[llvm-dev] lld/win32 creates pic code for threadlocal

[Carlo Kok via llvm-dev]

(Forward as I sent it to the wrong list)
Hi,

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

_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. Am I missing 
something obvious, or is this a bug? it doesn't happen with llc.

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

then disassemble it.

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" }

-- 
Carlo Kok
RemObjects Software