Create a new channel as a copy of main.
Rename main to:
Delete main? This cannot be undone.
## We currently parse but ignore .arch directives. # RUN: llvm-mc -triple=x86_64 %s | FileCheck /dev/null --implicit-check-not=.arch .arch i286 .arch generic32 .arch .avx512vl .arch .noavx512bw .arch .nop .arch .sse4.2