[libc] Use __builtin_fma(f) by default if LIBC_TARGET_CPU_HAS_FMA is defined. (llvm#91535)

Author: lntue

libc/src/__support/FPUtil/FMA.h

@@ -9,25 +9,31 @@
 #ifndef LLVM_LIBC_SRC___SUPPORT_FPUTIL_FMA_H
 #define LLVM_LIBC_SRC___SUPPORT_FPUTIL_FMA_H
 
+#include "src/__support/CPP/type_traits.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)
 
-#if defined(LIBC_TARGET_ARCH_IS_X86_64)
-#include "x86_64/FMA.h"
-#elif defined(LIBC_TARGET_ARCH_IS_AARCH64)
-#include "aarch64/FMA.h"
-#elif defined(LIBC_TARGET_ARCH_IS_ANY_RISCV)
-#include "riscv/FMA.h"
-#elif defined(LIBC_TARGET_ARCH_IS_GPU)
-#include "gpu/FMA.h"
-#endif
+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 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);
+}
+
+} // namespace fputil
+} // namespace LIBC_NAMESPACE
 
 #else
 // FMA instructions are not available
 #include "generic/FMA.h"
-#include "src/__support/CPP/type_traits.h"
 
 namespace LIBC_NAMESPACE {
 namespace fputil {

libc/src/__support/FPUtil/aarch64/FMA.h

@@ -913,17 +913,9 @@ fma_common_hdrs = [
     "src/__support/FPUtil/generic/FMA.h",
 ]
 
-fma_platform_hdrs = [
-    "src/__support/FPUtil/x86_64/FMA.h",
-    "src/__support/FPUtil/aarch64/FMA.h",
-]
-
 libc_support_library(
     name = "__support_fputil_fma",
     hdrs = fma_common_hdrs,
-    # These are conditionally included and will #error out if the platform
-    # doesn't support FMA, so they can't be compiled on their own.
-    textual_hdrs = fma_platform_hdrs,
     deps = [
         ":__support_cpp_bit",
         ":__support_cpp_type_traits",