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// 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
// uint64_t __fixunstfdi(long double x);
// This file implements the PowerPC 128-bit double-double -> uint64_t conversion
#include "DD.h"
uint64_t __fixunstfdi(long double input) {
const DD x = {.ld = input};
const doublebits hibits = {.d = x.s.hi};
const uint32_t highWordMinusOne =
(uint32_t)(hibits.x >> 32) - UINT32_C(0x3ff00000);
// If (1.0 - tiny) <= input < 0x1.0p64:
if (UINT32_C(0x04000000) > highWordMinusOne) {
const int unbiasedHeadExponent = highWordMinusOne >> 20;
uint64_t result = hibits.x & UINT64_C(0x000fffffffffffff); // mantissa(hi)
result |= UINT64_C(0x0010000000000000); // matissa(hi) with implicit bit
result <<= 11; // mantissa(hi) left aligned in the int64 field.
// 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|
const int64_t negationMask = ((int64_t)(lobits.x)) >> 63;
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 11 that we shifted the head mantissa by.
tailMantissa >>=
(unbiasedHeadExponent - (biasedTailExponent - (1023 - 11)));
result += tailMantissa;
}
result >>= (63 - unbiasedHeadExponent);
return result;
}
// Edge cases are handled here, with saturation.
if (1.0 > x.s.hi)
return UINT64_C(0);
else
return UINT64_MAX;
}
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