Big collection of patches for the new codegen branch.

o Fixed bug that emitted the copy-in code for closure entry
  in the wrong place -- at the initialization of the closure.
o Refactored some of the closure entry code.
o Added code to check that no LocalRegs are live-in to a procedure
   -- trip up some buggy programs earlier
o Fixed environment bindings for thunks
   -- we weren't (re)binding the free variables in a thunk
o Fixed a bug in proc-point splitting that dropped some updates
  to the entry block in a procedure.
o Fixed improper calls to code that generates CmmLit's for strings
o New invariant on cg_loc in CgIdInfo: the expression is always tagged
o Code to load free vars on entry to a thunk was (wrongly) placed before
  the heap check.
o Some of the StgCmm code was redundantly passing around Id's
  along with CgIdInfo's; no more.
o Initialize the LocalReg's that point to a closure before allocating and
  initializing the closure itself -- otherwise, we have problems with
  recursive closure bindings
o BlockEnv and BlockSet types are now abstract.
o Update frames:
  - push arguments in Old call area
  - keep track of the return sp in the FCode monad
  - keep the return sp in every call, tail call, and return
      (because it might be different at different call sites,
       e.g. tail calls to the gc after a heap check are performed
            before pushing the update frame)
  - set the sp appropriately on returns and tail calls
o Reduce call, tail call, and return to a single LastCall node
o Added slow entry code, using different calling conventions on entry and tail call
o More fixes to the calling convention code.
  The tricky stuff is all about the closure environment: it must be passed in R1,
  but in non-closures, there is no such argument, so we can't treat all arguments
  the same way: the closure environment is special. Maybe the right step forward
  would be to define a different calling convention for closure arguments.
o Let-no-escapes need to be emitted out-of-line -- otherwise, we drop code.
o Respect RTS requirement of word alignment for pointers
  My stack allocation can pack sub-word values into a single word on the stack,
  but it wasn't requiring word-alignment for pointers. It does now,
  by word-aligning both pointer registers and call areas.
o CmmLint was over-aggresively ruling out non-word-aligned memory references,
  which may be kosher now that we can spill small values into a single word.
o Wrong label order on a conditional branch when compiling switches.
o void args weren't dropped in many cases.
  To help prevent this kind of mistake, I defined a NonVoid wrapper,
  which I'm applying only to Id's for now, although there are probably
  other good candidates.
o A little code refactoring: separate modules for procpoint analysis splitting, 
  stack layout, and building infotables.
o Stack limit check: insert along with the heap limit check, using a symbolic
  constant (a special CmmLit), then replace it when the stack layout is known.
o Removed last node: MidAddToContext 
o Adding block id as a literal: means that the lowering of the calling conventions
  no longer has to produce labels early, which was inhibiting common-block elimination.
  Will also make it easier for the non-procpoint-splitting path.
o Info tables: don't try to describe the update frame!
o Over aggressive use of NonVoid!!!!
  Don't drop the non-void args before setting the type of the closure!!!
o Sanity checking:
  Added a pass to stub dead dead slots on the stack
  (only ~10 lines with the dataflow framework)
o More sanity checking:
  Check that incoming pointer arguments are non-stubbed.
  Note: these checks are still subject to dead-code removal, but they should
  still be quite helpful.
o Better sanity checking: why stop at function arguments?
  Instead, in mkAssign, check that _any_ assignment to a pointer type is non-null
  -- the sooner the crash, the easier it is to debug.
  Still need to add the debugging flag to turn these checks on explicitly.
o Fixed yet another calling convention bug.
  This time, the calls to the GC were wrong. I've added a new convention
  for GC calls and invoked it where appropriate.
  We should really straighten out the calling convention stuff:
    some of the code (and documentation) is spread across the compiler,
    and there's some magical use of the node register that should really
    be handled (not avoided) by calling conventions.
o Switch bug: the arms in mkCmmLitSwitch weren't returning to a single join point.
o Environment shadowing problem in Stg->Cmm:
  When a closure f is bound at the top-level, we should not bind f to the
  node register on entry to the closure.
  Why? Because if the body of f contains a let-bound closure g that refers
  to f, we want to make sure that it refers to the static closure for f.
  Normally, this would all be fine, because when we compile a closure,
  we rebind free variables in the environment. But f doesn't look like
  a free variable because it's a static value. So, the binding for f
  remains in the environment when we compile g, inconveniently referring
  to the wrong thing.
  Now, I bind the variable in the local environment only if the closure is not
  bound at the top level. It's still okay to make assumptions about the
  node holding the closure environment; we just won't find the binding
  in the environment, so code that names the closure will now directly
  get the label of the static closure, not the node register holding a
  pointer to the static closure.
o Don't generate bogus Cmm code containing SRTs during the STG -> Cmm pass!
  The tables made reference to some labels that don't exist when we compute and
  generate the tables in the back end.
o Safe foreign calls need some special treatment (at least until we have the integrated
  codegen). In particular:
  o they need info tables
  o they are not procpoints -- the successor had better be in the same procedure
  o we cannot (yet) implement the calling conventions early, which means we have
    to carry the calling-conv info all the way to the end
o We weren't following the old convention when registering a module.
  Now, we use update frames to push any new modules that have to be registered
  and enter the youngest one on the stack.
  We also use the update frame machinery to specify that the return should pop
  the return address off the stack.
o At each safe foreign call, an infotable must be at the bottom of the stack,
  and the TSO->sp must point to it.
o More problems with void args in a direct call to a function:
  We were checking the args (minus voids) to check whether the call was saturated,
  which caused problems when the function really wasn't saturated because it
  took an extra void argument.
o Forgot to distinguish integer != from floating != during Stg->Cmm
o Updating slotEnv and areaMap to include safe foreign calls
  The dataflow analyses that produce the slotEnv and areaMap give
  results for each basic block, but we also need the results for
  a safe foreign call, which is a middle node.
  After running the dataflow analysis, we have another pass that
  updates the results to includ any safe foreign calls.
o Added a static flag for the debugging technique that inserts
  instructions to stub dead slots on the stack and crashes when
  a stubbed value is loaded into a pointer-typed LocalReg.
o C back end expects to see return continuations before their call sites.
  Sorted the flowgraphs appropriately after splitting.
o PrimOp calling conventions are special -- unlimited registers, no stack
  Yet another calling convention...
o More void value problems: if the RHS of a case arm is a void-typed variable,
  don't try to return it.
o When calling some primOp, they may allocate memory; if so, we need to
  do a heap check when we return from the call.

1 files changed, 69 insertions, 34 deletions

diff --git a/compiler/codeGen/StgCmmMonad.hs b/compiler/codeGen/StgCmmMonad.hs
index 365263941e..2249a463df 100644
--- a/compiler/codeGen/StgCmmMonad.hs
+++ b/compiler/codeGen/StgCmmMonad.hs
@@ -13,7 +13,7 @@ module StgCmmMonad (
 	returnFC, fixC, nopC, whenC, 
 	newUnique, newUniqSupply, 
 
-	emit, emitData, emitProc, emitSimpleProc,
+	emit, emitData, emitProc, emitProcWithConvention, emitSimpleProc,
 
 	getCmm, cgStmtsToBlocks,
 	getCodeR, getCode, getHeapUsage,
@@ -28,6 +28,8 @@ module StgCmmMonad (
 	setSRTLabel, getSRTLabel, 
 	setTickyCtrLabel, getTickyCtrLabel,
 
+	withUpdFrameOff, getUpdFrameOff, initUpdFrameOff,
+
 	HeapUsage(..), VirtualHpOffset,	initHpUsage,
 	getHpUsage,  setHpUsage, heapHWM,
 	setVirtHp, getVirtHp, setRealHp,
@@ -50,6 +52,7 @@ module StgCmmMonad (
 import StgCmmClosure
 import DynFlags
 import MkZipCfgCmm
+import ZipCfgCmmRep (UpdFrameOffset)
 import BlockId
 import Cmm
 import CLabel
@@ -157,12 +160,13 @@ fixC fcode = FCode (
 
 data CgInfoDownwards	-- information only passed *downwards* by the monad
   = MkCgInfoDown {
-	cgd_dflags  :: DynFlags,
-	cgd_mod     :: Module,		-- Module being compiled
-	cgd_statics :: CgBindings,	-- [Id -> info] : static environment
-	cgd_srt_lbl :: CLabel,		-- Label of the current top-level SRT
-	cgd_ticky   :: CLabel,		-- Current destination for ticky counts
-	cgd_sequel  :: Sequel		-- What to do at end of basic block
+	cgd_dflags     :: DynFlags,
+	cgd_mod        :: Module,	  -- Module being compiled
+	cgd_statics    :: CgBindings,	  -- [Id -> info] : static environment
+	cgd_srt_lbl    :: CLabel,	  -- Label of the current top-level SRT
+	cgd_updfr_off  :: UpdFrameOffset, -- Size of current update frame
+	cgd_ticky      :: CLabel,	  -- Current destination for ticky counts
+	cgd_sequel     :: Sequel	  -- What to do at end of basic block
   }
 
 type CgBindings = IdEnv CgIdInfo
@@ -173,10 +177,10 @@ data CgIdInfo
 			-- Can differ from the Id at occurrence sites by 
 			-- virtue of being externalised, for splittable C
 	, cg_lf  :: LambdaFormInfo 
-	, cg_loc :: CgLoc
+	, cg_loc :: CgLoc		     -- CmmExpr for the *tagged* value
 	, cg_rep :: PrimRep		     -- Cache for (idPrimRep id)
         , cg_tag :: {-# UNPACK #-} !DynTag   -- Cache for (lfDynTag cg_lf)
-         }
+        }
 
 data CgLoc
   = CmmLoc CmmExpr	-- A stable CmmExpr; that is, one not mentioning
@@ -206,21 +210,28 @@ data Sequel
 	[LocalReg]	-- Put result(s) in these regs and fall through
 			-- 	NB: no void arguments here
 	C_SRT		-- Here are the statics live in the continuation
-
+			-- E.g.  case (case x# of 0# -> a; DEFAULT -> b) of {
+			-- 	    r -> <blah>
+			-- When compiling the nested case, remember to put the
+			-- result in r, and fall through  
 
 
 initCgInfoDown :: DynFlags -> Module -> CgInfoDownwards
 initCgInfoDown dflags mod
-  = MkCgInfoDown {	cgd_dflags  = dflags,
-			cgd_mod     = mod,
-			cgd_statics = emptyVarEnv,
-			cgd_srt_lbl = error "initC: srt_lbl",
-			cgd_ticky   = mkTopTickyCtrLabel,
-			cgd_sequel  = initSequel }
+  = MkCgInfoDown {	cgd_dflags    = dflags,
+			cgd_mod       = mod,
+			cgd_statics   = emptyVarEnv,
+			cgd_srt_lbl   = error "initC: srt_lbl",
+			cgd_updfr_off = initUpdFrameOff,
+			cgd_ticky     = mkTopTickyCtrLabel,
+			cgd_sequel    = initSequel }
 
 initSequel :: Sequel
 initSequel = Return False
 
+initUpdFrameOff :: UpdFrameOffset
+initUpdFrameOff = widthInBytes wordWidth -- space for the RA
+
 
 --------------------------------------------------------
 --	The code generator state
@@ -240,7 +251,7 @@ data CgState
 				-- the info-down part
 
      cgs_hp_usg  :: HeapUsage,
-     
+
      cgs_uniqs :: UniqSupply }
 
 data HeapUsage =
@@ -253,10 +264,10 @@ type VirtualHpOffset = WordOff
 
 initCgState :: UniqSupply -> CgState
 initCgState uniqs
-  = MkCgState { cgs_stmts = mkNop, cgs_tops = nilOL,
-		cgs_binds = emptyVarEnv, 
-		cgs_hp_usg = initHpUsage,
-		cgs_uniqs = uniqs }
+  = MkCgState { cgs_stmts      = mkNop, cgs_tops = nilOL,
+		cgs_binds      = emptyVarEnv, 
+		cgs_hp_usg     = initHpUsage,
+		cgs_uniqs      = uniqs }
 
 stateIncUsage :: CgState -> CgState -> CgState
 -- stateIncUsage@ e1 e2 incorporates in e1 
@@ -408,6 +419,26 @@ setSRTLabel srt_lbl code
 	withInfoDown code (info { cgd_srt_lbl = srt_lbl})
 
 -- ----------------------------------------------------------------------------
+-- Get/set the size of the update frame
+
+-- We keep track of the size of the update frame so that we
+-- can set the stack pointer to the proper address on return
+-- (or tail call) from the closure.
+-- There should be at most one update frame for each closure.
+-- Note: I'm including the size of the original return address
+-- in the size of the update frame -- hence the default case on `get'.
+
+withUpdFrameOff :: UpdFrameOffset -> FCode () -> FCode ()
+withUpdFrameOff size code
+  = do	{ info  <- getInfoDown
+	; withInfoDown code (info {cgd_updfr_off = size }) }
+
+getUpdFrameOff :: FCode UpdFrameOffset
+getUpdFrameOff
+  = do	{ info  <- getInfoDown
+	; return $ cgd_updfr_off info }
+
+-- ----------------------------------------------------------------------------
 -- Get/set the current ticky counter label
 
 getTickyCtrLabel :: FCode CLabel
@@ -440,7 +471,8 @@ forkClosureBody body_code
   = do	{ info <- getInfoDown
 	; us   <- newUniqSupply
 	; state <- getState
-   	; let	body_info_down = info { cgd_sequel = initSequel }
+   	; let	body_info_down = info { cgd_sequel    = initSequel
+                                      , cgd_updfr_off = initUpdFrameOff }
 		fork_state_in = (initCgState us) { cgs_binds = cgs_binds state }
 		((),fork_state_out)
 		    = doFCode body_code body_info_down fork_state_in
@@ -455,8 +487,9 @@ forkStatics body_code
   = do	{ info  <- getInfoDown
 	; us    <- newUniqSupply
 	; state <- getState
-	; let	rhs_info_down = info { cgd_statics = cgs_binds state,
-				       cgd_sequel  = initSequel }
+	; let	rhs_info_down = info { cgd_statics = cgs_binds state
+				     , cgd_sequel  = initSequel 
+			             , cgd_updfr_off = initUpdFrameOff }
 		(result, fork_state_out) = doFCode body_code rhs_info_down 
 						   (initCgState us)
 	; setState (state `addCodeBlocksFrom` fork_state_out)
@@ -473,9 +506,9 @@ forkProc body_code
   = do	{ info_down <- getInfoDown
 	; us    <- newUniqSupply
 	; state <- getState
-	; let	fork_state_in = (initCgState us) 
-					{ cgs_binds = cgs_binds state }
-		(result, fork_state_out) = doFCode body_code info_down fork_state_in
+   	; let	info_down' = info_down { cgd_sequel = initSequel }
+                fork_state_in = (initCgState us) { cgs_binds = cgs_binds state }
+		(result, fork_state_out) = doFCode body_code info_down' fork_state_in
   	; setState $ state `addCodeBlocksFrom` fork_state_out
 	; return result }
 
@@ -562,20 +595,22 @@ emitData sect lits
   where
     data_block = CmmData sect lits
 
-emitProc :: CmmInfo -> CLabel -> CmmFormals -> CmmAGraph -> FCode ()
-emitProc info lbl args blocks
+emitProcWithConvention :: Convention -> CmmInfo -> CLabel -> CmmFormals ->
+                          CmmAGraph -> FCode ()
+emitProcWithConvention conv info lbl args blocks
   = do  { us <- newUniqSupply
-        ; let (offset, entry) = mkEntry (mkBlockId $ uniqFromSupply us) Native args
+        ; let (offset, entry) = mkEntry (mkBlockId $ uniqFromSupply us) conv args
               blks = initUs_ us $ lgraphOfAGraph offset $ entry <*> blocks
-        -- ; blks <- cgStmtsToBlocks blocks
         ; let proc_block = CmmProc info lbl args blks
         ; state <- getState
         ; setState $ state { cgs_tops = cgs_tops state `snocOL` proc_block } }
 
+emitProc :: CmmInfo -> CLabel -> CmmFormals -> CmmAGraph -> FCode ()
+emitProc = emitProcWithConvention Native
+
 emitSimpleProc :: CLabel -> CmmAGraph -> FCode ()
--- Emit a procedure whose body is the specified code; no info table
-emitSimpleProc lbl code
-  = emitProc (CmmInfo Nothing Nothing CmmNonInfoTable) lbl [] code
+emitSimpleProc lbl code = 
+  emitProc (CmmInfo Nothing Nothing CmmNonInfoTable) lbl [] code
 
 getCmm :: FCode () -> FCode CmmZ
 -- Get all the CmmTops (there should be no stmts)