================
@@ -4114,8 +4114,26 @@ void CodeGenModule::emitMultiVersionFunctions() {
}
llvm::Constant *ResolverConstant = GetOrCreateMultiVersionResolver(GD);
- if (auto *IFunc = dyn_cast<llvm::GlobalIFunc>(ResolverConstant))
+ if (auto *IFunc = dyn_cast<llvm::GlobalIFunc>(ResolverConstant)) {
ResolverConstant = IFunc->getResolver();
+ // In Aarch64, default versions of multiversioned functions are mangled
to
+ // their 'normal' assembly name. This deviates from other targets which
+ // append a '.default' string. As a result we need to continue appending
+ // .ifunc in Aarch64.
+ // FIXME: Should Aarch64 mangling for 'default' multiversion function and
+ // in turn ifunc function match that of other targets?
----------------
jroelofs wrote:
I have been meaning to file an issue about this. Not using a different mangling
means you always get the default version when referencing a multi-versioned
function outside of the TU.
Consider e.g:
```
PublicHeader.h:
int versioned(void);
void *inside_TU();
void *outside_TU();
---
TUA.c:
#include "PublicHeader.h"
__attribute__((target_version("simd")))
int versioned(void) { return 1; }
__attribute__((target_version("default")))
int versioned(void) { return 2; }
void *inside_TU(void) { return versioned; }
---
TUB.c:
#include "PublicHeader.h"
void *outside_TU(void) { return versioned; }
---
Check.c:
#include "PublicHeader.h"
int main() { return inside_TU() == outside_TU(); }
```
@rsandifo-arm brought up a similar case on x86:
```
__attribute__((target("avx2")))
int versioned(void) { return 1; }
__attribute__((target("default")))
int versioned(void) { return 2; }
int (*inside_TU(void))(void) { return versioned; }
```
If we fix this, we should definitely make sure both the ACLE folks, and GCC are
on board, and that the fix makes sense in the context of other targets.
https://github.com/llvm/llvm-project/pull/71706
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