[libc-commits] [libc] [llvm] [libc][math][c++23] Add expbf16 math function (PR #161919)
Krishna Pandey via libc-commits
libc-commits at lists.llvm.org
Thu Jun 25 04:04:33 PDT 2026
https://github.com/krishna2803 updated https://github.com/llvm/llvm-project/pull/161919
>From df2bd8ae5b7f8d5433ec6695df623f57b383315c Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Sat, 4 Oct 2025 03:38:34 +0530
Subject: [PATCH 01/20] feat: implement expbf16 higher math function
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
libc/src/math/CMakeLists.txt | 1 +
libc/src/math/expbf16.h | 21 +++
libc/src/math/generic/CMakeLists.txt | 22 ++++
libc/src/math/generic/expbf16.cpp | 184 +++++++++++++++++++++++++++
4 files changed, 228 insertions(+)
create mode 100644 libc/src/math/expbf16.h
create mode 100644 libc/src/math/generic/expbf16.cpp
diff --git a/libc/src/math/CMakeLists.txt b/libc/src/math/CMakeLists.txt
index 3c7e99f4a9c46..d74b43e0f923b 100644
--- a/libc/src/math/CMakeLists.txt
+++ b/libc/src/math/CMakeLists.txt
@@ -139,6 +139,7 @@ add_math_entrypoint_object(erff)
add_math_entrypoint_object(exp)
add_math_entrypoint_object(expf)
add_math_entrypoint_object(expf16)
+add_math_entrypoint_object(expbf16)
add_math_entrypoint_object(exp2)
add_math_entrypoint_object(exp2f)
diff --git a/libc/src/math/expbf16.h b/libc/src/math/expbf16.h
new file mode 100644
index 0000000000000..7c7aed30b4a51
--- /dev/null
+++ b/libc/src/math/expbf16.h
@@ -0,0 +1,21 @@
+//===-- Implementation header for expbf16 -----------------------*- 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_EXPBF16_H
+#define LLVM_LIBC_SRC_MATH_EXPBF16_H
+
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/types.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+bfloat16 expbf16(bfloat16 x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_MATH_EXPBF16_H
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index 8074a3925626c..0adcc7fd31015 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -1441,6 +1441,28 @@ add_entrypoint_object(
libc.src.errno.errno
)
+add_entrypoint_object(
+ expbf16
+ SRCS
+ expbf16.cpp
+ HDRS
+ ../expbf16.h
+ DEPENDS
+ libc.hdr.errno_macros
+ libc.hdr.fenv_macros
+ libc.src.__support.CPP.array
+ libc.src.__support.FPUtil.cast
+ libc.src.__support.FPUtil.except_value_utils
+ libc.src.__support.FPUtil.fenv_impl
+ libc.src.__support.FPUtil.fp_bits
+ libc.src.__support.FPUtil.multiply_add
+ libc.src.__support.FPUtil.nearest_integer
+ libc.src.__support.FPUtil.polyeval
+ libc.src.__support.FPUtil.rounding_mode
+ libc.src.__support.FPUtil.bfloat16
+ libc.src.__support.macros.optimization
+)
+
add_entrypoint_object(
exp2
SRCS
diff --git a/libc/src/math/generic/expbf16.cpp b/libc/src/math/generic/expbf16.cpp
new file mode 100644
index 0000000000000..bd03660a4a11d
--- /dev/null
+++ b/libc/src/math/generic/expbf16.cpp
@@ -0,0 +1,184 @@
+//===-- BFloat16 e^x 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/expbf16.h"
+
+#include "hdr/errno_macros.h"
+#include "hdr/fenv_macros.h"
+#include "src/__support/FPUtil/FEnvImpl.h"
+#include "src/__support/FPUtil/FPBits.h"
+#include "src/__support/FPUtil/PolyEval.h"
+#include "src/__support/FPUtil/bfloat16.h"
+#include "src/__support/FPUtil/cast.h"
+#include "src/__support/FPUtil/except_value_utils.h"
+#include "src/__support/FPUtil/multiply_add.h"
+#include "src/__support/FPUtil/nearest_integer.h"
+#include "src/__support/FPUtil/rounding_mode.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/optimization.h"
+#include "src/__support/macros/properties/types.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+// Generated by Sollya with the following commands:
+// > display = hexadecimal;
+// > for i from -96 to 88 by 8 do print(i, round(exp(i), SG, RN) @ "f,");
+static constexpr float EXP_HI[24] = {
+ 0x1.6a4p-139f, 0x1.07b71p-127f, 0x1.7fd974p-116f, 0x1.175afp-104f,
+ 0x1.969d48p-93f, 0x1.27ec46p-81f, 0x1.aebabap-70f, 0x1.397924p-58f,
+ 0x1.c8465p-47f, 0x1.4c1078p-35f, 0x1.e355bcp-24f, 0x1.5fc21p-12f,
+ 0x1p0f, 0x1.749ea8p11f, 0x1.0f2ebep23f, 0x1.8ab7fcp34f,
+ 0x1.1f43fcp46f, 0x1.a220d4p57f, 0x1.304d6ap69f, 0x1.baed16p80f,
+ 0x1.425982p92f, 0x1.d531d8p103f, 0x1.55779cp115f, 0x1.f1056ep126f,
+};
+
+// Generated by Sollya with the following commands:
+// > display = hexadecimal;
+// > for i from 0 to 7.75 by 0.25 do print(round(exp(i), SG, RN) @ "f,");
+static constexpr float EXP_MID[32] = {
+ 0x1p0f, 0x1.48b5e4p0f, 0x1.a61298p0f, 0x1.0ef9dcp1f,
+ 0x1.5bf0a8p1f, 0x1.bec38ep1f, 0x1.1ed3fep2f, 0x1.704b6ap2f,
+ 0x1.d8e64cp2f, 0x1.2f9b88p3f, 0x1.85d6fep3f, 0x1.f4907p3f,
+ 0x1.415e5cp4f, 0x1.9ca53cp4f, 0x1.08ec72p5f, 0x1.542b2ep5f,
+ 0x1.b4c902p5f, 0x1.186bf2p6f, 0x1.68118ap6f, 0x1.ce564ep6f,
+ 0x1.28d38ap7f, 0x1.7d21eep7f, 0x1.e96244p7f, 0x1.3a30dp8f,
+ 0x1.936dc6p8f, 0x1.0301a4p9f, 0x1.4c9222p9f, 0x1.ab0786p9f,
+ 0x1.122886p10f, 0x1.6006b6p10f, 0x1.c402b6p10f, 0x1.223252p11f,
+};
+
+constexpr fputil::ExceptValues<bfloat16, 4> EXPBF16_EXCEPTS = {{
+ // (input, RZ output, RU offset, RD offset, RN offset)
+ // x = 0x40DB (6.84375)
+ // MPFR: RU=0x446B, RD=0x446A, RZ=0x446A, RN=0x446B
+ {0x40DBU, 0x446AU, 1U, 0U, 1U},
+ // x = 0x419D, keep original
+ {0x419DU, 0x4D9FU, 1U, 0U, 0U},
+ // x = 0x41F9 (31.125)
+ // MPFR: RU=0x55F0, RD=0x55EF, RZ=0x55EF, RN=0x55F0
+ {0x41F9U, 0x55EFU, 1U, 0U, 1U},
+ // x = 0xC19F (-19.875)
+ // MPFR: RU=0x3121, RD=0x3120, RZ=0x3120, RN=0x3121
+ {0xC19FU, 0x3120U, 1U, 0U, 1U},
+}};
+
+LLVM_LIBC_FUNCTION(bfloat16, expbf16, (bfloat16 x)) {
+ using FPBits = fputil::FPBits<bfloat16>;
+ FPBits x_bits(x);
+
+ uint16_t x_u = x_bits.uintval();
+ uint16_t x_abs = x_u & 0x7fffU;
+
+ // 0 <= |x| <= 2^(-3), or |x| >= 89, or x is NaN
+ if (LIBC_UNLIKELY(x_abs <= 0x3e00U || x_abs >= 0x42b2U)) {
+
+ // exp(NaN) = NaN
+ if (x_bits.is_nan()) {
+ if (x_bits.is_signaling_nan()) {
+ fputil::raise_except_if_required(FE_INVALID);
+ return FPBits::quiet_nan().get_val();
+ }
+
+ return x;
+ }
+
+ // if x >= 89
+ if (x_bits.is_pos() && x_abs >= 0x42b2U) {
+ // exp(inf) = inf
+ if (x_bits.is_inf())
+ return FPBits::inf().get_val();
+
+ switch (fputil::quick_get_round()) {
+ case FE_TONEAREST:
+ case FE_UPWARD:
+ fputil::set_errno_if_required(ERANGE);
+ fputil::raise_except_if_required(FE_OVERFLOW);
+ return FPBits::inf().get_val();
+ default:
+ return FPBits::max_normal().get_val();
+ }
+ }
+
+ // x <= -93
+ if (x_u >= 0xc2baU) {
+ // exp(-inf) = +0
+ if (x_bits.is_inf())
+ return FPBits::zero().get_val();
+
+ fputil::set_errno_if_required(ERANGE);
+ fputil::raise_except_if_required(FE_UNDERFLOW | FE_INEXACT);
+
+ switch (fputil::quick_get_round()) {
+ case FE_UPWARD:
+ return FPBits::min_subnormal().get_val();
+ default:
+ return FPBits::zero().get_val();
+ }
+ }
+
+ // 0 < |x| <= 2^(-3)
+ if (x_abs <= 0x3e00U && !x_bits.is_zero()) {
+ float xf = static_cast<float>(x);
+ // Degree-3 minimax polynomial generated by Sollya with the following
+ // commands:
+ // > display = hexadecimal;
+ // > P = fpminimax(expm1(x)/x, 2, [|SG...|], [-2^-7, 2^-7]);
+ // > 1 + x * P;
+ // 0x1p0 + x * (0x1p0 + x * (0x1.00004p-1 + x * 0x1.555578p-3))
+ return fputil::cast<bfloat16>(
+ fputil::polyeval(xf, 0x1p+0f, 0x1p+0f, 0x1.0004p-1f, 0x1.555778p-3f));
+ }
+
+ // exp(0) = 1
+ if (x_bits.is_zero())
+ return bfloat16(1.0f);
+ }
+
+ if (auto r = EXPBF16_EXCEPTS.lookup(x_u); LIBC_UNLIKELY(r.has_value()))
+ return r.value();
+
+ // For -93 < x < 89, we do the following range reduction:
+ // x = hi + mid + lo
+ // where,
+ // hi / 2^3 is an integer
+ // mid * 2^2 is an integer
+ // -2^3 <= lo <= 2^3
+ // also, hi + mid = round(4 * x) / x
+ // then,
+ // exp(x) = exp(hi + mid + lo)
+ // = exp(hi) * exp(mid) * exp(lo)
+ // we store 184/8 + 1 = 24 values for looking up exp(hi)
+ // from -96 to 88
+ // we store 8*4 = 32 values for looking up exp(mid) since
+ // mid will always have the bit pattern |bbb.bb| where
+ // b can be either 0 or 1
+
+ float xf = static_cast<float>(x);
+ float kf = fputil::nearest_integer(xf * 4.0f);
+ int x_hi_mid = static_cast<int>(kf);
+ int x_hi = x_hi_mid >> 5;
+ int x_mid = x_hi_mid & 0b11111;
+ // lo = x - (hi + mid) = round(x * 4) / (-4) + x
+ float lo = fputil::multiply_add(kf, -0.25f, xf);
+
+ float exp_hi = EXP_HI[x_hi + 12];
+ float exp_mid = EXP_MID[x_mid];
+
+ // Degree-3 minimax polynomial generated by Sollya with the following
+ // commands:
+ // > display = hexadecimal;
+ // > P = fpminimax(expm1(x)/x, 2, [|SG...|], [-2^-7, 2^-7]);
+ // > 1 + x * P;
+ // 0x1p0 + x * (0x1p0 + x * (0x1.00004p-1 + x * 0x1.555578p-3))
+ float exp_lo =
+ fputil::polyeval(lo, 0x1p+0f, 0x1p+0f, 0x1.0004p-1f, 0x1.555778p-3f);
+
+ return fputil::cast<bfloat16>(exp_hi * exp_mid * exp_lo);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
>From a0d196c92de60888072f07ac0d13b987d776c08e Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Sat, 4 Oct 2025 03:39:00 +0530
Subject: [PATCH 02/20] chore: add smoke and general tests for expbf16 higher
math function
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
libc/test/src/math/CMakeLists.txt | 12 +++++
libc/test/src/math/expbf16_test.cpp | 59 +++++++++++++++++++++
libc/test/src/math/smoke/CMakeLists.txt | 14 +++++
libc/test/src/math/smoke/expbf16_test.cpp | 63 +++++++++++++++++++++++
4 files changed, 148 insertions(+)
create mode 100644 libc/test/src/math/expbf16_test.cpp
create mode 100644 libc/test/src/math/smoke/expbf16_test.cpp
diff --git a/libc/test/src/math/CMakeLists.txt b/libc/test/src/math/CMakeLists.txt
index 2d2d5287bb384..299762cbbc808 100644
--- a/libc/test/src/math/CMakeLists.txt
+++ b/libc/test/src/math/CMakeLists.txt
@@ -1138,6 +1138,18 @@ add_fp_unittest(
libc.src.math.expf16
)
+add_fp_unittest(
+ expbf16_test
+ NEED_MPFR
+ SUITE
+ libc-math-unittests
+ SRCS
+ expbf16_test.cpp
+ DEPENDS
+ libc.src.math.expbf16
+ libc.src.__support.FPUtil.bfloat16
+)
+
add_fp_unittest(
exp2_test
NEED_MPFR
diff --git a/libc/test/src/math/expbf16_test.cpp b/libc/test/src/math/expbf16_test.cpp
new file mode 100644
index 0000000000000..35f247348f9dc
--- /dev/null
+++ b/libc/test/src/math/expbf16_test.cpp
@@ -0,0 +1,59 @@
+//===-- Exhaustive test for expbf16 ---------------------------------------===//
+//
+// 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/bfloat16.h"
+#include "src/math/expbf16.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/Test.h"
+#include "utils/MPFRWrapper/MPFRUtils.h"
+
+using LlvmLibcExpBf16Test = LIBC_NAMESPACE::testing::FPTest<bfloat16>;
+
+namespace mpfr = LIBC_NAMESPACE::testing::mpfr;
+
+// range: [0, inf]
+static constexpr uint16_t POS_START = 0x0000U;
+static constexpr uint16_t POS_STOP = 0x7f80U;
+// static constexpr uint16_t POS_STOP = 0x3e00U;
+
+// range: [-0, -inf]
+static constexpr uint16_t NEG_START = 0x8000U;
+static constexpr uint16_t NEG_STOP = 0xff80U;
+
+TEST_F(LlvmLibcExpBf16Test, PositiveRange) {
+ for (uint16_t v = POS_START; v <= POS_STOP; ++v) {
+ bfloat16 x = FPBits(v).get_val();
+ EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Exp, x,
+ LIBC_NAMESPACE::expbf16(x), 0.5);
+ }
+
+ auto test_value = [&](uint16_t v) {
+ bfloat16 x = FPBits(v).get_val();
+ EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Exp, x,
+ LIBC_NAMESPACE::expbf16(x), 0.5);
+ };
+
+ auto test_value_f = [&](float v) {
+ bfloat16 x(v);
+ EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Exp, x,
+ LIBC_NAMESPACE::expbf16(x), 0.5);
+ };
+
+ test_value(0xc2c8);
+ test_value(0xc2ba);
+
+ test_value_f(17.45f);
+}
+
+TEST_F(LlvmLibcExpBf16Test, NegativeRange) {
+ for (uint16_t v = NEG_START; v <= NEG_STOP; ++v) {
+ bfloat16 x = FPBits(v).get_val();
+ EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Exp, x,
+ LIBC_NAMESPACE::expbf16(x), 0.5);
+ }
+}
diff --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
index 42a97ba10b601..8373423b7bc13 100644
--- a/libc/test/src/math/smoke/CMakeLists.txt
+++ b/libc/test/src/math/smoke/CMakeLists.txt
@@ -1395,6 +1395,20 @@ add_fp_unittest(
libc.src.__support.FPUtil.cast
)
+add_fp_unittest(
+ expbf16_test
+ SUITE
+ libc-math-smoke-tests
+ SRCS
+ expbf16_test.cpp
+ DEPENDS
+ libc.hdr.errno_macros
+ libc.hdr.fenv_macros
+ libc.src.math.expbf16
+ libc.src.__support.FPUtil.bfloat16
+ libc.src.__support.FPUtil.cast
+)
+
add_fp_unittest(
exp2_test
SUITE
diff --git a/libc/test/src/math/smoke/expbf16_test.cpp b/libc/test/src/math/smoke/expbf16_test.cpp
new file mode 100644
index 0000000000000..8576b78e4391e
--- /dev/null
+++ b/libc/test/src/math/smoke/expbf16_test.cpp
@@ -0,0 +1,63 @@
+//===-- Unittests for expbf16 ---------------------------------------------===//
+//
+// 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 "hdr/errno_macros.h"
+#include "hdr/fenv_macros.h"
+#include "src/__support/FPUtil/bfloat16.h"
+#include "src/__support/FPUtil/cast.h"
+#include "src/math/expbf16.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/Test.h"
+
+using LlvmLibcExpf16Test = LIBC_NAMESPACE::testing::FPTest<bfloat16>;
+
+TEST_F(LlvmLibcExpf16Test, SpecialNumbers) {
+ EXPECT_FP_IS_NAN(LIBC_NAMESPACE::expbf16(aNaN));
+ EXPECT_MATH_ERRNO(0);
+
+ EXPECT_FP_IS_NAN_WITH_EXCEPTION(LIBC_NAMESPACE::expbf16(sNaN), FE_INVALID);
+ EXPECT_MATH_ERRNO(0);
+
+ EXPECT_FP_EQ_ALL_ROUNDING(inf, LIBC_NAMESPACE::expbf16(inf));
+ EXPECT_MATH_ERRNO(0);
+
+ EXPECT_FP_EQ_ALL_ROUNDING(zero, LIBC_NAMESPACE::expbf16(neg_inf));
+ EXPECT_MATH_ERRNO(0);
+
+ EXPECT_FP_EQ_ALL_ROUNDING(LIBC_NAMESPACE::fputil::cast<bfloat16>(1.0f),
+ LIBC_NAMESPACE::expbf16(zero));
+ EXPECT_MATH_ERRNO(0);
+
+ EXPECT_FP_EQ_ALL_ROUNDING(LIBC_NAMESPACE::fputil::cast<bfloat16>(1.0f),
+ LIBC_NAMESPACE::expbf16(neg_zero));
+ EXPECT_MATH_ERRNO(0);
+}
+
+TEST_F(LlvmLibcExpf16Test, Overflow) {
+ EXPECT_FP_EQ_WITH_EXCEPTION(inf, LIBC_NAMESPACE::expbf16(max_normal),
+ FE_OVERFLOW);
+ EXPECT_MATH_ERRNO(ERANGE);
+
+ EXPECT_FP_EQ_WITH_EXCEPTION(
+ inf,
+ LIBC_NAMESPACE::expbf16(LIBC_NAMESPACE::fputil::cast<bfloat16>(89.0f)),
+ FE_OVERFLOW);
+ EXPECT_MATH_ERRNO(ERANGE);
+}
+
+TEST_F(LlvmLibcExpf16Test, Underflow) {
+ EXPECT_FP_EQ_WITH_EXCEPTION(zero, LIBC_NAMESPACE::expbf16(neg_max_normal),
+ FE_UNDERFLOW | FE_INEXACT);
+ EXPECT_MATH_ERRNO(ERANGE);
+
+ EXPECT_FP_EQ_WITH_EXCEPTION(
+ zero,
+ LIBC_NAMESPACE::expbf16(LIBC_NAMESPACE::fputil::cast<bfloat16>(-92.5f)),
+ FE_UNDERFLOW | FE_INEXACT);
+ EXPECT_MATH_ERRNO(ERANGE);
+}
>From b4f6ffbb89c8da1076e0e296784abd2432bcd4dc Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Sat, 4 Oct 2025 03:40:12 +0530
Subject: [PATCH 03/20] chore: update entrypoints
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
libc/config/baremetal/aarch64/entrypoints.txt | 1 +
libc/config/baremetal/arm/entrypoints.txt | 1 +
libc/config/baremetal/riscv/entrypoints.txt | 1 +
libc/config/darwin/aarch64/entrypoints.txt | 1 +
libc/config/darwin/x86_64/entrypoints.txt | 1 +
libc/config/gpu/amdgpu/entrypoints.txt | 1 +
libc/config/gpu/nvptx/entrypoints.txt | 1 +
libc/config/linux/aarch64/entrypoints.txt | 1 +
libc/config/linux/arm/entrypoints.txt | 1 +
libc/config/linux/riscv/entrypoints.txt | 1 +
libc/config/linux/x86_64/entrypoints.txt | 1 +
libc/config/windows/entrypoints.txt | 1 +
12 files changed, 12 insertions(+)
diff --git a/libc/config/baremetal/aarch64/entrypoints.txt b/libc/config/baremetal/aarch64/entrypoints.txt
index 935c95af0d4af..f8d0ed5167d43 100644
--- a/libc/config/baremetal/aarch64/entrypoints.txt
+++ b/libc/config/baremetal/aarch64/entrypoints.txt
@@ -778,6 +778,7 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
libc.src.math.canonicalizebf16
libc.src.math.ceilbf16
libc.src.math.copysignbf16
+ libc.src.math.expbf16
libc.src.math.fabsbf16
libc.src.math.fdimbf16
libc.src.math.floorbf16
diff --git a/libc/config/baremetal/arm/entrypoints.txt b/libc/config/baremetal/arm/entrypoints.txt
index 82e257c1d2b0d..3291d54c6e308 100644
--- a/libc/config/baremetal/arm/entrypoints.txt
+++ b/libc/config/baremetal/arm/entrypoints.txt
@@ -778,6 +778,7 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
libc.src.math.canonicalizebf16
libc.src.math.ceilbf16
libc.src.math.copysignbf16
+ libc.src.math.expbf16
libc.src.math.fabsbf16
libc.src.math.fdimbf16
libc.src.math.floorbf16
diff --git a/libc/config/baremetal/riscv/entrypoints.txt b/libc/config/baremetal/riscv/entrypoints.txt
index c10cc1162cc5a..bf0e7d7108bdb 100644
--- a/libc/config/baremetal/riscv/entrypoints.txt
+++ b/libc/config/baremetal/riscv/entrypoints.txt
@@ -778,6 +778,7 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
libc.src.math.canonicalizebf16
libc.src.math.ceilbf16
libc.src.math.copysignbf16
+ libc.src.math.expbf16
libc.src.math.fabsbf16
libc.src.math.fdimbf16
libc.src.math.floorbf16
diff --git a/libc/config/darwin/aarch64/entrypoints.txt b/libc/config/darwin/aarch64/entrypoints.txt
index e3c6c2b30c415..d5eba9cdf4f9d 100644
--- a/libc/config/darwin/aarch64/entrypoints.txt
+++ b/libc/config/darwin/aarch64/entrypoints.txt
@@ -608,6 +608,7 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
libc.src.math.canonicalizebf16
libc.src.math.ceilbf16
libc.src.math.copysignbf16
+ libc.src.math.expbf16
libc.src.math.fabsbf16
libc.src.math.fdimbf16
libc.src.math.floorbf16
diff --git a/libc/config/darwin/x86_64/entrypoints.txt b/libc/config/darwin/x86_64/entrypoints.txt
index e899bf97ea3f6..78dab1d24d20c 100644
--- a/libc/config/darwin/x86_64/entrypoints.txt
+++ b/libc/config/darwin/x86_64/entrypoints.txt
@@ -251,6 +251,7 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
libc.src.math.canonicalizebf16
libc.src.math.ceilbf16
libc.src.math.copysignbf16
+ libc.src.math.expbf16
libc.src.math.fabsbf16
libc.src.math.fdimbf16
libc.src.math.floorbf16
diff --git a/libc/config/gpu/amdgpu/entrypoints.txt b/libc/config/gpu/amdgpu/entrypoints.txt
index 0dda7d5c683ec..524e42c0f6c94 100644
--- a/libc/config/gpu/amdgpu/entrypoints.txt
+++ b/libc/config/gpu/amdgpu/entrypoints.txt
@@ -634,6 +634,7 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
libc.src.math.canonicalizebf16
libc.src.math.ceilbf16
libc.src.math.copysignbf16
+ libc.src.math.expbf16
libc.src.math.fabsbf16
libc.src.math.fdimbf16
libc.src.math.floorbf16
diff --git a/libc/config/gpu/nvptx/entrypoints.txt b/libc/config/gpu/nvptx/entrypoints.txt
index 6070fb5b17b3c..d6450cdba6dce 100644
--- a/libc/config/gpu/nvptx/entrypoints.txt
+++ b/libc/config/gpu/nvptx/entrypoints.txt
@@ -636,6 +636,7 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
libc.src.math.canonicalizebf16
libc.src.math.ceilbf16
libc.src.math.copysignbf16
+ libc.src.math.expbf16
libc.src.math.fabsbf16
libc.src.math.fdimbf16
libc.src.math.floorbf16
diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
index ae8deabc97407..184e7878dbc24 100644
--- a/libc/config/linux/aarch64/entrypoints.txt
+++ b/libc/config/linux/aarch64/entrypoints.txt
@@ -861,6 +861,7 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
libc.src.math.canonicalizebf16
libc.src.math.ceilbf16
libc.src.math.copysignbf16
+ libc.src.math.expbf16
libc.src.math.fabsbf16
libc.src.math.fdimbf16
libc.src.math.floorbf16
diff --git a/libc/config/linux/arm/entrypoints.txt b/libc/config/linux/arm/entrypoints.txt
index f04ac40145d3a..999f863bbba36 100644
--- a/libc/config/linux/arm/entrypoints.txt
+++ b/libc/config/linux/arm/entrypoints.txt
@@ -478,6 +478,7 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
libc.src.math.canonicalizebf16
libc.src.math.ceilbf16
libc.src.math.copysignbf16
+ libc.src.math.expbf16
libc.src.math.fabsbf16
libc.src.math.fdimbf16
libc.src.math.floorbf16
diff --git a/libc/config/linux/riscv/entrypoints.txt b/libc/config/linux/riscv/entrypoints.txt
index 5f407e842121e..c54ce62703131 100644
--- a/libc/config/linux/riscv/entrypoints.txt
+++ b/libc/config/linux/riscv/entrypoints.txt
@@ -883,6 +883,7 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
libc.src.math.canonicalizebf16
libc.src.math.ceilbf16
libc.src.math.copysignbf16
+ libc.src.math.expbf16
libc.src.math.fabsbf16
libc.src.math.fdimbf16
libc.src.math.floorbf16
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index bf2ad4a40ca11..e55e2664f0818 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -918,6 +918,7 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
libc.src.math.canonicalizebf16
libc.src.math.ceilbf16
libc.src.math.copysignbf16
+ libc.src.math.expbf16
libc.src.math.fabsbf16
libc.src.math.fdimbf16
libc.src.math.floorbf16
diff --git a/libc/config/windows/entrypoints.txt b/libc/config/windows/entrypoints.txt
index 3a76595b258e2..750715c83cbca 100644
--- a/libc/config/windows/entrypoints.txt
+++ b/libc/config/windows/entrypoints.txt
@@ -324,6 +324,7 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
libc.src.math.canonicalizebf16
libc.src.math.ceilbf16
libc.src.math.copysignbf16
+ libc.src.math.expbf16
libc.src.math.fabsbf16
libc.src.math.fdimbf16
libc.src.math.floorbf16
>From a317ac67f2b6aa4bb77865d330f73d9746608bc8 Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Sat, 4 Oct 2025 03:41:23 +0530
Subject: [PATCH 04/20] docs: add expbf16 higher math function
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
libc/docs/headers/math/index.rst | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libc/docs/headers/math/index.rst b/libc/docs/headers/math/index.rst
index 51bf238b950b0..529fb2f798be2 100644
--- a/libc/docs/headers/math/index.rst
+++ b/libc/docs/headers/math/index.rst
@@ -289,7 +289,7 @@ Higher Math Functions
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
| cosh | |check| | | | |check| | | | 7.12.5.4 | F.10.2.4 |
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
-| cospi | |check| | | | |check| | | | 7.12.4.12 | F.10.1.12 |
+| cospi | |check| | | | |check| | | |check| | 7.12.4.12 | F.10.1.12 |
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
| dsqrt | N/A | N/A | |check| | N/A | |check|\* | | 7.12.14.6 | F.10.11 |
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
>From 27da1ff10d8eeb700379150646dca8b905ef1cb4 Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Sat, 4 Oct 2025 03:45:11 +0530
Subject: [PATCH 05/20] docs: fix incorrect check
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
libc/docs/headers/math/index.rst | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/libc/docs/headers/math/index.rst b/libc/docs/headers/math/index.rst
index 529fb2f798be2..c10c42408eea0 100644
--- a/libc/docs/headers/math/index.rst
+++ b/libc/docs/headers/math/index.rst
@@ -289,7 +289,7 @@ Higher Math Functions
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
| cosh | |check| | | | |check| | | | 7.12.5.4 | F.10.2.4 |
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
-| cospi | |check| | | | |check| | | |check| | 7.12.4.12 | F.10.1.12 |
+| cospi | |check| | | | |check| | | | 7.12.4.12 | F.10.1.12 |
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
| dsqrt | N/A | N/A | |check| | N/A | |check|\* | | 7.12.14.6 | F.10.11 |
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
@@ -297,7 +297,7 @@ Higher Math Functions
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
| erfc | | | | | | | 7.12.8.2 | F.10.5.2 |
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
-| exp | |check| | |check| | | |check| | | | 7.12.6.1 | F.10.3.1 |
+| exp | |check| | |check| | | |check| | | |check| | 7.12.6.1 | F.10.3.1 |
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
| exp10 | |check| | |check| | | |check| | | | 7.12.6.2 | F.10.3.2 |
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
>From 270f0a190a96a2662be1885547b3735e4b32ada2 Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Sat, 4 Oct 2025 03:52:01 +0530
Subject: [PATCH 06/20] chore: remove junk tests
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
libc/test/src/math/expbf16_test.cpp | 17 -----------------
1 file changed, 17 deletions(-)
diff --git a/libc/test/src/math/expbf16_test.cpp b/libc/test/src/math/expbf16_test.cpp
index 35f247348f9dc..14889d4fa9ee4 100644
--- a/libc/test/src/math/expbf16_test.cpp
+++ b/libc/test/src/math/expbf16_test.cpp
@@ -31,23 +31,6 @@ TEST_F(LlvmLibcExpBf16Test, PositiveRange) {
EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Exp, x,
LIBC_NAMESPACE::expbf16(x), 0.5);
}
-
- auto test_value = [&](uint16_t v) {
- bfloat16 x = FPBits(v).get_val();
- EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Exp, x,
- LIBC_NAMESPACE::expbf16(x), 0.5);
- };
-
- auto test_value_f = [&](float v) {
- bfloat16 x(v);
- EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Exp, x,
- LIBC_NAMESPACE::expbf16(x), 0.5);
- };
-
- test_value(0xc2c8);
- test_value(0xc2ba);
-
- test_value_f(17.45f);
}
TEST_F(LlvmLibcExpBf16Test, NegativeRange) {
>From d58d2eedd976dec8772dba26e0aaa1b7ea0fe2a1 Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Sat, 4 Oct 2025 22:59:39 +0530
Subject: [PATCH 07/20] chore: update and fix test
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
libc/src/math/generic/expbf16.cpp | 11 +++++++----
libc/test/src/math/smoke/expbf16_test.cpp | 2 +-
2 files changed, 8 insertions(+), 5 deletions(-)
diff --git a/libc/src/math/generic/expbf16.cpp b/libc/src/math/generic/expbf16.cpp
index bd03660a4a11d..6bb6d2e0f5288 100644
--- a/libc/src/math/generic/expbf16.cpp
+++ b/libc/src/math/generic/expbf16.cpp
@@ -104,8 +104,8 @@ LLVM_LIBC_FUNCTION(bfloat16, expbf16, (bfloat16 x)) {
}
}
- // x <= -93
- if (x_u >= 0xc2baU) {
+ // x <= -92.5
+ if (x_u >= 0xc2b9U) {
// exp(-inf) = +0
if (x_bits.is_inf())
return FPBits::zero().get_val();
@@ -115,7 +115,10 @@ LLVM_LIBC_FUNCTION(bfloat16, expbf16, (bfloat16 x)) {
switch (fputil::quick_get_round()) {
case FE_UPWARD:
- return FPBits::min_subnormal().get_val();
+ case FE_TONEAREST:
+ if (LIBC_UNLIKELY(x_u == 0xc2b9U))
+ return FPBits::min_subnormal().get_val();
+ return FPBits::zero().get_val();
default:
return FPBits::zero().get_val();
}
@@ -145,7 +148,7 @@ LLVM_LIBC_FUNCTION(bfloat16, expbf16, (bfloat16 x)) {
// For -93 < x < 89, we do the following range reduction:
// x = hi + mid + lo
// where,
- // hi / 2^3 is an integer
+ // hi is an integer
// mid * 2^2 is an integer
// -2^3 <= lo <= 2^3
// also, hi + mid = round(4 * x) / x
diff --git a/libc/test/src/math/smoke/expbf16_test.cpp b/libc/test/src/math/smoke/expbf16_test.cpp
index 8576b78e4391e..cc501571383e3 100644
--- a/libc/test/src/math/smoke/expbf16_test.cpp
+++ b/libc/test/src/math/smoke/expbf16_test.cpp
@@ -57,7 +57,7 @@ TEST_F(LlvmLibcExpf16Test, Underflow) {
EXPECT_FP_EQ_WITH_EXCEPTION(
zero,
- LIBC_NAMESPACE::expbf16(LIBC_NAMESPACE::fputil::cast<bfloat16>(-92.5f)),
+ LIBC_NAMESPACE::expbf16(LIBC_NAMESPACE::fputil::cast<bfloat16>(-93.0f)),
FE_UNDERFLOW | FE_INEXACT);
EXPECT_MATH_ERRNO(ERANGE);
}
>From 0816194c3a92df6aa879885f5b96ccffb3ccd3aa Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Mon, 6 Oct 2025 17:31:27 +0530
Subject: [PATCH 08/20] chore: remove redundant comment
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
libc/test/src/math/expbf16_test.cpp | 1 -
1 file changed, 1 deletion(-)
diff --git a/libc/test/src/math/expbf16_test.cpp b/libc/test/src/math/expbf16_test.cpp
index 14889d4fa9ee4..c2288af74fe12 100644
--- a/libc/test/src/math/expbf16_test.cpp
+++ b/libc/test/src/math/expbf16_test.cpp
@@ -19,7 +19,6 @@ namespace mpfr = LIBC_NAMESPACE::testing::mpfr;
// range: [0, inf]
static constexpr uint16_t POS_START = 0x0000U;
static constexpr uint16_t POS_STOP = 0x7f80U;
-// static constexpr uint16_t POS_STOP = 0x3e00U;
// range: [-0, -inf]
static constexpr uint16_t NEG_START = 0x8000U;
>From 9e9d4719e2029142484d84a965822cdc91137fa1 Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Thu, 18 Jun 2026 18:26:40 +0530
Subject: [PATCH 09/20] add: expbf16 to shared math functions
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
libc/shared/math.h | 1 +
libc/shared/math/expbf16.h | 23 +++++++++++++++++++++++
2 files changed, 24 insertions(+)
create mode 100644 libc/shared/math/expbf16.h
diff --git a/libc/shared/math.h b/libc/shared/math.h
index f4b28e3aa139d..f9b847b835f57 100644
--- a/libc/shared/math.h
+++ b/libc/shared/math.h
@@ -114,6 +114,7 @@
#include "math/exp2f16.h"
#include "math/exp2m1f.h"
#include "math/exp2m1f16.h"
+#include "math/expbf16.h"
#include "math/expf.h"
#include "math/expf16.h"
#include "math/expm1.h"
diff --git a/libc/shared/math/expbf16.h b/libc/shared/math/expbf16.h
new file mode 100644
index 0000000000000..0aae861917f7f
--- /dev/null
+++ b/libc/shared/math/expbf16.h
@@ -0,0 +1,23 @@
+//===-- Shared expbf16 function ---------------------------------*- 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_SHARED_MATH_EXPBF16_H
+#define LLVM_LIBC_SHARED_MATH_EXPBF16_H
+
+#include "shared/libc_common.h"
+#include "src/__support/math/expbf16.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::expbf16;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SHARED_MATH_EXPBF16_H
>From c4c0a5761261485d6c6b367ed2e0ffabc8563037 Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Thu, 18 Jun 2026 18:27:09 +0530
Subject: [PATCH 10/20] refactor: expbf16 to __support math functions
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
libc/src/__support/math/CMakeLists.txt | 21 +++
libc/src/__support/math/expbf16.h | 194 +++++++++++++++++++++++++
libc/src/math/generic/expbf16.cpp | 178 +----------------------
3 files changed, 217 insertions(+), 176 deletions(-)
create mode 100644 libc/src/__support/math/expbf16.h
diff --git a/libc/src/__support/math/CMakeLists.txt b/libc/src/__support/math/CMakeLists.txt
index b57e82a036665..4c57f8333cc5c 100644
--- a/libc/src/__support/math/CMakeLists.txt
+++ b/libc/src/__support/math/CMakeLists.txt
@@ -3125,6 +3125,27 @@ add_header_library(
libc.src.__support.math.exp10_float16_constants
)
+
+add_header_library(
+ expbf16
+ HDRS
+ expbf16.h
+ DEPENDS
+ libc.hdr.errno_macros
+ libc.hdr.fenv_macros
+ libc.src.__support.CPP.array
+ libc.src.__support.FPUtil.cast
+ libc.src.__support.FPUtil.except_value_utils
+ libc.src.__support.FPUtil.fenv_impl
+ libc.src.__support.FPUtil.fp_bits
+ libc.src.__support.FPUtil.multiply_add
+ libc.src.__support.FPUtil.nearest_integer
+ libc.src.__support.FPUtil.polyeval
+ libc.src.__support.FPUtil.rounding_mode
+ libc.src.__support.FPUtil.bfloat16
+ libc.src.__support.macros.optimization
+)
+
add_header_library(
f16add
HDRS
diff --git a/libc/src/__support/math/expbf16.h b/libc/src/__support/math/expbf16.h
new file mode 100644
index 0000000000000..b9a6f7689de1b
--- /dev/null
+++ b/libc/src/__support/math/expbf16.h
@@ -0,0 +1,194 @@
+//===-- Implementation header for expbf16 -----------------------*- 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___SUPPORT_MATH_EXPBF16_H
+#define LLVM_LIBC_SRC___SUPPORT_MATH_EXPBF16_H
+
+#include "hdr/errno_macros.h"
+#include "hdr/fenv_macros.h"
+#include "src/__support/FPUtil/FEnvImpl.h"
+#include "src/__support/FPUtil/FPBits.h"
+#include "src/__support/FPUtil/PolyEval.h"
+#include "src/__support/FPUtil/bfloat16.h"
+#include "src/__support/FPUtil/cast.h"
+#include "src/__support/FPUtil/except_value_utils.h"
+#include "src/__support/FPUtil/multiply_add.h"
+#include "src/__support/FPUtil/nearest_integer.h"
+#include "src/__support/FPUtil/rounding_mode.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/optimization.h"
+#include "src/__support/macros/properties/types.h"
+
+// bfloat16 expbf16(bfloat16 x);
+
+namespace LIBC_NAMESPACE_DECL {
+
+namespace math {
+
+// Generated by Sollya with the following commands:
+// > display = hexadecimal;
+// > for i from -96 to 88 by 8 do print(i, round(exp(i), SG, RN) @ "f,");
+LIBC_INLINE_VAR constexpr float EXP_HI[24] = {
+ 0x1.6a4p-139f, 0x1.07b71p-127f, 0x1.7fd974p-116f, 0x1.175afp-104f,
+ 0x1.969d48p-93f, 0x1.27ec46p-81f, 0x1.aebabap-70f, 0x1.397924p-58f,
+ 0x1.c8465p-47f, 0x1.4c1078p-35f, 0x1.e355bcp-24f, 0x1.5fc21p-12f,
+ 0x1p0f, 0x1.749ea8p11f, 0x1.0f2ebep23f, 0x1.8ab7fcp34f,
+ 0x1.1f43fcp46f, 0x1.a220d4p57f, 0x1.304d6ap69f, 0x1.baed16p80f,
+ 0x1.425982p92f, 0x1.d531d8p103f, 0x1.55779cp115f, 0x1.f1056ep126f,
+};
+
+// Generated by Sollya with the following commands:
+// > display = hexadecimal;
+// > for i from 0 to 7.75 by 0.25 do print(round(exp(i), SG, RN) @ "f,");
+LIBC_INLINE_VAR constexpr float EXP_MID[32] = {
+ 0x1p0f, 0x1.48b5e4p0f, 0x1.a61298p0f, 0x1.0ef9dcp1f,
+ 0x1.5bf0a8p1f, 0x1.bec38ep1f, 0x1.1ed3fep2f, 0x1.704b6ap2f,
+ 0x1.d8e64cp2f, 0x1.2f9b88p3f, 0x1.85d6fep3f, 0x1.f4907p3f,
+ 0x1.415e5cp4f, 0x1.9ca53cp4f, 0x1.08ec72p5f, 0x1.542b2ep5f,
+ 0x1.b4c902p5f, 0x1.186bf2p6f, 0x1.68118ap6f, 0x1.ce564ep6f,
+ 0x1.28d38ap7f, 0x1.7d21eep7f, 0x1.e96244p7f, 0x1.3a30dp8f,
+ 0x1.936dc6p8f, 0x1.0301a4p9f, 0x1.4c9222p9f, 0x1.ab0786p9f,
+ 0x1.122886p10f, 0x1.6006b6p10f, 0x1.c402b6p10f, 0x1.223252p11f,
+};
+
+LIBC_INLINE bfloat16 expbf16(bfloat16 x) {
+ using FPBits = fputil::FPBits<bfloat16>;
+ FPBits x_bits(x);
+
+ uint16_t x_u = x_bits.uintval();
+ uint16_t x_abs = x_u & 0x7fffU;
+
+ // 0 <= |x| <= 2^(-3), or |x| >= 89, or x is NaN
+ if (LIBC_UNLIKELY(x_abs <= 0x3e00U || x_abs >= 0x42b2U)) {
+
+ // exp(NaN) = NaN
+ if (x_bits.is_nan()) {
+ if (x_bits.is_signaling_nan()) {
+ fputil::raise_except_if_required(FE_INVALID);
+ return FPBits::quiet_nan().get_val();
+ }
+
+ return x;
+ }
+
+ // if x >= 89
+ if (x_bits.is_pos() && x_abs >= 0x42b2U) {
+ // exp(inf) = inf
+ if (x_bits.is_inf())
+ return x;
+
+ switch (fputil::quick_get_round()) {
+ case FE_TONEAREST:
+ case FE_UPWARD:
+ fputil::set_errno_if_required(ERANGE);
+ fputil::raise_except_if_required(FE_OVERFLOW);
+ return FPBits::inf().get_val();
+ default:
+ return FPBits::max_normal().get_val();
+ }
+ }
+
+ // x <= -92.5
+ if (x_u >= 0xc2b9U) {
+ // exp(-inf) = +0
+ if (x_bits.is_inf())
+ return FPBits::zero().get_val();
+
+ fputil::set_errno_if_required(ERANGE);
+ fputil::raise_except_if_required(FE_UNDERFLOW | FE_INEXACT);
+
+ switch (fputil::quick_get_round()) {
+ case FE_UPWARD:
+ case FE_TONEAREST:
+ if (LIBC_UNLIKELY(x_u == 0xc2b9U))
+ return FPBits::min_subnormal().get_val();
+ return FPBits::zero().get_val();
+ default:
+ return FPBits::zero().get_val();
+ }
+ }
+
+ // 0 < |x| <= 2^(-3)
+ if (x_abs <= 0x3e00U && !x_bits.is_zero()) {
+ float xf = static_cast<float>(x);
+ // Degree-3 minimax polynomial generated by Sollya with the following
+ // commands:
+ // > display = hexadecimal;
+ // > P = fpminimax(expm1(x)/x, 2, [|SG...|], [-2^-7, 2^-7]);
+ // > 1 + x * P;
+ // 0x1p0 + x * (0x1p0 + x * (0x1.00004p-1 + x * 0x1.555578p-3))
+ return fputil::cast<bfloat16>(
+ fputil::polyeval(xf, 0x1p+0f, 0x1p+0f, 0x1.0004p-1f, 0x1.555778p-3f));
+ }
+
+ // exp(0) = 1
+ if (x_bits.is_zero())
+ return bfloat16(1.0f);
+ }
+
+ constexpr fputil::ExceptValues<bfloat16, 4> EXPBF16_EXCEPTS = {{
+ // (input, RZ output, RU offset, RD offset, RN offset)
+ // x = 0x40DB (6.84375)
+ // MPFR: RU=0x446B, RD=0x446A, RZ=0x446A, RN=0x446B
+ {0x40DBU, 0x446AU, 1U, 0U, 1U},
+ // x = 0x419D, keep original
+ {0x419DU, 0x4D9FU, 1U, 0U, 0U},
+ // x = 0x41F9 (31.125)
+ // MPFR: RU=0x55F0, RD=0x55EF, RZ=0x55EF, RN=0x55F0
+ {0x41F9U, 0x55EFU, 1U, 0U, 1U},
+ // x = 0xC19F (-19.875)
+ // MPFR: RU=0x3121, RD=0x3120, RZ=0x3120, RN=0x3121
+ {0xC19FU, 0x3120U, 1U, 0U, 1U},
+ }};
+
+ if (auto r = EXPBF16_EXCEPTS.lookup(x_u); LIBC_UNLIKELY(r.has_value()))
+ return r.value();
+
+ // For -93 < x < 89, we do the following range reduction:
+ // x = hi + mid + lo
+ // where,
+ // hi is an integer
+ // mid * 2^2 is an integer
+ // -2^3 <= lo <= 2^3
+ // also, hi + mid = round(4 * x) / x
+ // then,
+ // exp(x) = exp(hi + mid + lo)
+ // = exp(hi) * exp(mid) * exp(lo)
+ // we store 184/8 + 1 = 24 values for looking up exp(hi)
+ // from -96 to 88
+ // we store 8*4 = 32 values for looking up exp(mid) since
+ // mid will always have the bit pattern |bbb.bb| where
+ // b can be either 0 or 1
+
+ float xf = static_cast<float>(x);
+ float kf = fputil::nearest_integer(xf * 4.0f);
+ int x_hi_mid = static_cast<int>(kf);
+ int x_hi = x_hi_mid >> 5;
+ int x_mid = x_hi_mid & 0b11111;
+ // lo = x - (hi + mid) = round(x * 4) / (-4) + x
+ float lo = fputil::multiply_add(kf, -0.25f, xf);
+
+ float exp_hi = EXP_HI[x_hi + 12];
+ float exp_mid = EXP_MID[x_mid];
+
+ // Degree-3 minimax polynomial generated by Sollya with the following
+ // commands:
+ // > display = hexadecimal;
+ // > P = fpminimax(expm1(x)/x, 2, [|SG...|], [-2^-7, 2^-7]);
+ // > 1 + x * P;
+ // 0x1p0 + x * (0x1p0 + x * (0x1.00004p-1 + x * 0x1.555578p-3))
+ float exp_lo =
+ fputil::polyeval(lo, 0x1p+0f, 0x1p+0f, 0x1.0004p-1f, 0x1.555778p-3f);
+
+ return fputil::cast<bfloat16>(exp_hi * exp_mid * exp_lo);
+}
+} // namespace math
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC___SUPPORT_MATH_EXPBF16_H
diff --git a/libc/src/math/generic/expbf16.cpp b/libc/src/math/generic/expbf16.cpp
index 6bb6d2e0f5288..ba48185d9864e 100644
--- a/libc/src/math/generic/expbf16.cpp
+++ b/libc/src/math/generic/expbf16.cpp
@@ -6,182 +6,8 @@
//
//===----------------------------------------------------------------------===//
+#include "src/__support/math/expbf16.h"
#include "src/math/expbf16.h"
-#include "hdr/errno_macros.h"
-#include "hdr/fenv_macros.h"
-#include "src/__support/FPUtil/FEnvImpl.h"
-#include "src/__support/FPUtil/FPBits.h"
-#include "src/__support/FPUtil/PolyEval.h"
-#include "src/__support/FPUtil/bfloat16.h"
-#include "src/__support/FPUtil/cast.h"
-#include "src/__support/FPUtil/except_value_utils.h"
-#include "src/__support/FPUtil/multiply_add.h"
-#include "src/__support/FPUtil/nearest_integer.h"
-#include "src/__support/FPUtil/rounding_mode.h"
-#include "src/__support/common.h"
-#include "src/__support/macros/config.h"
-#include "src/__support/macros/optimization.h"
-#include "src/__support/macros/properties/types.h"
-
namespace LIBC_NAMESPACE_DECL {
-
-// Generated by Sollya with the following commands:
-// > display = hexadecimal;
-// > for i from -96 to 88 by 8 do print(i, round(exp(i), SG, RN) @ "f,");
-static constexpr float EXP_HI[24] = {
- 0x1.6a4p-139f, 0x1.07b71p-127f, 0x1.7fd974p-116f, 0x1.175afp-104f,
- 0x1.969d48p-93f, 0x1.27ec46p-81f, 0x1.aebabap-70f, 0x1.397924p-58f,
- 0x1.c8465p-47f, 0x1.4c1078p-35f, 0x1.e355bcp-24f, 0x1.5fc21p-12f,
- 0x1p0f, 0x1.749ea8p11f, 0x1.0f2ebep23f, 0x1.8ab7fcp34f,
- 0x1.1f43fcp46f, 0x1.a220d4p57f, 0x1.304d6ap69f, 0x1.baed16p80f,
- 0x1.425982p92f, 0x1.d531d8p103f, 0x1.55779cp115f, 0x1.f1056ep126f,
-};
-
-// Generated by Sollya with the following commands:
-// > display = hexadecimal;
-// > for i from 0 to 7.75 by 0.25 do print(round(exp(i), SG, RN) @ "f,");
-static constexpr float EXP_MID[32] = {
- 0x1p0f, 0x1.48b5e4p0f, 0x1.a61298p0f, 0x1.0ef9dcp1f,
- 0x1.5bf0a8p1f, 0x1.bec38ep1f, 0x1.1ed3fep2f, 0x1.704b6ap2f,
- 0x1.d8e64cp2f, 0x1.2f9b88p3f, 0x1.85d6fep3f, 0x1.f4907p3f,
- 0x1.415e5cp4f, 0x1.9ca53cp4f, 0x1.08ec72p5f, 0x1.542b2ep5f,
- 0x1.b4c902p5f, 0x1.186bf2p6f, 0x1.68118ap6f, 0x1.ce564ep6f,
- 0x1.28d38ap7f, 0x1.7d21eep7f, 0x1.e96244p7f, 0x1.3a30dp8f,
- 0x1.936dc6p8f, 0x1.0301a4p9f, 0x1.4c9222p9f, 0x1.ab0786p9f,
- 0x1.122886p10f, 0x1.6006b6p10f, 0x1.c402b6p10f, 0x1.223252p11f,
-};
-
-constexpr fputil::ExceptValues<bfloat16, 4> EXPBF16_EXCEPTS = {{
- // (input, RZ output, RU offset, RD offset, RN offset)
- // x = 0x40DB (6.84375)
- // MPFR: RU=0x446B, RD=0x446A, RZ=0x446A, RN=0x446B
- {0x40DBU, 0x446AU, 1U, 0U, 1U},
- // x = 0x419D, keep original
- {0x419DU, 0x4D9FU, 1U, 0U, 0U},
- // x = 0x41F9 (31.125)
- // MPFR: RU=0x55F0, RD=0x55EF, RZ=0x55EF, RN=0x55F0
- {0x41F9U, 0x55EFU, 1U, 0U, 1U},
- // x = 0xC19F (-19.875)
- // MPFR: RU=0x3121, RD=0x3120, RZ=0x3120, RN=0x3121
- {0xC19FU, 0x3120U, 1U, 0U, 1U},
-}};
-
-LLVM_LIBC_FUNCTION(bfloat16, expbf16, (bfloat16 x)) {
- using FPBits = fputil::FPBits<bfloat16>;
- FPBits x_bits(x);
-
- uint16_t x_u = x_bits.uintval();
- uint16_t x_abs = x_u & 0x7fffU;
-
- // 0 <= |x| <= 2^(-3), or |x| >= 89, or x is NaN
- if (LIBC_UNLIKELY(x_abs <= 0x3e00U || x_abs >= 0x42b2U)) {
-
- // exp(NaN) = NaN
- if (x_bits.is_nan()) {
- if (x_bits.is_signaling_nan()) {
- fputil::raise_except_if_required(FE_INVALID);
- return FPBits::quiet_nan().get_val();
- }
-
- return x;
- }
-
- // if x >= 89
- if (x_bits.is_pos() && x_abs >= 0x42b2U) {
- // exp(inf) = inf
- if (x_bits.is_inf())
- return FPBits::inf().get_val();
-
- switch (fputil::quick_get_round()) {
- case FE_TONEAREST:
- case FE_UPWARD:
- fputil::set_errno_if_required(ERANGE);
- fputil::raise_except_if_required(FE_OVERFLOW);
- return FPBits::inf().get_val();
- default:
- return FPBits::max_normal().get_val();
- }
- }
-
- // x <= -92.5
- if (x_u >= 0xc2b9U) {
- // exp(-inf) = +0
- if (x_bits.is_inf())
- return FPBits::zero().get_val();
-
- fputil::set_errno_if_required(ERANGE);
- fputil::raise_except_if_required(FE_UNDERFLOW | FE_INEXACT);
-
- switch (fputil::quick_get_round()) {
- case FE_UPWARD:
- case FE_TONEAREST:
- if (LIBC_UNLIKELY(x_u == 0xc2b9U))
- return FPBits::min_subnormal().get_val();
- return FPBits::zero().get_val();
- default:
- return FPBits::zero().get_val();
- }
- }
-
- // 0 < |x| <= 2^(-3)
- if (x_abs <= 0x3e00U && !x_bits.is_zero()) {
- float xf = static_cast<float>(x);
- // Degree-3 minimax polynomial generated by Sollya with the following
- // commands:
- // > display = hexadecimal;
- // > P = fpminimax(expm1(x)/x, 2, [|SG...|], [-2^-7, 2^-7]);
- // > 1 + x * P;
- // 0x1p0 + x * (0x1p0 + x * (0x1.00004p-1 + x * 0x1.555578p-3))
- return fputil::cast<bfloat16>(
- fputil::polyeval(xf, 0x1p+0f, 0x1p+0f, 0x1.0004p-1f, 0x1.555778p-3f));
- }
-
- // exp(0) = 1
- if (x_bits.is_zero())
- return bfloat16(1.0f);
- }
-
- if (auto r = EXPBF16_EXCEPTS.lookup(x_u); LIBC_UNLIKELY(r.has_value()))
- return r.value();
-
- // For -93 < x < 89, we do the following range reduction:
- // x = hi + mid + lo
- // where,
- // hi is an integer
- // mid * 2^2 is an integer
- // -2^3 <= lo <= 2^3
- // also, hi + mid = round(4 * x) / x
- // then,
- // exp(x) = exp(hi + mid + lo)
- // = exp(hi) * exp(mid) * exp(lo)
- // we store 184/8 + 1 = 24 values for looking up exp(hi)
- // from -96 to 88
- // we store 8*4 = 32 values for looking up exp(mid) since
- // mid will always have the bit pattern |bbb.bb| where
- // b can be either 0 or 1
-
- float xf = static_cast<float>(x);
- float kf = fputil::nearest_integer(xf * 4.0f);
- int x_hi_mid = static_cast<int>(kf);
- int x_hi = x_hi_mid >> 5;
- int x_mid = x_hi_mid & 0b11111;
- // lo = x - (hi + mid) = round(x * 4) / (-4) + x
- float lo = fputil::multiply_add(kf, -0.25f, xf);
-
- float exp_hi = EXP_HI[x_hi + 12];
- float exp_mid = EXP_MID[x_mid];
-
- // Degree-3 minimax polynomial generated by Sollya with the following
- // commands:
- // > display = hexadecimal;
- // > P = fpminimax(expm1(x)/x, 2, [|SG...|], [-2^-7, 2^-7]);
- // > 1 + x * P;
- // 0x1p0 + x * (0x1p0 + x * (0x1.00004p-1 + x * 0x1.555578p-3))
- float exp_lo =
- fputil::polyeval(lo, 0x1p+0f, 0x1p+0f, 0x1.0004p-1f, 0x1.555778p-3f);
-
- return fputil::cast<bfloat16>(exp_hi * exp_mid * exp_lo);
-}
-
-} // namespace LIBC_NAMESPACE_DECL
+LLVM_LIBC_FUNCTION(bfloat16, expbf16, (bfloat16 x)) { return math::expbf16(x); }
>From 10a38c3f4e2902734b1a9f98c98efcb32c79b8df Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Thu, 18 Jun 2026 18:27:27 +0530
Subject: [PATCH 11/20] chore: add shared math tests for expbf16
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
libc/src/math/generic/expbf16.cpp | 3 +++
libc/test/shared/CMakeLists.txt | 1 +
libc/test/shared/shared_math_test.cpp | 1 +
3 files changed, 5 insertions(+)
diff --git a/libc/src/math/generic/expbf16.cpp b/libc/src/math/generic/expbf16.cpp
index ba48185d9864e..9f946b8d1ac4e 100644
--- a/libc/src/math/generic/expbf16.cpp
+++ b/libc/src/math/generic/expbf16.cpp
@@ -10,4 +10,7 @@
#include "src/math/expbf16.h"
namespace LIBC_NAMESPACE_DECL {
+
LLVM_LIBC_FUNCTION(bfloat16, expbf16, (bfloat16 x)) { return math::expbf16(x); }
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/test/shared/CMakeLists.txt b/libc/test/shared/CMakeLists.txt
index 17e1570f1b19a..529b00a58097b 100644
--- a/libc/test/shared/CMakeLists.txt
+++ b/libc/test/shared/CMakeLists.txt
@@ -125,6 +125,7 @@ add_fp_unittest(
libc.src.__support.math.exp10f
libc.src.__support.math.exp10f16
libc.src.__support.math.expf
+ libc.src.__support.math.expbf16
libc.src.__support.math.expf16
libc.src.__support.math.f16add
libc.src.__support.math.f16addf
diff --git a/libc/test/shared/shared_math_test.cpp b/libc/test/shared/shared_math_test.cpp
index e26532773c69b..cafaf83f42766 100644
--- a/libc/test/shared/shared_math_test.cpp
+++ b/libc/test/shared/shared_math_test.cpp
@@ -802,6 +802,7 @@ TEST(LlvmLibcSharedMathTest, AllBFloat16) {
bfloat16(0.0)));
EXPECT_FP_EQ(bfloat16(0.0), setpayloadsigbf16_res);
+ EXPECT_FP_EQ(bfloat16(1.0), LIBC_NAMESPACE::shared::expbf16(bfloat16(0.0)));
EXPECT_FP_EQ(bfloat16(0.0), LIBC_NAMESPACE::shared::log_bf16(bfloat16(1.0)));
bfloat16 neg_min_denormal = FPBits::min_subnormal(Sign::NEG).get_val();
>From 62170843ae8e1423b09e635a5ebb7f41f57c384d Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Thu, 25 Jun 2026 14:00:50 +0530
Subject: [PATCH 12/20] chore: address changes
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
libc/src/__support/math/CMakeLists.txt | 4 +++-
libc/src/__support/math/expbf16.h | 21 ++++++++++++---------
2 files changed, 15 insertions(+), 10 deletions(-)
diff --git a/libc/src/__support/math/CMakeLists.txt b/libc/src/__support/math/CMakeLists.txt
index 4c57f8333cc5c..1fcf801f4afab 100644
--- a/libc/src/__support/math/CMakeLists.txt
+++ b/libc/src/__support/math/CMakeLists.txt
@@ -3134,6 +3134,7 @@ add_header_library(
libc.hdr.errno_macros
libc.hdr.fenv_macros
libc.src.__support.CPP.array
+ libc.src.__support.FPUtil.bfloat16
libc.src.__support.FPUtil.cast
libc.src.__support.FPUtil.except_value_utils
libc.src.__support.FPUtil.fenv_impl
@@ -3142,7 +3143,8 @@ add_header_library(
libc.src.__support.FPUtil.nearest_integer
libc.src.__support.FPUtil.polyeval
libc.src.__support.FPUtil.rounding_mode
- libc.src.__support.FPUtil.bfloat16
+ libc.src.__support.macros.config
+ libc.src.__support.macros.properties.types
libc.src.__support.macros.optimization
)
diff --git a/libc/src/__support/math/expbf16.h b/libc/src/__support/math/expbf16.h
index b9a6f7689de1b..d21680a60eabd 100644
--- a/libc/src/__support/math/expbf16.h
+++ b/libc/src/__support/math/expbf16.h
@@ -10,7 +10,6 @@
#define LLVM_LIBC_SRC___SUPPORT_MATH_EXPBF16_H
#include "hdr/errno_macros.h"
-#include "hdr/fenv_macros.h"
#include "src/__support/FPUtil/FEnvImpl.h"
#include "src/__support/FPUtil/FPBits.h"
#include "src/__support/FPUtil/PolyEval.h"
@@ -20,7 +19,6 @@
#include "src/__support/FPUtil/multiply_add.h"
#include "src/__support/FPUtil/nearest_integer.h"
#include "src/__support/FPUtil/rounding_mode.h"
-#include "src/__support/common.h"
#include "src/__support/macros/config.h"
#include "src/__support/macros/optimization.h"
#include "src/__support/macros/properties/types.h"
@@ -31,6 +29,8 @@ namespace LIBC_NAMESPACE_DECL {
namespace math {
+namespace expbf16_internal {
+
// Generated by Sollya with the following commands:
// > display = hexadecimal;
// > for i from -96 to 88 by 8 do print(i, round(exp(i), SG, RN) @ "f,");
@@ -57,6 +57,8 @@ LIBC_INLINE_VAR constexpr float EXP_MID[32] = {
0x1.122886p10f, 0x1.6006b6p10f, 0x1.c402b6p10f, 0x1.223252p11f,
};
+} // namespace expbf16_internal
+
LIBC_INLINE bfloat16 expbf16(bfloat16 x) {
using FPBits = fputil::FPBits<bfloat16>;
FPBits x_bits(x);
@@ -114,8 +116,12 @@ LIBC_INLINE bfloat16 expbf16(bfloat16 x) {
}
}
+ // exp(0) = 1
+ if (x_bits.is_zero())
+ return bfloat16(1.0f);
+
// 0 < |x| <= 2^(-3)
- if (x_abs <= 0x3e00U && !x_bits.is_zero()) {
+ if (x_abs <= 0x3e00U) {
float xf = static_cast<float>(x);
// Degree-3 minimax polynomial generated by Sollya with the following
// commands:
@@ -126,10 +132,6 @@ LIBC_INLINE bfloat16 expbf16(bfloat16 x) {
return fputil::cast<bfloat16>(
fputil::polyeval(xf, 0x1p+0f, 0x1p+0f, 0x1.0004p-1f, 0x1.555778p-3f));
}
-
- // exp(0) = 1
- if (x_bits.is_zero())
- return bfloat16(1.0f);
}
constexpr fputil::ExceptValues<bfloat16, 4> EXPBF16_EXCEPTS = {{
@@ -174,8 +176,8 @@ LIBC_INLINE bfloat16 expbf16(bfloat16 x) {
// lo = x - (hi + mid) = round(x * 4) / (-4) + x
float lo = fputil::multiply_add(kf, -0.25f, xf);
- float exp_hi = EXP_HI[x_hi + 12];
- float exp_mid = EXP_MID[x_mid];
+ float exp_hi = expbf16_internal::EXP_HI[x_hi + 12];
+ float exp_mid = expbf16_internal::EXP_MID[x_mid];
// Degree-3 minimax polynomial generated by Sollya with the following
// commands:
@@ -188,6 +190,7 @@ LIBC_INLINE bfloat16 expbf16(bfloat16 x) {
return fputil::cast<bfloat16>(exp_hi * exp_mid * exp_lo);
}
+
} // namespace math
} // namespace LIBC_NAMESPACE_DECL
>From 85722055f7f08ca47e36fb257a4842b810a92b9a Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Thu, 25 Jun 2026 14:07:01 +0530
Subject: [PATCH 13/20] chore: make use of macros
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
libc/src/__support/math/expbf16.h | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/libc/src/__support/math/expbf16.h b/libc/src/__support/math/expbf16.h
index d21680a60eabd..6cd54f61454fb 100644
--- a/libc/src/__support/math/expbf16.h
+++ b/libc/src/__support/math/expbf16.h
@@ -85,6 +85,11 @@ LIBC_INLINE bfloat16 expbf16(bfloat16 x) {
if (x_bits.is_inf())
return x;
+#ifdef LIBC_MATH_HAS_ASSUME_ROUND_NEAREST_ONLY
+ fputil::set_errno_if_required(ERANGE);
+ fputil::raise_except_if_required(FE_OVERFLOW);
+ return FPBits::inf().get_val();
+#else
switch (fputil::quick_get_round()) {
case FE_TONEAREST:
case FE_UPWARD:
@@ -94,6 +99,7 @@ LIBC_INLINE bfloat16 expbf16(bfloat16 x) {
default:
return FPBits::max_normal().get_val();
}
+#endif // LIBC_MATH_HAS_ASSUME_ROUND_NEAREST_ONLY
}
// x <= -92.5
@@ -105,6 +111,9 @@ LIBC_INLINE bfloat16 expbf16(bfloat16 x) {
fputil::set_errno_if_required(ERANGE);
fputil::raise_except_if_required(FE_UNDERFLOW | FE_INEXACT);
+#ifdef LIBC_MATH_HAS_ASSUME_ROUND_NEAREST_ONLY
+ return FPBits::zero().get_val();
+#else
switch (fputil::quick_get_round()) {
case FE_UPWARD:
case FE_TONEAREST:
@@ -114,6 +123,7 @@ LIBC_INLINE bfloat16 expbf16(bfloat16 x) {
default:
return FPBits::zero().get_val();
}
+#endif // LIBC_MATH_HAS_ASSUME_ROUND_NEAREST_ONLY
}
// exp(0) = 1
@@ -134,6 +144,7 @@ LIBC_INLINE bfloat16 expbf16(bfloat16 x) {
}
}
+#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
constexpr fputil::ExceptValues<bfloat16, 4> EXPBF16_EXCEPTS = {{
// (input, RZ output, RU offset, RD offset, RN offset)
// x = 0x40DB (6.84375)
@@ -151,6 +162,7 @@ LIBC_INLINE bfloat16 expbf16(bfloat16 x) {
if (auto r = EXPBF16_EXCEPTS.lookup(x_u); LIBC_UNLIKELY(r.has_value()))
return r.value();
+#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
// For -93 < x < 89, we do the following range reduction:
// x = hi + mid + lo
>From 4a733dc395c5ae1ee3e77716b6fe8d282f8ef090 Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Thu, 25 Jun 2026 15:07:05 +0530
Subject: [PATCH 14/20] chore: address more changes
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
libc/src/__support/math/expbf16.h | 3 +-
libc/src/math/generic/CMakeLists.txt | 14 +--
libc/test/src/math/smoke/expbf16_test.cpp | 104 ++++++++++++----------
3 files changed, 57 insertions(+), 64 deletions(-)
diff --git a/libc/src/__support/math/expbf16.h b/libc/src/__support/math/expbf16.h
index 6cd54f61454fb..eaef906b05410 100644
--- a/libc/src/__support/math/expbf16.h
+++ b/libc/src/__support/math/expbf16.h
@@ -10,6 +10,7 @@
#define LLVM_LIBC_SRC___SUPPORT_MATH_EXPBF16_H
#include "hdr/errno_macros.h"
+#include "hdr/fenv_macros.h"
#include "src/__support/FPUtil/FEnvImpl.h"
#include "src/__support/FPUtil/FPBits.h"
#include "src/__support/FPUtil/PolyEval.h"
@@ -23,8 +24,6 @@
#include "src/__support/macros/optimization.h"
#include "src/__support/macros/properties/types.h"
-// bfloat16 expbf16(bfloat16 x);
-
namespace LIBC_NAMESPACE_DECL {
namespace math {
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index 9dbcc0989b580..01465f599e930 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -1238,19 +1238,7 @@ add_entrypoint_object(
HDRS
../expbf16.h
DEPENDS
- libc.hdr.errno_macros
- libc.hdr.fenv_macros
- libc.src.__support.CPP.array
- libc.src.__support.FPUtil.cast
- libc.src.__support.FPUtil.except_value_utils
- libc.src.__support.FPUtil.fenv_impl
- libc.src.__support.FPUtil.fp_bits
- libc.src.__support.FPUtil.multiply_add
- libc.src.__support.FPUtil.nearest_integer
- libc.src.__support.FPUtil.polyeval
- libc.src.__support.FPUtil.rounding_mode
- libc.src.__support.FPUtil.bfloat16
- libc.src.__support.macros.optimization
+ libc.src.__support.math.expbf16
)
add_entrypoint_object(
diff --git a/libc/test/src/math/smoke/expbf16_test.cpp b/libc/test/src/math/smoke/expbf16_test.cpp
index cc501571383e3..04526bebc4685 100644
--- a/libc/test/src/math/smoke/expbf16_test.cpp
+++ b/libc/test/src/math/smoke/expbf16_test.cpp
@@ -11,53 +11,59 @@
#include "src/__support/FPUtil/bfloat16.h"
#include "src/__support/FPUtil/cast.h"
#include "src/math/expbf16.h"
+#include "test/UnitTest/FEnvSafeTest.h"
#include "test/UnitTest/FPMatcher.h"
-#include "test/UnitTest/Test.h"
-
-using LlvmLibcExpf16Test = LIBC_NAMESPACE::testing::FPTest<bfloat16>;
-
-TEST_F(LlvmLibcExpf16Test, SpecialNumbers) {
- EXPECT_FP_IS_NAN(LIBC_NAMESPACE::expbf16(aNaN));
- EXPECT_MATH_ERRNO(0);
-
- EXPECT_FP_IS_NAN_WITH_EXCEPTION(LIBC_NAMESPACE::expbf16(sNaN), FE_INVALID);
- EXPECT_MATH_ERRNO(0);
-
- EXPECT_FP_EQ_ALL_ROUNDING(inf, LIBC_NAMESPACE::expbf16(inf));
- EXPECT_MATH_ERRNO(0);
-
- EXPECT_FP_EQ_ALL_ROUNDING(zero, LIBC_NAMESPACE::expbf16(neg_inf));
- EXPECT_MATH_ERRNO(0);
-
- EXPECT_FP_EQ_ALL_ROUNDING(LIBC_NAMESPACE::fputil::cast<bfloat16>(1.0f),
- LIBC_NAMESPACE::expbf16(zero));
- EXPECT_MATH_ERRNO(0);
-
- EXPECT_FP_EQ_ALL_ROUNDING(LIBC_NAMESPACE::fputil::cast<bfloat16>(1.0f),
- LIBC_NAMESPACE::expbf16(neg_zero));
- EXPECT_MATH_ERRNO(0);
-}
-
-TEST_F(LlvmLibcExpf16Test, Overflow) {
- EXPECT_FP_EQ_WITH_EXCEPTION(inf, LIBC_NAMESPACE::expbf16(max_normal),
- FE_OVERFLOW);
- EXPECT_MATH_ERRNO(ERANGE);
-
- EXPECT_FP_EQ_WITH_EXCEPTION(
- inf,
- LIBC_NAMESPACE::expbf16(LIBC_NAMESPACE::fputil::cast<bfloat16>(89.0f)),
- FE_OVERFLOW);
- EXPECT_MATH_ERRNO(ERANGE);
-}
-
-TEST_F(LlvmLibcExpf16Test, Underflow) {
- EXPECT_FP_EQ_WITH_EXCEPTION(zero, LIBC_NAMESPACE::expbf16(neg_max_normal),
- FE_UNDERFLOW | FE_INEXACT);
- EXPECT_MATH_ERRNO(ERANGE);
-
- EXPECT_FP_EQ_WITH_EXCEPTION(
- zero,
- LIBC_NAMESPACE::expbf16(LIBC_NAMESPACE::fputil::cast<bfloat16>(-93.0f)),
- FE_UNDERFLOW | FE_INEXACT);
- EXPECT_MATH_ERRNO(ERANGE);
-}
+
+class LlvmLibcExpf16Test : public LIBC_NAMESPACE::testing::FEnvSafeTest {
+ DECLARE_SPECIAL_CONSTANTS(bfloat16)
+public:
+ void test_special_numbers() {
+ EXPECT_FP_IS_NAN(LIBC_NAMESPACE::expbf16(aNaN));
+ EXPECT_MATH_ERRNO(0);
+
+ EXPECT_FP_IS_NAN_WITH_EXCEPTION(LIBC_NAMESPACE::expbf16(sNaN), FE_INVALID);
+ EXPECT_MATH_ERRNO(0);
+
+ EXPECT_FP_EQ_ALL_ROUNDING(inf, LIBC_NAMESPACE::expbf16(inf));
+ EXPECT_MATH_ERRNO(0);
+
+ EXPECT_FP_EQ_ALL_ROUNDING(zero, LIBC_NAMESPACE::expbf16(neg_inf));
+ EXPECT_MATH_ERRNO(0);
+
+ EXPECT_FP_EQ_ALL_ROUNDING(LIBC_NAMESPACE::fputil::cast<bfloat16>(1.0f),
+ LIBC_NAMESPACE::expbf16(zero));
+ EXPECT_MATH_ERRNO(0);
+
+ EXPECT_FP_EQ_ALL_ROUNDING(LIBC_NAMESPACE::fputil::cast<bfloat16>(1.0f),
+ LIBC_NAMESPACE::expbf16(neg_zero));
+ EXPECT_MATH_ERRNO(0);
+ }
+
+ void test_overflow() {
+ EXPECT_FP_EQ_WITH_EXCEPTION(inf, LIBC_NAMESPACE::expbf16(max_normal),
+ FE_OVERFLOW);
+ EXPECT_MATH_ERRNO(ERANGE);
+
+ EXPECT_FP_EQ_WITH_EXCEPTION(
+ inf,
+ LIBC_NAMESPACE::expbf16(LIBC_NAMESPACE::fputil::cast<bfloat16>(89.0f)),
+ FE_OVERFLOW);
+ EXPECT_MATH_ERRNO(ERANGE);
+ }
+
+ void test_underflow() {
+ EXPECT_FP_EQ_WITH_EXCEPTION(zero, LIBC_NAMESPACE::expbf16(neg_max_normal),
+ FE_UNDERFLOW | FE_INEXACT);
+ EXPECT_MATH_ERRNO(ERANGE);
+
+ EXPECT_FP_EQ_WITH_EXCEPTION(
+ zero,
+ LIBC_NAMESPACE::expbf16(LIBC_NAMESPACE::fputil::cast<bfloat16>(-93.0f)),
+ FE_UNDERFLOW | FE_INEXACT);
+ EXPECT_MATH_ERRNO(ERANGE);
+ }
+};
+
+TEST_F(LlvmLibcExpf16Test, SpecialNumbers) { test_special_numbers(); }
+TEST_F(LlvmLibcExpf16Test, Overflow) { test_overflow(); }
+TEST_F(LlvmLibcExpf16Test, Undeflow) { test_underflow(); }
>From a0e220f34c5157f6baf0e62af1b88afc4e802bf3 Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Thu, 25 Jun 2026 15:18:52 +0530
Subject: [PATCH 15/20] chore: nit, freebsd entrypoint and bazel updates
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
libc/config/freebsd/x86_64/entrypoints.txt | 1 +
libc/src/__support/math/expbf16.h | 2 +-
.../llvm-project-overlay/libc/BUILD.bazel | 22 +++++++++++++++++++
.../libc/test/src/math/BUILD.bazel | 2 ++
.../libc/test/src/math/smoke/BUILD.bazel | 2 ++
5 files changed, 28 insertions(+), 1 deletion(-)
diff --git a/libc/config/freebsd/x86_64/entrypoints.txt b/libc/config/freebsd/x86_64/entrypoints.txt
index b4745d9400335..18b01b76c6bf2 100644
--- a/libc/config/freebsd/x86_64/entrypoints.txt
+++ b/libc/config/freebsd/x86_64/entrypoints.txt
@@ -579,6 +579,7 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
libc.src.math.canonicalizebf16
libc.src.math.ceilbf16
libc.src.math.copysignbf16
+ libc.src.math.expbf16
libc.src.math.fabsbf16
libc.src.math.fdimbf16
libc.src.math.floorbf16
diff --git a/libc/src/__support/math/expbf16.h b/libc/src/__support/math/expbf16.h
index eaef906b05410..77006a8ad3440 100644
--- a/libc/src/__support/math/expbf16.h
+++ b/libc/src/__support/math/expbf16.h
@@ -197,7 +197,7 @@ LIBC_INLINE bfloat16 expbf16(bfloat16 x) {
// > 1 + x * P;
// 0x1p0 + x * (0x1p0 + x * (0x1.00004p-1 + x * 0x1.555578p-3))
float exp_lo =
- fputil::polyeval(lo, 0x1p+0f, 0x1p+0f, 0x1.0004p-1f, 0x1.555778p-3f);
+ fputil::polyeval(lo, 0x1p+0f, 0x1p+0f, 0x1.00004p-1f, 0x1.555578p-3f);
return fputil::cast<bfloat16>(exp_hi * exp_mid * exp_lo);
}
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index fd71a06b382d8..bf25a3757738b 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -6907,6 +6907,28 @@ libc_support_library(
],
)
+libc_support_library(
+ name = "__support_math_expbf16",
+ hdrs = ["src/__support/math/expbf16.h"],
+ deps = [
+ ":hdr_errno_macros",
+ ":hdr_fenv_macros",
+ ":__support_cpp_array",
+ ":__support_fputil_bfloat16",
+ ":__support_fputil_cast",
+ ":__support_fputil_except_value_utils",
+ ":__support_fputil_fenv_impl",
+ ":__support_fputil_fp_bits",
+ ":__support_fputil_multiply_add",
+ ":__support_fputil_nearest_integer",
+ ":__support_fputil_polyeval",
+ ":__support_fputil_rounding_mode",
+ ":__support_macros_config",
+ ":__support_macros_properties_types",
+ ":__support_macros_optimization",
+ ],
+)
+
libc_support_library(
name = "__support_math_expxf16_utils",
hdrs = ["src/__support/math/expxf16_utils.h"],
diff --git a/utils/bazel/llvm-project-overlay/libc/test/src/math/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/test/src/math/BUILD.bazel
index a49a852becfb6..ced7b0bddd93f 100644
--- a/utils/bazel/llvm-project-overlay/libc/test/src/math/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/test/src/math/BUILD.bazel
@@ -623,6 +623,8 @@ math_mpfr_test(name = "tanpif16")
math_mpfr_test(name = "expf16")
+math_mpfr_test(name = "expbf16")
+
math_mpfr_test(name = "exp2f16")
math_mpfr_test(name = "exp2m1f16")
diff --git a/utils/bazel/llvm-project-overlay/libc/test/src/math/smoke/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/test/src/math/smoke/BUILD.bazel
index c4281d3993afb..a8d344351cfb7 100644
--- a/utils/bazel/llvm-project-overlay/libc/test/src/math/smoke/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/test/src/math/smoke/BUILD.bazel
@@ -1696,6 +1696,8 @@ math_test(name = "exp2m1f16")
math_test(name = "expf16")
+math_test(name = "expbf16")
+
math_test(name = "expm1f16")
math_test(
>From cbe190c69318dfc7c785d3754a77044c87a949a0 Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Thu, 25 Jun 2026 15:23:55 +0530
Subject: [PATCH 16/20] fix: bazel
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
utils/bazel/llvm-project-overlay/libc/BUILD.bazel | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index bf25a3757738b..b1695e935e061 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -6911,8 +6911,6 @@ libc_support_library(
name = "__support_math_expbf16",
hdrs = ["src/__support/math/expbf16.h"],
deps = [
- ":hdr_errno_macros",
- ":hdr_fenv_macros",
":__support_cpp_array",
":__support_fputil_bfloat16",
":__support_fputil_cast",
@@ -6924,8 +6922,10 @@ libc_support_library(
":__support_fputil_polyeval",
":__support_fputil_rounding_mode",
":__support_macros_config",
- ":__support_macros_properties_types",
":__support_macros_optimization",
+ ":__support_macros_properties_types",
+ ":hdr_errno_macros",
+ ":hdr_fenv_macros",
],
)
>From 21ad61d52d84a6ffe6301d3a1ee131f215b83faf Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Thu, 25 Jun 2026 15:32:19 +0530
Subject: [PATCH 17/20] nit: match polyeval args with sollya
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
libc/src/__support/math/expbf16.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/libc/src/__support/math/expbf16.h b/libc/src/__support/math/expbf16.h
index 77006a8ad3440..5fdde6d6204f7 100644
--- a/libc/src/__support/math/expbf16.h
+++ b/libc/src/__support/math/expbf16.h
@@ -138,8 +138,8 @@ LIBC_INLINE bfloat16 expbf16(bfloat16 x) {
// > P = fpminimax(expm1(x)/x, 2, [|SG...|], [-2^-7, 2^-7]);
// > 1 + x * P;
// 0x1p0 + x * (0x1p0 + x * (0x1.00004p-1 + x * 0x1.555578p-3))
- return fputil::cast<bfloat16>(
- fputil::polyeval(xf, 0x1p+0f, 0x1p+0f, 0x1.0004p-1f, 0x1.555778p-3f));
+ return fputil::cast<bfloat16>(fputil::polyeval(
+ xf, 0x1p+0f, 0x1p+0f, 0x1.00004p-1f, 0x1.555578p-3f));
}
}
>From f015cca4c42cdcaa19ac6484cbc514f687b0f243 Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Thu, 25 Jun 2026 15:45:44 +0530
Subject: [PATCH 18/20] fix: bazel
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
utils/bazel/llvm-project-overlay/libc/BUILD.bazel | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index b1695e935e061..2fb1552e811cd 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -10573,6 +10573,13 @@ libc_math_function(
],
)
+libc_math_function(
+ name = "expbf16",
+ additional_deps = [
+ ":__support_math_expbf16",
+ ],
+)
+
libc_math_function(
name = "exp10",
additional_deps = [
>From 95077d2b086a59319df1705def382394a8a12fa4 Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Thu, 25 Jun 2026 10:36:33 +0000
Subject: [PATCH 19/20] Update libc/src/__support/math/CMakeLists.txt
Co-authored-by: Zorojuro <sawantsukumar at gmail.com>
---
libc/src/__support/math/CMakeLists.txt | 1 -
1 file changed, 1 deletion(-)
diff --git a/libc/src/__support/math/CMakeLists.txt b/libc/src/__support/math/CMakeLists.txt
index 1fcf801f4afab..d4c51208514da 100644
--- a/libc/src/__support/math/CMakeLists.txt
+++ b/libc/src/__support/math/CMakeLists.txt
@@ -3125,7 +3125,6 @@ add_header_library(
libc.src.__support.math.exp10_float16_constants
)
-
add_header_library(
expbf16
HDRS
>From 7a60688be600c515ed605cda5ce131f5d20c9bc9 Mon Sep 17 00:00:00 2001
From: Krishna Pandey <kpandey81930 at gmail.com>
Date: Thu, 25 Jun 2026 16:33:17 +0530
Subject: [PATCH 20/20] fix: bfloat16 bazel
Signed-off-by: Krishna Pandey <kpandey81930 at gmail.com>
---
.../llvm-project-overlay/libc/test/src/math/BUILD.bazel | 7 ++++++-
.../libc/test/src/math/smoke/BUILD.bazel | 7 ++++++-
2 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/utils/bazel/llvm-project-overlay/libc/test/src/math/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/test/src/math/BUILD.bazel
index ced7b0bddd93f..9b5fa61303f10 100644
--- a/utils/bazel/llvm-project-overlay/libc/test/src/math/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/test/src/math/BUILD.bazel
@@ -623,7 +623,12 @@ math_mpfr_test(name = "tanpif16")
math_mpfr_test(name = "expf16")
-math_mpfr_test(name = "expbf16")
+math_mpfr_test(
+ name = "expbf16",
+ deps = [
+ "//libc:__support_fputil_bfloat16",
+ ],
+)
math_mpfr_test(name = "exp2f16")
diff --git a/utils/bazel/llvm-project-overlay/libc/test/src/math/smoke/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/test/src/math/smoke/BUILD.bazel
index a8d344351cfb7..3f0874110e140 100644
--- a/utils/bazel/llvm-project-overlay/libc/test/src/math/smoke/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/test/src/math/smoke/BUILD.bazel
@@ -1696,7 +1696,12 @@ math_test(name = "exp2m1f16")
math_test(name = "expf16")
-math_test(name = "expbf16")
+math_test(
+ name = "expbf16",
+ deps = [
+ "//libc:__support_fputil_bfloat16",
+ ],
+)
math_test(name = "expm1f16")
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