cmd/compile: remove uncommonType.name

Reduces binary size of cmd/go by 0.5%.
For #6853.

Change-Id: I5a4b814049580ab5098ad252d979f80b70d8a5f9
Reviewed-on: https://go-review.googlesource.com/19694Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

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

@@ -492,16 +492,10 @@ func dextratype(sym *Sym, off int, t *Type, ptroff int) int {
 
 	ot := off
 	s := sym
-	if t.Sym != nil {
-		ot = dgostringptr(s, ot, t.Sym.Name)
-		if t != Types[t.Etype] && t != errortype {
-			ot = dgopkgpath(s, ot, t.Sym.Pkg)
-		} else {
-			ot = dgostringptr(s, ot, "")
-		}
+	if t.Sym != nil && t != Types[t.Etype] && t != errortype {
+		ot = dgopkgpath(s, ot, t.Sym.Pkg)
 	} else {
 		ot = dgostringptr(s, ot, "")
-		ot = dgostringptr(s, ot, "")
 	}
 
 	// slice header

src/reflect/all_test.go

@@ -5007,3 +5007,24 @@ func TestChanAlloc(t *testing.T) {
 	// a limitation of escape analysis.  If that is ever fixed the
 	// allocs < 0.5 condition will trigger and this test should be fixed.
 }
+
+type nameTest struct {
+	v    interface{}
+	want string
+}
+
+var nameTests = []nameTest{
+	{int32(0), "int32"},
+	{D1{}, "D1"},
+	{[]D1{}, ""},
+	{(chan D1)(nil), ""},
+	{(func() D1)(nil), ""},
+}
+
+func TestNames(t *testing.T) {
+	for _, test := range nameTests {
+		if got := TypeOf(test.v).Name(); got != test.want {
+			t.Errorf("%T Name()=%q, want %q", test.v, got, test.want)
+		}
+	}
+}

src/reflect/type.go

@@ -283,7 +283,6 @@ type method struct {
 // Using a pointer to this struct reduces the overall size required
 // to describe an unnamed type with no methods.
 type uncommonType struct {
-	name    *string  // name of type
 	pkgPath *string  // import path; nil for built-in types like int, string
 	methods []method // methods associated with type
 }
@@ -452,13 +451,6 @@ func (t *uncommonType) PkgPath() string {
 	return *t.pkgPath
 }
 
-func (t *uncommonType) Name() string {
-	if t == nil || t.name == nil {
-		return ""
-	}
-	return *t.name
-}
-
 func (t *rtype) String() string { return t.string }
 
 func (t *rtype) Size() uintptr { return t.size }
@@ -557,8 +549,34 @@ func (t *rtype) PkgPath() string {
 	return t.uncommonType.PkgPath()
 }
 
+func hasPrefix(s, prefix string) bool {
+	return len(s) >= len(prefix) && s[:len(prefix)] == prefix
+}
+
 func (t *rtype) Name() string {
-	return t.uncommonType.Name()
+	if hasPrefix(t.string, "map[") {
+		return ""
+	}
+	if hasPrefix(t.string, "struct {") {
+		return ""
+	}
+	if hasPrefix(t.string, "chan ") {
+		return ""
+	}
+	if hasPrefix(t.string, "func(") {
+		return ""
+	}
+	if t.string[0] == '[' || t.string[0] == '*' {
+		return ""
+	}
+	i := len(t.string) - 1
+	for i >= 0 {
+		if t.string[i] == '.' {
+			break
+		}
+		i--
+	}
+	return t.string[i+1:]
 }
 
 func (t *rtype) ChanDir() ChanDir {

src/runtime/heapdump.go

@@ -183,11 +183,12 @@ func dumptype(t *_type) {
 	dumpint(tagType)
 	dumpint(uint64(uintptr(unsafe.Pointer(t))))
 	dumpint(uint64(t.size))
-	if t.x == nil || t.x.pkgpath == nil || t.x.name == nil {
+	if t.x == nil || t.x.pkgpath == nil {
 		dumpstr(t._string)
 	} else {
 		pkgpath := stringStructOf(t.x.pkgpath)
-		name := stringStructOf(t.x.name)
+		namestr := t.name()
+		name := stringStructOf(&namestr)
 		dumpint(uint64(uintptr(pkgpath.len) + 1 + uintptr(name.len)))
 		dwrite(pkgpath.str, uintptr(pkgpath.len))
 		dwritebyte('.')

src/runtime/mfinal.go

@@ -340,7 +340,7 @@ func SetFinalizer(obj interface{}, finalizer interface{}) {
 		// ok - same type
 		goto okarg
 	case fint.kind&kindMask == kindPtr:
-		if (fint.x == nil || fint.x.name == nil || etyp.x == nil || etyp.x.name == nil) && (*ptrtype)(unsafe.Pointer(fint)).elem == ot.elem {
+		if (fint.x == nil || etyp.x == nil) && (*ptrtype)(unsafe.Pointer(fint)).elem == ot.elem {
 			// ok - not same type, but both pointers,
 			// one or the other is unnamed, and same element type, so assignable.
 			goto okarg

src/runtime/type.go

@@ -28,6 +28,36 @@ type _type struct {
 	x       *uncommontype
 }
 
+func hasPrefix(s, prefix string) bool {
+	return len(s) >= len(prefix) && s[:len(prefix)] == prefix
+}
+
+func (t *_type) name() string {
+	if hasPrefix(t._string, "map[") {
+		return ""
+	}
+	if hasPrefix(t._string, "struct {") {
+		return ""
+	}
+	if hasPrefix(t._string, "chan ") {
+		return ""
+	}
+	if hasPrefix(t._string, "func(") {
+		return ""
+	}
+	if t._string[0] == '[' || t._string[0] == '*' {
+		return ""
+	}
+	i := len(t._string) - 1
+	for i >= 0 {
+		if t._string[i] == '.' {
+			break
+		}
+		i--
+	}
+	return t._string[i+1:]
+}
+
 type method struct {
 	name    *string
 	pkgpath *string
@@ -38,7 +68,6 @@ type method struct {
 }
 
 type uncommontype struct {
-	name    *string
 	pkgpath *string
 	mhdr    []method
 }