| 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-exception |
| 4 | |
| 5 | // int64_t __fixunstfdi(long double x); |
| 6 | // This file implements the PowerPC 128-bit double-double -> int64_t conversion |
| 7 | |
| 8 | #include "../int_math.h" |
| 9 | #include "DD.h" |
| 10 | |
| 11 | uint64_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 bit |
| 26 | 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 integer |
| 43 | |
| 44 | const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff; |
| 45 | |
| 46 | // Shift the tail mantissa into the right position, accounting for the |
| 47 | // 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 return |
| 57 | 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 than |
| 74 | // 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 tailMantissa |
| 81 | tailMantissa = (tailMantissa ^ INT64_C(-1)) + INT64_C(1); |
| 82 | |
| 83 | // And shift it by the appropriate amount |
| 84 | 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 NaNs |
| 94 | if (x.s.hi > 0.0) |
| 95 | return INT64_MAX; |
| 96 | else |
| 97 | return INT64_MIN; |
| 98 | } |
| 99 |