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drop local assign-only variable in return (#2587)

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This commit is contained in:
Alex Lam S.L
2017-12-14 02:59:59 +08:00
committed by GitHub
parent ef618332ea
commit 9a137e8613
3 changed files with 113 additions and 5 deletions
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18
lib/compress.js
View File

@@ -4666,6 +4666,24 @@ merge(Compressor.prototype, {
var ASSIGN_OPS = [ '+', '-', '/', '*', '%', '>>', '<<', '>>>', '|', '^', '&' ];
var ASSIGN_OPS_COMMUTATIVE = [ '*', '|', '^', '&' ];
OPT(AST_Assign, function(self, compressor){
if (compressor.option("dead_code")
&& self.left instanceof AST_SymbolRef
&& self.left.definition().scope === compressor.find_parent(AST_Lambda)) {
var level = 0, node, parent = self;
do {
node = parent;
parent = compressor.parent(level++);
if (parent instanceof AST_Exit) {
if (self.operator == "=") return self.right;
return make_node(AST_Binary, self, {
operator: self.operator.slice(0, -1),
left: self.left,
right: self.right
}).optimize(compressor);
}
} while (parent instanceof AST_Binary && parent.right === node
|| parent instanceof AST_Sequence && parent.tail_node() === node);
}
self = self.lift_sequences(compressor);
if (self.operator == "=" && self.left instanceof AST_SymbolRef && self.right instanceof AST_Binary) {
// x = expr1 OP expr2

10
test/compress/collapse_vars.js
View File

@@ -591,7 +591,7 @@ collapse_vars_switch: {
collapse_vars_assignment: {
options = {
collapse_vars:true, sequences:true, properties:true, dead_code:true, conditionals:true,
collapse_vars:true, sequences:true, properties:true, conditionals:true,
comparisons:true, evaluate:true, booleans:true, loops:true, unused:true, hoist_funs:true,
keep_fargs:true, if_return:true, join_vars:true, side_effects:true
}
@@ -639,7 +639,7 @@ collapse_vars_assignment: {
return a = a;
}
function f1(c) {
return 1 - 3 / c
return 1 - 3 / c;
}
function f2(c) {
return log(c = 3 / c - 7);
@@ -664,7 +664,7 @@ collapse_vars_assignment: {
collapse_vars_lvalues: {
options = {
collapse_vars:true, sequences:true, properties:true, dead_code:true, conditionals:true,
collapse_vars:true, sequences:true, properties:true, conditionals:true,
comparisons:true, evaluate:true, booleans:true, loops:true, unused:"keep_assign",
hoist_funs:true, keep_fargs:true, if_return:true, join_vars:true,
side_effects:true
@@ -697,7 +697,7 @@ collapse_vars_lvalues: {
collapse_vars_lvalues_drop_assign: {
options = {
collapse_vars:true, sequences:true, properties:true, dead_code:true, conditionals:true,
collapse_vars:true, sequences:true, properties:true, conditionals:true,
comparisons:true, evaluate:true, booleans:true, loops:true, unused:true, hoist_funs:true,
keep_fargs:true, if_return:true, join_vars:true, side_effects:true, passes:3
}
@@ -729,7 +729,7 @@ collapse_vars_lvalues_drop_assign: {
collapse_vars_misc1: {
options = {
collapse_vars:true, sequences:true, properties:true, dead_code:true, conditionals:true,
collapse_vars:true, sequences:true, properties:true, conditionals:true,
comparisons:true, evaluate:true, booleans:true, loops:true, unused:true, hoist_funs:true,
keep_fargs:true, if_return:true, join_vars:true, side_effects:true,
reduce_funcs: true, reduce_vars:true

90
test/compress/dead-code.js
View File

@@ -417,3 +417,93 @@ global_fns: {
"RangeError",
]
}
collapse_vars_assignment: {
options = {
collapse_vars: true,
dead_code: true,
passes: 2,
unused: true,
}
input: {
function f0(c) {
var a = 3 / c;
return a = a;
}
}
expect: {
function f0(c) {
return 3 / c;
}
}
}
collapse_vars_lvalues_drop_assign: {
options = {
collapse_vars: true,
dead_code: true,
unused: true,
}
input: {
function f0(x) { var i = ++x; return x += i; }
function f1(x) { var a = (x -= 3); return x += a; }
function f2(x) { var z = x, a = ++z; return z += a; }
}
expect: {
function f0(x) { var i = ++x; return x + i; }
function f1(x) { var a = (x -= 3); return x + a; }
function f2(x) { var z = x, a = ++z; return z + a; }
}
}
collapse_vars_misc1: {
options = {
collapse_vars: true,
dead_code: true,
unused: true,
}
input: {
function f10(x) { var a = 5, b = 3; return a += b; }
function f11(x) { var a = 5, b = 3; return a += --b; }
}
expect: {
function f10(x) { return 5 + 3; }
function f11(x) { var b = 3; return 5 + --b; }
}
}
return_assignment: {
options = {
dead_code: true,
unused: true,
}
input: {
function f1(a, b, c) {
return a = x(), b = y(), b = a && (c >>= 5);
}
function f2() {
return e = x();
}
function f3(e) {
return e = x();
}
function f4() {
var e;
return e = x();
}
}
expect: {
function f1(a, b, c) {
return a = x(), y(), a && (c >> 5);
}
function f2() {
return e = x();
}
function f3(e) {
return x();
}
function f4() {
return x();
}
}
}