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Diffstat (limited to 'source/luametatex/source/libraries/softposit/source/p16_roundToInt.c')
| -rw-r--r-- | source/luametatex/source/libraries/softposit/source/p16_roundToInt.c | 98 |
1 files changed, 98 insertions, 0 deletions
diff --git a/source/luametatex/source/libraries/softposit/source/p16_roundToInt.c b/source/luametatex/source/libraries/softposit/source/p16_roundToInt.c new file mode 100644 index 000000000..383fdb131 --- /dev/null +++ b/source/luametatex/source/libraries/softposit/source/p16_roundToInt.c @@ -0,0 +1,98 @@ + +/*============================================================================ + +This C source file is part of the SoftPosit Posit Arithmetic Package +by S. H. Leong (Cerlane) and John Gustafson. + +Copyright 2017, 2018 A*STAR. All rights reserved. + +This C source file was based on SoftFloat IEEE Floating-Point Arithmetic +Package, Release 3d, by John R. Hauser. + +Copyright 2011, 2012, 2013, 2014, 2015, 2016, 2017 The Regents of the +University of California. All rights reserved. + +Redistribution and use in source and binary forms, with or without +modification, are permitted provided that the following conditions are met: + + 1. Redistributions of source code must retain the above copyright notice, + this list of conditions, and the following disclaimer. + + 2. Redistributions in binary form must reproduce the above copyright notice, + this list of conditions, and the following disclaimer in the documentation + and/or other materials provided with the distribution. + + 3. Neither the name of the University nor the names of its contributors may + be used to endorse or promote products derived from this software without + specific prior written permission. + +THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS "AS IS", AND ANY +EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED +WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ARE +DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY +DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES +(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; +LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND +ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS +SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + +=============================================================================*/ + +#include "platform.h" +#include "internals.h" + + +posit16_t p16_roundToInt( posit16_t pA ) { + + union ui16_p16 uA; + uint_fast16_t mask = 0x2000, scale=0, tmp=0, uiA; + bool bitLast, bitNPlusOne, sign; + + uA.p = pA; + uiA = uA.ui; // Copy of the input. + sign = (uiA > 0x8000); + + // sign is True if pA > NaR. + if (sign) uiA = -uiA & 0xFFFF; // A is now |A|. + if (uiA <= 0x3000) { // 0 <= |pA| <= 1/2 rounds to zero. + uA.ui = 0; + return uA.p; + } + else if (uiA < 0x4800) { // 1/2 < x < 3/2 rounds to 1. + uA.ui = 0x4000; + } + else if (uiA <= 0x5400) { // 3/2 <= x <= 5/2 rounds to 2. + uA.ui = 0x5000; + } + else if (uiA >= 0x7C00) { // If |A| is 256 or greater, leave it unchanged. + return uA.p; // This also takes care of the NaR case, 0x8000. + } + else { // 34% of the cases, we have to decode the posit. + while (mask & uiA) { // Increment scale by 2 for each regime sign bit. + scale += 2; // Regime sign bit is always 1 in this range. + mask >>= 1; // Move the mask right, to the next bit. + } + mask >>= 1; // Skip over termination bit. + if (mask & uiA) scale++; // If exponent is 1, increment the scale. + + mask >>= scale; // Point to the last bit of the integer part. + bitLast = (uiA & mask); // Extract the bit, without shifting it. + + mask >>= 1; + tmp = (uiA & mask); + bitNPlusOne = tmp; // "True" if nonzero. + uiA ^= tmp; // Erase the bit, if it was set. + tmp = uiA & (mask - 1); // tmp has any remaining bits. + uiA ^= tmp; // Erase those bits, if any were set. + + if (bitNPlusOne) { // logic for round to nearest, tie to even + if (bitLast | tmp) uiA += (mask << 1); + } + uA.ui = uiA; + } + if (sign) uA.ui = -uA.ui & 0xFFFF; // Apply the sign of Z. + return uA.p; + +} + |