<html>
    <head>
      <base href="https://llvm.org/bugs/" />
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - R_X86_64_REX_GOTPCRELX is not produced"
   href="https://llvm.org/bugs/show_bug.cgi?id=27913">27913</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>R_X86_64_REX_GOTPCRELX is not produced
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>libraries
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>MC
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>grimar@accesssoftek.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Created <span class=""><a href="attachment.cgi?id=16428" name="attach_16428" title="testcase">attachment 16428</a> <a href="attachment.cgi?id=16428&action=edit" title="testcase">[details]</a></span>
testcase

Using the attached testcase and following commandline:
llvm-mc -relax-relocations -filetype=obj -triple=x86_64-pc-linux test.s -o test

I am observing only R_X86_64_GOTPCRELX relocations in output:

Relocations [
  Section (3) .rela.text {
    0x2 R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x8 R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0xE R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x14 R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x1A R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x20 R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x26 R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x2D R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x34 R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x3B R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x42 R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x49 R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x50 R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x57 R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x5E R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x65 R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x6C R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x73 R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x79 R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0x7F R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0x85 R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0x8B R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0x91 R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0x97 R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0x9D R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xA4 R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xAB R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xB2 R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xB9 R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xC0 R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xC7 R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xCE R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xD5 R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xDC R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xE3 R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xEA R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
  }

when gas output is:

(as --64 -mrelax-relocations=yes test.s -o test)
Relocations [
  Section (2) .rela.text {
    0x2 R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x8 R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0xE R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x14 R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x1A R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x20 R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x26 R_X86_64_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x2D R_X86_64_REX_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x34 R_X86_64_REX_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x3B R_X86_64_REX_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x42 R_X86_64_REX_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x49 R_X86_64_REX_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x50 R_X86_64_REX_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x57 R_X86_64_REX_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x5E R_X86_64_REX_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x65 R_X86_64_REX_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x6C R_X86_64_REX_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x73 R_X86_64_REX_GOTPCRELX bar 0xFFFFFFFFFFFFFFFC
    0x79 R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0x7F R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0x85 R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0x8B R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0x91 R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0x97 R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0x9D R_X86_64_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xA4 R_X86_64_REX_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xAB R_X86_64_REX_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xB2 R_X86_64_REX_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xB9 R_X86_64_REX_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xC0 R_X86_64_REX_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xC7 R_X86_64_REX_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xCE R_X86_64_REX_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xD5 R_X86_64_REX_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xDC R_X86_64_REX_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xE3 R_X86_64_REX_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
    0xEA R_X86_64_REX_GOTPCRELX foo 0xFFFFFFFFFFFFFFFC
  }</pre>
        </div>
      </p>
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