| 1 | //===-- lib/builtins/ppc/floattitf.c - Convert int128->long double -*-C -*-===// |
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| 2 | // |
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| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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| 4 | // See https://llvm.org/LICENSE.txt for license information. |
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| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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| 6 | // |
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| 7 | //===----------------------------------------------------------------------===// |
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| 8 | // |
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| 9 | // This file implements converting a signed 128 bit integer to a 128bit IBM / |
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| 10 | // PowerPC long double (double-double) value. |
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| 11 | // |
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| 12 | //===----------------------------------------------------------------------===// |
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| 13 | |
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| 14 | #include <stdint.h> |
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| 15 | |
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| 16 | // Conversions from signed and unsigned 64-bit int to long double. |
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| 17 | long double __floatditf(int64_t); |
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| 18 | long double __floatunditf(uint64_t); |
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| 19 | |
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| 20 | // Convert a signed 128-bit integer to long double. |
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| 21 | // This uses the following property: Let hi and lo be 64-bits each, |
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| 22 | // and let signed_val_k() and unsigned_val_k() be the value of the |
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| 23 | // argument interpreted as a signed or unsigned k-bit integer. Then, |
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| 24 | // |
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| 25 | // signed_val_128(hi,lo) = signed_val_64(hi) * 2^64 + unsigned_val_64(lo) |
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| 26 | // = (long double)hi * 2^64 + (long double)lo, |
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| 27 | // |
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| 28 | // where (long double)hi and (long double)lo are signed and |
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| 29 | // unsigned 64-bit integer to long double conversions, respectively. |
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| 30 | long double __floattitf(__int128_t arg) { |
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| 31 | // Split the int128 argument into 64-bit high and low int64 parts. |
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| 32 | int64_t ArgHiPart = (int64_t)(arg >> 64); |
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| 33 | uint64_t ArgLoPart = (uint64_t)arg; |
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| 34 | |
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| 35 | // Convert each 64-bit part into long double. The high part |
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| 36 | // must be a signed conversion and the low part an unsigned conversion |
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| 37 | // to ensure the correct result. |
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| 38 | long double ConvertedHiPart = __floatditf(ArgHiPart); |
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| 39 | long double ConvertedLoPart = __floatunditf(ArgLoPart); |
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| 40 | |
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| 41 | // The low bit of ArgHiPart corresponds to the 2^64 bit in arg. |
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| 42 | // Multiply the high part by 2^64 to undo the right shift by 64-bits |
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| 43 | // done in the splitting. Then, add to the low part to obtain the |
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| 44 | // final result. |
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| 45 | return ((ConvertedHiPart * 0x1.0p64) + ConvertedLoPart); |
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| 46 | } |
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| 47 | |
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