Optimize tls_get_addr_common(). The change provides around 30% speedup for TLS microbenchmark using global-dynamic TLS model on amd64 (which is default for PIC dso objects).
Optimize tls_get_addr_common(). The change provides around 30% speedup
for TLS microbenchmark using global-dynamic TLS model on amd64 (which is
default for PIC dso objects).

Split the slow path into tls_get_addr_slow(), for which inlining is
disabled. This prevents the registers spill on tls_get_addr_common()
entry.

Provide static branch hint to the compiler, indicating that slow path
is not likely to be taken.

While there, do some minimal style adjustments.

Reported and tested by:	davidxu
MFC after:	1 week

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase