mirror of
https://github.com/UberGames/ioef.git
synced 2024-12-11 05:11:29 +00:00
179 lines
4.7 KiB
Groff
179 lines
4.7 KiB
Groff
.TH LBURG 1 "local \- 11/30/94"
|
|
.\" $Id: lburg.1 145 2001-10-17 21:53:10Z timo $
|
|
.SH NAME
|
|
lburg \- lcc's code-generator generator
|
|
.SH SYNOPSIS
|
|
.B lburg
|
|
[
|
|
.I option
|
|
]...
|
|
[ [
|
|
.I input
|
|
]
|
|
.I output
|
|
]
|
|
.br
|
|
.SH DESCRIPTION
|
|
.PP
|
|
.I lburg
|
|
reads an lcc-style BURG specification from
|
|
.I input
|
|
and writes a pattern-matching code generator to
|
|
.IR output .
|
|
If
|
|
.I input
|
|
is `\-' or is omitted,
|
|
.I lburg
|
|
reads the standard input;
|
|
If
|
|
.I output
|
|
is `\-' or is omitted,
|
|
.I lburg
|
|
writes to the standard output.
|
|
.PP
|
|
.I lburg
|
|
accepts specifications that conform to the following EBNF grammar.
|
|
Terminals are enclosed in single quotes or are
|
|
given in uppercase, all other symbols are nonterminals or English phrases,
|
|
{X} denotes zero or more instances of X, and [X] denotes an optional X.
|
|
.PP
|
|
.nf
|
|
.RS
|
|
.ft CW
|
|
spec: `%{' configuration `%}' { dcl } `%%' { rule }
|
|
[ `%%' C code ]
|
|
|
|
dcl: `%start' nonterm
|
|
`%term' { ID `=' INT }
|
|
|
|
rule: nonterm `:' tree template [ C expression ]
|
|
|
|
tree: term `(' tree `,' tree `)'
|
|
term `(' tree `)'
|
|
term
|
|
nonterm
|
|
|
|
nonterm: ID
|
|
|
|
template: `"' { any character except double quote } `"'
|
|
.RE
|
|
.fi
|
|
.PP
|
|
Specifications are structurally similar to
|
|
.IR yacc 's.
|
|
Text between
|
|
`\f(CW%{\fP'
|
|
and
|
|
`\f(CW%}\fP'
|
|
is called the configuration section; there may be several such segments.
|
|
All are concatenated and copied verbatim into the head of the output.
|
|
Text after the second
|
|
`\f(CW%%\fP',
|
|
if any, is also copied verbatim into the output, at the end.
|
|
.PP
|
|
Specifications consist of declarations, a
|
|
`\f(CW%%\fP'
|
|
separator, and rules.
|
|
Input is line-oriented; each declaration and rule must appear on a separate line,
|
|
and declarations must begin in column 1.
|
|
Declarations declare terminals \(em the operators in subject
|
|
trees \(em and associate a unique, positive external symbol
|
|
number with each one.
|
|
Nonterminals are declared by their presence
|
|
on the left side of rules. The
|
|
\f(CW%start\fP
|
|
declaration optionally declares a nonterminal as the start symbol.
|
|
In the grammar above,
|
|
\f(CWterm\fP
|
|
and
|
|
\f(CWnonterm\fP
|
|
denote identifiers that are terminals and nonterminals.
|
|
.PP
|
|
Rules define tree patterns in a fully parenthesized prefix
|
|
form. Every nonterminal denotes a tree.
|
|
Each operator has a fixed
|
|
arity, which is inferred from the rules in which it is used.
|
|
A chain rule is a rule whose pattern is another nonterminal.
|
|
If no start symbol is declared, the nonterminal defined by the first rule is used.
|
|
.PP
|
|
Each rule ends with an expression that computes the cost of matching
|
|
that rule; omitted costs
|
|
default to zero. Costs of chain rules must be constants.
|
|
.PP
|
|
The configuration section configures the output
|
|
for the trees being parsed and the client's environment.
|
|
As shown, this section must define
|
|
\f(CWNODEPTR_TYPE\fP
|
|
to be a visible typedef symbol for a pointer to a
|
|
node in the subject tree.
|
|
The labeller invokes
|
|
\f(CWOP_LABEL(p)\fP,
|
|
\f(CWLEFT\_CHILD(p)\fP, and
|
|
\f(CWRIGHT\_CHILD(p)\fP
|
|
to read the operator and children from the node pointed to by \f(CWp\fP.
|
|
If the configuration section defines these operations as macros, they are implemented in-line;
|
|
otherwise, they must be implemented as functions.
|
|
.PP
|
|
The matcher
|
|
computes and stores a single integral state in each node of the subject tree.
|
|
The configuration section must define a macro
|
|
\f(CWSTATE_LABEL(p)\fP
|
|
to access the state field of the node pointed to
|
|
by \f(CWp\fP. It must be large enough to hold a pointer, and
|
|
a macro is required because it is used as an lvalue.
|
|
.PP
|
|
.SH OPTIONS
|
|
.TP
|
|
.BI \-p \ prefix
|
|
.br
|
|
.ns
|
|
.TP
|
|
.BI \-p prefix
|
|
Use
|
|
.I prefix
|
|
as the disambiquating prefix for visible names and fields.
|
|
The default is `\f(CW_\fP'.
|
|
.TP
|
|
.B \-T
|
|
Arrange for
|
|
.sp
|
|
.nf
|
|
.ft CW
|
|
void _trace(NODEPTR_TYPE p, int eruleno,
|
|
int cost, int bestcost);
|
|
.sp
|
|
.fi
|
|
.ft R
|
|
to be called at each successful match.
|
|
\f(CWp\fP
|
|
identifies the node and
|
|
\f(CWeruleno\fP
|
|
identifies the matching rule; the rules are numbered
|
|
beginning at 1 in the order they appear in the input.
|
|
\f(CWcost\fP
|
|
is the cost of the match and
|
|
\f(CWbestcost\fP
|
|
is the cost of the best previous match. The current match
|
|
wins only if
|
|
\f(CWcost\fP
|
|
is less than \f(CWbestcost\fP.
|
|
32767 represents the infinite cost of no previous match.
|
|
\f(CW_trace\fP must be declared in the configuration section.
|
|
.SH "SEE ALSO"
|
|
.IR lcc (1)
|
|
.PP
|
|
C. W. Fraser and D. R. Hanson,
|
|
.IR A Retargetable C Compiler: Design and Implementation ,
|
|
Benjamin/Cummings, Redwood City, CA, 1995,
|
|
ISBN 0-8053-1670-1. Chapter 14.
|
|
.PP
|
|
C. W. Fraser, D. R. Hanson and T. A. Proebsting,
|
|
`Engineering a simple, efficient code generator generator,'
|
|
.I
|
|
ACM Letters on Programming Languages and Systems
|
|
.BR 1 ,
|
|
3 (Sep. 1992), 213-226.
|
|
.br
|
|
.SH BUGS
|
|
Mail bug reports along with the shortest input
|
|
that exposes them to drh@cs.princeton.edu.
|