| GNU Compiler Collection (GCC) Internals: Insn Attributes |
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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. |