fdf20941a8
Add tests for signaling NaNs, and fix function behavior for handling signaling NaN input. Fixes https://github.com/llvm/llvm-project/issues/124812
118 lines
3.9 KiB
C++
118 lines
3.9 KiB
C++
//===-- Single-precision sinpif 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/sinpif.h"
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#include "sincosf_utils.h"
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#include "src/__support/FPUtil/FEnvImpl.h"
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#include "src/__support/FPUtil/FPBits.h"
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#include "src/__support/FPUtil/PolyEval.h"
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#include "src/__support/FPUtil/multiply_add.h"
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#include "src/__support/common.h"
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#include "src/__support/macros/config.h"
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#include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
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namespace LIBC_NAMESPACE_DECL {
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LLVM_LIBC_FUNCTION(float, sinpif, (float x)) {
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using FPBits = typename fputil::FPBits<float>;
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FPBits xbits(x);
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uint32_t x_u = xbits.uintval();
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uint32_t x_abs = x_u & 0x7fff'ffffU;
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double xd = static_cast<double>(x);
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// Range reduction:
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// For |x| > 1/32, we perform range reduction as follows:
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// Find k and y such that:
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// x = (k + y) * 1/32
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// k is an integer
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// |y| < 0.5
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//
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// This is done by performing:
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// k = round(x * 32)
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// y = x * 32 - k
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//
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// Once k and y are computed, we then deduce the answer by the sine of sum
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// formula:
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// sin(x * pi) = sin((k + y)*pi/32)
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// = sin(y*pi/32) * cos(k*pi/32) + cos(y*pi/32) * sin(k*pi/32)
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// The values of sin(k*pi/32) and cos(k*pi/32) for k = 0..31 are precomputed
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// and stored using a vector of 32 doubles. Sin(y*pi/32) and cos(y*pi/32) are
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// computed using degree-7 and degree-6 minimax polynomials generated by
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// Sollya respectively.
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// |x| <= 1/16
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if (LIBC_UNLIKELY(x_abs <= 0x3d80'0000U)) {
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if (LIBC_UNLIKELY(x_abs < 0x33CD'01D7U)) {
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if (LIBC_UNLIKELY(x_abs == 0U)) {
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// For signed zeros.
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return x;
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}
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// For very small values we can approximate sinpi(x) with x * pi
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// An exhaustive test shows that this is accurate for |x| < 9.546391 ×
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// 10-8
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double xdpi = xd * 0x1.921fb54442d18p1;
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return static_cast<float>(xdpi);
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}
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// |x| < 1/16.
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double xsq = xd * xd;
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// Degree-9 polynomial approximation:
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// sinpi(x) ~ x + a_3 x^3 + a_5 x^5 + a_7 x^7 + a_9 x^9
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// = x (1 + a_3 x^2 + ... + a_9 x^8)
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// = x * P(x^2)
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// generated by Sollya with the following commands:
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// > display = hexadecimal;
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// > Q = fpminimax(sin(pi * x)/x, [|0, 2, 4, 6, 8|], [|D...|], [0, 1/16]);
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double result = fputil::polyeval(
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xsq, 0x1.921fb54442d18p1, -0x1.4abbce625bbf2p2, 0x1.466bc675e116ap1,
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-0x1.32d2c0b62d41cp-1, 0x1.501ec4497cb7dp-4);
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return static_cast<float>(xd * result);
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}
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// Numbers greater or equal to 2^23 are always integers or NaN
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if (LIBC_UNLIKELY(x_abs >= 0x4B00'0000)) {
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// check for NaN values
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if (LIBC_UNLIKELY(x_abs >= 0x7f80'0000U)) {
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if (xbits.is_signaling_nan()) {
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fputil::raise_except_if_required(FE_INVALID);
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return FPBits::quiet_nan().get_val();
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}
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if (x_abs == 0x7f80'0000U) {
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fputil::set_errno_if_required(EDOM);
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fputil::raise_except_if_required(FE_INVALID);
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}
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return x + FPBits::quiet_nan().get_val();
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}
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return FPBits::zero(xbits.sign()).get_val();
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}
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// Combine the results with the sine of sum formula:
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// sin(x * pi) = sin((k + y)*pi/32)
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// = sin(y*pi/32) * cos(k*pi/32) + cos(y*pi/32) * sin(k*pi/32)
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// = sin_y * cos_k + (1 + cosm1_y) * sin_k
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// = sin_y * cos_k + (cosm1_y * sin_k + sin_k)
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double sin_k, cos_k, sin_y, cosm1_y;
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sincospif_eval(xd, sin_k, cos_k, sin_y, cosm1_y);
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if (LIBC_UNLIKELY(sin_y == 0 && sin_k == 0))
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return FPBits::zero(xbits.sign()).get_val();
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return static_cast<float>(fputil::multiply_add(
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sin_y, cos_k, fputil::multiply_add(cosm1_y, sin_k, sin_k)));
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}
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} // namespace LIBC_NAMESPACE_DECL
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