Merge branch 'rightlib' into mergelibs-241016-1210

1 files changed, 16 insertions, 172 deletions

diff --git a/contrib/libs/cxxsupp/builtins/divdf3.c b/contrib/libs/cxxsupp/builtins/divdf3.c
index ab44c2b25f..4c11759e0c 100644
--- a/contrib/libs/cxxsupp/builtins/divdf3.c
+++ b/contrib/libs/cxxsupp/builtins/divdf3.c
@@ -1,185 +1,29 @@
 //===-- lib/divdf3.c - Double-precision division ------------------*- 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
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements double-precision soft-float division
 // with the IEEE-754 default rounding (to nearest, ties to even).
 //
-// For simplicity, this implementation currently flushes denormals to zero.
-// It should be a fairly straightforward exercise to implement gradual
-// underflow with correct rounding.
-//
 //===----------------------------------------------------------------------===//
 
 #define DOUBLE_PRECISION
-#include "fp_lib.h"
 
-ARM_EABI_FNALIAS(ddiv, divdf3)
+#define NUMBER_OF_HALF_ITERATIONS 3
+#define NUMBER_OF_FULL_ITERATIONS 1
+
+#include "fp_div_impl.inc"
+
+COMPILER_RT_ABI fp_t __divdf3(fp_t a, fp_t b) { return __divXf3__(a, b); }
 
-COMPILER_RT_ABI fp_t
-__divdf3(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 quotientSign = (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 / infinity = NaN
-            if (bAbs == infRep) return fromRep(qnanRep);
-            // infinity / anything else = +/- infinity
-            else return fromRep(aAbs | quotientSign);
-        }
-        
-        // anything else / infinity = +/- 0
-        if (bAbs == infRep) return fromRep(quotientSign);
-        
-        if (!aAbs) {
-            // zero / zero = NaN
-            if (!bAbs) return fromRep(qnanRep);
-            // zero / anything else = +/- zero
-            else return fromRep(quotientSign);
-        }
-        // anything else / zero = +/- infinity
-        if (!bAbs) return fromRep(infRep | quotientSign);
-        
-        // 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);
-    }
-    
-    // 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;
-    int quotientExponent = aExponent - bExponent + scale;
-    
-    // Align the significand of b as a Q31 fixed-point number in the range
-    // [1, 2.0) and get a Q32 approximate reciprocal using a small minimax
-    // polynomial approximation: reciprocal = 3/4 + 1/sqrt(2) - b/2.  This
-    // is accurate to about 3.5 binary digits.
-    const uint32_t q31b = bSignificand >> 21;
-    uint32_t recip32 = UINT32_C(0x7504f333) - q31b;
-    
-    // Now refine the reciprocal estimate using a Newton-Raphson iteration:
-    //
-    //     x1 = x0 * (2 - x0 * b)
-    //
-    // This doubles the number of correct binary digits in the approximation
-    // with each iteration, so after three iterations, we have about 28 binary
-    // digits of accuracy.
-    uint32_t correction32;
-    correction32 = -((uint64_t)recip32 * q31b >> 32);
-    recip32 = (uint64_t)recip32 * correction32 >> 31;
-    correction32 = -((uint64_t)recip32 * q31b >> 32);
-    recip32 = (uint64_t)recip32 * correction32 >> 31;
-    correction32 = -((uint64_t)recip32 * q31b >> 32);
-    recip32 = (uint64_t)recip32 * correction32 >> 31;
-    
-    // recip32 might have overflowed to exactly zero in the preceding
-    // computation if the high word of b is exactly 1.0.  This would sabotage
-    // the full-width final stage of the computation that follows, so we adjust
-    // recip32 downward by one bit.
-    recip32--;
-    
-    // We need to perform one more iteration to get us to 56 binary digits;
-    // The last iteration needs to happen with extra precision.
-    const uint32_t q63blo = bSignificand << 11;
-    uint64_t correction, reciprocal;
-    correction = -((uint64_t)recip32*q31b + ((uint64_t)recip32*q63blo >> 32));
-    uint32_t cHi = correction >> 32;
-    uint32_t cLo = correction;
-    reciprocal = (uint64_t)recip32*cHi + ((uint64_t)recip32*cLo >> 32);
-    
-    // We already adjusted the 32-bit estimate, now we need to adjust the final
-    // 64-bit reciprocal estimate downward to ensure that it is strictly smaller
-    // than the infinitely precise exact reciprocal.  Because the computation
-    // of the Newton-Raphson step is truncating at every step, this adjustment
-    // is small; most of the work is already done.
-    reciprocal -= 2;
-    
-    // The numerical reciprocal is accurate to within 2^-56, lies in the
-    // interval [0.5, 1.0), and is strictly smaller than the true reciprocal
-    // of b.  Multiplying a by this reciprocal thus gives a numerical q = a/b
-    // in Q53 with the following properties:
-    //
-    //    1. q < a/b
-    //    2. q is in the interval [0.5, 2.0)
-    //    3. the error in q is bounded away from 2^-53 (actually, we have a
-    //       couple of bits to spare, but this is all we need).
-    
-    // We need a 64 x 64 multiply high to compute q, which isn't a basic
-    // operation in C, so we need to be a little bit fussy.
-    rep_t quotient, quotientLo;
-    wideMultiply(aSignificand << 2, reciprocal, &quotient, &quotientLo);
-    
-    // Two cases: quotient is in [0.5, 1.0) or quotient is in [1.0, 2.0).
-    // In either case, we are going to compute a residual of the form
-    //
-    //     r = a - q*b
-    //
-    // We know from the construction of q that r satisfies:
-    //
-    //     0 <= r < ulp(q)*b
-    // 
-    // if r is greater than 1/2 ulp(q)*b, then q rounds up.  Otherwise, we
-    // already have the correct result.  The exact halfway case cannot occur.
-    // We also take this time to right shift quotient if it falls in the [1,2)
-    // range and adjust the exponent accordingly.
-    rep_t residual;
-    if (quotient < (implicitBit << 1)) {
-        residual = (aSignificand << 53) - quotient * bSignificand;
-        quotientExponent--;
-    } else {
-        quotient >>= 1;
-        residual = (aSignificand << 52) - quotient * bSignificand;
-    }
-    
-    const int writtenExponent = quotientExponent + exponentBias;
-    
-    if (writtenExponent >= maxExponent) {
-        // If we have overflowed the exponent, return infinity.
-        return fromRep(infRep | quotientSign);
-    }
-    
-    else if (writtenExponent < 1) {
-        // Flush denormals to zero.  In the future, it would be nice to add
-        // code to round them correctly.
-        return fromRep(quotientSign);
-    }
-    
-    else {
-        const bool round = (residual << 1) > bSignificand;
-        // Clear the implicit bit
-        rep_t absResult = quotient & significandMask;
-        // Insert the exponent
-        absResult |= (rep_t)writtenExponent << significandBits;
-        // Round
-        absResult += round;
-        // Insert the sign and return
-        const double result = fromRep(absResult | quotientSign);
-        return result;
-    }
-}
+#if defined(__ARM_EABI__)
+#if defined(COMPILER_RT_ARMHF_TARGET)
+AEABI_RTABI fp_t __aeabi_ddiv(fp_t a, fp_t b) { return __divdf3(a, b); }
+#else
+COMPILER_RT_ALIAS(__divdf3, __aeabi_ddiv)
+#endif
+#endif