internal/abi: add EscapeNonString, EscapeToResultNonString

src/internal/abi/escape.go

@@ -15,3 +15,35 @@ func Escape[T any](x T) T {
 	// as-is.
 	panic("internal/abi.Escape: unreachable (implemented in the compiler)")
 }
+
+// EscapeNonString forces v to be on the heap, if v contains a
+// non-string pointer.
+//
+// This is used in hash/maphash.Comparable. We cannot hash pointers
+// to local variables on stack, as their addresses might change on
+// stack growth. Strings are okay as the hash depends on only the
+// content, not the pointer.
+//
+// This is essentially
+//
+//	if hasNonStringPointers(T) { Escape(v) }
+//
+// Implemented as a compiler intrinsic.
+func EscapeNonString[T any](v T) { panic("intrinsic") }
+
+// EscapeToResultNonString models a data flow edge from v to the result,
+// if v contains a non-string pointer. If v contains only string pointers,
+// it returns a copy of v, but is not modeled as a data flow edge
+// from the escape analysis's perspective.
+//
+// This is used in unique.clone, to model the data flow edge on the
+// value with strings excluded, because strings are cloned (by
+// content).
+//
+// TODO: probably we should define this as a intrinsic and EscapeNonString
+// could just be "heap = EscapeToResultNonString(v)". This way we can model
+// an edge to the result but not necessarily heap.
+func EscapeToResultNonString[T any](v T) T {
+	EscapeNonString(v)
+	return *(*T)(NoEscape(unsafe.Pointer(&v)))
+}