Change the way module initialisation is done (#3252, #4417)

Previously the code generator generated small code fragments labelled
with __stginit_M for each module M, and these performed whatever
initialisation was necessary for that module and recursively invoked
the initialisation functions for imported modules.  This appraoch had
drawbacks:

 - FFI users had to call hs_add_root() to ensure the correct
   initialisation routines were called.  This is a non-standard,
   and ugly, API.

 - unless we were using -split-objs, the __stginit dependencies would
   entail linking the whole transitive closure of modules imported,
   whether they were actually used or not.  In an extreme case (#4387,
   #4417), a module from GHC might be imported for use in Template
   Haskell or an annotation, and that would force the whole of GHC to
   be needlessly linked into the final executable.

So now instead we do our initialisation with C functions marked with
__attribute__((constructor)), which are automatically invoked at
program startup time (or DSO load-time).  The C initialisers are
emitted into the stub.c file.  This means that every time we compile
with -prof or -hpc, we now get a stub file, but thanks to #3687 that
is now invisible to the user.

There are some refactorings in the RTS (particularly for HPC) to
handle the fact that initialisers now get run earlier than they did
before.

The __stginit symbols are still generated, and the hs_add_root()
function still exists (but does nothing), for backwards compatibility.

1 files changed, 5 insertions, 36 deletions

diff --git a/compiler/codeGen/StgCmmHpc.hs b/compiler/codeGen/StgCmmHpc.hs
index a93af34961..fae3bef016 100644
--- a/compiler/codeGen/StgCmmHpc.hs
+++ b/compiler/codeGen/StgCmmHpc.hs
@@ -8,9 +8,7 @@
 
 module StgCmmHpc ( initHpc, mkTickBox ) where
 
-import StgCmmUtils
 import StgCmmMonad
-import StgCmmForeign
 
 import MkGraph
 import CmmDecl
@@ -18,11 +16,8 @@ import CmmExpr
 import CLabel
 import Module
 import CmmUtils
-import FastString
 import HscTypes
-import Data.Char
 import StaticFlags
-import BasicTypes
 
 mkTickBox :: Module -> Int -> CmmAGraph
 mkTickBox mod n 
@@ -35,41 +30,15 @@ mkTickBox mod n
                         (CmmLit $ CmmLabel $ mkHpcTicksLabel $ mod)
                         n
 
-initHpc :: Module -> HpcInfo -> FCode CmmAGraph
+initHpc :: Module -> HpcInfo -> FCode ()
 -- Emit top-level tables for HPC and return code to initialise
 initHpc _ (NoHpcInfo {})
-  = return mkNop
-initHpc this_mod (HpcInfo tickCount hashNo)
-  = getCode $ whenC opt_Hpc $
-    do	{ emitData ReadOnlyData
-              [ CmmDataLabel mkHpcModuleNameLabel
-              , CmmString $ map (fromIntegral . ord)
-                               (full_name_str)
-                            ++ [0]
-              ]
-        ; emitData Data $ [ CmmDataLabel (mkHpcTicksLabel this_mod)
+  = return ()
+initHpc this_mod (HpcInfo tickCount _hashNo)
+  = whenC opt_Hpc $
+    do  { emitData Data $ [ CmmDataLabel (mkHpcTicksLabel this_mod)
               ] ++
               [ CmmStaticLit (CmmInt 0 W64)
               | _ <- take tickCount [0::Int ..]
               ]
-
-    	; id <- newTemp bWord -- TODO FIXME NOW
-        ; emitCCall
-               [(id,NoHint)]
-               (CmmLit $ CmmLabel $ mkForeignLabel mod_alloc Nothing ForeignLabelInThisPackage IsFunction)
-               [ (mkLblExpr mkHpcModuleNameLabel,AddrHint)
-               , (CmmLit $ mkIntCLit tickCount,NoHint)
-               , (CmmLit $ mkIntCLit hashNo,NoHint)
-               , (CmmLit $ CmmLabel $ mkHpcTicksLabel $ this_mod,AddrHint)
-               ]
        }
-  where
-    mod_alloc = mkFastString "hs_hpc_module"
-    module_name_str = moduleNameString (Module.moduleName this_mod)
-    full_name_str   = if modulePackageId this_mod == mainPackageId 
-		      then module_name_str
-		      else packageIdString (modulePackageId this_mod) ++ "/" ++
-			   module_name_str
-
-
-