https://bugs.llvm.org/show_bug.cgi?id=42542
Bug ID: 42542
Summary: ThinLTO on Aarch64 fails to handle aliases to
overridden weak functions
Product: new-bugs
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: new bugs
Assignee: unassignedb...@nondot.org
Reporter: samitolva...@google.com
CC: htmldevelo...@gmail.com, llvm-bugs@lists.llvm.org
C code that defines an alias to a weak function, which is then referred to in
assembly code that also overrides the same weak function, fails to compile with
-flto=thin on Aarch64:
$ cat alias.c
__attribute__((__weak__)) int __a(int n)
{
return n;
}
int a(int n) __attribute__((__alias__("__a")));
int main()
{
return __a(0);
}
$ cat alias.s
.arch armv8-a
__a:
b a
.globl __a
$ clang -flto=thin -fvisibility=hidden -fuse-ld=lld --target=aarch64-linux-gnu-
alias.s alias.c
Alias must point to a definition
i32 (i32)* @a
LLVM ERROR: Broken module found, compilation aborted!
clang-9: error: linker command failed with exit code 1 (use -v to see
invocation)
Using -flto instead of -flto=thin works.
This bug prevents us from compiling the Linux kernel with ThinLTO, as explained
here:
https://github.com/ClangBuiltLinux/linux/issues/509
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