bbb7555403
This expands the pattern suggest in https://reviews.llvm.org/D95850 to all math functions.
65 lines
1.7 KiB
C++
65 lines
1.7 KiB
C++
//===-- Single-precision 2^x function -------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "src/math/exp2f.h"
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#include "exp_utils.h"
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#include "math_utils.h"
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#include "src/__support/common.h"
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#include <math.h>
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#include <stdint.h>
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#define T exp2f_data.tab
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#define C exp2f_data.poly
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#define SHIFT exp2f_data.shift_scaled
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namespace __llvm_libc {
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LLVM_LIBC_FUNCTION(float, exp2f, (float x)) {
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uint32_t abstop;
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uint64_t ki, t;
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// double_t for better performance on targets with FLT_EVAL_METHOD==2.
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double_t kd, xd, z, r, r2, y, s;
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xd = static_cast<double_t>(x);
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abstop = top12_bits(x) & 0x7ff;
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if (unlikely(abstop >= top12_bits(128.0f))) {
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// |x| >= 128 or x is nan.
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if (as_uint32_bits(x) == as_uint32_bits(-INFINITY))
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return 0.0f;
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if (abstop >= top12_bits(INFINITY))
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return x + x;
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if (x > 0.0f)
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return overflow<float>(0);
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if (x <= -150.0f)
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return underflow<float>(0);
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if (x < -149.0f)
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return may_underflow<float>(0);
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}
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// x = k/N + r with r in [-1/(2N), 1/(2N)] and int k.
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kd = static_cast<double>(xd + SHIFT);
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ki = as_uint64_bits(kd);
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kd -= SHIFT; // k/N for int k.
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r = xd - kd;
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// exp2(x) = 2^(k/N) * 2^r ~= s * (C0*r^3 + C1*r^2 + C2*r + 1)
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t = T[ki % N];
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t += ki << (52 - EXP2F_TABLE_BITS);
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s = as_double(t);
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z = C[0] * r + C[1];
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r2 = r * r;
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y = C[2] * r + 1;
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y = z * r2 + y;
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y = y * s;
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return static_cast<float>(y);
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}
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} // namespace __llvm_libc
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