[libc][math][c23] Add exp2m1f C23 math function #86996
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overmighty
commented
Mar 28, 2024
libc/src/math/generic/exp2m1f.cpp
Outdated
| } | ||
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| // x <= -25 | ||
| if (x <= -25.0f) { |
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In exp2f you compare x_u. I assume it's a small optimization based on integer comparisons usually being cheaper than floating-point ones. For example, on x86-64, cmp seems cheaper than {,v}ucomiss:
- https://uops.info/table.html?search=cmp%20(r32%2C%20i32)&cb_lat=on&cb_tp=on&cb_uops=on&cb_ports=on&cb_ADLP=on&cb_ADLE=on&cb_measurements=on&cb_doc=on&cb_base=on
- https://uops.info/table.html?search=ucomiss&cb_lat=on&cb_tp=on&cb_uops=on&cb_ports=on&cb_ADLP=on&cb_ADLE=on&cb_measurements=on&cb_doc=on&cb_avx=on&cb_sse=on
I can change this if you want. Also, the comment is pretty useless if I don't change it.
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You can benchmark later, but there are several reasons:
- the first one is that inside CPUs, floating point instructions and integer instructions use different ports, and switching values between them does have some hidden cost, like the above we use integer comparisons to omit inf / nan.
- second is that with multiple tight conditions, keeping them as integers will help compilers to optimize better, since the full semantic of floating point is more complicated, such as it's easy for us to see that NaNs cannot get here, but not so easy for the compilers.
And of course everything is just guessing. Once you finish the implementations and accuracy tests, you can try both with performance tests to see if it has any affects.
|
It seems to have been added in MPFR 4.2.0: https://gitlab.inria.fr/mpfr/mpfr/-/commit/78f1866613ca67b801ce4c17f103e2bc1e576fc1. I don't know what OS the CI runs but MPFR >= 4.2.0 isn't available on any Ubuntu LTS release: https://packages.ubuntu.com/search?suite=default§ion=all&arch=any&keywords=libmpfr-dev&searchon=names. Should I add |
You can implement |
|
@llvm/pr-subscribers-libc Author: OverMighty (overmighty) ChangesFixes #86502. TODO:
cc @lntue Patch is 22.57 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/86996.diff 15 Files Affected:
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/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/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..3790171ed531eb
--- /dev/null
+++ b/libc/src/math/generic/exp2m1f.cpp
@@ -0,0 +1,182 @@
+//===-- 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/except_value_utils.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 {
+
+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);
+
+ 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) {
+ 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;
+ // > 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();
+ }
+ }
+
+ 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:
+ // 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/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/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/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 3b756127fe21ea..c65d6339d6c671 100644
--- a/libc/test/src/math/smoke/CMakeLists.txt
+++ b/libc/test/src/math/smoke/CMakeLists.txt
@@ -769,6 +769,17 @@ 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.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..c144856b30b769
--- /dev/null
+++ b/libc/test/src/math/smoke/exp2m1f_test.cpp
@@ -0,0 +1,68 @@
+//===-- 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/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);
+
+ 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(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(-1.0f, LIBC_NAMESPACE::exp2m1f(-25.0f),
+ FE_UNDERFLOW);
+ EXPECT_MATH_ERRNO(ERANGE);
+
+ EXPECT_FP_EQ_WITH_EXCEPTION(-1.0f, LIBC_NAMESPACE::exp2m1f(-0x1.900002p4),
+ FE_UNDERFLOW);
+ EXPECT_MA...
[truncated]
|
overmighty
commented
Apr 1, 2024
| {{ | ||
| // (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}, |
There was a problem hiding this comment.
Not sure when exactly to use the U suffix and when not to use it.
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U suffix means the literal is unsigned. This is opposed to unsigned x = 7; where 7 is signed with an implicit cast inserted in front during AST parsing. Dumping the ast alludes to this, and makes it more understandable.
https://godbolt.org/z/7n5MT4xYM
Notice the declaration of foo has an ImplictCast node inserted in the AST; the declaration of bar does not.
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Yes but existing code sometimes doesn't use the U suffix in literals that initialize variables of unsigned integer types and in literals that are compared against variables of unsigned integer types, and sometimes uses it. I'm not sure if there's a rule for this or if it just doesn't really matter if it's inconsistent (as long as it doesn't change the program's behavior).
lntue
reviewed
Apr 1, 2024
lntue
reviewed
Apr 2, 2024
libc/src/math/generic/exp2m1f.cpp
Outdated
Comment on lines
173
to
178
| 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); |
There was a problem hiding this comment.
You can combine these into double p = fputil::polyeval(dx_sq, c1, c2, c3);
Also update the comment to reflect the computation steps are done here: mh * exp2_lo - 1.
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Shouldn't we also rename dx and dx_sq to lo and lo_sq instead of stating that dx = lo in the comment above the declaration of dx?
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+1. Also update dx appearance in some of the comments.
There was a problem hiding this comment.
There aren't any comments in this file that reference dx.
overmighty
commented
Apr 3, 2024
| #include "test/UnitTest/Test.h" | ||
| #include "utils/MPFRWrapper/MPFRUtils.h" | ||
|
|
||
| #include <stdint.h> |
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I thought of including include/llvm-libc-macros/stdint-macros.h instead for UINT32_MAX, but there are other includes that end up including stdint.h, which redefines UINT32_MAX. I could include stdint-macros.h after all the other headers but I'm not sure if it makes sense.
Also, some files include *.h headers (e.g., stdint.h) and some include the c* alternatives (e.g., cstdint). Is there a rule for this?
There was a problem hiding this comment.
That's ok, we are going to re-organize and codify how to include standard headers soon: #87017
lntue
reviewed
Apr 3, 2024
|
@overmighty : Can you sync and resolve the merge conflict? |
|
Sure. Sorry I didn't notice it earlier. |
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I confirm all exhaustive tests are ok. On a Intel(R) Xeon(R) Silver 4214 I get the following timings: The timings are very close to core-math (the "glibc" timings are those from core-math, since exp2m1f is not yet available in GNU libc). |
Thanks Paul! |
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Fixes #86502.
cc @lntue