[RISCV] Disallow target attribute use in multiversioning

[BeMg]

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.

Here is spec https://github.com/riscv-non-isa/riscv-c-api-doc/blob/master/riscv-c-api.md#__attribute__targetattr-string

[llvmbot]

@llvm/pr-subscribers-backend-risc-v

@llvm/pr-subscribers-clang

Author: Piyou Chen (BeMg)

Changes

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.

---

Full diff: https://github.com/llvm/llvm-project/pull/85899.diff

1 Files Affected:

• (modified) clang/lib/Sema/SemaDecl.cpp (+4)

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()) {

[BeMg]

The proposal could be found here riscv-non-isa/riscv-c-api-doc#48.

[kito-cheng]

Add a testcase like AArch64 https://reviews.llvm.org/D150867 ?

[topperc]

Can we share S.getASTContext().getTargetInfo().getTriple() with AArch64

[kito-cheng]

LGTM :)

[topperc]

LGTM