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Based on 1 normalized pattern(s): 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 2 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 write to the free software foundation inc 59 temple place suite 330 boston ma 02111 1307 usa extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 42 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Richard Fontana <rfontana@redhat.com> Reviewed-by: Allison Randal <allison@lohutok.net> Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190524100845.259718220@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
509 lines
14 KiB
C
509 lines
14 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Linux/PA-RISC Project (http://www.parisc-linux.org/)
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*
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* Floating-point emulation code
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* Copyright (C) 2001 Hewlett-Packard (Paul Bame) <bame@debian.org>
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*/
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/*
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* BEGIN_DESC
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*
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* File:
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* @(#) pa/spmath/sfsub.c $Revision: 1.1 $
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*
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* Purpose:
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* Single_subtract: subtract two single precision values.
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*
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* External Interfaces:
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* sgl_fsub(leftptr, rightptr, dstptr, status)
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*
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* Internal Interfaces:
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*
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* Theory:
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* <<please update with a overview of the operation of this file>>
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*
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* END_DESC
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*/
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#include "float.h"
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#include "sgl_float.h"
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/*
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* Single_subtract: subtract two single precision values.
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*/
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int
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sgl_fsub(
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sgl_floating_point *leftptr,
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sgl_floating_point *rightptr,
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sgl_floating_point *dstptr,
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unsigned int *status)
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{
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register unsigned int left, right, result, extent;
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register unsigned int signless_upper_left, signless_upper_right, save;
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register int result_exponent, right_exponent, diff_exponent;
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register int sign_save, jumpsize;
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register boolean inexact = FALSE, underflowtrap;
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/* Create local copies of the numbers */
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left = *leftptr;
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right = *rightptr;
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/* A zero "save" helps discover equal operands (for later), *
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* and is used in swapping operands (if needed). */
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Sgl_xortointp1(left,right,/*to*/save);
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/*
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* check first operand for NaN's or infinity
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*/
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if ((result_exponent = Sgl_exponent(left)) == SGL_INFINITY_EXPONENT)
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{
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if (Sgl_iszero_mantissa(left))
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{
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if (Sgl_isnotnan(right))
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{
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if (Sgl_isinfinity(right) && save==0)
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{
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/*
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* invalid since operands are same signed infinity's
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*/
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if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
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Set_invalidflag();
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Sgl_makequietnan(result);
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*dstptr = result;
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return(NOEXCEPTION);
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}
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/*
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* return infinity
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*/
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*dstptr = left;
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return(NOEXCEPTION);
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}
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}
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else
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{
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/*
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* is NaN; signaling or quiet?
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*/
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if (Sgl_isone_signaling(left))
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{
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/* trap if INVALIDTRAP enabled */
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if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
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/* make NaN quiet */
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Set_invalidflag();
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Sgl_set_quiet(left);
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}
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/*
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* is second operand a signaling NaN?
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*/
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else if (Sgl_is_signalingnan(right))
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{
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/* trap if INVALIDTRAP enabled */
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if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
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/* make NaN quiet */
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Set_invalidflag();
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Sgl_set_quiet(right);
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*dstptr = right;
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return(NOEXCEPTION);
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}
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/*
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* return quiet NaN
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*/
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*dstptr = left;
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return(NOEXCEPTION);
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}
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} /* End left NaN or Infinity processing */
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/*
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* check second operand for NaN's or infinity
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*/
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if (Sgl_isinfinity_exponent(right))
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{
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if (Sgl_iszero_mantissa(right))
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{
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/* return infinity */
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Sgl_invert_sign(right);
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*dstptr = right;
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return(NOEXCEPTION);
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}
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/*
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* is NaN; signaling or quiet?
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*/
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if (Sgl_isone_signaling(right))
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{
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/* trap if INVALIDTRAP enabled */
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if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
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/* make NaN quiet */
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Set_invalidflag();
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Sgl_set_quiet(right);
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}
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/*
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* return quiet NaN
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*/
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*dstptr = right;
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return(NOEXCEPTION);
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} /* End right NaN or Infinity processing */
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/* Invariant: Must be dealing with finite numbers */
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/* Compare operands by removing the sign */
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Sgl_copytoint_exponentmantissa(left,signless_upper_left);
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Sgl_copytoint_exponentmantissa(right,signless_upper_right);
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/* sign difference selects sub or add operation. */
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if(Sgl_ismagnitudeless(signless_upper_left,signless_upper_right))
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{
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/* Set the left operand to the larger one by XOR swap *
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* First finish the first word using "save" */
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Sgl_xorfromintp1(save,right,/*to*/right);
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Sgl_xorfromintp1(save,left,/*to*/left);
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result_exponent = Sgl_exponent(left);
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Sgl_invert_sign(left);
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}
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/* Invariant: left is not smaller than right. */
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if((right_exponent = Sgl_exponent(right)) == 0)
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{
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/* Denormalized operands. First look for zeroes */
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if(Sgl_iszero_mantissa(right))
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{
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/* right is zero */
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if(Sgl_iszero_exponentmantissa(left))
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{
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/* Both operands are zeros */
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Sgl_invert_sign(right);
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if(Is_rounding_mode(ROUNDMINUS))
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{
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Sgl_or_signs(left,/*with*/right);
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}
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else
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{
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Sgl_and_signs(left,/*with*/right);
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}
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}
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else
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{
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/* Left is not a zero and must be the result. Trapped
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* underflows are signaled if left is denormalized. Result
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* is always exact. */
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if( (result_exponent == 0) && Is_underflowtrap_enabled() )
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{
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/* need to normalize results mantissa */
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sign_save = Sgl_signextendedsign(left);
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Sgl_leftshiftby1(left);
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Sgl_normalize(left,result_exponent);
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Sgl_set_sign(left,/*using*/sign_save);
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Sgl_setwrapped_exponent(left,result_exponent,unfl);
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*dstptr = left;
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/* inexact = FALSE */
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return(UNDERFLOWEXCEPTION);
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}
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}
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*dstptr = left;
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return(NOEXCEPTION);
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}
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/* Neither are zeroes */
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Sgl_clear_sign(right); /* Exponent is already cleared */
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if(result_exponent == 0 )
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{
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/* Both operands are denormalized. The result must be exact
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* and is simply calculated. A sum could become normalized and a
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* difference could cancel to a true zero. */
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if( (/*signed*/int) save >= 0 )
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{
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Sgl_subtract(left,/*minus*/right,/*into*/result);
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if(Sgl_iszero_mantissa(result))
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{
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if(Is_rounding_mode(ROUNDMINUS))
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{
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Sgl_setone_sign(result);
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}
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else
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{
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Sgl_setzero_sign(result);
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}
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*dstptr = result;
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return(NOEXCEPTION);
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}
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}
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else
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{
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Sgl_addition(left,right,/*into*/result);
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if(Sgl_isone_hidden(result))
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{
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*dstptr = result;
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return(NOEXCEPTION);
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}
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}
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if(Is_underflowtrap_enabled())
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{
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/* need to normalize result */
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sign_save = Sgl_signextendedsign(result);
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Sgl_leftshiftby1(result);
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Sgl_normalize(result,result_exponent);
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Sgl_set_sign(result,/*using*/sign_save);
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Sgl_setwrapped_exponent(result,result_exponent,unfl);
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*dstptr = result;
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/* inexact = FALSE */
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return(UNDERFLOWEXCEPTION);
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}
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*dstptr = result;
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return(NOEXCEPTION);
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}
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right_exponent = 1; /* Set exponent to reflect different bias
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* with denomalized numbers. */
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}
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else
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{
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Sgl_clear_signexponent_set_hidden(right);
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}
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Sgl_clear_exponent_set_hidden(left);
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diff_exponent = result_exponent - right_exponent;
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/*
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* Special case alignment of operands that would force alignment
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* beyond the extent of the extension. A further optimization
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* could special case this but only reduces the path length for this
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* infrequent case.
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*/
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if(diff_exponent > SGL_THRESHOLD)
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{
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diff_exponent = SGL_THRESHOLD;
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}
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/* Align right operand by shifting to right */
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Sgl_right_align(/*operand*/right,/*shifted by*/diff_exponent,
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/*and lower to*/extent);
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/* Treat sum and difference of the operands separately. */
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if( (/*signed*/int) save >= 0 )
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{
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/*
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* Difference of the two operands. Their can be no overflow. A
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* borrow can occur out of the hidden bit and force a post
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* normalization phase.
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*/
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Sgl_subtract_withextension(left,/*minus*/right,/*with*/extent,/*into*/result);
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if(Sgl_iszero_hidden(result))
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{
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/* Handle normalization */
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/* A straightforward algorithm would now shift the result
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* and extension left until the hidden bit becomes one. Not
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* all of the extension bits need participate in the shift.
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* Only the two most significant bits (round and guard) are
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* needed. If only a single shift is needed then the guard
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* bit becomes a significant low order bit and the extension
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* must participate in the rounding. If more than a single
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* shift is needed, then all bits to the right of the guard
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* bit are zeros, and the guard bit may or may not be zero. */
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sign_save = Sgl_signextendedsign(result);
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Sgl_leftshiftby1_withextent(result,extent,result);
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/* Need to check for a zero result. The sign and exponent
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* fields have already been zeroed. The more efficient test
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* of the full object can be used.
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*/
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if(Sgl_iszero(result))
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/* Must have been "x-x" or "x+(-x)". */
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{
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if(Is_rounding_mode(ROUNDMINUS)) Sgl_setone_sign(result);
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*dstptr = result;
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return(NOEXCEPTION);
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}
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result_exponent--;
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/* Look to see if normalization is finished. */
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if(Sgl_isone_hidden(result))
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{
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if(result_exponent==0)
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{
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/* Denormalized, exponent should be zero. Left operand *
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* was normalized, so extent (guard, round) was zero */
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goto underflow;
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}
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else
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{
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/* No further normalization is needed. */
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Sgl_set_sign(result,/*using*/sign_save);
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Ext_leftshiftby1(extent);
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goto round;
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}
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}
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/* Check for denormalized, exponent should be zero. Left *
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* operand was normalized, so extent (guard, round) was zero */
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if(!(underflowtrap = Is_underflowtrap_enabled()) &&
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result_exponent==0) goto underflow;
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/* Shift extension to complete one bit of normalization and
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* update exponent. */
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Ext_leftshiftby1(extent);
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/* Discover first one bit to determine shift amount. Use a
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* modified binary search. We have already shifted the result
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* one position right and still not found a one so the remainder
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* of the extension must be zero and simplifies rounding. */
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/* Scan bytes */
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while(Sgl_iszero_hiddenhigh7mantissa(result))
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{
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Sgl_leftshiftby8(result);
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if((result_exponent -= 8) <= 0 && !underflowtrap)
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goto underflow;
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}
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/* Now narrow it down to the nibble */
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if(Sgl_iszero_hiddenhigh3mantissa(result))
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{
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/* The lower nibble contains the normalizing one */
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Sgl_leftshiftby4(result);
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if((result_exponent -= 4) <= 0 && !underflowtrap)
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goto underflow;
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}
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/* Select case were first bit is set (already normalized)
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* otherwise select the proper shift. */
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if((jumpsize = Sgl_hiddenhigh3mantissa(result)) > 7)
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{
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/* Already normalized */
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if(result_exponent <= 0) goto underflow;
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Sgl_set_sign(result,/*using*/sign_save);
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Sgl_set_exponent(result,/*using*/result_exponent);
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*dstptr = result;
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return(NOEXCEPTION);
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}
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Sgl_sethigh4bits(result,/*using*/sign_save);
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switch(jumpsize)
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{
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case 1:
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{
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Sgl_leftshiftby3(result);
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result_exponent -= 3;
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break;
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}
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case 2:
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case 3:
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{
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Sgl_leftshiftby2(result);
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result_exponent -= 2;
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break;
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}
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case 4:
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case 5:
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case 6:
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case 7:
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{
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Sgl_leftshiftby1(result);
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result_exponent -= 1;
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break;
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}
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}
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if(result_exponent > 0)
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{
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Sgl_set_exponent(result,/*using*/result_exponent);
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*dstptr = result; /* Sign bit is already set */
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return(NOEXCEPTION);
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}
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/* Fixup potential underflows */
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underflow:
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if(Is_underflowtrap_enabled())
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{
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Sgl_set_sign(result,sign_save);
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Sgl_setwrapped_exponent(result,result_exponent,unfl);
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*dstptr = result;
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/* inexact = FALSE */
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return(UNDERFLOWEXCEPTION);
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}
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/*
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* Since we cannot get an inexact denormalized result,
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* we can now return.
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*/
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Sgl_right_align(result,/*by*/(1-result_exponent),extent);
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Sgl_clear_signexponent(result);
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Sgl_set_sign(result,sign_save);
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*dstptr = result;
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return(NOEXCEPTION);
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} /* end if(hidden...)... */
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/* Fall through and round */
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} /* end if(save >= 0)... */
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else
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{
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/* Add magnitudes */
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Sgl_addition(left,right,/*to*/result);
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if(Sgl_isone_hiddenoverflow(result))
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{
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/* Prenormalization required. */
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Sgl_rightshiftby1_withextent(result,extent,extent);
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Sgl_arithrightshiftby1(result);
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result_exponent++;
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} /* end if hiddenoverflow... */
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} /* end else ...sub magnitudes... */
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/* Round the result. If the extension is all zeros,then the result is
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* exact. Otherwise round in the correct direction. No underflow is
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* possible. If a postnormalization is necessary, then the mantissa is
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* all zeros so no shift is needed. */
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round:
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if(Ext_isnotzero(extent))
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{
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inexact = TRUE;
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switch(Rounding_mode())
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{
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case ROUNDNEAREST: /* The default. */
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if(Ext_isone_sign(extent))
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{
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/* at least 1/2 ulp */
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if(Ext_isnotzero_lower(extent) ||
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Sgl_isone_lowmantissa(result))
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{
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/* either exactly half way and odd or more than 1/2ulp */
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Sgl_increment(result);
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}
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}
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break;
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case ROUNDPLUS:
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if(Sgl_iszero_sign(result))
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{
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/* Round up positive results */
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Sgl_increment(result);
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}
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break;
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case ROUNDMINUS:
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if(Sgl_isone_sign(result))
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{
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/* Round down negative results */
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Sgl_increment(result);
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}
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case ROUNDZERO:;
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/* truncate is simple */
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} /* end switch... */
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if(Sgl_isone_hiddenoverflow(result)) result_exponent++;
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}
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if(result_exponent == SGL_INFINITY_EXPONENT)
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{
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/* Overflow */
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if(Is_overflowtrap_enabled())
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{
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Sgl_setwrapped_exponent(result,result_exponent,ovfl);
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*dstptr = result;
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if (inexact)
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if (Is_inexacttrap_enabled())
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return(OVERFLOWEXCEPTION | INEXACTEXCEPTION);
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else Set_inexactflag();
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return(OVERFLOWEXCEPTION);
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}
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else
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{
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Set_overflowflag();
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inexact = TRUE;
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Sgl_setoverflow(result);
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}
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}
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else Sgl_set_exponent(result,result_exponent);
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*dstptr = result;
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if(inexact)
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if(Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
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else Set_inexactflag();
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return(NOEXCEPTION);
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}
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