GNU Compiler Collection (GCC) Internals: Insn Attributes

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### 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.