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[libc][math] Refactor fmaf implementation to header-only in src/__support/math folder. #163970
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    …port/math folder.
  This was referenced Oct 17, 2025 
      
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| @llvm/pr-subscribers-libc Author: Muhammad Bassiouni (bassiounix) ChangesPart 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 Full diff: https://github.com/llvm/llvm-project/pull/163970.diff 9 Files Affected: 
 diff --git a/libc/shared/math.h b/libc/shared/math.h
index 79ba2ea5aa6ff..2198ffdc74459 100644
--- a/libc/shared/math.h
+++ b/libc/shared/math.h
@@ -58,6 +58,7 @@
 #include "math/expm1f.h"
 #include "math/expm1f16.h"
 #include "math/fma.h"
+#include "math/fmaf.h"
 #include "math/frexpf.h"
 #include "math/frexpf128.h"
 #include "math/frexpf16.h"
diff --git a/libc/shared/math/fmaf.h b/libc/shared/math/fmaf.h
new file mode 100644
index 0000000000000..eef75b05d4a18
--- /dev/null
+++ b/libc/shared/math/fmaf.h
@@ -0,0 +1,23 @@
+//===-- Shared fmaf 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_FMAF_H
+#define LLVM_LIBC_SHARED_MATH_FMAF_H
+
+#include "shared/libc_common.h"
+#include "src/__support/math/fmaf.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::fmaf;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SHARED_MATH_FMAF_H
diff --git a/libc/src/__support/math/CMakeLists.txt b/libc/src/__support/math/CMakeLists.txt
index 1911481d0649e..56229957a4c56 100644
--- a/libc/src/__support/math/CMakeLists.txt
+++ b/libc/src/__support/math/CMakeLists.txt
@@ -601,6 +601,14 @@ add_header_library(
     libc.src.__support.FPUtil.fma
 )
 
+add_header_library(
+  fmaf
+  HDRS
+    fmaf.h
+  DEPENDS
+    libc.src.__support.FPUtil.fma
+)
+
 add_header_library(
   frexpf128
   HDRS
diff --git a/libc/src/__support/math/fmaf.h b/libc/src/__support/math/fmaf.h
new file mode 100644
index 0000000000000..f5b893873e885
--- /dev/null
+++ b/libc/src/__support/math/fmaf.h
@@ -0,0 +1,27 @@
+//===-- Implementation header for fmaf --------------------------*- 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_FMAF_H
+#define LLVM_LIBC_SRC___SUPPORT_MATH_FMAF_H
+
+#include "src/__support/FPUtil/FMA.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+namespace math {
+
+LIBC_INLINE static float fmaf(float x, float y, float z) {
+  return fputil::fma<float>(x, y, z);
+}
+
+} // namespace math
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC___SUPPORT_MATH_FMAF_H
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index 7103c6947eba0..55055803731ae 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -4701,7 +4701,7 @@ add_entrypoint_object(
   HDRS
     ../fmaf.h
   DEPENDS
-    libc.src.__support.FPUtil.fma
+    libc.src.__support.math.fmaf
 )
 
 add_entrypoint_object(
diff --git a/libc/src/math/generic/fmaf.cpp b/libc/src/math/generic/fmaf.cpp
index dad85b4e9d1e6..069c7c4605da7 100644
--- a/libc/src/math/generic/fmaf.cpp
+++ b/libc/src/math/generic/fmaf.cpp
@@ -7,15 +7,12 @@
 //===----------------------------------------------------------------------===//
 
 #include "src/math/fmaf.h"
-#include "src/__support/common.h"
-
-#include "src/__support/FPUtil/FMA.h"
-#include "src/__support/macros/config.h"
+#include "src/__support/math/fmaf.h"
 
 namespace LIBC_NAMESPACE_DECL {
 
 LLVM_LIBC_FUNCTION(float, fmaf, (float x, float y, float z)) {
-  return fputil::fma<float>(x, y, z);
+  return math::fmaf(x, y, z);
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/test/shared/CMakeLists.txt b/libc/test/shared/CMakeLists.txt
index cd4b5ec75f876..f5c42c145c318 100644
--- a/libc/test/shared/CMakeLists.txt
+++ b/libc/test/shared/CMakeLists.txt
@@ -54,6 +54,7 @@ add_fp_unittest(
     libc.src.__support.math.expf
     libc.src.__support.math.expf16
     libc.src.__support.math.fma
+    libc.src.__support.math.fmaf
     libc.src.__support.math.frexpf
     libc.src.__support.math.frexpf128
     libc.src.__support.math.frexpf16
diff --git a/libc/test/shared/shared_math_test.cpp b/libc/test/shared/shared_math_test.cpp
index 7357e24603004..d81ae4df562b6 100644
--- a/libc/test/shared/shared_math_test.cpp
+++ b/libc/test/shared/shared_math_test.cpp
@@ -67,7 +67,7 @@ TEST(LlvmLibcSharedMathTest, AllFloat) {
   EXPECT_FP_EQ(0x1p+0f, LIBC_NAMESPACE::shared::expf(0.0f));
   EXPECT_FP_EQ(0x1p+0f, LIBC_NAMESPACE::shared::exp2f(0.0f));
   EXPECT_FP_EQ(0x0p+0f, LIBC_NAMESPACE::shared::expm1f(0.0f));
-
+  EXPECT_FP_EQ(0x0p+0f, LIBC_NAMESPACE::shared::fmaf(0.0f, 0.0f, 0.0f));
   EXPECT_FP_EQ_ALL_ROUNDING(0.75f,
                             LIBC_NAMESPACE::shared::frexpf(24.0f, &exponent));
   EXPECT_EQ(exponent, 5);
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index 1902b43216a7c..d3f3168f31a0d 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -2799,6 +2799,14 @@ libc_support_library(
     ],
 )
 
+libc_support_library(
+    name = "__support_math_fmaf",
+    hdrs = ["src/__support/math/fmaf.h"],
+    deps = [
+        ":__support_fputil_fma",
+    ],
+)
+
 libc_support_library(
     name = "__support_math_frexpf128",
     hdrs = ["src/__support/math/frexpf128.h"],
@@ -4016,7 +4024,7 @@ libc_math_function(
 libc_math_function(
     name = "fmaf",
     additional_deps = [
-        ":__support_fputil_fma",
+        ":__support_math_fmaf",
     ],
 )
 
 | 
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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