16.19 Instruction Attributes

In addition to describing the instruction supported by the target machine, the md file also defines a group of attributes and a set of values for each. Every generated insn is assigned a value for each attribute. One possible attribute would be the effect that the insn has on the machine's condition code. This attribute can then be used by NOTICE_UPDATE_CC to track the condition codes.

• Defining Attributes: Specifying attributes and their values.
• Expressions: Valid expressions for attribute values.
• Tagging Insns: Assigning attribute values to insns.
• Attr Example: An example of assigning attributes.
• Insn Lengths: Computing the length of insns.
• Constant Attributes: Defining attributes that are constant.
• Mnemonic Attribute: Obtain the instruction mnemonic as attribute value.
• Delay Slots: Defining delay slots required for a machine.
• Processor pipeline description: Specifying information for insn scheduling.