There's a few instructions that GAS infers operands but Clang doesn't;
from what I can tell the Arm ARM doesn't say these are optional.

F5.1.257 TBB, TBH T1 Halfword variant
F5.1.238 STREXD T1 variant
F5.1.84 LDREXD T1 variant

Link: https://github.com/ClangBuiltLinux/linux/issues/1309Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Jian Cai <jiancai@google.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>