llvm/llvm/test/FileCheck/regex-brackets.txt

// RUN: FileCheck -input-file %s %s

op r1
op r2, [x r1]
op r3, [r1]
; CHECK:        op [[REG:r[0-9]]]
; CHECK:        op [[REG2:r[0-9]]], [x [[REG]]]
; CHECK:        op [[REG3:r[0-9]]], [[[REG]]]