[Bug inline-asm/65859] New: Optimizes out TLS variable called in a child function

[mike at cchtml dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65859

            Bug ID: 65859
           Summary: Optimizes out TLS variable called in a child function
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: inline-asm
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mike at cchtml dot com

Created attachment 35391
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35391&action=edit
test case

When compiled with -O0 the test case compiles. When compiled with -O1 the test
case will not compile with an error for an undefined reference to the TLS
variable. If you move the THREAD_VAR_OFFSET macro call to main() gcc will
compile without error. Enabling -O1 and turning off optimizations by hand does
not change the result.

I see the same issue with gcc 4.8, 4.9, and 5.0.