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enhance join_vars & sequences (#2697)

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- nudge declarations without assignments
  - within `AST_BlockStatement`
  - across `AST_If`
This commit is contained in:
Alex Lam S.L
2018-01-01 00:09:26 +08:00
committed by GitHub
parent da82fa59a7
commit 673b071637
4 changed files with 160 additions and 18 deletions
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92
lib/compress.js
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@@ -884,6 +884,7 @@ merge(Compressor.prototype, {
}
if (compressor.sequences_limit > 0) {
sequencesize(statements, compressor);
sequencesize_2(statements, compressor);
}
if (compressor.option("join_vars")) {
join_consecutive_vars(statements, compressor);
@@ -1537,6 +1538,12 @@ merge(Compressor.prototype, {
});
}
function declarations_only(node) {
return all(node.definitions, function(var_def) {
return !var_def.value;
});
}
function sequencesize(statements, compressor) {
if (statements.length < 2) return;
var seq = [], n = 0;
@@ -1553,6 +1560,9 @@ merge(Compressor.prototype, {
var body = stat.body;
if (seq.length > 0) body = body.drop_side_effect_free(compressor);
if (body) merge_sequence(seq, body);
} else if (stat instanceof AST_Definitions && declarations_only(stat)
|| stat instanceof AST_Defun) {
statements[n++] = stat;
} else {
push_seq();
statements[n++] = stat;
@@ -1560,13 +1570,31 @@ merge(Compressor.prototype, {
}
push_seq();
statements.length = n;
sequencesize_2(statements, compressor);
CHANGED = statements.length != len;
if (n != len) CHANGED = true;
}
function to_simple_statement(block, decls) {
if (!(block instanceof AST_BlockStatement)) return block;
var defs = [];
var stat = null;
for (var i = 0, len = block.body.length; i < len; i++) {
var line = block.body[i];
if (line instanceof AST_Definitions && declarations_only(line)) {
defs.push(line);
} else if (stat) {
return false;
} else {
stat = line;
}
}
[].push.apply(decls, defs);
return stat;
}
function sequencesize_2(statements, compressor) {
function cons_seq(right) {
n--;
CHANGED = true;
var left = prev.body;
return make_sequence(left, [ left, right ]).transform(compressor);
};
@@ -1588,6 +1616,7 @@ merge(Compressor.prototype, {
else {
stat.init = prev.body;
n--;
CHANGED = true;
}
}
}
@@ -1607,6 +1636,22 @@ merge(Compressor.prototype, {
stat.expression = cons_seq(stat.expression);
}
}
if (compressor.option("conditionals") && stat instanceof AST_If) {
var decls = [];
var body = to_simple_statement(stat.body, decls);
var alt = to_simple_statement(stat.alternative, decls);
if (body !== false && alt !== false && decls.length > 0) {
decls.push(make_node(AST_If, stat, {
condition: stat.condition,
body: body || make_node(AST_EmptyStatement, stat.body),
alternative: alt
}));
stat = make_node(AST_BlockStatement, stat, {
body: decls
});
CHANGED = true;
}
}
statements[n++] = stat;
prev = stat instanceof AST_SimpleStatement ? stat : null;
}
@@ -1614,30 +1659,43 @@ merge(Compressor.prototype, {
}
function join_consecutive_vars(statements, compressor) {
var defs;
for (var i = 0, j = -1, len = statements.length; i < len; i++) {
var stat = statements[i];
var prev = statements[j];
if (stat instanceof AST_Definitions && prev && prev.TYPE == stat.TYPE) {
prev.definitions = prev.definitions.concat(stat.definitions);
CHANGED = true;
}
else if (stat instanceof AST_For
&& prev instanceof AST_Var
&& (!stat.init || stat.init.TYPE == prev.TYPE)) {
CHANGED = true;
if (stat.init) {
stat.init.definitions = prev.definitions.concat(stat.init.definitions);
if (stat instanceof AST_Definitions) {
if (prev && prev.TYPE == stat.TYPE) {
prev.definitions = prev.definitions.concat(stat.definitions);
CHANGED = true;
} else if (defs && defs.TYPE == stat.TYPE && declarations_only(stat)) {
defs.definitions = defs.definitions.concat(stat.definitions);
CHANGED = true;
} else {
stat.init = prev;
statements[++j] = stat;
defs = stat;
}
statements[j] = stat;
}
else {
} else if (stat instanceof AST_For) {
if (prev instanceof AST_Var && (!stat.init || stat.init.TYPE == prev.TYPE)) {
if (stat.init) {
prev.definitions = prev.definitions.concat(stat.init.definitions);
}
stat.init = prev;
statements[j] = stat;
CHANGED = true;
} else if (defs && stat.init && defs.TYPE == stat.init.TYPE && declarations_only(stat.init)) {
defs.definitions = defs.definitions.concat(stat.init.definitions);
stat.init = null;
statements[++j] = stat;
CHANGED = true;
} else {
statements[++j] = stat;
}
} else {
statements[++j] = stat;
}
}
statements.length = j + 1;
};
}
}
function extract_declarations_from_unreachable_code(compressor, stat, target) {