// 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 // int64_t __fixunstfdi(long double x); // This file implements the PowerPC 128-bit double-double -> int64_t conversion #include "../int_math.h" #include "DD.h" uint64_t __fixtfdi(long double input) { const DD x = {.ld = input}; const doublebits hibits = {.d = x.s.hi}; const uint32_t absHighWord = (uint32_t)(hibits.x >> 32) & UINT32_C(0x7fffffff); const uint32_t absHighWordMinusOne = absHighWord - UINT32_C(0x3ff00000); // If (1.0 - tiny) <= input < 0x1.0p63: if (UINT32_C(0x03f00000) > absHighWordMinusOne) { // Do an unsigned conversion of the absolute value, then restore the sign. const int unbiasedHeadExponent = absHighWordMinusOne >> 20; int64_t result = hibits.x & INT64_C(0x000fffffffffffff); // mantissa(hi) result |= INT64_C(0x0010000000000000); // matissa(hi) with implicit bit result <<= 10; // mantissa(hi) with one zero preceding bit. const int64_t hiNegationMask = ((int64_t)(hibits.x)) >> 63; // If the tail is non-zero, we need to patch in the tail bits. if (0.0 != x.s.lo) { const doublebits lobits = {.d = x.s.lo}; int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff); tailMantissa |= INT64_C(0x0010000000000000); // At this point we have the mantissa of |tail| // We need to negate it if head and tail have different signs. const int64_t loNegationMask = ((int64_t)(lobits.x)) >> 63; const int64_t negationMask = loNegationMask ^ hiNegationMask; tailMantissa = (tailMantissa ^ negationMask) - negationMask; // Now we have the mantissa of tail as a signed 2s-complement integer const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff; // Shift the tail mantissa into the right position, accounting for the // bias of 10 that we shifted the head mantissa by. tailMantissa >>= (unbiasedHeadExponent - (biasedTailExponent - (1023 - 10))); result += tailMantissa; } result >>= (62 - unbiasedHeadExponent); // Restore the sign of the result and return result = (result ^ hiNegationMask) - hiNegationMask; return result; } // Edge cases handled here: // |x| < 1, result is zero. if (1.0 > crt_fabs(x.s.hi)) return INT64_C(0); // x very close to INT64_MIN, care must be taken to see which side we are on. if (x.s.hi == -0x1.0p63) { int64_t result = INT64_MIN; if (0.0 < x.s.lo) { // If the tail is positive, the correct result is something other than // INT64_MIN. we'll need to figure out what it is. const doublebits lobits = {.d = x.s.lo}; int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff); tailMantissa |= INT64_C(0x0010000000000000); // Now we negate the tailMantissa tailMantissa = (tailMantissa ^ INT64_C(-1)) + INT64_C(1); // And shift it by the appropriate amount const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff; tailMantissa >>= 1075 - biasedTailExponent; result -= tailMantissa; } return result; } // Signed overflows, infinities, and NaNs if (x.s.hi > 0.0) return INT64_MAX; else return INT64_MIN; } |