[libc-commits] [libc] [libc][math][c23] Add exp2m1f C23 math function (PR #86996)
via libc-commits
libc-commits at lists.llvm.org
Thu Mar 28 12:41:21 PDT 2024
https://github.com/overmighty created https://github.com/llvm/llvm-project/pull/86996
Fixes #86502.
cc @lntue
>From 601fabe46dd13bb4e2a3b93f723b45632f45c838 Mon Sep 17 00:00:00 2001
From: OverMighty <its.overmighty at gmail.com>
Date: Thu, 28 Mar 2024 19:36:38 +0000
Subject: [PATCH] [libc][math][c23] Add exp2m1f C23 math function
Fixes #86502.
---
libc/config/linux/x86_64/entrypoints.txt | 1 +
libc/spec/stdc.td | 2 +
libc/src/math/CMakeLists.txt | 2 +
libc/src/math/exp2m1f.h | 18 +++
libc/src/math/generic/CMakeLists.txt | 21 +++
libc/src/math/generic/exp2m1f.cpp | 144 ++++++++++++++++++
libc/test/src/math/exhaustive/CMakeLists.txt | 15 ++
.../test/src/math/exhaustive/exp2m1f_test.cpp | 33 ++++
libc/test/src/math/smoke/CMakeLists.txt | 12 ++
libc/test/src/math/smoke/exp2m1f_test.cpp | 57 +++++++
libc/utils/MPFRWrapper/MPFRUtils.cpp | 8 +
libc/utils/MPFRWrapper/MPFRUtils.h | 1 +
12 files changed, 314 insertions(+)
create mode 100644 libc/src/math/exp2m1f.h
create mode 100644 libc/src/math/generic/exp2m1f.cpp
create mode 100644 libc/test/src/math/exhaustive/exp2m1f_test.cpp
create mode 100644 libc/test/src/math/smoke/exp2m1f_test.cpp
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 5b428e51aee620..b1e0592278e18c 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -369,6 +369,7 @@ set(TARGET_LIBM_ENTRYPOINTS
libc.src.math.exp10f
libc.src.math.exp2
libc.src.math.exp2f
+ libc.src.math.exp2m1f
libc.src.math.expm1
libc.src.math.expm1f
libc.src.math.fabs
diff --git a/libc/spec/stdc.td b/libc/spec/stdc.td
index ac6e1d1801ba55..bd72ff9095e2ea 100644
--- a/libc/spec/stdc.td
+++ b/libc/spec/stdc.td
@@ -535,6 +535,8 @@ def StdC : StandardSpec<"stdc"> {
FunctionSpec<"exp2", RetValSpec<DoubleType>, [ArgSpec<DoubleType>]>,
FunctionSpec<"exp2f", RetValSpec<FloatType>, [ArgSpec<FloatType>]>,
+ FunctionSpec<"exp2m1f", RetValSpec<FloatType>, [ArgSpec<FloatType>]>,
+
FunctionSpec<"expm1", RetValSpec<DoubleType>, [ArgSpec<DoubleType>]>,
FunctionSpec<"expm1f", RetValSpec<FloatType>, [ArgSpec<FloatType>]>,
diff --git a/libc/src/math/CMakeLists.txt b/libc/src/math/CMakeLists.txt
index b67ee3a8e0dfbd..c89792b8ac7be6 100644
--- a/libc/src/math/CMakeLists.txt
+++ b/libc/src/math/CMakeLists.txt
@@ -88,6 +88,8 @@ add_math_entrypoint_object(expf)
add_math_entrypoint_object(exp2)
add_math_entrypoint_object(exp2f)
+add_math_entrypoint_object(exp2m1f)
+
add_math_entrypoint_object(exp10)
add_math_entrypoint_object(exp10f)
diff --git a/libc/src/math/exp2m1f.h b/libc/src/math/exp2m1f.h
new file mode 100644
index 00000000000000..0eaf6b00e958c5
--- /dev/null
+++ b/libc/src/math/exp2m1f.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for exp2m1f -----------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_MATH_EXP2M1F_H
+#define LLVM_LIBC_SRC_MATH_EXP2M1F_H
+
+namespace LIBC_NAMESPACE {
+
+float exp2m1f(float x);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_MATH_EXP2M1F_H
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index 4d9b91150d0200..c1a4e5ea6e3b9d 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -837,6 +837,27 @@ add_entrypoint_object(
-O3
)
+add_entrypoint_object(
+ exp2m1f
+ SRCS
+ exp2m1f.cpp
+ HDRS
+ ../exp2m1f.h
+ DEPENDS
+ .explogxf
+ libc.src.errno.errno
+ libc.src.__support.common
+ libc.src.__support.FPUtil.fenv_impl
+ libc.src.__support.FPUtil.fp_bits
+ libc.src.__support.FPUtil.multiply_add
+ libc.src.__support.FPUtil.polyeval
+ libc.src.__support.FPUtil.rounding_mode
+ libc.src.__support.macros.optimization
+ libc.src.__support.macros.properties.cpu_features
+ COMPILE_OPTIONS
+ -O3
+)
+
add_entrypoint_object(
exp10
SRCS
diff --git a/libc/src/math/generic/exp2m1f.cpp b/libc/src/math/generic/exp2m1f.cpp
new file mode 100644
index 00000000000000..ea5c637b0b8692
--- /dev/null
+++ b/libc/src/math/generic/exp2m1f.cpp
@@ -0,0 +1,144 @@
+//===-- Implementation of exp2m1f function --------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/math/exp2m1f.h"
+#include "src/__support/FPUtil/FEnvImpl.h"
+#include "src/__support/FPUtil/FPBits.h"
+#include "src/__support/FPUtil/PolyEval.h"
+#include "src/__support/FPUtil/multiply_add.h"
+#include "src/__support/FPUtil/rounding_mode.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/optimization.h"
+#include "src/__support/macros/properties/cpu_features.h"
+#include "src/errno/libc_errno.h"
+
+#include "explogxf.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(float, exp2m1f, (float x)) {
+ using FPBits = fputil::FPBits<float>;
+ FPBits xbits(x);
+
+ uint32_t x_u = xbits.uintval();
+ uint32_t x_abs = x_u & 0x7fff'ffffU;
+
+ // When |x| >= 128, or x is nan, or |x| <= 2^-5
+ if (LIBC_UNLIKELY(x_abs >= 0x4300'0000U || x_abs <= 0x3d00'0000U)) {
+ // |x| <= 2^-5
+ if (x_abs <= 0x3d00'0000) {
+ // TODO: Handle exceptional values.
+
+ // Minimax polynomial generated by Sollya with:
+ // > display = hexadecimal;
+ // > fpminimax((2^x - 1)/x, 5, [|D...|], [-2^-5, 2^-5]);
+ constexpr double COEFFS[] = {
+ 0x1.62e42fefa39f3p-1, 0x1.ebfbdff82c57bp-3, 0x1.c6b08d6f2d7aap-5,
+ 0x1.3b2ab6fc92f5dp-7, 0x1.5d897cfe27125p-10, 0x1.43090e61e6af1p-13};
+ double xd = x;
+ double xsq = xd * xd;
+ double c0 = fputil::multiply_add(xd, COEFFS[1], COEFFS[0]);
+ double c1 = fputil::multiply_add(xd, COEFFS[3], COEFFS[2]);
+ double c2 = fputil::multiply_add(xd, COEFFS[5], COEFFS[4]);
+ double p = fputil::polyeval(xsq, c0, c1, c2);
+ return static_cast<float>(p * xd);
+ }
+
+ // x >= 128, or x is nan
+ if (xbits.is_pos()) {
+ if (xbits.is_finite()) {
+ int rounding = fputil::quick_get_round();
+ if (rounding == FE_DOWNWARD || rounding == FE_TOWARDZERO)
+ return FPBits::max_normal().get_val();
+
+ fputil::set_errno_if_required(ERANGE);
+ fputil::raise_except_if_required(FE_OVERFLOW);
+ }
+
+ // x >= 128 and 2^x - 1 rounds to +inf, or x is +inf or nan
+ return x + FPBits::inf().get_val();
+ }
+
+ // x <= -25
+ if (x <= -25.0f) {
+ // 2^(-inf) - 1 = -1
+ if (xbits.is_inf())
+ return -1.0f;
+ // 2^nan - 1 = nan
+ if (xbits.is_nan())
+ return x;
+
+ int rounding = fputil::quick_get_round();
+ if (rounding == FE_UPWARD || rounding == FE_TOWARDZERO)
+ return -0x1.ffff'fep-1f; // -1.0f + 0x1.0p-24f
+
+ fputil::set_errno_if_required(ERANGE);
+ fputil::raise_except_if_required(FE_UNDERFLOW);
+ return -1.0f;
+ }
+ }
+
+ // For -25 < x < 128, to compute 2^x, we perform the following range
+ // reduction: find hi, mid, lo such that:
+ // x = hi + mid + lo, in which:
+ // hi is an integer,
+ // 0 <= mid * 2^5 < 32 is an integer,
+ // -2^(-6) <= lo <= 2^(-6).
+ // In particular,
+ // hi + mid = round(x * 2^5) * 2^(-5).
+ // Then,
+ // 2^x = 2^(hi + mid + lo) = 2^hi * 2^mid * 2^lo.
+ // 2^mid is stored in the lookup table of 32 elements.
+ // 2^lo is computed using a degree-4 minimax polynomial generated by Sollya.
+ // We perform 2^hi * 2^mid by simply add hi to the exponent field of 2^mid.
+
+ // kf = (hi + mid) * 2^5 = round(x * 2^5)
+ float kf;
+ int k;
+#ifdef LIBC_TARGET_CPU_HAS_NEAREST_INT
+ kf = fputil::nearest_integer(x * 32.0f);
+ k = static_cast<int>(kf);
+#else
+ constexpr float HALF[2] = {0.5f, -0.5f};
+ k = static_cast<int>(fputil::multiply_add(x, 32.0f, HALF[x < 0.0f]));
+ kf = static_cast<float>(k);
+#endif // LIBC_TARGET_CPU_HAS_NEAREST_INT
+
+ // dx = lo = x - (hi + mid) = x - kf * 2^(-5)
+ double dx = fputil::multiply_add(-0x1.0p-5f, kf, x);
+
+ // hi = floor(kf * 2^(-4))
+ // exp_hi = shift hi to the exponent field of double precision.
+ int64_t exp_hi =
+ static_cast<int64_t>(static_cast<uint64_t>(k >> ExpBase::MID_BITS)
+ << fputil::FPBits<double>::FRACTION_LEN);
+ // mh = 2^hi * 2^mid
+ // mh_bits = bit field of mh
+ int64_t mh_bits = ExpBase::EXP_2_MID[k & ExpBase::MID_MASK] + exp_hi;
+ double mh = fputil::FPBits<double>(static_cast<uint64_t>(mh_bits)).get_val();
+
+ // Degree-4 polynomial approximating (2^x - 1)/x generated by Sollya with:
+ // > display = hexadecimal;
+ // > fpminimax((2^x - 1)/x, 4, [|D...|], [-2^-6, 2^-6]);
+ constexpr double COEFFS[5] = {0x1.62e42fefa39efp-1, 0x1.ebfbdff8131c4p-3,
+ 0x1.c6b08d7061695p-5, 0x1.3b2b1bee74b2ap-7,
+ 0x1.5d88091198529p-10};
+ double dx_sq = dx * dx;
+ double c1 = fputil::multiply_add(dx, COEFFS[0], 1.0);
+ double c2 = fputil::multiply_add(dx, COEFFS[2], COEFFS[1]);
+ double c3 = fputil::multiply_add(dx, COEFFS[4], COEFFS[3]);
+ double p = fputil::multiply_add(dx_sq, c3, c2);
+ // 2^x = 2^(hi + mid + lo)
+ // = 2^(hi + mid) * 2^lo
+ // ~ mh * (1 + lo * P(lo))
+ // = mh + (mh*lo) * P(lo)
+ double exp2_lo = fputil::multiply_add(p, dx_sq, c1);
+ return static_cast<float>(fputil::multiply_add(exp2_lo, mh, -1.0));
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/test/src/math/exhaustive/CMakeLists.txt b/libc/test/src/math/exhaustive/CMakeLists.txt
index df32dd4f943f30..6b2f3dddcadd24 100644
--- a/libc/test/src/math/exhaustive/CMakeLists.txt
+++ b/libc/test/src/math/exhaustive/CMakeLists.txt
@@ -142,6 +142,21 @@ add_fp_unittest(
-lpthread
)
+add_fp_unittest(
+ exp2m1f_test
+ NO_RUN_POSTBUILD
+ NEED_MPFR
+ SUITE
+ libc_math_exhaustive_tests
+ SRCS
+ exp2m1f_test.cpp
+ DEPENDS
+ .exhaustive_test
+ libc.src.math.exp2m1f
+ LINK_LIBRARIES
+ -lpthread
+)
+
add_fp_unittest(
exp10f_test
NO_RUN_POSTBUILD
diff --git a/libc/test/src/math/exhaustive/exp2m1f_test.cpp b/libc/test/src/math/exhaustive/exp2m1f_test.cpp
new file mode 100644
index 00000000000000..2111024cb5c03b
--- /dev/null
+++ b/libc/test/src/math/exhaustive/exp2m1f_test.cpp
@@ -0,0 +1,33 @@
+//===-- Exhaustive test for exp2m1f ---------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "exhaustive_test.h"
+#include "src/math/exp2m1f.h"
+#include "utils/MPFRWrapper/MPFRUtils.h"
+
+namespace mpfr = LIBC_NAMESPACE::testing::mpfr;
+
+using LlvmLibcExp2m1fExhaustiveTest =
+ LlvmLibcUnaryOpExhaustiveMathTest<float, mpfr::Operation::Exp2m1,
+ LIBC_NAMESPACE::exp2m1f>;
+
+// Range: [0, Inf];
+static constexpr uint32_t POS_START = 0x0000'0000U;
+static constexpr uint32_t POS_STOP = 0x7f80'0000U;
+
+TEST_F(LlvmLibcExp2m1fExhaustiveTest, PostiveRange) {
+ test_full_range_all_roundings(POS_START, POS_STOP);
+}
+
+// Range: [-Inf, 0];
+static constexpr uint32_t NEG_START = 0x8000'0000U;
+static constexpr uint32_t NEG_STOP = 0xff80'0000U;
+
+TEST_F(LlvmLibcExp2m1fExhaustiveTest, NegativeRange) {
+ test_full_range_all_roundings(NEG_START, NEG_STOP);
+}
diff --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
index 3b756127fe21ea..d07927f5d5e4bf 100644
--- a/libc/test/src/math/smoke/CMakeLists.txt
+++ b/libc/test/src/math/smoke/CMakeLists.txt
@@ -769,6 +769,18 @@ add_fp_unittest(
libc.src.__support.FPUtil.fp_bits
)
+add_fp_unittest(
+ exp2m1f_test
+ SUITE
+ libc-math-smoke-tests
+ SRCS
+ exp2m1f_test.cpp
+ DEPENDS
+ libc.src.__support.FPUtil.fp_bits
+ libc.src.errno.errno
+ libc.src.math.exp2m1f
+)
+
add_fp_unittest(
exp10f_test
SUITE
diff --git a/libc/test/src/math/smoke/exp2m1f_test.cpp b/libc/test/src/math/smoke/exp2m1f_test.cpp
new file mode 100644
index 00000000000000..1db865b91a0c26
--- /dev/null
+++ b/libc/test/src/math/smoke/exp2m1f_test.cpp
@@ -0,0 +1,57 @@
+//===-- Unittests for exp2m1f ---------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/FPUtil/FPBits.h"
+#include "src/errno/libc_errno.h"
+#include "src/math/exp2m1f.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/Test.h"
+
+using LlvmLibcExp2m1fTest = LIBC_NAMESPACE::testing::FPTest<float>;
+
+TEST_F(LlvmLibcExp2m1fTest, SpecialNumbers) {
+ LIBC_NAMESPACE::libc_errno = 0;
+
+ EXPECT_FP_EQ_ALL_ROUNDING(aNaN, LIBC_NAMESPACE::exp2m1f(aNaN));
+ EXPECT_MATH_ERRNO(0);
+
+ EXPECT_FP_EQ_ALL_ROUNDING(inf, LIBC_NAMESPACE::exp2m1f(inf));
+ EXPECT_MATH_ERRNO(0);
+
+ EXPECT_FP_EQ_ALL_ROUNDING(-1.0f, LIBC_NAMESPACE::exp2m1f(neg_inf));
+ EXPECT_MATH_ERRNO(0);
+
+ EXPECT_FP_EQ_ALL_ROUNDING(0.0f, LIBC_NAMESPACE::exp2m1f(0.0f));
+ EXPECT_MATH_ERRNO(0);
+
+ EXPECT_FP_EQ_ALL_ROUNDING(-0.0f, LIBC_NAMESPACE::exp2m1f(-0.0f));
+ EXPECT_MATH_ERRNO(0);
+
+ EXPECT_FP_EQ_ALL_ROUNDING(1.0f, LIBC_NAMESPACE::exp2m1f(1.0f));
+ EXPECT_FP_EQ_ALL_ROUNDING(-0.5f, LIBC_NAMESPACE::exp2m1f(-1.0f));
+ EXPECT_FP_EQ_ALL_ROUNDING(3.0f, LIBC_NAMESPACE::exp2m1f(2.0f));
+ EXPECT_FP_EQ_ALL_ROUNDING(-0.75f, LIBC_NAMESPACE::exp2m1f(-2.0f));
+}
+
+TEST_F(LlvmLibcExp2m1fTest, Overflow) {
+ LIBC_NAMESPACE::libc_errno = 0;
+ EXPECT_FP_EQ_WITH_EXCEPTION(
+ inf, LIBC_NAMESPACE::exp2m1f(FPBits(0x7f7f'ffffU).get_val()),
+ FE_OVERFLOW);
+ EXPECT_MATH_ERRNO(ERANGE);
+
+ EXPECT_FP_EQ_WITH_EXCEPTION(
+ inf, LIBC_NAMESPACE::exp2m1f(FPBits(0x4300'0000U).get_val()),
+ FE_OVERFLOW);
+ EXPECT_MATH_ERRNO(ERANGE);
+
+ EXPECT_FP_EQ_WITH_EXCEPTION(
+ inf, LIBC_NAMESPACE::exp2m1f(FPBits(0x4300'0001U).get_val()),
+ FE_OVERFLOW);
+ EXPECT_MATH_ERRNO(ERANGE);
+}
diff --git a/libc/utils/MPFRWrapper/MPFRUtils.cpp b/libc/utils/MPFRWrapper/MPFRUtils.cpp
index 2e1c44e6fd5da9..d694d893b45aac 100644
--- a/libc/utils/MPFRWrapper/MPFRUtils.cpp
+++ b/libc/utils/MPFRWrapper/MPFRUtils.cpp
@@ -223,6 +223,12 @@ class MPFRNumber {
return result;
}
+ MPFRNumber exp2m1() const {
+ MPFRNumber result(*this);
+ mpfr_exp2m1(result.value, value, mpfr_rounding);
+ return result;
+ }
+
MPFRNumber exp10() const {
MPFRNumber result(*this);
mpfr_exp10(result.value, value, mpfr_rounding);
@@ -564,6 +570,8 @@ unary_operation(Operation op, InputType input, unsigned int precision,
return mpfrInput.exp();
case Operation::Exp2:
return mpfrInput.exp2();
+ case Operation::Exp2m1:
+ return mpfrInput.exp2m1();
case Operation::Exp10:
return mpfrInput.exp10();
case Operation::Expm1:
diff --git a/libc/utils/MPFRWrapper/MPFRUtils.h b/libc/utils/MPFRWrapper/MPFRUtils.h
index 6164d78fa5adc4..66e83f6f0dcc34 100644
--- a/libc/utils/MPFRWrapper/MPFRUtils.h
+++ b/libc/utils/MPFRWrapper/MPFRUtils.h
@@ -37,6 +37,7 @@ enum class Operation : int {
Erf,
Exp,
Exp2,
+ Exp2m1,
Exp10,
Expm1,
Floor,
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