[llvm-bugs] [Bug 34306] New: Odd PC rel for thread local

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=34306

            Bug ID: 34306
           Summary: Odd  PC rel for thread local
           Product: lld
           Version: unspecified
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: COFF
          Assignee: unassignedbugs at nondot.org
          Reporter: ck at remobjects.com
                CC: llvm-bugs at lists.llvm.org

With latest llvm/lld on Win32 (link flavor) I get an odd PC rel for thread
local statics:

_GetCurrent:
  402000:       55      pushl   %ebp
  402001:       89 e5   movl    %esp, %ebp
  402003:       e8 00 00 00 00  calll   0 <_GetCurrent+0x8>
  402008:       58      popl    %eax
  402009:       8b 88 00 10 40 00       movl    4198400(%eax), %ecx
  40200f:       64 8b 80 2c 00 00 00    movl    %fs:44(%eax), %eax
  402016:       8b 04 88        movl    (%eax,%ecx,4), %eax
  402019:       8b 80 00 00 00 00       movl    (%eax), %eax
  40201f:       5d      popl    %ebp
  402020:       c3      retl

notice 402009, which does a movl 4198400 (_tls_index)%eax, %ecx, where %eax is
PC, this crashes here and I'm having trouble seeing how this would ever work
since 4198400 is already the real address.


Steps:
- llvm-as.exe isl.out.ll
- lld.exe -flavor link isl.out.bc /entry:main /debug  /opt:lldlto=0 /force

then disassemble it.

(Note that /force is only here for testcase purposes, it fails in a full
project without /force too)

Code:

; ModuleID = 'isl.out'
source_filename = "Island"
target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
target triple = "i686-pc-windows-msvc"

module asm ".globl _tls_array\0D"
module asm "_tls_array = 44\0D"
module asm ".globl __tls_array\0D"
module asm "__tls_array = 44"

@_tls_index = global i32 0


@fCurrent = thread_local global i8* null

define i8* @GetCurrent() #0 {
  br label %1

; <label>:1:                                      ; preds = %0
  %2 = load i8*, i8** @fCurrent
  ret i8* %2
}

declare void @DoSomething(i8*)

define void @main() {
  %1 =  call i8* @GetCurrent()
  call void @DoSomething(i8* %1)
  ret void
}

attributes #0 = { "no-frame-pointer-elim"="true"
"no-frame-pointer-elim-non-leaf" }

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