[libc][math][c23] Add f16fmaf C23 math function (#95483)

Part of #93566.

Author: overmighty

libc/config/linux/aarch64/entrypoints.txt

@@ -503,6 +503,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
     libc.src.math.canonicalizef16
     libc.src.math.ceilf16
     libc.src.math.copysignf16
+    libc.src.math.f16fmaf
     libc.src.math.f16sqrtf
     libc.src.math.fabsf16
     libc.src.math.fdimf16

libc/config/linux/x86_64/entrypoints.txt

@@ -535,6 +535,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
     libc.src.math.canonicalizef16
     libc.src.math.ceilf16
     libc.src.math.copysignf16
+    libc.src.math.f16fmaf
     libc.src.math.f16sqrtf
     libc.src.math.fabsf16
     libc.src.math.fdimf16

libc/docs/math/index.rst

@@ -124,6 +124,8 @@ Basic Operations
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | dsub             | N/A              | N/A             |                        | N/A                  |                        | 7.12.14.2              | F.10.11                    |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
+| f16fma           | |check|          |                 |                        | N/A                  |                        | 7.12.14.5              | F.10.11                    |
++------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | fabs             | |check|          | |check|         | |check|                | |check|              | |check|                | 7.12.7.3               | F.10.4.3                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | fadd             | N/A              |                 |                        | N/A                  |                        | 7.12.14.1              | F.10.11                    |

libc/spec/stdc.td

@@ -474,10 +474,11 @@ def StdC : StandardSpec<"stdc"> {
 
           FunctionSpec<"fmul", RetValSpec<FloatType>, [ArgSpec<DoubleType>, ArgSpec<DoubleType>]>,
 
-
           FunctionSpec<"fma", RetValSpec<DoubleType>, [ArgSpec<DoubleType>, ArgSpec<DoubleType>, ArgSpec<DoubleType>]>,
           FunctionSpec<"fmaf", RetValSpec<FloatType>, [ArgSpec<FloatType>, ArgSpec<FloatType>, ArgSpec<FloatType>]>,
 
+          GuardedFunctionSpec<"f16fmaf", RetValSpec<Float16Type>, [ArgSpec<FloatType>, ArgSpec<FloatType>, ArgSpec<FloatType>], "LIBC_TYPES_HAS_FLOAT16">,
+
           FunctionSpec<"fmod", RetValSpec<DoubleType>, [ArgSpec<DoubleType>, ArgSpec<DoubleType>]>,
           FunctionSpec<"fmodf", RetValSpec<FloatType>, [ArgSpec<FloatType>, ArgSpec<FloatType>]>,
           FunctionSpec<"fmodl", RetValSpec<LongDoubleType>, [ArgSpec<LongDoubleType>, ArgSpec<LongDoubleType>]>,

libc/src/__support/FPUtil/FMA.h

@@ -10,41 +10,29 @@
 #define LLVM_LIBC_SRC___SUPPORT_FPUTIL_FMA_H
 
 #include "src/__support/CPP/type_traits.h"
+#include "src/__support/FPUtil/generic/FMA.h"
 #include "src/__support/macros/properties/architectures.h"
 #include "src/__support/macros/properties/cpu_features.h" // LIBC_TARGET_CPU_HAS_FMA
 
-#if defined(LIBC_TARGET_CPU_HAS_FMA)
-
 namespace LIBC_NAMESPACE {
 namespace fputil {
 
-template <typename T>
-LIBC_INLINE cpp::enable_if_t<cpp::is_same_v<T, float>, T> fma(T x, T y, T z) {
-  return __builtin_fmaf(x, y, z);
+template <typename OutType, typename InType>
+LIBC_INLINE OutType fma(InType x, InType y, InType z) {
+  return generic::fma<OutType>(x, y, z);
 }
 
-template <typename T>
-LIBC_INLINE cpp::enable_if_t<cpp::is_same_v<T, double>, T> fma(T x, T y, T z) {
-  return __builtin_fma(x, y, z);
+#ifdef LIBC_TARGET_CPU_HAS_FMA
+template <> LIBC_INLINE float fma(float x, float y, float z) {
+  return __builtin_fmaf(x, y, z);
 }
 
-} // namespace fputil
-} // namespace LIBC_NAMESPACE
-
-#else
-// FMA instructions are not available
-#include "generic/FMA.h"
-
-namespace LIBC_NAMESPACE {
-namespace fputil {
-
-template <typename T> LIBC_INLINE T fma(T x, T y, T z) {
-  return generic::fma(x, y, z);
+template <> LIBC_INLINE double fma(double x, double y, double z) {
+  return __builtin_fma(x, y, z);
 }
+#endif // LIBC_TARGET_CPU_HAS_FMA
 
 } // namespace fputil
 } // namespace LIBC_NAMESPACE
 
-#endif
-
 #endif // LLVM_LIBC_SRC___SUPPORT_FPUTIL_FMA_H

libc/src/__support/FPUtil/generic/CMakeLists.txt

@@ -19,12 +19,15 @@ add_header_library(
   HDRS
     FMA.h
   DEPENDS
+    libc.hdr.fenv_macros
     libc.src.__support.common
     libc.src.__support.CPP.bit
+    libc.src.__support.CPP.limits
     libc.src.__support.CPP.type_traits
     libc.src.__support.FPUtil.fenv_impl
     libc.src.__support.FPUtil.fp_bits
     libc.src.__support.FPUtil.rounding_mode
+    libc.src.__support.big_int
     libc.src.__support.macros.optimization
     libc.src.__support.uint128
 )