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c5f6ba6e71
This is to implement constexpr template based implementations for mathematical functions This also changes math.cpp to use these implementations. Also adds a fastpath for floating point trucation for values smaller than the signed 64 bit limit.
468 lines
9.2 KiB
C++
468 lines
9.2 KiB
C++
/*
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* Copyright (c) 2021, Leon Albrecht <leon2002.la@gmail.com>.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Concepts.h>
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#include <AK/StdLibExtraDetails.h>
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#include <AK/Types.h>
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namespace AK {
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template<FloatingPoint T>
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constexpr T NaN = __builtin_nan("");
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template<FloatingPoint T>
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constexpr T Pi = 3.141592653589793238462643383279502884L;
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template<FloatingPoint T>
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constexpr T E = 2.718281828459045235360287471352662498L;
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namespace Details {
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template<size_t>
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constexpr size_t product_even();
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template<>
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constexpr size_t product_even<2>() { return 2; }
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template<size_t value>
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constexpr size_t product_even() { return value * product_even<value - 2>(); }
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template<size_t>
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constexpr size_t product_odd();
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template<>
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constexpr size_t product_odd<1>() { return 1; }
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template<size_t value>
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constexpr size_t product_odd() { return value * product_odd<value - 2>(); }
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}
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#define CONSTEXPR_STATE(function, args...) \
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if (is_constant_evaluated()) { \
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if (IsSame<T, long double>) \
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return __builtin_##function##l(args); \
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if (IsSame<T, double>) \
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return __builtin_##function(args); \
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if (IsSame<T, float>) \
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return __builtin_##function##f(args); \
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}
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#define INTEGER_BUILTIN(name) \
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template<Integral T> \
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constexpr T name(T x) \
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{ \
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if constexpr (sizeof(T) == sizeof(long long)) \
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return __builtin_##name##ll(x); \
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if constexpr (sizeof(T) == sizeof(long)) \
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return __builtin_##name##l(x); \
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return __builtin_##name(x); \
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}
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INTEGER_BUILTIN(clz);
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INTEGER_BUILTIN(ctz);
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INTEGER_BUILTIN(popcnt);
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namespace Division {
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template<FloatingPoint T>
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constexpr T fmod(T x, T y)
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{
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CONSTEXPR_STATE(fmod, x, y);
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T res;
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asm(
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"fprem"
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: "=t"(res)
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: "0"(x), "u"(y));
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return res;
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}
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template<FloatingPoint T>
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constexpr T remainder(T x, T y)
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{
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CONSTEXPR_STATE(remainder, x, y);
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T res;
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asm(
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"fprem1"
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: "=t"(res)
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: "0"(x), "u"(y));
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return res;
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}
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}
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using Division::fmod;
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using Division::remainder;
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template<FloatingPoint T>
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constexpr T sqrt(T x)
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{
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CONSTEXPR_STATE(sqrt, x);
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T res;
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asm("fsqrt"
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: "=t"(res)
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: "0"(x));
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return res;
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}
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template<FloatingPoint T>
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constexpr T cbrt(T x)
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{
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CONSTEXPR_STATE(cbrt, x);
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if (__builtin_isinf(x) || x == 0)
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return x;
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if (x < 0)
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return -cbrt(-x);
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T r = x;
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T ex = 0;
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while (r < 0.125l) {
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r *= 8;
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ex--;
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}
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while (r > 1.0l) {
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r *= 0.125l;
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ex++;
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}
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r = (-0.46946116l * r + 1.072302l) * r + 0.3812513l;
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while (ex < 0) {
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r *= 0.5l;
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ex++;
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}
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while (ex > 0) {
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r *= 2.0l;
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ex--;
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}
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r = (2.0l / 3.0l) * r + (1.0l / 3.0l) * x / (r * r);
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r = (2.0l / 3.0l) * r + (1.0l / 3.0l) * x / (r * r);
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r = (2.0l / 3.0l) * r + (1.0l / 3.0l) * x / (r * r);
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r = (2.0l / 3.0l) * r + (1.0l / 3.0l) * x / (r * r);
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return r;
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}
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template<FloatingPoint T>
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constexpr T fabs(T x)
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{
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if (is_constant_evaluated())
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return x < 0 ? -x : x;
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asm(
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"fabs"
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: "+t"(x));
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return x;
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}
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namespace Trigonometry {
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template<FloatingPoint T>
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constexpr T hypot(T x, T y)
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{
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return sqrt(x * x + y * y);
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}
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template<FloatingPoint T>
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constexpr T sin(T angle)
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{
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CONSTEXPR_STATE(sin, angle);
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T ret;
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asm(
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"fsin"
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: "=t"(ret)
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: "0"(angle));
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return ret;
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}
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template<FloatingPoint T>
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constexpr T cos(T angle)
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{
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CONSTEXPR_STATE(cos, angle);
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T ret;
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asm(
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"fcos"
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: "=t"(ret)
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: "0"(angle));
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return ret;
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}
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template<FloatingPoint T>
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constexpr T tan(T angle)
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{
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CONSTEXPR_STATE(tan, angle);
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double ret, one;
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asm(
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"fptan"
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: "=t"(one), "=u"(ret)
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: "0"(angle));
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return ret;
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}
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template<FloatingPoint T>
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constexpr T atan(T value)
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{
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CONSTEXPR_STATE(atan, value);
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T ret;
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asm(
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"fld1\n"
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"fpatan\n"
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: "=t"(ret)
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: "0"(value));
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return ret;
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}
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template<FloatingPoint T>
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constexpr T asin(T x)
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{
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CONSTEXPR_STATE(asin, x);
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if (x > 1 || x < -1)
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return NaN<T>;
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if (x > (T)0.5 || x < (T)-0.5)
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return 2 * atan<T>(x / (1 + sqrt<T>(1 - x * x)));
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T squared = x * x;
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T value = x;
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T i = x * squared;
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value += i * Details::product_odd<1>() / Details::product_even<2>() / 3;
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i *= squared;
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value += i * Details::product_odd<3>() / Details::product_even<4>() / 5;
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i *= squared;
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value += i * Details::product_odd<5>() / Details::product_even<6>() / 7;
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i *= squared;
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value += i * Details::product_odd<7>() / Details::product_even<8>() / 9;
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i *= squared;
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value += i * Details::product_odd<9>() / Details::product_even<10>() / 11;
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i *= squared;
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value += i * Details::product_odd<11>() / Details::product_even<12>() / 13;
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i *= squared;
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value += i * Details::product_odd<13>() / Details::product_even<14>() / 15;
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i *= squared;
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value += i * Details::product_odd<15>() / Details::product_even<16>() / 17;
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return value;
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}
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template<FloatingPoint T>
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constexpr T acos(T value)
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{
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CONSTEXPR_STATE(acos, value);
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// FIXME: I am naive
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return Pi<T> + asin(value);
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}
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template<FloatingPoint T>
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constexpr T atan2(T y, T x)
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{
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CONSTEXPR_STATE(atan2, y, x);
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T ret;
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asm("fpatan"
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: "=t"(ret)
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: "0"(x), "u"(y)
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: "st(1)");
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return ret;
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}
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}
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using Trigonometry::acos;
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using Trigonometry::asin;
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using Trigonometry::atan;
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using Trigonometry::atan2;
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using Trigonometry::cos;
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using Trigonometry::hypot;
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using Trigonometry::sin;
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using Trigonometry::tan;
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namespace Exponentials {
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template<FloatingPoint T>
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constexpr T log(T x)
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{
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CONSTEXPR_STATE(log, x);
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T ret;
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asm(
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"fldln2\n"
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"fxch %%st(1)\n"
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"fyl2x\n"
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: "=t"(ret)
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: "0"(x));
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return ret;
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}
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template<FloatingPoint T>
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constexpr T log2(T x)
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{
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CONSTEXPR_STATE(log2, x);
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T ret;
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asm(
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"fld1\n"
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"fxch %%st(1)\n"
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"fyl2x\n"
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: "=t"(ret)
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: "0"(x));
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return ret;
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}
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template<Integral T>
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constexpr T log2(T x)
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{
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return x ? 8 * sizeof(T) - clz(x) : 0;
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}
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template<FloatingPoint T>
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constexpr T log10(T x)
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{
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CONSTEXPR_STATE(log10, x);
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T ret;
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asm(
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"fldlg2\n"
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"fxch %%st(1)\n"
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"fyl2x\n"
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: "=t"(ret)
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: "0"(x));
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return ret;
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}
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template<FloatingPoint T>
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constexpr T exp(T exponent)
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{
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CONSTEXPR_STATE(exp, exponent);
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T res;
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asm("fldl2e\n"
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"fmulp\n"
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"fld1\n"
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"fld %%st(1)\n"
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"fprem\n"
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"f2xm1\n"
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"faddp\n"
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"fscale\n"
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"fstp %%st(1)"
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: "=t"(res)
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: "0"(exponent));
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return res;
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}
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template<FloatingPoint T>
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constexpr T exp2(T exponent)
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{
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CONSTEXPR_STATE(exp2, exponent);
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T res;
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asm("fld1\n"
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"fld %%st(1)\n"
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"fprem\n"
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"f2xm1\n"
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"faddp\n"
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"fscale\n"
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"fstp %%st(1)"
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: "=t"(res)
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: "0"(exponent));
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return res;
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}
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template<Integral T>
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constexpr T exp2(T exponent)
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{
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return 1u << exponent;
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}
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}
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using Exponentials::exp;
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using Exponentials::exp2;
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using Exponentials::log;
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using Exponentials::log10;
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using Exponentials::log2;
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namespace Hyperbolic {
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template<FloatingPoint T>
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constexpr T sinh(T x)
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{
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T exponentiated = exp<T>(x);
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if (x > 0)
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return (exponentiated * exponentiated - 1) / 2 / exponentiated;
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return (exponentiated - 1 / exponentiated) / 2;
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}
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template<FloatingPoint T>
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constexpr T cosh(T x)
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{
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CONSTEXPR_STATE(cosh, x);
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T exponentiated = exp(-x);
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if (x < 0)
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return (1 + exponentiated * exponentiated) / 2 / exponentiated;
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return (1 / exponentiated + exponentiated) / 2;
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}
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template<FloatingPoint T>
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constexpr T tanh(T x)
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{
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if (x > 0) {
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T exponentiated = exp<T>(2 * x);
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return (exponentiated - 1) / (exponentiated + 1);
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}
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T plusX = exp<T>(x);
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T minusX = 1 / plusX;
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return (plusX - minusX) / (plusX + minusX);
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}
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template<FloatingPoint T>
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constexpr T asinh(T x)
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{
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return log<T>(x + sqrt<T>(x * x + 1));
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}
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template<FloatingPoint T>
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constexpr T acosh(T x)
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{
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return log<T>(x + sqrt<T>(x * x - 1));
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}
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template<FloatingPoint T>
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constexpr T atanh(T x)
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{
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return log<T>((1 + x) / (1 - x)) / (T)2.0l;
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}
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}
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using Hyperbolic::acosh;
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using Hyperbolic::asinh;
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using Hyperbolic::atanh;
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using Hyperbolic::cosh;
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using Hyperbolic::sinh;
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using Hyperbolic::tanh;
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template<FloatingPoint T>
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constexpr T pow(T x, T y)
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{
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CONSTEXPR_STATE(pow, x, y);
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// fixme I am naive
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if (__builtin_isnan(y))
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return y;
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if (y == 0)
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return 1;
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if (x == 0)
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return 0;
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if (y == 1)
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return x;
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int y_as_int = (int)y;
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if (y == (T)y_as_int) {
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T result = x;
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for (int i = 0; i < fabs<T>(y) - 1; ++i)
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result *= x;
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if (y < 0)
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result = 1.0l / result;
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return result;
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}
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return exp2<T>(y * log2<T>(x));
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}
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#undef CONSTEXPR_STATE
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#undef INTEGER_BUILTIN
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}
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