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0cf277c710
std::__clz is a libc++ specific function so it can't be used in the test suite. This patch implements a dumb "count leading zeros" implementation within hexfloat itself. This patch also fixes UB since the output of `__builtin_clz(0)` is undefined according to the GCC docs. git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@268354 91177308-0d34-0410-b5e6-96231b3b80d8
51 lines
1.4 KiB
C++
51 lines
1.4 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is dual licensed under the MIT and the University of Illinois Open
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// Source Licenses. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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// Define a hexfloat literal emulator since we can't depend on being able to
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// for hexfloat literals
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// 0x10.F5p-10 == hexfloat<double>(0x10, 0xF5, -10)
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#ifndef HEXFLOAT_H
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#define HEXFLOAT_H
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#include <cmath>
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#include <climits>
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template <class T>
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class hexfloat
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{
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T value_;
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static int CountLeadingZeros(unsigned long long n) {
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const std::size_t Digits = sizeof(unsigned long long) * CHAR_BIT;
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const unsigned long long TopBit = 1ull << (Digits - 1);
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if (n == 0) return Digits;
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int LeadingZeros = 0;
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while ((n & TopBit) == 0) {
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++LeadingZeros;
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n <<= 1;
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}
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return LeadingZeros;
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}
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public:
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hexfloat(long long m1, unsigned long long m0, int exp)
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{
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const std::size_t Digits = sizeof(unsigned long long) * CHAR_BIT;
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int s = m1 < 0 ? -1 : 1;
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int exp2 = -static_cast<int>(Digits - CountLeadingZeros(m0)/4*4);
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value_ = std::ldexp(m1 + s * std::ldexp(T(m0), exp2), exp);
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}
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operator T() const {return value_;}
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};
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#endif
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