diff options
Diffstat (limited to 'lib/builtins/fp_mul_impl.inc')
| -rw-r--r-- | lib/builtins/fp_mul_impl.inc | 208 |
1 files changed, 110 insertions, 98 deletions
diff --git a/lib/builtins/fp_mul_impl.inc b/lib/builtins/fp_mul_impl.inc index b34aa1b8f544..a93f2d78ad6b 100644 --- a/lib/builtins/fp_mul_impl.inc +++ b/lib/builtins/fp_mul_impl.inc @@ -1,9 +1,8 @@ //===---- lib/fp_mul_impl.inc - floating point multiplication -----*- 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 // //===----------------------------------------------------------------------===// // @@ -15,102 +14,115 @@ #include "fp_lib.h" static __inline fp_t __mulXf3__(fp_t a, fp_t b) { - const unsigned int aExponent = toRep(a) >> significandBits & maxExponent; - const unsigned int bExponent = toRep(b) >> significandBits & maxExponent; - const rep_t productSign = (toRep(a) ^ toRep(b)) & signBit; - - rep_t aSignificand = toRep(a) & significandMask; - rep_t bSignificand = toRep(b) & significandMask; - int scale = 0; - - // Detect if a or b is zero, denormal, infinity, or NaN. - if (aExponent-1U >= maxExponent-1U || bExponent-1U >= maxExponent-1U) { - - const rep_t aAbs = toRep(a) & absMask; - const rep_t bAbs = toRep(b) & absMask; - - // 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 * non-zero = +/- infinity - if (bAbs) return fromRep(aAbs | productSign); - // infinity * zero = NaN - else return fromRep(qnanRep); - } - - if (bAbs == infRep) { - //? non-zero * infinity = +/- infinity - if (aAbs) return fromRep(bAbs | productSign); - // zero * infinity = NaN - else return fromRep(qnanRep); - } - - // zero * anything = +/- zero - if (!aAbs) return fromRep(productSign); - // anything * zero = +/- zero - if (!bAbs) return fromRep(productSign); - - // one or both of a or b is denormal, the other (if applicable) is a - // normal number. Renormalize one or both of a and b, and set scale to - // include the necessary exponent adjustment. - if (aAbs < implicitBit) scale += normalize(&aSignificand); - if (bAbs < implicitBit) scale += normalize(&bSignificand); + const unsigned int aExponent = toRep(a) >> significandBits & maxExponent; + const unsigned int bExponent = toRep(b) >> significandBits & maxExponent; + const rep_t productSign = (toRep(a) ^ toRep(b)) & signBit; + + rep_t aSignificand = toRep(a) & significandMask; + rep_t bSignificand = toRep(b) & significandMask; + int scale = 0; + + // Detect if a or b is zero, denormal, infinity, or NaN. + if (aExponent - 1U >= maxExponent - 1U || + bExponent - 1U >= maxExponent - 1U) { + + const rep_t aAbs = toRep(a) & absMask; + const rep_t bAbs = toRep(b) & absMask; + + // 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 * non-zero = +/- infinity + if (bAbs) + return fromRep(aAbs | productSign); + // infinity * zero = NaN + else + return fromRep(qnanRep); } - // 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 |= implicitBit; - bSignificand |= implicitBit; - - // Get the significand of a*b. Before multiplying the significands, shift - // one of them left to left-align it in the field. Thus, the product will - // have (exponentBits + 2) integral digits, all but two of which must be - // zero. Normalizing this result is just a conditional left-shift by one - // and bumping the exponent accordingly. - rep_t productHi, productLo; - wideMultiply(aSignificand, bSignificand << exponentBits, - &productHi, &productLo); - - int productExponent = aExponent + bExponent - exponentBias + scale; - - // Normalize the significand, adjust exponent if needed. - if (productHi & implicitBit) productExponent++; - else wideLeftShift(&productHi, &productLo, 1); - - // If we have overflowed the type, return +/- infinity. - if (productExponent >= maxExponent) return fromRep(infRep | productSign); - - if (productExponent <= 0) { - // Result is denormal before rounding - // - // If the result is so small that it just underflows to zero, return - // a zero of the appropriate sign. Mathematically there is no need to - // handle this case separately, but we make it a special case to - // simplify the shift logic. - const unsigned int shift = REP_C(1) - (unsigned int)productExponent; - if (shift >= typeWidth) return fromRep(productSign); - - // Otherwise, shift the significand of the result so that the round - // bit is the high bit of productLo. - wideRightShiftWithSticky(&productHi, &productLo, shift); - } - else { - // Result is normal before rounding; insert the exponent. - productHi &= significandMask; - productHi |= (rep_t)productExponent << significandBits; + if (bAbs == infRep) { + // non-zero * infinity = +/- infinity + if (aAbs) + return fromRep(bAbs | productSign); + // zero * infinity = NaN + else + return fromRep(qnanRep); } - // Insert the sign of the result: - productHi |= productSign; - - // Final rounding. The final result may overflow to infinity, or underflow - // to zero, but those are the correct results in those cases. We use the - // default IEEE-754 round-to-nearest, ties-to-even rounding mode. - if (productLo > signBit) productHi++; - if (productLo == signBit) productHi += productHi & 1; - return fromRep(productHi); + // zero * anything = +/- zero + if (!aAbs) + return fromRep(productSign); + // anything * zero = +/- zero + if (!bAbs) + return fromRep(productSign); + + // One or both of a or b is denormal. The other (if applicable) is a + // normal number. Renormalize one or both of a and b, and set scale to + // include the necessary exponent adjustment. + if (aAbs < implicitBit) + scale += normalize(&aSignificand); + if (bAbs < implicitBit) + scale += normalize(&bSignificand); + } + + // Set 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 |= implicitBit; + bSignificand |= implicitBit; + + // Perform a basic multiplication on the significands. One of them must be + // shifted beforehand to be aligned with the exponent. + rep_t productHi, productLo; + wideMultiply(aSignificand, bSignificand << exponentBits, &productHi, + &productLo); + + int productExponent = aExponent + bExponent - exponentBias + scale; + + // Normalize the significand and adjust the exponent if needed. + if (productHi & implicitBit) + productExponent++; + else + wideLeftShift(&productHi, &productLo, 1); + + // If we have overflowed the type, return +/- infinity. + if (productExponent >= maxExponent) + return fromRep(infRep | productSign); + + if (productExponent <= 0) { + // The result is denormal before rounding. + // + // If the result is so small that it just underflows to zero, return + // zero with the appropriate sign. Mathematically, there is no need to + // handle this case separately, but we make it a special case to + // simplify the shift logic. + const unsigned int shift = REP_C(1) - (unsigned int)productExponent; + if (shift >= typeWidth) + return fromRep(productSign); + + // Otherwise, shift the significand of the result so that the round + // bit is the high bit of productLo. + wideRightShiftWithSticky(&productHi, &productLo, shift); + } else { + // The result is normal before rounding. Insert the exponent. + productHi &= significandMask; + productHi |= (rep_t)productExponent << significandBits; + } + + // Insert the sign of the result. + productHi |= productSign; + + // Perform the final rounding. The final result may overflow to infinity, + // or underflow to zero, but those are the correct results in those cases. + // We use the default IEEE-754 round-to-nearest, ties-to-even rounding mode. + if (productLo > signBit) + productHi++; + if (productLo == signBit) + productHi += productHi & 1; + return fromRep(productHi); } |