[llvm-bugs] [Bug 31576] New: lgdt op doesn't work in code16 block

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=31576

            Bug ID: 31576
           Summary: lgdt op doesn't work in code16 block
           Product: libraries
           Version: 3.9
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: LLVM assembly language parser
          Assignee: unassignedbugs at nondot.org
          Reporter: funfunctor at folklore1984.net
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

Created attachment 17817
  --> https://llvm.org/bugs/attachment.cgi?id=17817&action=edit
lgdt in code16 block usage

Hi,

In librecore/coreboot we require the use of lgdt to get us from code16
real-mode to code32 protected-mode.

The following attached reduced test case doesn't compile with the integrated-as
of LLVM however works with binutils.

GNU as assembles it as follows:

reduced-test-case-as.o:     file format elf64-x86-64


Disassembly of section .text:

0000000000000000 <gdtaddr>:
   0:    00 00                    add    %al,(%rax)
   2:    00 00                    add    %al,(%rax)
   4:    00 00                    add    %al,(%rax)
   6:    66 0f 01 16              data16 lgdt (%rsi)
    ...

$ llvm-as-3.9 --version
 LLVM version 3.9.1

Kind Regards,
Edward.

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