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182 lines
4.7 KiB
182 lines
4.7 KiB
// 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) <[email protected]> |
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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/dfsqrt.c $Revision: 1.1 $ |
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* |
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* Purpose: |
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* Double Floating-point Square Root |
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* |
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* External Interfaces: |
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* dbl_fsqrt(srcptr,nullptr,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 "dbl_float.h" |
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/* |
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* Double Floating-point Square Root |
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*/ |
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/*ARGSUSED*/ |
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unsigned int |
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dbl_fsqrt( |
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dbl_floating_point *srcptr, |
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unsigned int *nullptr, |
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dbl_floating_point *dstptr, |
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unsigned int *status) |
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{ |
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register unsigned int srcp1, srcp2, resultp1, resultp2; |
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register unsigned int newbitp1, newbitp2, sump1, sump2; |
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register int src_exponent; |
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register boolean guardbit = FALSE, even_exponent; |
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Dbl_copyfromptr(srcptr,srcp1,srcp2); |
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/* |
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* check source operand for NaN or infinity |
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*/ |
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if ((src_exponent = Dbl_exponent(srcp1)) == DBL_INFINITY_EXPONENT) { |
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/* |
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* is signaling NaN? |
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*/ |
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if (Dbl_isone_signaling(srcp1)) { |
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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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Dbl_set_quiet(srcp1); |
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} |
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/* |
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* Return quiet NaN or positive infinity. |
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* Fall through to negative test if negative infinity. |
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*/ |
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if (Dbl_iszero_sign(srcp1) || |
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Dbl_isnotzero_mantissa(srcp1,srcp2)) { |
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Dbl_copytoptr(srcp1,srcp2,dstptr); |
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return(NOEXCEPTION); |
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} |
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} |
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/* |
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* check for zero source operand |
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*/ |
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if (Dbl_iszero_exponentmantissa(srcp1,srcp2)) { |
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Dbl_copytoptr(srcp1,srcp2,dstptr); |
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return(NOEXCEPTION); |
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} |
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/* |
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* check for negative source operand |
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*/ |
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if (Dbl_isone_sign(srcp1)) { |
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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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Dbl_makequietnan(srcp1,srcp2); |
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Dbl_copytoptr(srcp1,srcp2,dstptr); |
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return(NOEXCEPTION); |
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} |
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/* |
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* Generate result |
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*/ |
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if (src_exponent > 0) { |
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even_exponent = Dbl_hidden(srcp1); |
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Dbl_clear_signexponent_set_hidden(srcp1); |
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} |
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else { |
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/* normalize operand */ |
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Dbl_clear_signexponent(srcp1); |
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src_exponent++; |
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Dbl_normalize(srcp1,srcp2,src_exponent); |
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even_exponent = src_exponent & 1; |
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} |
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if (even_exponent) { |
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/* exponent is even */ |
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/* Add comment here. Explain why odd exponent needs correction */ |
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Dbl_leftshiftby1(srcp1,srcp2); |
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} |
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/* |
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* Add comment here. Explain following algorithm. |
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* |
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* Trust me, it works. |
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* |
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*/ |
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Dbl_setzero(resultp1,resultp2); |
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Dbl_allp1(newbitp1) = 1 << (DBL_P - 32); |
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Dbl_setzero_mantissap2(newbitp2); |
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while (Dbl_isnotzero(newbitp1,newbitp2) && Dbl_isnotzero(srcp1,srcp2)) { |
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Dbl_addition(resultp1,resultp2,newbitp1,newbitp2,sump1,sump2); |
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if(Dbl_isnotgreaterthan(sump1,sump2,srcp1,srcp2)) { |
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Dbl_leftshiftby1(newbitp1,newbitp2); |
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/* update result */ |
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Dbl_addition(resultp1,resultp2,newbitp1,newbitp2, |
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resultp1,resultp2); |
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Dbl_subtract(srcp1,srcp2,sump1,sump2,srcp1,srcp2); |
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Dbl_rightshiftby2(newbitp1,newbitp2); |
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} |
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else { |
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Dbl_rightshiftby1(newbitp1,newbitp2); |
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} |
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Dbl_leftshiftby1(srcp1,srcp2); |
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} |
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/* correct exponent for pre-shift */ |
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if (even_exponent) { |
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Dbl_rightshiftby1(resultp1,resultp2); |
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} |
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/* check for inexact */ |
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if (Dbl_isnotzero(srcp1,srcp2)) { |
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if (!even_exponent && Dbl_islessthan(resultp1,resultp2,srcp1,srcp2)) { |
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Dbl_increment(resultp1,resultp2); |
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} |
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guardbit = Dbl_lowmantissap2(resultp2); |
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Dbl_rightshiftby1(resultp1,resultp2); |
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/* now round result */ |
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switch (Rounding_mode()) { |
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case ROUNDPLUS: |
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Dbl_increment(resultp1,resultp2); |
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break; |
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case ROUNDNEAREST: |
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/* stickybit is always true, so guardbit |
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* is enough to determine rounding */ |
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if (guardbit) { |
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Dbl_increment(resultp1,resultp2); |
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} |
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break; |
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} |
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/* increment result exponent by 1 if mantissa overflowed */ |
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if (Dbl_isone_hiddenoverflow(resultp1)) src_exponent+=2; |
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if (Is_inexacttrap_enabled()) { |
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Dbl_set_exponent(resultp1, |
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((src_exponent-DBL_BIAS)>>1)+DBL_BIAS); |
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Dbl_copytoptr(resultp1,resultp2,dstptr); |
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return(INEXACTEXCEPTION); |
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} |
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else Set_inexactflag(); |
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} |
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else { |
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Dbl_rightshiftby1(resultp1,resultp2); |
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} |
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Dbl_set_exponent(resultp1,((src_exponent-DBL_BIAS)>>1)+DBL_BIAS); |
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Dbl_copytoptr(resultp1,resultp2,dstptr); |
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return(NOEXCEPTION); |
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}
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