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optimise do{...}while(false) (#1785)

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- better heuristics to avoid issues like #1532
- fix `TreeWalker.loopcontrol_target()`
  - `continue` cannot refer to `switch` blocks
This commit is contained in:
Alex Lam S.L
2017-04-04 23:48:22 +08:00
committed by GitHub
parent 4b90dc1fdb
commit 9b6bc67c33
3 changed files with 49 additions and 19 deletions
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10
lib/ast.js
View File

@@ -1035,16 +1035,16 @@ TreeWalker.prototype = {
self = p;
}
},
loopcontrol_target: function(label) {
loopcontrol_target: function(node) {
var stack = this.stack;
if (label) for (var i = stack.length; --i >= 0;) {
if (node.label) for (var i = stack.length; --i >= 0;) {
var x = stack[i];
if (x instanceof AST_LabeledStatement && x.label.name == label.name) {
if (x instanceof AST_LabeledStatement && x.label.name == node.label.name)
return x.body;
}
} else for (var i = stack.length; --i >= 0;) {
var x = stack[i];
if (x instanceof AST_Switch || x instanceof AST_IterationStatement)
if (x instanceof AST_IterationStatement
|| node instanceof AST_Break && x instanceof AST_Switch)
return x;
}
}

32
lib/compress.js
View File

@@ -893,7 +893,7 @@ merge(Compressor.prototype, {
}
var ab = aborts(stat.body);
var lct = ab instanceof AST_LoopControl ? compressor.loopcontrol_target(ab.label) : null;
var lct = ab instanceof AST_LoopControl ? compressor.loopcontrol_target(ab) : null;
if (ab && ((ab instanceof AST_Return && !ab.value && in_lambda)
|| (ab instanceof AST_Continue && self === loop_body(lct))
|| (ab instanceof AST_Break && lct instanceof AST_BlockStatement && self === lct))) {
@@ -915,7 +915,7 @@ merge(Compressor.prototype, {
}
var ab = aborts(stat.alternative);
var lct = ab instanceof AST_LoopControl ? compressor.loopcontrol_target(ab.label) : null;
var lct = ab instanceof AST_LoopControl ? compressor.loopcontrol_target(ab) : null;
if (ab && ((ab instanceof AST_Return && !ab.value && in_lambda)
|| (ab instanceof AST_Continue && self === loop_body(lct))
|| (ab instanceof AST_Break && lct instanceof AST_BlockStatement && self === lct))) {
@@ -964,7 +964,7 @@ merge(Compressor.prototype, {
extract_declarations_from_unreachable_code(compressor, stat, a);
} else {
if (stat instanceof AST_LoopControl) {
var lct = compressor.loopcontrol_target(stat.label);
var lct = compressor.loopcontrol_target(stat);
if ((stat instanceof AST_Break
&& !(lct instanceof AST_IterationStatement)
&& loop_body(lct) === self) || (stat instanceof AST_Continue
@@ -1746,7 +1746,7 @@ merge(Compressor.prototype, {
OPT(AST_LabeledStatement, function(self, compressor){
if (self.body instanceof AST_Break
&& compressor.loopcontrol_target(self.body.label) === self.body) {
&& compressor.loopcontrol_target(self.body) === self.body) {
return make_node(AST_EmptyStatement, self);
}
return self.label.references.length == 0 ? self.body : self;
@@ -2314,13 +2314,21 @@ merge(Compressor.prototype, {
return make_node(AST_For, self, {
body: self.body
});
} else if (compressor.option("dead_code") && self instanceof AST_While) {
}
if (compressor.option("dead_code") && self instanceof AST_While) {
var a = [];
extract_declarations_from_unreachable_code(compressor, self.body, a);
return make_node(AST_BlockStatement, self, { body: a });
} else {
cond = make_node_from_constant(cond, self.condition).transform(compressor);
self.condition = best_of_expression(cond, self.condition);
}
if (self instanceof AST_Do) {
var has_loop_control = false;
var tw = new TreeWalker(function(node) {
if (node instanceof AST_Scope || has_loop_control) return true;
if (node instanceof AST_LoopControl && tw.loopcontrol_target(node) === self)
return has_loop_control = true;
});
self.walk(tw);
if (!has_loop_control) return self.body;
}
}
if (self instanceof AST_While) {
@@ -2346,7 +2354,7 @@ merge(Compressor.prototype, {
var first = self.body instanceof AST_BlockStatement ? self.body.body[0] : self.body;
if (first instanceof AST_If) {
if (first.body instanceof AST_Break
&& compressor.loopcontrol_target(first.body.label) === compressor.self()) {
&& compressor.loopcontrol_target(first.body) === compressor.self()) {
if (self.condition) {
self.condition = make_node(AST_Binary, self.condition, {
left: self.condition,
@@ -2359,7 +2367,7 @@ merge(Compressor.prototype, {
drop_it(first.alternative);
}
else if (first.alternative instanceof AST_Break
&& compressor.loopcontrol_target(first.alternative.label) === compressor.self()) {
&& compressor.loopcontrol_target(first.alternative) === compressor.self()) {
if (self.condition) {
self.condition = make_node(AST_Binary, self.condition, {
left: self.condition,
@@ -2590,7 +2598,7 @@ merge(Compressor.prototype, {
self.body = body;
while (branch = body[body.length - 1]) {
var stat = branch.body[branch.body.length - 1];
if (stat instanceof AST_Break && compressor.loopcontrol_target(stat.label) === self)
if (stat instanceof AST_Break && compressor.loopcontrol_target(stat) === self)
branch.body.pop();
if (branch.body.length || branch instanceof AST_Case
&& (default_branch || branch.expression.has_side_effects(compressor))) break;
@@ -2609,7 +2617,7 @@ merge(Compressor.prototype, {
if (has_break
|| node instanceof AST_Lambda
|| node instanceof AST_SimpleStatement) return true;
if (node instanceof AST_Break && tw.loopcontrol_target(node.label) === self)
if (node instanceof AST_Break && tw.loopcontrol_target(node) === self)
has_break = true;
});
self.walk(tw);

26
test/compress/loops.js
View File

@@ -215,8 +215,7 @@ evaluate: {
a();
for(;;)
c();
// rule disabled due to issue_1532
do d(); while (false);
d();
}
}
@@ -458,3 +457,26 @@ issue_1648: {
}
expect_exact: "function f(){for(x();1;);}"
}
do_switch: {
options = {
evaluate: true,
loops: true,
}
input: {
do {
switch (a) {
case b:
continue;
}
} while (false);
}
expect: {
do {
switch (a) {
case b:
continue;
}
} while (false);
}
}