[llvm-bugs] [Bug 35022] New: some vtable symbol refs use GOT despite hidden visibility

via llvm-bugs llvm-bugs at lists.llvm.org
Sat Oct 21 04:21:13 PDT 2017


https://bugs.llvm.org/show_bug.cgi?id=35022

            Bug ID: 35022
           Summary: some vtable symbol refs use GOT despite hidden
                    visibility
           Product: clang
           Version: trunk
          Hardware: PC
                OS: other
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: LLVM Codegen
          Assignee: unassignedclangbugs at nondot.org
          Reporter: roland at hack.frob.com
                CC: llvm-bugs at lists.llvm.org, phosek at chromium.org

The attached input file starts with:
  #pragma GCC visibility push(hidden)
so all definitions and all external references should be treated as if they had
individual __attribute__((visibility("hidden"))).  Hence there should be no GOT
references.

However, it generates a GOT reference for _ZTV21BlockingPortAllocator, a C++
vtable symbol.

In the attached .ll file, the symbol is declared:
  @_ZTV21BlockingPortAllocator = external unnamed_addr constant { [6 x i8*] }

I think this is where "hidden" is missing, so it appears to be a Clang issue
rather than a backend issue.

The test case is for x86-64 but I'm having the same issue on aarch64 too.

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