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15.15: 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.
  • Delay Slots Defining delay slots required for a machine.
  • Function Units Specifying information for insn scheduling.