runtime: lock output in print/println

This ensures that calls to print/println happening in different threads
are not interleaved. It's a task.PMutex, so this should only change
things when threading is used.

This matches the Go compiler, which does the same thing:
https://godbolt.org/z/na5KzE7en

The locks are not recursive, which means that we need to be careful to
not call `print` or `println` inside a runtime.print* implementation,
inside putchar (recursively), and inside signal handlers. Making them
recursive might be useful to do in the future, but it's not really
necessary.

src/runtime/print.go

@@ -1,6 +1,7 @@
 package runtime
 
 import (
+	"internal/task"
 	"unsafe"
 )
 
@@ -8,6 +9,18 @@ type stringer interface {
 	String() string
 }
 
+// Lock to make sure print calls do not interleave.
+// This is a no-op lock on systems that do not have parallelism.
+var printLock task.PMutex
+
+func printlock() {
+	printLock.Lock()
+}
+
+func printunlock() {
+	printLock.Unlock()
+}
+
 //go:nobounds
 func printstring(s string) {
 	for i := 0; i < len(s); i++ {
@@ -293,67 +306,84 @@ func printnl() {
 func printitf(msg interface{}) {
 	switch msg := msg.(type) {
 	case bool:
-		print(msg)
+		printbool(msg)
 	case int:
-		print(msg)
+		switch unsafe.Sizeof(msg) {
+		case 8:
+			printint64(int64(msg))
+		case 4:
+			printint32(int32(msg))
+		}
 	case int8:
-		print(msg)
+		printint8(msg)
 	case int16:
-		print(msg)
+		printint16(msg)
 	case int32:
-		print(msg)
+		printint32(msg)
 	case int64:
-		print(msg)
+		printint64(msg)
 	case uint:
-		print(msg)
+		switch unsafe.Sizeof(msg) {
+		case 8:
+			printuint64(uint64(msg))
+		case 4:
+			printuint32(uint32(msg))
+		}
 	case uint8:
-		print(msg)
+		printuint8(msg)
 	case uint16:
-		print(msg)
+		printuint16(msg)
 	case uint32:
-		print(msg)
+		printuint32(msg)
 	case uint64:
-		print(msg)
+		printuint64(msg)
 	case uintptr:
-		print(msg)
+		printuintptr(msg)
 	case float32:
-		print(msg)
+		printfloat32(msg)
 	case float64:
-		print(msg)
+		printfloat64(msg)
 	case complex64:
-		print(msg)
+		printcomplex64(msg)
 	case complex128:
-		print(msg)
+		printcomplex128(msg)
 	case string:
-		print(msg)
+		printstring(msg)
 	case error:
-		print(msg.Error())
+		printstring(msg.Error())
 	case stringer:
-		print(msg.String())
+		printstring(msg.String())
 	default:
 		// cast to underlying type
 		itf := *(*_interface)(unsafe.Pointer(&msg))
 		putchar('(')
 		printuintptr(uintptr(itf.typecode))
 		putchar(':')
-		print(itf.value)
+		printptr(uintptr(itf.value))
 		putchar(')')
 	}
 }
 
 func printmap(m *hashmap) {
-	print("map[")
+	printstring("map[")
 	if m == nil {
-		print("nil")
+		printstring("nil")
 	} else {
-		print(uint(m.count))
+		switch unsafe.Sizeof(m.count) {
+		case 8:
+			printuint64(uint64(m.count))
+		case 4:
+			printuint32(uint32(m.count))
+		case 2:
+			printuint16(uint16(m.count))
+		}
 	}
 	putchar(']')
 }
 
 func printptr(ptr uintptr) {
 	if ptr == 0 {
-		print("nil")
+		printstring("nil")
 		return
 	}
 	putchar('0')