Refactoring: use a structured CmmStatics type rather than [CmmStatic]

I observed that the [CmmStatics] within CmmData uses the list in a very stylised way.
The first item in the list is almost invariably a CmmDataLabel. Many parts of the
compiler pattern match on this list and fail if this is not true.

This patch makes the invariant explicit by introducing a structured type CmmStatics
that holds the label and the list of remaining [CmmStatic].

There is one wrinkle: the x86 backend sometimes wants to output an alignment directive just
before the label. However, this can be easily fixed up by parameterising the native codegen
over the type of CmmStatics (though the GenCmmTop parameterisation) and using a pair
(Alignment, CmmStatics) there instead.

As a result, I think we will be able to remove CmmAlign and CmmDataLabel from the CmmStatic
data type, thus nuking a lot of code and failing pattern matches. This change will come as part
of my next patch.

1 files changed, 18 insertions, 18 deletions

diff --git a/compiler/nativeGen/RegAlloc/Liveness.hs b/compiler/nativeGen/RegAlloc/Liveness.hs
index a2030fafa9..a6a3724bfa 100644
--- a/compiler/nativeGen/RegAlloc/Liveness.hs
+++ b/compiler/nativeGen/RegAlloc/Liveness.hs
@@ -66,9 +66,9 @@ type BlockMap a = BlockEnv a
 
 
 -- | A top level thing which carries liveness information.
-type LiveCmmTop instr
+type LiveCmmTop statics instr
 	= GenCmmTop
-		CmmStatic
+		statics
 		LiveInfo
 		[SCC (LiveBasicBlock instr)]
 
@@ -224,7 +224,7 @@ instance Outputable LiveInfo where
 --
 mapBlockTop
 	:: (LiveBasicBlock instr -> LiveBasicBlock instr)
-	-> LiveCmmTop instr -> LiveCmmTop instr
+	-> LiveCmmTop statics instr -> LiveCmmTop statics instr
 
 mapBlockTop f cmm
 	= evalState (mapBlockTopM (\x -> return $ f x) cmm) ()
@@ -235,7 +235,7 @@ mapBlockTop f cmm
 mapBlockTopM
 	:: Monad m
 	=> (LiveBasicBlock instr -> m (LiveBasicBlock instr))
-	-> LiveCmmTop instr -> m (LiveCmmTop instr)
+	-> LiveCmmTop statics instr -> m (LiveCmmTop statics instr)
 
 mapBlockTopM _ cmm@(CmmData{})
 	= return cmm
@@ -283,7 +283,7 @@ mapGenBlockTopM f (CmmProc header label (ListGraph blocks))
 --
 slurpConflicts 
 	:: Instruction instr
-	=> LiveCmmTop instr 
+	=> LiveCmmTop statics instr 
 	-> (Bag (UniqSet Reg), Bag (Reg, Reg))
 
 slurpConflicts live
@@ -357,8 +357,8 @@ slurpConflicts live
 --
 --
 slurpReloadCoalesce 
-	:: forall instr. Instruction instr
-	=> LiveCmmTop instr
+	:: forall statics instr. Instruction instr
+	=> LiveCmmTop statics instr
 	-> Bag (Reg, Reg)
 
 slurpReloadCoalesce live
@@ -458,9 +458,9 @@ slurpReloadCoalesce live
 
 -- | Strip away liveness information, yielding NatCmmTop
 stripLive 
-	:: (Outputable instr, Instruction instr)
-	=> LiveCmmTop instr 
-	-> NatCmmTop instr
+	:: (Outputable statics, Outputable instr, Instruction instr)
+	=> LiveCmmTop statics instr 
+	-> NatCmmTop statics instr
 
 stripLive live
 	= stripCmm live
@@ -525,8 +525,8 @@ stripLiveBlock (BasicBlock i lis)
 
 eraseDeltasLive 
 	:: Instruction instr
-	=> LiveCmmTop instr
-	-> LiveCmmTop instr
+	=> LiveCmmTop statics instr
+	-> LiveCmmTop statics instr
 
 eraseDeltasLive cmm
 	= mapBlockTop eraseBlock cmm
@@ -543,7 +543,7 @@ eraseDeltasLive cmm
 patchEraseLive
 	:: Instruction instr
 	=> (Reg -> Reg)
-	-> LiveCmmTop instr -> LiveCmmTop instr
+	-> LiveCmmTop statics instr -> LiveCmmTop statics instr
 
 patchEraseLive patchF cmm
 	= patchCmm cmm
@@ -620,8 +620,8 @@ patchRegsLiveInstr patchF li
 
 natCmmTopToLive 
 	:: Instruction instr
-	=> NatCmmTop instr
-	-> LiveCmmTop instr
+	=> NatCmmTop statics instr
+	-> LiveCmmTop statics instr
 
 natCmmTopToLive (CmmData i d)
 	= CmmData i d
@@ -658,8 +658,8 @@ sccBlocks blocks = stronglyConnCompFromEdgedVertices graph
 --
 regLiveness
 	:: (Outputable instr, Instruction instr)
-	=> LiveCmmTop instr
-	-> UniqSM (LiveCmmTop instr)
+	=> LiveCmmTop statics instr
+	-> UniqSM (LiveCmmTop statics instr)
 
 regLiveness (CmmData i d)
 	= returnUs $ CmmData i d
@@ -720,7 +720,7 @@ checkIsReverseDependent sccs'
 
 -- | If we've compute liveness info for this code already we have to reverse
 --   the SCCs in each top to get them back to the right order so we can do it again.
-reverseBlocksInTops :: LiveCmmTop instr -> LiveCmmTop instr
+reverseBlocksInTops :: LiveCmmTop statics instr -> LiveCmmTop statics instr
 reverseBlocksInTops top
  = case top of
 	CmmData{}			-> top