diff --git a/src/cmd/asm/main.go b/src/cmd/asm/main.go
index 55ae94a6de5..447d1afde3a 100644
--- a/src/cmd/asm/main.go
+++ b/src/cmd/asm/main.go
@@ -36,7 +36,7 @@ func main() {
 
 	ctxt := obj.Linknew(architecture.LinkArch)
 	if *flags.PrintOut {
-		ctxt.Debugasm = true
+		ctxt.Debugasm = 1
 	}
 	ctxt.Flag_dynlink = *flags.Dynlink
 	ctxt.Flag_shared = *flags.Shared || *flags.Dynlink
diff --git a/src/cmd/compile/internal/gc/global_test.go b/src/cmd/compile/internal/gc/global_test.go
index 857cf967502..56855d797a1 100644
--- a/src/cmd/compile/internal/gc/global_test.go
+++ b/src/cmd/compile/internal/gc/global_test.go
@@ -8,7 +8,6 @@ import (
 	"bytes"
 	"internal/testenv"
 	"io/ioutil"
-	"log"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -24,7 +23,7 @@ func TestScanfRemoval(t *testing.T) {
 	// Make a directory to work in.
 	dir, err := ioutil.TempDir("", "issue6853a-")
 	if err != nil {
-		log.Fatalf("could not create directory: %v", err)
+		t.Fatalf("could not create directory: %v", err)
 	}
 	defer os.RemoveAll(dir)
 
@@ -32,7 +31,7 @@ func TestScanfRemoval(t *testing.T) {
 	src := filepath.Join(dir, "test.go")
 	f, err := os.Create(src)
 	if err != nil {
-		log.Fatalf("could not create source file: %v", err)
+		t.Fatalf("could not create source file: %v", err)
 	}
 	f.Write([]byte(`
 package main
@@ -50,17 +49,17 @@ func main() {
 	cmd := exec.Command(testenv.GoToolPath(t), "build", "-o", dst, src)
 	out, err := cmd.CombinedOutput()
 	if err != nil {
-		log.Fatalf("could not build target: %v", err)
+		t.Fatalf("could not build target: %v", err)
 	}
 
 	// Check destination to see if scanf code was included.
 	cmd = exec.Command(testenv.GoToolPath(t), "tool", "nm", dst)
 	out, err = cmd.CombinedOutput()
 	if err != nil {
-		log.Fatalf("could not read target: %v", err)
+		t.Fatalf("could not read target: %v", err)
 	}
 	if bytes.Contains(out, []byte("scanInt")) {
-		log.Fatalf("scanf code not removed from helloworld")
+		t.Fatalf("scanf code not removed from helloworld")
 	}
 }
 
@@ -71,7 +70,7 @@ func TestDashS(t *testing.T) {
 	// Make a directory to work in.
 	dir, err := ioutil.TempDir("", "issue14515-")
 	if err != nil {
-		log.Fatalf("could not create directory: %v", err)
+		t.Fatalf("could not create directory: %v", err)
 	}
 	defer os.RemoveAll(dir)
 
@@ -79,7 +78,7 @@ func TestDashS(t *testing.T) {
 	src := filepath.Join(dir, "test.go")
 	f, err := os.Create(src)
 	if err != nil {
-		log.Fatalf("could not create source file: %v", err)
+		t.Fatalf("could not create source file: %v", err)
 	}
 	f.Write([]byte(`
 package main
@@ -94,7 +93,7 @@ func main() {
 	cmd := exec.Command(testenv.GoToolPath(t), "build", "-gcflags", "-S", "-o", filepath.Join(dir, "test"), src)
 	out, err := cmd.CombinedOutput()
 	if err != nil {
-		log.Fatalf("could not build target: %v", err)
+		t.Fatalf("could not build target: %v", err)
 	}
 
 	patterns := []string{
diff --git a/src/cmd/compile/internal/gc/main.go b/src/cmd/compile/internal/gc/main.go
index adfdd7cb376..f44d19b4390 100644
--- a/src/cmd/compile/internal/gc/main.go
+++ b/src/cmd/compile/internal/gc/main.go
@@ -39,7 +39,6 @@ var (
 
 var (
 	Debug_append       int
-	Debug_asm          bool
 	Debug_closure      int
 	Debug_compilelater int
 	debug_dclstack     int
@@ -195,7 +194,7 @@ func Main(archInit func(*Arch)) {
 	objabi.Flagcount("K", "debug missing line numbers", &Debug['K'])
 	objabi.Flagcount("L", "show full file names in error messages", &Debug['L'])
 	objabi.Flagcount("N", "disable optimizations", &Debug['N'])
-	flag.BoolVar(&Debug_asm, "S", false, "print assembly listing")
+	objabi.Flagcount("S", "print assembly listing", &Debug['S'])
 	objabi.AddVersionFlag() // -V
 	objabi.Flagcount("W", "debug parse tree after type checking", &Debug['W'])
 	flag.StringVar(&asmhdr, "asmhdr", "", "write assembly header to `file`")
@@ -265,7 +264,7 @@ func Main(archInit func(*Arch)) {
 	Ctxt.Flag_dynlink = flag_dynlink
 	Ctxt.Flag_optimize = Debug['N'] == 0
 
-	Ctxt.Debugasm = Debug_asm
+	Ctxt.Debugasm = Debug['S']
 	Ctxt.Debugvlog = Debug_vlog
 	if flagDWARF {
 		Ctxt.DebugInfo = debuginfo
@@ -1330,6 +1329,7 @@ var concurrentFlagOK = [256]bool{
 	'l': true, // disable inlining
 	'w': true, // all printing happens before compilation
 	'W': true, // all printing happens before compilation
+	'S': true, // printing disassembly happens at the end (but see concurrentBackendAllowed below)
 }
 
 func concurrentBackendAllowed() bool {
@@ -1338,9 +1338,9 @@ func concurrentBackendAllowed() bool {
 			return false
 		}
 	}
-	// Debug_asm by itself is ok, because all printing occurs
+	// Debug['S'] by itself is ok, because all printing occurs
 	// while writing the object file, and that is non-concurrent.
-	// Adding Debug_vlog, however, causes Debug_asm to also print
+	// Adding Debug_vlog, however, causes Debug['S'] to also print
 	// while flushing the plist, which happens concurrently.
 	if Debug_vlog || debugstr != "" || debuglive > 0 {
 		return false
diff --git a/src/cmd/internal/obj/link.go b/src/cmd/internal/obj/link.go
index 6cff335ddfa..dfecdfbb379 100644
--- a/src/cmd/internal/obj/link.go
+++ b/src/cmd/internal/obj/link.go
@@ -599,7 +599,7 @@ type Pcdata struct {
 type Link struct {
 	Headtype           objabi.HeadType
 	Arch               *LinkArch
-	Debugasm           bool
+	Debugasm           int
 	Debugvlog          bool
 	Debugpcln          string
 	Flag_shared        bool
diff --git a/src/cmd/internal/obj/objfile.go b/src/cmd/internal/obj/objfile.go
index 4fbaafe3474..49301f04d50 100644
--- a/src/cmd/internal/obj/objfile.go
+++ b/src/cmd/internal/obj/objfile.go
@@ -240,7 +240,13 @@ func (w *objWriter) writeSymDebug(s *LSym) {
 	fmt.Fprintf(ctxt.Bso, "\n")
 	if s.Type == objabi.STEXT {
 		for p := s.Func.Text; p != nil; p = p.Link {
-			fmt.Fprintf(ctxt.Bso, "\t%#04x %v\n", uint(int(p.Pc)), p)
+			var s string
+			if ctxt.Debugasm > 1 {
+				s = p.String()
+			} else {
+				s = p.InnermostString()
+			}
+			fmt.Fprintf(ctxt.Bso, "\t%#04x %s\n", uint(int(p.Pc)), s)
 		}
 	}
 	for i := 0; i < len(s.P); i += 16 {
@@ -283,7 +289,7 @@ func (w *objWriter) writeSymDebug(s *LSym) {
 
 func (w *objWriter) writeSym(s *LSym) {
 	ctxt := w.ctxt
-	if ctxt.Debugasm {
+	if ctxt.Debugasm > 0 {
 		w.writeSymDebug(s)
 	}
 
diff --git a/src/cmd/internal/obj/plist.go b/src/cmd/internal/obj/plist.go
index 6710b375f16..9d376f739ff 100644
--- a/src/cmd/internal/obj/plist.go
+++ b/src/cmd/internal/obj/plist.go
@@ -27,7 +27,7 @@ func Flushplist(ctxt *Link, plist *Plist, newprog ProgAlloc, myimportpath string
 
 	var plink *Prog
 	for p := plist.Firstpc; p != nil; p = plink {
-		if ctxt.Debugasm && ctxt.Debugvlog {
+		if ctxt.Debugasm > 0 && ctxt.Debugvlog {
 			fmt.Printf("obj: %v\n", p)
 		}
 		plink = p.Link
diff --git a/src/cmd/internal/obj/util.go b/src/cmd/internal/obj/util.go
index 46c3d7b17bb..f1517d3d5d1 100644
--- a/src/cmd/internal/obj/util.go
+++ b/src/cmd/internal/obj/util.go
@@ -17,6 +17,9 @@ const REG_NONE = 0
 func (p *Prog) Line() string {
 	return p.Ctxt.OutermostPos(p.Pos).Format(false, true)
 }
+func (p *Prog) InnermostLine() string {
+	return p.Ctxt.InnermostPos(p.Pos).Format(false, true)
+}
 
 // InnermostLineNumber returns a string containing the line number for the
 // innermost inlined function (if any inlining) at p's position
@@ -118,6 +121,16 @@ func (p *Prog) String() string {
 	return fmt.Sprintf("%.5d (%v)\t%s", p.Pc, p.Line(), p.InstructionString())
 }
 
+func (p *Prog) InnermostString() string {
+	if p == nil {
+		return "<nil Prog>"
+	}
+	if p.Ctxt == nil {
+		return "<Prog without ctxt>"
+	}
+	return fmt.Sprintf("%.5d (%v)\t%s", p.Pc, p.InnermostLine(), p.InstructionString())
+}
+
 // InstructionString returns a string representation of the instruction without preceding
 // program counter or file and line number.
 func (p *Prog) InstructionString() string {
@@ -177,7 +190,7 @@ func (ctxt *Link) NewProg() *Prog {
 }
 
 func (ctxt *Link) CanReuseProgs() bool {
-	return !ctxt.Debugasm
+	return ctxt.Debugasm == 0
 }
 
 func Dconv(p *Prog, a *Addr) string {
diff --git a/test/run.go b/test/run.go
index 96192937b09..ad38d420c9b 100644
--- a/test/run.go
+++ b/test/run.go
@@ -642,7 +642,8 @@ func (t *test) run() {
 		// against a set of regexps in comments.
 		ops := t.wantedAsmOpcodes(long)
 		for _, env := range ops.Envs() {
-			cmdline := []string{"build", "-gcflags", "-S"}
+			// -S=2 forces outermost line numbers when disassembling inlined code.
+			cmdline := []string{"build", "-gcflags", "-S=2"}
 			cmdline = append(cmdline, flags...)
 			cmdline = append(cmdline, long)
 			cmd := exec.Command(goTool(), cmdline...)