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