[Pkg-javascript-commits] [uglifyjs] 15/491: improve `collapse_vars` on `AST_Var` (#1828)
Jonas Smedegaard
dr at jones.dk
Wed Feb 14 19:51:17 UTC 2018
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js pushed a commit to annotated tag debian/3.3.10-1
in repository uglifyjs.
commit 4dcff038cb1a6951a0b20d1345bfdb27d756301c
Author: Alex Lam S.L <alexlamsl at gmail.com>
Date: Wed Apr 19 04:49:09 2017 +0800
improve `collapse_vars` on `AST_Var` (#1828)
Perform the same cascaded scanning within `var` statement as we do on array of statements.
---
lib/compress.js | 197 +++++++++++++++++++++--------------------
test/compress/collapse_vars.js | 23 +++++
2 files changed, 124 insertions(+), 96 deletions(-)
diff --git a/lib/compress.js b/lib/compress.js
index eb54f75..2612d9a 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -644,21 +644,21 @@ merge(Compressor.prototype, {
var scope = compressor.find_parent(AST_Scope);
var toplevel = compressor.option("toplevel");
- for (var stat_index = statements.length; --stat_index >= 0;) {
- var stat = statements[stat_index];
-
- var var_names_seen = Object.create(null);
- var side_effects_encountered = false;
- var lvalues_encountered = false;
- var lvalues = Object.create(null);
- var prev_stat_index, var_defs, var_defs_index;
-
+ var stat_index;
+ var prev_stat_index;
+ var def_stat_index;
+ var stat;
+ var var_defs;
+ var var_defs_index;
+ for (stat_index = statements.length; --stat_index >= 0;) {
+ stat = statements[stat_index];
// Scan variable definitions from right to left.
if (stat instanceof AST_Definitions) {
prev_stat_index = stat_index;
var_defs = stat.definitions;
- for (var_defs_index = var_defs.length - 1; --var_defs_index >= 0;) {
- if (collapse(var_defs[var_defs_index + 1])) break;
+ for (def_stat_index = var_defs.length; --def_stat_index >= 1;) {
+ stat = var_defs[def_stat_index];
+ scan_var_defs(def_stat_index);
}
} else if (stat_index > 0) {
// The variable definition must precede a statement.
@@ -666,103 +666,107 @@ merge(Compressor.prototype, {
var prev_stat = statements[prev_stat_index];
if (!(prev_stat instanceof AST_Definitions)) continue;
var_defs = prev_stat.definitions;
- for (var_defs_index = var_defs.length; --var_defs_index >= 0;) {
- if (collapse(stat)) break;
- }
+ scan_var_defs(var_defs.length);
}
}
return statements;
- function collapse(stat) {
- var var_decl = var_defs[var_defs_index];
- // `drop_unused()` shuffles variables without values to the top,
- // so we can terminate upon first sighting as an optimization.
- if (var_decl.value == null) return true;
- var var_name = var_decl.name.name;
-
- // Bail if we've seen a var definition of same name before.
- if (var_name in var_names_seen) return true;
- var_names_seen[var_name] = true;
-
- // Only interested in non-constant values.
- if (var_decl.value.is_constant()) return;
-
- // Only interested in cases with just one reference to the variable.
- var def = var_decl.name.definition();
- if (def.references.length !== 1
- || var_name == "arguments" || (!toplevel && def.global)) {
- side_effects_encountered = true;
- return;
- }
- var ref = def.references[0];
-
- // Don't replace ref if eval() or with statement in scope.
- if (ref.scope.uses_eval || ref.scope.uses_with) return true;
+ function scan_var_defs(end_pos) {
+ var var_names_seen = Object.create(null);
+ var side_effects_encountered = false;
+ var lvalues_encountered = false;
+ var lvalues = Object.create(null);
+ for (var_defs_index = end_pos; --var_defs_index >= 0;) {
+ var var_decl = var_defs[var_defs_index];
+ // `drop_unused()` shuffles variables without values to the top,
+ // so we can terminate upon first sighting as an optimization.
+ if (var_decl.value == null) break;
+ var var_name = var_decl.name.name;
+
+ // Bail if we've seen a var definition of same name before.
+ if (var_name in var_names_seen) break;
+ var_names_seen[var_name] = true;
+
+ // Only interested in non-constant values.
+ if (var_decl.value.is_constant()) continue;
+
+ // Only interested in cases with just one reference to the variable.
+ var def = var_decl.name.definition();
+ if (def.references.length !== 1
+ || var_name == "arguments" || (!toplevel && def.global)) {
+ side_effects_encountered = true;
+ continue;
+ }
+ var ref = def.references[0];
- // Restrict var replacement to constants if side effects encountered.
- if (side_effects_encountered |= lvalues_encountered) return;
+ // Don't replace ref if eval() or with statement in scope.
+ if (ref.scope.uses_eval || ref.scope.uses_with) break;
- var value_has_side_effects = var_decl.value.has_side_effects(compressor);
- // Non-constant single use vars can only be replaced in same scope.
- if (ref.scope !== scope) {
- side_effects_encountered |= value_has_side_effects;
- return;
- }
+ // Restrict var replacement to constants if side effects encountered.
+ if (side_effects_encountered |= lvalues_encountered) continue;
- // Detect lvalues in var value.
- var tw = new TreeWalker(function(node){
- if (node instanceof AST_SymbolRef && is_lvalue(node, tw.parent())) {
- lvalues[node.name] = lvalues_encountered = true;
+ var value_has_side_effects = var_decl.value.has_side_effects(compressor);
+ // Non-constant single use vars can only be replaced in same scope.
+ if (ref.scope !== scope) {
+ side_effects_encountered |= value_has_side_effects;
+ continue;
}
- });
- var_decl.value.walk(tw);
-
- // Replace the non-constant single use var in statement if side effect free.
- var unwind = false;
- var tt = new TreeTransformer(
- function preorder(node) {
- if (unwind || node instanceof AST_Scope && node !== scope) return node;
- var parent = tt.parent();
- if (node instanceof AST_Try
- || node instanceof AST_With
- || node instanceof AST_Case
- || node instanceof AST_IterationStatement
- || (parent instanceof AST_If && node !== parent.condition)
- || (parent instanceof AST_Conditional && node !== parent.condition)
- || (node instanceof AST_SymbolRef
- && value_has_side_effects
- && !are_references_in_scope(node.definition(), scope))
- || (parent instanceof AST_Binary
- && (parent.operator == "&&" || parent.operator == "||")
- && node === parent.right)
- || (parent instanceof AST_Switch && node !== parent.expression)) {
- return side_effects_encountered = unwind = true, node;
+
+ // Detect lvalues in var value.
+ var tw = new TreeWalker(function(node){
+ if (node instanceof AST_SymbolRef && is_lvalue(node, tw.parent())) {
+ lvalues[node.name] = lvalues_encountered = true;
}
- function are_references_in_scope(def, scope) {
- if (def.orig.length === 1
- && def.orig[0] instanceof AST_SymbolDefun) return true;
- if (def.scope !== scope) return false;
- var refs = def.references;
- for (var i = 0, len = refs.length; i < len; i++) {
- if (refs[i].scope !== scope) return false;
+ });
+ var_decl.value.walk(tw);
+
+ // Replace the non-constant single use var in statement if side effect free.
+ var unwind = false;
+ var tt = new TreeTransformer(
+ function preorder(node) {
+ if (unwind || node instanceof AST_Scope && node !== scope) return node;
+ var parent = tt.parent();
+ if (node instanceof AST_Try
+ || node instanceof AST_With
+ || node instanceof AST_Case
+ || node instanceof AST_IterationStatement
+ || (parent instanceof AST_If && node !== parent.condition)
+ || (parent instanceof AST_Conditional && node !== parent.condition)
+ || (node instanceof AST_SymbolRef
+ && value_has_side_effects
+ && !are_references_in_scope(node.definition(), scope))
+ || (parent instanceof AST_Binary
+ && (parent.operator == "&&" || parent.operator == "||")
+ && node === parent.right)
+ || (parent instanceof AST_Switch && node !== parent.expression)) {
+ return side_effects_encountered = unwind = true, node;
+ }
+ function are_references_in_scope(def, scope) {
+ if (def.orig.length === 1
+ && def.orig[0] instanceof AST_SymbolDefun) return true;
+ if (def.scope !== scope) return false;
+ var refs = def.references;
+ for (var i = 0, len = refs.length; i < len; i++) {
+ if (refs[i].scope !== scope) return false;
+ }
+ return true;
+ }
+ },
+ function postorder(node) {
+ if (unwind) return node;
+ if (node === ref)
+ return unwind = true, replace_var(var_decl, node, tt.parent(), false);
+ if (side_effects_encountered |= node.has_side_effects(compressor))
+ return unwind = true, node;
+ if (lvalues_encountered && node instanceof AST_SymbolRef && node.name in lvalues) {
+ side_effects_encountered = true;
+ return unwind = true, node;
}
- return true;
- }
- },
- function postorder(node) {
- if (unwind) return node;
- if (node === ref)
- return unwind = true, replace_var(var_decl, node, tt.parent(), false);
- if (side_effects_encountered |= node.has_side_effects(compressor))
- return unwind = true, node;
- if (lvalues_encountered && node instanceof AST_SymbolRef && node.name in lvalues) {
- side_effects_encountered = true;
- return unwind = true, node;
}
- }
- );
- stat.transform(tt);
+ );
+ stat.transform(tt);
+ }
}
function is_lvalue(node, parent) {
@@ -777,6 +781,7 @@ merge(Compressor.prototype, {
var_decl.value = null;
var_defs.splice(var_defs_index, 1);
+ def_stat_index--;
if (var_defs.length === 0) {
statements.splice(prev_stat_index, 1);
stat_index--;
diff --git a/test/compress/collapse_vars.js b/test/compress/collapse_vars.js
index 0f82b74..94515a6 100644
--- a/test/compress/collapse_vars.js
+++ b/test/compress/collapse_vars.js
@@ -1654,3 +1654,26 @@ iife_2: {
}(bar());
}
}
+
+var_defs: {
+ options = {
+ collapse_vars:true, sequences:true, properties:true, dead_code: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, cascade:true, side_effects:true
+ }
+ input: {
+ var f1 = function(x, y) {
+ var a, b, r = x + y, q = r * r, z = q - r, a = z, b = 7;
+ console.log(a + b);
+ };
+ f1("1", 0);
+ }
+ expect: {
+ var f1 = function(x, y) {
+ var r = x + y, a = r * r - r, b = 7;
+ console.log(a + b);
+ };
+ f1("1", 0);
+ }
+ expect_stdout: "97"
+}
--
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