[clang] [llvm] [RISCV] Implement Clang Builtins for XAndesPerf Extension (PR #147018)

[Pengcheng Wang via llvm-commits]

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@@ -0,0 +1,29 @@
+//==- BuiltinsRISCVXAndes.td - RISC-V Andes Builtin database -----*- 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the Andes-specific builtin function database.  Users of
+// this file must define the BUILTIN macro to make use of this information.
+//
+//===----------------------------------------------------------------------===//
+
+class RISCVXAndesBuiltin<string prototype, string features = ""> : TargetBuiltin {
+  let Spellings = ["__builtin_riscv_nds_" # NAME];
+  let Prototype = prototype;
+  let Features = features;
+}
+
+let Attributes = [NoThrow, Const] in {
+//===----------------------------------------------------------------------===//
+// XAndesPerf extension.
+//===----------------------------------------------------------------------===//
+
+def ffb     : RISCVXAndesBuiltin<"long int(unsigned long int, unsigned long int)", "xandesperf">;
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wangpc-pp wrote:

Should we have 32/64 versions just like `clz`, `orc.b`?

https://github.com/llvm/llvm-project/pull/147018