[project @ 1999-03-11 17:39:18 by simonpj]

Fix loadInterface to avoid repeated loading of PrelPack.hi-boot

diff --git a/ghc/compiler/rename/RnIfaces.lhs b/ghc/compiler/rename/RnIfaces.lhs
index f507e6a..b8bd40c 100644 (file)
--- a/ghc/compiler/rename/RnIfaces.lhs
+++ b/ghc/compiler/rename/RnIfaces.lhs
@@ -172,14 +172,15 @@ loadInterface :: SDoc -> Module -> RnMG (Module, Ifaces)
 loadInterface doc_str load_mod
  = getIfacesRn                 `thenRn` \ ifaces ->
    let
-       new_hif              = moduleIfaceFlavour load_mod
+       hi_boot_wanted       = bootFlavour (moduleIfaceFlavour load_mod)
        mod_map              = iModMap ifaces
        (insts, tycls_names) = iDefInsts ifaces
+       
    in
        -- CHECK WHETHER WE HAVE IT ALREADY
    case lookupFM mod_map load_mod of {
        Just (existing_hif, _, _) 
-               | bootFlavour new_hif || not (bootFlavour existing_hif)
+               | hi_boot_wanted || not (bootFlavour existing_hif)
                ->      -- Already in the cache, and new version is no better than old,
                        -- so don't re-read it
                    returnRn (setModuleFlavour existing_hif load_mod, ifaces) ;
@@ -188,8 +189,20 @@ loadInterface doc_str load_mod
        -- READ THE MODULE IN
    findAndReadIface doc_str load_mod           `thenRn` \ read_result ->
    case read_result of {
-       -- Check for not found
-       Nothing ->      -- Not found, so add an empty export env to the Ifaces map
+       Nothing | not hi_boot_wanted && load_mod `elem` thinAirModules
+               -> -- Hack alert!  When compiling PrelBase we have to load the
+                  -- decls for packCString# and friends; they are 'thin-air' Ids
+                  -- (see PrelInfo.lhs).  So if we don't find the HiFile we quietly
+                  -- look for a .hi-boot file instead, and use that
+                  --
+                  -- NB this causes multiple "failed" attempts to read PrelPack,
+                  --    which makes curious reading with -dshow-rn-trace, but
+                  --    there's no harm done
+                  loadInterface doc_str (mkBootModule load_mod)
+
+              
+               | otherwise
+               ->      -- Not found, so add an empty export env to the Ifaces map
                        -- so that we don't look again
                   let
                        new_mod_map = addToFM mod_map load_mod (hiFile, 0, [])
@@ -1050,15 +1063,8 @@ findAndReadIface doc_str mod_name
     case (lookupFM himap (moduleUserString mod_name)) of
          -- Found the file
        Just fpath -> readIface mod_name fpath
-        -- Hack alert!  When compiling PrelBase we have to load the
-        -- decls for packCString# and friends; they are 'thin-air' Ids
-        -- (see PrelInfo.lhs).  So if we don't find the HiFile we quietly
-        -- look for a .hi-boot file instead, and use that
-       Nothing |  not from_hi_boot && mod_name `elem` thinAirModules
-              -> findAndReadIface doc_str (mkBootModule mod_name)
-               | otherwise              
-              -> traceRn (ptext SLIT("...failed"))     `thenRn_`
-                 returnRn Nothing
+       Nothing    -> traceRn (ptext SLIT("...failed")) `thenRn_`
+                    returnRn Nothing
   where
     hif                 = moduleIfaceFlavour mod_name
     from_hi_boot = bootFlavour hif