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Diffstat (limited to 'source/luametatex/source/libraries/softposit/source/s_subMagsP16.c')
| -rw-r--r-- | source/luametatex/source/libraries/softposit/source/s_subMagsP16.c | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/source/luametatex/source/libraries/softposit/source/s_subMagsP16.c b/source/luametatex/source/libraries/softposit/source/s_subMagsP16.c new file mode 100644 index 000000000..a0c9c33e2 --- /dev/null +++ b/source/luametatex/source/libraries/softposit/source/s_subMagsP16.c @@ -0,0 +1,175 @@ + +/*============================================================================ + +This C source file is part of the SoftPosit Posit Arithmetic Package +by S. H. Leong (Cerlane). + +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" + +#ifdef SOFTPOSIT_EXACT +posit16_t softposit_subMagsP16( uint_fast16_t uiA, uint_fast16_t uiB, bool isExact){ +#else +posit16_t softposit_subMagsP16( uint_fast16_t uiA, uint_fast16_t uiB ){ +#endif + uint_fast16_t regA; + uint_fast32_t frac32A, frac32B; + uint_fast16_t fracA=0, regime, tmp; + bool sign=0, regSA, regSB, ecarry=0, bitNPlusOne=0, bitsMore=0; + int_fast16_t shiftRight; + int_fast8_t kA=0, expA; + union ui16_p16 uZ; + + //Both uiA and uiB are actually the same signs if uiB inherits sign of sub + //Make both positive + sign = signP16UI( uiA ); + (sign)?(uiA = (-uiA & 0xFFFF)): (uiB = (-uiB & 0xFFFF)); + + if (uiA==uiB){ //essential, if not need special handling + uZ.ui = 0; + return uZ.p; + } + if(uiA<uiB){ + uiA ^= uiB; + uiB ^= uiA; + uiA ^= uiB; + (sign) ? (sign = 0 ) : (sign=1); //A becomes B + } + + regSA = signregP16UI( uiA ); + regSB = signregP16UI( uiB ); + + tmp = (uiA<<2) & 0xFFFF; + if (regSA){ + while (tmp>>15){ + kA++; + tmp= (tmp<<1) & 0xFFFF; + } + } + else{ + kA=-1; + while (!(tmp>>15)){ + kA--; + tmp= (tmp<<1) & 0xFFFF; + } + tmp&=0x7FFF; + } + expA = tmp>>14; + frac32A = (0x4000 | tmp) << 16; + shiftRight = kA; + + tmp = (uiB<<2) & 0xFFFF; + if (regSB){ + while (tmp>>15){ + shiftRight--; + tmp= (tmp<<1) & 0xFFFF; + } + } + else{ + shiftRight++; + while (!(tmp>>15)){ + shiftRight++; + tmp= (tmp<<1) & 0xFFFF; + } + tmp&=0x7FFF; + } + frac32B = (0x4000 | tmp) <<16; + //This is 2kZ + expZ; (where kZ=kA-kB and expZ=expA-expB) + + shiftRight = (shiftRight<<1) + expA - (tmp>>14); + + if (shiftRight!=0){ + if (shiftRight>=29){ + uZ.ui = uiA; + if (sign) uZ.ui = -uZ.ui & 0xFFFF; + return uZ.p; + } + else + frac32B >>= shiftRight; + } + + frac32A -= frac32B; + + while((frac32A>>29)==0){ + kA--; + frac32A<<=2; + } + ecarry = (0x40000000 & frac32A)>>30; + if(!ecarry){ + if (expA==0) kA--; + expA^=1; + frac32A<<=1; + } + + if(kA<0){ + regA = (-kA & 0xFFFF); + regSA = 0; + regime = 0x4000>>regA; + } + else{ + regA = kA+1; + regSA=1; + regime = 0x7FFF - (0x7FFF>>regA); + } + + if(regA>14){ + //max or min pos. exp and frac does not matter. + (regSA) ? (uZ.ui= 0x7FFF): (uZ.ui=0x1); + } + else{ + //remove hidden bits + frac32A = (frac32A & 0x3FFFFFFF) >>(regA + 1) ; + fracA = frac32A>>16; + if (regA!=14) bitNPlusOne = (frac32A>>15) & 0x1; + else if (frac32A>0){ + fracA=0; + bitsMore =1; + } + if (regA==14 && expA) bitNPlusOne = 1; + uZ.ui = packToP16UI(regime, regA, expA, fracA); + if (bitNPlusOne){ + if ( frac32A&0x7FFF ) bitsMore=1; + //n+1 frac bit is 1. Need to check if another bit is 1 too if not round to even + uZ.ui += (uZ.ui&1) | bitsMore; + } + } + if (sign) uZ.ui = -uZ.ui & 0xFFFF; + return uZ.p; + +} + |