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more optimizations for some break/continue cases

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This commit is contained in:
Mihai Bazon
2012-10-18 15:14:57 +03:00
parent 6aa56f92fe
commit afb7faa6fa
5 changed files with 216 additions and 9 deletions
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45
lib/compress.js
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@@ -186,6 +186,14 @@ merge(Compressor.prototype, {
return false;
};
function loop_body(x) {
if (x instanceof AST_Switch) return x;
if (x instanceof AST_For || x instanceof AST_ForIn || x instanceof AST_DWLoop) {
return (x.body instanceof AST_BlockStatement ? x.body : x);
}
return x;
};
function tighten_body(statements, compressor) {
var CHANGED;
do {
@@ -303,8 +311,13 @@ merge(Compressor.prototype, {
}
var ab = aborts(stat.body);
var lct = ab instanceof AST_LoopControl ? compressor.loopcontrol_target(ab.label) : null;
if (ab && ((ab instanceof AST_Return && !ab.value && in_lambda)
|| (ab instanceof AST_Continue && self === compressor.loopcontrol_target(ab.label)))) {
|| (ab instanceof AST_Continue && self === loop_body(lct))
|| (ab instanceof AST_Break && lct instanceof AST_BlockStatement && self === lct))) {
if (ab.label) {
remove(ab.label.thedef.references, ab.label);
}
CHANGED = true;
var body = as_statement_array(stat.body).slice(0, -1);
stat = stat.clone();
@@ -320,8 +333,13 @@ merge(Compressor.prototype, {
}
var ab = aborts(stat.alternative);
var lct = ab instanceof AST_LoopControl ? compressor.loopcontrol_target(ab.label) : null;
if (ab && ((ab instanceof AST_Return && !ab.value && in_lambda)
|| (ab instanceof AST_Continue && self === compressor.loopcontrol_target(ab.label)))) {
|| (ab instanceof AST_Continue && self === loop_body(lct))
|| (ab instanceof AST_Break && lct instanceof AST_BlockStatement && self === lct))) {
if (ab.label) {
remove(ab.label.thedef.references, ab.label);
}
CHANGED = true;
stat = stat.clone();
stat.body = make_node(AST_BlockStatement, stat.body, {
@@ -347,11 +365,26 @@ merge(Compressor.prototype, {
function eliminate_dead_code(statements, compressor) {
var has_quit = false;
var orig = statements.length;
var self = compressor.self();
statements = statements.reduce(function(a, stat){
if (has_quit) {
extract_declarations_from_unreachable_code(compressor, stat, a);
} else {
a.push(stat);
if (stat instanceof AST_LoopControl) {
var lct = compressor.loopcontrol_target(stat.label);
if ((stat instanceof AST_Break
&& lct instanceof AST_BlockStatement
&& loop_body(lct) === self) || (stat instanceof AST_Continue
&& loop_body(lct) === self)) {
if (stat.label) {
remove(stat.label.thedef.references, stat.label);
}
} else {
a.push(stat);
}
} else {
a.push(stat);
}
if (aborts(stat)) has_quit = true;
}
return a;
@@ -795,6 +828,10 @@ merge(Compressor.prototype, {
});
OPT(AST_LabeledStatement, function(self, compressor){
if (self.body instanceof AST_Break
&& compressor.loopcontrol_target(self.body.label) === self.body) {
return make_node(AST_EmptyStatement, self);
}
return self.label.references.length == 0 ? self.body : self;
});
@@ -1227,7 +1264,7 @@ merge(Compressor.prototype, {
var last_branch = self.body[self.body.length - 1];
if (last_branch) {
var stat = last_branch.body[last_branch.body.length - 1]; // last statement
if (stat instanceof AST_Break && compressor.loopcontrol_target(stat.label) === self)
if (stat instanceof AST_Break && loop_body(compressor.loopcontrol_target(stat.label)) === self)
last_branch.body.pop();
}
return self;