[AArch64][FMV] Prevent target attribute using for multiversioning.

[ilinpv]

Summary

On AArch64 for function multiversioning target_version/target_clones attributes should be used. The patch fixes the defect allowing target attribute to cause multiversioning.

[danielkiss]

LGTM

[Allen]

clang/lib/Sema/SemaDecl.cpp

11544

I find the attribute target_clones/target_version also not be used to generate multiversioning function? https://godbolt.org/z/cYWsbrPn9
so it is not support on AArch64 ?

[ilinpv]

clang/lib/Sema/SemaDecl.cpp

11544

Function multiversioning depends on compiler-rt library, specify --rtlib=compiler-rt to make it work.

clang/lib/Sema/SemaDecl.cpp

if (MVKind != MultiVersionKind::None &&
           NewTVA->isDefaultVersion())) {
       S.Diag(NewFD->getLocation(), diag::err_multiversion_not_allowed_on_main);
       NewFD->setInvalidDecl();
       return true;
     }
     return false;
   }
 
+  // Target attribute on AArch64 is not used for multiversioning
+  if (NewTA && S.getASTContext().getTargetInfo().getTriple().isAArch64())
+    return false;
+
   if (!OldDecl || !OldDecl->getAsFunction() ||
       OldDecl->getDeclContext()->getRedeclContext() !=
           NewFD->getDeclContext()->getRedeclContext()) {
     // If there's no previous declaration, AND this isn't attempting to cause
     // multiversioning, this isn't an error condition.
     if (MVKind == MultiVersionKind::None)
       return false;
     return CheckMultiVersionFirstFunction(S, NewFD);

clang/test/Sema/attr-target-version.c

 //expected-error@+2 {{redefinition of 'dup1'}}
 //expected-note@-2 {{previous definition is here}}
 int dup1(void) { return 2; }
 
 int __attribute__((target_version("aes"))) foo(void) { return 1; }
 //expected-note@+1 {{previous definition is here}}
 int __attribute__((target_version("default"))) foo(void) { return 2; }
 
-//expected-note@+1 {{previous declaration is here}}
+//expected-note@+1 {{previous definition is here}}
 int __attribute__((target_version("sha3 + pmull "))) foo(void) { return 1; }
+//expected-note@-1 {{previous definition is here}}
 
-//expected-error@+1 {{multiversioning attributes cannot be combined}}
+//expected-error@+1 {{redefinition of 'foo'}}
 int __attribute__((target("dotprod"))) foo(void) { return -1; }
+//expected-warning@-1 {{attribute declaration must precede definition}}
 
 //expected-error@+1 {{redefinition of 'foo'}}
 int foo(void) { return 2; }
 
+//expected-note@+1 {{previous definition is here}}
+__attribute__ ((target("bf16,sve,sve2,dotprod"))) int func(void) { return 1; }
+//expected-error@+1 {{redefinition of 'func'}}
+__attribute__ ((target("default"))) int func(void) { return 0; }
+
 //expected-note@+1 {{previous declaration is here}}
 void __attribute__((target_version("bti+flagm2"))) one(void) {}
 //expected-error@+1 {{multiversioned function redeclarations require identical target attributes}}
 void __attribute__((target_version("flagm2+bti"))) one(void) {}
 
 void __attribute__((target_version("ssbs+sha1"))) two(void) {}
 void __attribute__((target_version("ssbs+fp16fml"))) two(void) {}