[libc] Implement roundeven C23 math functions (#87678)

Implements the functions `roundeven()`, `roundevenf()`, `roundevenl()`
from the roundeven family of functions introduced in C23. Also
implements `roundevenf128()`.

Author: vinayakdsci

libc/config/linux/x86_64/entrypoints.txt

@@ -494,6 +494,9 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.round
     libc.src.math.roundf
     libc.src.math.roundl
+    libc.src.math.roundeven
+    libc.src.math.roundevenf
+    libc.src.math.roundevenl
     libc.src.math.scalbn
     libc.src.math.scalbnf
     libc.src.math.scalbnl
@@ -555,6 +558,7 @@ if(LIBC_TYPES_HAS_FLOAT128)
     libc.src.math.nextdownf128
     libc.src.math.nextupf128
     libc.src.math.rintf128
+    libc.src.math.roundevenf128
     libc.src.math.roundf128
     libc.src.math.sqrtf128
     libc.src.math.truncf128

libc/docs/c23.rst

@@ -54,7 +54,7 @@ Additions:
   * pown*
   * powr*
   * rootn*
-  * roundeven*
+  * roundeven* |check|
   * fromfp*
   * ufromfp*
   * fromfpx*

libc/docs/math/index.rst

@@ -206,7 +206,7 @@ Basic Operations
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | round            | |check|          | |check|         | |check|                |                      | |check|                | 7.12.9.6               | F.10.6.6                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
-| roundeven        |                  |                 |                        |                      |                        | 7.12.9.8               | F.10.6.8                   |
+| roundeven        | |check|          | |check|         | |check|                |                      | |check|                | 7.12.9.8               | F.10.6.8                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | scalbn           | |check|          | |check|         | |check|                |                      |                        | 7.12.6.19              | F.10.3.19                  |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+

libc/src/math/CMakeLists.txt

@@ -293,6 +293,11 @@ add_math_entrypoint_object(roundf)
 add_math_entrypoint_object(roundl)
 add_math_entrypoint_object(roundf128)
 
+add_math_entrypoint_object(roundeven)
+add_math_entrypoint_object(roundevenf)
+add_math_entrypoint_object(roundevenl)
+add_math_entrypoint_object(roundevenf128)
+
 add_math_entrypoint_object(scalbn)
 add_math_entrypoint_object(scalbnf)
 add_math_entrypoint_object(scalbnl)

libc/src/math/generic/CMakeLists.txt

@@ -417,6 +417,55 @@ add_entrypoint_object(
     libc.src.__support.FPUtil.nearest_integer_operations
 )
 
+add_entrypoint_object(
+  roundeven
+  SRCS
+    roundeven.cpp
+  HDRS
+    ../roundeven.h
+  COMPILE_OPTIONS
+    -O3
+  DEPENDS
+    libc.src.__support.FPUtil.nearest_integer_operations
+)
+
+add_entrypoint_object(
+  roundevenf
+  SRCS
+    roundevenf.cpp
+  HDRS
+    ../roundevenf.h
+  COMPILE_OPTIONS
+    -O3
+  DEPENDS
+    libc.src.__support.FPUtil.nearest_integer_operations
+)
+
+add_entrypoint_object(
+  roundevenl
+  SRCS
+    roundevenl.cpp
+  HDRS
+    ../roundevenl.h
+  COMPILE_OPTIONS
+    -O3
+  DEPENDS
+    libc.src.__support.FPUtil.nearest_integer_operations
+)
+
+add_entrypoint_object(
+  roundevenf128
+  SRCS
+    roundevenf128.cpp
+  HDRS
+    ../roundevenf128.h
+  COMPILE_OPTIONS
+    -O3
+  DEPENDS
+    libc.src.__support.macros.properties.types
+    libc.src.__support.FPUtil.nearest_integer_operations
+)
+
 add_entrypoint_object(
   lround
   SRCS

libc/src/math/generic/roundeven.cpp

@@ -0,0 +1,19 @@
+//===-- Implementation of roundeven 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/roundeven.h"
+#include "src/__support/FPUtil/NearestIntegerOperations.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(double, roundeven, (double x)) {
+  return fputil::round_using_specific_rounding_mode(x, FP_INT_TONEAREST);
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/math/generic/roundevenf.cpp

@@ -0,0 +1,19 @@
+//===-- Implementation of roundevenf 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/roundevenf.h"
+#include "src/__support/FPUtil/NearestIntegerOperations.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(float, roundevenf, (float x)) {
+  return fputil::round_using_specific_rounding_mode(x, FP_INT_TONEAREST);
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/math/generic/roundevenf128.cpp

@@ -0,0 +1,19 @@
+//===-- Implementation of roundevenf128 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/roundevenf128.h"
+#include "src/__support/FPUtil/NearestIntegerOperations.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(float128, roundevenf128, (float128 x)) {
+  return fputil::round_using_specific_rounding_mode(x, FP_INT_TONEAREST);
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/math/generic/roundevenl.cpp

@@ -0,0 +1,19 @@
+//===-- Implementation of roundevenl 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/roundevenl.h"
+#include "src/__support/FPUtil/NearestIntegerOperations.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(long double, roundevenl, (long double x)) {
+  return fputil::round_using_specific_rounding_mode(x, FP_INT_TONEAREST);
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/math/roundeven.h

@@ -0,0 +1,18 @@
+//===-- Implementation header for roundeven ---------------------*- 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_ROUNDEVEN_H
+#define LLVM_LIBC_SRC_MATH_ROUNDEVEN_H
+
+namespace LIBC_NAMESPACE {
+
+double roundeven(double x);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_MATH_ROUNDEVEN_H