Fork channel

Create a new channel as a copy of main.

Rename channel

Rename main to:

Delete channel

Delete main? This cannot be undone.

X86_64-pku.s
// RUN: llvm-mc -triple x86_64-unknown-unknown --show-encoding < %s | FileCheck %s
// CHECK: rdpkru
// CHECK: encoding: [0x0f,0x01,0xee]
   rdpkru

// CHECK: wrpkru
// CHECK: encoding: [0x0f,0x01,0xef]
   wrpkru