diff --git a/src/cmd/compile/internal/base/debug.go b/src/cmd/compile/internal/base/debug.go
index e2245e1c26..37e345bd7f 100644
--- a/src/cmd/compile/internal/base/debug.go
+++ b/src/cmd/compile/internal/base/debug.go
@@ -6,15 +6,6 @@
 
 package base
 
-import (
-	"fmt"
-	"log"
-	"os"
-	"reflect"
-	"strconv"
-	"strings"
-)
-
 // Debug holds the parsed debugging configuration values.
 var Debug DebugFlags
 
@@ -26,7 +17,7 @@ var Debug DebugFlags
 // Each setting is name=value; for ints, name is short for name=1.
 type DebugFlags struct {
 	Append               int    `help:"print information about append compilation"`
-	Checkptr             int    `help:"instrument unsafe pointer conversions"`
+	Checkptr             int    `help:"instrument unsafe pointer conversions\n0: instrumentation disabled\n1: conversions involving unsafe.Pointer are instrumented\n2: conversions to unsafe.Pointer force heap allocation"`
 	Closure              int    `help:"print information about closure compilation"`
 	DclStack             int    `help:"run internal dclstack check"`
 	Defer                int    `help:"print information about defer compilation"`
@@ -40,7 +31,7 @@ type DebugFlags struct {
 	LocationLists        int    `help:"print information about DWARF location list creation"`
 	Nil                  int    `help:"print information about nil checks"`
 	NoOpenDefer          int    `help:"disable open-coded defers"`
-	PCTab                string `help:"print named pc-value table"`
+	PCTab                string `help:"print named pc-value table\nOne of: pctospadj, pctofile, pctoline, pctoinline, pctopcdata"`
 	Panic                int    `help:"show all compiler panics"`
 	Slice                int    `help:"print information about slice compilation"`
 	SoftFloat            int    `help:"force compiler to emit soft-float code"`
@@ -52,141 +43,10 @@ type DebugFlags struct {
 	WB                   int    `help:"print information about write barriers"`
 	ABIWrap              int    `help:"print information about ABI wrapper generation"`
 
-	any bool // set when any of the values have been set
-}
-
-// Any reports whether any of the debug flags have been set.
-func (d *DebugFlags) Any() bool { return d.any }
-
-type debugField struct {
-	name string
-	help string
-	val  interface{} // *int or *string
-}
-
-var debugTab []debugField
-
-func init() {
-	v := reflect.ValueOf(&Debug).Elem()
-	t := v.Type()
-	for i := 0; i < t.NumField(); i++ {
-		f := t.Field(i)
-		if f.Name == "any" {
-			continue
-		}
-		name := strings.ToLower(f.Name)
-		help := f.Tag.Get("help")
-		if help == "" {
-			panic(fmt.Sprintf("base.Debug.%s is missing help text", f.Name))
-		}
-		ptr := v.Field(i).Addr().Interface()
-		switch ptr.(type) {
-		default:
-			panic(fmt.Sprintf("base.Debug.%s has invalid type %v (must be int or string)", f.Name, f.Type))
-		case *int, *string:
-			// ok
-		}
-		debugTab = append(debugTab, debugField{name, help, ptr})
-	}
+	Any bool // set when any of the debug flags have been set
 }
 
 // DebugSSA is called to set a -d ssa/... option.
 // If nil, those options are reported as invalid options.
 // If DebugSSA returns a non-empty string, that text is reported as a compiler error.
 var DebugSSA func(phase, flag string, val int, valString string) string
-
-// parseDebug parses the -d debug string argument.
-func parseDebug(debugstr string) {
-	// parse -d argument
-	if debugstr == "" {
-		return
-	}
-	Debug.any = true
-Split:
-	for _, name := range strings.Split(debugstr, ",") {
-		if name == "" {
-			continue
-		}
-		// display help about the -d option itself and quit
-		if name == "help" {
-			fmt.Print(debugHelpHeader)
-			maxLen := len("ssa/help")
-			for _, t := range debugTab {
-				if len(t.name) > maxLen {
-					maxLen = len(t.name)
-				}
-			}
-			for _, t := range debugTab {
-				fmt.Printf("\t%-*s\t%s\n", maxLen, t.name, t.help)
-			}
-			// ssa options have their own help
-			fmt.Printf("\t%-*s\t%s\n", maxLen, "ssa/help", "print help about SSA debugging")
-			fmt.Print(debugHelpFooter)
-			os.Exit(0)
-		}
-		val, valstring, haveInt := 1, "", true
-		if i := strings.IndexAny(name, "=:"); i >= 0 {
-			var err error
-			name, valstring = name[:i], name[i+1:]
-			val, err = strconv.Atoi(valstring)
-			if err != nil {
-				val, haveInt = 1, false
-			}
-		}
-		for _, t := range debugTab {
-			if t.name != name {
-				continue
-			}
-			switch vp := t.val.(type) {
-			case nil:
-				// Ignore
-			case *string:
-				*vp = valstring
-			case *int:
-				if !haveInt {
-					log.Fatalf("invalid debug value %v", name)
-				}
-				*vp = val
-			default:
-				panic("bad debugtab type")
-			}
-			continue Split
-		}
-		// special case for ssa for now
-		if DebugSSA != nil && strings.HasPrefix(name, "ssa/") {
-			// expect form ssa/phase/flag
-			// e.g. -d=ssa/generic_cse/time
-			// _ in phase name also matches space
-			phase := name[4:]
-			flag := "debug" // default flag is debug
-			if i := strings.Index(phase, "/"); i >= 0 {
-				flag = phase[i+1:]
-				phase = phase[:i]
-			}
-			err := DebugSSA(phase, flag, val, valstring)
-			if err != "" {
-				log.Fatalf(err)
-			}
-			continue Split
-		}
-		log.Fatalf("unknown debug key -d %s\n", name)
-	}
-}
-
-const debugHelpHeader = `usage: -d arg[,arg]* and arg is <key>[=<value>]
-
-<key> is one of:
-
-`
-
-const debugHelpFooter = `
-<value> is key-specific.
-
-Key "checkptr" supports values:
-	"0": instrumentation disabled
-	"1": conversions involving unsafe.Pointer are instrumented
-	"2": conversions to unsafe.Pointer force heap allocation
-
-Key "pctab" supports values:
-	"pctospadj", "pctofile", "pctoline", "pctoinline", "pctopcdata"
-`
diff --git a/src/cmd/compile/internal/base/flag.go b/src/cmd/compile/internal/base/flag.go
index 9d630ce97a..f38eaa91c0 100644
--- a/src/cmd/compile/internal/base/flag.go
+++ b/src/cmd/compile/internal/base/flag.go
@@ -64,19 +64,19 @@ type CmdFlags struct {
 	// V is added by objabi.AddVersionFlag
 	W CountFlag "help:\"debug parse tree after type checking\""
 
-	LowerC int          "help:\"concurrency during compilation (1 means no concurrency)\""
-	LowerD func(string) "help:\"enable debugging settings; try -d help\""
-	LowerE CountFlag    "help:\"no limit on number of errors reported\""
-	LowerH CountFlag    "help:\"halt on error\""
-	LowerJ CountFlag    "help:\"debug runtime-initialized variables\""
-	LowerL CountFlag    "help:\"disable inlining\""
-	LowerM CountFlag    "help:\"print optimization decisions\""
-	LowerO string       "help:\"write output to `file`\""
-	LowerP *string      "help:\"set expected package import `path`\"" // &Ctxt.Pkgpath, set below
-	LowerR CountFlag    "help:\"debug generated wrappers\""
-	LowerT bool         "help:\"enable tracing for debugging the compiler\""
-	LowerW CountFlag    "help:\"debug type checking\""
-	LowerV *bool        "help:\"increase debug verbosity\""
+	LowerC int        "help:\"concurrency during compilation (1 means no concurrency)\""
+	LowerD flag.Value "help:\"enable debugging settings; try -d help\""
+	LowerE CountFlag  "help:\"no limit on number of errors reported\""
+	LowerH CountFlag  "help:\"halt on error\""
+	LowerJ CountFlag  "help:\"debug runtime-initialized variables\""
+	LowerL CountFlag  "help:\"disable inlining\""
+	LowerM CountFlag  "help:\"print optimization decisions\""
+	LowerO string     "help:\"write output to `file`\""
+	LowerP *string    "help:\"set expected package import `path`\"" // &Ctxt.Pkgpath, set below
+	LowerR CountFlag  "help:\"debug generated wrappers\""
+	LowerT bool       "help:\"enable tracing for debugging the compiler\""
+	LowerW CountFlag  "help:\"debug type checking\""
+	LowerV *bool      "help:\"increase debug verbosity\""
 
 	// Special characters
 	Percent          int  "flag:\"%\" help:\"debug non-static initializers\""
@@ -145,7 +145,7 @@ func ParseFlags() {
 	Flag.I = addImportDir
 
 	Flag.LowerC = 1
-	Flag.LowerD = parseDebug
+	Flag.LowerD = objabi.NewDebugFlag(&Debug, DebugSSA)
 	Flag.LowerP = &Ctxt.Pkgpath
 	Flag.LowerV = &Ctxt.Debugvlog
 
@@ -331,7 +331,11 @@ func registerFlags() {
 			f := v.Field(i).Interface().(func(string))
 			objabi.Flagfn1(name, help, f)
 		default:
-			panic(fmt.Sprintf("base.Flag.%s has unexpected type %s", f.Name, f.Type))
+			if val, ok := v.Field(i).Interface().(flag.Value); ok {
+				flag.Var(val, name, help)
+			} else {
+				panic(fmt.Sprintf("base.Flag.%s has unexpected type %s", f.Name, f.Type))
+			}
 		}
 	}
 }
@@ -359,7 +363,7 @@ func concurrentBackendAllowed() bool {
 	// while writing the object file, and that is non-concurrent.
 	// Adding Debug_vlog, however, causes Debug.S to also print
 	// while flushing the plist, which happens concurrently.
-	if Ctxt.Debugvlog || Debug.Any() || Flag.Live > 0 {
+	if Ctxt.Debugvlog || Debug.Any || Flag.Live > 0 {
 		return false
 	}
 	// TODO: Test and delete this condition.
diff --git a/src/cmd/internal/objabi/flag.go b/src/cmd/internal/objabi/flag.go
index e41fc570b0..f75c054fcb 100644
--- a/src/cmd/internal/objabi/flag.go
+++ b/src/cmd/internal/objabi/flag.go
@@ -13,6 +13,8 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
+	"reflect"
+	"sort"
 	"strconv"
 	"strings"
 )
@@ -202,3 +204,165 @@ func DecodeArg(arg string) string {
 	}
 	return b.String()
 }
+
+type debugField struct {
+	name string
+	help string
+	val  interface{} // *int or *string
+}
+
+type DebugFlag struct {
+	tab map[string]debugField
+	any *bool
+
+	debugSSA DebugSSA
+}
+
+// A DebugSSA function is called to set a -d ssa/... option.
+// If nil, those options are reported as invalid options.
+// If DebugSSA returns a non-empty string, that text is reported as a compiler error.
+// If phase is "help", it should print usage information and terminate the process.
+type DebugSSA func(phase, flag string, val int, valString string) string
+
+// NewDebugFlag constructs a DebugFlag for the fields of debug, which
+// must be a pointer to a struct.
+//
+// Each field of *debug is a different value, named for the lower-case of the field name.
+// Each field must be an int or string and must have a `help` struct tag.
+// There may be an "Any bool" field, which will be set if any debug flags are set.
+//
+// The returned flag takes a comma-separated list of settings.
+// Each setting is name=value; for ints, name is short for name=1.
+//
+// If debugSSA is non-nil, any debug flags of the form ssa/... will be
+// passed to debugSSA for processing.
+func NewDebugFlag(debug interface{}, debugSSA DebugSSA) *DebugFlag {
+	flag := &DebugFlag{
+		tab:      make(map[string]debugField),
+		debugSSA: debugSSA,
+	}
+
+	v := reflect.ValueOf(debug).Elem()
+	t := v.Type()
+	for i := 0; i < t.NumField(); i++ {
+		f := t.Field(i)
+		ptr := v.Field(i).Addr().Interface()
+		if f.Name == "Any" {
+			switch ptr := ptr.(type) {
+			default:
+				panic("debug.Any must have type bool")
+			case *bool:
+				flag.any = ptr
+			}
+			continue
+		}
+		name := strings.ToLower(f.Name)
+		help := f.Tag.Get("help")
+		if help == "" {
+			panic(fmt.Sprintf("debug.%s is missing help text", f.Name))
+		}
+		switch ptr.(type) {
+		default:
+			panic(fmt.Sprintf("debug.%s has invalid type %v (must be int or string)", f.Name, f.Type))
+		case *int, *string:
+			// ok
+		}
+		flag.tab[name] = debugField{name, help, ptr}
+	}
+
+	return flag
+}
+
+func (f *DebugFlag) Set(debugstr string) error {
+	if debugstr == "" {
+		return nil
+	}
+	if f.any != nil {
+		*f.any = true
+	}
+	for _, name := range strings.Split(debugstr, ",") {
+		if name == "" {
+			continue
+		}
+		// display help about the debug option itself and quit
+		if name == "help" {
+			fmt.Print(debugHelpHeader)
+			maxLen, names := 0, []string{}
+			if f.debugSSA != nil {
+				maxLen = len("ssa/help")
+			}
+			for name := range f.tab {
+				if len(name) > maxLen {
+					maxLen = len(name)
+				}
+				names = append(names, name)
+			}
+			sort.Strings(names)
+			// Indent multi-line help messages.
+			nl := fmt.Sprintf("\n\t%-*s\t", maxLen, "")
+			for _, name := range names {
+				help := f.tab[name].help
+				fmt.Printf("\t%-*s\t%s\n", maxLen, name, strings.Replace(help, "\n", nl, -1))
+			}
+			if f.debugSSA != nil {
+				// ssa options have their own help
+				fmt.Printf("\t%-*s\t%s\n", maxLen, "ssa/help", "print help about SSA debugging")
+			}
+			os.Exit(0)
+		}
+
+		val, valstring, haveInt := 1, "", true
+		if i := strings.IndexAny(name, "=:"); i >= 0 {
+			var err error
+			name, valstring = name[:i], name[i+1:]
+			val, err = strconv.Atoi(valstring)
+			if err != nil {
+				val, haveInt = 1, false
+			}
+		}
+
+		if t, ok := f.tab[name]; ok {
+			switch vp := t.val.(type) {
+			case nil:
+				// Ignore
+			case *string:
+				*vp = valstring
+			case *int:
+				if !haveInt {
+					log.Fatalf("invalid debug value %v", name)
+				}
+				*vp = val
+			default:
+				panic("bad debugtab type")
+			}
+		} else if f.debugSSA != nil && strings.HasPrefix(name, "ssa/") {
+			// expect form ssa/phase/flag
+			// e.g. -d=ssa/generic_cse/time
+			// _ in phase name also matches space
+			phase := name[4:]
+			flag := "debug" // default flag is debug
+			if i := strings.Index(phase, "/"); i >= 0 {
+				flag = phase[i+1:]
+				phase = phase[:i]
+			}
+			err := f.debugSSA(phase, flag, val, valstring)
+			if err != "" {
+				log.Fatalf(err)
+			}
+		} else {
+			return fmt.Errorf("unknown debug key %s\n", name)
+		}
+	}
+
+	return nil
+}
+
+const debugHelpHeader = `usage: -d arg[,arg]* and arg is <key>[=<value>]
+
+<key> is one of:
+
+`
+
+func (f *DebugFlag) String() string {
+	return ""
+}