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Optimize if_return for single if/return cases.

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Fixes #1089
This commit is contained in:
kzc
2016-05-22 11:35:41 -04:00
committed by Richard van Velzen
parent bc49dfd27a
commit 1e390269d4
2 changed files with 221 additions and 1 deletions
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15
lib/compress.js
View File

@@ -535,6 +535,7 @@ merge(Compressor.prototype, {
function handle_if_return(statements, compressor) {
var self = compressor.self();
var multiple_if_returns = has_multiple_if_returns(statements);
var in_lambda = self instanceof AST_Lambda;
var ret = [];
loop: for (var i = statements.length; --i >= 0;) {
@@ -572,7 +573,8 @@ merge(Compressor.prototype, {
}
//---
// if (foo()) return x; [ return ; ] ==> return foo() ? x : undefined;
if ((ret.length == 0 || ret[0] instanceof AST_Return) && stat.body.value && !stat.alternative && in_lambda) {
if (multiple_if_returns && (ret.length == 0 || ret[0] instanceof AST_Return)
&& stat.body.value && !stat.alternative && in_lambda) {
CHANGED = true;
stat = stat.clone();
stat.alternative = ret[0] || make_node(AST_Return, stat, {
@@ -664,6 +666,17 @@ merge(Compressor.prototype, {
}
}
return ret;
function has_multiple_if_returns(statements) {
var n = 0;
for (var i = statements.length; --i >= 0;) {
var stat = statements[i];
if (stat instanceof AST_If && stat.body instanceof AST_Return) {
if (++n > 1) return true;
}
}
return false;
}
};
function eliminate_dead_code(statements, compressor) {

207
test/compress/if_return.js Normal file
View File

@@ -0,0 +1,207 @@
if_return_1: {
options = {
if_return : true,
sequences : true,
conditionals : true,
comparisons : true,
evaluate : true,
booleans : true,
unused : true,
side_effects : true,
dead_code : true,
}
input: {
function f(x) {
if (x) {
return true;
}
}
}
expect: {
function f(x){if(x)return!0}
}
}
if_return_2: {
options = {
if_return : true,
sequences : true,
conditionals : true,
comparisons : true,
evaluate : true,
booleans : true,
unused : true,
side_effects : true,
dead_code : true,
}
input: {
function f(x, y) {
if (x)
return 3;
if (y)
return c();
}
}
expect: {
function f(x,y){return x?3:y?c():void 0}
}
}
if_return_3: {
options = {
if_return : true,
sequences : true,
conditionals : true,
comparisons : true,
evaluate : true,
booleans : true,
unused : true,
side_effects : true,
dead_code : true,
}
input: {
function f(x) {
a();
if (x) {
b();
return false;
}
}
}
expect: {
function f(x){if(a(),x)return b(),!1}
}
}
if_return_4: {
options = {
if_return : true,
sequences : true,
conditionals : true,
comparisons : true,
evaluate : true,
booleans : true,
unused : true,
side_effects : true,
dead_code : true,
}
input: {
function f(x, y) {
a();
if (x) return 3;
b();
if (y) return c();
}
}
expect: {
function f(x,y){return a(),x?3:(b(),y?c():void 0)}
}
}
if_return_5: {
options = {
if_return : true,
sequences : true,
conditionals : true,
comparisons : true,
evaluate : true,
booleans : true,
unused : true,
side_effects : true,
dead_code : true,
}
input: {
function f() {
if (x)
return;
return 7;
if (y)
return j;
}
}
expect: {
function f(){if(!x)return 7}
}
}
if_return_6: {
options = {
if_return : true,
sequences : true,
conditionals : true,
comparisons : true,
evaluate : true,
booleans : true,
unused : true,
side_effects : true,
dead_code : true,
}
input: {
function f(x) {
return x ? true : void 0;
return y;
}
}
expect: {
// suboptimal
function f(x){return!!x||void 0}
}
}
if_return_7: {
options = {
if_return : true,
sequences : true,
conditionals : true,
comparisons : true,
evaluate : true,
booleans : true,
unused : true,
side_effects : true,
dead_code : true,
}
input: {
function f(x) {
if (x) {
return true;
}
foo();
bar();
}
}
expect: {
// suboptimal
function f(x){return!!x||(foo(),void bar())}
}
}
issue_1089: {
options = {
if_return : true,
sequences : true,
conditionals : true,
comparisons : true,
evaluate : true,
booleans : true,
unused : true,
side_effects : true,
dead_code : true,
}
input: {
function x() {
var f = document.getElementById("fname");
if (f.files[0].size > 12345) {
alert("alert");
f.focus();
return false;
}
}
}
expect: {
function x() {
var f = document.getElementById("fname");
if (f.files[0].size > 12345)
return alert("alert"), f.focus(), !1;
}
}
}