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174 lines
4.1 KiB
174 lines
4.1 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/sfsqrt.c $Revision: 1.1 $ |
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* |
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* Purpose: |
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* Single Floating-point Square Root |
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* |
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* External Interfaces: |
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* sgl_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 "sgl_float.h" |
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/* |
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* Single Floating-point Square Root |
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*/ |
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/*ARGSUSED*/ |
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unsigned int |
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sgl_fsqrt( |
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sgl_floating_point *srcptr, |
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unsigned int *nullptr, |
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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 src, result; |
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register int src_exponent; |
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register unsigned int newbit, sum; |
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register boolean guardbit = FALSE, even_exponent; |
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src = *srcptr; |
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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 = Sgl_exponent(src)) == SGL_INFINITY_EXPONENT) { |
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/* |
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* is signaling NaN? |
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*/ |
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if (Sgl_isone_signaling(src)) { |
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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(src); |
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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 (Sgl_iszero_sign(src) || Sgl_isnotzero_mantissa(src)) { |
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*dstptr = src; |
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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 (Sgl_iszero_exponentmantissa(src)) { |
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*dstptr = src; |
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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 (Sgl_isone_sign(src)) { |
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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_makequietnan(src); |
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*dstptr = src; |
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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 = Sgl_hidden(src); |
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Sgl_clear_signexponent_set_hidden(src); |
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} |
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else { |
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/* normalize operand */ |
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Sgl_clear_signexponent(src); |
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src_exponent++; |
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Sgl_normalize(src,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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Sgl_leftshiftby1(src); |
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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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Sgl_setzero(result); |
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newbit = 1 << SGL_P; |
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while (newbit && Sgl_isnotzero(src)) { |
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Sgl_addition(result,newbit,sum); |
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if(sum <= Sgl_all(src)) { |
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/* update result */ |
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Sgl_addition(result,(newbit<<1),result); |
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Sgl_subtract(src,sum,src); |
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} |
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Sgl_rightshiftby1(newbit); |
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Sgl_leftshiftby1(src); |
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} |
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/* correct exponent for pre-shift */ |
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if (even_exponent) { |
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Sgl_rightshiftby1(result); |
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} |
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/* check for inexact */ |
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if (Sgl_isnotzero(src)) { |
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if (!even_exponent && Sgl_islessthan(result,src)) |
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Sgl_increment(result); |
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guardbit = Sgl_lowmantissa(result); |
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Sgl_rightshiftby1(result); |
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/* now round result */ |
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switch (Rounding_mode()) { |
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case ROUNDPLUS: |
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Sgl_increment(result); |
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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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Sgl_increment(result); |
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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 (Sgl_isone_hiddenoverflow(result)) src_exponent+=2; |
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if (Is_inexacttrap_enabled()) { |
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Sgl_set_exponent(result, |
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((src_exponent-SGL_BIAS)>>1)+SGL_BIAS); |
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*dstptr = result; |
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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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Sgl_rightshiftby1(result); |
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} |
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Sgl_set_exponent(result,((src_exponent-SGL_BIAS)>>1)+SGL_BIAS); |
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*dstptr = result; |
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return(NOEXCEPTION); |
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}
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