From ed90dd62e7846d42cc44b43c199d58697b031a19 Mon Sep 17 00:00:00 2001
From: Simon Marlow <marlowsd@gmail.com>
Date: Fri, 27 Jan 2012 09:53:48 +0000
Subject: Make the old codegen run in constant space too

---
 compiler/codeGen/CodeGen.lhs | 57 +++++++++++++++++++++++++++-----------------
 1 file changed, 35 insertions(+), 22 deletions(-)

(limited to 'compiler/codeGen/CodeGen.lhs')

diff --git a/compiler/codeGen/CodeGen.lhs b/compiler/codeGen/CodeGen.lhs
index aa561c4f40..f8898450ef 100644
--- a/compiler/codeGen/CodeGen.lhs
+++ b/compiler/codeGen/CodeGen.lhs
@@ -45,6 +45,13 @@ import TyCon
 import Module
 import ErrUtils
 import Panic
+import Outputable
+
+import OrdList
+import Stream (Stream, liftIO)
+import qualified Stream
+
+import Data.IORef
 
 codeGen :: DynFlags
         -> Module                     -- Module we are compiling
@@ -52,32 +59,38 @@ codeGen :: DynFlags
         -> CollectedCCs               -- (Local/global) cost-centres needing declaring/registering.
         -> [(StgBinding,[(Id,[Id])])] -- Bindings to convert, with SRTs
         -> HpcInfo                    -- Profiling info
-        -> IO [CmmGroup]
+        -> Stream IO CmmGroup ()
               -- N.B. returning '[Cmm]' and not 'Cmm' here makes it
               -- possible for object splitting to split up the
               -- pieces later.
 
-codeGen dflags this_mod data_tycons cost_centre_info stg_binds hpc_info = do
-    showPass dflags "CodeGen"
-    code_stuff <-
-        initC dflags this_mod $ do
-            cmm_binds  <- mapM (getCmm . cgTopBinding dflags) stg_binds
-            cmm_tycons <- mapM cgTyCon data_tycons
-            cmm_init   <- getCmm (mkModuleInit dflags cost_centre_info this_mod hpc_info)
-            return (cmm_init : cmm_binds ++ cmm_tycons)
-                -- Put datatype_stuff after code_stuff, because the
-                -- datatype closure table (for enumeration types) to
-                -- (say) PrelBase_True_closure, which is defined in
-                -- code_stuff
-
-                -- Note [codegen-split-init] the cmm_init block must
-                -- come FIRST.  This is because when -split-objs is on
-                -- we need to combine this block with its
-                -- initialisation routines; see Note
-                -- [pipeline-split-init].
-
-    dumpIfSet_dyn dflags Opt_D_dump_cmm "Cmm" (pprCmms (targetPlatform dflags) code_stuff)
-    return code_stuff
+codeGen dflags this_mod data_tycons cost_centre_info stg_binds hpc_info
+
+   = do { liftIO $ showPass dflags "CodeGen"
+
+        ; cgref <- liftIO $ newIORef =<< initC
+        ; let cg :: FCode CmmGroup -> Stream IO CmmGroup ()
+              cg fcode = do
+                cmm <- liftIO $ do
+                         st <- readIORef cgref
+                         let (a,st') = runC dflags this_mod st fcode
+
+                         dumpIfSet_dyn dflags Opt_D_dump_cmm "Cmm" $
+                             pprPlatform (targetPlatform dflags) a
+
+                         -- NB. stub-out cgs_tops and cgs_stmts.  This fixes
+                         -- a big space leak.  DO NOT REMOVE!
+                         writeIORef cgref $! st'{ cgs_tops = nilOL,
+                                                  cgs_stmts = nilOL }
+                         return a
+                Stream.yield cmm
+
+        ; cg (getCmm $ mkModuleInit dflags cost_centre_info this_mod hpc_info)
+
+        ; mapM_ (cg . getCmm . cgTopBinding dflags) stg_binds
+
+        ; mapM_ (cg . cgTyCon) data_tycons
+        }
 
 mkModuleInit
         :: DynFlags
-- 
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