fix fbcode weak ordering (#23511)

Summary: There is an internal fbcode assert that fails if i do not add these checks. Pull Request resolved: https://github.com/pytorch/pytorch/pull/23511 Differential Revision: D16545606 Pulled By: eellison fbshipit-source-id: cd3a799850bae8f052f9d81c1e4a2678fda19317

fix fbcode weak ordering (#23511)
Summary: There is an internal fbcode assert that fails if i do not add these checks. Pull Request resolved: https://github.com/pytorch/pytorch/pull/23511 Differential Revision: D16545606 Pulled By: eellison fbshipit-source-id: cd3a799850bae8f052f9d81c1e4a2678fda19317
dec4eaca · Elias Ellison · Facebook Github Bot · 0c9979dd · dec4eaca
--- a/torch/csrc/jit/register_prim_ops.cpp
+++ b/torch/csrc/jit/register_prim_ops.cpp
@@ -1759,7 +1759,13 @@ int listSort(Stack& stack) {
  bool reverse = pop(stack).toBool();
  c10::List<T> list = pop(stack).to<c10::List<T>>();
  std::sort(list.begin(), list.end(), [reverse](const T& a, const T& b) {
-    return (a < b) ^ reverse;
+    // FBCode errors without this check - "strict weak ordering"
+    // TODO: remove when possible, since it just slows down
+    // sorting and doesn't do anything useful
+    if (a == b) {
+      return false;
+    }
+    return (a < b) != reverse;
  });
  return 0;
 }
@@ -1783,6 +1789,10 @@ int listCopyAndSort(Stack& stack) {
  c10::List<T> list = pop(stack).to<c10::List<T>>();
  auto list_copied = list.copy();
  std::sort(list_copied.begin(), list_copied.end(), [](const T& a, const T& b) {
+    // "strict weak ordering" issue - see other sort
+    if (a == b) {
+      return false;
+    }
    return a < b;
  });
  push(stack, list_copied);
@@ -2885,16 +2895,14 @@ Operation sort_op(
        g_list.begin(),
        g_list.end(),
        [lt_func, reverse, &sort_stack](IValue a, IValue b) -> bool {
-          // FBCode errors without this check - "strict weak ordering"
-          // TODO: remove when possible, since it just slows down
-          // sorting and doesn't do anything useful
+          // "strict weak ordering" issue - see other sort
          if (a.isSameIdentity(b)) {
            return false;
          }
          sort_stack.push_back(a);
          sort_stack.push_back(b);
          lt_func->run(sort_stack);
-          return pop(sort_stack).toBool() ^ reverse;
+          return pop(sort_stack).toBool() != reverse;
        });
    if (copy_return_list) {
      push(stack, g_list);