[libc] [llvm] [libc][math] Refactor ldexpf16 implementation to header-only in src/__support/math folder. (PR #147901)

[Muhammad Bassiouni via llvm-commits]

https://github.com/bassiounix created https://github.com/llvm/llvm-project/pull/147901

Part of #147386

in preparation for: https://discourse.llvm.org/t/rfc-make-clang-builtin-math-functions-constexpr-with-llvm-libc-to-support-c-23-constexpr-math-functions/86450

@lntue 

>From 7db2f39cff5fa4ff5c3ab1a9140fe90ec44c6aa1 Mon Sep 17 00:00:00 2001
From: bassiounix <muhammad.m.bassiouni at gmail.com>
Date: Thu, 10 Jul 2025 09:55:59 +0300
Subject: [PATCH] [libc][math] Refactor ldexpf16 implementation to header-only
 in src/__support/math folder.

---
 libc/shared/math.h                            |  1 +
 libc/shared/math/ldexpf16.h                   | 31 +++++++++++++++++
 libc/src/__support/math/CMakeLists.txt        | 10 ++++++
 libc/src/__support/math/ldexpf16.h            | 34 +++++++++++++++++++
 libc/src/math/generic/CMakeLists.txt          |  3 +-
 libc/src/math/generic/ldexpf16.cpp            |  7 ++--
 .../llvm-project-overlay/libc/BUILD.bazel     | 17 +++++++++-
 7 files changed, 96 insertions(+), 7 deletions(-)
 create mode 100644 libc/shared/math/ldexpf16.h
 create mode 100644 libc/src/__support/math/ldexpf16.h

diff --git a/libc/shared/math.h b/libc/shared/math.h
index 4ddc29c7ae834..467d5f5c5c350 100644
--- a/libc/shared/math.h
+++ b/libc/shared/math.h
@@ -12,5 +12,6 @@
 #include "libc_common.h"
 
 #include "math/expf.h"
+#include "math/ldexpf16.h"
 
 #endif // LLVM_LIBC_SHARED_MATH_H
diff --git a/libc/shared/math/ldexpf16.h b/libc/shared/math/ldexpf16.h
new file mode 100644
index 0000000000000..d4e39c449943e
--- /dev/null
+++ b/libc/shared/math/ldexpf16.h
@@ -0,0 +1,31 @@
+//===-- Shared ldexpf16 function --------------------------------*- 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_SHARED_MATH_ldexpf16_H
+#define LLVM_LIBC_SHARED_MATH_ldexpf16_H
+
+#include "include/llvm-libc-macros/float16-macros.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT16
+
+#include "shared/libc_common.h"
+#include "src/__support/math/ldexpf16.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+namespace shared {
+
+using math::ldexpf16;
+
+} // namespace shared
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT16
+
+#endif // LLVM_LIBC_SHARED_MATH_ldexpf16_H
diff --git a/libc/src/__support/math/CMakeLists.txt b/libc/src/__support/math/CMakeLists.txt
index 66c1d19a1cab0..114c46ca0aeb8 100644
--- a/libc/src/__support/math/CMakeLists.txt
+++ b/libc/src/__support/math/CMakeLists.txt
@@ -22,3 +22,13 @@ add_header_library(
     libc.src.__support.macros.config
     libc.src.__support.macros.optimization
 )
+
+add_header_library(
+  ldexpf16
+  HDRS
+    ldexpf16.h
+  DEPENDS
+    libc.src.__support.macros.properties.types
+    libc.src.__support.FPUtil.manipulation_functions
+    libc.include.llvm-libc-macros.float16_macros
+)
diff --git a/libc/src/__support/math/ldexpf16.h b/libc/src/__support/math/ldexpf16.h
new file mode 100644
index 0000000000000..fbead87d909a8
--- /dev/null
+++ b/libc/src/__support/math/ldexpf16.h
@@ -0,0 +1,34 @@
+//===-- Implementation header for ldexpf16 ----------------------*- 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___SUPPORT_MATH_LDEXPF16_H
+#define LLVM_LIBC_SRC___SUPPORT_MATH_LDEXPF16_H
+
+#include "include/llvm-libc-macros/float16-macros.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT16
+
+#include "src/__support/FPUtil/ManipulationFunctions.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+namespace math {
+
+static constexpr float16 ldexpf16(float16 x, int exp) {
+  return fputil::ldexp(x, exp);
+}
+
+} // namespace math
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT16
+
+#endif // LLVM_LIBC_SRC___SUPPORT_MATH_LDEXPF16_H
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index fd1e6c0d648aa..ead06dd0a9dfc 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -1931,8 +1931,7 @@ add_entrypoint_object(
   HDRS
     ../ldexpf16.h
   DEPENDS
-    libc.src.__support.macros.properties.types
-    libc.src.__support.FPUtil.manipulation_functions
+    libc.src.__support.math.ldexpf16
 )
 
 add_entrypoint_object(
diff --git a/libc/src/math/generic/ldexpf16.cpp b/libc/src/math/generic/ldexpf16.cpp
index caa344b41476b..ecf16337ee79a 100644
--- a/libc/src/math/generic/ldexpf16.cpp
+++ b/libc/src/math/generic/ldexpf16.cpp
@@ -7,14 +7,13 @@
 //===----------------------------------------------------------------------===//
 
 #include "src/math/ldexpf16.h"
-#include "src/__support/FPUtil/ManipulationFunctions.h"
-#include "src/__support/common.h"
-#include "src/__support/macros/config.h"
+
+#include "src/__support/math/ldexpf16.h"
 
 namespace LIBC_NAMESPACE_DECL {
 
 LLVM_LIBC_FUNCTION(float16, ldexpf16, (float16 x, int exp)) {
-  return fputil::ldexp(x, exp);
+  return math::ldexpf16(x, exp);
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index 2484a2f1e2bd7..50bb1e88356f2 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -2096,6 +2096,16 @@ libc_support_library(
     ],
 )
 
+libc_support_library(
+    name = "__support_math_ldexpf16",
+    hdrs = ["src/__support/math/ldexpf16.h"],
+    deps = [
+        ":__support_macros_properties_types",
+        ":__support_fputil_manipulation_functions",
+        ":llvm_libc_macros_float16_macros"
+    ],
+)
+
 ############################### complex targets ################################
 
 libc_function(
@@ -3235,7 +3245,12 @@ libc_math_function(name = "ldexpl")
 
 libc_math_function(name = "ldexpf128")
 
-libc_math_function(name = "ldexpf16")
+libc_math_function(
+    name = "ldexpf16",
+    additional_deps = [
+        ":__support_math_ldexpf16",
+    ],
+)
 
 libc_math_function(name = "llogb")