* Stefan Hajnoczi:
> I'm basically asking whether the &tls_var input operand is treated as
> volatile and part of the inline assembly or whether it's just regular
> C code that the compiler may optimize with the surrounding function?
&tls_var is evaluated outside of the inline assembly, any compiler
barrier will come after that. It's subject to CSE (or whatever it's
called. Three asm statements in a row
asm volatile("" : "=r"(dst_ptr) : "0"(&tls_var));
asm volatile("" : "=r"(dst_ptr) : "0"(&tls_var));
asm volatile("" : "=r"(dst_ptr) : "0"(&tls_var));
result in
movq tls_var@gottpoff(%rip), %rax
addq %fs:0, %rax
movq %rax, %rdx
movq %rax, %rdx
which is probably not what you want.
Thanks,
Florian
