[libc] Add implementations of nearbyint[f|l].

[sivachandra]

Summary

The implementation is exactly the same as rint* as even rint does not
raise any floating point exceptions currently. [Note that the standards
do not specify that floating point exceptions must be raised - they
leave it up to the implementation to choose to raise FE_INEXACT when
rounding non-integral values.]

libc/config/linux/x86_64/entrypoints.txt

set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.lrintf
     libc.src.math.lrintl
     libc.src.math.lround
     libc.src.math.lroundf
     libc.src.math.lroundl
     libc.src.math.modf
     libc.src.math.modff
     libc.src.math.modfl
+    libc.src.math.nearbyint
+    libc.src.math.nearbyintf
+    libc.src.math.nearbyintl
     libc.src.math.remainderf
     libc.src.math.remainder
     libc.src.math.remainderl
     libc.src.math.remquof
     libc.src.math.remquo
     libc.src.math.remquol
     libc.src.math.rint
     libc.src.math.rintf

libc/spec/stdc.td

HeaderSpec Math = HeaderSpec<
 
           FunctionSpec<"sqrt", RetValSpec<DoubleType>, [ArgSpec<DoubleType>]>,
           FunctionSpec<"sqrtf", RetValSpec<FloatType>, [ArgSpec<FloatType>]>,
           FunctionSpec<"sqrtl", RetValSpec<LongDoubleType>, [ArgSpec<LongDoubleType>]>,
 
           FunctionSpec<"trunc", RetValSpec<DoubleType>, [ArgSpec<DoubleType>]>,
           FunctionSpec<"truncf", RetValSpec<FloatType>, [ArgSpec<FloatType>]>,
           FunctionSpec<"truncl", RetValSpec<LongDoubleType>, [ArgSpec<LongDoubleType>]>,
+
+          FunctionSpec<"nearbyint", RetValSpec<DoubleType>, [ArgSpec<DoubleType>]>,
+          FunctionSpec<"nearbyintf", RetValSpec<FloatType>, [ArgSpec<FloatType>]>,
+          FunctionSpec<"nearbyintl", RetValSpec<LongDoubleType>, [ArgSpec<LongDoubleType>]>,
       ]
   >;
 
   HeaderSpec StdIO = HeaderSpec<
       "stdio.h",
       [], // Macros
       [ // Types
           SizeTType,

libc/src/math/CMakeLists.txt

add_entrypoint_object(
   HDRS
     llrintl.h
   DEPENDS
     libc.utils.FPUtil.fputil
   COMPILE_OPTIONS
     -O2
 )
 
+add_entrypoint_object(
+  nearbyint
+  SRCS
+    nearbyint.cpp
+  HDRS
+    nearbyint.h
+  DEPENDS
+    libc.utils.FPUtil.fputil
+  COMPILE_OPTIONS
+    -O2
+)
+
+add_entrypoint_object(
+  nearbyintf
+  SRCS
+    nearbyintf.cpp
+  HDRS
+    nearbyintf.h
+  DEPENDS
+    libc.utils.FPUtil.fputil
+  COMPILE_OPTIONS
+    -O2
+)
+
+add_entrypoint_object(
+  nearbyintl
+  SRCS
+    nearbyintl.cpp
+  HDRS
+    nearbyintl.h
+  DEPENDS
+    libc.utils.FPUtil.fputil
+  COMPILE_OPTIONS
+    -O2
+)
+
 add_object_library(
   exp_utils
   HDRS
     exp_utils.h
   SRCS
     exp_utils.cpp
   DEPENDS
     .math_utils

libc/src/math/nearbyint.h

+//===-- Implementation header for nearbyint ---------------------*- 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_NEARBYINT_H
+#define LLVM_LIBC_SRC_MATH_NEARBYINT_H
+
+namespace __llvm_libc {
+
+double nearbyint(double x);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_MATH_NEARBYINT_H

libc/src/math/nearbyint.cpp

+//===-- Implementation of nearbyint 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/__support/common.h"
+#include "utils/FPUtil/NearestIntegerOperations.h"
+
+namespace __llvm_libc {
+
+double LLVM_LIBC_ENTRYPOINT(nearbyint)(double x) {
+  return fputil::roundUsingCurrentRoundingMode(x);
+}
+
+} // namespace __llvm_libc

libc/src/math/nearbyintf.h

+//===-- Implementation header for nearbyintf --------------------*- 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_NEARBYINTF_H
+#define LLVM_LIBC_SRC_MATH_NEARBYINTF_H
+
+namespace __llvm_libc {
+
+float nearbyintf(float x);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_MATH_NEARBYINTF_H

libc/src/math/nearbyintf.cpp

+//===-- Implementation of nearbyintf 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/__support/common.h"
+#include "utils/FPUtil/NearestIntegerOperations.h"
+
+namespace __llvm_libc {
+
+float LLVM_LIBC_ENTRYPOINT(nearbyintf)(float x) {
+  return fputil::roundUsingCurrentRoundingMode(x);
+}
+
+} // namespace __llvm_libc

libc/src/math/nearbyintl.h

+//===-- Implementation header for nearbyintl --------------------*- 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_NEARBYINTL_H
+#define LLVM_LIBC_SRC_MATH_NEARBYINTL_H
+
+namespace __llvm_libc {
+
+long double nearbyintl(long double x);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_MATH_NEARBYINTL_H

libc/src/math/nearbyintl.cpp

+//===-- Implementation of nearbyintl 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/__support/common.h"
+#include "utils/FPUtil/NearestIntegerOperations.h"
+
+namespace __llvm_libc {
+
+long double LLVM_LIBC_ENTRYPOINT(nearbyintl)(long double x) {
+  return fputil::roundUsingCurrentRoundingMode(x);
+}
+
+} // namespace __llvm_libc