[libc][math][c++23] Add next{after,down,toward,up}bf16 math functions (#153993)

krishna2803 · overmighty · web-flow · commit eac19d46d8e0 · 2025-08-22T22:01:49.000+05:30
This PR adds the following basic math functions for BFloat16 type along
with the tests:
- nextafterbf16
- nextdownbf16
- nexttowardbf16
- nextupbf16

---------

Signed-off-by: Krishna Pandey &lt;kpandey81930@gmail.com&gt;
Co-authored-by: OverMighty &lt;its.overmighty@gmail.com&gt;
diff --git a/libc/config/baremetal/aarch64/entrypoints.txt b/libc/config/baremetal/aarch64/entrypoints.txt
@@ -787,6 +787,10 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.fminimum_numbf16
   libc.src.math.fromfpbf16
   libc.src.math.fromfpxbf16
+  libc.src.math.nextafterbf16
+  libc.src.math.nextdownbf16
+  libc.src.math.nexttowardbf16
+  libc.src.math.nextupbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
   libc.src.math.truncbf16
diff --git a/libc/config/baremetal/arm/entrypoints.txt b/libc/config/baremetal/arm/entrypoints.txt
@@ -790,6 +790,10 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.fminimum_numbf16
   libc.src.math.fromfpbf16
   libc.src.math.fromfpxbf16
+  libc.src.math.nextafterbf16
+  libc.src.math.nextdownbf16
+  libc.src.math.nexttowardbf16
+  libc.src.math.nextupbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
   libc.src.math.truncbf16
diff --git a/libc/config/baremetal/riscv/entrypoints.txt b/libc/config/baremetal/riscv/entrypoints.txt
@@ -790,6 +790,10 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.fminimum_numbf16
   libc.src.math.fromfpbf16
   libc.src.math.fromfpxbf16
+  libc.src.math.nextafterbf16
+  libc.src.math.nextdownbf16
+  libc.src.math.nexttowardbf16
+  libc.src.math.nextupbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
   libc.src.math.truncbf16
diff --git a/libc/config/darwin/aarch64/entrypoints.txt b/libc/config/darwin/aarch64/entrypoints.txt
@@ -620,6 +620,10 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.fminimum_numbf16
   libc.src.math.fromfpbf16
   libc.src.math.fromfpxbf16
+  libc.src.math.nextafterbf16
+  libc.src.math.nextdownbf16
+  libc.src.math.nexttowardbf16
+  libc.src.math.nextupbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
   libc.src.math.truncbf16
diff --git a/libc/config/darwin/x86_64/entrypoints.txt b/libc/config/darwin/x86_64/entrypoints.txt
@@ -263,6 +263,10 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.fminimum_numbf16
   libc.src.math.fromfpbf16
   libc.src.math.fromfpxbf16
+  libc.src.math.nextafterbf16
+  libc.src.math.nextdownbf16
+  libc.src.math.nexttowardbf16
+  libc.src.math.nextupbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
   libc.src.math.truncbf16
diff --git a/libc/config/gpu/amdgpu/entrypoints.txt b/libc/config/gpu/amdgpu/entrypoints.txt
@@ -646,6 +646,10 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.fminimum_numbf16
   libc.src.math.fromfpbf16
   libc.src.math.fromfpxbf16
+  libc.src.math.nextafterbf16
+  libc.src.math.nextdownbf16
+  libc.src.math.nexttowardbf16
+  libc.src.math.nextupbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
   libc.src.math.truncbf16
diff --git a/libc/config/gpu/nvptx/entrypoints.txt b/libc/config/gpu/nvptx/entrypoints.txt
@@ -648,6 +648,10 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.fminimum_numbf16
   libc.src.math.fromfpbf16
   libc.src.math.fromfpxbf16
+  libc.src.math.nextafterbf16
+  libc.src.math.nextdownbf16
+  libc.src.math.nexttowardbf16
+  libc.src.math.nextupbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
   libc.src.math.truncbf16
diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
@@ -875,6 +875,10 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.fminimum_numbf16
   libc.src.math.fromfpbf16
   libc.src.math.fromfpxbf16
+  libc.src.math.nextafterbf16
+  libc.src.math.nextdownbf16
+  libc.src.math.nexttowardbf16
+  libc.src.math.nextupbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
   libc.src.math.truncbf16
diff --git a/libc/config/linux/arm/entrypoints.txt b/libc/config/linux/arm/entrypoints.txt
@@ -490,6 +490,10 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.fminimum_numbf16
   libc.src.math.fromfpbf16
   libc.src.math.fromfpxbf16
+  libc.src.math.nextafterbf16
+  libc.src.math.nextdownbf16
+  libc.src.math.nexttowardbf16
+  libc.src.math.nextupbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
   libc.src.math.truncbf16
diff --git a/libc/config/linux/riscv/entrypoints.txt b/libc/config/linux/riscv/entrypoints.txt
@@ -893,6 +893,9 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.fminimum_numbf16
   libc.src.math.fromfpbf16
   libc.src.math.fromfpxbf16
+  libc.src.math.nextafterbf16
+  libc.src.math.nextdownbf16
+  libc.src.math.nexttowardbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
   libc.src.math.truncbf16
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
@@ -926,6 +926,10 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.fminimum_numbf16
   libc.src.math.fromfpbf16
   libc.src.math.fromfpxbf16
+  libc.src.math.nextafterbf16
+  libc.src.math.nextdownbf16
+  libc.src.math.nexttowardbf16
+  libc.src.math.nextupbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
   libc.src.math.truncbf16
diff --git a/libc/config/windows/entrypoints.txt b/libc/config/windows/entrypoints.txt
@@ -336,6 +336,10 @@ list(APPEND TARGET_LIBM_ENTRYPOINTS
   libc.src.math.fminimum_numbf16
   libc.src.math.fromfpbf16
   libc.src.math.fromfpxbf16
+  libc.src.math.nextafterbf16
+  libc.src.math.nextdownbf16
+  libc.src.math.nexttowardbf16
+  libc.src.math.nextupbf16
   libc.src.math.roundbf16
   libc.src.math.roundevenbf16
   libc.src.math.truncbf16
diff --git a/libc/docs/headers/math/index.rst b/libc/docs/headers/math/index.rst
@@ -215,13 +215,13 @@ Basic Operations
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
 | nearbyint        | |check|          | |check|         | |check|                | |check|              | |check|                |                        | 7.12.9.3               | F.10.6.3                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
-| nextafter        | |check|          | |check|         | |check|                | |check|              | |check|                |                        | 7.12.11.3              | F.10.8.3                   |
+| nextafter        | |check|          | |check|         | |check|                | |check|              | |check|                | |check|                | 7.12.11.3              | F.10.8.3                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
-| nextdown         | |check|          | |check|         | |check|                | |check|              | |check|                |                        | 7.12.11.6              | F.10.8.6                   |
+| nextdown         | |check|          | |check|         | |check|                | |check|              | |check|                | |check|                | 7.12.11.6              | F.10.8.6                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
-| nexttoward       | |check|          | |check|         | |check|                | |check|              | N/A                    |                        | 7.12.11.4              | F.10.8.4                   |
+| nexttoward       | |check|          | |check|         | |check|                | |check|              | N/A                    | |check|                | 7.12.11.4              | F.10.8.4                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
-| nextup           | |check|          | |check|         | |check|                | |check|              | |check|                |                        | 7.12.11.5              | F.10.8.5                   |
+| nextup           | |check|          | |check|         | |check|                | |check|              | |check|                | |check|                | 7.12.11.5              | F.10.8.5                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
 | remainder        | |check|          | |check|         | |check|                | |check|              | |check|                |                        | 7.12.10.2              | F.10.7.2                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
diff --git a/libc/src/math/CMakeLists.txt b/libc/src/math/CMakeLists.txt
@@ -433,23 +433,27 @@ add_math_entrypoint_object(nextafterf)
 add_math_entrypoint_object(nextafterl)
 add_math_entrypoint_object(nextafterf16)
 add_math_entrypoint_object(nextafterf128)
+add_math_entrypoint_object(nextafterbf16)
 
 add_math_entrypoint_object(nexttoward)
 add_math_entrypoint_object(nexttowardf)
 add_math_entrypoint_object(nexttowardl)
 add_math_entrypoint_object(nexttowardf16)
+add_math_entrypoint_object(nexttowardbf16)
 
 add_math_entrypoint_object(nextdown)
 add_math_entrypoint_object(nextdownf)
 add_math_entrypoint_object(nextdownl)
 add_math_entrypoint_object(nextdownf16)
 add_math_entrypoint_object(nextdownf128)
+add_math_entrypoint_object(nextdownbf16)
 
 add_math_entrypoint_object(nextup)
 add_math_entrypoint_object(nextupf)
 add_math_entrypoint_object(nextupl)
 add_math_entrypoint_object(nextupf16)
 add_math_entrypoint_object(nextupf128)
+add_math_entrypoint_object(nextupbf16)
 
 add_math_entrypoint_object(pow)
 add_math_entrypoint_object(powf)
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
@@ -3484,6 +3484,20 @@ add_entrypoint_object(
     libc.src.__support.FPUtil.manipulation_functions
 )
 
+add_entrypoint_object(
+  nextafterbf16
+  SRCS
+    nextafterbf16.cpp
+  HDRS
+    ../nextafterbf16.h
+  DEPENDS
+    libc.src.__support.common
+    libc.src.__support.FPUtil.bfloat16
+    libc.src.__support.FPUtil.manipulation_functions
+    libc.src.__support.macros.config
+    libc.src.__support.macros.properties.types
+)
+
 add_entrypoint_object(
   nexttoward
   SRCS
@@ -3525,6 +3539,20 @@ add_entrypoint_object(
     libc.src.__support.FPUtil.manipulation_functions
 )
 
+add_entrypoint_object(
+  nexttowardbf16
+  SRCS
+    nexttowardbf16.cpp
+  HDRS
+    ../nexttowardbf16.h
+  DEPENDS
+    libc.src.__support.common
+    libc.src.__support.FPUtil.bfloat16
+    libc.src.__support.FPUtil.manipulation_functions
+    libc.src.__support.macros.config
+    libc.src.__support.macros.properties.types
+)
+
 add_entrypoint_object(
   nextdown
   SRCS
@@ -3577,6 +3605,20 @@ add_entrypoint_object(
     libc.src.__support.FPUtil.manipulation_functions
 )
 
+add_entrypoint_object(
+  nextdownbf16
+  SRCS
+    nextdownbf16.cpp
+  HDRS
+    ../nextdownbf16.h
+  DEPENDS
+    libc.src.__support.common
+    libc.src.__support.FPUtil.bfloat16
+    libc.src.__support.FPUtil.manipulation_functions
+    libc.src.__support.macros.config
+    libc.src.__support.macros.properties.types
+)
+
 add_entrypoint_object(
   nextup
   SRCS
@@ -3629,6 +3671,20 @@ add_entrypoint_object(
     libc.src.__support.FPUtil.manipulation_functions
 )
 
+add_entrypoint_object(
+  nextupbf16
+  SRCS
+    nextupbf16.cpp
+  HDRS
+    ../nextupbf16.h
+  DEPENDS
+    libc.src.__support.common
+    libc.src.__support.FPUtil.bfloat16
+    libc.src.__support.FPUtil.manipulation_functions
+    libc.src.__support.macros.config
+    libc.src.__support.macros.properties.types
+)
+
 add_entrypoint_object(
   fmod
   SRCS
diff --git a/libc/src/math/generic/nextafterbf16.cpp b/libc/src/math/generic/nextafterbf16.cpp
@@ -0,0 +1,21 @@
+//===-- Implementation of nextafterbf16 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/nextafterbf16.h"
+#include "src/__support/FPUtil/ManipulationFunctions.h"
+#include "src/__support/FPUtil/bfloat16.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(bfloat16, nextafterbf16, (bfloat16 x, bfloat16 y)) {
+  return fputil::nextafter(x, y);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/math/generic/nextdownbf16.cpp b/libc/src/math/generic/nextdownbf16.cpp
@@ -0,0 +1,21 @@
+//===-- Implementation of nextdownbf16 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/nextdownbf16.h"
+#include "src/__support/FPUtil/ManipulationFunctions.h"
+#include "src/__support/FPUtil/bfloat16.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(bfloat16, nextdownbf16, (bfloat16 x)) {
+  return fputil::nextupdown</*IsDown=*/true>(x);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/math/generic/nexttowardbf16.cpp b/libc/src/math/generic/nexttowardbf16.cpp
@@ -0,0 +1,22 @@
+//===-- Implementation of nexttowardbf16 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/nexttowardbf16.h"
+#include "src/__support/FPUtil/ManipulationFunctions.h"
+#include "src/__support/FPUtil/bfloat16.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(bfloat16, nexttowardbf16, (bfloat16 x, long double y)) {
+  // nextafter<T, U> where T != U is nexttoward
+  return fputil::nextafter(x, y);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/math/generic/nextupbf16.cpp b/libc/src/math/generic/nextupbf16.cpp
@@ -0,0 +1,21 @@
+//===-- Implementation of nextupbf16 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/nextupbf16.h"
+#include "src/__support/FPUtil/ManipulationFunctions.h"
+#include "src/__support/FPUtil/bfloat16.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(bfloat16, nextupbf16, (bfloat16 x)) {
+  return fputil::nextupdown</*IsDown=*/false>(x);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/math/nextafterbf16.h b/libc/src/math/nextafterbf16.h
@@ -0,0 +1,21 @@
+//===-- Implementation header for nextafterbf16 -----------------*- 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_NEXTAFTERBF16_H
+#define LLVM_LIBC_SRC_MATH_NEXTAFTERBF16_H
+
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/types.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+bfloat16 nextafterbf16(bfloat16 x, bfloat16 y);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_MATH_NEXTAFTERBF16_H
diff --git a/libc/src/math/nextdownbf16.h b/libc/src/math/nextdownbf16.h
@@ -0,0 +1,21 @@
+//===-- Implementation header for nextdownbf16 ------------------*- 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_NEXTDOWNBF16_H
+#define LLVM_LIBC_SRC_MATH_NEXTDOWNBF16_H
+
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/types.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+bfloat16 nextdownbf16(bfloat16 x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_MATH_NEXTDOWNBF16_H
diff --git a/libc/src/math/nexttowardbf16.h b/libc/src/math/nexttowardbf16.h
diff --git a/libc/src/math/nextupbf16.h b/libc/src/math/nextupbf16.h
diff --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
diff --git a/libc/test/src/math/smoke/NextAfterTest.h b/libc/test/src/math/smoke/NextAfterTest.h
diff --git a/libc/test/src/math/smoke/NextTowardTest.h b/libc/test/src/math/smoke/NextTowardTest.h
diff --git a/libc/test/src/math/smoke/nextafterbf16_test.cpp b/libc/test/src/math/smoke/nextafterbf16_test.cpp
diff --git a/libc/test/src/math/smoke/nextdownbf16_test.cpp b/libc/test/src/math/smoke/nextdownbf16_test.cpp
diff --git a/libc/test/src/math/smoke/nexttowardbf16_test.cpp b/libc/test/src/math/smoke/nexttowardbf16_test.cpp
diff --git a/libc/test/src/math/smoke/nextupbf16_test.cpp b/libc/test/src/math/smoke/nextupbf16_test.cpp
