cmd/compile: output DWARF lexical blocks for local variables

Change compiler and linker to emit DWARF lexical blocks in debug_info.
Version of debug_info is updated from DWARF v.2 to DWARF v.3 since version 2
does not allow lexical blocks with discontinuous ranges.

Second attempt at https://go-review.googlesource.com/#/c/29591/

Remaining open problems:
- scope information is removed from inlined functions
- variables in debug_info do not have DW_AT_start_scope attributes so a
variable will shadow other variables with the same name as soon as its
containing scope begins, before its declaration.

Updates golang/go#12899, golang/go#6913

Change-Id: I0e260a45b564d14a87b88974eb16c5387cb410a5
Reviewed-on: https://go-review.googlesource.com/36879
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 28 insertions, 20 deletions

diff --git a/src/cmd/compile/internal/gc/noder.go b/src/cmd/compile/internal/gc/noder.go
index bd769b6126..61a338d214 100644
--- a/src/cmd/compile/internal/gc/noder.go
+++ b/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)
+	funchdr(f, fun.Pos())
 
 	if fun.Body != nil {
 		if f.Noescape() {
@@ -347,7 +347,7 @@ func (p *noder) funcDecl(fun *syntax.FuncDecl) *Node {
 		}
 	}
 
-	funcbody(f)
+	funcbody(f, fun.Pos())
 
 	return f
 }
@@ -777,14 +777,14 @@ func (p *noder) stmt(stmt syntax.Stmt) *Node {
 }
 
 func (p *noder) blockStmt(stmt *syntax.BlockStmt) []*Node {
-	markdcl()
+	markdcl(stmt.Pos())
 	nodes := p.stmts(stmt.List)
-	popdcl()
+	popdcl(stmt.Rbrace)
 	return nodes
 }
 
 func (p *noder) ifStmt(stmt *syntax.IfStmt) *Node {
-	markdcl()
+	markdcl(stmt.Pos())
 	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()
+	popdcl(lastPopdclPos)
 	return n
 }
 
 func (p *noder) forStmt(stmt *syntax.ForStmt) *Node {
-	markdcl()
+	markdcl(stmt.Pos())
 	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()
+	popdcl(stmt.Body.Rbrace)
 	return n
 }
 
 func (p *noder) switchStmt(stmt *syntax.SwitchStmt) *Node {
-	markdcl()
+	markdcl(stmt.Pos())
 	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))
+	n.List.Set(p.caseClauses(stmt.Body, tswitch, stmt.Rbrace))
 
-	popdcl()
+	popdcl(stmt.Rbrace)
 	return n
 }
 
-func (p *noder) caseClauses(clauses []*syntax.CaseClause, tswitch *Node) []*Node {
+func (p *noder) caseClauses(clauses []*syntax.CaseClause, tswitch *Node, rbrace src.Pos) []*Node {
 	var nodes []*Node
-	for _, clause := range clauses {
+	for i, clause := range clauses {
 		p.lineno(clause)
-		markdcl()
+		markdcl(clause.Pos())
 		n := p.nod(clause, OXCASE, nil, nil)
 		if clause.Cases != nil {
 			n.List.Set(p.exprList(clause.Cases))
@@ -878,7 +878,11 @@ func (p *noder) caseClauses(clauses []*syntax.CaseClause, tswitch *Node) []*Node
 		}
 		n.Xoffset = int64(block)
 		n.Nbody.Set(p.stmts(clause.Body))
-		popdcl()
+		if i+1 < len(clauses) {
+			popdcl(clauses[i+1].Pos())
+		} else {
+			popdcl(rbrace)
+		}
 		nodes = append(nodes, n)
 	}
 	return nodes
@@ -886,22 +890,26 @@ func (p *noder) caseClauses(clauses []*syntax.CaseClause, tswitch *Node) []*Node
 
 func (p *noder) selectStmt(stmt *syntax.SelectStmt) *Node {
 	n := p.nod(stmt, OSELECT, nil, nil)
-	n.List.Set(p.commClauses(stmt.Body))
+	n.List.Set(p.commClauses(stmt.Body, stmt.Rbrace))
 	return n
 }
 
-func (p *noder) commClauses(clauses []*syntax.CommClause) []*Node {
+func (p *noder) commClauses(clauses []*syntax.CommClause, rbrace src.Pos) []*Node {
 	var nodes []*Node
-	for _, clause := range clauses {
+	for i, clause := range clauses {
 		p.lineno(clause)
-		markdcl()
+		markdcl(clause.Pos())
 		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))
-		popdcl()
+		if i+1 < len(clauses) {
+			popdcl(clauses[i+1].Pos())
+		} else {
+			popdcl(rbrace)
+		}
 		nodes = append(nodes, n)
 	}
 	return nodes