[ELF][test] Add test coverage of TLS to gc-sections.s

[MaskRay]

LG. Worth waiting for @grimar

[grimar]

LGTM too.

lld/test/ELF/gc-sections.s

 # REQUIRES: x86
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: ld.lld %t -o %t2
 # RUN: llvm-readobj --sections --symbols %t2 | FileCheck -check-prefix=NOGC %s
 # RUN: ld.lld --gc-sections %t -o %t2
 # RUN: llvm-readobj --sections --symbols %t2 | FileCheck -check-prefix=GC1 %s
 # RUN: ld.lld --export-dynamic --gc-sections %t -o %t2
 # RUN: llvm-readobj --sections --symbols %t2 | FileCheck -check-prefix=GC2 %s
 
 # NOGC: Name: .eh_frame
 # NOGC: Name: .text
 # NOGC: Name: .init
 # NOGC: Name: .fini
+# NOGC: Name: .tdata
+# NOGC: Name: .tbss
 # NOGC: Name: .ctors
 # NOGC: Name: .dtors
 # NOGC: Name: .debug_pubtypes
 # NOGC: Name: .comment
 # NOGC: Name: a
 # NOGC: Name: b
 # NOGC: Name: c
+# NOGC: Name: e
+# NOGC: Name: f
+# NOGC: Name: g
+# NOGC: Name: h
 # NOGC: Name: x
 # NOGC: Name: y
 # NOGC: Name: d
 
 # GC1:     Name: .eh_frame
 # GC1:     Name: .text
 # GC1:     Name: .init
 # GC1:     Name: .fini
+# GC1:     Name: .tdata
+# GC1:     Name: .tbss
 # GC1:     Name: .ctors
 # GC1:     Name: .dtors
 # GC1:     Name: .debug_pubtypes
 # GC1:     Name: .comment
 # GC1:     Name: a
 # GC1:     Name: b
 # GC1:     Name: c
+# GC1:     Name: e
+# GC1-NOT: Name: f
+# GC1:     Name: g
+# GC1-NOT: Name: h
 # GC1-NOT: Name: x
 # GC1-NOT: Name: y
 # GC1-NOT: Name: d
 
 # GC2:     Name: .eh_frame
 # GC2:     Name: .text
 # GC2:     Name: .init
 # GC2:     Name: .fini
+# GC2:     Name: .tdata
+# GC2:     Name: .tbss
 # GC2:     Name: .ctors
 # GC2:     Name: .dtors
 # GC2:     Name: .debug_pubtypes
 # GC2:     Name: .comment
 # GC2:     Name: a
 # GC2:     Name: b
 # GC2:     Name: c
+# GC2:     Name: e
+# GC2-NOT: Name: f
+# GC2:     Name: g
+# GC2-NOT: Name: h
 # GC2-NOT: Name: x
 # GC2-NOT: Name: y
 # GC2:     Name: d
 
 .globl _start, d
-.protected a, b, c, x, y
+.protected a, b, c, e, f, g, h, x, y
 _start:
   call a
 
 .section .text.a,"ax",@progbits
 a:
   call _start
   call b
 
 .section .text.b,"ax",@progbits
 b:
+  leaq e@tpoff(%rax),%rdx
   call c
 
 .section .text.c,"ax",@progbits
 c:
-  nop
+  leaq g@tpoff(%rax),%rdx
 
 .section .text.d,"ax",@progbits
 d:
   nop
 
 .section .text.x,"ax",@progbits
 x:
   call y
 
 .section .text.y,"ax",@progbits
 y:
   call x
 
+.section .tbss.e,"awT",@nobits
+e:
+  .quad 0
+
+.section .tbss.f,"awT",@nobits
+f:
+  .quad 0
+
+.section .tdata.g,"awT",@progbits
+g:
+  .quad 0
+
+.section .tdata.h,"awT",@progbits
+h:
+  .quad 0
+
 .section .ctors,"aw",@progbits
   .quad 0
 
 .section .dtors,"aw",@progbits
   .quad 0
 
 .section .init,"aw",@init_array
   .quad 0