lp64, which decides the generated object file in ELF32 and ELF64 format respectively. The default is
xgene2. The special name
allmay be used to allow the assembler to accept instructions valid for any supported processor, including all optional extensions.
In addition to the basic instruction set, the assembler can be told to accept, or restrict, various extension mnemonics that extend the processor. See AArch64 Extensions.
If some implementations of a particular processor can have an extension, then then those extensions are automatically enabled. Consequently, you will not normally have to specify any additional extensions.
If both -mcpu and -march are specified, the assembler will use the setting for -mcpu. If neither are specified, the assembler will default to -mcpu=all.
The architecture option can be extended with the same instruction set extension options as the -mcpu option. Unlike -mcpu, extensions are not always enabled by default, See AArch64 Extensions.