[PATCH] D64304: [X86] -fno-plt: use GOT __tls_get_addr only if GOTPCRELX is enabled

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

In D64304#1579785 <https://reviews.llvm.org/D64304#1579785>, @MaskRay wrote:

> Can you share a reproduce of the Rust code?


Sorry, I missed that! The rust code is essentially the same as your C code, plus a lot of boilerplate to avoid linking libstd, otherwise the internal TLS use in libstd will already cause the linker error.

  // test2.rs
  #![crate_type="rlib"]
  #![no_std]
  #![feature(thread_local)]
  
  #[thread_local]
  static TEST: isize = 0;
  
  pub fn get_test() -> isize {
      TEST
  }
  
  // test.rs
  #![no_std]
  #![no_main]
  extern crate test2;
  
  use core::panic::PanicInfo;
  #[panic_handler]
  fn panic(_info: &PanicInfo) -> ! {
      loop {}
  }
  
  #[no_mangle]
  pub extern "C" fn _start() -> isize {
      test2::get_test()
  }

Additionally `-C link-arg=-nostartfiles` needs to be specified to avoid linking libc.

This requires a rustc build linked against LLVM 9 though, and the only public build with LLVM 9 (`rustup-toolchain-install-master 82310f68ee567093e06ad767cc0d3cb6127457ba`) already includes your patch here, otherwise rustc would be practically unusable.


Repository:
  rL LLVM

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