[clang] [RISCV] Disallow target attribute use in multiversioning (PR #85899)

[Piyou Chen via cfe-commits]

https://github.com/BeMg created https://github.com/llvm/llvm-project/pull/85899

For RISC-V target only `target_clones` and `target_version` can enable function multiversion(FMV). 

This patch make target attribute trigger redefinition instead of emit FMV.

>From 0bbffb92e7f36957c042cab9a67a483571d9b3f9 Mon Sep 17 00:00:00 2001
From: Piyou Chen <piyou.chen at sifive.com>
Date: Mon, 18 Mar 2024 05:07:14 -0700
Subject: [PATCH] [RISCV] Disallow target attribute use in multiversioning

---
 clang/lib/Sema/SemaDecl.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 5850cd0ab6b9aa..e543aff77e67ea 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -11853,6 +11853,10 @@ static bool CheckMultiVersionFunction(Sema &S, FunctionDecl *NewFD,
   if (NewTA && S.getASTContext().getTargetInfo().getTriple().isAArch64())
     return false;
 
+  // Target attribute on RISCV is not used for multiversioning
+  if (NewTA && S.getASTContext().getTargetInfo().getTriple().isRISCV())
+    return false;
+
   if (!OldDecl || !OldDecl->getAsFunction() ||
       OldDecl->getDeclContext()->getRedeclContext() !=
           NewFD->getDeclContext()->getRedeclContext()) {