sig_help_cache.diff

diff --git a/python/ycm/signature_help.py b/python/ycm/signature_help.py
index 90b1d225..0e23575d 100644
--- a/python/ycm/signature_help.py
+++ b/python/ycm/signature_help.py
@@ -20,6 +20,8 @@ import json
 from ycm import vimsupport
 from ycm.vimsupport import GetIntValue
 
+SIGNATURE_SUPPORTED = None
+
 
 class SignatureHelpState( object ):
   ACTIVE = 'ACTIVE'
@@ -78,8 +80,11 @@ def _MakeSignatureHelpBuffer( signature_info ):
 
 
 def ShouldUseSignatureHelp():
-  return ( vimsupport.VimHasFunctions( 'screenpos', 'pum_getpos' ) and
-           vimsupport.VimSupportsPopupWindows() )
+  global SIGNATURE_SUPPORTED
+  if SIGNATURE_SUPPORTED is None:
+    SIGNATURE_SUPPORTED = vimsupport.VimHasFunctions(
+        'screenpos', 'pum_getpos' ) and vimsupport.VimSupportsPopupWindows()
+  return SIGNATURE_SUPPORTED
 
 
 def UpdateSignatureHelp( state, signature_info ): # noqa
diff --git a/python/ycm/vimsupport.py b/python/ycm/vimsupport.py
index d129680e..a7aeefc5 100644
--- a/python/ycm/vimsupport.py
+++ b/python/ycm/vimsupport.py
@@ -28,6 +28,7 @@ from ycmd.utils import ( ByteOffsetToCodepointOffset,
                          ToBytes,
                          ToUnicode )
 
+POPUP_SUPPORTED = None
 BUFFER_COMMAND_MAP = { 'same-buffer'      : 'edit',
                        'split'            : 'split',
                        # These commands are obsolete. :vertical or :tab should
@@ -1251,14 +1252,17 @@ def AutoCloseOnCurrentBuffer( name ):
 
 
 def VimSupportsPopupWindows():
-  return VimHasFunctions( 'popup_create',
-                          'popup_move',
-                          'popup_hide',
-                          'popup_settext',
-                          'popup_show',
-                          'popup_close',
-                          'prop_add',
-                          'prop_type_add' )
+  global POPUP_SUPPORTED
+  if POPUP_SUPPORTED is None:
+    POPUP_SUPPORTED = VimHasFunctions( 'popup_create',
+                                       'popup_move',
+                                       'popup_hide',
+                                       'popup_settext',
+                                       'popup_show',
+                                       'popup_close',
+                                       'prop_add',
+                                       'prop_type_add' )
+  return POPUP_SUPPORTED
 
 
 def VimHasFunctions( *functions ):