This MIPS behavior from edb9d84dcc4824865e86f963e52d67eb50dde7f5 (2010) is obsoleted and misleading. This caused confusion in https://reviews.llvm.org/D123702 ([NVPTX] Disable parens for identifiers starting with '$') Note: $tmp was rejected by AsmParser before https://reviews.llvm.org/D75111 (2020)