[libc][math][c++23] Add fabsbf16 math function (#148398)

krishna2803 · overmighty · web-flow · commit 111edfcab89b · 2025-07-29T12:19:21.000-04:00
This PR implements fabsbf16 math function for BFloat16 type along with
the tests.

---------

Signed-off-by: krishna2803 &lt;kpandey81930@gmail.com&gt;
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
@@ -754,6 +754,11 @@ if(LIBC_TYPES_HAS_FLOAT128)
   )
 endif()
 
+list(APPEND TARGET_LIBM_ENTRYPOINTS
+  # bfloat16 entrypoints
+  libc.src.math.fabsbf16
+)
+
 if(LIBC_COMPILER_HAS_FIXED_POINT)
   list(APPEND TARGET_LIBM_ENTRYPOINTS
     # stdfix.h _Fract and _Accum entrypoints
diff --git a/libc/config/baremetal/arm/entrypoints.txt b/libc/config/baremetal/arm/entrypoints.txt
@@ -757,6 +757,11 @@ if(LIBC_TYPES_HAS_FLOAT128)
   )
 endif()
 
+list(APPEND TARGET_LIBM_ENTRYPOINTS
+  # bfloat16 entrypoints
+  libc.src.math.fabsbf16
+)
+
 if(LIBC_COMPILER_HAS_FIXED_POINT)
   list(APPEND TARGET_LIBM_ENTRYPOINTS
     # stdfix.h _Fract and _Accum entrypoints
diff --git a/libc/config/baremetal/riscv/entrypoints.txt b/libc/config/baremetal/riscv/entrypoints.txt
@@ -757,6 +757,11 @@ if(LIBC_TYPES_HAS_FLOAT128)
   )
 endif()
 
+list(APPEND TARGET_LIBM_ENTRYPOINTS
+  # bfloat16 entrypoints
+  libc.src.math.fabsbf16
+)
+
 if(LIBC_COMPILER_HAS_FIXED_POINT)
   list(APPEND TARGET_LIBM_ENTRYPOINTS
     # stdfix.h _Fract and _Accum entrypoints
diff --git a/libc/config/darwin/aarch64/entrypoints.txt b/libc/config/darwin/aarch64/entrypoints.txt
@@ -588,6 +588,11 @@ if(LIBC_TYPES_HAS_FLOAT128)
   )
 endif()
 
+list(APPEND TARGET_LIBM_ENTRYPOINTS
+  # bfloat16 entrypoints
+  libc.src.math.fabsbf16
+)
+
 if(LIBC_COMPILER_HAS_FIXED_POINT)
   list(APPEND TARGET_LIBM_ENTRYPOINTS
     # stdfix.h _Fract and _Accum entrypoints
diff --git a/libc/config/darwin/x86_64/entrypoints.txt b/libc/config/darwin/x86_64/entrypoints.txt
@@ -231,6 +231,11 @@ set(TARGET_LIBM_ENTRYPOINTS
     #libc.src.math.truncl
 )
 
+list(APPEND TARGET_LIBM_ENTRYPOINTS
+  # bfloat16 entrypoints
+  libc.src.math.fabsbf16
+)
+
 set(TARGET_LLVMLIBC_ENTRYPOINTS
   ${TARGET_LIBC_ENTRYPOINTS}
   ${TARGET_LIBM_ENTRYPOINTS}
diff --git a/libc/config/gpu/amdgpu/entrypoints.txt b/libc/config/gpu/amdgpu/entrypoints.txt
@@ -612,6 +612,11 @@ if(LIBC_TYPES_HAS_FLOAT16)
   )
 endif()
 
+list(APPEND TARGET_LIBM_ENTRYPOINTS
+  # bfloat16 entrypoints
+  libc.src.math.fabsbf16
+)
+
 set(TARGET_LLVMLIBC_ENTRYPOINTS
   ${TARGET_LIBC_ENTRYPOINTS}
   ${TARGET_LIBM_ENTRYPOINTS}
diff --git a/libc/config/gpu/nvptx/entrypoints.txt b/libc/config/gpu/nvptx/entrypoints.txt
@@ -614,6 +614,11 @@ if(LIBC_TYPES_HAS_FLOAT16)
   )
 endif()
 
+list(APPEND TARGET_LIBM_ENTRYPOINTS
+  # bfloat16 entrypoints
+  libc.src.math.fabsbf16
+)
+
 set(TARGET_LLVMLIBC_ENTRYPOINTS
   ${TARGET_LIBC_ENTRYPOINTS}
   ${TARGET_LIBM_ENTRYPOINTS}
diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
@@ -842,6 +842,11 @@ if(LIBC_TYPES_HAS_FLOAT128)
   )
 endif()
 
+list(APPEND TARGET_LIBM_ENTRYPOINTS
+  # bfloat16 entrypoints
+  libc.src.math.fabsbf16
+)
+
 if(LLVM_LIBC_FULL_BUILD)
   list(APPEND TARGET_LIBC_ENTRYPOINTS
     # assert.h entrypoints
diff --git a/libc/config/linux/arm/entrypoints.txt b/libc/config/linux/arm/entrypoints.txt
@@ -458,6 +458,11 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.ufromfpxl
 )
 
+list(APPEND TARGET_LIBM_ENTRYPOINTS
+  # bfloat16 entrypoints
+  libc.src.math.fabsbf16
+)
+
 set(TARGET_LLVMLIBC_ENTRYPOINTS
   ${TARGET_LIBC_ENTRYPOINTS}
   ${TARGET_LIBM_ENTRYPOINTS}
diff --git a/libc/config/linux/riscv/entrypoints.txt b/libc/config/linux/riscv/entrypoints.txt
@@ -861,6 +861,11 @@ if(LIBC_TYPES_HAS_FLOAT128)
   )
 endif()
 
+list(APPEND TARGET_LIBM_ENTRYPOINTS
+  # bfloat16 entrypoints
+  libc.src.math.fabsbf16
+)
+
 if(LIBC_COMPILER_HAS_FIXED_POINT)
   list(APPEND TARGET_LIBM_ENTRYPOINTS
     # stdfix.h _Fract and _Accum entrypoints
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
@@ -892,6 +892,12 @@ if(LIBC_TYPES_HAS_FLOAT128)
   )
 endif()
 
+
+list(APPEND TARGET_LIBM_ENTRYPOINTS
+  # bfloat16 entrypoints
+  libc.src.math.fabsbf16
+)
+
 if(LIBC_COMPILER_HAS_FIXED_POINT)
   list(APPEND TARGET_LIBM_ENTRYPOINTS
     # stdfix.h _Fract and _Accum entrypoints
diff --git a/libc/config/windows/entrypoints.txt b/libc/config/windows/entrypoints.txt
@@ -304,6 +304,11 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.truncl
 )
 
+list(APPEND TARGET_LIBM_ENTRYPOINTS
+  # bfloat16 entrypoints
+  libc.src.math.fabsbf16
+)
+
 set(TARGET_LLVMLIBC_ENTRYPOINTS
   ${TARGET_LIBC_ENTRYPOINTS}
   ${TARGET_LIBM_ENTRYPOINTS}
diff --git a/libc/src/math/CMakeLists.txt b/libc/src/math/CMakeLists.txt
@@ -189,6 +189,7 @@ add_math_entrypoint_object(fabsf)
 add_math_entrypoint_object(fabsl)
 add_math_entrypoint_object(fabsf16)
 add_math_entrypoint_object(fabsf128)
+add_math_entrypoint_object(fabsbf16)
 
 add_math_entrypoint_object(fadd)
 add_math_entrypoint_object(faddl)
diff --git a/libc/src/math/fabsbf16.h b/libc/src/math/fabsbf16.h
@@ -0,0 +1,21 @@
+//===-- Implementation header for fabsbf16 ----------------------*- 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_FABSBF16_H
+#define LLVM_LIBC_SRC_MATH_FABSBF16_H
+
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/types.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+bfloat16 fabsbf16(bfloat16 x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_MATH_FABSBF16_H
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
@@ -697,6 +697,19 @@ add_entrypoint_object(
     libc.src.__support.FPUtil.basic_operations
 )
 
+add_entrypoint_object(
+  fabsbf16
+  SRCS
+    fabsbf16.cpp
+  HDRS
+    ../fabsbf16.h
+  DEPENDS
+    libc.src.__support.FPUtil.basic_operations
+    libc.src.__support.FPUtil.bfloat16
+    libc.src.__support.macros.config
+    libc.src.__support.macros.properties.types
+)
+
 add_entrypoint_object(
   fadd
   SRCS
diff --git a/libc/src/math/generic/fabsbf16.cpp b/libc/src/math/generic/fabsbf16.cpp
@@ -0,0 +1,19 @@
+//===-- Implementation of fabsbf16 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/fabsbf16.h"
+
+#include "src/__support/FPUtil/BasicOperations.h"
+#include "src/__support/FPUtil/bfloat16.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(bfloat16, fabsbf16, (bfloat16 x)) { return fputil::abs(x); }
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/test/src/math/generic/CMakeLists.txt b/libc/test/src/math/generic/CMakeLists.txt
@@ -30,4 +30,3 @@ add_fp_unittest(
   DEPENDS
     libc.src.math.generic.ceill
 )
-
diff --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
@@ -220,6 +220,19 @@ add_fp_unittest(
     libc.src.__support.FPUtil.fp_bits
 )
 
+add_fp_unittest(
+  fabsbf16_test
+  SUITE
+  libc-math-smoke-tests
+  SRCS
+    fabsbf16_test.cpp
+  HDRS
+    FAbsTest.h
+  DEPENDS
+    libc.src.__support.FPUtil.bfloat16
+    libc.src.math.fabsbf16
+)
+
 add_fp_unittest(
   fadd_test
   SUITE
diff --git a/libc/test/src/math/smoke/fabsbf16_test.cpp b/libc/test/src/math/smoke/fabsbf16_test.cpp
@@ -0,0 +1,14 @@
+//===-- Unittests for fabsbf16 --------------------------------------------===//
+//
+// 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 "FAbsTest.h"
+
+#include "src/__support/FPUtil/bfloat16.h"
+#include "src/math/fabsbf16.h"
+
+LIST_FABS_TESTS(bfloat16, LIBC_NAMESPACE::fabsbf16)
