pegjs/spec/compiler/passes/generate-bytecode.spec.js
David Majda fe1ca481ab Code generator rewrite
This is a complete rewrite of the PEG.js code generator. Its goals are:

  1. Allow optimizing the generated parser code for code size as well as
     for parsing speed.

  2. Prepare ground for future optimizations and big features (like
     incremental parsing).

  2. Replace the old template-based code-generation system with
     something more lightweight and flexible.

  4. General code cleanup (structure, style, variable names, ...).

New Architecture
----------------

The new code generator consists of two steps:

  * Bytecode generator -- produces bytecode for an abstract virtual
    machine

  * JavaScript generator -- produces JavaScript code based on the
    bytecode

The abstract virtual machine is stack-based. Originally I wanted to make
it register-based, but it turned out that all the code related to it
would be more complex and the bytecode itself would be longer (because
of explicit register specifications in instructions). The only downsides
of the stack-based approach seem to be few small inefficiencies (see
e.g. the |NIP| instruction), which seem to be insignificant.

The new generator allows optimizing for parsing speed or code size (you
can choose using the |optimize| option of the |PEG.buildParser| method
or the --optimize/-o option on the command-line).

When optimizing for size, the JavaScript generator emits the bytecode
together with its constant table and a generic bytecode interpreter.
Because the interpreter is small and the bytecode and constant table
grow only slowly with size of the grammar, the resulting parser is also
small.

When optimizing for speed, the JavaScript generator just compiles the
bytecode into JavaScript. The generated code is relatively efficient, so
the resulting parser is fast.

Internal Identifiers
--------------------

As a small bonus, all internal identifiers visible to user code in the
initializer, actions and predicates are prefixed by |peg$|. This lowers
the chance that identifiers in user code will conflict with the ones
from PEG.js. It also makes using any internals in user code ugly, which
is a good thing. This solves GH-92.

Performance
-----------

The new code generator improved parsing speed and parser code size
significantly. The generated parsers are now:

  * 39% faster when optimizing for speed

  * 69% smaller when optimizing for size (without minification)

  * 31% smaller when optimizing for size (with minification)

(Parsing speed was measured using the |benchmark/run| script. Code size
was measured by generating parsers for examples in the |examples|
directory and adding up the file sizes. Minification was done by |uglify
--ascii| in version 1.3.4.)

Final Note
----------

This is just a beginning! The new code generator lays a foundation upon
which many optimizations and improvements can (and will) be made.

Stay tuned :-)
2013-01-01 16:38:09 +01:00

675 lines
22 KiB
JavaScript

describe("compiler pass |generateBytecode|", function() {
var pass = PEG.compiler.passes.generateBytecode;
function bytecodeDetails(bytecode) {
return {
rules: [{ bytecode: bytecode }]
};
}
function constsDetails(consts) { return { consts: consts }; }
describe("for grammar", function() {
it("generates correct bytecode", function() {
expect(pass).toChangeAST([
'a = "a"',
'b = "b"',
'c = "c"'
].join("\n"), {
rules: [
{ bytecode: [15, 0, 2, 2, 19, 0, 20, 1] },
{ bytecode: [15, 2, 2, 2, 19, 2, 20, 3] },
{ bytecode: [15, 4, 2, 2, 19, 4, 20, 5] }
]
});
});
it("defines correct constants", function() {
expect(pass).toChangeAST([
'a = "a"',
'b = "b"',
'c = "c"'
].join("\n"), constsDetails([
'"a"',
'"\\"a\\""',
'"b"',
'"\\"b\\""',
'"c"',
'"\\"c\\""'
]));
});
});
describe("for rule", function() {
it("generates correct bytecode", function() {
expect(pass).toChangeAST('start = "a"', bytecodeDetails([
15, 0, 2, 2, 19, 0, 20, 1 // <expression>
]));
});
});
describe("for named", function() {
var grammar = 'start "start" = "a"';
it("generates correct bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
25, // SILENT_FAILS_ON
15, 1, 2, 2, 19, 1, 20, 2, // <expression>
26, // SILENT_FAILS_OFF
11, 2, 0, // IF_ERROR
20, 0 // FAIL
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(
grammar,
constsDetails(['"start"', '"a"', '"\\"a\\""'])
);
});
});
describe("for choice", function() {
it("generates correct bytecode", function() {
expect(pass).toChangeAST('start = "a" / "b" / "c"', bytecodeDetails([
15, 0, 2, 2, 19, 0, 20, 1, // <alternatives[0]>
11, 21, 0, // IF_ERROR
2, // * POP
15, 2, 2, 2, 19, 2, 20, 3, // <alternatives[1]>
11, 9, 0, // IF_ERROR
2, // * POP
15, 4, 2, 2, 19, 4, 20, 5 // <alternatives[2]>
]));
});
});
describe("for action", function() {
describe("without labels", function() {
var grammar = 'start = { code }';
it("generates correct bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
1, // PUSH_CURR_POS
0, 0, // PUSH
12, 6, 0, // IF_NOT_ERROR
21, 1, // * REPORT_SAVED_POS
23, 1, 1, 0, // CALL
11, 1, 1, // IF_ERROR
6, // * NIP_CURR_POS
5 // * NIP
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(
grammar,
constsDetails(['[]', 'function() { code }'])
);
});
});
describe("with one label", function() {
var grammar = 'start = a:"a" { code }';
it("generates correct bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
1, // PUSH_CURR_POS
15, 0, 2, 2, 19, 0, 20, 1, // <expression>
12, 7, 0, // IF_NOT_ERROR
21, 1, // * REPORT_SAVED_POS
23, 2, 1, 1, 0, // CALL
11, 1, 1, // IF_ERROR
6, // * NIP_CURR_POS
5 // * NIP
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(
grammar,
constsDetails(['"a"', '"\\"a\\""', 'function(a) { code }'])
);
});
});
describe("with multiple labels", function() {
var grammar = 'start = a:"a" b:"b" c:"c" { code }';
it("generates correct bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
1, // PUSH_CURR_POS
15, 1, 2, 2, 19, 1, 20, 2, // <elements[0]>
12, 46, 4, // IF_NOT_ERROR
15, 3, 2, 2, 19, 3, 20, 4, // * <elements[1]>
12, 30, 5, // IF_NOT_ERROR
15, 5, 2, 2, 19, 5, 20, 6, // * <elements[2]>
12, 14, 5, // IF_NOT_ERROR
21, 3, // * REPORT_SAVED_POS
23, 7, 3, 3, 2, 1, 0, // CALL
11, 1, 1, // IF_ERROR
6, // * NIP_CURR_POS
5, // * NIP
4, 3, // * POP_N
3, // POP_CURR_POS
0, 0, // PUSH
4, 2, // * POP_N
3, // POP_CURR_POS
0, 0, // PUSH
2, // * POP
3, // POP_CURR_POS
0, 0 // PUSH
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(grammar, constsDetails([
'null',
'"a"',
'"\\"a\\""',
'"b"',
'"\\"b\\""',
'"c"',
'"\\"c\\""',
'function(a, b, c) { code }'
]));
});
});
});
describe("for sequence", function() {
describe("empty", function() {
var grammar = 'start = ';
it("generates correct bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
0, 0 // PUSH
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(grammar, constsDetails(['[]']));
});
});
describe("non-empty", function() {
var grammar = 'start = "a" "b" "c"';
it("generates correct bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
1, // PUSH_CURR_POS
15, 1, 2, 2, 19, 1, 20, 2, // <elements[0]>
12, 35, 4, // IF_NOT_ERROR
15, 3, 2, 2, 19, 3, 20, 4, // * <elements[1]>
12, 19, 5, // IF_NOT_ERROR
15, 5, 2, 2, 19, 5, 20, 6, // * <elements[2]>
12, 3, 5, // IF_NOT_ERROR
8, 3, // * WRAP
5, // NIP
4, 3, // * POP_N
3, // POP_CURR_POS
0, 0, // PUSH
4, 2, // * POP_N
3, // POP_CURR_POS
0, 0, // PUSH
2, // * POP
3, // POP_CURR_POS
0, 0 // PUSH
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(
grammar,
constsDetails([
'null',
'"a"',
'"\\"a\\""',
'"b"',
'"\\"b\\""',
'"c"',
'"\\"c\\""'
])
);
});
});
});
describe("for labeled", function() {
it("generates correct bytecode", function() {
expect(pass).toChangeAST('start = a:"a"', bytecodeDetails([
15, 0, 2, 2, 19, 0, 20, 1 // <expression>
]));
});
});
describe("for text", function() {
it("generates correct bytecode", function() {
expect(pass).toChangeAST('start = $"a"', bytecodeDetails([
1, // PUSH_CURR_POS
15, 0, 2, 2, 19, 0, 20, 1, // <expression>
12, 1, 0, // IF_NOT_ERROR
9, // * TEXT
5 // NIP
]));
});
});
describe("for simple and", function() {
var grammar = 'start = &"a"';
it("generates correct bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
1, // PUSH_CURR_POS
25, // SILENT_FAILS_ON
15, 2, 2, 2, 19, 2, 20, 3, // <expression>
26, // SILENT_FAILS_OFF
12, 4, 4, // IF_NOT_ERROR
2, // * POP
3, // POP_CURR_POS
0, 0, // PUSH
2, // * POP
2, // POP
0, 1 // PUSH
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(
grammar,
constsDetails(['""', 'null', '"a"', '"\\"a\\""'])
);
});
});
describe("for simple not", function() {
var grammar = 'start = !"a"';
it("generates correct bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
1, // PUSH_CURR_POS
25, // SILENT_FAILS_ON
15, 2, 2, 2, 19, 2, 20, 3, // <expression>
26, // SILENT_FAILS_OFF
11, 4, 4, // IF_ERROR
2, // * POP
2, // POP
0, 0, // PUSH
2, // * POP
3, // POP_CURR_POS
0, 1 // PUSH
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(
grammar,
constsDetails(['""', 'null', '"a"', '"\\"a\\""'])
);
});
});
describe("for semantic and", function() {
describe("without labels", function() {
var grammar = 'start = &{ code }';
it("generates correct bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
22, // REPORT_CURR_POS
23, 0, 0, 0, // CALL
10, 3, 3, // IF
2, // * POP
0, 1, // PUSH
2, // * POP
0, 2 // PUSH
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(
grammar,
constsDetails(['function() { code }', '""', 'null'])
);
});
});
describe("with labels", function() {
var grammar = 'start = a:"a" b:"b" c:"c" &{ code }';
it("generates correct bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
1, // PUSH_CURR_POS
15, 1, 2, 2, 19, 1, 20, 2, // <elements[0]>
12, 60, 4, // IF_NOT_ERROR
15, 3, 2, 2, 19, 3, 20, 4, // * <elements[1]>
12, 44, 5, // IF_NOT_ERROR
15, 5, 2, 2, 19, 5, 20, 6, // * <elements[2]>
12, 28, 5, // IF_NOT_ERROR
22, // * REPORT_CURR_POS
23, 7, 0, 3, 2, 1, 0, // CALL
10, 3, 3, // IF
2, // * POP
0, 8, // PUSH
2, // * POP
0, 0, // PUSH
12, 3, 5, // IF_NOT_ERROR
8, 4, // * WRAP
5, // NIP
4, 4, // * POP_N
3, // POP_CURR_POS
0, 0, // PUSH
4, 3, // * POP_N
3, // POP_CURR_POS
0, 0, // PUSH
4, 2, // * POP_N
3, // POP_CURR_POS
0, 0, // PUSH
2, // * POP
3, // POP_CURR_POS
0, 0 // PUSH
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(grammar, constsDetails([
'null',
'"a"',
'"\\"a\\""',
'"b"',
'"\\"b\\""',
'"c"',
'"\\"c\\""',
'function(a, b, c) { code }',
'""'
]));
});
});
});
describe("for semantic not", function() {
describe("without labels", function() {
var grammar = 'start = !{ code }';
it("generates correct bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
22, // REPORT_CURR_POS
23, 0, 0, 0, // CALL_PREDICATE
10, 3, 3, // IF
2, // * POP
0, 2, // PUSH
2, // * POP
0, 1 // PUSH
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(
grammar,
constsDetails(['function() { code }', '""', 'null'])
);
});
});
describe("with labels", function() {
var grammar = 'start = a:"a" b:"b" c:"c" !{ code }';
it("generates correct bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
1, // PUSH_CURR_POS
15, 1, 2, 2, 19, 1, 20, 2, // <elements[0]>
12, 60, 4, // IF_NOT_ERROR
15, 3, 2, 2, 19, 3, 20, 4, // * <elements[1]>
12, 44, 5, // IF_NOT_ERROR
15, 5, 2, 2, 19, 5, 20, 6, // * <elements[2]>
12, 28, 5, // IF_NOT_ERROR
22, // * REPORT_CURR_POS
23, 7, 0, 3, 2, 1, 0, // CALL
10, 3, 3, // IF
2, // * POP
0, 0, // PUSH
2, // * POP
0, 8, // PUSH
12, 3, 5, // IF_NOT_ERROR
8, 4, // * WRAP
5, // NIP
4, 4, // * POP_N
3, // POP_CURR_POS
0, 0, // PUSH
4, 3, // * POP_N
3, // POP_CURR_POS
0, 0, // PUSH
4, 2, // * POP_N
3, // POP_CURR_POS
0, 0, // PUSH
2, // * POP
3, // POP_CURR_POS
0, 0 // PUSH
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(grammar, constsDetails([
'null',
'"a"',
'"\\"a\\""',
'"b"',
'"\\"b\\""',
'"c"',
'"\\"c\\""',
'function(a, b, c) { code }',
'""'
]));
});
});
});
describe("for optional", function() {
var grammar = 'start = "a"?';
it("generates correct bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
15, 1, 2, 2, 19, 1, 20, 2, // <expression>
11, 3, 0, // IF_ERROR
2, // * POP
0, 0 // PUSH
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(
grammar,
constsDetails(['""', '"a"', '"\\"a\\""'])
);
});
});
describe("for zero or more", function() {
var grammar = 'start = "a"*';
it("generates correct bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
0, 0, // PUSH
15, 1, 2, 2, 19, 1, 20, 2, // <expression>
13, 9, // WHILE_NOT_ERROR
7, // * APPEND
15, 1, 2, 2, 19, 1, 20, 2, // <expression>
2 // POP
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(
grammar,
constsDetails(['[]', '"a"', '"\\"a\\""'])
);
});
});
describe("for one or more", function() {
var grammar = 'start = "a"+';
it("generates correct bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
0, 0, // PUSH
15, 2, 2, 2, 19, 2, 20, 3, // <expression>
12, 12, 4, // IF_NOT_ERROR
13, 9, // * WHILE_NOT_ERROR
7, // * APPEND
15, 2, 2, 2, 19, 2, 20, 3, // <expression>
2, // POP
2, // * POP
2, // POP
0, 1 // PUSH
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(
grammar,
constsDetails(['[]', 'null', '"a"', '"\\"a\\""'])
);
});
});
describe("for rule reference", function() {
it("generates correct bytecode", function() {
expect(pass).toChangeAST([
'start = other',
'other = "other"'
].join("\n"), {
rules: [
{
bytecode: [24, 1] // RULE
},
{ }
]
});
});
});
describe("for literal", function() {
describe("empty", function() {
var grammar = 'start = ""';
it("generates correct bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
0, 0 // PUSH
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(grammar, constsDetails(['""']));
});
});
describe("non-empty case-sensitive", function() {
var grammar = 'start = "a"';
it("generates correct bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
15, 0, 2, 2, // MATCH_STRING
19, 0, // * ACCEPT_STRING
20, 1 // * FAIL
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(grammar, constsDetails(['"a"', '"\\"a\\""']));
});
});
describe("non-empty case-insensitive", function() {
var grammar = 'start = "A"i';
it("generates correct bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
16, 0, 2, 2, // MATCH_STRING_IC
18, 1, // * ACCEPT_N
20, 1 // * FAIL
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(grammar, constsDetails(['"a"', '"\\"A\\""']));
});
});
});
describe("for class", function() {
it("generates correct bytecode", function() {
expect(pass).toChangeAST('start = [a]', bytecodeDetails([
17, 0, 2, 2, // MATCH_REGEXP
18, 1, // * ACCEPT_N
20, 1 // * FAIL
]));
});
describe("non-empty non-inverted case-sensitive", function() {
it("defines correct constants", function() {
expect(pass).toChangeAST(
'start = [a]',
constsDetails(['/^[a]/', '"[a]"'])
);
});
});
describe("non-empty inverted case-sensitive", function() {
it("defines correct constants", function() {
expect(pass).toChangeAST(
'start = [^a]',
constsDetails(['/^[^a]/', '"[^a]"'])
);
});
});
describe("non-empty non-inverted case-insensitive", function() {
it("defines correct constants", function() {
expect(pass).toChangeAST(
'start = [a]i',
constsDetails(['/^[a]/i', '"[a]i"'])
);
});
});
describe("non-empty complex", function() {
it("defines correct constants", function() {
expect(pass).toChangeAST(
'start = [ab-def-hij-l]',
constsDetails(['/^[ab-def-hij-l]/', '"[ab-def-hij-l]"'])
);
});
});
describe("empty non-inverted", function() {
it("defines correct constants", function() {
expect(pass).toChangeAST(
'start = []',
constsDetails(['/^(?!)/', '"[]"'])
);
});
});
describe("empty inverted", function() {
it("defines correct constants", function() {
expect(pass).toChangeAST(
'start = [^]',
constsDetails(['/^[\\S\\s]/', '"[^]"'])
);
});
});
});
describe("for any", function() {
var grammar = 'start = .';
it("generates bytecode", function() {
expect(pass).toChangeAST(grammar, bytecodeDetails([
14, 2, 2, // MATCH_ANY
18, 1, // * ACCEPT_N
20, 0 // * FAIL
]));
});
it("defines correct constants", function() {
expect(pass).toChangeAST(grammar, constsDetails(['"any character"']));
});
});
});