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enhance dead_code (#3811)

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This commit is contained in:
Alex Lam S.L
2020-04-22 11:22:45 +01:00
committed by GitHub
parent 306e8e9873
commit 01b13d797c
2 changed files with 101 additions and 34 deletions
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42
lib/compress.js
View File

@@ -1034,6 +1034,16 @@ merge(Compressor.prototype, {
return false;
}
function has_declarations_only(block) {
return all(block.body, function(stat) {
return is_empty(stat)
|| stat instanceof AST_Defun
|| stat instanceof AST_Var && all(stat.definitions, function(var_def) {
return !var_def.value;
});
});
}
function loop_body(x) {
if (x instanceof AST_IterationStatement) {
return x.body instanceof AST_BlockStatement ? x.body : x;
@@ -5493,15 +5503,15 @@ merge(Compressor.prototype, {
var stat = branch.body[branch.body.length - 1];
if (is_break(stat, compressor)) branch.body.pop();
if (branch === default_branch) {
if (!is_body_empty(branch)) break;
if (!has_declarations_only(branch)) break;
} else if (branch.expression.has_side_effects(compressor)) {
break;
} else if (default_branch) {
if (!is_body_empty(default_branch)) break;
if (!has_declarations_only(default_branch)) break;
if (body[body.length - 2] !== default_branch) break;
default_branch.body = default_branch.body.concat(branch.body);
branch.body = [];
} else if (!is_body_empty(branch)) break;
} else if (!has_declarations_only(branch)) break;
eliminate_branch(branch);
if (body.pop() === default_branch) default_branch = null;
}
@@ -5543,16 +5553,6 @@ merge(Compressor.prototype, {
return node instanceof AST_Break && tw.loopcontrol_target(node) === self;
}
function is_body_empty(branch) {
return all(branch.body, function(stat) {
return is_empty(stat)
|| stat instanceof AST_Defun
|| stat instanceof AST_Var && all(stat.definitions, function(var_def) {
return !var_def.value;
});
});
}
function eliminate_branch(branch, prev) {
if (prev && !aborts(prev)) {
prev.body = prev.body.concat(branch.body);
@@ -5564,8 +5564,8 @@ merge(Compressor.prototype, {
OPT(AST_Try, function(self, compressor) {
self.body = tighten_body(self.body, compressor);
if (self.bcatch && self.bfinally && all(self.bfinally.body, is_empty)) self.bfinally = null;
if (compressor.option("dead_code") && all(self.body, is_empty)) {
if (compressor.option("dead_code")) {
if (has_declarations_only(self)) {
var body = [];
if (self.bcatch) {
extract_declarations_from_unreachable_code(self.bcatch, body);
@@ -5579,11 +5579,21 @@ merge(Compressor.prototype, {
});
});
}
if (self.bfinally) body = body.concat(self.bfinally.body);
[].unshift.apply(body, self.body);
if (self.bfinally) [].push.apply(body, self.bfinally.body);
return make_node(AST_BlockStatement, self, {
body: body
}).optimize(compressor);
}
if (self.bfinally && has_declarations_only(self.bfinally)) {
var body = self.body.concat(self.bfinally.body);
if (!self.bcatch) return make_node(AST_BlockStatement, self, {
body: body
}).optimize(compressor);
self.body = body;
self.bfinally = null;
}
}
return self;
});

63
test/compress/dead-code.js
View File

@@ -97,6 +97,66 @@ dead_code_constant_boolean_should_warn_more: {
node_version: "<=4"
}
trim_try: {
options = {
dead_code: true,
}
input: {
try {
var a;
} catch (e) {
console.log("FAIL");
} finally {
console.log(a);
}
}
expect: {
var a;
console.log(a);
}
expect_stdout: "undefined"
}
trim_finally_1: {
options = {
dead_code: true,
}
input: {
try {
console.log("PASS");
} finally {
var a;
}
}
expect: {
console.log("PASS");
var a;
}
expect_stdout: "PASS"
}
trim_finally_2: {
options = {
dead_code: true,
}
input: {
try {
console.log("PASS");
} catch (e) {
} finally {
var a;
}
}
expect: {
try {
console.log("PASS");
var a;
} catch (e) {
}
}
expect_stdout: "PASS"
}
try_catch_finally: {
options = {
conditionals: true,
@@ -130,10 +190,7 @@ try_catch_finally: {
a = 3;
console.log("PASS");
}();
try {
console.log(a);
} finally {
}
}
expect_stdout: [
"PASS",