JS: revert performance regression from 61a4bb8, up to 120% faster for…

… antd.js

js/js_test.go

@@ -711,6 +711,7 @@ func TestJS(t *testing.T) {
  {`a=5;with(b=4){}`, `with(a=5,b=4);`},
  {`(function(){})();(function(){})()`, `(function(){})(),function(){}()`},
  //{`for(var a=0;;){var b=5;var d=6;for(var c=0;;);}`, `for(a=0;;)for(var a,b=5,d=6,c=0;;);`}, // TODO
+ //{`var aaaa=[];for(var b=0;;){}for(var b in aaaa){}var aaaa=[];for(var b=0;;){}`, `for(var aaaa=[],b=0;;);for(b in aaaa);for(aaaa=[],b=0;;);`}, // TODO
 
  // collapse functions
  //{`var a=function(){return 5}`, `var a=()=>5`},
@@ -808,8 +809,8 @@ func TestJS(t *testing.T) {
  {`export default function Foo(){a}Foo.prototype.bar=b`, `export default function Foo(){a}Foo.prototype.bar=b`}, // #525
  {`(e=1,e=2)`, `e=1,e=2`}, // #528
  {`"\x00\x31 \0\u0000"`, `"\x001 \0\x00"`}, // #577
- {`function transform(){{var aaaa=[];for(var b=0;;){}for(var b in aaaa){}var aaaa=[];for(var b=0;;){}}}`, `function transform(){{for(var aaaa=[],b=0;;);for(b in aaaa);for(aaaa=[],b=0;;);}}`}, // #619
- {`for(var a=0;;){var b=5;for(var c=0;;);}`, `for(var b,c,a=0;;)for(b=5,c=0;;);`}, // #634
+ {`function transform(){{var aaaa=[];for(var b=0;;){}for(var b in aaaa){}var aaaa=[];for(var b=0;;){}}}`, `function transform(){{for(var aaaa=[],b=0;;);for(b in aaaa);for(var aaaa=[],b=0;;);}}`}, // #619
+ {`for(var a=0;;){var b=5;for(var c=0;;);}`, `for(var b,c,a=0;;)for(b=5,c=0;;);`},  // #634
  {"if(a)for(;;)\n;else b", `if(a)for(;;);else b`}, // #636
  {`'\u000A\u000D'`, "`\n\r`"}, // #653
  {`for(!a;b;c);`, "for(!a;b;c);"}, // #656

js/vars.go

@@ -288,112 +288,90 @@ func mergeVarDeclExprStmt(decl *js.VarDecl, exprStmt *js.ExprStmt, forward bool)
  return false
 }
 
-func (m *jsMinifier) varNameLen(v *js.Var) int {
+func (m *jsMinifier) countHoistLength(ibinding js.IBinding) int {
  if !m.o.KeepVarNames {
- return 2 // assume that var name will be of length one, +1 for the comma
+ return len(bindingVars(ibinding)) * 2 // assume that var name will be of length one, +1 for the comma
  }
- return len(v.Data) + 1 // +1 for the comma when added to other declaration
+
+ n := 0
+ for _, v := range bindingVars(ibinding) {
+ n += len(v.Data) + 1 // +1 for the comma when added to other declaration
+ }
+ return n
 }
 
 func (m *jsMinifier) hoistVars(body *js.BlockStmt) {
- // Hoist all variable declarations in the current module/function scope to the top
- // Find the best var declaration (that results in the shortest code), all others are converted to expressions.
- // This is possible because an ArrayBindingPattern and ObjectBindingPattern can be converted to an ArrayLiteral or ObjectLiteral respectively, as they are supersets of the BindingPatterns.
+ // Hoist all variable declarations in the current module/function scope to the variable
+ // declaration that reduces file size the most. All other declarations are converted to
+ // expressions and their variable names are copied to the only remaining declaration.
+ // This is possible because an ArrayBindingPattern and ObjectBindingPattern can be converted to
+ // an ArrayLiteral or ObjectLiteral respectively, as they are supersets of the BindingPatterns.
  if 1 < len(body.Scope.VarDecls) {
  // Select which variable declarations will be hoisted (convert to expression) and which not
  best := 0
  scores := make([]int, len(body.Scope.VarDecls)) // savings if hoisting target
- hoists := make([][]bool, len(body.Scope.VarDecls))
- for i, target := range body.Scope.VarDecls {
- // keep list of target variables to avoid declaring a var more than once
- var refsTarget []*js.Var
- for _, item := range target.List {
- refsTarget = append(refsTarget, bindingVars(item.Binding)...)
+ hoist := make([]bool, len(body.Scope.VarDecls))
+ for i, varDecl := range body.Scope.VarDecls {
+ hoist[i] = true
+ if varDecl.InForInOf {
+ continue
  }
 
- hoists[i] = make([]bool, len(body.Scope.VarDecls))
- for j, varDecl := range body.Scope.VarDecls {
- if i == j {
- hoists[i][j] = false
- continue
- }
-
- score := 4 // "var "
- hoists[i][j] = true
- if !varDecl.InForInOf {
- // variable names in for-in or for-of cannot be removed
- n := 0 // total number of vars with decls
- nArrays := 0 // of which lhs arrays
- nObjects := 0 // of which lhs objects
- nNames := 0 // length of var names and commas
- hasDefinitions := false
- for k, item := range varDecl.List {
- if item.Default != nil {
- // move arrays/objects to the front (saves a space)
- if _, ok := item.Binding.(*js.BindingObject); ok {
- if k != 0 && nArrays == 0 && nObjects == 0 {
- varDecl.List[0], varDecl.List[k] = varDecl.List[k], varDecl.List[0]
- }
- nObjects++
- } else if _, ok := item.Binding.(*js.BindingArray); ok {
- if k != 0 && nArrays == 0 && nObjects == 0 {
- varDecl.List[0], varDecl.List[k] = varDecl.List[k], varDecl.List[0]
- }
- nArrays++
- }
-
- refs := bindingVars(item.Binding)
- CountNamesLoop:
- for _, ref := range refs {
- for _, v := range refsTarget {
- if ref == v {
- // already exists in target
- continue CountNamesLoop
- }
- }
-
- // declaration separate from assignment will copy var name + comma
- nNames += m.varNameLen(ref)
- refsTarget = append(refsTarget, ref)
- }
- hasDefinitions = true
- n++
+ // variable names in for-in or for-of cannot be removed
+ n := 0 // total number of vars with decls
+ score := 3 // "var"
+ nArrays := 0 // of which lhs arrays
+ nObjects := 0 // of which lhs objects
+ hasDefinitions := false
+ for j, item := range varDecl.List {
+ if item.Default != nil {
+ // move arrays/objects to the front (saves a space)
+ if _, ok := item.Binding.(*js.BindingObject); ok {
+ if j != 0 && nArrays == 0 && nObjects == 0 {
+ varDecl.List[0], varDecl.List[j] = varDecl.List[j], varDecl.List[0]
  }
+ nObjects++
+ } else if _, ok := item.Binding.(*js.BindingArray); ok {
+ if j != 0 && nArrays == 0 && nObjects == 0 {
+ varDecl.List[0], varDecl.List[j] = varDecl.List[j], varDecl.List[0]
+ }
+ nArrays++
  }
- if hasDefinitions {
- score -= nNames // copy var names and commas to target
- } else if varDecl.InFor {
- score-- // semicolon can be reused
- }
- if nObjects != 0 && !varDecl.InFor && nObjects == n {
- score -= 2 // required parenthesis around braces
- }
- if nArrays != 0 || nObjects != 0 {
- score-- // space after var disappears
- }
- if score < 0 {
- // don't hoist if it increases the amount of characters
- hoists[i][j] = false
- score = 0
- }
+ score -= m.countHoistLength(item.Binding) // var names and commas
+ hasDefinitions = true
+ n++
  }
- scores[i] += score
  }
- if scores[best] < scores[i] || body.Scope.VarDecls[best].InForInOf {
- // select var decl with the most savings if hoist target
+ if nArrays == 0 && nObjects == 0 {
+ score++ // required space after var
+ }
+ if !hasDefinitions && varDecl.InFor {
+ score-- // semicolon can be reused
+ }
+ if nObjects != 0 && !varDecl.InFor && nObjects == n {
+ // required parenthesis around braces to not confound it with a block statement
+ score -= 2
+ }
+ if score < scores[best] || body.Scope.VarDecls[best].InForInOf {
+ // select var decl that reduces the least when hoist target
  best = i
  }
+ if score < 0 {
+ // don't hoist if it increases the amount of characters
+ hoist[i] = false
+ }
+ scores[i] = score
  }
- if scores[best] < 0 || body.Scope.VarDecls[best].InForInOf {
+ if body.Scope.VarDecls[best].InForInOf {
  // no savings possible
  return
  }
 
- hoist := hoists[best]
  decl := body.Scope.VarDecls[best]
  if 10000 < len(decl.List) {
  return
  }
+ hoist[best] = false
 
  // get original declarations
  orig := []*js.Var{}