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17 Machine Descriptions ¶

A machine description has two parts: a file of instruction patterns (.md file) and a C header file of macro definitions.

The .md file for a target machine contains a pattern for each instruction that the target machine supports (or at least each instruction that is worth telling the compiler about). It may also contain comments. A semicolon causes the rest of the line to be a comment, unless the semicolon is inside a quoted string.

See the next chapter for information on the C header file.

• Overview of How the Machine Description is Used
• Everything about Instruction Patterns
• Example of define_insn
• RTL Template
• Output Templates and Operand Substitution
• C Statements for Assembler Output
• Predicates
• Operand Constraints
• Standard Pattern Names For Generation
• When the Order of Patterns Matters
• Interdependence of Patterns
• Defining Jump Instruction Patterns
• Defining Looping Instruction Patterns
• Canonicalization of Instructions
• Defining RTL Sequences for Code Generation
• Defining How to Split Instructions
• Including Patterns in Machine Descriptions.
• Machine-Specific Peephole Optimizers
• Instruction Attributes
• Conditional Execution
• RTL Templates Transformations
• Constant Definitions
• Iterators