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Diffstat (limited to 'arch/parisc/math-emu/dfsqrt.c')
| -rw-r--r-- | arch/parisc/math-emu/dfsqrt.c | 182 |
1 files changed, 182 insertions, 0 deletions
diff --git a/arch/parisc/math-emu/dfsqrt.c b/arch/parisc/math-emu/dfsqrt.c new file mode 100644 index 000000000..63d339c81 --- /dev/null +++ b/arch/parisc/math-emu/dfsqrt.c @@ -0,0 +1,182 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Linux/PA-RISC Project (http://www.parisc-linux.org/) + * + * Floating-point emulation code + * Copyright (C) 2001 Hewlett-Packard (Paul Bame) <bame@debian.org> + */ +/* + * BEGIN_DESC + * + * File: + * @(#) pa/spmath/dfsqrt.c $Revision: 1.1 $ + * + * Purpose: + * Double Floating-point Square Root + * + * External Interfaces: + * dbl_fsqrt(srcptr,nullptr,dstptr,status) + * + * Internal Interfaces: + * + * Theory: + * <<please update with a overview of the operation of this file>> + * + * END_DESC +*/ + + +#include "float.h" +#include "dbl_float.h" + +/* + * Double Floating-point Square Root + */ + +/*ARGSUSED*/ +unsigned int +dbl_fsqrt( + dbl_floating_point *srcptr, + unsigned int *nullptr, + dbl_floating_point *dstptr, + unsigned int *status) +{ + register unsigned int srcp1, srcp2, resultp1, resultp2; + register unsigned int newbitp1, newbitp2, sump1, sump2; + register int src_exponent; + register boolean guardbit = FALSE, even_exponent; + + Dbl_copyfromptr(srcptr,srcp1,srcp2); + /* + * check source operand for NaN or infinity + */ + if ((src_exponent = Dbl_exponent(srcp1)) == DBL_INFINITY_EXPONENT) { + /* + * is signaling NaN? + */ + if (Dbl_isone_signaling(srcp1)) { + /* trap if INVALIDTRAP enabled */ + if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION); + /* make NaN quiet */ + Set_invalidflag(); + Dbl_set_quiet(srcp1); + } + /* + * Return quiet NaN or positive infinity. + * Fall through to negative test if negative infinity. + */ + if (Dbl_iszero_sign(srcp1) || + Dbl_isnotzero_mantissa(srcp1,srcp2)) { + Dbl_copytoptr(srcp1,srcp2,dstptr); + return(NOEXCEPTION); + } + } + + /* + * check for zero source operand + */ + if (Dbl_iszero_exponentmantissa(srcp1,srcp2)) { + Dbl_copytoptr(srcp1,srcp2,dstptr); + return(NOEXCEPTION); + } + + /* + * check for negative source operand + */ + if (Dbl_isone_sign(srcp1)) { + /* trap if INVALIDTRAP enabled */ + if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION); + /* make NaN quiet */ + Set_invalidflag(); + Dbl_makequietnan(srcp1,srcp2); + Dbl_copytoptr(srcp1,srcp2,dstptr); + return(NOEXCEPTION); + } + + /* + * Generate result + */ + if (src_exponent > 0) { + even_exponent = Dbl_hidden(srcp1); + Dbl_clear_signexponent_set_hidden(srcp1); + } + else { + /* normalize operand */ + Dbl_clear_signexponent(srcp1); + src_exponent++; + Dbl_normalize(srcp1,srcp2,src_exponent); + even_exponent = src_exponent & 1; + } + if (even_exponent) { + /* exponent is even */ + /* Add comment here. Explain why odd exponent needs correction */ + Dbl_leftshiftby1(srcp1,srcp2); + } + /* + * Add comment here. Explain following algorithm. + * + * Trust me, it works. + * + */ + Dbl_setzero(resultp1,resultp2); + Dbl_allp1(newbitp1) = 1 << (DBL_P - 32); + Dbl_setzero_mantissap2(newbitp2); + while (Dbl_isnotzero(newbitp1,newbitp2) && Dbl_isnotzero(srcp1,srcp2)) { + Dbl_addition(resultp1,resultp2,newbitp1,newbitp2,sump1,sump2); + if(Dbl_isnotgreaterthan(sump1,sump2,srcp1,srcp2)) { + Dbl_leftshiftby1(newbitp1,newbitp2); + /* update result */ + Dbl_addition(resultp1,resultp2,newbitp1,newbitp2, + resultp1,resultp2); + Dbl_subtract(srcp1,srcp2,sump1,sump2,srcp1,srcp2); + Dbl_rightshiftby2(newbitp1,newbitp2); + } + else { + Dbl_rightshiftby1(newbitp1,newbitp2); + } + Dbl_leftshiftby1(srcp1,srcp2); + } + /* correct exponent for pre-shift */ + if (even_exponent) { + Dbl_rightshiftby1(resultp1,resultp2); + } + + /* check for inexact */ + if (Dbl_isnotzero(srcp1,srcp2)) { + if (!even_exponent && Dbl_islessthan(resultp1,resultp2,srcp1,srcp2)) { + Dbl_increment(resultp1,resultp2); + } + guardbit = Dbl_lowmantissap2(resultp2); + Dbl_rightshiftby1(resultp1,resultp2); + + /* now round result */ + switch (Rounding_mode()) { + case ROUNDPLUS: + Dbl_increment(resultp1,resultp2); + break; + case ROUNDNEAREST: + /* stickybit is always true, so guardbit + * is enough to determine rounding */ + if (guardbit) { + Dbl_increment(resultp1,resultp2); + } + break; + } + /* increment result exponent by 1 if mantissa overflowed */ + if (Dbl_isone_hiddenoverflow(resultp1)) src_exponent+=2; + + if (Is_inexacttrap_enabled()) { + Dbl_set_exponent(resultp1, + ((src_exponent-DBL_BIAS)>>1)+DBL_BIAS); + Dbl_copytoptr(resultp1,resultp2,dstptr); + return(INEXACTEXCEPTION); + } + else Set_inexactflag(); + } + else { + Dbl_rightshiftby1(resultp1,resultp2); + } + Dbl_set_exponent(resultp1,((src_exponent-DBL_BIAS)>>1)+DBL_BIAS); + Dbl_copytoptr(resultp1,resultp2,dstptr); + return(NOEXCEPTION); +} |