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1// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.2// See https://llvm.org/LICENSE.txt for license information.3// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception4 5// int64_t __fixunstfdi(long double x);6// This file implements the PowerPC 128-bit double-double -> int64_t conversion7 8#include "../int_math.h"9#include "DD.h"10 11uint64_t __fixtfdi(long double input) {12 const DD x = {.ld = input};13 const doublebits hibits = {.d = x.s.hi};14 15 const uint32_t absHighWord =16 (uint32_t)(hibits.x >> 32) & UINT32_C(0x7fffffff);17 const uint32_t absHighWordMinusOne = absHighWord - UINT32_C(0x3ff00000);18 19 // If (1.0 - tiny) <= input < 0x1.0p63:20 if (UINT32_C(0x03f00000) > absHighWordMinusOne) {21 // Do an unsigned conversion of the absolute value, then restore the sign.22 const int unbiasedHeadExponent = absHighWordMinusOne >> 20;23 24 int64_t result = hibits.x & INT64_C(0x000fffffffffffff); // mantissa(hi)25 result |= INT64_C(0x0010000000000000); // matissa(hi) with implicit bit26 result <<= 10; // mantissa(hi) with one zero preceding bit.27 28 const int64_t hiNegationMask = ((int64_t)(hibits.x)) >> 63;29 30 // If the tail is non-zero, we need to patch in the tail bits.31 if (0.0 != x.s.lo) {32 const doublebits lobits = {.d = x.s.lo};33 int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff);34 tailMantissa |= INT64_C(0x0010000000000000);35 36 // At this point we have the mantissa of |tail|37 // We need to negate it if head and tail have different signs.38 const int64_t loNegationMask = ((int64_t)(lobits.x)) >> 63;39 const int64_t negationMask = loNegationMask ^ hiNegationMask;40 tailMantissa = (tailMantissa ^ negationMask) - negationMask;41 42 // Now we have the mantissa of tail as a signed 2s-complement integer43 44 const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff;45 46 // Shift the tail mantissa into the right position, accounting for the47 // bias of 10 that we shifted the head mantissa by.48 tailMantissa >>=49 (unbiasedHeadExponent - (biasedTailExponent - (1023 - 10)));50 51 result += tailMantissa;52 }53 54 result >>= (62 - unbiasedHeadExponent);55 56 // Restore the sign of the result and return57 result = (result ^ hiNegationMask) - hiNegationMask;58 return result;59 }60 61 // Edge cases handled here:62 63 // |x| < 1, result is zero.64 if (1.0 > crt_fabs(x.s.hi))65 return INT64_C(0);66 67 // x very close to INT64_MIN, care must be taken to see which side we are on.68 if (x.s.hi == -0x1.0p63) {69 70 int64_t result = INT64_MIN;71 72 if (0.0 < x.s.lo) {73 // If the tail is positive, the correct result is something other than74 // INT64_MIN. we'll need to figure out what it is.75 76 const doublebits lobits = {.d = x.s.lo};77 int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff);78 tailMantissa |= INT64_C(0x0010000000000000);79 80 // Now we negate the tailMantissa81 tailMantissa = (tailMantissa ^ INT64_C(-1)) + INT64_C(1);82 83 // And shift it by the appropriate amount84 const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff;85 tailMantissa >>= 1075 - biasedTailExponent;86 87 result -= tailMantissa;88 }89 90 return result;91 }92 93 // Signed overflows, infinities, and NaNs94 if (x.s.hi > 0.0)95 return INT64_MAX;96 else97 return INT64_MIN;98}99