From 6122fd70ca82b2156a32f2b369d509b3a21a7128 Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Fri, 27 Nov 2015 18:08:46 +0800
Subject: [PATCH] compiler.types: TVar.find: improve path compression.

After this change, the compiler's complexity is nearly linear
even when very large arrays are used.
---
 artiq/compiler/types.py | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/artiq/compiler/types.py b/artiq/compiler/types.py
index 795e8f80e..88f1ae302 100644
--- a/artiq/compiler/types.py
+++ b/artiq/compiler/types.py
@@ -71,7 +71,13 @@ class TVar(Type):
                     root = root.parent
 
             # path compression
-            self.parent = root
+            iter = self
+            while isinstance(iter, TVar):
+                if iter is iter.parent:
+                    break
+                else:
+                    iter, iter.parent = iter.parent, root
+
             return root
 
     def unify(self, other):