cmd/compile/internal/syntax: replace inlined statement lists with syntax.BlockStmt

This simplifies the code and removes a premature optimization.
It increases the amount of allocated syntax.Node space by ~0.4%
for parsing all of std lib, which is negligible.

Before the change (best of 5 runs):

  $ go test -run StdLib -fast
  parsed 1517022 lines (3394 files) in 793.487886ms (1911840 lines/s)
  allocated 387.086Mb (267B/line, 487.828Mb/s)

After the change (best of 5 runs):

  $ go test -run StdLib -fast
  parsed 1516911 lines (3392 files) in 805.028655ms (1884294 lines/s)
  allocated 388.466Mb (268B/line, 482.549Mb/s)

Change-Id: Id19d6210fdc62393862ba3b04913352d95c599be
Reviewed-on: https://go-review.googlesource.com/38439
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

6 files changed, 80 insertions, 111 deletions

diff --git a/src/cmd/compile/internal/gc/noder.go b/src/cmd/compile/internal/gc/noder.go
index 41c05c6480..d203603816 100644
--- a/src/cmd/compile/internal/gc/noder.go
+++ b/src/cmd/compile/internal/gc/noder.go
@@ -297,7 +297,7 @@ func (p *noder) funcDecl(fun *syntax.FuncDecl) *Node {
 
 	var body []*Node
 	if fun.Body != nil {
-		body = p.stmts(fun.Body)
+		body = p.stmts(fun.Body.List)
 		if body == nil {
 			body = []*Node{p.nod(fun, OEMPTY, nil, nil)}
 		}
@@ -314,7 +314,11 @@ func (p *noder) funcDecl(fun *syntax.FuncDecl) *Node {
 		yyerror("go:nosplit and go:systemstack cannot be combined")
 	}
 	f.Func.Pragma = pragma
-	lineno = Ctxt.PosTable.XPos(fun.Rbrace)
+	var rbrace src.Pos
+	if fun.Body != nil {
+		rbrace = fun.Body.Rbrace
+	}
+	lineno = Ctxt.PosTable.XPos(rbrace)
 	f.Func.Endlineno = lineno
 
 	funcbody(f)
@@ -450,8 +454,8 @@ func (p *noder) expr(expr syntax.Expr) *Node {
 		return p.nod(expr, OKEY, p.expr(expr.Key), p.wrapname(expr.Value, p.expr(expr.Value)))
 	case *syntax.FuncLit:
 		closurehdr(p.typeExpr(expr.Type))
-		body := p.stmts(expr.Body)
-		lineno = Ctxt.PosTable.XPos(expr.Rbrace)
+		body := p.stmts(expr.Body.List)
+		lineno = Ctxt.PosTable.XPos(expr.Body.Rbrace)
 		return p.setlineno(expr, closurebody(body))
 	case *syntax.ParenExpr:
 		return p.nod(expr, OPAREN, p.expr(expr.X), nil)
@@ -676,7 +680,12 @@ func (p *noder) stmt(stmt syntax.Stmt) *Node {
 	case *syntax.LabeledStmt:
 		return p.labeledStmt(stmt)
 	case *syntax.BlockStmt:
-		return p.body(stmt.Body)
+		l := p.blockStmt(stmt)
+		if len(l) == 0 {
+			// TODO(mdempsky): Line number?
+			return nod(OEMPTY, nil, nil)
+		}
+		return liststmt(l)
 	case *syntax.ExprStmt:
 		return p.wrapname(stmt, p.expr(stmt.X))
 	case *syntax.SendStmt:
@@ -781,18 +790,9 @@ func (p *noder) stmt(stmt syntax.Stmt) *Node {
 	panic("unhandled Stmt")
 }
 
-func (p *noder) body(body []syntax.Stmt) *Node {
-	l := p.bodyList(body)
-	if len(l) == 0 {
-		// TODO(mdempsky): Line number?
-		return nod(OEMPTY, nil, nil)
-	}
-	return liststmt(l)
-}
-
-func (p *noder) bodyList(body []syntax.Stmt) []*Node {
+func (p *noder) blockStmt(stmt *syntax.BlockStmt) []*Node {
 	markdcl()
-	nodes := p.stmts(body)
+	nodes := p.stmts(stmt.List)
 	popdcl()
 	return nodes
 }
@@ -806,7 +806,7 @@ func (p *noder) ifStmt(stmt *syntax.IfStmt) *Node {
 	if stmt.Cond != nil {
 		n.Left = p.expr(stmt.Cond)
 	}
-	n.Nbody.Set(p.bodyList(stmt.Then))
+	n.Nbody.Set(p.blockStmt(stmt.Then))
 	if stmt.Else != nil {
 		e := p.stmt(stmt.Else)
 		if e.Op == OBLOCK && e.Ninit.Len() == 0 {
@@ -848,7 +848,7 @@ func (p *noder) forStmt(stmt *syntax.ForStmt) *Node {
 			n.Right = p.stmt(stmt.Post)
 		}
 	}
-	n.Nbody.Set(p.bodyList(stmt.Body))
+	n.Nbody.Set(p.blockStmt(stmt.Body))
 	popdcl()
 	return n
 }
diff --git a/src/cmd/compile/internal/syntax/nodes.go b/src/cmd/compile/internal/syntax/nodes.go
index a99cb008f2..4fb50b1f4a 100644
--- a/src/cmd/compile/internal/syntax/nodes.go
+++ b/src/cmd/compile/internal/syntax/nodes.go
@@ -97,13 +97,12 @@ type (
 	// func Receiver Name Type { Body }
 	// func Receiver Name Type
 	FuncDecl struct {
-		Attr           map[string]bool // go:attr map
-		Recv           *Field          // nil means regular function
-		Name           *Name
-		Type           *FuncType
-		Body           []Stmt // nil means no body (forward declaration)
-		Lbrace, Rbrace src.Pos
-		Pragma         Pragma // TODO(mdempsky): Cleaner solution.
+		Attr   map[string]bool // go:attr map
+		Recv   *Field          // nil means regular function
+		Name   *Name
+		Type   *FuncType
+		Body   *BlockStmt // nil means no body (forward declaration)
+		Pragma Pragma     // TODO(mdempsky): Cleaner solution.
 		decl
 	}
 )
@@ -141,10 +140,10 @@ type (
 
 	// Type { ElemList[0], ElemList[1], ... }
 	CompositeLit struct {
-		Type           Expr // nil means no literal type
-		ElemList       []Expr
-		NKeys          int // number of elements with keys
-		Lbrace, Rbrace src.Pos
+		Type     Expr // nil means no literal type
+		ElemList []Expr
+		NKeys    int // number of elements with keys
+		Rbrace   src.Pos
 		expr
 	}
 
@@ -156,9 +155,8 @@ type (
 
 	// func Type { Body }
 	FuncLit struct {
-		Type           *FuncType
-		Body           []Stmt
-		Lbrace, Rbrace src.Pos
+		Type *FuncType
+		Body *BlockStmt
 		expr
 	}
 
@@ -323,7 +321,7 @@ type (
 	}
 
 	BlockStmt struct {
-		Body   []Stmt
+		List   []Stmt
 		Rbrace src.Pos
 		stmt
 	}
@@ -367,20 +365,18 @@ type (
 	}
 
 	IfStmt struct {
-		Init           SimpleStmt
-		Cond           Expr
-		Then           []Stmt
-		Lbrace, Rbrace src.Pos // of Then branch
-		Else           Stmt    // either *IfStmt or *BlockStmt
+		Init SimpleStmt
+		Cond Expr
+		Then *BlockStmt
+		Else Stmt // either *IfStmt or *BlockStmt
 		stmt
 	}
 
 	ForStmt struct {
-		Init           SimpleStmt // incl. *RangeClause
-		Cond           Expr
-		Post           SimpleStmt
-		Body           []Stmt
-		Lbrace, Rbrace src.Pos
+		Init SimpleStmt // incl. *RangeClause
+		Cond Expr
+		Post SimpleStmt
+		Body *BlockStmt
 		stmt
 	}
 
diff --git a/src/cmd/compile/internal/syntax/nodes_test.go b/src/cmd/compile/internal/syntax/nodes_test.go
index 935a1096c6..ea446235fa 100644
--- a/src/cmd/compile/internal/syntax/nodes_test.go
+++ b/src/cmd/compile/internal/syntax/nodes_test.go
@@ -261,23 +261,23 @@ func TestPos(t *testing.T) {
 	)
 
 	testPos(t, stmts, "package p; func _() { ", "; }",
-		func(f *File) Node { return f.DeclList[0].(*FuncDecl).Body[0] },
+		func(f *File) Node { return f.DeclList[0].(*FuncDecl).Body.List[0] },
 	)
 
 	testPos(t, ranges, "package p; func _() { for ", " {} }",
-		func(f *File) Node { return f.DeclList[0].(*FuncDecl).Body[0].(*ForStmt).Init.(*RangeClause) },
+		func(f *File) Node { return f.DeclList[0].(*FuncDecl).Body.List[0].(*ForStmt).Init.(*RangeClause) },
 	)
 
 	testPos(t, guards, "package p; func _() { switch ", " {} }",
-		func(f *File) Node { return f.DeclList[0].(*FuncDecl).Body[0].(*SwitchStmt).Tag.(*TypeSwitchGuard) },
+		func(f *File) Node { return f.DeclList[0].(*FuncDecl).Body.List[0].(*SwitchStmt).Tag.(*TypeSwitchGuard) },
 	)
 
 	testPos(t, cases, "package p; func _() { switch { ", " } }",
-		func(f *File) Node { return f.DeclList[0].(*FuncDecl).Body[0].(*SwitchStmt).Body[0] },
+		func(f *File) Node { return f.DeclList[0].(*FuncDecl).Body.List[0].(*SwitchStmt).Body[0] },
 	)
 
 	testPos(t, comms, "package p; func _() { select { ", " } }",
-		func(f *File) Node { return f.DeclList[0].(*FuncDecl).Body[0].(*SelectStmt).Body[0] },
+		func(f *File) Node { return f.DeclList[0].(*FuncDecl).Body.List[0].(*SelectStmt).Body[0] },
 	)
 }
 
diff --git a/src/cmd/compile/internal/syntax/parser.go b/src/cmd/compile/internal/syntax/parser.go
index 8232be64ff..39532689e2 100644
--- a/src/cmd/compile/internal/syntax/parser.go
+++ b/src/cmd/compile/internal/syntax/parser.go
@@ -480,11 +480,8 @@ func (p *parser) funcDecl() *FuncDecl {
 
 	f.Name = p.name()
 	f.Type = p.funcType()
-	if lbrace := p.pos(); p.got(_Lbrace) {
-		f.Lbrace = lbrace
-		f.Body = p.funcBody()
-		f.Rbrace = p.pos()
-		p.want(_Rbrace)
+	if p.tok == _Lbrace {
+		f.Body = p.blockStmt("")
 	}
 
 	f.Pragma = p.pragma
@@ -704,16 +701,13 @@ func (p *parser) operand(keep_parens bool) Expr {
 		pos := p.pos()
 		p.next()
 		t := p.funcType()
-		if lbrace := p.pos(); p.got(_Lbrace) {
+		if p.tok == _Lbrace {
 			p.xnest++
 
 			f := new(FuncLit)
 			f.pos = pos
-			f.Lbrace = lbrace
 			f.Type = t
-			f.Body = p.funcBody()
-			f.Rbrace = p.pos()
-			p.want(_Rbrace)
+			f.Body = p.blockStmt("")
 
 			p.xnest--
 			return f
@@ -902,7 +896,6 @@ func (p *parser) complitexpr() *CompositeLit {
 	x := new(CompositeLit)
 	x.pos = p.pos()
 
-	x.Lbrace = p.pos()
 	p.want(_Lbrace)
 	p.xnest++
 
@@ -1619,15 +1612,21 @@ func (p *parser) labeledStmt(label *Name) Stmt {
 	return s
 }
 
-func (p *parser) blockStmt() *BlockStmt {
+func (p *parser) blockStmt(context string) *BlockStmt {
 	if trace {
 		defer p.trace("blockStmt")()
 	}
 
 	s := new(BlockStmt)
 	s.pos = p.pos()
-	p.want(_Lbrace)
-	s.Body = p.stmtList()
+
+	if !p.got(_Lbrace) {
+		p.syntax_error("expecting { after " + context)
+		p.advance(_Name, _Rbrace)
+		// TODO(gri) may be better to return here than to continue (#19663)
+	}
+
+	s.List = p.stmtList()
 	s.Rbrace = p.pos()
 	p.want(_Rbrace)
 
@@ -1657,29 +1656,14 @@ func (p *parser) forStmt() Stmt {
 	s.pos = p.pos()
 
 	s.Init, s.Cond, s.Post = p.header(_For)
-	s.Body, s.Lbrace, s.Rbrace = p.stmtBody("for clause")
+	s.Body = p.blockStmt("for clause")
 
 	return s
 }
 
-// stmtBody parses if and for statement bodies.
-func (p *parser) stmtBody(context string) (body []Stmt, lbrace, rbrace src.Pos) {
-	if trace {
-		defer p.trace("stmtBody")()
-	}
-
-	lbrace = p.pos()
-	if !p.got(_Lbrace) {
-		p.syntax_error("expecting { after " + context)
-		p.advance(_Name, _Rbrace)
-	}
-	body = p.stmtList()
-	rbrace = p.pos()
-	p.want(_Rbrace)
-
-	return
-}
-
+// TODO(gri) This function is now so heavily influenced by the keyword that
+//           it may not make sense anymore to combine all three cases. It
+//           may be simpler to just split it up for each statement kind.
 func (p *parser) header(keyword token) (init SimpleStmt, cond Expr, post SimpleStmt) {
 	p.want(keyword)
 
@@ -1769,14 +1753,14 @@ func (p *parser) ifStmt() *IfStmt {
 	s.pos = p.pos()
 
 	s.Init, s.Cond, _ = p.header(_If)
-	s.Then, s.Lbrace, s.Rbrace = p.stmtBody("if clause")
+	s.Then = p.blockStmt("if clause")
 
 	if p.got(_Else) {
 		switch p.tok {
 		case _If:
 			s.Else = p.ifStmt()
 		case _Lbrace:
-			s.Else = p.blockStmt()
+			s.Else = p.blockStmt("")
 		default:
 			p.syntax_error("else must be followed by if or statement block")
 			p.advance(_Name, _Rbrace)
@@ -1849,7 +1833,7 @@ func (p *parser) caseClause() *CaseClause {
 
 	default:
 		p.syntax_error("expecting case or default or }")
-		p.advance(_Case, _Default, _Rbrace)
+		p.advance(_Colon, _Case, _Default, _Rbrace)
 	}
 
 	c.Colon = p.pos()
@@ -1889,7 +1873,7 @@ func (p *parser) commClause() *CommClause {
 
 	default:
 		p.syntax_error("expecting case or default or }")
-		p.advance(_Case, _Default, _Rbrace)
+		p.advance(_Colon, _Case, _Default, _Rbrace)
 	}
 
 	c.Colon = p.pos()
@@ -1926,7 +1910,7 @@ func (p *parser) stmt() Stmt {
 
 	switch p.tok {
 	case _Lbrace:
-		return p.blockStmt()
+		return p.blockStmt("")
 
 	case _Var:
 		return p.declStmt(p.varDecl)
diff --git a/src/cmd/compile/internal/syntax/parser_test.go b/src/cmd/compile/internal/syntax/parser_test.go
index 06c74cbfba..4c317dab60 100644
--- a/src/cmd/compile/internal/syntax/parser_test.go
+++ b/src/cmd/compile/internal/syntax/parser_test.go
@@ -23,10 +23,7 @@ var src_ = flag.String("src", "parser.go", "source file to parse")
 var verify = flag.Bool("verify", false, "verify idempotent printing")
 
 func TestParse(t *testing.T) {
-	_, err := ParseFile(*src_, nil, nil, 0)
-	if err != nil {
-		t.Fatal(err)
-	}
+	ParseFile(*src_, func(err error) { t.Error(err) }, nil, 0)
 }
 
 func TestStdLib(t *testing.T) {
@@ -81,7 +78,7 @@ func TestStdLib(t *testing.T) {
 	dm := float64(m2.TotalAlloc-m1.TotalAlloc) / 1e6
 
 	fmt.Printf("parsed %d lines (%d files) in %v (%d lines/s)\n", lines, count, dt, int64(float64(lines)/dt.Seconds()))
-	fmt.Printf("allocated %.3fMb (%dB/line, %.3fMb/s)\n", dm, uint64(dm*(1<<20)/float64(lines)), dm/dt.Seconds())
+	fmt.Printf("allocated %.3fMb (%.3fMb/s)\n", dm, dm/dt.Seconds())
 }
 
 func walkDirs(t *testing.T, dir string, action func(string)) {
diff --git a/src/cmd/compile/internal/syntax/printer.go b/src/cmd/compile/internal/syntax/printer.go
index 43876a25c2..426921199e 100644
--- a/src/cmd/compile/internal/syntax/printer.go
+++ b/src/cmd/compile/internal/syntax/printer.go
@@ -349,8 +349,7 @@ func (p *printer) printRawNode(n Node) {
 		p.print(_Name, n.Value) // _Name requires actual value following immediately
 
 	case *FuncLit:
-		p.print(n.Type, blank)
-		p.printBody(n.Body)
+		p.print(n.Type, blank, n.Body)
 
 	case *CompositeLit:
 		if n.Type != nil {
@@ -524,15 +523,20 @@ func (p *printer) printRawNode(n Node) {
 		}
 
 	case *BlockStmt:
-		p.printBody(n.Body)
+		p.print(_Lbrace)
+		if len(n.List) > 0 {
+			p.print(newline, indent)
+			p.printStmtList(n.List, true)
+			p.print(outdent, newline)
+		}
+		p.print(_Rbrace)
 
 	case *IfStmt:
 		p.print(_If, blank)
 		if n.Init != nil {
 			p.print(n.Init, _Semi, blank)
 		}
-		p.print(n.Cond, blank)
-		p.printBody(n.Then)
+		p.print(n.Cond, blank, n.Then)
 		if n.Else != nil {
 			p.print(blank, _Else, blank, n.Else)
 		}
@@ -578,8 +582,7 @@ func (p *printer) printRawNode(n Node) {
 				p.print(n.Init)
 				// TODO(gri) clean this up
 				if _, ok := n.Init.(*RangeClause); ok {
-					p.print(blank)
-					p.printBody(n.Body)
+					p.print(blank, n.Body)
 					break
 				}
 			}
@@ -592,7 +595,7 @@ func (p *printer) printRawNode(n Node) {
 				p.print(n.Post, blank)
 			}
 		}
-		p.printBody(n.Body)
+		p.print(n.Body)
 
 	case *ImportDecl:
 		if n.Group == nil {
@@ -650,8 +653,7 @@ func (p *printer) printRawNode(n Node) {
 		p.print(n.Name)
 		p.printSignature(n.Type)
 		if n.Body != nil {
-			p.print(blank)
-			p.printBody(n.Body)
+			p.print(blank, n.Body)
 		}
 
 	case *printGroup:
@@ -882,16 +884,6 @@ func (p *printer) printStmtList(list []Stmt, braces bool) {
 	}
 }
 
-func (p *printer) printBody(list []Stmt) {
-	p.print(_Lbrace)
-	if len(list) > 0 {
-		p.print(newline, indent)
-		p.printStmtList(list, true)
-		p.print(outdent, newline)
-	}
-	p.print(_Rbrace)
-}
-
 func (p *printer) printSwitchBody(list []*CaseClause) {
 	p.print(_Lbrace)
 	if len(list) > 0 {