cmd/compile: add support for arm64 bit-test instructions
Add support for generating TBZ/TBNZ instructions.
The bit-test-and-branch pattern shows up in a number of
important places, including the runtime (gc bitmaps).
Before this change, there were 3 TB[N]?Z instructions in the Go tool,
all of which were in hand-written assembly. After this change, there
are 285. Also, the go1 benchmark binary gets about 4.5kB smaller.
Fixes #21361
Change-Id: I170c138b852754b9b8df149966ca5e62e6dfa771
Reviewed-on: https://go-review.googlesource.com/54470
Run-TryBot: Philip Hofer <phofer@umich.edu>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>