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compress chained compound assignments (#2850)

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This commit is contained in:
Alex Lam S.L
2018-01-29 15:13:25 +08:00
committed by GitHub
parent 4eb4cb656c
commit 6fa3fbeae8
3 changed files with 125 additions and 43 deletions
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63
lib/compress.js
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@@ -320,6 +320,7 @@ merge(Compressor.prototype, {
function reset_def(compressor, def) {
def.assignments = 0;
def.chained = false;
def.direct_access = false;
def.escaped = false;
if (def.scope.uses_eval || def.scope.uses_with) {
@@ -485,19 +486,27 @@ merge(Compressor.prototype, {
});
def(AST_Assign, function(tw) {
var node = this;
if (node.operator != "=" || !(node.left instanceof AST_SymbolRef)) return;
if (!(node.left instanceof AST_SymbolRef)) return;
var d = node.left.definition();
if (safe_to_assign(tw, d, node.right)) {
d.references.push(node.left);
d.assignments++;
d.fixed = function() {
return node.right;
};
mark(tw, d, false);
node.right.walk(tw);
mark(tw, d, true);
return true;
}
var fixed = d.fixed;
if (!fixed && node.operator != "=") return;
if (!safe_to_assign(tw, d, node.right)) return;
d.references.push(node.left);
d.assignments++;
if (node.operator != "=") d.chained = true;
d.fixed = node.operator == "=" ? function() {
return node.right;
} : function() {
return make_node(AST_Binary, node, {
operator: node.operator.slice(0, -1),
left: fixed instanceof AST_Node ? fixed : fixed(),
right: node.right
});
};
mark(tw, d, false);
node.right.walk(tw);
mark(tw, d, true);
return true;
});
def(AST_Binary, function(tw) {
if (!lazy_op(this.operator)) return;
@@ -672,6 +681,32 @@ merge(Compressor.prototype, {
if (this.bfinally) this.bfinally.walk(tw);
return true;
});
def(AST_Unary, function(tw, descend) {
var node = this;
if (node.operator != "++" && node.operator != "--") return;
if (!(node.expression instanceof AST_SymbolRef)) return;
var d = node.expression.definition();
var fixed = d.fixed;
if (!fixed) return;
if (!safe_to_assign(tw, d, true)) return;
d.references.push(node.expression);
d.assignments++;
d.chained = true;
d.fixed = function() {
return make_node(AST_Binary, node, {
operator: node.operator.slice(0, -1),
left: make_node(AST_UnaryPrefix, node, {
operator: "+",
expression: fixed instanceof AST_Node ? fixed : fixed()
}),
right: make_node(AST_Number, node, {
value: 1
})
});
};
mark(tw, d, true);
return true;
});
def(AST_VarDef, function(tw, descend) {
var node = this;
var d = node.name.definition();
@@ -2946,7 +2981,7 @@ merge(Compressor.prototype, {
if (def.value.has_side_effects(compressor)) {
def.value.walk(tw);
}
if (def.name.fixed_value() === def.value) {
if (!node_def.chained && def.name.fixed_value() === def.value) {
fixed_ids[node_def.id] = def;
}
}
@@ -3164,7 +3199,7 @@ merge(Compressor.prototype, {
&& self.variables.get(sym.name) === (node_def = sym.definition())) {
if (node instanceof AST_Assign) {
node.right.walk(tw);
if (node.left.fixed_value() === node.right) {
if (!node_def.chained && node.left.fixed_value() === node.right) {
fixed_ids[node_def.id] = node;
}
}