[libc][math][c23] Add f16subf128 C23 math function

Author: overmighty

libc/config/linux/x86_64/entrypoints.txt

@@ -604,6 +604,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
       libc.src.math.f16addf128
       libc.src.math.f16divf128
       libc.src.math.f16fmaf128
+      libc.src.math.f16subf128
     )
   endif()
 endif()

libc/docs/math/index.rst

@@ -130,7 +130,7 @@ Basic Operations
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | f16fma           | |check|          | |check|         | |check|                | N/A                  | |check|                | 7.12.14.5              | F.10.11                    |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
-| f16sub           | |check|\*        | |check|         |                        | N/A                  |                        | 7.12.14.2              | F.10.11                    |
+| f16sub           | |check|\*        | |check|         |                        | N/A                  | |check|                | 7.12.14.2              | F.10.11                    |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | fabs             | |check|          | |check|         | |check|                | |check|              | |check|                | 7.12.7.3               | F.10.4.3                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+

libc/spec/stdc.td

@@ -734,6 +734,7 @@ def StdC : StandardSpec<"stdc"> {
           GuardedFunctionSpec<"f16addf128", RetValSpec<Float16Type>, [ArgSpec<Float128Type>, ArgSpec<Float128Type>], "LIBC_TYPES_HAS_FLOAT16_AND_FLOAT128">,
 
           GuardedFunctionSpec<"f16sub", RetValSpec<Float16Type>, [ArgSpec<DoubleType>, ArgSpec<DoubleType>], "LIBC_TYPES_HAS_FLOAT16">,
+          GuardedFunctionSpec<"f16subf128", RetValSpec<Float16Type>, [ArgSpec<Float128Type>, ArgSpec<Float128Type>], "LIBC_TYPES_HAS_FLOAT16_AND_FLOAT128">,
 
           GuardedFunctionSpec<"f16divf128", RetValSpec<Float16Type>, [ArgSpec<Float128Type>, ArgSpec<Float128Type>], "LIBC_TYPES_HAS_FLOAT16_AND_FLOAT128">,
 

libc/src/math/CMakeLists.txt

@@ -118,6 +118,7 @@ add_math_entrypoint_object(f16sqrtf)
 
 add_math_entrypoint_object(f16sub)
 add_math_entrypoint_object(f16subf)
+add_math_entrypoint_object(f16subf128)
 
 add_math_entrypoint_object(fabs)
 add_math_entrypoint_object(fabsf)

libc/src/math/f16subf128.h

@@ -0,0 +1,20 @@
+//===-- Implementation header for f16subf128 --------------------*- 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_F16SUBF128_H
+#define LLVM_LIBC_SRC_MATH_F16SUBF128_H
+
+#include "src/__support/macros/properties/types.h"
+
+namespace LIBC_NAMESPACE {
+
+float16 f16subf128(float128 x, float128 y);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_MATH_F16SUBF128_H

libc/src/math/generic/CMakeLists.txt

@@ -3854,6 +3854,19 @@ add_entrypoint_object(
     -O3
 )
 
+add_entrypoint_object(
+  f16subf128
+  SRCS
+    f16subf128.cpp
+  HDRS
+    ../f16subf128.h
+  DEPENDS
+    libc.src.__support.macros.properties.types
+    libc.src.__support.FPUtil.generic.add_sub
+  COMPILE_OPTIONS
+    -O3
+)
+
 add_entrypoint_object(
   f16div
   SRCS

libc/src/math/generic/f16subf128.cpp

@@ -0,0 +1,19 @@
+//===-- Implementation of f16subf128 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/f16subf128.h"
+#include "src/__support/FPUtil/generic/add_sub.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(float16, f16subf128, (float128 x, float128 y)) {
+  return fputil::generic::sub<float16>(x, y);
+}
+
+} // namespace LIBC_NAMESPACE

libc/test/src/math/smoke/CMakeLists.txt

@@ -3718,6 +3718,20 @@ add_fp_unittest(
     libc.src.math.f16subf
 )
 
+add_fp_unittest(
+  f16subf128_test
+  SUITE
+    libc-math-smoke-tests
+  SRCS
+    f16subf128_test.cpp
+  HDRS
+    SubTest.h
+  DEPENDS
+    libc.hdr.fenv_macros
+    libc.src.__support.FPUtil.basic_operations
+    libc.src.math.f16subf128
+)
+
 add_fp_unittest(
   f16div_test
   SUITE

libc/test/src/math/smoke/f16subf128_test.cpp

@@ -0,0 +1,13 @@
+//===-- Unittests for f16subf128 ------------------------------------------===//
+//
+// 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 "SubTest.h"
+
+#include "src/math/f16subf128.h"
+
+LIST_SUB_TESTS(float16, float128, LIBC_NAMESPACE::f16subf128)