GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: lib/libcompiler_rt/fp_add_impl.inc Lines: 0 58 0.0 %
Date: 2017-11-13 Branches: 0 46 0.0 %

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//===----- lib/fp_add_impl.inc - floaing point addition -----------*- C -*-===//
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//
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//                     The LLVM Compiler Infrastructure
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//
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// This file is dual licensed under the MIT and the University of Illinois Open
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// Source Licenses. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements soft-float addition with the IEEE-754 default rounding
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// (to nearest, ties to even).
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//
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//===----------------------------------------------------------------------===//
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#include "fp_lib.h"
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static __inline fp_t __addXf3__(fp_t a, fp_t b) {
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    rep_t aRep = toRep(a);
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    rep_t bRep = toRep(b);
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    const rep_t aAbs = aRep & absMask;
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    const rep_t bAbs = bRep & absMask;
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    // Detect if a or b is zero, infinity, or NaN.
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    if (aAbs - REP_C(1) >= infRep - REP_C(1) ||
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        bAbs - REP_C(1) >= infRep - REP_C(1)) {
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        // NaN + anything = qNaN
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        if (aAbs > infRep) return fromRep(toRep(a) | quietBit);
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        // anything + NaN = qNaN
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        if (bAbs > infRep) return fromRep(toRep(b) | quietBit);
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        if (aAbs == infRep) {
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            // +/-infinity + -/+infinity = qNaN
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            if ((toRep(a) ^ toRep(b)) == signBit) return fromRep(qnanRep);
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            // +/-infinity + anything remaining = +/- infinity
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            else return a;
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        }
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        // anything remaining + +/-infinity = +/-infinity
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        if (bAbs == infRep) return b;
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        // zero + anything = anything
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        if (!aAbs) {
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            // but we need to get the sign right for zero + zero
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            if (!bAbs) return fromRep(toRep(a) & toRep(b));
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            else return b;
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        }
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        // anything + zero = anything
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        if (!bAbs) return a;
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    }
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    // Swap a and b if necessary so that a has the larger absolute value.
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    if (bAbs > aAbs) {
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        const rep_t temp = aRep;
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        aRep = bRep;
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        bRep = temp;
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    }
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    // Extract the exponent and significand from the (possibly swapped) a and b.
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    int aExponent = aRep >> significandBits & maxExponent;
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    int bExponent = bRep >> significandBits & maxExponent;
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    rep_t aSignificand = aRep & significandMask;
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    rep_t bSignificand = bRep & significandMask;
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    // Normalize any denormals, and adjust the exponent accordingly.
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    if (aExponent == 0) aExponent = normalize(&aSignificand);
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    if (bExponent == 0) bExponent = normalize(&bSignificand);
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    // The sign of the result is the sign of the larger operand, a.  If they
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    // have opposite signs, we are performing a subtraction; otherwise addition.
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    const rep_t resultSign = aRep & signBit;
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    const bool subtraction = (aRep ^ bRep) & signBit;
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    // Shift the significands to give us round, guard and sticky, and or in the
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    // implicit significand bit.  (If we fell through from the denormal path it
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    // was already set by normalize( ), but setting it twice won't hurt
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    // anything.)
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    aSignificand = (aSignificand | implicitBit) << 3;
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    bSignificand = (bSignificand | implicitBit) << 3;
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    // Shift the significand of b by the difference in exponents, with a sticky
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    // bottom bit to get rounding correct.
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    const unsigned int align = aExponent - bExponent;
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    if (align) {
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        if (align < typeWidth) {
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            const bool sticky = bSignificand << (typeWidth - align);
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            bSignificand = bSignificand >> align | sticky;
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        } else {
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            bSignificand = 1; // sticky; b is known to be non-zero.
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        }
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    }
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    if (subtraction) {
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        aSignificand -= bSignificand;
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        // If a == -b, return +zero.
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        if (aSignificand == 0) return fromRep(0);
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        // If partial cancellation occured, we need to left-shift the result
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        // and adjust the exponent:
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        if (aSignificand < implicitBit << 3) {
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            const int shift = rep_clz(aSignificand) - rep_clz(implicitBit << 3);
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            aSignificand <<= shift;
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            aExponent -= shift;
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        }
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    }
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    else /* addition */ {
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        aSignificand += bSignificand;
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        // If the addition carried up, we need to right-shift the result and
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        // adjust the exponent:
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        if (aSignificand & implicitBit << 4) {
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            const bool sticky = aSignificand & 1;
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            aSignificand = aSignificand >> 1 | sticky;
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            aExponent += 1;
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        }
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    }
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    // If we have overflowed the type, return +/- infinity:
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    if (aExponent >= maxExponent) return fromRep(infRep | resultSign);
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    if (aExponent <= 0) {
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        // Result is denormal before rounding; the exponent is zero and we
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        // need to shift the significand.
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        const int shift = 1 - aExponent;
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        const bool sticky = aSignificand << (typeWidth - shift);
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        aSignificand = aSignificand >> shift | sticky;
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        aExponent = 0;
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    }
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    // Low three bits are round, guard, and sticky.
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    const int roundGuardSticky = aSignificand & 0x7;
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    // Shift the significand into place, and mask off the implicit bit.
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    rep_t result = aSignificand >> 3 & significandMask;
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    // Insert the exponent and sign.
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    result |= (rep_t)aExponent << significandBits;
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    result |= resultSign;
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    // Final rounding.  The result may overflow to infinity, but that is the
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    // correct result in that case.
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    if (roundGuardSticky > 0x4) result++;
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    if (roundGuardSticky == 0x4) result += result & 1;
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    return fromRep(result);
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}