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Created page with 'Category:Computer Architecture The encoding of instructions, which is a key aspect of an Instruction Set Architecture, defines how instuctions and arguments are encoded a…'
[[Category:Computer Architecture]]
The encoding of instructions, which is a key aspect of an [[Instruction Set Architecture]], defines how instuctions and arguments are encoded as binary values in the [[Machine Language|machine code]] of a system.
Some architectures encode instructions as multi-byte sequences, where one or more bytes specify the operation to be performed and the [[Addressing Mode|addressing mode(s)]] to be used, and additional bytes specify the operands (such as the register numbers, immediate values, addresses, or offsets to be used). Other architectures encode instructions as fixed-length bitfields, where various (and varying) subfields within the bitfield specify the operation, addressing mode(s), and operands.
The x86_64 architecture uses variable-length byte sequences, from 1 to approximately 17 bytes.
The AArch64 architecture uses 32-bit long instructions. Since this instruction length is insufficient to adequately contain a 64-bit operand (such as an address), some operands are encoded using run-length encoding (RLL) or shifted-bitfield techniques. For certain operand values, it may be necessary to build the required value in a register with a few instructions.
The encoding of instructions, which is a key aspect of an [[Instruction Set Architecture]], defines how instuctions and arguments are encoded as binary values in the [[Machine Language|machine code]] of a system.
Some architectures encode instructions as multi-byte sequences, where one or more bytes specify the operation to be performed and the [[Addressing Mode|addressing mode(s)]] to be used, and additional bytes specify the operands (such as the register numbers, immediate values, addresses, or offsets to be used). Other architectures encode instructions as fixed-length bitfields, where various (and varying) subfields within the bitfield specify the operation, addressing mode(s), and operands.
The x86_64 architecture uses variable-length byte sequences, from 1 to approximately 17 bytes.
The AArch64 architecture uses 32-bit long instructions. Since this instruction length is insufficient to adequately contain a 64-bit operand (such as an address), some operands are encoded using run-length encoding (RLL) or shifted-bitfield techniques. For certain operand values, it may be necessary to build the required value in a register with a few instructions.