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authorMihai Bazon <mihai@bazon.net>2013-10-04 13:17:25 +0300
committerMihai Bazon <mihai@bazon.net>2013-10-04 13:17:25 +0300
commitf2348dd98baeb7dc3e0542465ede897c15d7cbc9 (patch)
tree8a14ff70c67377e34c38598d93c377fcdb0ef484
parent253c7c23258e9c783459f683a385bb518f18403a (diff)
downloadtracifyjs-f2348dd98baeb7dc3e0542465ede897c15d7cbc9.tar.gz
tracifyjs-f2348dd98baeb7dc3e0542465ede897c15d7cbc9.zip
Rename clean_getters to pure_getters; add pure_funcs.
-rw-r--r--README.md31
-rw-r--r--lib/compress.js15
2 files changed, 41 insertions, 5 deletions
diff --git a/README.md b/README.md
index 6980878c..3a4d27a5 100644
--- a/README.md
+++ b/README.md
@@ -184,38 +184,67 @@ you can pass a comma-separated list of options. Options are in the form
to set `true`; it's effectively a shortcut for `foo=true`).
- `sequences` -- join consecutive simple statements using the comma operator
+
- `properties` -- rewrite property access using the dot notation, for
example `foo["bar"] → foo.bar`
+
- `dead_code` -- remove unreachable code
+
- `drop_debugger` -- remove `debugger;` statements
+
- `unsafe` (default: false) -- apply "unsafe" transformations (discussion below)
+
- `conditionals` -- apply optimizations for `if`-s and conditional
expressions
+
- `comparisons` -- apply certain optimizations to binary nodes, for example:
`!(a <= b) → a > b` (only when `unsafe`), attempts to negate binary nodes,
e.g. `a = !b && !c && !d && !e → a=!(b||c||d||e)` etc.
+
- `evaluate` -- attempt to evaluate constant expressions
+
- `booleans` -- various optimizations for boolean context, for example `!!a
? b : c → a ? b : c`
+
- `loops` -- optimizations for `do`, `while` and `for` loops when we can
statically determine the condition
+
- `unused` -- drop unreferenced functions and variables
+
- `hoist_funs` -- hoist function declarations
+
- `hoist_vars` (default: false) -- hoist `var` declarations (this is `false`
by default because it seems to increase the size of the output in general)
+
- `if_return` -- optimizations for if/return and if/continue
+
- `join_vars` -- join consecutive `var` statements
+
- `cascade` -- small optimization for sequences, transform `x, x` into `x`
and `x = something(), x` into `x = something()`
+
- `warnings` -- display warnings when dropping unreachable code or unused
declarations etc.
+
- `negate_iife` -- negate "Immediately-Called Function Expressions"
where the return value is discarded, to avoid the parens that the
code generator would insert.
-- `clean_getters` -- the default is `false`. If you pass `true` for
+
+- `pure_getters` -- the default is `false`. If you pass `true` for
this, UglifyJS will assume that object property access
(e.g. `foo.bar` or `foo["bar"]`) doesn't have any side effects.
+- `pure_funcs` -- default `null`. You can pass an array of names and
+ UglifyJS will assume that those functions do not produce side
+ effects. DANGER: will not check if the name is redefined in scope.
+ An example case here, for instance `var q = Math.floor(a/b)`. If
+ variable `q` is not used elsewhere, UglifyJS will drop it, but will
+ still keep the `Math.floor(a/b)`, not knowing what it does. You can
+ pass `pure_funcs: [ 'Math.floor' ]` to let it know that this
+ function won't produce any side effect, in which case the whole
+ statement would get discarded. The current implementation adds some
+ overhead (compression will be slower).
+
### The `unsafe` option
It enables some transformations that *might* break code logic in certain
diff --git a/lib/compress.js b/lib/compress.js
index 76cbc748..4dd273b5 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -66,7 +66,8 @@ function Compressor(options, false_by_default) {
join_vars : !false_by_default,
cascade : !false_by_default,
side_effects : !false_by_default,
- clean_getters : false,
+ pure_getters : false,
+ pure_funcs : null,
negate_iife : !false_by_default,
screw_ie8 : false,
@@ -809,6 +810,12 @@ merge(Compressor.prototype, {
def(AST_Constant, function(compressor){ return false });
def(AST_This, function(compressor){ return false });
+ def(AST_Call, function(compressor){
+ var pure = compressor.option("pure_funcs");
+ if (!pure) return true;
+ return pure.indexOf(this.expression.print_to_string()) < 0;
+ });
+
def(AST_Block, function(compressor){
for (var i = this.body.length; --i >= 0;) {
if (this.body[i].has_side_effects(compressor))
@@ -855,16 +862,16 @@ merge(Compressor.prototype, {
return false;
});
def(AST_Dot, function(compressor){
- if (!compressor.option("clean_getters")) return true;
+ if (!compressor.option("pure_getters")) return true;
return this.expression.has_side_effects(compressor);
});
def(AST_Sub, function(compressor){
- if (!compressor.option("clean_getters")) return true;
+ if (!compressor.option("pure_getters")) return true;
return this.expression.has_side_effects(compressor)
|| this.property.has_side_effects(compressor);
});
def(AST_PropAccess, function(compressor){
- return !compressor.option("clean_getters");
+ return !compressor.option("pure_getters");
});
def(AST_Seq, function(compressor){
return this.car.has_side_effects(compressor)