diff options
Diffstat (limited to 'lib/compress.js')
| -rw-r--r-- | lib/compress.js | 245 |
1 files changed, 117 insertions, 128 deletions
diff --git a/lib/compress.js b/lib/compress.js index 596b03fa..a3641573 100644 --- a/lib/compress.js +++ b/lib/compress.js @@ -642,151 +642,134 @@ merge(Compressor.prototype, { // and if it has exactly one reference then attempt to replace its reference // in the statement with the var value and then erase the var definition. - var self = compressor.self(); - var var_defs_removed = false; + 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]; - if (stat instanceof AST_Definitions) continue; - - // Process child blocks of statement if present. - [stat, stat.body, stat.alternative, stat.bcatch, stat.bfinally].forEach(function(node) { - node && node.body && collapse_single_use_vars(node.body, compressor); - }); - // The variable definition must precede a statement. - if (stat_index <= 0) break; - var prev_stat_index = stat_index - 1; - var prev_stat = statements[prev_stat_index]; - if (!(prev_stat instanceof AST_Definitions)) continue; - var var_defs = prev_stat.definitions; - if (var_defs == null) continue; - - var var_names_seen = {}; + var var_names_seen = Object.create(null); var side_effects_encountered = false; var lvalues_encountered = false; - var lvalues = {}; + var lvalues = Object.create(null); + var prev_stat_index, var_defs, var_defs_index; // Scan variable definitions from right to left. - for (var var_defs_index = var_defs.length; --var_defs_index >= 0;) { - - // Obtain var declaration and var name with basic sanity check. - var var_decl = var_defs[var_defs_index]; - if (var_decl.value == null) break; - var var_name = var_decl.name.name; - if (!var_name || !var_name.length) break; - - // 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 cases with just one reference to the variable. - var def = self.find_variable && self.find_variable(var_name); - if (!def || !def.references || def.references.length !== 1 - || var_name == "arguments" || (!toplevel && def.global)) { - side_effects_encountered = true; - continue; + 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; } - 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) break; - - // Constant single use vars can be replaced in any scope. - if (var_decl.value.is_constant()) { - var ctt = new TreeTransformer(function(node) { - var parent = ctt.parent(); - if (parent instanceof AST_IterationStatement - && (parent.condition === node || parent.init === node)) { - return node; - } - if (node === ref) - return replace_var(node, parent, true); - }); - stat.transform(ctt); - continue; + } else if (stat_index > 0) { + // The variable definition must precede a statement. + prev_stat_index = stat_index - 1; + 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; } + } + } - // Restrict var replacement to constants if side effects encountered. - if (side_effects_encountered |= lvalues_encountered) continue; + return statements; - 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 !== self) { - side_effects_encountered |= value_has_side_effects; - continue; - } + 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; + + // Restrict var replacement to constants if side effects encountered. + if (side_effects_encountered |= lvalues_encountered) return; - // 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; + return; + } + + // 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_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; } - }); - 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) return node; - var parent = tt.parent(); - if (node instanceof AST_Lambda - || 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(), self)) - || (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(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; + 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; } - ); - stat.transform(tt); - } - } - - // Remove extraneous empty statments in block after removing var definitions. - // Leave at least one statement in `statements`. - if (var_defs_removed) for (var i = statements.length; --i >= 0;) { - if (statements.length > 1 && statements[i] instanceof AST_EmptyStatement) - statements.splice(i, 1); + }, + 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); } - return statements; - function is_lvalue(node, parent) { return node instanceof AST_SymbolRef && is_lhs(node, parent); } - function replace_var(node, parent, is_constant) { + + function replace_var(var_decl, node, parent, is_constant) { if (is_lvalue(node, parent)) return node; // Remove var definition and return its value to the TreeTransformer to replace. @@ -795,14 +778,19 @@ merge(Compressor.prototype, { var_defs.splice(var_defs_index, 1); if (var_defs.length === 0) { - statements[prev_stat_index] = make_node(AST_EmptyStatement, self); - var_defs_removed = true; + statements.splice(prev_stat_index, 1); + stat_index--; } // Further optimize statement after substitution. stat.reset_opt_flags(compressor); - compressor.info("Collapsing " + (is_constant ? "constant" : "variable") + - " " + var_name + " [{file}:{line},{col}]", node.start); + compressor.info("Collapsing {type} {name} [{file}:{line},{col}]", { + type: is_constant ? "constant" : "variable", + name: var_decl.name.name, + file: node.start.file, + line: node.start.line, + col: node.start.col + }); CHANGED = true; return value; } @@ -1746,6 +1734,7 @@ merge(Compressor.prototype, { def(AST_SymbolRef, function(compressor){ return this.undeclared(); }); + def(AST_SymbolDeclaration, return_false); def(AST_Object, function(compressor){ return any(this.properties, compressor); }); |