[libc] Add support for fma in riscv

[sivachandra]

OK from me. Please wait for @lntue to give an OK as well. If this allows you to enable more functions, you feel free to include them in the patch.

[lntue]

libc/src/__support/FPUtil/riscv64/FMA.h

2

RISCV64

10

LLVM_LIBC_SRC_SUPPORT_FPUTIL_RISCV64_FMA_H

[mikhail.ramalho]

Fix guards

libc/src/__support/FPUtil/FMA.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_RISCV64)
+#include "riscv64/FMA.h"
 #endif
 
 #else
 // FMA instructions are not available
 #include "generic/FMA.h"
 #include "src/__support/CPP/type_traits.h"
 
 namespace __llvm_libc {

libc/src/__support/FPUtil/riscv64/FMA.h

+//===-- RISCV64 implementations of the 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_SRC_SUPPORT_FPUTIL_RISCV64_FMA_H
+#define LLVM_LIBC_SRC_SUPPORT_FPUTIL_RISCV64_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_ARCH_IS_RISCV64)
+#error "Invalid include"
+#endif
+
+#if !defined(LIBC_TARGET_CPU_HAS_FMA)
+#error "FMA instructions are not supported"
+#endif
+
+#include "src/__support/CPP/type_traits.h"
+
+namespace __llvm_libc {
+namespace fputil {
+
+template <typename T>
+cpp::enable_if_t<cpp::is_same_v<T, float>, T> fma(T x, T y, T z) {
+  float result;
+  __asm__ __volatile__("fmadd.s %0, %1, %2, %3\n\t"
+                       : "=f"(result)
+                       : "f"(x), "f"(y), "f"(z));
+  return result;
+}
+
+template <typename T>
+cpp::enable_if_t<cpp::is_same_v<T, double>, T> fma(T x, T y, T z) {
+  double result;
+  __asm__ __volatile__("fmadd.d %0, %1, %2, %3\n\t"
+                       : "=f"(result)
+                       : "f"(x), "f"(y), "f"(z));
+  return result;
+}
+
+} // namespace fputil
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SUPPORT_FPUTIL_RISCV64_FMA_H

libc/src/__support/macros/properties/cpu_features.h

 #if defined(__AVX512F__)
 #define LIBC_TARGET_CPU_HAS_AVX512F
 #endif
 
 #if defined(__AVX512BW__)
 #define LIBC_TARGET_CPU_HAS_AVX512BW
 #endif
 
-#if defined(__ARM_FEATURE_FMA) || defined(__AVX2__) || defined(__FMA__)
+#if defined(__ARM_FEATURE_FMA) || defined(__AVX2__) || defined(__FMA__) ||     \
+    defined(__riscv)
 #define LIBC_TARGET_CPU_HAS_FMA
 #endif
 
 #endif // LLVM_LIBC_SRC_SUPPORT_MACROS_PROPERTIES_CPU_FEATURES_H