runtime (gc): scan callee-saved registers while marking stack

src/runtime/gc_stack_raw.go

@@ -3,12 +3,38 @@
 
 package runtime
 
+import "internal/task"
+
 // markStack marks all root pointers found on the stack.
 //
 // This implementation is conservative and relies on the stack top (provided by
 // the linker) and getting the current stack pointer from a register. Also, it
 // assumes a descending stack. Thus, it is not very portable.
 func markStack() {
-	// Mark system stack.
-	markRoots(getSystemStackPointer(), stackTop)
+	// Scan the current stack, and all current registers.
+	scanCurrentStack()
+
+	if !task.OnSystemStack() {
+		// Mark system stack.
+		markRoots(getSystemStackPointer(), stackTop)
+	}
+}
+
+//go:export tinygo_scanCurrentStack
+func scanCurrentStack()
+
+//go:export tinygo_scanstack
+func scanstack(sp uintptr) {
+	// Mark current stack.
+	// This function is called by scanCurrentStack, after pushing all registers onto the stack.
+	// Callee-saved registers have been pushed onto stack by tinygo_localscan, so this will scan them too.
+	if task.OnSystemStack() {
+		// This is the system stack.
+		// Scan all words on the stack.
+		markRoots(sp, stackTop)
+	} else {
+		// This is a goroutine stack.
+		// It is an allocation, so scan it as if it were a value in a global.
+		markRoot(0, sp)
+	}
 }