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Diffstat (limited to 'source/luametatex/source/libraries/softposit/source/s_subMagsP8.c')
| -rw-r--r-- | source/luametatex/source/libraries/softposit/source/s_subMagsP8.c | 160 |
1 files changed, 160 insertions, 0 deletions
diff --git a/source/luametatex/source/libraries/softposit/source/s_subMagsP8.c b/source/luametatex/source/libraries/softposit/source/s_subMagsP8.c new file mode 100644 index 000000000..dd48c4225 --- /dev/null +++ b/source/luametatex/source/libraries/softposit/source/s_subMagsP8.c @@ -0,0 +1,160 @@ + +/*============================================================================ + +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. + +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 +posit8_t softposit_subMagsP8( uint_fast8_t uiA, uint_fast8_t uiB, bool isExact){ +#else +posit8_t softposit_subMagsP8( uint_fast8_t uiA, uint_fast8_t uiB ){ +#endif + uint_fast8_t regA; + uint_fast16_t frac16A, frac16B; + uint_fast8_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; + union ui8_p8 uZ; + + + //Both uiA and uiB are actually the same signs if uiB inherits sign of sub + //Make both positive + sign = signP8UI( uiA ); + (sign)? (uiA = (-uiA & 0xFF)): (uiB = (-uiB & 0xFF)); + + 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 = signregP8UI( uiA ); + regSB = signregP8UI( uiB ); + + tmp = (uiA<<2) & 0xFF; + if (regSA){ + while (tmp>>7){ + kA++; + tmp= (tmp<<1) & 0xFF; + } + } + else{ + kA=-1; + while (!(tmp>>7)){ + kA--; + tmp= (tmp<<1) & 0xFF; + } + tmp&=0x7F; + } + frac16A = (0x80 | tmp) << 7; + shiftRight = kA; + + tmp = (uiB<<2) & 0xFF; + if (regSB){ + while (tmp>>7){ + shiftRight--; + tmp= (tmp<<1) & 0xFF; + } + } + else{ + shiftRight++; + while (!(tmp>>7)){ + shiftRight++; + tmp= (tmp<<1) & 0xFF; + } + tmp&=0x7F; + } + frac16B = (0x80 | tmp) <<7; + + + if (shiftRight>=14){ + uZ.ui = uiA; + if (sign) uZ.ui = -uZ.ui & 0xFFFF; + return uZ.p; + } + else + frac16B >>= shiftRight; + + frac16A -= frac16B; + + while((frac16A>>14)==0){ + kA--; + frac16A<<=1; + } + ecarry = (0x4000 & frac16A)>>14; + if(!ecarry){ + kA--; + frac16A<<=1; + } + + if(kA<0){ + regA = (-kA & 0xFF); + regSA = 0; + regime = 0x40>>regA; + } + else{ + regA = kA+1; + regSA=1; + regime = 0x7F-(0x7F>>regA); + } + + if(regA>6){ + //max or min pos. exp and frac does not matter. + (regSA) ? (uZ.ui= 0x7F): (uZ.ui=0x1); + } + else{ + frac16A = (frac16A&0x3FFF) >> regA; + fracA = (uint_fast8_t) (frac16A>>8); + bitNPlusOne = (0x80 & frac16A) ; + uZ.ui = packToP8UI(regime, fracA); + + if (bitNPlusOne){ + if (0x7F & frac16A) bitsMore=1; + uZ.ui += (uZ.ui&1) | bitsMore; + } + } + if (sign) uZ.ui = -uZ.ui & 0xFF; + return uZ.p; + +} + |