gccint: Machine Desc

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1 17 Machine Descriptions
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1 A machine description has two parts: a file of instruction patterns
1 ('.md' file) and a C header file of macro definitions.
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1  The '.md' file for a target machine contains a pattern for each
1 instruction that the target machine supports (or at least each
1 instruction that is worth telling the compiler about).  It may also
1 contain comments.  A semicolon causes the rest of the line to be a
1 comment, unless the semicolon is inside a quoted string.
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1  See the next chapter for information on the C header file.
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· Overview            How the machine description is used.
· Patterns            How to write instruction patterns.
· Example             An explained example of a 'define_insn' pattern.
· RTL Template        The RTL template defines what insns match a pattern.
· Output Template     The output template says how to make assembler code
1                         from such an insn.
· Output Statement    For more generality, write C code to output
1                         the assembler code.
· Predicates          Controlling what kinds of operands can be used
1                         for an insn.
· Constraints         Fine-tuning operand selection.
· Standard Names      Names mark patterns to use for code generation.
· Pattern Ordering    When the order of patterns makes a difference.
· Dependent Patterns  Having one pattern may make you need another.
· Jump Patterns       Special considerations for patterns for jump insns.
· Looping Patterns    How to define patterns for special looping insns.
· Insn CanonicalizationsCanonicalization of Instructions
· Expander DefinitionsGenerating a sequence of several RTL insns
1                         for a standard operation.
· Insn Splitting      Splitting Instructions into Multiple Instructions.
· Including Patterns  Including Patterns in Machine Descriptions.
· Peephole DefinitionsDefining machine-specific peephole optimizations.
· Insn Attributes     Specifying the value of attributes for generated insns.
· Conditional ExecutionGenerating 'define_insn' patterns for
1                          predication.
· Define Subst        Generating 'define_insn' and 'define_expand'
1 			patterns from other patterns.
· Constant DefinitionsDefining symbolic constants that can be used in the
1                         md file.
· Iterators           Using iterators to generate patterns from a template.
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