[libc][math] Refactor fma implementation to header-only in src/__support/math folder. (#163968)

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

libc/shared/math.h

@@ -137,6 +137,7 @@
 #include "math/floorf128.h"
 #include "math/floorf16.h"
 #include "math/floorl.h"
+#include "math/fma.h"
 #include "math/fmabf16.h"
 #include "math/fmax.h"
 #include "math/fmaxbf16.h"

libc/shared/math/fma.h

@@ -0,0 +1,23 @@
+//===-- Shared fma 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_FMA_H
+#define LLVM_LIBC_SHARED_MATH_FMA_H
+
+#include "shared/libc_common.h"
+#include "src/__support/math/fma.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::fma;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SHARED_MATH_FMA_H

libc/src/__support/math/CMakeLists.txt

@@ -1320,6 +1320,15 @@ add_header_library(
     libc.src.__support.macros.properties.types
 )
 
+add_header_library(
+  fma
+  HDRS
+    fma.h
+  DEPENDS
+    libc.src.__support.FPUtil.fma
+    libc.src.__support.macros.config
+)
+
 add_header_library(
   ffma
   HDRS

libc/src/__support/math/fma.h

@@ -0,0 +1,27 @@
+//===-- Implementation header for fma ---------------------------*- 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_FMA_H
+#define LLVM_LIBC_SRC___SUPPORT_MATH_FMA_H
+
+#include "src/__support/FPUtil/FMA.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+namespace math {
+
+LIBC_INLINE double fma(double x, double y, double z) {
+  return fputil::fma<double>(x, y, z);
+}
+
+} // namespace math
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC___SUPPORT_MATH_FMA_H

libc/src/math/generic/CMakeLists.txt

@@ -4399,7 +4399,7 @@ add_entrypoint_object(
   HDRS
     ../fma.h
   DEPENDS
-    libc.src.__support.FPUtil.fma
+    libc.src.__support.math.fma
 )
 
 add_entrypoint_object(

libc/src/math/generic/fma.cpp

@@ -7,15 +7,12 @@
 //===----------------------------------------------------------------------===//
 
 #include "src/math/fma.h"
-#include "src/__support/common.h"
-
-#include "src/__support/FPUtil/FMA.h"
-#include "src/__support/macros/config.h"
+#include "src/__support/math/fma.h"
 
 namespace LIBC_NAMESPACE_DECL {
 
 LLVM_LIBC_FUNCTION(double, fma, (double x, double y, double z)) {
-  return fputil::fma<double>(x, y, z);
+  return math::fma(x, y, z);
 }
 
 } // namespace LIBC_NAMESPACE_DECL

libc/test/shared/CMakeLists.txt

@@ -134,6 +134,7 @@ add_fp_unittest(
     libc.src.__support.math.floorf128
     libc.src.__support.math.floorf16
     libc.src.__support.math.floorl
+    libc.src.__support.math.fma
     libc.src.__support.math.fmabf16
     libc.src.__support.math.fmax
     libc.src.__support.math.fmaxbf16

libc/test/shared/shared_math_test.cpp

@@ -247,6 +247,7 @@ TEST(LlvmLibcSharedMathTest, AllDouble) {
   EXPECT_FP_EQ(0x1p+0, LIBC_NAMESPACE::shared::exp2(0.0));
   EXPECT_FP_EQ(0x1p+0, LIBC_NAMESPACE::shared::exp10(0.0));
   EXPECT_FP_EQ(0x0p+0, LIBC_NAMESPACE::shared::expm1(0.0));
+  EXPECT_FP_EQ(0x0p+0, LIBC_NAMESPACE::shared::fma(0.0, 0.0, 0.0));
   EXPECT_FP_EQ(0x0p+0f, LIBC_NAMESPACE::shared::ffma(0.0, 0.0, 0.0));
   EXPECT_FP_EQ(0.0, LIBC_NAMESPACE::shared::hypot(0.0, 0.0));
   EXPECT_FP_EQ(0x0p+0, LIBC_NAMESPACE::shared::fsqrt(0.0));

utils/bazel/llvm-project-overlay/libc/BUILD.bazel

@@ -4311,6 +4311,14 @@ libc_support_library(
     ],
 )
 
+libc_support_library(
+    name = "__support_math_fma",
+    hdrs = ["src/__support/math/fma.h"],
+    deps = [
+        ":__support_fputil_fma",
+    ],
+)
+
 libc_support_library(
     name = "__support_math_frexpf128",
     hdrs = ["src/__support/math/frexpf128.h"],
@@ -7090,7 +7098,7 @@ libc_math_function(
 libc_math_function(
     name = "fmaf16",
     additional_deps = [
-        ":__support_fputil_fma",
+        ":__support_math_fma",
     ],
 )