compiler,reflect: add tagged pointers for **T etc

Author: dgryski

compiler/interface.go

@@ -127,6 +127,18 @@ func (c *compilerContext) getTypeCode(typ types.Type) llvm.Value {
 	if _, ok := typ.Underlying().(*types.Interface); ok {
 		hasMethodSet = false
 	}
+
+	// Short-circuit all the global pointer logic here for pointers to pointers.
+	if typ, ok := typ.(*types.Pointer); ok {
+		if _, ok := typ.Elem().(*types.Pointer); ok {
+			// For a pointer to a pointer, we just increase the pointer by 1
+			ptr := c.getTypeCode(typ.Elem())
+			return llvm.ConstGEP(c.ctx.Int8Type(), ptr, []llvm.Value{
+				llvm.ConstInt(llvm.Int32Type(), 1, false),
+			})
+		}
+	}
+
 	typeCodeName, isLocal := getTypeCodeName(typ)
 	globalName := "reflect/types.type:" + typeCodeName
 	var global llvm.Value
@@ -391,6 +403,9 @@ func (c *compilerContext) getTypeCode(typ types.Type) llvm.Value {
 			}, typeFields...)
 		}
 		alignment := c.targetData.TypeAllocSize(c.i8ptrType)
+		if alignment < 4 {
+			alignment = 4
+		}
 		globalValue := c.ctx.ConstStruct(typeFields, false)
 		global.SetInitializer(globalValue)
 		if isLocal {

src/reflect/type.go

@@ -477,7 +477,15 @@ func (t *rawType) underlying() *rawType {
 	return t
 }
 
+func (t *rawType) ptrtag() uintptr {
+	return uintptr(unsafe.Pointer(t)) & 0b11
+}
+
 func (t *rawType) isNamed() bool {
+	if tag := t.ptrtag(); tag != 0 {
+		return false
+	}
+
 	return t.meta&flagNamed != 0
 }
 
@@ -502,9 +510,13 @@ func pointerTo(t *rawType) *rawType {
 
 	switch t.Kind() {
 	case Pointer:
+		if tag := t.ptrtag(); tag < 3 {
+			return (*rawType)(unsafe.Add(unsafe.Pointer(t), 1))
+		}
+
 		// TODO(dgryski): This is blocking https://github.com/tinygo-org/tinygo/issues/3131
 		// We need to be able to create types that match existing types to prevent typecode equality.
-		panic("reflect: cannot make **T type")
+		panic("reflect: cannot make *****T type")
 	case Struct:
 		return (*structType)(unsafe.Pointer(t)).ptrTo
 	default:
@@ -581,6 +593,11 @@ func (t *rawType) Kind() Kind {
 	if t == nil {
 		return Invalid
 	}
+
+	if tag := t.ptrtag(); tag != 0 {
+		return Pointer
+	}
+
 	return Kind(t.meta & kindMask)
 }
 
@@ -591,6 +608,10 @@ func (t *rawType) Elem() Type {
 }
 
 func (t *rawType) elem() *rawType {
+	if tag := t.ptrtag(); tag != 0 {
+		return (*rawType)(unsafe.Add(unsafe.Pointer(t), -1))
+	}
+
 	underlying := t.underlying()
 	switch underlying.Kind() {
 	case Pointer: