[libc-commits] [libc] [libc][math][c23] Add exp2m1f C23 math function (PR #86996)
via libc-commits
libc-commits at lists.llvm.org
Sun Mar 31 17:40:07 PDT 2024
https://github.com/overmighty updated https://github.com/llvm/llvm-project/pull/86996
>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 1/3] [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,
>From 5db48641785f8739f1df8d9fba500e15a4def2a2 Mon Sep 17 00:00:00 2001
From: OverMighty <its.overmighty at gmail.com>
Date: Fri, 29 Mar 2024 19:28:12 +0000
Subject: [PATCH 2/3] fixup! [libc][math][c23] Add exp2m1f C23 math function
---
libc/docs/math/index.rst | 2 +
libc/src/math/generic/exp2m1f.cpp | 72 +++++++++++++++++------
libc/test/src/math/CMakeLists.txt | 16 +++++
libc/test/src/math/exp2m1f_test.cpp | 67 +++++++++++++++++++++
libc/test/src/math/smoke/CMakeLists.txt | 1 -
libc/test/src/math/smoke/exp2m1f_test.cpp | 39 +++++++-----
6 files changed, 165 insertions(+), 32 deletions(-)
create mode 100644 libc/test/src/math/exp2m1f_test.cpp
diff --git a/libc/docs/math/index.rst b/libc/docs/math/index.rst
index 080b6a4427f511..02d3dbfd7ba3bf 100644
--- a/libc/docs/math/index.rst
+++ b/libc/docs/math/index.rst
@@ -480,6 +480,8 @@ Higher Math Functions
+------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
| exp2l | | | | | | | | | | | | |
+------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
+| exp2m1f | |check| | | | | | | | | | | | |
++------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
| expm1 | |check| | |check| | |check| | |check| | |check| | | | |check| | |check| | |check| | | |
+------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
| expm1f | |check| | |check| | |check| | |check| | |check| | | | |check| | |check| | |check| | | |
diff --git a/libc/src/math/generic/exp2m1f.cpp b/libc/src/math/generic/exp2m1f.cpp
index ea5c637b0b8692..3790171ed531eb 100644
--- a/libc/src/math/generic/exp2m1f.cpp
+++ b/libc/src/math/generic/exp2m1f.cpp
@@ -10,6 +10,7 @@
#include "src/__support/FPUtil/FEnvImpl.h"
#include "src/__support/FPUtil/FPBits.h"
#include "src/__support/FPUtil/PolyEval.h"
+#include "src/__support/FPUtil/except_value_utils.h"
#include "src/__support/FPUtil/multiply_add.h"
#include "src/__support/FPUtil/rounding_mode.h"
#include "src/__support/common.h"
@@ -21,6 +22,40 @@
namespace LIBC_NAMESPACE {
+static constexpr size_t N_EXCEPTS_LO = 8;
+
+static constexpr fputil::ExceptValues<float, N_EXCEPTS_LO> EXP2M1F_EXCEPTS_LO =
+ {{
+ // (input, RZ output, RU offset, RD offset, RN offset)
+ // x = 0x1.36dc8ep-36, exp2m1f(x) = 0x1.aef212p-37 (RZ)
+ {0x2d9b'6e47U, 0x2d57'7909U, 1U, 0U, 0U},
+ // x = 0x1.224936p-19, exp2m1f(x) = 0x1.926c0ep-20 (RZ)
+ {0x3611'249bU, 0x35c9'3607U, 1U, 0U, 1U},
+ // x = 0x1.d16d2p-20, exp2m1f(x) = 0x1.429becp-20 (RZ)
+ {0x35e8'b690U, 0x35a1'4df6U, 1U, 0U, 1U},
+ // x = 0x1.17949ep-14, exp2m1f(x) = 0x1.8397p-15 (RZ)
+ {0x388b'ca4fU, 0x3841'cb80U, 1U, 0U, 1U},
+ // x = -0x1.9c3e1ep-38, exp2m1f(x) = -0x1.1dbeacp-38 (RZ)
+ {0xacce'1f0fU, 0xac8e'df56U, 0U, 1U, 0U},
+ // x = -0x1.4d89b4p-32, exp2m1f(x) = -0x1.ce61b6p-33 (RZ)
+ {0xafa6'c4daU, 0xaf67'30dbU, 0U, 1U, 1U},
+ // x = -0x1.a6eac4p-10, exp2m1f(x) = -0x1.24fadap-10 (RZ)
+ {0xbad3'7562U, 0xba92'7d6dU, 0U, 1U, 1U},
+ // x = -0x1.e7526ep-6, exp2m1f(x) = -0x1.4e53dep-6 (RZ)
+ {0xbcf3'a937U, 0xbca7'29efU, 0U, 1U, 1U},
+ }};
+
+static constexpr size_t N_EXCEPTS_HI = 2;
+
+static constexpr fputil::ExceptValues<float, N_EXCEPTS_HI> EXP2M1F_EXCEPTS_HI =
+ {{
+ // (input, RZ output, RU offset, RD offset, RN offset)
+ // x = 0x1.16a972p-1, exp2m1f(x) = 0x1.d545b2p-2 (RZ)
+ {0x3f0b'54b9U, 0x3eea'a2d9U, 1U, 0U, 0U},
+ // x = -0x1.9f12acp-5, exp2m1f(x) = -0x1.1ab68cp-5 (RZ)
+ {0xbd4f'8956U, 0xbd0d'5b46U, 0U, 1U, 0U},
+ }};
+
LLVM_LIBC_FUNCTION(float, exp2m1f, (float x)) {
using FPBits = fputil::FPBits<float>;
FPBits xbits(x);
@@ -32,7 +67,8 @@ LLVM_LIBC_FUNCTION(float, exp2m1f, (float x)) {
if (LIBC_UNLIKELY(x_abs >= 0x4300'0000U || x_abs <= 0x3d00'0000U)) {
// |x| <= 2^-5
if (x_abs <= 0x3d00'0000) {
- // TODO: Handle exceptional values.
+ if (auto r = EXP2M1F_EXCEPTS_LO.lookup(x_u); LIBC_UNLIKELY(r.has_value()))
+ return r.value();
// Minimax polynomial generated by Sollya with:
// > display = hexadecimal;
@@ -63,26 +99,28 @@ LLVM_LIBC_FUNCTION(float, exp2m1f, (float x)) {
// 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);
+ if (LIBC_UNLIKELY(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;
}
+ if (auto r = EXP2M1F_EXCEPTS_HI.lookup(x_u); LIBC_UNLIKELY(r.has_value()))
+ return r.value();
+
// 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:
diff --git a/libc/test/src/math/CMakeLists.txt b/libc/test/src/math/CMakeLists.txt
index 026bcd12928bdf..d27c3218416732 100644
--- a/libc/test/src/math/CMakeLists.txt
+++ b/libc/test/src/math/CMakeLists.txt
@@ -637,6 +637,22 @@ add_fp_unittest(
libc.src.__support.FPUtil.fp_bits
)
+add_fp_unittest(
+ exp2m1f_test
+ NEED_MPFR
+ SUITE
+ libc-math-unittests
+ SRCS
+ exp2m1f_test.cpp
+ DEPENDS
+ libc.include.llvm-libc-macros.math_macros
+ libc.include.llvm-libc-macros.stdint_macros
+ libc.src.errno.errno
+ libc.src.math.exp2m1f
+ libc.src.__support.CPP.array
+ libc.src.__support.FPUtil.fp_bits
+)
+
add_fp_unittest(
exp10f_test
NEED_MPFR
diff --git a/libc/test/src/math/exp2m1f_test.cpp b/libc/test/src/math/exp2m1f_test.cpp
new file mode 100644
index 00000000000000..b35d94cb0f788d
--- /dev/null
+++ b/libc/test/src/math/exp2m1f_test.cpp
@@ -0,0 +1,67 @@
+//===-- 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 "include/llvm-libc-macros/math-macros.h"
+#include "src/__support/CPP/array.h"
+#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"
+#include "utils/MPFRWrapper/MPFRUtils.h"
+
+#include <stdint.h>
+
+using LlvmLibcExp2m1fTest = LIBC_NAMESPACE::testing::FPTest<float>;
+
+namespace mpfr = LIBC_NAMESPACE::testing::mpfr;
+
+TEST_F(LlvmLibcExp2m1fTest, TrickyInputs) {
+ constexpr LIBC_NAMESPACE::cpp::array<float, 10> INPUTS = {
+ // EXP2M1F_EXCEPTS_LO
+ 0x1.36dc8ep-36,
+ 0x1.224936p-19,
+ 0x1.d16d2p-20,
+ 0x1.17949ep-14,
+ -0x1.9c3e1ep-38,
+ -0x1.4d89b4p-32,
+ -0x1.a6eac4p-10,
+ -0x1.e7526ep-6,
+ // EXP2M1F_EXCEPTS_HI
+ 0x1.16a972p-1,
+ -0x1.9f12acp-5,
+ };
+
+ for (float x : INPUTS) {
+ LIBC_NAMESPACE::libc_errno = 0;
+ EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Exp2m1, x,
+ LIBC_NAMESPACE::exp2m1f(x), 0.5);
+ EXPECT_MATH_ERRNO(0);
+ }
+}
+
+TEST_F(LlvmLibcExp2m1fTest, InFloatRange) {
+ constexpr uint32_t COUNT = 100'000;
+ constexpr uint32_t STEP = UINT32_MAX / COUNT;
+ for (uint32_t i = 0, v = 0; i <= COUNT; ++i, v += STEP) {
+ float x = FPBits(v).get_val();
+ if (isnan(x) || isinf(x))
+ continue;
+ LIBC_NAMESPACE::libc_errno = 0;
+ float result = LIBC_NAMESPACE::exp2m1f(x);
+
+ // If the computation resulted in an error or did not produce valid result
+ // in the single-precision floating point range, then ignore comparing with
+ // MPFR result as MPFR can still produce valid results because of its
+ // wider precision.
+ if (isnan(result) || isinf(result) || LIBC_NAMESPACE::libc_errno != 0)
+ continue;
+ ASSERT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Exp2m1, x,
+ LIBC_NAMESPACE::exp2m1f(x), 0.5);
+ }
+}
diff --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
index d07927f5d5e4bf..c65d6339d6c671 100644
--- a/libc/test/src/math/smoke/CMakeLists.txt
+++ b/libc/test/src/math/smoke/CMakeLists.txt
@@ -776,7 +776,6 @@ add_fp_unittest(
SRCS
exp2m1f_test.cpp
DEPENDS
- libc.src.__support.FPUtil.fp_bits
libc.src.errno.errno
libc.src.math.exp2m1f
)
diff --git a/libc/test/src/math/smoke/exp2m1f_test.cpp b/libc/test/src/math/smoke/exp2m1f_test.cpp
index 1db865b91a0c26..c144856b30b769 100644
--- a/libc/test/src/math/smoke/exp2m1f_test.cpp
+++ b/libc/test/src/math/smoke/exp2m1f_test.cpp
@@ -6,29 +6,26 @@
//
//===----------------------------------------------------------------------===//
-#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>;
+using LIBC_NAMESPACE::fputil::testing::ForceRoundingMode;
+using LIBC_NAMESPACE::fputil::testing::RoundingMode;
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);
@@ -40,18 +37,32 @@ TEST_F(LlvmLibcExp2m1fTest, SpecialNumbers) {
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_FP_EQ_WITH_EXCEPTION(inf, LIBC_NAMESPACE::exp2m1f(0x1.fffffep+127),
+ FE_OVERFLOW);
+ EXPECT_MATH_ERRNO(ERANGE);
+
+ EXPECT_FP_EQ_WITH_EXCEPTION(inf, LIBC_NAMESPACE::exp2m1f(128.0f),
+ FE_OVERFLOW);
+ EXPECT_MATH_ERRNO(ERANGE);
+
+ EXPECT_FP_EQ_WITH_EXCEPTION(inf, LIBC_NAMESPACE::exp2m1f(0x1.000002p+7),
+ FE_OVERFLOW);
+ EXPECT_MATH_ERRNO(ERANGE);
+}
+
+TEST_F(LlvmLibcExp2m1fTest, Underflow) {
+ LIBC_NAMESPACE::libc_errno = 0;
+
+ EXPECT_FP_EQ_WITH_EXCEPTION(-1.0f, LIBC_NAMESPACE::exp2m1f(-0x1.fffffep+127),
+ FE_UNDERFLOW);
EXPECT_MATH_ERRNO(ERANGE);
- EXPECT_FP_EQ_WITH_EXCEPTION(
- inf, LIBC_NAMESPACE::exp2m1f(FPBits(0x4300'0000U).get_val()),
- FE_OVERFLOW);
+ EXPECT_FP_EQ_WITH_EXCEPTION(-1.0f, LIBC_NAMESPACE::exp2m1f(-25.0f),
+ FE_UNDERFLOW);
EXPECT_MATH_ERRNO(ERANGE);
- EXPECT_FP_EQ_WITH_EXCEPTION(
- inf, LIBC_NAMESPACE::exp2m1f(FPBits(0x4300'0001U).get_val()),
- FE_OVERFLOW);
+ EXPECT_FP_EQ_WITH_EXCEPTION(-1.0f, LIBC_NAMESPACE::exp2m1f(-0x1.900002p4),
+ FE_UNDERFLOW);
EXPECT_MATH_ERRNO(ERANGE);
}
>From 28a6b56a75333cc2be87d138487046f5f0b304b6 Mon Sep 17 00:00:00 2001
From: OverMighty <its.overmighty at gmail.com>
Date: Mon, 1 Apr 2024 01:38:51 +0100
Subject: [PATCH 3/3] fixup! [libc][math][c23] Add exp2m1f C23 math function
---
libc/utils/MPFRWrapper/MPFRUtils.cpp | 37 +++++++++++++++++++++++++---
1 file changed, 34 insertions(+), 3 deletions(-)
diff --git a/libc/utils/MPFRWrapper/MPFRUtils.cpp b/libc/utils/MPFRWrapper/MPFRUtils.cpp
index d694d893b45aac..50c51498304d50 100644
--- a/libc/utils/MPFRWrapper/MPFRUtils.cpp
+++ b/libc/utils/MPFRWrapper/MPFRUtils.cpp
@@ -134,6 +134,12 @@ class MPFRNumber {
mpfr_set(value, other.value, mpfr_rounding);
}
+ MPFRNumber(const MPFRNumber &other, unsigned int precision)
+ : mpfr_precision(precision), mpfr_rounding(other.mpfr_rounding) {
+ mpfr_init2(value, mpfr_precision);
+ mpfr_set(value, other.value, mpfr_rounding);
+ }
+
~MPFRNumber() { mpfr_clear(value); }
MPFRNumber &operator=(const MPFRNumber &rhs) {
@@ -223,10 +229,28 @@ class MPFRNumber {
return result;
}
- MPFRNumber exp2m1() const {
+ MPFRNumber
+ exp2m1([[maybe_unused]] const MPFRNumber &underflow_rndz_fallback) const {
+ // TODO: Only use mpfr_exp2m1 once CI and buildbots get MPFR >= 4.2.0.
+#if MPFR_VERSION_MAJOR > 4 || \
+ (MPFR_VERSION_MAJOR == 4 && MPFR_VERSION_MINOR >= 2)
MPFRNumber result(*this);
mpfr_exp2m1(result.value, value, mpfr_rounding);
return result;
+#else
+ MPFRNumber result(*this, mpfr_precision * 8);
+ mpfr_exp2(result.value, value, mpfr_rounding);
+
+ if (mpfr_underflow_p()) {
+ mpfr_clear_underflow();
+
+ if (mpfr_rounding == MPFR_RNDZ)
+ return underflow_rndz_fallback;
+ }
+
+ mpfr_sub_ui(result.value, result.value, 1, mpfr_rounding);
+ return result;
+#endif
}
MPFRNumber exp10() const {
@@ -570,8 +594,15 @@ 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::Exp2m1: {
+ constexpr InputType UNDERFLOW_RNDZ_FALLBACK =
+ FPBits<InputType>::create_value(Sign::NEG,
+ -1 + FPBits<InputType>::EXP_BIAS,
+ FPBits<InputType>::SIG_MASK)
+ .get_val();
+ MPFRNumber underflow_rndz_fallback(UNDERFLOW_RNDZ_FALLBACK);
+ return mpfrInput.exp2m1(underflow_rndz_fallback);
+ }
case Operation::Exp10:
return mpfrInput.exp10();
case Operation::Expm1:
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