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, 5 insertions, 6 deletions

diff --git a/compiler/codeGen/StgCmmHpc.hs b/compiler/codeGen/StgCmmHpc.hs
index fae3bef016..4465e30b04 100644
--- a/compiler/codeGen/StgCmmHpc.hs
+++ b/compiler/codeGen/StgCmmHpc.hs
@@ -11,11 +11,11 @@ module StgCmmHpc ( initHpc, mkTickBox ) where
 import StgCmmMonad
 
 import MkGraph
-import CmmDecl
 import CmmExpr
 import CLabel
 import Module
 import CmmUtils
+import StgCmmUtils
 import HscTypes
 import StaticFlags
 
@@ -36,9 +36,8 @@ initHpc _ (NoHpcInfo {})
   = 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 ..]
-              ]
+    do  { emitDataLits (mkHpcTicksLabel this_mod)
+                       [ (CmmInt 0 W64)
+                       | _ <- take tickCount [0::Int ..]
+                       ]
        }