diff options
Diffstat (limited to 'lib/builtins/fp_add_impl.inc')
| -rw-r--r-- | lib/builtins/fp_add_impl.inc | 258 |
1 files changed, 135 insertions, 123 deletions
diff --git a/lib/builtins/fp_add_impl.inc b/lib/builtins/fp_add_impl.inc index b47be1b64..b5a2fb098 100644 --- a/lib/builtins/fp_add_impl.inc +++ b/lib/builtins/fp_add_impl.inc @@ -1,9 +1,8 @@ //===----- lib/fp_add_impl.inc - floaing point addition -----------*- C -*-===// // -// The LLVM Compiler Infrastructure -// -// This file is dual licensed under the MIT and the University of Illinois Open -// Source Licenses. See LICENSE.TXT for details. +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// // @@ -15,130 +14,143 @@ #include "fp_lib.h" static __inline fp_t __addXf3__(fp_t a, fp_t b) { - rep_t aRep = toRep(a); - rep_t bRep = toRep(b); - const rep_t aAbs = aRep & absMask; - const rep_t bAbs = bRep & absMask; - - // Detect if a or b is zero, infinity, or NaN. - if (aAbs - REP_C(1) >= infRep - REP_C(1) || - bAbs - REP_C(1) >= infRep - REP_C(1)) { - // NaN + anything = qNaN - if (aAbs > infRep) return fromRep(toRep(a) | quietBit); - // anything + NaN = qNaN - if (bAbs > infRep) return fromRep(toRep(b) | quietBit); - - if (aAbs == infRep) { - // +/-infinity + -/+infinity = qNaN - if ((toRep(a) ^ toRep(b)) == signBit) return fromRep(qnanRep); - // +/-infinity + anything remaining = +/- infinity - else return a; - } - - // anything remaining + +/-infinity = +/-infinity - if (bAbs == infRep) return b; - - // zero + anything = anything - if (!aAbs) { - // but we need to get the sign right for zero + zero - if (!bAbs) return fromRep(toRep(a) & toRep(b)); - else return b; - } - - // anything + zero = anything - if (!bAbs) return a; + rep_t aRep = toRep(a); + rep_t bRep = toRep(b); + const rep_t aAbs = aRep & absMask; + const rep_t bAbs = bRep & absMask; + + // Detect if a or b is zero, infinity, or NaN. + if (aAbs - REP_C(1) >= infRep - REP_C(1) || + bAbs - REP_C(1) >= infRep - REP_C(1)) { + // NaN + anything = qNaN + if (aAbs > infRep) + return fromRep(toRep(a) | quietBit); + // anything + NaN = qNaN + if (bAbs > infRep) + return fromRep(toRep(b) | quietBit); + + if (aAbs == infRep) { + // +/-infinity + -/+infinity = qNaN + if ((toRep(a) ^ toRep(b)) == signBit) + return fromRep(qnanRep); + // +/-infinity + anything remaining = +/- infinity + else + return a; } - // Swap a and b if necessary so that a has the larger absolute value. - if (bAbs > aAbs) { - const rep_t temp = aRep; - aRep = bRep; - bRep = temp; + // anything remaining + +/-infinity = +/-infinity + if (bAbs == infRep) + return b; + + // zero + anything = anything + if (!aAbs) { + // but we need to get the sign right for zero + zero + if (!bAbs) + return fromRep(toRep(a) & toRep(b)); + else + return b; } - // Extract the exponent and significand from the (possibly swapped) a and b. - int aExponent = aRep >> significandBits & maxExponent; - int bExponent = bRep >> significandBits & maxExponent; - rep_t aSignificand = aRep & significandMask; - rep_t bSignificand = bRep & significandMask; - - // Normalize any denormals, and adjust the exponent accordingly. - if (aExponent == 0) aExponent = normalize(&aSignificand); - if (bExponent == 0) bExponent = normalize(&bSignificand); - - // The sign of the result is the sign of the larger operand, a. If they - // have opposite signs, we are performing a subtraction; otherwise addition. - const rep_t resultSign = aRep & signBit; - const bool subtraction = (aRep ^ bRep) & signBit; - - // Shift the significands to give us round, guard and sticky, and or in the - // implicit significand bit. (If we fell through from the denormal path it - // was already set by normalize( ), but setting it twice won't hurt - // anything.) - aSignificand = (aSignificand | implicitBit) << 3; - bSignificand = (bSignificand | implicitBit) << 3; - - // Shift the significand of b by the difference in exponents, with a sticky - // bottom bit to get rounding correct. - const unsigned int align = aExponent - bExponent; - if (align) { - if (align < typeWidth) { - const bool sticky = bSignificand << (typeWidth - align); - bSignificand = bSignificand >> align | sticky; - } else { - bSignificand = 1; // sticky; b is known to be non-zero. - } - } - if (subtraction) { - aSignificand -= bSignificand; - // If a == -b, return +zero. - if (aSignificand == 0) return fromRep(0); - - // If partial cancellation occured, we need to left-shift the result - // and adjust the exponent: - if (aSignificand < implicitBit << 3) { - const int shift = rep_clz(aSignificand) - rep_clz(implicitBit << 3); - aSignificand <<= shift; - aExponent -= shift; - } + // anything + zero = anything + if (!bAbs) + return a; + } + + // Swap a and b if necessary so that a has the larger absolute value. + if (bAbs > aAbs) { + const rep_t temp = aRep; + aRep = bRep; + bRep = temp; + } + + // Extract the exponent and significand from the (possibly swapped) a and b. + int aExponent = aRep >> significandBits & maxExponent; + int bExponent = bRep >> significandBits & maxExponent; + rep_t aSignificand = aRep & significandMask; + rep_t bSignificand = bRep & significandMask; + + // Normalize any denormals, and adjust the exponent accordingly. + if (aExponent == 0) + aExponent = normalize(&aSignificand); + if (bExponent == 0) + bExponent = normalize(&bSignificand); + + // The sign of the result is the sign of the larger operand, a. If they + // have opposite signs, we are performing a subtraction; otherwise addition. + const rep_t resultSign = aRep & signBit; + const bool subtraction = (aRep ^ bRep) & signBit; + + // Shift the significands to give us round, guard and sticky, and or in the + // implicit significand bit. (If we fell through from the denormal path it + // was already set by normalize( ), but setting it twice won't hurt + // anything.) + aSignificand = (aSignificand | implicitBit) << 3; + bSignificand = (bSignificand | implicitBit) << 3; + + // Shift the significand of b by the difference in exponents, with a sticky + // bottom bit to get rounding correct. + const unsigned int align = aExponent - bExponent; + if (align) { + if (align < typeWidth) { + const bool sticky = bSignificand << (typeWidth - align); + bSignificand = bSignificand >> align | sticky; + } else { + bSignificand = 1; // sticky; b is known to be non-zero. } - else /* addition */ { - aSignificand += bSignificand; - - // If the addition carried up, we need to right-shift the result and - // adjust the exponent: - if (aSignificand & implicitBit << 4) { - const bool sticky = aSignificand & 1; - aSignificand = aSignificand >> 1 | sticky; - aExponent += 1; - } + } + if (subtraction) { + aSignificand -= bSignificand; + // If a == -b, return +zero. + if (aSignificand == 0) + return fromRep(0); + + // If partial cancellation occured, we need to left-shift the result + // and adjust the exponent: + if (aSignificand < implicitBit << 3) { + const int shift = rep_clz(aSignificand) - rep_clz(implicitBit << 3); + aSignificand <<= shift; + aExponent -= shift; } - - // If we have overflowed the type, return +/- infinity: - if (aExponent >= maxExponent) return fromRep(infRep | resultSign); - - if (aExponent <= 0) { - // Result is denormal before rounding; the exponent is zero and we - // need to shift the significand. - const int shift = 1 - aExponent; - const bool sticky = aSignificand << (typeWidth - shift); - aSignificand = aSignificand >> shift | sticky; - aExponent = 0; + } else /* addition */ { + aSignificand += bSignificand; + + // If the addition carried up, we need to right-shift the result and + // adjust the exponent: + if (aSignificand & implicitBit << 4) { + const bool sticky = aSignificand & 1; + aSignificand = aSignificand >> 1 | sticky; + aExponent += 1; } - - // Low three bits are round, guard, and sticky. - const int roundGuardSticky = aSignificand & 0x7; - - // Shift the significand into place, and mask off the implicit bit. - rep_t result = aSignificand >> 3 & significandMask; - - // Insert the exponent and sign. - result |= (rep_t)aExponent << significandBits; - result |= resultSign; - - // Final rounding. The result may overflow to infinity, but that is the - // correct result in that case. - if (roundGuardSticky > 0x4) result++; - if (roundGuardSticky == 0x4) result += result & 1; - return fromRep(result); + } + + // If we have overflowed the type, return +/- infinity: + if (aExponent >= maxExponent) + return fromRep(infRep | resultSign); + + if (aExponent <= 0) { + // Result is denormal before rounding; the exponent is zero and we + // need to shift the significand. + const int shift = 1 - aExponent; + const bool sticky = aSignificand << (typeWidth - shift); + aSignificand = aSignificand >> shift | sticky; + aExponent = 0; + } + + // Low three bits are round, guard, and sticky. + const int roundGuardSticky = aSignificand & 0x7; + + // Shift the significand into place, and mask off the implicit bit. + rep_t result = aSignificand >> 3 & significandMask; + + // Insert the exponent and sign. + result |= (rep_t)aExponent << significandBits; + result |= resultSign; + + // Final rounding. The result may overflow to infinity, but that is the + // correct result in that case. + if (roundGuardSticky > 0x4) + result++; + if (roundGuardSticky == 0x4) + result += result & 1; + return fromRep(result); } |