docs/devel/decodetree.rst

18 immediates, and sub-opcodes.
20 In support of patterns, one may declare *fields*, *argument sets*, and
21 *formats*, each of which may be re-used to simplify further definitions.
33 For *unnamed_field*, the first number is the least-significant bit position
54 In this way one can define disjoint fields.
59 One may use ``!function`` with zero ``fields``.  This case is called
67 +---------------------------+---------------------------------------------+
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82 |   !function=expand_sz_imm |               extract(a->sz, 0, 3))         |
83 +---------------------------+---------------------------------------------+
100 with each of the fields being one of the member arguments.
105 Argument sets are useful when one wants to define helper functions
126   fixedbit_elt := [01.-]+
131 Defining a format is a handy way to avoid replicating groups of fields
135 be 1, 0, or don't care.  The difference between '.' and '-'
137 final 0 or 1 from the pattern, and '-' means that the bit is really
145 Padding with a *fixedbit_elt* of all '.' is an easy way to accomplish that.
147 A *field_ref* incorporates a field by reference.  This is the only way to
154 the argument set.  If an argument set is not specified, one will be
177 A pattern that does not specify a named format will have one inferred
181 come in handy when fields overlap between patterns and one has to
208 A *group* begins with a lone open-brace or open-bracket, with all
210 close-brace or close-bracket.  Groups may be nested, increasing the
220 Patterns within no-overlap groups are not allowed to overlap, just
221 the same as ungrouped patterns.  Thus no-overlap groups are intended
224 The following example from PA-RISC shows specialization of the *or*
229       nop   000010 ----- ----- 0000 001001 0 00000