[PATCH] D54016: [X86] don't allow X86_64 PIC mode addresses to be used as immediates

[Reid Kleckner via Phabricator via llvm-commits]

rnk added a comment.

Here is the original test case from the PR:

  #include <stdio.h>
  int offset = 0;
  static void foo2() { printf("foo2 is called\n"); }
  void foo() {
    __asm__ volatile("movq %0,%%gs:(%1)" : : "ir"((void *)&foo2), "r"(offset));
    printf("foo is called\n");
  }

If you compile with GCC, you will see that it generates the same assembly that LLVM does:

  foo:
  .LFB15:
          .cfi_startproc
          subq    $8, %rsp
          .cfi_def_cfa_offset 16
          movl    offset(%rip), %eax
  #APP
  # 21 "t.c" 1
          movq $foo2,%gs:(%eax)
  # 0 "" 2
  #NO_APP
          leaq    .LC1(%rip), %rdi
          call    puts at PLT
          addq    $8, %rsp
          .cfi_def_cfa_offset 8
          ret
          .cfi_endproc

So, I think LLVM is already correct here. You can confirm on compiler explorer: https://gcc.godbolt.org/z/rOHCb6


Repository:
  rL LLVM

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  https://reviews.llvm.org/D54016/new/

https://reviews.llvm.org/D54016