;

  decContextDefault (&set, DEC_INIT_DECIMAL128);
  set.traps = 0;

  if (WORDS_BIGENDIAN == FLOAT_WORDS_BIG_ENDIAN)
    {
      image = buf[0];
      memcpy (&d128.bytes[0],  &image, sizeof (int32_t));
      image = buf[1];
      memcpy (&d128.bytes[4],  &image, sizeof (int32_t));
      image = buf[2];
      memcpy (&d128.bytes[8],  &image, sizeof (int32_t));
      image = buf[3];
      memcpy (&d128.bytes[12], &image, sizeof (int32_t));
    }
  else
    {
      image = buf[3];
      memcpy (&d128.bytes[0],  &image, sizeof (int32_t));
      image = buf[2];
      memcpy (&d128.bytes[4],  &image, sizeof (int32_t));
      image = buf[1];
      memcpy (&d128.bytes[8],  &image, sizeof (int32_t));
      image = buf[0];
      memcpy (&d128.bytes[12], &image, sizeof (int32_t));
    }

  decimal128ToNumber (&d128, &dn);
  decimal_from_decnumber (r, &dn, &set);
}

/* Helper function to convert from a binary real internal
   representation.  */

static void
decimal_to_binary (REAL_VALUE_TYPE *to, const REAL_VALUE_TYPE *from,
		   const real_format *fmt)
{
  char string[256];
  if (from->cl == rvc_normal)
    {
      const decimal128 *const d128 = (const decimal128 *) from->sig;
      decimal128ToString (d128, string);
    }
  else
    real_to_decimal (string, from, sizeof (string), 0, 1);
  real_from_string3 (to, string, fmt);
}


/* Helper function to convert from a binary real internal
   representation.  */

static void
decimal_from_binary (REAL_VALUE_TYPE *to, const REAL_VALUE_TYPE *from)
{
  char string[256];

  /* We convert to string, then to decNumber then to decimal128.  */
  real_to_decimal (string, from, sizeof (string), 0, 1);
  decimal_real_from_string (to, string);
}

/* Helper function to real.c:do_compare() to handle decimal internal
   representation including when one of the operands is still in the
   binary internal representation.  */

int
decimal_do_compare (const REAL_VALUE_TYPE *a, const REAL_VALUE_TYPE *b,
		    int nan_result)
{
  decContext set;
  decNumber dn, dn2, dn3;
  REAL_VALUE_TYPE a1, b1;

  /* If either operand is non-decimal, create temporary versions.  */
  if (!a->decimal)
    {
      decimal_from_binary (&a1, a);
      a = &a1;
    }
  if (!b->decimal)
    {
      decimal_from_binary (&b1, b);
      b = &b1;
    }

  /* Convert into decNumber form for comparison operation.  */
  decContextDefault (&set, DEC_INIT_DECIMAL128);
  set.traps = 0;
  decimal128ToNumber ((const decimal128 *) a->sig, &dn2);
  decimal128ToNumber ((const decimal128 *) b->sig, &dn3);

  /* Finally, do the comparison.  */
  decNumberCompare (&dn, &dn2, &dn3, &set);

  /* Return the comparison result.  */
  if (decNumberIsNaN (&dn))
    return nan_result;
  else if (decNumberIsZero (&dn))
    return 0;
  else if (decNumberIsNegative (&dn))
    return -1;
  else
    return 1;
}

/* Helper to round_for_format, handling decimal float types.  */

void
decimal_round_for_format (const struct real_format *fmt, REAL_VALUE_TYPE *r)
{
  decNumber dn;
  decContext set;

  /* Real encoding occurs later.  */
  if (r->cl != rvc_normal)
    return;

  decContextDefault (&set, DEC_INIT_DECIMAL128);
  set.traps = 0;
  decimal128ToNumber ((decimal128 *) r->sig, &dn);

  if (fmt == &decimal_quad_format)
    {
      /* The internal format is already in this format.  */
      return;
    }
  else if (fmt == &decimal_single_format)
    {
      decimal32 d32;
      decContextDefault (&set, DEC_INIT_DECIMAL32);
      set.traps = 0;

      decimal32FromNumber (&d32, &dn, &set);
      decimal32ToNumber (&d32, &dn);
    }
  else if (fmt == &decimal_double_format)
    {
      decimal64 d64;
      decContextDefault (&set, DEC_INIT_DECIMAL64);
      set.traps = 0;

      decimal64FromNumber (&d64, &dn, &set);
      decimal64ToNumber (&d64, &dn);
    }
  else
    gcc_unreachable ();

  decimal_from_decnumber (r, &dn, &set);
}

/* Extend or truncate to a new mode.  Handles conversions between
   binary and decimal types.  */

void
decimal_real_convert (REAL_VALUE_TYPE *r, const real_format *fmt,
		      const REAL_VALUE_TYPE *a)
{
  if (a->decimal && fmt->b == 10)
    return;
  if (a->decimal)
      decimal_to_binary (r, a, fmt);
  else
      decimal_from_binary (r, a);
}

/* Render R_ORIG as a decimal floating point constant.  Emit DIGITS
   significant digits in the result, bounded by BUF_SIZE.  If DIGITS
   is 0, choose the maximum for the representation.  If
   CROP_TRAILING_ZEROS, strip trailing zeros.  Currently, not honoring
   DIGITS or CROP_TRAILING_ZEROS.  */

void
decimal_real_to_decimal (char *str, const REAL_VALUE_TYPE *r_orig,
			 size_t buf_size,
			 size_t digits ATTRIBUTE_UNUSED,
			 int crop_trailing_zeros ATTRIBUTE_UNUSED)
{
  const decimal128 *const d128 = (const decimal128*) r_orig->sig;

  /* decimal128ToString requires space for at least 24 characters;
     Require two more for suffix.  */
  gcc_assert (buf_size >= 24);
  decimal128ToString (d128, str);
}

static bool
decimal_do_add (REAL_VALUE_TYPE *r, const REAL_VALUE_TYPE *op0,
		const REAL_VALUE_TYPE *op1, int subtract_p)
{
  decNumber dn;
  decContext set;
  decNumber dn2, dn3;

  decimal_to_decnumber (op0, &dn2);
  decimal_to_decnumber (op1, &dn3);

  decContextDefault (&set, DEC_INIT_DECIMAL128);
  set.traps = 0;

  if (subtract_p)
    decNumberSubtract (&dn, &dn2, &dn3, &set);
  else
    decNumberAdd (&dn, &dn2, &dn3, &set);

  decimal_from_decnumber (r, &dn, &set);

  /* Return true, if inexact.  */
  return (set.status & DEC_Inexact);
}

/* Compute R = OP0 * OP1.  */

static bool
decimal_do_multiply (REAL_VALUE_TYPE *r, const REAL_VALUE_TYPE *op0,
		     const REAL_VALUE_TYPE *op1)
{
  decContext set;
  decNumber dn, dn2, dn3;

  decimal_to_decnumber (op0, &dn2);
  decimal_to_decnumber (op1, &dn3);

  decContextDefault (&set, DEC_INIT_DECIMAL128);
  set.traps = 0;

  decNumberMultiply (&dn, &dn2, &dn3, &set);
  decimal_from_decnumber (r, &dn, &set);

  /* Return true, if inexact.  */
  return (set.status & DEC_Inexact);
}

/* Compute R = OP0 / OP1.  */

static bool
decimal_do_divide (REAL_VALUE_TYPE *r, const REAL_VALUE_TYPE *op0,
		   const REAL_VALUE_TYPE *op1)
{
  decContext set;
  decNumber dn, dn2, dn3;

  decimal_to_decnumber (op0, &dn2);
  decimal_to_decnumber (op1, &dn3);

  decContextDefault (&set, DEC_INIT_DECIMAL128);
  set.traps = 0;

  decNumberDivide (&dn, &dn2, &dn3, &set);
  decimal_from_decnumber (r, &dn, &set);

  /* Return true, if inexact.  */
  return (set.status & DEC_Inexact);
}

/* Set R to A truncated to an integral value toward zero (decimal
   floating point).  */

void
decimal_do_fix_trunc (REAL_VALUE_TYPE *r, const REAL_VALUE_TYPE *a)
{
  decNumber dn, dn2;
  decContext set;

  decContextDefault (&set, DEC_INIT_DECIMAL128);
  set.traps = 0;
  set.round = DEC_ROUND_DOWN;
  decimal128ToNumber ((const decimal128 *) a->sig, &dn2);

  decNumberToIntegralValue (&dn, &dn2, &set);
  decimal_from_decnumber (r, &dn, &set);
}

/* Render decimal float value R as an integer.  */

HOST_WIDE_INT
decimal_real_to_integer (const REAL_VALUE_TYPE *r)
{
  decContext set;
  decNumber dn, dn2, dn3;
  REAL_VALUE_TYPE to;
  char string[256];

  decContextDefault (&set, DEC_INIT_DECIMAL128);
  set.traps = 0;
  set.round = DEC_ROUND_DOWN;
  decimal128ToNumber ((const decimal128 *) r->sig, &dn);

  decNumberToIntegralValue (&dn2, &dn, &set);
  decNumberZero (&dn3);
  decNumberRescale (&dn, &dn2, &dn3, &set);

  /* Convert to REAL_VALUE_TYPE and call appropriate conversion
     function.  */
  decNumberToString (&dn, string);
  real_from_string (&to, string);
  return real_to_integer (&to);
}

/* Likewise, but returns a wide_int with PRECISION.  *FAIL is set if the
   value does not fit.  */

wide_int
decimal_real_to_integer (const REAL_VALUE_TYPE *r, bool *fail, int precision)
{
  decContext set;
  decNumber dn, dn2, dn3;
  REAL_VALUE_TYPE to;
  char string[256];

  decContextDefault (&set, DEC_INIT_DECIMAL128);
  set.traps = 0;
  set.round = DEC_ROUND_DOWN;
  decimal128ToNumber ((const decimal128 *) r->sig, &dn);

  decNumberToIntegralValue (&dn2, &dn, &set);
  decNumberZero (&dn3);
  decNumberRescale (&dn, &dn2, &dn3, &set);

  /* Convert to REAL_VALUE_TYPE and call appropriate conversion
     function.  */
  decNumberToString (&dn, string);
  real_from_string (&to, string);
  return real_to_integer (&to, fail, precision);
}

/* Perform the decimal floating point operation described by CODE.
   For a unary operation, OP1 will be NULL.  This function returns
   true if the result may be inexact due to loss of precision.  */

bool
decimal_real_arithmetic (REAL_VALUE_TYPE *r, enum tree_code code,
			 const REAL_VALUE_TYPE *op0,
			 const REAL_VALUE_TYPE *op1)
{
  REAL_VALUE_TYPE a, b;

  /* If either operand is non-decimal, create temporaries.  */
  if (!op0->decimal)
    {
      decimal_from_binary (&a, op0);
      op0 = &a;
    }
  if (op1 && !op1->decimal)
    {
      decimal_from_binary (&b, op1);
      op1 = &b;
    }

  switch (code)
    {
    case PLUS_EXPR:
      return decimal_do_add (r, op0, op1, 0);

    case MINUS_EXPR:
      return decimal_do_add (r, op0, op1, 1);

    case MULT_EXPR:
      return decimal_do_multiply (r, op0, op1);

    case RDIV_EXPR:
      return decimal_do_divide (r, op0, op1);

    case MIN_EXPR:
      if (op1->cl == rvc_nan)
        *r = *op1;
      else if (real_compare (UNLT_EXPR, op0, op1))
        *r = *op0;
      else
        *r = *op1;
      return false;

    case MAX_EXPR:
      if (op1->cl == rvc_nan)
        *r = *op1;
      else if (real_compare (LT_EXPR, op0, op1))
        *r = *op1;
      else
        *r = *op0;
      return false;

    case NEGATE_EXPR:
      {
	*r = *op0;
	/* Flip sign bit.  */
	decimal128FlipSign ((decimal128 *) r->sig);
	/* Keep sign field in sync.  */
	r->sign ^= 1;
      }
      return false;

    case ABS_EXPR:
      {
        *r = *op0;
	/* Clear sign bit.  */
	decimal128ClearSign ((decimal128 *) r->sig);
	/* Keep sign field in sync.  */
	r->sign = 0;
      }
      return false;

    case FIX_TRUNC_EXPR:
      decimal_do_fix_trunc (r, op0);
      return false;

    default:
      gcc_unreachable ();
    }
}

/* Fills R with the largest finite value representable in mode MODE.
   If SIGN is nonzero, R is set to the most negative finite value.  */

void
decimal_real_maxval (REAL_VALUE_TYPE *r, int sign, machine_mode mode)
{
  const char *max;

  switch (mode)
    {
    case E_SDmode:
      max = "9.999999E96";
      break;
    case E_DDmode:
      max = "9.999999999999999E384";
      break;
    case E_TDmode:
      max = "9.999999999999999999999999999999999E6144";
      break;
    default:
      gcc_unreachable ();
    }

  decimal_real_from_string (r, max);
  if (sign)
    decimal128SetSign ((decimal128 *) r->sig, 1);

  r->sign = sign;
}