Revert "cmd/compile: output DWARF lexical blocks for local variables"

This reverts commit c8b889cc.

Reason for revert: broke noopt build, compiler performance regression, new Curfn uses

Let's fix those and then try this again.

Change-Id: Icc3cad1365d04cac8fd09da9dbb0bbf55c13ef44
Reviewed-on: https://go-review.googlesource.com/39991Reviewed-by: Robert Griesemer <gri@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/cmd/compile/internal/gc/alg.go

@@ -6,7 +6,6 @@ package gc
 
 import (
 	"cmd/compile/internal/types"
-	"cmd/internal/src"
 	"fmt"
 )
 
@@ -192,7 +191,7 @@ func genhash(sym *types.Sym, t *types.Type) {
 
 	lineno = autogeneratedPos // less confusing than end of input
 	dclcontext = PEXTERN
-	markdcl(src.NoPos)
+	markdcl()
 
 	// func sym(p *T, h uintptr) uintptr
 	fn := nod(ODCLFUNC, nil, nil)
@@ -211,7 +210,7 @@ func genhash(sym *types.Sym, t *types.Type) {
 	n = anonfield(types.Types[TUINTPTR]) // return value
 	tfn.Rlist.Append(n)
 
-	funchdr(fn, src.NoPos)
+	funchdr(fn)
 	fn.Func.Nname.Name.Param.Ntype = typecheck(fn.Func.Nname.Name.Param.Ntype, Etype)
 
 	// genhash is only called for types that have equality but
@@ -300,13 +299,13 @@ func genhash(sym *types.Sym, t *types.Type) {
 		dumplist("genhash body", fn.Nbody)
 	}
 
-	funcbody(fn, src.NoPos)
+	funcbody(fn)
 	Curfn = fn
 	fn.Func.SetDupok(true)
 	fn = typecheck(fn, Etop)
 	typecheckslice(fn.Nbody.Slice(), Etop)
-	popdcl(src.NoPos)
 	Curfn = nil
+	popdcl()
 	if debug_dclstack != 0 {
 		testdclstack()
 	}
@@ -370,7 +369,7 @@ func geneq(sym *types.Sym, t *types.Type) {
 
 	lineno = autogeneratedPos // less confusing than end of input
 	dclcontext = PEXTERN
-	markdcl(src.NoPos)
+	markdcl()
 
 	// func sym(p, q *T) bool
 	fn := nod(ODCLFUNC, nil, nil)
@@ -389,7 +388,7 @@ func geneq(sym *types.Sym, t *types.Type) {
 	n = anonfield(types.Types[TBOOL])
 	tfn.Rlist.Append(n)
 
-	funchdr(fn, src.NoPos)
+	funchdr(fn)
 	fn.Func.Nname.Name.Param.Ntype = typecheck(fn.Func.Nname.Name.Param.Ntype, Etype)
 
 	// geneq is only called for types that have equality but
@@ -492,13 +491,13 @@ func geneq(sym *types.Sym, t *types.Type) {
 		dumplist("geneq body", fn.Nbody)
 	}
 
-	funcbody(fn, src.NoPos)
+	funcbody(fn)
 	Curfn = fn
 	fn.Func.SetDupok(true)
 	fn = typecheck(fn, Etop)
 	typecheckslice(fn.Nbody.Slice(), Etop)
-	popdcl(src.NoPos)
 	Curfn = nil
+	popdcl()
 	if debug_dclstack != 0 {
 		testdclstack()
 	}

src/cmd/compile/internal/gc/bimport.go

@@ -187,7 +187,7 @@ func Import(imp *types.Pkg, in *bufio.Reader) {
 
 		if f := p.funcList[i]; f != nil {
 			// function not yet imported - read body and set it
-			funchdr(f, src.NoPos)
+			funchdr(f)
 			body := p.stmtList()
 			if body == nil {
 				// Make sure empty body is not interpreted as
@@ -198,7 +198,7 @@ func Import(imp *types.Pkg, in *bufio.Reader) {
 				body = []*Node{nod(OEMPTY, nil, nil)}
 			}
 			f.Func.Inl.Set(body)
-			funcbody(f, src.NoPos)
+			funcbody(f)
 		} else {
 			// function already imported - read body but discard declarations
 			dclcontext = PDISCARD // throw away any declarations
@@ -1091,54 +1091,54 @@ func (p *importer) node() *Node {
 		return nodl(p.pos(), op, p.expr(), nil)
 
 	case OIF:
-		markdcl(src.NoPos)
+		markdcl()
 		n := nodl(p.pos(), OIF, nil, nil)
 		n.Ninit.Set(p.stmtList())
 		n.Left = p.expr()
 		n.Nbody.Set(p.stmtList())
 		n.Rlist.Set(p.stmtList())
-		popdcl(src.NoPos)
+		popdcl()
 		return n
 
 	case OFOR:
-		markdcl(src.NoPos)
+		markdcl()
 		n := nodl(p.pos(), OFOR, nil, nil)
 		n.Ninit.Set(p.stmtList())
 		n.Left, n.Right = p.exprsOrNil()
 		n.Nbody.Set(p.stmtList())
-		popdcl(src.NoPos)
+		popdcl()
 		return n
 
 	case ORANGE:
-		markdcl(src.NoPos)
+		markdcl()
 		n := nodl(p.pos(), ORANGE, nil, nil)
 		n.List.Set(p.stmtList())
 		n.Right = p.expr()
 		n.Nbody.Set(p.stmtList())
-		popdcl(src.NoPos)
+		popdcl()
 		return n
 
 	case OSELECT, OSWITCH:
-		markdcl(src.NoPos)
+		markdcl()
 		n := nodl(p.pos(), op, nil, nil)
 		n.Ninit.Set(p.stmtList())
 		n.Left, _ = p.exprsOrNil()
 		n.List.Set(p.stmtList())
-		popdcl(src.NoPos)
+		popdcl()
 		return n
 
 	// case OCASE, OXCASE:
 	// 	unreachable - mapped to OXCASE case below by exporter
 
 	case OXCASE:
-		markdcl(src.NoPos)
+		markdcl()
 		n := nodl(p.pos(), OXCASE, nil, nil)
 		n.Xoffset = int64(block)
 		n.List.Set(p.exprList())
 		// TODO(gri) eventually we must declare variables for type switch
 		// statements (type switch statements are not yet exported)
 		n.Nbody.Set(p.stmtList())
-		popdcl(src.NoPos)
+		popdcl()
 		return n
 
 	// case OFALL:

src/cmd/compile/internal/gc/closure.go

@@ -6,7 +6,6 @@ package gc
 
 import (
 	"cmd/compile/internal/types"
-	"cmd/internal/src"
 	"fmt"
 )
 
@@ -18,7 +17,7 @@ func closurehdr(ntype *Node) {
 	n.Func.Depth = funcdepth
 	n.Func.Outerfunc = Curfn
 
-	funchdr(n, src.NoPos)
+	funchdr(n)
 
 	// steal ntype's argument names and
 	// leave a fresh copy in their place.
@@ -59,7 +58,7 @@ func closurebody(body []*Node) *Node {
 	func_ := Curfn
 	func_.Nbody.Set(body)
 	func_.Func.Endlineno = lineno
-	funcbody(func_, src.NoPos)
+	funcbody(func_)
 
 	// closure-specific variables are hanging off the
 	// ordinary ones in the symbol table; see oldname.
@@ -227,10 +226,8 @@ func makeclosure(func_ *Node) *Node {
 	}
 
 	xfunc.Nbody.Set(func_.Nbody.Slice())
-	xfunc.Func.scopes = func_.Func.scopes
 	xfunc.Func.Dcl = append(func_.Func.Dcl, xfunc.Func.Dcl...)
 	func_.Func.Dcl = nil
-	func_.Func.scopes.Scopes = nil
 	if xfunc.Nbody.Len() == 0 {
 		Fatalf("empty body - won't generate any code")
 	}
@@ -612,7 +609,6 @@ func makepartialcall(fn *Node, t0 *types.Type, meth *types.Sym) *Node {
 	xfunc.Func.Nname.Sym.SetExported(true) // disable export
 	xfunc.Func.Nname.Name.Param.Ntype = xtype
 	xfunc.Func.Nname.Name.Defn = xfunc
-	xfunc.Func.scopes.Scopes = []src.Scope{src.Scope{}}
 	declare(xfunc.Func.Nname, PFUNC)
 
 	// Declare and initialize variable holding receiver.

src/cmd/compile/internal/gc/dcl.go

@@ -33,9 +33,6 @@ var block int32 // current block number
 // Sym definitions, and only a subset of its fields are actually used.
 var dclstack *types.Sym
 
-// lastPopdclPos is the last pos passed to popdcl
-var lastPopdclPos src.Pos
-
 func dcopy(a, b *types.Sym) {
 	a.Pkg = b.Pkg
 	a.Name = b.Name
@@ -62,7 +59,7 @@ func pushdcl(s *types.Sym) *types.Sym {
 
 // popdcl pops the innermost block scope and restores all symbol declarations
 // to their previous state.
-func popdcl(pos src.Pos) {
+func popdcl() {
 	d := dclstack
 	for ; d != nil && d.Name != ""; d = d.Link {
 		s := d.Pkg.Lookup(d.Name)
@@ -77,29 +74,16 @@ func popdcl(pos src.Pos) {
 
 	dclstack = d.Link // pop mark
 	block = d.Block
-
-	if Curfn != nil {
-		Curfn.Func.scopes.Close(&Ctxt.PosTable, pos)
-		lastPopdclPos = pos
-	}
-
-	return
 }
 
 // markdcl records the start of a new block scope for declarations.
-func markdcl(pos src.Pos) {
+func markdcl() {
 	d := push()
 	d.Name = "" // used as a mark in fifo
 	d.Block = block
 
 	blockgen++
 	block = blockgen
-
-	if Curfn != nil {
-		Curfn.Func.scopes.Open(&Ctxt.PosTable, pos)
-	}
-
-	return
 }
 
 // keep around for debugging
@@ -467,14 +451,14 @@ func ifacedcl(n *Node) {
 // and declare the arguments.
 // called in extern-declaration context
 // returns in auto-declaration context.
-func funchdr(n *Node, pos src.Pos) {
+func funchdr(n *Node) {
 	// change the declaration context from extern to auto
 	if funcdepth == 0 && dclcontext != PEXTERN {
 		Fatalf("funchdr: dclcontext = %d", dclcontext)
 	}
 
 	dclcontext = PAUTO
-	funcstart(n, pos)
+	funcstart(n)
 
 	if n.Func.Nname != nil {
 		funcargs(n.Func.Nname.Name.Param.Ntype)
@@ -612,22 +596,22 @@ var funcdepth int32   // len(funcstack) during parsing, but then forced to be th
 
 // start the function.
 // called before funcargs; undone at end of funcbody.
-func funcstart(n *Node, pos src.Pos) {
+func funcstart(n *Node) {
+	markdcl()
 	funcstack = append(funcstack, Curfn)
 	funcdepth++
 	Curfn = n
-	markdcl(pos)
 }
 
 // finish the body.
 // called in auto-declaration context.
 // returns in extern-declaration context.
-func funcbody(n *Node, pos src.Pos) {
+func funcbody(n *Node) {
 	// change the declaration context from auto to extern
 	if dclcontext != PAUTO {
 		Fatalf("funcbody: unexpected dclcontext %d", dclcontext)
 	}
-	popdcl(pos)
+	popdcl()
 	funcstack, Curfn = funcstack[:len(funcstack)-1], funcstack[len(funcstack)-1]
 	funcdepth--
 	if funcdepth == 0 {

src/cmd/compile/internal/gc/init.go

@@ -4,10 +4,7 @@
 
 package gc
 
-import (
-	"cmd/compile/internal/types"
-	"cmd/internal/src"
-)
+import "cmd/compile/internal/types"
 
 // a function named init is a special case.
 // it is called by the initialization before
@@ -95,7 +92,7 @@ func fninit(n []*Node) {
 	fn.Func.Nname.Name.Defn = fn
 	fn.Func.Nname.Name.Param.Ntype = nod(OTFUNC, nil, nil)
 	declare(fn.Func.Nname, PFUNC)
-	funchdr(fn, src.NoPos)
+	funchdr(fn)
 
 	// (3)
 	a := nod(OIF, nil, nil)
@@ -155,7 +152,7 @@ func fninit(n []*Node) {
 	exportsym(fn.Func.Nname)
 
 	fn.Nbody.Set(r)
-	funcbody(fn, src.NoPos)
+	funcbody(fn)
 
 	Curfn = fn
 	fn = typecheck(fn, Etop)

src/cmd/compile/internal/gc/noder.go

@@ -326,7 +326,7 @@ func (p *noder) funcDecl(fun *syntax.FuncDecl) *Node {
 		declare(f.Func.Nname, PFUNC)
 	}
 
-	funchdr(f, fun.Pos())
+	funchdr(f)
 
 	if fun.Body != nil {
 		if f.Noescape() {
@@ -347,7 +347,7 @@ func (p *noder) funcDecl(fun *syntax.FuncDecl) *Node {
 		}
 	}
 
-	funcbody(f, fun.Pos())
+	funcbody(f)
 
 	return f
 }
@@ -777,14 +777,14 @@ func (p *noder) stmt(stmt syntax.Stmt) *Node {
 }
 
 func (p *noder) blockStmt(stmt *syntax.BlockStmt) []*Node {
-	markdcl(stmt.Pos())
+	markdcl()
 	nodes := p.stmts(stmt.List)
-	popdcl(stmt.Rbrace)
+	popdcl()
 	return nodes
 }
 
 func (p *noder) ifStmt(stmt *syntax.IfStmt) *Node {
-	markdcl(stmt.Pos())
+	markdcl()
 	n := p.nod(stmt, OIF, nil, nil)
 	if stmt.Init != nil {
 		n.Ninit.Set1(p.stmt(stmt.Init))
@@ -801,12 +801,12 @@ func (p *noder) ifStmt(stmt *syntax.IfStmt) *Node {
 			n.Rlist.Set1(e)
 		}
 	}
-	popdcl(lastPopdclPos)
+	popdcl()
 	return n
 }
 
 func (p *noder) forStmt(stmt *syntax.ForStmt) *Node {
-	markdcl(stmt.Pos())
+	markdcl()
 	var n *Node
 	if r, ok := stmt.Init.(*syntax.RangeClause); ok {
 		if stmt.Cond != nil || stmt.Post != nil {
@@ -835,12 +835,12 @@ func (p *noder) forStmt(stmt *syntax.ForStmt) *Node {
 		}
 	}
 	n.Nbody.Set(p.blockStmt(stmt.Body))
-	popdcl(stmt.Body.Rbrace)
+	popdcl()
 	return n
 }
 
 func (p *noder) switchStmt(stmt *syntax.SwitchStmt) *Node {
-	markdcl(stmt.Pos())
+	markdcl()
 	n := p.nod(stmt, OSWITCH, nil, nil)
 	if stmt.Init != nil {
 		n.Ninit.Set1(p.stmt(stmt.Init))
@@ -854,17 +854,17 @@ func (p *noder) switchStmt(stmt *syntax.SwitchStmt) *Node {
 		tswitch = nil
 	}
 
-	n.List.Set(p.caseClauses(stmt.Body, tswitch, stmt.Rbrace))
+	n.List.Set(p.caseClauses(stmt.Body, tswitch))
 
-	popdcl(stmt.Rbrace)
+	popdcl()
 	return n
 }
 
-func (p *noder) caseClauses(clauses []*syntax.CaseClause, tswitch *Node, rbrace src.Pos) []*Node {
+func (p *noder) caseClauses(clauses []*syntax.CaseClause, tswitch *Node) []*Node {
 	var nodes []*Node
-	for i, clause := range clauses {
+	for _, clause := range clauses {
 		p.lineno(clause)
-		markdcl(clause.Pos())
+		markdcl()
 		n := p.nod(clause, OXCASE, nil, nil)
 		if clause.Cases != nil {
 			n.List.Set(p.exprList(clause.Cases))
@@ -878,11 +878,7 @@ func (p *noder) caseClauses(clauses []*syntax.CaseClause, tswitch *Node, rbrace
 		}
 		n.Xoffset = int64(block)
 		n.Nbody.Set(p.stmts(clause.Body))
-		if i+1 < len(clauses) {
-			popdcl(clauses[i+1].Pos())
-		} else {
-			popdcl(rbrace)
-		}
+		popdcl()
 		nodes = append(nodes, n)
 	}
 	return nodes
@@ -890,26 +886,22 @@ func (p *noder) caseClauses(clauses []*syntax.CaseClause, tswitch *Node, rbrace
 
 func (p *noder) selectStmt(stmt *syntax.SelectStmt) *Node {
 	n := p.nod(stmt, OSELECT, nil, nil)
-	n.List.Set(p.commClauses(stmt.Body, stmt.Rbrace))
+	n.List.Set(p.commClauses(stmt.Body))
 	return n
 }
 
-func (p *noder) commClauses(clauses []*syntax.CommClause, rbrace src.Pos) []*Node {
+func (p *noder) commClauses(clauses []*syntax.CommClause) []*Node {
 	var nodes []*Node
-	for i, clause := range clauses {
+	for _, clause := range clauses {
 		p.lineno(clause)
-		markdcl(clause.Pos())
+		markdcl()
 		n := p.nod(clause, OXCASE, nil, nil)
 		if clause.Comm != nil {
 			n.List.Set1(p.stmt(clause.Comm))
 		}
 		n.Xoffset = int64(block)
 		n.Nbody.Set(p.stmts(clause.Body))
-		if i+1 < len(clauses) {
-			popdcl(clauses[i+1].Pos())
-		} else {
-			popdcl(rbrace)
-		}
+		popdcl()
 		nodes = append(nodes, n)
 	}
 	return nodes

src/cmd/compile/internal/gc/pgen.go

@@ -310,18 +310,13 @@ func compile(fn *Node) {
 	pp.Free()
 }
 
-func debuginfo(fnsym *obj.LSym, curfn interface{}) []dwarf.Scope {
+func debuginfo(fnsym *obj.LSym, curfn interface{}) []*dwarf.Var {
 	fn := curfn.(*Node)
 	if expect := Linksym(fn.Func.Nname.Sym); fnsym != expect {
 		Fatalf("unexpected fnsym: %v != %v", fnsym, expect)
 	}
 
-	scopes := make([]dwarf.Scope, len(fn.Func.scopes.Scopes))
-
-	for i := range scopes {
-		scopes[i] = dwarf.Scope{Scope: fn.Func.scopes.Scopes[i]}
-	}
-
+	var vars []*dwarf.Var
 	for _, n := range fn.Func.Dcl {
 		if n.Op != ONAME { // might be OTYPE or OLITERAL
 			continue
@@ -368,14 +363,8 @@ func debuginfo(fnsym *obj.LSym, curfn interface{}) []dwarf.Scope {
 			continue
 		}
 
-		var scope int32 = 0
-		// Only record scope information when inlining is disabled.
-		if Debug['l'] == 0 {
-			scope = findScope(n.Pos, scopes)
-		}
-
 		typename := dwarf.InfoPrefix + gotype.Name[len("type."):]
-		scopes[scope].Vars = append(scopes[scope].Vars, &dwarf.Var{
+		vars = append(vars, &dwarf.Var{
 			Name:   n.Sym.Name,
 			Abbrev: abbrev,
 			Offset: int32(offs),
@@ -384,13 +373,9 @@ func debuginfo(fnsym *obj.LSym, curfn interface{}) []dwarf.Scope {
 	}
 
 	// Stable sort so that ties are broken with declaration order.
-	for i := range scopes {
-		sort.Stable(dwarf.VarsByOffset(scopes[i].Vars))
-	}
-
-	scopeRanges(fnsym, scopes)
+	sort.Stable(dwarf.VarsByOffset(vars))
 
-	return scopes
+	return vars
 }
 
 // fieldtrack adds R_USEFIELD relocations to fnsym to record any

src/cmd/compile/internal/gc/scope.go

-// Copyright 2017 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package gc
-
-import (
-	"cmd/internal/dwarf"
-	"cmd/internal/obj"
-	"cmd/internal/src"
-)
-
-// findScope returns the most specific scope containing pos.
-func findScope(pos src.XPos, scopes []dwarf.Scope) int32 {
-	if !pos.IsKnown() {
-		return 0
-	}
-	for i := len(scopes) - 1; i > 0; i-- {
-		if pos.After(scopes[i].Start) && pos.Before(scopes[i].End) {
-			return int32(i)
-		}
-	}
-	return 0
-}
-
-type scopedProg struct {
-	p     *obj.Prog
-	scope int32
-}
-
-// scopeRanges calculates scope ranges for symbol fnsym.
-func scopeRanges(fnsym *obj.LSym, scopes []dwarf.Scope) {
-	var sp []scopedProg
-
-	for p := fnsym.Text; p != nil; p = p.Link {
-		sp = append(sp, scopedProg{p, -1})
-	}
-
-	for scopeID := int32(len(scopes) - 1); scopeID >= 0; scopeID-- {
-		if scope := &scopes[scopeID]; scope.Start.IsKnown() && scope.End.IsKnown() {
-			scopeProgs(sp, scopeID, scope.Start, scope.End)
-		}
-	}
-
-	scopedProgsToRanges(sp, scopes, fnsym.Size)
-
-	// Propagate scope's pc ranges to parent
-	for i := len(scopes) - 1; i > 0; i-- {
-		cur := &scopes[i]
-		if scopes[i].Parent != 0 {
-			parent := &scopes[scopes[i].Parent]
-			parent.UnifyRanges(cur)
-		}
-	}
-}
-
-// scopeProgs marks all scopedProgs between start and end that don't already
-// belong to a scope as belonging to scopeId.
-func scopeProgs(sp []scopedProg, scopeId int32, start, end src.XPos) {
-	for i := range sp {
-		if sp[i].scope >= 0 {
-			continue
-		}
-		if pos := sp[i].p.Pos; pos.After(start) && pos.Before(end) {
-			sp[i].scope = scopeId
-		}
-	}
-}
-
-// scopedProgsToRanges scans sp and collects in the Ranges field of each
-// scope the start and end instruction of the scope.
-func scopedProgsToRanges(sp []scopedProg, scopes []dwarf.Scope, symSize int64) {
-	var curscope int32 = -1
-	for i := range sp {
-		if sp[i].scope == curscope {
-			continue
-		}
-		if curscope >= 0 {
-			curranges := scopes[curscope].Ranges
-			curranges[len(curranges)-1].End = sp[i].p.Pc
-		}
-		curscope = sp[i].scope
-		if curscope >= 0 {
-			scopes[curscope].Ranges = append(scopes[curscope].Ranges, dwarf.Range{Start: sp[i].p.Pc, End: -1})
-		}
-	}
-	if curscope >= 0 {
-		curranges := scopes[curscope].Ranges
-		curranges[len(curranges)-1].End = symSize
-	}
-}

src/cmd/compile/internal/gc/sizeof_test.go

@@ -22,7 +22,7 @@ func TestSizeof(t *testing.T) {
 		_32bit uintptr     // size on 32bit platforms
 		_64bit uintptr     // size on 64bit platforms
 	}{
-		{Func{}, 112, 192},
+		{Func{}, 96, 160},
 		{Name{}, 36, 56},
 		{Param{}, 28, 56},
 		{Node{}, 84, 136},

src/cmd/compile/internal/gc/subr.go

@@ -1687,7 +1687,7 @@ func genwrapper(rcvr *types.Type, method *types.Field, newnam *types.Sym, iface
 	lineno = autogeneratedPos
 
 	dclcontext = PEXTERN
-	markdcl(src.NoPos)
+	markdcl()
 
 	this := namedfield(".this", rcvr)
 	this.Left.Name.Param.Ntype = this.Right
@@ -1717,7 +1717,7 @@ func genwrapper(rcvr *types.Type, method *types.Field, newnam *types.Sym, iface
 	fn.Func.Nname.Name.Param.Ntype = t
 	fn.Func.Nname.Sym.SetExported(true) // prevent export; see closure.go
 	declare(fn.Func.Nname, PFUNC)
-	funchdr(fn, src.NoPos)
+	funchdr(fn)
 
 	// arg list
 	var args []*Node
@@ -1782,9 +1782,9 @@ func genwrapper(rcvr *types.Type, method *types.Field, newnam *types.Sym, iface
 		dumplist("genwrapper body", fn.Nbody)
 	}
 
-	funcbody(fn, src.NoPos)
+	funcbody(fn)
 	Curfn = fn
-	popdcl(src.NoPos)
+	popdcl()
 	if debug_dclstack != 0 {
 		testdclstack()
 	}

src/cmd/compile/internal/gc/syntax.go

@@ -321,10 +321,9 @@ type Func struct {
 	Shortname  *types.Sym
 	Enter      Nodes // for example, allocate and initialize memory for escaping parameters
 	Exit       Nodes
-	Cvars      Nodes      // closure params
-	Dcl        []*Node    // autodcl for this func/closure
-	Inldcl     Nodes      // copy of dcl for use in inlining
-	scopes     src.Scopes // lexical scopes of the function
+	Cvars      Nodes   // closure params
+	Dcl        []*Node // autodcl for this func/closure
+	Inldcl     Nodes   // copy of dcl for use in inlining
 	Closgen    int
 	Outerfunc  *Node // outer function (for closure)
 	FieldTrack map[*types.Sym]struct{}

src/cmd/compile/internal/gc/walk.go

@@ -7,7 +7,6 @@ package gc
 import (
 	"cmd/compile/internal/types"
 	"cmd/internal/obj"
-	"cmd/internal/src"
 	"cmd/internal/sys"
 	"fmt"
 	"strings"
@@ -3662,7 +3661,7 @@ func walkprintfunc(n *Node, init *Nodes) *Node {
 
 	oldfn := Curfn
 	Curfn = nil
-	funchdr(fn, src.NoPos)
+	funchdr(fn)
 
 	a = nod(n.Op, nil, nil)
 	a.List.Set(printargs)
@@ -3671,7 +3670,7 @@ func walkprintfunc(n *Node, init *Nodes) *Node {
 
 	fn.Nbody.Set1(a)
 
-	funcbody(fn, src.NoPos)
+	funcbody(fn)
 
 	fn = typecheck(fn, Etop)
 	typecheckslice(fn.Nbody.Slice(), Etop)

src/cmd/internal/dwarf/dwarf.go

@@ -8,20 +8,14 @@
 package dwarf
 
 import (
-	"cmd/internal/src"
-	"errors"
 	"fmt"
 )
 
 // InfoPrefix is the prefix for all the symbols containing DWARF info entries.
 const InfoPrefix = "go.info."
 
-// RangePrefix is the prefix for all the symbols containing DWARF range lists.
-const RangePrefix = "go.range."
-
 // Sym represents a symbol.
 type Sym interface {
-	Len() int64
 }
 
 // A Var represents a local variable or a function parameter.
@@ -32,63 +26,6 @@ type Var struct {
 	Type   Sym
 }
 
-// A Scope represents a lexical scope, all variables contained in a scope
-// will only be visible to instructions covered by the scope.
-// Lexical scopes are contiguous in source files but can end up being
-// compiled to discontiguous blocks of instructions in the executable, the
-// Ranges field lists all the blocks of instructions that belong in this
-// scope.
-type Scope struct {
-	src.Scope
-	Ranges []Range
-	Vars   []*Var
-}
-
-// A Range represents a half-open interval [Start, End).
-type Range struct {
-	Start, End int64
-}
-
-// UnifyRanges merges the list of ranges of c into the list of ranges of s
-func (s *Scope) UnifyRanges(c *Scope) {
-	out := make([]Range, 0, len(s.Ranges)+len(c.Ranges))
-
-	i, j := 0, 0
-	for {
-		var cur Range
-		if i < len(s.Ranges) && j < len(c.Ranges) {
-			if s.Ranges[i].Start < c.Ranges[j].Start {
-				cur = s.Ranges[i]
-				i++
-			} else {
-				cur = c.Ranges[j]
-				j++
-			}
-		} else if i < len(s.Ranges) {
-			cur = s.Ranges[i]
-			i++
-		} else if j < len(c.Ranges) {
-			cur = c.Ranges[j]
-			j++
-		} else {
-			break
-		}
-
-		if len(out) == 0 {
-			out = append(out, cur)
-		} else {
-			last := &out[len(out)-1]
-			if cur.Start > last.End {
-				out = append(out, cur)
-			} else if cur.End > last.End {
-				last.End = cur.End
-			}
-		}
-	}
-
-	s.Ranges = out
-}
-
 // A Context specifies how to add data to a Sym.
 type Context interface {
 	PtrSize() int
@@ -216,8 +153,6 @@ const (
 	DW_ABRV_VARIABLE
 	DW_ABRV_AUTO
 	DW_ABRV_PARAM
-	DW_ABRV_LEXICAL_BLOCK_RANGES
-	DW_ABRV_LEXICAL_BLOCK_SIMPLE
 	DW_ABRV_STRUCTFIELD
 	DW_ABRV_FUNCTYPEPARAM
 	DW_ABRV_DOTDOTDOT
@@ -308,25 +243,6 @@ var abbrevs = [DW_NABRV]dwAbbrev{
 		},
 	},
 
-	/* LEXICAL_BLOCK_RANGES */
-	{
-		DW_TAG_lexical_block,
-		DW_CHILDREN_yes,
-		[]dwAttrForm{
-			{DW_AT_ranges, DW_FORM_data4}, // replace with DW_FORM_sec_offset in DWARFv4.
-		},
-	},
-
-	/* LEXICAL_BLOCK_SIMPLE */
-	{
-		DW_TAG_lexical_block,
-		DW_CHILDREN_yes,
-		[]dwAttrForm{
-			{DW_AT_low_pc, DW_FORM_addr},
-			{DW_AT_high_pc, DW_FORM_addr},
-		},
-	},
-
 	/* STRUCTFIELD */
 	{
 		DW_TAG_member,
@@ -604,8 +520,8 @@ func putattr(ctxt Context, s Sym, abbrev int, form int, cls int, value int64, da
 		ctxt.AddInt(s, 2, value)
 
 	case DW_FORM_data4: // constant, {line,loclist,mac,rangelist}ptr
-		if cls == DW_CLS_PTR { // DW_AT_stmt_list and DW_AT_ranges
-			ctxt.AddSectionOffset(s, 4, data, value)
+		if cls == DW_CLS_PTR { // DW_AT_stmt_list
+			ctxt.AddSectionOffset(s, 4, data, 0)
 			break
 		}
 		ctxt.AddInt(s, 4, value)
@@ -634,13 +550,15 @@ func putattr(ctxt Context, s Sym, abbrev int, form int, cls int, value int64, da
 			ctxt.AddInt(s, 1, 0)
 		}
 
-	// In DWARF 3 the ref_addr is always 32 bits, unless emitting a large
+	// In DWARF 2 (which is what we claim to generate),
+	// the ref_addr is the same size as a normal address.
+	// In DWARF 3 it is always 32 bits, unless emitting a large
 	// (> 4 GB of debug info aka "64-bit") unit, which we don't implement.
 	case DW_FORM_ref_addr: // reference to a DIE in the .info section
 		if data == nil {
 			return fmt.Errorf("dwarf: null reference in %d", abbrev)
 		} else {
-			ctxt.AddSectionOffset(s, 4, data, 0)
+			ctxt.AddSectionOffset(s, ctxt.PtrSize(), data, 0)
 		}
 
 	case DW_FORM_ref1, // reference within the compilation unit
@@ -683,7 +601,7 @@ func HasChildren(die *DWDie) bool {
 
 // PutFunc writes a DIE for a function to s.
 // It also writes child DIEs for each variable in vars.
-func PutFunc(ctxt Context, s, ranges Sym, name string, external bool, startPC Sym, size int64, scopes []Scope) error {
+func PutFunc(ctxt Context, s Sym, name string, external bool, startPC Sym, size int64, vars []*Var) {
 	Uleb128put(ctxt, s, DW_ABRV_FUNCTION)
 	putattr(ctxt, s, DW_ABRV_FUNCTION, DW_FORM_string, DW_CLS_STRING, int64(len(name)), name)
 	putattr(ctxt, s, DW_ABRV_FUNCTION, DW_FORM_addr, DW_CLS_ADDRESS, 0, startPC)
@@ -693,72 +611,29 @@ func PutFunc(ctxt Context, s, ranges Sym, name string, external bool, startPC Sy
 		ev = 1
 	}
 	putattr(ctxt, s, DW_ABRV_FUNCTION, DW_FORM_flag, DW_CLS_FLAG, ev, 0)
-	if len(scopes) > 0 {
-		var encbuf [20]byte
-		if putscope(ctxt, s, ranges, startPC, 0, scopes, encbuf[:0]) < int32(len(scopes)) {
-			return errors.New("multiple toplevel scopes")
-		}
-	}
-
-	Uleb128put(ctxt, s, 0)
-	return nil
-}
-
-func putvar(ctxt Context, s Sym, v *Var, encbuf []byte) {
-	n := v.Name
-
-	Uleb128put(ctxt, s, int64(v.Abbrev))
-	putattr(ctxt, s, v.Abbrev, DW_FORM_string, DW_CLS_STRING, int64(len(n)), n)
-	loc := append(encbuf[:0], DW_OP_call_frame_cfa)
-	if v.Offset != 0 {
-		loc = append(loc, DW_OP_consts)
-		loc = AppendSleb128(loc, int64(v.Offset))
-		loc = append(loc, DW_OP_plus)
-	}
-	putattr(ctxt, s, v.Abbrev, DW_FORM_block1, DW_CLS_BLOCK, int64(len(loc)), loc)
-	putattr(ctxt, s, v.Abbrev, DW_FORM_ref_addr, DW_CLS_REFERENCE, 0, v.Type)
-}
-
-func putscope(ctxt Context, s, ranges Sym, startPC Sym, curscope int32, scopes []Scope, encbuf []byte) int32 {
-	for _, v := range scopes[curscope].Vars {
-		putvar(ctxt, s, v, encbuf)
-	}
-	this := curscope
-	curscope++
-	for curscope < int32(len(scopes)) {
-		scope := scopes[curscope]
-		if scope.Parent != this {
-			return curscope
-		}
-
-		emptyscope := len(scope.Vars) == 0 || len(scope.Ranges) == 0
-
-		if !emptyscope {
-			if len(scope.Ranges) == 1 {
-				Uleb128put(ctxt, s, DW_ABRV_LEXICAL_BLOCK_SIMPLE)
-				putattr(ctxt, s, DW_ABRV_LEXICAL_BLOCK_SIMPLE, DW_FORM_addr, DW_CLS_ADDRESS, scope.Ranges[0].Start, startPC)
-				putattr(ctxt, s, DW_ABRV_LEXICAL_BLOCK_SIMPLE, DW_FORM_addr, DW_CLS_ADDRESS, scope.Ranges[0].End, startPC)
-			} else {
-				Uleb128put(ctxt, s, DW_ABRV_LEXICAL_BLOCK_RANGES)
-				putattr(ctxt, s, DW_ABRV_LEXICAL_BLOCK_RANGES, DW_FORM_data4, DW_CLS_PTR, ranges.Len(), ranges)
-				ctxt.AddAddress(ranges, nil, -1)
-				ctxt.AddAddress(ranges, startPC, 0)
-				for _, pcrange := range scope.Ranges {
-					ctxt.AddAddress(ranges, nil, pcrange.Start)
-					ctxt.AddAddress(ranges, nil, pcrange.End)
-				}
-				ctxt.AddAddress(ranges, nil, 0)
-				ctxt.AddAddress(ranges, nil, 0)
-			}
+	names := make(map[string]bool)
+	var encbuf [20]byte
+	for _, v := range vars {
+		var n string
+		if names[v.Name] {
+			n = fmt.Sprintf("%s#%d", v.Name, len(names))
+		} else {
+			n = v.Name
 		}
-
-		curscope = putscope(ctxt, s, ranges, startPC, curscope, scopes, encbuf)
-
-		if !emptyscope {
-			Uleb128put(ctxt, s, 0)
+		names[n] = true
+
+		Uleb128put(ctxt, s, int64(v.Abbrev))
+		putattr(ctxt, s, v.Abbrev, DW_FORM_string, DW_CLS_STRING, int64(len(n)), n)
+		loc := append(encbuf[:0], DW_OP_call_frame_cfa)
+		if v.Offset != 0 {
+			loc = append(loc, DW_OP_consts)
+			loc = AppendSleb128(loc, int64(v.Offset))
+			loc = append(loc, DW_OP_plus)
 		}
+		putattr(ctxt, s, v.Abbrev, DW_FORM_block1, DW_CLS_BLOCK, int64(len(loc)), loc)
+		putattr(ctxt, s, v.Abbrev, DW_FORM_ref_addr, DW_CLS_REFERENCE, 0, v.Type)
 	}
-	return curscope
+	Uleb128put(ctxt, s, 0)
 }
 
 // VarsByOffset attaches the methods of sort.Interface to []*Var,

src/cmd/internal/obj/data.go

@@ -114,7 +114,7 @@ func (s *LSym) WriteInt(ctxt *Link, off int64, siz int, i int64) {
 // WriteAddr writes an address of size siz into s at offset off.
 // rsym and roff specify the relocation for the address.
 func (s *LSym) WriteAddr(ctxt *Link, off int64, siz int, rsym *LSym, roff int64) {
-	if siz != ctxt.Arch.PtrSize && siz != 4 {
+	if siz != ctxt.Arch.PtrSize {
 		ctxt.Diag("WriteAddr: bad address size %d in %s", siz, s.Name)
 	}
 	s.prepwrite(ctxt, off, siz)

src/cmd/internal/obj/link.go

@@ -483,7 +483,6 @@ const (
 	SHOSTOBJ
 	SDWARFSECT
 	SDWARFINFO
-	SDWARFRANGE
 	SSUB       = SymKind(1 << 8)
 	SMASK      = SymKind(SSUB - 1)
 	SHIDDEN    = SymKind(1 << 9)
@@ -740,7 +739,7 @@ type Link struct {
 	Armsize       int32
 	Pc            int64
 	DiagFunc      func(string, ...interface{})
-	DebugInfo     func(fn *LSym, curfn interface{}) []dwarf.Scope // if non-nil, curfn is a *gc.Node
+	DebugInfo     func(fn *LSym, curfn interface{}) []*dwarf.Var // if non-nil, curfn is a *gc.Node
 	Cursym        *LSym
 	Version       int
 	Errors        int

src/cmd/internal/obj/objfile.go

@@ -542,14 +542,10 @@ func (c dwCtxt) SymValue(s dwarf.Sym) int64 {
 	return 0
 }
 func (c dwCtxt) AddAddress(s dwarf.Sym, data interface{}, value int64) {
+	rsym := data.(*LSym)
 	ls := s.(*LSym)
 	size := c.PtrSize()
-	if data != nil {
-		rsym := data.(*LSym)
-		ls.WriteAddr(c.Link, ls.Size, size, rsym, value)
-	} else {
-		ls.WriteInt(c.Link, ls.Size, size, value)
-	}
+	ls.WriteAddr(c.Link, ls.Size, size, rsym, value)
 }
 func (c dwCtxt) AddSectionOffset(s dwarf.Sym, size int, t interface{}, ofs int64) {
 	ls := s.(*LSym)
@@ -559,10 +555,6 @@ func (c dwCtxt) AddSectionOffset(s dwarf.Sym, size int, t interface{}, ofs int64
 	r.Type = R_DWARFREF
 }
 
-func (s *LSym) Len() int64 {
-	return s.Size
-}
-
 // makeFuncDebugEntry makes a DWARF Debugging Information Entry
 // for TEXT symbol s.
 func makeFuncDebugEntry(ctxt *Link, curfn interface{}, s *LSym) {
@@ -572,21 +564,10 @@ func makeFuncDebugEntry(ctxt *Link, curfn interface{}, s *LSym) {
 	}
 	dsym.Type = SDWARFINFO
 	dsym.Set(AttrDuplicateOK, s.DuplicateOK())
-
-	drsym := ctxt.Lookup(dwarf.RangePrefix+s.Name, int(s.Version))
-	if drsym.Size != 0 {
-		return
-	}
-	drsym.Type = SDWARFRANGE
-	drsym.Set(AttrDuplicateOK, s.DuplicateOK())
-
-	var scopes []dwarf.Scope
+	var vars []*dwarf.Var
 	if ctxt.DebugInfo != nil {
-		scopes = ctxt.DebugInfo(s, curfn)
-	}
-	err := dwarf.PutFunc(dwCtxt{ctxt}, dsym, drsym, s.Name, s.Version == 0, s, s.Size, scopes)
-	if err != nil {
-		ctxt.Diag("emitting DWARF for %s failed: %v", s.Name, err)
+		vars = ctxt.DebugInfo(s, curfn)
 	}
-	ctxt.Data = append(ctxt.Data, dsym, drsym)
+	dwarf.PutFunc(dwCtxt{ctxt}, dsym, s.Name, s.Version == 0, s, s.Size, vars)
+	ctxt.Data = append(ctxt.Data, dsym)
 }

src/cmd/internal/src/scope.go

-// Copyright 2017 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package src
-
-// Scope represents a lexical scope.
-type Scope struct {
-	Start, End XPos
-	Parent     int32
-}
-
-// Scopes represents a tree of lexical scopes
-type Scopes struct {
-	Scopes   []Scope // lexical scopes
-	curscope int32   // current scope index (during noding)
-}
-
-// Open starts a new scope, scopes.Curscope is the parent.
-func (scopes *Scopes) Open(posTable *PosTable, pos Pos) {
-	scope := Scope{Parent: scopes.curscope, Start: NoXPos, End: NoXPos}
-	if pos.IsKnown() {
-		scope.Start = posTable.XPos(pos)
-	}
-	scopes.Scopes = append(scopes.Scopes, scope)
-	scopes.curscope = int32(len(scopes.Scopes) - 1)
-}
-
-// Close ends the current scope.
-func (scopes *Scopes) Close(posTable *PosTable, pos Pos) {
-	scope := &scopes.Scopes[scopes.curscope]
-	if pos.IsKnown() {
-		scope.End = posTable.XPos(pos)
-	}
-	scopes.curscope = scope.Parent
-}

src/cmd/link/internal/ld/data.go

@@ -570,18 +570,9 @@ func relocsym(ctxt *Link, s *Symbol) {
 			}
 
 		case obj.R_DWARFREF:
-			sectName := ""
-			vaddr := int64(0)
-			if r.Sym.Sect != nil {
-				sectName = r.Sym.Sect.Name
-				vaddr = int64(r.Sym.Sect.Vaddr)
-			} else if r.Sym.Type == obj.SDWARFRANGE {
-				sectName = ".debug_ranges"
-				vaddr = 0
-			} else {
+			if r.Sym.Sect == nil {
 				Errorf(s, "missing DWARF section for relocation target %s", r.Sym.Name)
 			}
-
 			if Linkmode == LinkExternal {
 				r.Done = 0
 				// PE code emits IMAGE_REL_I386_SECREL and IMAGE_REL_AMD64_SECREL
@@ -593,9 +584,8 @@ func relocsym(ctxt *Link, s *Symbol) {
 					r.Type = obj.R_ADDR
 				}
 
-				r.Xsym = ctxt.Syms.ROLookup(sectName, 0)
-				r.Xadd = r.Add + Symaddr(r.Sym) - vaddr
-
+				r.Xsym = ctxt.Syms.ROLookup(r.Sym.Sect.Name, 0)
+				r.Xadd = r.Add + Symaddr(r.Sym) - int64(r.Sym.Sect.Vaddr)
 				o = r.Xadd
 				rs = r.Xsym
 				if Iself && SysArch.Family == sys.AMD64 {
@@ -603,7 +593,7 @@ func relocsym(ctxt *Link, s *Symbol) {
 				}
 				break
 			}
-			o = Symaddr(r.Sym) + r.Add - vaddr
+			o = Symaddr(r.Sym) + r.Add - int64(r.Sym.Sect.Vaddr)
 
 		case obj.R_WEAKADDROFF:
 			if !r.Sym.Attr.Reachable() {
@@ -1832,7 +1822,6 @@ func (ctxt *Link) dodata() {
 		if s.Type != obj.SDWARFSECT {
 			break
 		}
-
 		sect = addsection(&Segdwarf, s.Name, 04)
 		sect.Align = 1
 		datsize = Rnd(datsize, int64(sect.Align))

src/cmd/link/internal/ld/dwarf.go

@@ -8,6 +8,7 @@
 //   - assign global variables and types to their packages
 //   - gdb uses c syntax, meaning clumsy quoting is needed for go identifiers. eg
 //     ptype struct '[]uint8' and qualifiers need to be quoted away
+//   - lexical scoping is lost, so gdb gets confused as to which 'main.i' you mean.
 //   - file:line info for variables
 //   - make strings a typedef so prettyprinters can see the underlying string type
 
@@ -75,7 +76,6 @@ var arangessec *Symbol
 var framesec *Symbol
 var infosec *Symbol
 var linesec *Symbol
-var rangesec *Symbol
 
 var gdbscript string
 
@@ -1288,34 +1288,6 @@ func writeframes(ctxt *Link, syms []*Symbol) []*Symbol {
 	return syms
 }
 
-func writeranges(ctxt *Link, syms []*Symbol) []*Symbol {
-	if rangesec == nil {
-		rangesec = ctxt.Syms.Lookup(".debug_ranges", 0)
-	}
-	rangesec.Type = obj.SDWARFSECT
-	rangesec.Attr |= AttrReachable
-	rangesec.R = rangesec.R[:0]
-
-	for _, s := range ctxt.Textp {
-		rangeSym := ctxt.Syms.Lookup(dwarf.RangePrefix+s.Name, int(s.Version))
-		rangeSym.Attr |= AttrHidden
-		rangeSym.Attr |= AttrReachable
-		rangeSym.Type = obj.SDWARFRANGE
-		rangeSym.Value = rangesec.Size
-		rangesec.P = append(rangesec.P, rangeSym.P...)
-		for _, r := range rangeSym.R {
-			r.Off += int32(rangesec.Size)
-			rangesec.R = append(rangesec.R, r)
-		}
-		rangesec.Size += rangeSym.Size
-	}
-	if rangesec.Size > 0 {
-		// PE does not like empty sections
-		syms = append(syms, rangesec)
-	}
-	return syms
-}
-
 /*
  *  Walk DWarfDebugInfoEntries, and emit .debug_info
  */
@@ -1346,7 +1318,7 @@ func writeinfo(ctxt *Link, syms []*Symbol, funcs []*Symbol) []*Symbol {
 		// Fields marked with (*) must be changed for 64-bit dwarf
 		// This must match COMPUNITHEADERSIZE above.
 		Adduint32(ctxt, s, 0) // unit_length (*), will be filled in later.
-		Adduint16(ctxt, s, 3) // dwarf version (appendix F)
+		Adduint16(ctxt, s, 2) // dwarf version (appendix F)
 
 		// debug_abbrev_offset (*)
 		adddwarfref(ctxt, s, abbrevsym, 4)
@@ -1559,7 +1531,6 @@ func dwarfgeneratedebugsyms(ctxt *Link) {
 	syms := writeabbrev(ctxt, nil)
 	syms, funcs := writelines(ctxt, syms)
 	syms = writeframes(ctxt, syms)
-	syms = writeranges(ctxt, syms)
 
 	synthesizestringtypes(ctxt, dwtypes.Child)
 	synthesizeslicetypes(ctxt, dwtypes.Child)
@@ -1601,7 +1572,6 @@ func dwarfaddshstrings(ctxt *Link, shstrtab *Symbol) {
 	Addstring(shstrtab, ".debug_pubnames")
 	Addstring(shstrtab, ".debug_pubtypes")
 	Addstring(shstrtab, ".debug_gdb_scripts")
-	Addstring(shstrtab, ".debug_ranges")
 	if Linkmode == LinkExternal {
 		Addstring(shstrtab, elfRelType+".debug_info")
 		Addstring(shstrtab, elfRelType+".debug_aranges")
@@ -1629,10 +1599,6 @@ func dwarfaddelfsectionsyms(ctxt *Link) {
 	putelfsectionsym(sym, sym.Sect.Elfsect.shnum)
 	sym = ctxt.Syms.Lookup(".debug_frame", 0)
 	putelfsectionsym(sym, sym.Sect.Elfsect.shnum)
-	sym = ctxt.Syms.Lookup(".debug_ranges", 0)
-	if sym.Sect != nil {
-		putelfsectionsym(sym, sym.Sect.Elfsect.shnum)
-	}
 }
 
 /*

src/cmd/link/internal/ld/link.go

@@ -89,10 +89,6 @@ func (s *Symbol) ElfsymForReloc() int32 {
 	}
 }
 
-func (s *Symbol) Len() int64 {
-	return s.Size
-}
-
 // Attribute is a set of common symbol attributes.
 type Attribute int16