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improve transversal efficiency in collapse_vars (#2611)

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fixes #2603
This commit is contained in:
Alex Lam S.L
2017-12-18 03:00:05 +08:00
committed by GitHub
parent 5de369fa67
commit b29fc8b27c
2 changed files with 62 additions and 21 deletions
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61
lib/compress.js
View File

@@ -905,10 +905,18 @@ merge(Compressor.prototype, {
if (abort) return node;
// Scan case expressions first in a switch statement
if (node instanceof AST_Switch) {
if (!hit) {
if (node !== hit_stack[hit_index]) return node;
hit_index++;
}
node.expression = node.expression.transform(scanner);
for (var i = 0, len = node.body.length; !abort && i < len; i++) {
var branch = node.body[i];
if (branch instanceof AST_Case) {
if (!hit) {
if (branch !== hit_stack[hit_index]) continue;
hit_index++;
}
branch.expression = branch.expression.transform(scanner);
if (side_effects || !replace_all) break;
}
@@ -918,13 +926,13 @@ merge(Compressor.prototype, {
}
// Skip nodes before `candidate` as quickly as possible
if (!hit) {
if (node === candidate) {
hit = true;
stop_after = find_stop(node, 0);
if (stop_after === node) abort = true;
return node;
}
return;
if (node !== hit_stack[hit_index]) return node;
hit_index++;
if (hit_index < hit_stack.length) return;
hit = true;
stop_after = find_stop(node, 0);
if (stop_after === node) abort = true;
return node;
}
// Stop immediately if these node types are encountered
var parent = scanner.parent();
@@ -1013,11 +1021,11 @@ merge(Compressor.prototype, {
if (abort) return node;
// Skip nodes before `candidate` as quickly as possible
if (!hit) {
if (node === candidate) {
hit = true;
return node;
}
return;
if (node !== hit_stack[hit_index]) return node;
hit_index++;
if (hit_index < hit_stack.length) return;
hit = true;
return node;
}
// Replace variable when found
if (node instanceof AST_SymbolRef
@@ -1038,9 +1046,12 @@ merge(Compressor.prototype, {
// var a = x(), b = undefined;
if (stat_index == 0 && compressor.option("unused")) extract_args();
// Find collapsible assignments
var hit_stack = [];
extract_candidates(statements[stat_index]);
while (candidates.length > 0) {
var candidate = candidates.pop();
hit_stack = candidates.pop();
var hit_index = 0;
var candidate = hit_stack[hit_stack.length - 1];
var value_def = null;
var stop_after = null;
var lhs = get_lhs(candidate);
@@ -1074,6 +1085,7 @@ merge(Compressor.prototype, {
if (abort && def.references.length - def.replaced > replaced) replaced = false;
else {
abort = false;
hit_index = 0;
hit = funarg;
for (var i = stat_index; !abort && i < statements.length; i++) {
statements[i].transform(multi_replacer);
@@ -1124,18 +1136,24 @@ merge(Compressor.prototype, {
});
arg.walk(tw);
}
if (arg) candidates.unshift(make_node(AST_VarDef, sym, {
if (arg) candidates.unshift([ make_node(AST_VarDef, sym, {
name: sym,
value: arg
}));
}) ]);
}
}
}
function extract_candidates(expr) {
if (expr instanceof AST_Assign && !expr.left.has_side_effects(compressor)
|| expr instanceof AST_Unary && (expr.operator == "++" || expr.operator == "--")) {
candidates.push(expr);
hit_stack.push(expr);
if (expr instanceof AST_Assign) {
if (!expr.left.has_side_effects(compressor)) {
candidates.push(hit_stack.slice());
}
} else if (expr instanceof AST_Unary) {
if (expr.operator == "++" || expr.operator == "--") {
candidates.push(hit_stack.slice());
}
} else if (expr instanceof AST_Call) {
extract_candidates(expr.expression);
expr.args.forEach(extract_candidates);
@@ -1146,9 +1164,7 @@ merge(Compressor.prototype, {
extract_candidates(expr.consequent);
extract_candidates(expr.alternative);
} else if (expr instanceof AST_Definitions) {
expr.definitions.forEach(function(var_def) {
if (var_def.value) candidates.push(var_def);
});
expr.definitions.forEach(extract_candidates);
} else if (expr instanceof AST_Exit) {
if (expr.value) extract_candidates(expr.value);
} else if (expr instanceof AST_For) {
@@ -1162,7 +1178,10 @@ merge(Compressor.prototype, {
} else if (expr instanceof AST_Switch) {
extract_candidates(expr.expression);
expr.body.forEach(extract_candidates);
} else if (expr instanceof AST_VarDef) {
if (expr.value) candidates.push(hit_stack.slice());
}
hit_stack.pop();
}
function find_stop(node, level) {

22
test/compress/collapse_vars.js
View File

@@ -3990,3 +3990,25 @@ cascade_call: {
}
}
}
replace_all_var: {
options = {
collapse_vars: true,
unused: true,
}
input: {
var a = "PASS";
(function() {
var b = b || c && c[a = "FAIL"], c = a;
})();
console.log(a);
}
expect: {
var a = "PASS";
(function() {
var b = b || c && c[a = "FAIL"], c = a;
})();
console.log(a);
}
expect_stdout: "PASS"
}