A little import wrangling. Not much accomplishedwip/lower-parser-deps

23 files changed, 312 insertions, 292 deletions

diff --git a/compiler/GHC/ByteCode/Asm.hs b/compiler/GHC/ByteCode/Asm.hs
index 6b9d4a9223..f5b1f14661 100644
--- a/compiler/GHC/ByteCode/Asm.hs
+++ b/compiler/GHC/ByteCode/Asm.hs
@@ -39,7 +39,8 @@ import GHC.Data.FastString
 import GHC.Data.SizedSeq
 
 import GHC.StgToCmm.Layout     ( ArgRep(..) )
-import GHC.Cmm.Expr
+import GHC.Cmm.Reg.Global
+import GHC.Cmm.Reg.Set
 import GHC.Cmm.CallConv        ( tupleRegsCover )
 import GHC.Platform
 import GHC.Platform.Profile
diff --git a/compiler/GHC/ByteCode/Types.hs b/compiler/GHC/ByteCode/Types.hs
index 673838654d..6cc53826d2 100644
--- a/compiler/GHC/ByteCode/Types.hs
+++ b/compiler/GHC/ByteCode/Types.hs
@@ -43,7 +43,8 @@ import qualified Data.IntMap as IntMap
 import Data.Maybe (catMaybes)
 import qualified GHC.Exts.Heap as Heap
 import GHC.Stack.CCS
-import GHC.Cmm.Expr ( GlobalRegSet, emptyRegSet, regSetToList )
+import GHC.Cmm.Reg.Set ( emptyRegSet, regSetToList )
+import GHC.Cmm.Reg.Global ( GlobalRegSet )
 
 -- -----------------------------------------------------------------------------
 -- Compiled Byte Code
diff --git a/compiler/GHC/Cmm.hs b/compiler/GHC/Cmm.hs
index 3a461fa03c..fdaa8ce624 100644
--- a/compiler/GHC/Cmm.hs
+++ b/compiler/GHC/Cmm.hs
@@ -30,6 +30,7 @@ module GHC.Cmm (
      -- * Statements, expressions and types
      module GHC.Cmm.Node,
      module GHC.Cmm.Expr,
+     module GHC.Cmm.Reg.Global
   ) where
 
 import GHC.Prelude
@@ -45,6 +46,7 @@ import GHC.Cmm.Dataflow.Block
 import GHC.Cmm.Dataflow.Collections
 import GHC.Cmm.Dataflow.Graph
 import GHC.Cmm.Dataflow.Label
+import GHC.Cmm.Reg.Global
 import GHC.Utils.Outputable
 import Data.ByteString (ByteString)
 
@@ -288,4 +290,3 @@ instance OutputableP env instr => OutputableP env (GenBasicBlock instr) where
 pprBBlock :: Outputable stmt => GenBasicBlock stmt -> SDoc
 pprBBlock (BasicBlock ident stmts) =
     hang (ppr ident <> colon) 4 (vcat (map ppr stmts))
-
diff --git a/compiler/GHC/Cmm/CallConv.hs b/compiler/GHC/Cmm/CallConv.hs
index f376e598bf..378248640d 100644
--- a/compiler/GHC/Cmm/CallConv.hs
+++ b/compiler/GHC/Cmm/CallConv.hs
@@ -10,6 +10,7 @@ import GHC.Prelude
 import Data.List (nub)
 
 import GHC.Cmm.Expr
+import GHC.Cmm.Reg.Global
 import GHC.Runtime.Heap.Layout
 import GHC.Cmm (Convention(..))
 import GHC.Cmm.Ppr () -- For Outputable instances
diff --git a/compiler/GHC/Cmm/Expr.hs b/compiler/GHC/Cmm/Expr.hs
index 86b06271d1..7f94f3f3dd 100644
--- a/compiler/GHC/Cmm/Expr.hs
+++ b/compiler/GHC/Cmm/Expr.hs
@@ -9,22 +9,16 @@ module GHC.Cmm.Expr
     ( CmmExpr(..), cmmExprType, cmmExprWidth, cmmExprAlignment, maybeInvertCmmExpr
     , CmmReg(..), cmmRegType, cmmRegWidth
     , CmmLit(..), cmmLitType
-    , LocalReg(..), localRegType
-    , GlobalReg(..), isArgReg, globalRegType
+    , LocalReg(..), LocalRegSet, localRegType
+    , globalRegType
     , spReg, hpReg, spLimReg, hpLimReg, nodeReg
     , currentTSOReg, currentNurseryReg, hpAllocReg, cccsReg
-    , node, baseReg
-    , VGcPtr(..)
+    , baseReg
 
     , DefinerOfRegs, UserOfRegs
     , foldRegsDefd, foldRegsUsed
     , foldLocalRegsDefd, foldLocalRegsUsed
 
-    , RegSet, LocalRegSet, GlobalRegSet
-    , emptyRegSet, elemRegSet, extendRegSet, deleteFromRegSet, mkRegSet
-    , plusRegSet, minusRegSet, timesRegSet, sizeRegSet, nullRegSet
-    , regSetToList
-
     , Area(..)
     , module GHC.Cmm.MachOp
     , module GHC.Cmm.Type
@@ -34,6 +28,8 @@ where
 import GHC.Prelude
 
 import GHC.Platform
+import GHC.Cmm.Reg.Global
+import GHC.Cmm.Reg.Set
 import GHC.Cmm.BlockId
 import GHC.Cmm.CLabel
 import GHC.Cmm.MachOp
@@ -42,9 +38,6 @@ import GHC.Utils.Panic (panic)
 import GHC.Utils.Outputable
 import GHC.Types.Unique
 
-import Data.Set (Set)
-import qualified Data.Set as Set
-
 import GHC.Types.Basic (Alignment, mkAlignment, alignmentOf)
 
 -----------------------------------------------------------------------------
@@ -280,6 +273,8 @@ data LocalReg
     --   1. Identifier
     --   2. Type
 
+type LocalRegSet  = RegSet LocalReg
+
 instance Eq LocalReg where
   (LocalReg u1 _) == (LocalReg u2 _) = u1 == u2
 
@@ -306,40 +301,6 @@ localRegType (LocalReg _ rep) = rep
 --    Register-use information for expressions and other types
 -----------------------------------------------------------------------------
 
--- | Sets of registers
-
--- These are used for dataflow facts, and a common operation is taking
--- the union of two RegSets and then asking whether the union is the
--- same as one of the inputs.  UniqSet isn't good here, because
--- sizeUniqSet is O(n) whereas Set.size is O(1), so we use ordinary
--- Sets.
-
-type RegSet r     = Set r
-type LocalRegSet  = RegSet LocalReg
-type GlobalRegSet = RegSet GlobalReg
-
-emptyRegSet             :: RegSet r
-nullRegSet              :: RegSet r -> Bool
-elemRegSet              :: Ord r => r -> RegSet r -> Bool
-extendRegSet            :: Ord r => RegSet r -> r -> RegSet r
-deleteFromRegSet        :: Ord r => RegSet r -> r -> RegSet r
-mkRegSet                :: Ord r => [r] -> RegSet r
-minusRegSet, plusRegSet, timesRegSet :: Ord r => RegSet r -> RegSet r -> RegSet r
-sizeRegSet              :: RegSet r -> Int
-regSetToList            :: RegSet r -> [r]
-
-emptyRegSet      = Set.empty
-nullRegSet       = Set.null
-elemRegSet       = Set.member
-extendRegSet     = flip Set.insert
-deleteFromRegSet = flip Set.delete
-mkRegSet         = Set.fromList
-minusRegSet      = Set.difference
-plusRegSet       = Set.union
-timesRegSet      = Set.intersection
-sizeRegSet       = Set.size
-regSetToList     = Set.toList
-
 class Ord r => UserOfRegs r a where
   foldRegsUsed :: Platform -> (b -> r -> b) -> b -> a -> b
 
@@ -397,217 +358,6 @@ instance DefinerOfRegs r a => DefinerOfRegs r [a] where
   foldRegsDefd platform f set as = foldl' (foldRegsDefd platform f) set as
   {-# INLINABLE foldRegsDefd #-}
 
------------------------------------------------------------------------------
---              Global STG registers
------------------------------------------------------------------------------
-
-data VGcPtr = VGcPtr | VNonGcPtr deriving( Eq, Show )
-
------------------------------------------------------------------------------
---              Global STG registers
------------------------------------------------------------------------------
-{-
-Note [Overlapping global registers]
-
-The backend might not faithfully implement the abstraction of the STG
-machine with independent registers for different values of type
-GlobalReg. Specifically, certain pairs of registers (r1, r2) may
-overlap in the sense that a store to r1 invalidates the value in r2,
-and vice versa.
-
-Currently this occurs only on the x86_64 architecture where FloatReg n
-and DoubleReg n are assigned the same microarchitectural register, in
-order to allow functions to receive more Float# or Double# arguments
-in registers (as opposed to on the stack).
-
-There are no specific rules about which registers might overlap with
-which other registers, but presumably it's safe to assume that nothing
-will overlap with special registers like Sp or BaseReg.
-
-Use GHC.Cmm.Utils.regsOverlap to determine whether two GlobalRegs overlap
-on a particular platform. The instance Eq GlobalReg is syntactic
-equality of STG registers and does not take overlap into
-account. However it is still used in UserOfRegs/DefinerOfRegs and
-there are likely still bugs there, beware!
--}
-
-data GlobalReg
-  -- Argument and return registers
-  = VanillaReg                  -- pointers, unboxed ints and chars
-        {-# UNPACK #-} !Int     -- its number
-        VGcPtr
-
-  | FloatReg            -- single-precision floating-point registers
-        {-# UNPACK #-} !Int     -- its number
-
-  | DoubleReg           -- double-precision floating-point registers
-        {-# UNPACK #-} !Int     -- its number
-
-  | LongReg             -- long int registers (64-bit, really)
-        {-# UNPACK #-} !Int     -- its number
-
-  | XmmReg                      -- 128-bit SIMD vector register
-        {-# UNPACK #-} !Int     -- its number
-
-  | YmmReg                      -- 256-bit SIMD vector register
-        {-# UNPACK #-} !Int     -- its number
-
-  | ZmmReg                      -- 512-bit SIMD vector register
-        {-# UNPACK #-} !Int     -- its number
-
-  -- STG registers
-  | Sp                  -- Stack ptr; points to last occupied stack location.
-  | SpLim               -- Stack limit
-  | Hp                  -- Heap ptr; points to last occupied heap location.
-  | HpLim               -- Heap limit register
-  | CCCS                -- Current cost-centre stack
-  | CurrentTSO          -- pointer to current thread's TSO
-  | CurrentNursery      -- pointer to allocation area
-  | HpAlloc             -- allocation count for heap check failure
-
-                -- We keep the address of some commonly-called
-                -- functions in the register table, to keep code
-                -- size down:
-  | EagerBlackholeInfo  -- stg_EAGER_BLACKHOLE_info
-  | GCEnter1            -- stg_gc_enter_1
-  | GCFun               -- stg_gc_fun
-
-  -- Base offset for the register table, used for accessing registers
-  -- which do not have real registers assigned to them.  This register
-  -- will only appear after we have expanded GlobalReg into memory accesses
-  -- (where necessary) in the native code generator.
-  | BaseReg
-
-  -- The register used by the platform for the C stack pointer. This is
-  -- a break in the STG abstraction used exclusively to setup stack unwinding
-  -- information.
-  | MachSp
-
-  -- The is a dummy register used to indicate to the stack unwinder where
-  -- a routine would return to.
-  | UnwindReturnReg
-
-  -- Base Register for PIC (position-independent code) calculations
-  -- Only used inside the native code generator. It's exact meaning differs
-  -- from platform to platform (see module PositionIndependentCode).
-  | PicBaseReg
-
-  deriving( Show )
-
-instance Eq GlobalReg where
-   VanillaReg i _ == VanillaReg j _ = i==j -- Ignore type when seeking clashes
-   FloatReg i == FloatReg j = i==j
-   DoubleReg i == DoubleReg j = i==j
-   LongReg i == LongReg j = i==j
-   -- NOTE: XMM, YMM, ZMM registers actually are the same registers
-   -- at least with respect to store at YMM i and then read from XMM i
-   -- and similarly for ZMM etc.
-   XmmReg i == XmmReg j = i==j
-   YmmReg i == YmmReg j = i==j
-   ZmmReg i == ZmmReg j = i==j
-   Sp == Sp = True
-   SpLim == SpLim = True
-   Hp == Hp = True
-   HpLim == HpLim = True
-   CCCS == CCCS = True
-   CurrentTSO == CurrentTSO = True
-   CurrentNursery == CurrentNursery = True
-   HpAlloc == HpAlloc = True
-   EagerBlackholeInfo == EagerBlackholeInfo = True
-   GCEnter1 == GCEnter1 = True
-   GCFun == GCFun = True
-   BaseReg == BaseReg = True
-   MachSp == MachSp = True
-   UnwindReturnReg == UnwindReturnReg = True
-   PicBaseReg == PicBaseReg = True
-   _r1 == _r2 = False
-
--- NOTE: this Ord instance affects the tuple layout in GHCi, see
---       Note [GHCi tuple layout]
-instance Ord GlobalReg where
-   compare (VanillaReg i _) (VanillaReg j _) = compare i j
-     -- Ignore type when seeking clashes
-   compare (FloatReg i)  (FloatReg  j) = compare i j
-   compare (DoubleReg i) (DoubleReg j) = compare i j
-   compare (LongReg i)   (LongReg   j) = compare i j
-   compare (XmmReg i)    (XmmReg    j) = compare i j
-   compare (YmmReg i)    (YmmReg    j) = compare i j
-   compare (ZmmReg i)    (ZmmReg    j) = compare i j
-   compare Sp Sp = EQ
-   compare SpLim SpLim = EQ
-   compare Hp Hp = EQ
-   compare HpLim HpLim = EQ
-   compare CCCS CCCS = EQ
-   compare CurrentTSO CurrentTSO = EQ
-   compare CurrentNursery CurrentNursery = EQ
-   compare HpAlloc HpAlloc = EQ
-   compare EagerBlackholeInfo EagerBlackholeInfo = EQ
-   compare GCEnter1 GCEnter1 = EQ
-   compare GCFun GCFun = EQ
-   compare BaseReg BaseReg = EQ
-   compare MachSp MachSp = EQ
-   compare UnwindReturnReg UnwindReturnReg = EQ
-   compare PicBaseReg PicBaseReg = EQ
-   compare (VanillaReg _ _) _ = LT
-   compare _ (VanillaReg _ _) = GT
-   compare (FloatReg _) _     = LT
-   compare _ (FloatReg _)     = GT
-   compare (DoubleReg _) _    = LT
-   compare _ (DoubleReg _)    = GT
-   compare (LongReg _) _      = LT
-   compare _ (LongReg _)      = GT
-   compare (XmmReg _) _       = LT
-   compare _ (XmmReg _)       = GT
-   compare (YmmReg _) _       = LT
-   compare _ (YmmReg _)       = GT
-   compare (ZmmReg _) _       = LT
-   compare _ (ZmmReg _)       = GT
-   compare Sp _ = LT
-   compare _ Sp = GT
-   compare SpLim _ = LT
-   compare _ SpLim = GT
-   compare Hp _ = LT
-   compare _ Hp = GT
-   compare HpLim _ = LT
-   compare _ HpLim = GT
-   compare CCCS _ = LT
-   compare _ CCCS = GT
-   compare CurrentTSO _ = LT
-   compare _ CurrentTSO = GT
-   compare CurrentNursery _ = LT
-   compare _ CurrentNursery = GT
-   compare HpAlloc _ = LT
-   compare _ HpAlloc = GT
-   compare GCEnter1 _ = LT
-   compare _ GCEnter1 = GT
-   compare GCFun _ = LT
-   compare _ GCFun = GT
-   compare BaseReg _ = LT
-   compare _ BaseReg = GT
-   compare MachSp _ = LT
-   compare _ MachSp = GT
-   compare UnwindReturnReg _ = LT
-   compare _ UnwindReturnReg = GT
-   compare EagerBlackholeInfo _ = LT
-   compare _ EagerBlackholeInfo = GT
-
--- convenient aliases
-baseReg, spReg, hpReg, spLimReg, hpLimReg, nodeReg,
-  currentTSOReg, currentNurseryReg, hpAllocReg, cccsReg  :: CmmReg
-baseReg = CmmGlobal BaseReg
-spReg = CmmGlobal Sp
-hpReg = CmmGlobal Hp
-hpLimReg = CmmGlobal HpLim
-spLimReg = CmmGlobal SpLim
-nodeReg = CmmGlobal node
-currentTSOReg = CmmGlobal CurrentTSO
-currentNurseryReg = CmmGlobal CurrentNursery
-hpAllocReg = CmmGlobal HpAlloc
-cccsReg = CmmGlobal CCCS
-
-node :: GlobalReg
-node = VanillaReg 1 VGcPtr
-
 globalRegType :: Platform -> GlobalReg -> CmmType
 globalRegType platform = \case
    (VanillaReg _ VGcPtr)    -> gcWord platform
@@ -626,12 +376,16 @@ globalRegType platform = \case
                                  -- dynamically allocated closures
    _          -> bWord platform
 
-isArgReg :: GlobalReg -> Bool
-isArgReg (VanillaReg {}) = True
-isArgReg (FloatReg {})   = True
-isArgReg (DoubleReg {})  = True
-isArgReg (LongReg {})    = True
-isArgReg (XmmReg {})     = True
-isArgReg (YmmReg {})     = True
-isArgReg (ZmmReg {})     = True
-isArgReg _               = False
+-- convenient aliases
+baseReg, spReg, hpReg, spLimReg, hpLimReg, nodeReg,
+  currentTSOReg, currentNurseryReg, hpAllocReg, cccsReg  :: CmmReg
+baseReg = CmmGlobal BaseReg
+spReg = CmmGlobal Sp
+hpReg = CmmGlobal Hp
+hpLimReg = CmmGlobal HpLim
+spLimReg = CmmGlobal SpLim
+nodeReg = CmmGlobal node
+currentTSOReg = CmmGlobal CurrentTSO
+currentNurseryReg = CmmGlobal CurrentNursery
+hpAllocReg = CmmGlobal HpAlloc
+cccsReg = CmmGlobal CCCS
diff --git a/compiler/GHC/Cmm/LayoutStack.hs b/compiler/GHC/Cmm/LayoutStack.hs
index b996427bba..d2fe6aeb98 100644
--- a/compiler/GHC/Cmm/LayoutStack.hs
+++ b/compiler/GHC/Cmm/LayoutStack.hs
@@ -19,6 +19,7 @@ import GHC.Cmm.Utils
 import GHC.Cmm.Graph
 import GHC.Cmm.Liveness
 import GHC.Cmm.ProcPoint
+import GHC.Cmm.Reg.Set
 import GHC.Runtime.Heap.Layout
 import GHC.Cmm.Dataflow.Block
 import GHC.Cmm.Dataflow.Collections
diff --git a/compiler/GHC/Cmm/Lexer.x b/compiler/GHC/Cmm/Lexer.x
index bf379ec7da..44f989a5bf 100644
--- a/compiler/GHC/Cmm/Lexer.x
+++ b/compiler/GHC/Cmm/Lexer.x
@@ -17,7 +17,7 @@ module GHC.Cmm.Lexer (
 
 import GHC.Prelude
 
-import GHC.Cmm.Expr
+import GHC.Cmm.Reg.Global
 
 import GHC.Parser.Lexer
 import GHC.Cmm.Parser.Monad
diff --git a/compiler/GHC/Cmm/Liveness.hs b/compiler/GHC/Cmm/Liveness.hs
index f047ea4367..b4d8f6d5b6 100644
--- a/compiler/GHC/Cmm/Liveness.hs
+++ b/compiler/GHC/Cmm/Liveness.hs
@@ -26,6 +26,7 @@ import GHC.Cmm.Dataflow.Collections
 import GHC.Cmm.Dataflow
 import GHC.Cmm.Dataflow.Label
 import GHC.Cmm.LRegSet
+import GHC.Cmm.Reg.Set
 
 import GHC.Data.Maybe
 import GHC.Utils.Outputable
@@ -159,5 +160,3 @@ xferLiveL platform (BlockCC eNode middle xNode) fBase =
     let joined = gen_killL platform xNode $! joinOutFacts liveLatticeL xNode fBase
         !result = foldNodesBwdOO (gen_killL platform) middle joined
     in mapSingleton (entryLabel eNode) result
-
-
diff --git a/compiler/GHC/Cmm/Node.hs b/compiler/GHC/Cmm/Node.hs
index fe6eac3223..9988e2210c 100644
--- a/compiler/GHC/Cmm/Node.hs
+++ b/compiler/GHC/Cmm/Node.hs
@@ -29,6 +29,7 @@ import GHC.Prelude hiding (succ)
 
 import GHC.Platform.Regs
 import GHC.Cmm.Expr
+import GHC.Cmm.Reg.Global
 import GHC.Cmm.Switch
 import GHC.Data.FastString
 import GHC.Types.ForeignCall
diff --git a/compiler/GHC/Cmm/Ppr/Expr.hs b/compiler/GHC/Cmm/Ppr/Expr.hs
index c656c98522..44b09dbf32 100644
--- a/compiler/GHC/Cmm/Ppr/Expr.hs
+++ b/compiler/GHC/Cmm/Ppr/Expr.hs
@@ -48,6 +48,7 @@ import GHC.Driver.Ppr
 
 import GHC.Platform
 import GHC.Cmm.Expr
+import GHC.Cmm.Reg.Global
 
 import GHC.Utils.Outputable
 
diff --git a/compiler/GHC/Cmm/ProcPoint.hs b/compiler/GHC/Cmm/ProcPoint.hs
index 0cabea1536..10ea7df8a9 100644
--- a/compiler/GHC/Cmm/ProcPoint.hs
+++ b/compiler/GHC/Cmm/ProcPoint.hs
@@ -22,6 +22,7 @@ import GHC.Cmm.Utils
 import GHC.Cmm.Info
 import GHC.Cmm.Liveness
 import GHC.Cmm.Switch
+import GHC.Cmm.Reg.Set
 import Data.List (sortBy)
 import GHC.Data.Maybe
 import Control.Monad
diff --git a/compiler/GHC/Cmm/Reg/Global.hs b/compiler/GHC/Cmm/Reg/Global.hs
new file mode 100644
index 0000000000..8bf0220fc0
--- /dev/null
+++ b/compiler/GHC/Cmm/Reg/Global.hs
@@ -0,0 +1,217 @@
+module GHC.Cmm.Reg.Global (
+    GlobalReg(..), GlobalRegSet, isArgReg, node
+  , VGcPtr(..)
+  ) where
+
+import GHC.Prelude
+
+import GHC.Cmm.Reg.Set
+
+-----------------------------------------------------------------------------
+--              Global STG registers
+-----------------------------------------------------------------------------
+
+data VGcPtr = VGcPtr | VNonGcPtr deriving( Eq, Show )
+
+-----------------------------------------------------------------------------
+--              Global STG registers
+-----------------------------------------------------------------------------
+{-
+Note [Overlapping global registers]
+
+The backend might not faithfully implement the abstraction of the STG
+machine with independent registers for different values of type
+GlobalReg. Specifically, certain pairs of registers (r1, r2) may
+overlap in the sense that a store to r1 invalidates the value in r2,
+and vice versa.
+
+Currently this occurs only on the x86_64 architecture where FloatReg n
+and DoubleReg n are assigned the same microarchitectural register, in
+order to allow functions to receive more Float# or Double# arguments
+in registers (as opposed to on the stack).
+
+There are no specific rules about which registers might overlap with
+which other registers, but presumably it's safe to assume that nothing
+will overlap with special registers like Sp or BaseReg.
+
+Use GHC.Cmm.Utils.regsOverlap to determine whether two GlobalRegs overlap
+on a particular platform. The instance Eq GlobalReg is syntactic
+equality of STG registers and does not take overlap into
+account. However it is still used in UserOfRegs/DefinerOfRegs and
+there are likely still bugs there, beware!
+-}
+
+data GlobalReg
+  -- Argument and return registers
+  = VanillaReg                  -- pointers, unboxed ints and chars
+        {-# UNPACK #-} !Int     -- its number
+        VGcPtr
+
+  | FloatReg            -- single-precision floating-point registers
+        {-# UNPACK #-} !Int     -- its number
+
+  | DoubleReg           -- double-precision floating-point registers
+        {-# UNPACK #-} !Int     -- its number
+
+  | LongReg             -- long int registers (64-bit, really)
+        {-# UNPACK #-} !Int     -- its number
+
+  | XmmReg                      -- 128-bit SIMD vector register
+        {-# UNPACK #-} !Int     -- its number
+
+  | YmmReg                      -- 256-bit SIMD vector register
+        {-# UNPACK #-} !Int     -- its number
+
+  | ZmmReg                      -- 512-bit SIMD vector register
+        {-# UNPACK #-} !Int     -- its number
+
+  -- STG registers
+  | Sp                  -- Stack ptr; points to last occupied stack location.
+  | SpLim               -- Stack limit
+  | Hp                  -- Heap ptr; points to last occupied heap location.
+  | HpLim               -- Heap limit register
+  | CCCS                -- Current cost-centre stack
+  | CurrentTSO          -- pointer to current thread's TSO
+  | CurrentNursery      -- pointer to allocation area
+  | HpAlloc             -- allocation count for heap check failure
+
+                -- We keep the address of some commonly-called
+                -- functions in the register table, to keep code
+                -- size down:
+  | EagerBlackholeInfo  -- stg_EAGER_BLACKHOLE_info
+  | GCEnter1            -- stg_gc_enter_1
+  | GCFun               -- stg_gc_fun
+
+  -- Base offset for the register table, used for accessing registers
+  -- which do not have real registers assigned to them.  This register
+  -- will only appear after we have expanded GlobalReg into memory accesses
+  -- (where necessary) in the native code generator.
+  | BaseReg
+
+  -- The register used by the platform for the C stack pointer. This is
+  -- a break in the STG abstraction used exclusively to setup stack unwinding
+  -- information.
+  | MachSp
+
+  -- The is a dummy register used to indicate to the stack unwinder where
+  -- a routine would return to.
+  | UnwindReturnReg
+
+  -- Base Register for PIC (position-independent code) calculations
+  -- Only used inside the native code generator. It's exact meaning differs
+  -- from platform to platform (see module PositionIndependentCode).
+  | PicBaseReg
+
+  deriving( Show )
+
+type GlobalRegSet = RegSet GlobalReg
+
+instance Eq GlobalReg where
+   VanillaReg i _ == VanillaReg j _ = i==j -- Ignore type when seeking clashes
+   FloatReg i == FloatReg j = i==j
+   DoubleReg i == DoubleReg j = i==j
+   LongReg i == LongReg j = i==j
+   -- NOTE: XMM, YMM, ZMM registers actually are the same registers
+   -- at least with respect to store at YMM i and then read from XMM i
+   -- and similarly for ZMM etc.
+   XmmReg i == XmmReg j = i==j
+   YmmReg i == YmmReg j = i==j
+   ZmmReg i == ZmmReg j = i==j
+   Sp == Sp = True
+   SpLim == SpLim = True
+   Hp == Hp = True
+   HpLim == HpLim = True
+   CCCS == CCCS = True
+   CurrentTSO == CurrentTSO = True
+   CurrentNursery == CurrentNursery = True
+   HpAlloc == HpAlloc = True
+   EagerBlackholeInfo == EagerBlackholeInfo = True
+   GCEnter1 == GCEnter1 = True
+   GCFun == GCFun = True
+   BaseReg == BaseReg = True
+   MachSp == MachSp = True
+   UnwindReturnReg == UnwindReturnReg = True
+   PicBaseReg == PicBaseReg = True
+   _r1 == _r2 = False
+
+-- NOTE: this Ord instance affects the tuple layout in GHCi, see
+--       Note [GHCi tuple layout]
+instance Ord GlobalReg where
+   compare (VanillaReg i _) (VanillaReg j _) = compare i j
+     -- Ignore type when seeking clashes
+   compare (FloatReg i)  (FloatReg  j) = compare i j
+   compare (DoubleReg i) (DoubleReg j) = compare i j
+   compare (LongReg i)   (LongReg   j) = compare i j
+   compare (XmmReg i)    (XmmReg    j) = compare i j
+   compare (YmmReg i)    (YmmReg    j) = compare i j
+   compare (ZmmReg i)    (ZmmReg    j) = compare i j
+   compare Sp Sp = EQ
+   compare SpLim SpLim = EQ
+   compare Hp Hp = EQ
+   compare HpLim HpLim = EQ
+   compare CCCS CCCS = EQ
+   compare CurrentTSO CurrentTSO = EQ
+   compare CurrentNursery CurrentNursery = EQ
+   compare HpAlloc HpAlloc = EQ
+   compare EagerBlackholeInfo EagerBlackholeInfo = EQ
+   compare GCEnter1 GCEnter1 = EQ
+   compare GCFun GCFun = EQ
+   compare BaseReg BaseReg = EQ
+   compare MachSp MachSp = EQ
+   compare UnwindReturnReg UnwindReturnReg = EQ
+   compare PicBaseReg PicBaseReg = EQ
+   compare (VanillaReg _ _) _ = LT
+   compare _ (VanillaReg _ _) = GT
+   compare (FloatReg _) _     = LT
+   compare _ (FloatReg _)     = GT
+   compare (DoubleReg _) _    = LT
+   compare _ (DoubleReg _)    = GT
+   compare (LongReg _) _      = LT
+   compare _ (LongReg _)      = GT
+   compare (XmmReg _) _       = LT
+   compare _ (XmmReg _)       = GT
+   compare (YmmReg _) _       = LT
+   compare _ (YmmReg _)       = GT
+   compare (ZmmReg _) _       = LT
+   compare _ (ZmmReg _)       = GT
+   compare Sp _ = LT
+   compare _ Sp = GT
+   compare SpLim _ = LT
+   compare _ SpLim = GT
+   compare Hp _ = LT
+   compare _ Hp = GT
+   compare HpLim _ = LT
+   compare _ HpLim = GT
+   compare CCCS _ = LT
+   compare _ CCCS = GT
+   compare CurrentTSO _ = LT
+   compare _ CurrentTSO = GT
+   compare CurrentNursery _ = LT
+   compare _ CurrentNursery = GT
+   compare HpAlloc _ = LT
+   compare _ HpAlloc = GT
+   compare GCEnter1 _ = LT
+   compare _ GCEnter1 = GT
+   compare GCFun _ = LT
+   compare _ GCFun = GT
+   compare BaseReg _ = LT
+   compare _ BaseReg = GT
+   compare MachSp _ = LT
+   compare _ MachSp = GT
+   compare UnwindReturnReg _ = LT
+   compare _ UnwindReturnReg = GT
+   compare EagerBlackholeInfo _ = LT
+   compare _ EagerBlackholeInfo = GT
+
+node :: GlobalReg
+node = VanillaReg 1 VGcPtr
+
+isArgReg :: GlobalReg -> Bool
+isArgReg (VanillaReg {}) = True
+isArgReg (FloatReg {})   = True
+isArgReg (DoubleReg {})  = True
+isArgReg (LongReg {})    = True
+isArgReg (XmmReg {})     = True
+isArgReg (YmmReg {})     = True
+isArgReg (ZmmReg {})     = True
+isArgReg _               = False
diff --git a/compiler/GHC/Cmm/Reg/Set.hs b/compiler/GHC/Cmm/Reg/Set.hs
new file mode 100644
index 0000000000..5d6ec5e93f
--- /dev/null
+++ b/compiler/GHC/Cmm/Reg/Set.hs
@@ -0,0 +1,43 @@
+module GHC.Cmm.Reg.Set (
+      RegSet
+    , emptyRegSet, elemRegSet, extendRegSet, deleteFromRegSet, mkRegSet
+    , plusRegSet, minusRegSet, timesRegSet, sizeRegSet, nullRegSet
+    , regSetToList
+  ) where
+
+import GHC.Prelude
+
+import           Data.Set ( Set )
+import qualified Data.Set as Set
+
+-- | Sets of registers
+
+-- These are used for dataflow facts, and a common operation is taking
+-- the union of two RegSets and then asking whether the union is the
+-- same as one of the inputs.  UniqSet isn't good here, because
+-- sizeUniqSet is O(n) whereas Set.size is O(1), so we use ordinary
+-- Sets.
+
+type RegSet r     = Set r
+
+emptyRegSet             :: RegSet r
+nullRegSet              :: RegSet r -> Bool
+elemRegSet              :: Ord r => r -> RegSet r -> Bool
+extendRegSet            :: Ord r => RegSet r -> r -> RegSet r
+deleteFromRegSet        :: Ord r => RegSet r -> r -> RegSet r
+mkRegSet                :: Ord r => [r] -> RegSet r
+minusRegSet, plusRegSet, timesRegSet :: Ord r => RegSet r -> RegSet r -> RegSet r
+sizeRegSet              :: RegSet r -> Int
+regSetToList            :: RegSet r -> [r]
+
+emptyRegSet      = Set.empty
+nullRegSet       = Set.null
+elemRegSet       = Set.member
+extendRegSet     = flip Set.insert
+deleteFromRegSet = flip Set.delete
+mkRegSet         = Set.fromList
+minusRegSet      = Set.difference
+plusRegSet       = Set.union
+timesRegSet      = Set.intersection
+sizeRegSet       = Set.size
+regSetToList     = Set.toList
diff --git a/compiler/GHC/CmmToAsm/Dwarf.hs b/compiler/GHC/CmmToAsm/Dwarf.hs
index fcff4be74e..b659b8a5a5 100644
--- a/compiler/GHC/CmmToAsm/Dwarf.hs
+++ b/compiler/GHC/CmmToAsm/Dwarf.hs
@@ -5,7 +5,7 @@ module GHC.CmmToAsm.Dwarf (
 import GHC.Prelude
 
 import GHC.Cmm.CLabel
-import GHC.Cmm.Expr        ( GlobalReg(..) )
+import GHC.Cmm.Reg.Global  ( GlobalReg(..) )
 import GHC.Settings.Config ( cProjectName, cProjectVersion )
 import GHC.Types.Tickish   ( CmmTickish, GenTickish(..) )
 import GHC.Cmm.DebugBlock
diff --git a/compiler/GHC/CmmToAsm/Dwarf/Types.hs b/compiler/GHC/CmmToAsm/Dwarf/Types.hs
index b607d1d45e..3502015566 100644
--- a/compiler/GHC/CmmToAsm/Dwarf/Types.hs
+++ b/compiler/GHC/CmmToAsm/Dwarf/Types.hs
@@ -31,7 +31,7 @@ import GHC.Prelude
 
 import GHC.Cmm.DebugBlock
 import GHC.Cmm.CLabel
-import GHC.Cmm.Expr         ( GlobalReg(..) )
+import GHC.Cmm.Reg.Global         ( GlobalReg(..) )
 import GHC.Utils.Encoding
 import GHC.Data.FastString
 import GHC.Utils.Outputable
diff --git a/compiler/GHC/CmmToAsm/Reg/Graph/Spill.hs b/compiler/GHC/CmmToAsm/Reg/Graph/Spill.hs
index 86c3590f99..81f62e16c2 100644
--- a/compiler/GHC/CmmToAsm/Reg/Graph/Spill.hs
+++ b/compiler/GHC/CmmToAsm/Reg/Graph/Spill.hs
@@ -13,7 +13,7 @@ import GHC.CmmToAsm.Reg.Liveness
 import GHC.CmmToAsm.Reg.Utils
 import GHC.CmmToAsm.Instr
 import GHC.Platform.Reg
-import GHC.Cmm hiding (RegSet)
+import GHC.Cmm
 import GHC.Cmm.BlockId
 import GHC.Cmm.Dataflow.Collections
 
diff --git a/compiler/GHC/CmmToAsm/Reg/Linear.hs b/compiler/GHC/CmmToAsm/Reg/Linear.hs
index 88fdcd6bce..ea6cb1de44 100644
--- a/compiler/GHC/CmmToAsm/Reg/Linear.hs
+++ b/compiler/GHC/CmmToAsm/Reg/Linear.hs
@@ -124,7 +124,7 @@ import GHC.Platform.Reg
 
 import GHC.Cmm.BlockId
 import GHC.Cmm.Dataflow.Collections
-import GHC.Cmm hiding (RegSet)
+import GHC.Cmm
 
 import GHC.Data.Graph.Directed
 import GHC.Types.Unique
diff --git a/compiler/GHC/CmmToAsm/Reg/Liveness.hs b/compiler/GHC/CmmToAsm/Reg/Liveness.hs
index bf53ecf421..e95c43572c 100644
--- a/compiler/GHC/CmmToAsm/Reg/Liveness.hs
+++ b/compiler/GHC/CmmToAsm/Reg/Liveness.hs
@@ -54,7 +54,7 @@ import GHC.CmmToAsm.Utils
 import GHC.Cmm.BlockId
 import GHC.Cmm.Dataflow.Collections
 import GHC.Cmm.Dataflow.Label
-import GHC.Cmm hiding (RegSet, emptyRegSet)
+import GHC.Cmm
 
 import GHC.Data.Graph.Directed
 import GHC.Utils.Monad
diff --git a/compiler/GHC/CmmToLlvm/Regs.hs b/compiler/GHC/CmmToLlvm/Regs.hs
index b18df77ed4..8811ebce7e 100644
--- a/compiler/GHC/CmmToLlvm/Regs.hs
+++ b/compiler/GHC/CmmToLlvm/Regs.hs
@@ -13,7 +13,7 @@ import GHC.Prelude
 
 import GHC.Llvm
 
-import GHC.Cmm.Expr
+import GHC.Cmm.Reg.Global
 import GHC.Platform
 import GHC.Data.FastString
 import GHC.Utils.Panic ( panic )
diff --git a/compiler/GHC/Platform/Regs.hs b/compiler/GHC/Platform/Regs.hs
index e0bdf5d6e5..66bed785e7 100644
--- a/compiler/GHC/Platform/Regs.hs
+++ b/compiler/GHC/Platform/Regs.hs
@@ -4,7 +4,7 @@ module GHC.Platform.Regs
 
 import GHC.Prelude
 
-import GHC.Cmm.Expr
+import GHC.Cmm.Reg.Global
 import GHC.Platform
 import GHC.Platform.Reg
 
diff --git a/compiler/GHC/StgToByteCode.hs b/compiler/GHC/StgToByteCode.hs
index f7bb270e16..4ee077f2a7 100644
--- a/compiler/GHC/StgToByteCode.hs
+++ b/compiler/GHC/StgToByteCode.hs
@@ -26,6 +26,8 @@ import GHC.Cmm.CallConv
 import GHC.Cmm.Expr
 import GHC.Cmm.Node
 import GHC.Cmm.Utils
+import GHC.Cmm.Reg.Global
+import GHC.Cmm.Reg.Set
 
 import GHC.Platform
 import GHC.Platform.Profile
diff --git a/compiler/GHC/Tc/Module.hs b/compiler/GHC/Tc/Module.hs
index 450e97819a..95d442e4ad 100644
--- a/compiler/GHC/Tc/Module.hs
+++ b/compiler/GHC/Tc/Module.hs
@@ -121,6 +121,7 @@ import GHC.Core.Unify( RoughMatchTc(..) )
 import GHC.Core.FamInstEnv
    ( FamInst, pprFamInst, famInstsRepTyCons
    , famInstEnvElts, extendFamInstEnvList, normaliseType )
+import GHC.Core.Lint     ( lintAxioms )
 
 import GHC.Parser.Header       ( mkPrelImports )
 
@@ -348,6 +349,14 @@ tcRnModuleTcRnM hsc_env mod_sum
         }
       }
 
+-- | Check the 'TcGblEnv' for consistency. Currently, only checks
+-- axioms, but should check other aspects, too.
+lintGblEnv :: Logger -> DynFlags -> TcGblEnv -> TcM ()
+lintGblEnv logger dflags tcg_env =
+  liftIO $ lintAxioms logger dflags (text "TcGblEnv axioms") axioms
+  where
+    axioms = typeEnvCoAxioms (tcg_type_env tcg_env)
+
 implicitPreludeWarn :: SDoc
 implicitPreludeWarn
   = text "Module `Prelude' implicitly imported"
diff --git a/compiler/GHC/Tc/Types.hs b/compiler/GHC/Tc/Types.hs
index 2d80039234..9ebb96008c 100644
--- a/compiler/GHC/Tc/Types.hs
+++ b/compiler/GHC/Tc/Types.hs
@@ -80,9 +80,6 @@ module GHC.Tc.Types(
         RoleAnnotEnv, emptyRoleAnnotEnv, mkRoleAnnotEnv,
         lookupRoleAnnot, getRoleAnnots,
 
-        -- Linting
-        lintGblEnv,
-
         -- Diagnostics
         TcRnMessage
   ) where
@@ -106,7 +103,6 @@ import GHC.Tc.Errors.Types
 import GHC.Core.Type
 import GHC.Core.TyCon  ( TyCon, tyConKind )
 import GHC.Core.PatSyn ( PatSyn )
-import GHC.Core.Lint   ( lintAxioms )
 import GHC.Core.UsageEnv
 import GHC.Core.InstEnv
 import GHC.Core.FamInstEnv
@@ -1755,18 +1751,10 @@ getRoleAnnots bndrs role_env
 
 {- *********************************************************************
 *                                                                      *
-                  Linting a TcGblEnv
+       DocLoc
 *                                                                      *
 ********************************************************************* -}
 
--- | Check the 'TcGblEnv' for consistency. Currently, only checks
--- axioms, but should check other aspects, too.
-lintGblEnv :: Logger -> DynFlags -> TcGblEnv -> TcM ()
-lintGblEnv logger dflags tcg_env =
-  liftIO $ lintAxioms logger dflags (text "TcGblEnv axioms") axioms
-  where
-    axioms = typeEnvCoAxioms (tcg_type_env tcg_env)
-
 -- | This is a mirror of Template Haskell's DocLoc, but the TH names are
 -- resolved to GHC names.
 data DocLoc = DeclDoc Name