From 14956cb89d8548e531c99821ad504b4f35b5509a Mon Sep 17 00:00:00 2001
From: Sylvain Henry <sylvain@haskus.fr>
Date: Wed, 2 Jun 2021 15:04:51 +0200
Subject: Put tracing functions into their own module

Now that Outputable is independent of DynFlags, we can put tracing
functions using SDocs into their own module that doesn't transitively
depend on any GHC.Driver.* module.

A few modules needed to be moved to avoid loops in DEBUG mode.
---
 compiler/GHC/Builtin/Utils.hs           |  2 +
 compiler/GHC/Cmm/Ppr/Expr.hs            |  3 +-
 compiler/GHC/CmmToAsm/BlockLayout.hs    | 18 +++----
 compiler/GHC/CmmToC.hs                  | 19 ++++---
 compiler/GHC/Core.hs                    |  3 +-
 compiler/GHC/Core/Coercion/Opt.hs       | 11 ++--
 compiler/GHC/Core/Lint.hs               | 62 +++++++++++++----------
 compiler/GHC/Core/Opt/Arity.hs          | 28 +++++-----
 compiler/GHC/Core/Opt/ConstantFold.hs   | 40 ++++++++-------
 compiler/GHC/Core/Opt/CprAnal.hs        | 23 +++++----
 compiler/GHC/Core/Opt/OccurAnal.hs      | 30 ++++++-----
 compiler/GHC/Core/Opt/Pipeline.hs       |  2 +-
 compiler/GHC/Core/Opt/SetLevels.hs      | 25 +++++----
 compiler/GHC/Core/Opt/Simplify.hs       | 49 ++++++++++--------
 compiler/GHC/Core/Opt/Simplify/Utils.hs | 27 +++++-----
 compiler/GHC/Core/Opt/SpecConstr.hs     | 38 ++++++++------
 compiler/GHC/Core/Opt/Specialise.hs     |  2 +
 compiler/GHC/Core/Opt/WorkWrap.hs       | 17 ++++---
 compiler/GHC/Core/Opt/WorkWrap/Utils.hs | 34 +++++++------
 compiler/GHC/Core/Rules.hs              | 27 ++++++----
 compiler/GHC/Core/Subst.hs              |  8 +--
 compiler/GHC/Core/Unfold.hs             |  3 +-
 compiler/GHC/Core/Utils.hs              | 42 ++++++++-------
 compiler/GHC/CoreToIface.hs             | 39 +++++++-------
 compiler/GHC/CoreToStg.hs               | 32 +++++++-----
 compiler/GHC/CoreToStg/Prep.hs          |  6 +--
 compiler/GHC/Data/Bool.hs               | 18 +++++++
 compiler/GHC/Data/List/SetOps.hs        | 37 +++++++++++++-
 compiler/GHC/Driver/CodeOutput.hs       |  4 +-
 compiler/GHC/Driver/Env.hs              |  6 +--
 compiler/GHC/Driver/Ppr.hs              | 90 +--------------------------------
 compiler/GHC/Driver/Ppr.hs-boot         |  9 ----
 compiler/GHC/Driver/Session.hs          |  1 +
 compiler/GHC/HsToCore/Binds.hs          | 40 ++++++++-------
 compiler/GHC/Iface/Load.hs              |  2 +-
 compiler/GHC/Iface/Make.hs              |  2 +-
 compiler/GHC/Iface/Recomp.hs            |  1 +
 compiler/GHC/Iface/Tidy.hs              |  1 +
 compiler/GHC/Parser/Lexer.x             |  1 +
 compiler/GHC/Rename/Names.hs            |  1 +
 compiler/GHC/Runtime/Eval.hs            |  1 +
 compiler/GHC/Stg/Pipeline.hs            |  3 +-
 compiler/GHC/Stg/Subst.hs               |  3 +-
 compiler/GHC/StgToCmm/Bind.hs           | 26 ++++++----
 compiler/GHC/StgToCmm/Ticky.hs          |  9 ++--
 compiler/GHC/Tc/Gen/Sig.hs              | 23 ++++++---
 compiler/GHC/Tc/Types/Origin.hs         |  2 +-
 compiler/GHC/Tc/Utils/TcMType.hs        | 40 ++++++++-------
 compiler/GHC/Types/Id.hs                |  3 +-
 compiler/GHC/Types/TyThing/Ppr.hs       |  3 +-
 compiler/GHC/Utils/Error.hs             |  1 -
 compiler/GHC/Utils/Logger.hs            |  4 +-
 compiler/GHC/Utils/Misc.hs              | 50 ------------------
 compiler/GHC/Utils/Outputable.hs        |  8 +++
 compiler/GHC/Utils/Panic.hs             |  2 -
 compiler/GHC/Utils/Ppr/Colour.hs        |  7 ++-
 compiler/GHC/Utils/Trace.hs             | 77 ++++++++++++++++++++++++++++
 compiler/ghc.cabal.in                   |  2 +
 58 files changed, 575 insertions(+), 492 deletions(-)
 create mode 100644 compiler/GHC/Data/Bool.hs
 delete mode 100644 compiler/GHC/Driver/Ppr.hs-boot
 create mode 100644 compiler/GHC/Utils/Trace.hs

(limited to 'compiler')

diff --git a/compiler/GHC/Builtin/Utils.hs b/compiler/GHC/Builtin/Utils.hs
index ab46812040..16d5096605 100644
--- a/compiler/GHC/Builtin/Utils.hs
+++ b/compiler/GHC/Builtin/Utils.hs
@@ -78,6 +78,8 @@ import GHC.Utils.Constants (debugIsOn)
 import GHC.Hs.Doc
 import GHC.Unit.Module.ModIface (IfaceExport)
 
+import GHC.Data.List.SetOps
+
 import Control.Applicative ((<|>))
 import Data.List        ( intercalate , find )
 import Data.Array
diff --git a/compiler/GHC/Cmm/Ppr/Expr.hs b/compiler/GHC/Cmm/Ppr/Expr.hs
index c656c98522..7828daf803 100644
--- a/compiler/GHC/Cmm/Ppr/Expr.hs
+++ b/compiler/GHC/Cmm/Ppr/Expr.hs
@@ -44,12 +44,11 @@ where
 
 import GHC.Prelude
 
-import GHC.Driver.Ppr
-
 import GHC.Platform
 import GHC.Cmm.Expr
 
 import GHC.Utils.Outputable
+import GHC.Utils.Trace
 
 import Data.Maybe
 import Numeric ( fromRat )
diff --git a/compiler/GHC/CmmToAsm/BlockLayout.hs b/compiler/GHC/CmmToAsm/BlockLayout.hs
index 35dce5246d..6e2e7e2189 100644
--- a/compiler/GHC/CmmToAsm/BlockLayout.hs
+++ b/compiler/GHC/CmmToAsm/BlockLayout.hs
@@ -15,7 +15,7 @@ where
 
 import GHC.Prelude
 
-import GHC.Driver.Ppr     (pprTrace)
+import GHC.Platform
 
 import GHC.CmmToAsm.Instr
 import GHC.CmmToAsm.Monad
@@ -23,30 +23,26 @@ import GHC.CmmToAsm.CFG
 import GHC.CmmToAsm.Types
 import GHC.CmmToAsm.Config
 
-import GHC.Cmm.BlockId
 import GHC.Cmm
+import GHC.Cmm.BlockId
 import GHC.Cmm.Dataflow.Collections
 import GHC.Cmm.Dataflow.Label
 
-import GHC.Platform
 import GHC.Types.Unique.FM
 
 import GHC.Data.Graph.Directed
+import GHC.Data.Maybe
+import GHC.Data.List.SetOps (removeDups)
+import GHC.Data.OrdList
+
+import GHC.Utils.Trace
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
 import GHC.Utils.Misc
-import GHC.Data.Maybe
-
--- DEBUGGING ONLY
---import GHC.Cmm.DebugBlock
---import Debug.Trace
-import GHC.Data.List.SetOps (removeDups)
 
-import GHC.Data.OrdList
 import Data.List (sortOn, sortBy)
 import Data.Foldable (toList)
-
 import qualified Data.Set as Set
 import Data.STRef
 import Control.Monad.ST.Strict
diff --git a/compiler/GHC/CmmToC.hs b/compiler/GHC/CmmToC.hs
index ae6f4b91b6..4e828e29f4 100644
--- a/compiler/GHC/CmmToC.hs
+++ b/compiler/GHC/CmmToC.hs
@@ -25,12 +25,14 @@ module GHC.CmmToC
    )
 where
 
--- Cmm stuff
 import GHC.Prelude
 
+import GHC.Platform
+
+import GHC.CmmToAsm.CPrim
+
 import GHC.Cmm.BlockId
 import GHC.Cmm.CLabel
-import GHC.Types.ForeignCall
 import GHC.Cmm hiding (pprBBlock)
 import GHC.Cmm.Ppr () -- For Outputable instances
 import GHC.Cmm.Dataflow.Block
@@ -39,19 +41,16 @@ import GHC.Cmm.Dataflow.Graph
 import GHC.Cmm.Utils
 import GHC.Cmm.Switch
 
--- Utils
-import GHC.CmmToAsm.CPrim
-import GHC.Driver.Session
-import GHC.Driver.Ppr
-import GHC.Utils.Outputable
-import GHC.Utils.Panic
-import GHC.Platform
+import GHC.Types.ForeignCall
 import GHC.Types.Unique.Set
 import GHC.Types.Unique.FM
 import GHC.Types.Unique
+
+import GHC.Utils.Outputable
+import GHC.Utils.Panic
 import GHC.Utils.Misc
+import GHC.Utils.Trace
 
--- The rest
 import Data.ByteString (ByteString)
 import qualified Data.ByteString as BS
 import Control.Monad.ST
diff --git a/compiler/GHC/Core.hs b/compiler/GHC/Core.hs
index a17604300f..ecd9a6ee00 100644
--- a/compiler/GHC/Core.hs
+++ b/compiler/GHC/Core.hs
@@ -114,8 +114,7 @@ import GHC.Utils.Misc
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
-
-import GHC.Driver.Ppr
+import GHC.Utils.Trace
 
 import Data.Data hiding (TyCon)
 import Data.Int
diff --git a/compiler/GHC/Core/Coercion/Opt.hs b/compiler/GHC/Core/Coercion/Opt.hs
index 85b6e93ec1..4be4441682 100644
--- a/compiler/GHC/Core/Coercion/Opt.hs
+++ b/compiler/GHC/Core/Coercion/Opt.hs
@@ -11,27 +11,30 @@ where
 
 import GHC.Prelude
 
-import GHC.Driver.Ppr
+import GHC.Tc.Utils.TcType   ( exactTyCoVarsOfType )
 
 import GHC.Core.TyCo.Rep
 import GHC.Core.TyCo.Subst
 import GHC.Core.Coercion
 import GHC.Core.Type as Type hiding( substTyVarBndr, substTy )
-import GHC.Tc.Utils.TcType   ( exactTyCoVarsOfType )
 import GHC.Core.TyCon
 import GHC.Core.Coercion.Axiom
+import GHC.Core.Unify
+
 import GHC.Types.Var.Set
 import GHC.Types.Var.Env
+
 import GHC.Data.Pair
 import GHC.Data.List.SetOps ( getNth )
-import GHC.Core.Unify
-import Control.Monad   ( zipWithM )
 
 import GHC.Utils.Outputable
 import GHC.Utils.Constants (debugIsOn)
 import GHC.Utils.Misc
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
+import GHC.Utils.Trace
+
+import Control.Monad   ( zipWithM )
 
 {-
 %************************************************************************
diff --git a/compiler/GHC/Core/Lint.hs b/compiler/GHC/Core/Lint.hs
index 45115bfb45..43935d1efe 100644
--- a/compiler/GHC/Core/Lint.hs
+++ b/compiler/GHC/Core/Lint.hs
@@ -29,33 +29,21 @@ import GHC.Driver.Session
 import GHC.Driver.Ppr
 import GHC.Driver.Env
 
+import GHC.Tc.Utils.TcType ( isFloatingTy, isTyFamFree )
+import GHC.Unit.Module.ModGuts
+import GHC.Runtime.Context
+
 import GHC.Core
 import GHC.Core.FVs
 import GHC.Core.Utils
 import GHC.Core.Stats ( coreBindsStats )
 import GHC.Core.Opt.Monad
-import GHC.Data.Bag
-import GHC.Types.Literal
 import GHC.Core.DataCon
-import GHC.Builtin.Types.Prim
-import GHC.Builtin.Types ( multiplicityTy )
-import GHC.Tc.Utils.TcType ( isFloatingTy, isTyFamFree )
-import GHC.Types.Var as Var
-import GHC.Types.Var.Env
-import GHC.Types.Var.Set
-import GHC.Types.Unique.Set( nonDetEltsUniqSet )
-import GHC.Types.Name
-import GHC.Types.Name.Env
-import GHC.Types.Id
-import GHC.Types.Id.Info
 import GHC.Core.Ppr
 import GHC.Core.Coercion
-import GHC.Types.SrcLoc
-import GHC.Types.Tickish
 import GHC.Core.Type as Type
 import GHC.Core.Multiplicity
 import GHC.Core.UsageEnv
-import GHC.Types.RepType
 import GHC.Core.TyCo.Rep   -- checks validity of types/coercions
 import GHC.Core.TyCo.Subst
 import GHC.Core.TyCo.FVs
@@ -63,26 +51,44 @@ import GHC.Core.TyCo.Ppr ( pprTyVar, pprTyVars )
 import GHC.Core.TyCon as TyCon
 import GHC.Core.Coercion.Axiom
 import GHC.Core.Unify
+import GHC.Core.InstEnv      ( instanceDFunId )
+import GHC.Core.Coercion.Opt ( checkAxInstCo )
+import GHC.Core.Opt.Arity    ( typeArity )
+
+import GHC.Types.Literal
+import GHC.Types.Var as Var
+import GHC.Types.Var.Env
+import GHC.Types.Var.Set
+import GHC.Types.Unique.Set( nonDetEltsUniqSet )
+import GHC.Types.Name
+import GHC.Types.Name.Env
+import GHC.Types.Id
+import GHC.Types.Id.Info
+import GHC.Types.SrcLoc
+import GHC.Types.Tickish
+import GHC.Types.RepType
 import GHC.Types.Basic
-import GHC.Utils.Error
-import qualified GHC.Utils.Error as Err
-import GHC.Utils.Logger
-import GHC.Data.List.SetOps
+import GHC.Types.Demand      ( splitDmdSig, isDeadEndDiv )
+import GHC.Types.TypeEnv
+
 import GHC.Builtin.Names
+import GHC.Builtin.Types.Prim
+import GHC.Builtin.Types ( multiplicityTy )
+
+import GHC.Data.Bag
+import GHC.Data.List.SetOps
+
+import GHC.Utils.Monad
 import GHC.Utils.Outputable as Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Constants (debugIsOn)
 import GHC.Utils.Misc
-import GHC.Core.InstEnv      ( instanceDFunId )
-import GHC.Core.Coercion.Opt ( checkAxInstCo )
-import GHC.Core.Opt.Arity    ( typeArity )
-import GHC.Types.Demand      ( splitDmdSig, isDeadEndDiv )
-import GHC.Types.TypeEnv
-import GHC.Unit.Module.ModGuts
-import GHC.Runtime.Context
+import GHC.Utils.Trace
+import GHC.Utils.Error
+import qualified GHC.Utils.Error as Err
+import GHC.Utils.Logger
 
 import Control.Monad
-import GHC.Utils.Monad
 import Data.Foldable      ( toList )
 import Data.List.NonEmpty ( NonEmpty(..), groupWith )
 import Data.List          ( partition )
diff --git a/compiler/GHC/Core/Opt/Arity.hs b/compiler/GHC/Core/Opt/Arity.hs
index 021af2d503..8bdf063eb9 100644
--- a/compiler/GHC/Core/Opt/Arity.hs
+++ b/compiler/GHC/Core/Opt/Arity.hs
@@ -31,15 +31,16 @@ where
 
 import GHC.Prelude
 
-import GHC.Driver.Ppr
+import GHC.Driver.Session ( DynFlags, GeneralFlag(..), gopt )
 
 import GHC.Core
 import GHC.Core.FVs
 import GHC.Core.Utils
-import GHC.Types.Demand
-import GHC.Types.Var
-import GHC.Types.Var.Env
-import GHC.Types.Id
+import GHC.Core.DataCon
+import GHC.Core.TyCon     ( tyConArity )
+import GHC.Core.TyCon.RecWalk     ( initRecTc, checkRecTc )
+import GHC.Core.Predicate ( isDictTy )
+import GHC.Core.Multiplicity
 
 -- We have two sorts of substitution:
 --   GHC.Core.Subst.Subst, and GHC.Core.TyCo.TCvSubst
@@ -48,22 +49,23 @@ import GHC.Core.Subst    as Core
 import GHC.Core.Type     as Type
 import GHC.Core.Coercion as Type
 
-import GHC.Core.DataCon
-import GHC.Core.TyCon     ( tyConArity )
-import GHC.Core.TyCon.RecWalk     ( initRecTc, checkRecTc )
-import GHC.Core.Predicate ( isDictTy )
-import GHC.Core.Multiplicity
+import GHC.Types.Demand
+import GHC.Types.Var
+import GHC.Types.Var.Env
+import GHC.Types.Id
 import GHC.Types.Var.Set
 import GHC.Types.Basic
 import GHC.Types.Tickish
+
 import GHC.Builtin.Uniques
-import GHC.Driver.Session ( DynFlags, GeneralFlag(..), gopt )
+import GHC.Data.FastString
+import GHC.Data.Pair
+
 import GHC.Utils.Constants (debugIsOn)
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
-import GHC.Data.FastString
-import GHC.Data.Pair
+import GHC.Utils.Trace
 import GHC.Utils.Misc
 
 {-
diff --git a/compiler/GHC/Core/Opt/ConstantFold.hs b/compiler/GHC/Core/Opt/ConstantFold.hs
index 14d4f840b6..9917db7584 100644
--- a/compiler/GHC/Core/Opt/ConstantFold.hs
+++ b/compiler/GHC/Core/Opt/ConstantFold.hs
@@ -32,45 +32,47 @@ where
 
 import GHC.Prelude
 
-import GHC.Driver.Ppr
+import GHC.Platform
 
 import {-# SOURCE #-} GHC.Types.Id.Make ( mkPrimOpId, voidPrimId )
+import GHC.Types.Id
+import GHC.Types.Literal
+import GHC.Types.Var.Set
+import GHC.Types.Var.Env
+import GHC.Types.Name.Occurrence ( occNameFS )
+import GHC.Types.Tickish
+import GHC.Types.Name ( Name, nameOccName )
+import GHC.Types.Basic
 
 import GHC.Core
 import GHC.Core.Make
-import GHC.Types.Id
-import GHC.Types.Literal
 import GHC.Core.SimpleOpt (  exprIsConApp_maybe, exprIsLiteral_maybe )
-import GHC.Builtin.PrimOps ( PrimOp(..), tagToEnumKey )
-import GHC.Builtin.Types
-import GHC.Builtin.Types.Prim
-import GHC.Core.TyCon
-   ( tyConDataCons_maybe, isAlgTyCon, isEnumerationTyCon
-   , isNewTyCon, tyConDataCons
-   , tyConFamilySize )
 import GHC.Core.DataCon ( dataConTagZ, dataConTyCon, dataConWrapId, dataConWorkId )
 import GHC.Core.Utils  ( eqExpr, cheapEqExpr, exprIsHNF, exprType
                        , stripTicksTop, stripTicksTopT, mkTicks )
 import GHC.Core.Multiplicity
 import GHC.Core.FVs
 import GHC.Core.Type
-import GHC.Types.Var.Set
-import GHC.Types.Var.Env
-import GHC.Types.Name.Occurrence ( occNameFS )
-import GHC.Types.Tickish
+import GHC.Core.TyCon
+   ( tyConDataCons_maybe, isAlgTyCon, isEnumerationTyCon
+   , isNewTyCon, tyConDataCons
+   , tyConFamilySize )
+
+import GHC.Builtin.PrimOps ( PrimOp(..), tagToEnumKey )
+import GHC.Builtin.Types
+import GHC.Builtin.Types.Prim
 import GHC.Builtin.Names
+
+import GHC.Data.FastString
 import GHC.Data.Maybe      ( orElse )
-import GHC.Types.Name ( Name, nameOccName )
+
 import GHC.Utils.Outputable
-import GHC.Data.FastString
-import GHC.Types.Basic
-import GHC.Platform
 import GHC.Utils.Misc
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
+import GHC.Utils.Trace
 
 import Control.Applicative ( Alternative(..) )
-
 import Control.Monad
 import Data.Functor (($>))
 import qualified Data.ByteString as BS
diff --git a/compiler/GHC/Core/Opt/CprAnal.hs b/compiler/GHC/Core/Opt/CprAnal.hs
index 91f6abef0d..f3ae2c0b43 100644
--- a/compiler/GHC/Core/Opt/CprAnal.hs
+++ b/compiler/GHC/Core/Opt/CprAnal.hs
@@ -11,16 +11,16 @@ module GHC.Core.Opt.CprAnal ( cprAnalProgram ) where
 import GHC.Prelude
 
 import GHC.Driver.Session
-import GHC.Types.Demand
-import GHC.Types.Cpr
-import GHC.Core
-import GHC.Core.Seq
-import GHC.Utils.Outputable
+
 import GHC.Builtin.Names ( runRWKey )
+
 import GHC.Types.Var.Env
 import GHC.Types.Basic
 import GHC.Types.Id
 import GHC.Types.Id.Info
+import GHC.Types.Demand
+import GHC.Types.Cpr
+
 import GHC.Core.DataCon
 import GHC.Core.FamInstEnv
 import GHC.Core.Multiplicity
@@ -28,18 +28,21 @@ import GHC.Core.Opt.WorkWrap.Utils
 import GHC.Core.TyCon
 import GHC.Core.Type
 import GHC.Core.Utils   ( exprIsHNF, dumpIdInfoOfProgram, normSplitTyConApp_maybe )
+import GHC.Core
+import GHC.Core.Seq
+
+import GHC.Data.Graph.UnVar -- for UnVarSet
+import GHC.Data.Maybe   ( isJust )
+
+import GHC.Utils.Outputable
 import GHC.Utils.Misc
 import GHC.Utils.Panic.Plain
 import GHC.Utils.Logger  ( Logger, putDumpFileMaybe, DumpFormat (..) )
-import GHC.Data.Graph.UnVar -- for UnVarSet
-import GHC.Data.Maybe   ( isJust )
+--import GHC.Utils.Trace
 
 import Control.Monad ( guard )
 import Data.List ( mapAccumL )
 
-import GHC.Driver.Ppr
-_ = pprTrace -- Tired of commenting out the import all the time
-
 {- Note [Constructed Product Result]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 The goal of Constructed Product Result analysis is to identify functions that
diff --git a/compiler/GHC/Core/Opt/OccurAnal.hs b/compiler/GHC/Core/Opt/OccurAnal.hs
index 93813a1735..cc67802309 100644
--- a/compiler/GHC/Core/Opt/OccurAnal.hs
+++ b/compiler/GHC/Core/Opt/OccurAnal.hs
@@ -20,38 +20,40 @@ module GHC.Core.Opt.OccurAnal ( occurAnalysePgm, occurAnalyseExpr ) where
 
 import GHC.Prelude
 
-import GHC.Driver.Ppr
-
 import GHC.Core
 import GHC.Core.FVs
 import GHC.Core.Utils   ( exprIsTrivial, isDefaultAlt, isExpandableApp,
                           stripTicksTopE, mkTicks )
 import GHC.Core.Opt.Arity   ( joinRhsArity )
-import GHC.Types.Id
-import GHC.Types.Id.Info
-import GHC.Types.Basic
-import GHC.Types.Tickish
-import GHC.Unit.Module( Module )
 import GHC.Core.Coercion
 import GHC.Core.Type
 import GHC.Core.TyCo.FVs( tyCoVarsOfMCo )
 
-import GHC.Types.Var.Set
-import GHC.Types.Var.Env
-import GHC.Types.Var
-import GHC.Types.Demand ( argOneShots, argsOneShots )
+import GHC.Data.Maybe( isJust )
 import GHC.Data.Graph.Directed ( SCC(..), Node(..)
                                , stronglyConnCompFromEdgedVerticesUniq
                                , stronglyConnCompFromEdgedVerticesUniqR )
-import GHC.Builtin.Names( runRWKey )
 import GHC.Types.Unique
 import GHC.Types.Unique.FM
 import GHC.Types.Unique.Set
-import GHC.Utils.Misc
-import GHC.Data.Maybe( isJust )
+import GHC.Types.Id
+import GHC.Types.Id.Info
+import GHC.Types.Basic
+import GHC.Types.Tickish
+import GHC.Types.Var.Set
+import GHC.Types.Var.Env
+import GHC.Types.Var
+import GHC.Types.Demand ( argOneShots, argsOneShots )
+
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
+import GHC.Utils.Misc
+import GHC.Utils.Trace
+
+import GHC.Builtin.Names( runRWKey )
+import GHC.Unit.Module( Module )
+
 import Data.List (mapAccumL, mapAccumR)
 
 {-
diff --git a/compiler/GHC/Core/Opt/Pipeline.hs b/compiler/GHC/Core/Opt/Pipeline.hs
index 23908403c7..666725f320 100644
--- a/compiler/GHC/Core/Opt/Pipeline.hs
+++ b/compiler/GHC/Core/Opt/Pipeline.hs
@@ -11,7 +11,6 @@ module GHC.Core.Opt.Pipeline ( core2core, simplifyExpr ) where
 import GHC.Prelude
 
 import GHC.Driver.Session
-import GHC.Driver.Ppr
 import GHC.Driver.Plugins ( withPlugins, installCoreToDos )
 import GHC.Driver.Env
 import GHC.Platform.Ways  ( hasWay, Way(WayProf) )
@@ -52,6 +51,7 @@ import GHC.Utils.Logger as Logger
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Constants (debugIsOn)
+import GHC.Utils.Trace
 
 import GHC.Unit.External
 import GHC.Unit.Module.Env
diff --git a/compiler/GHC/Core/Opt/SetLevels.hs b/compiler/GHC/Core/Opt/SetLevels.hs
index b1298c6b50..2d69e8eb04 100644
--- a/compiler/GHC/Core/Opt/SetLevels.hs
+++ b/compiler/GHC/Core/Opt/SetLevels.hs
@@ -77,8 +77,6 @@ module GHC.Core.Opt.SetLevels (
 
 import GHC.Prelude
 
-import GHC.Driver.Ppr
-
 import GHC.Core
 import GHC.Core.Opt.Monad ( FloatOutSwitches(..) )
 import GHC.Core.Utils   ( exprType, exprIsHNF
@@ -92,6 +90,10 @@ import GHC.Core.Opt.Arity   ( exprBotStrictness_maybe )
 import GHC.Core.FVs     -- all of it
 import GHC.Core.Subst
 import GHC.Core.Make    ( sortQuantVars )
+import GHC.Core.Type    ( Type, splitTyConApp_maybe, tyCoVarsOfType
+                        , mightBeUnliftedType, closeOverKindsDSet )
+import GHC.Core.Multiplicity     ( pattern Many )
+import GHC.Core.DataCon ( dataConOrigResTy )
 
 import GHC.Types.Id
 import GHC.Types.Id.Info
@@ -107,23 +109,24 @@ import GHC.Types.Name         ( getOccName, mkSystemVarName )
 import GHC.Types.Name.Occurrence ( occNameString )
 import GHC.Types.Unique       ( hasKey )
 import GHC.Types.Tickish      ( tickishIsCode )
-import GHC.Core.Type    ( Type, splitTyConApp_maybe, tyCoVarsOfType
-                        , mightBeUnliftedType, closeOverKindsDSet )
-import GHC.Core.Multiplicity     ( pattern Many )
+import GHC.Types.Unique.Supply
+import GHC.Types.Unique.DFM
 import GHC.Types.Basic  ( Arity, RecFlag(..), isRec )
-import GHC.Core.DataCon ( dataConOrigResTy )
+
 import GHC.Builtin.Types
 import GHC.Builtin.Names      ( runRWKey )
-import GHC.Types.Unique.Supply
+
+import GHC.Data.FastString
+
+import GHC.Utils.FV
+import GHC.Utils.Monad  ( mapAccumLM )
 import GHC.Utils.Misc
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
-import GHC.Data.FastString
-import GHC.Types.Unique.DFM
-import GHC.Utils.FV
+import GHC.Utils.Trace
+
 import Data.Maybe
-import GHC.Utils.Monad  ( mapAccumLM )
 
 {-
 ************************************************************************
diff --git a/compiler/GHC/Core/Opt/Simplify.hs b/compiler/GHC/Core/Opt/Simplify.hs
index caa18050e2..cb5264f4ba 100644
--- a/compiler/GHC/Core/Opt/Simplify.hs
+++ b/compiler/GHC/Core/Opt/Simplify.hs
@@ -13,21 +13,17 @@ module GHC.Core.Opt.Simplify ( simplTopBinds, simplExpr, simplRules ) where
 import GHC.Prelude
 
 import GHC.Platform
+
 import GHC.Driver.Session
-import GHC.Driver.Ppr
+
+import GHC.Core
 import GHC.Core.Opt.Simplify.Monad
 import GHC.Core.Type hiding ( substTy, substTyVar, extendTvSubst, extendCvSubst )
 import GHC.Core.Opt.Simplify.Env
 import GHC.Core.Opt.Simplify.Utils
 import GHC.Core.Opt.OccurAnal ( occurAnalyseExpr )
-import GHC.Types.Literal   ( litIsLifted ) --, mkLitInt ) -- temporalily commented out. See #8326
-import GHC.Types.SourceText
-import GHC.Types.Id
-import GHC.Types.Id.Make   ( seqId )
 import GHC.Core.Make       ( FloatBind, mkImpossibleExpr, castBottomExpr )
 import qualified GHC.Core.Make
-import GHC.Types.Id.Info
-import GHC.Types.Name           ( mkSystemVarName, isExternalName, getOccFS )
 import GHC.Core.Coercion hiding ( substCo, substCoVar )
 import GHC.Core.Coercion.Opt    ( optCoercion )
 import GHC.Core.FamInstEnv      ( FamInstEnv, topNormaliseType_maybe )
@@ -36,14 +32,7 @@ import GHC.Core.DataCon
    , dataConRepArgTys, isUnboxedTupleDataCon
    , StrictnessMark (..) )
 import GHC.Core.Opt.Monad ( Tick(..), SimplMode(..) )
-import GHC.Core
-import GHC.Builtin.Types.Prim( realWorldStatePrimTy )
-import GHC.Builtin.Names( runRWKey )
-import GHC.Types.Demand ( DmdSig(..), Demand, dmdTypeDepth, isStrUsedDmd
-                        , mkClosedDmdSig, topDmd, seqDmd, isDeadEndDiv )
-import GHC.Types.Cpr    ( mkCprSig, botCpr )
 import GHC.Core.Ppr     ( pprCoreExpr )
-import GHC.Types.Unique ( hasKey )
 import GHC.Core.Unfold
 import GHC.Core.Unfold.Make
 import GHC.Core.Utils
@@ -53,21 +42,39 @@ import GHC.Core.Opt.Arity ( ArityType(..)
 import GHC.Core.SimpleOpt ( exprIsConApp_maybe, joinPointBinding_maybe, joinPointBindings_maybe )
 import GHC.Core.FVs     ( mkRuleInfo )
 import GHC.Core.Rules   ( lookupRule, getRules, initRuleOpts )
+import GHC.Core.Multiplicity
+
+import GHC.Types.Literal   ( litIsLifted ) --, mkLitInt ) -- temporalily commented out. See #8326
+import GHC.Types.SourceText
+import GHC.Types.Id
+import GHC.Types.Id.Make   ( seqId )
+import GHC.Types.Id.Info
+import GHC.Types.Name   ( mkSystemVarName, isExternalName, getOccFS )
+import GHC.Types.Demand ( DmdSig(..), Demand, dmdTypeDepth, isStrUsedDmd
+                        , mkClosedDmdSig, topDmd, seqDmd, isDeadEndDiv )
+import GHC.Types.Cpr    ( mkCprSig, botCpr )
+import GHC.Types.Unique ( hasKey )
 import GHC.Types.Basic
-import GHC.Utils.Monad  ( mapAccumLM, liftIO )
-import GHC.Utils.Logger
 import GHC.Types.Tickish
 import GHC.Types.Var    ( isTyCoVar )
+
+import GHC.Builtin.PrimOps ( PrimOp (SeqOp) )
+import GHC.Builtin.Types.Prim( realWorldStatePrimTy )
+import GHC.Builtin.Names( runRWKey )
+
 import GHC.Data.Maybe   ( orElse )
-import Control.Monad
+import GHC.Data.FastString
+import GHC.Unit.Module ( moduleName, pprModuleName )
+
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
 import GHC.Utils.Constants (debugIsOn)
-import GHC.Data.FastString
-import GHC.Unit.Module ( moduleName, pprModuleName )
-import GHC.Core.Multiplicity
-import GHC.Builtin.PrimOps ( PrimOp (SeqOp) )
+import GHC.Utils.Trace
+import GHC.Utils.Monad  ( mapAccumLM, liftIO )
+import GHC.Utils.Logger
+
+import Control.Monad
 
 
 {-
diff --git a/compiler/GHC/Core/Opt/Simplify/Utils.hs b/compiler/GHC/Core/Opt/Simplify/Utils.hs
index 09b39cbfb2..15cccfd55b 100644
--- a/compiler/GHC/Core/Opt/Simplify/Utils.hs
+++ b/compiler/GHC/Core/Opt/Simplify/Utils.hs
@@ -39,11 +39,11 @@ module GHC.Core.Opt.Simplify.Utils (
 
 import GHC.Prelude
 
-import GHC.Core.Opt.Simplify.Env
-import GHC.Core.Opt.Monad        ( SimplMode(..), Tick(..) )
 import GHC.Driver.Session
-import GHC.Driver.Ppr
+
 import GHC.Core
+import GHC.Core.Opt.Simplify.Env
+import GHC.Core.Opt.Monad        ( SimplMode(..), Tick(..) )
 import qualified GHC.Core.Subst
 import GHC.Core.Ppr
 import GHC.Core.TyCo.Ppr ( pprParendType )
@@ -52,28 +52,31 @@ import GHC.Core.Utils
 import GHC.Core.Opt.Arity
 import GHC.Core.Unfold
 import GHC.Core.Unfold.Make
+import GHC.Core.Opt.Simplify.Monad
+import GHC.Core.Type     hiding( substTy )
+import GHC.Core.Coercion hiding( substCo )
+import GHC.Core.DataCon ( dataConWorkId, isNullaryRepDataCon )
+import GHC.Core.Multiplicity
+import GHC.Core.Opt.ConstantFold
+
 import GHC.Types.Name
 import GHC.Types.Id
 import GHC.Types.Id.Info
 import GHC.Types.Tickish
-import GHC.Types.Var
 import GHC.Types.Demand
 import GHC.Types.Var.Set
 import GHC.Types.Basic
-import GHC.Core.Opt.Simplify.Monad
-import GHC.Core.Type     hiding( substTy )
-import GHC.Core.Coercion hiding( substCo )
-import GHC.Core.DataCon ( dataConWorkId, isNullaryRepDataCon )
-import GHC.Core.Multiplicity
-import GHC.Utils.Misc
+
 import GHC.Data.OrdList ( isNilOL )
+import GHC.Data.FastString ( fsLit )
+
+import GHC.Utils.Misc
 import GHC.Utils.Monad
 import GHC.Utils.Outputable
 import GHC.Utils.Logger
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
-import GHC.Core.Opt.ConstantFold
-import GHC.Data.FastString ( fsLit )
+import GHC.Utils.Trace
 
 import Control.Monad    ( when )
 import Data.List        ( sortBy )
diff --git a/compiler/GHC/Core/Opt/SpecConstr.hs b/compiler/GHC/Core/Opt/SpecConstr.hs
index 3c0e6b46cf..718c840c96 100644
--- a/compiler/GHC/Core/Opt/SpecConstr.hs
+++ b/compiler/GHC/Core/Opt/SpecConstr.hs
@@ -21,14 +21,15 @@ module GHC.Core.Opt.SpecConstr(
 
 import GHC.Prelude
 
+import GHC.Driver.Session ( DynFlags(..), GeneralFlag( Opt_SpecConstrKeen )
+                          , gopt, hasPprDebug )
+
 import GHC.Core
 import GHC.Core.Subst
 import GHC.Core.Utils
 import GHC.Core.Unfold
 import GHC.Core.FVs     ( exprsFreeVarsList )
 import GHC.Core.Opt.Monad
-import GHC.Types.Literal ( litIsLifted )
-import GHC.Unit.Module.ModGuts
 import GHC.Core.Opt.WorkWrap.Utils ( isWorkerSmallEnough, mkWorkerArgs )
 import GHC.Core.DataCon
 import GHC.Core.Coercion hiding( substCo )
@@ -36,35 +37,42 @@ import GHC.Core.Rules
 import GHC.Core.Type     hiding ( substTy )
 import GHC.Core.TyCon   (TyCon, tyConUnique, tyConName )
 import GHC.Core.Multiplicity
-import GHC.Types.Id
 import GHC.Core.Ppr     ( pprParendExpr )
 import GHC.Core.Make    ( mkImpossibleExpr )
+
+import GHC.Unit.Module
+import GHC.Unit.Module.ModGuts
+
+import GHC.Types.Literal ( litIsLifted )
+import GHC.Types.Id
 import GHC.Types.Var.Env
 import GHC.Types.Var.Set
 import GHC.Types.Name
 import GHC.Types.Tickish
 import GHC.Types.Basic
-import GHC.Driver.Session ( DynFlags(..), GeneralFlag( Opt_SpecConstrKeen )
-                          , gopt, hasPprDebug )
-import GHC.Driver.Ppr
-import GHC.Data.Maybe     ( orElse, catMaybes, isJust, isNothing )
 import GHC.Types.Demand
 import GHC.Types.Cpr
-import GHC.Serialized   ( deserializeWithData )
-import GHC.Utils.Misc
-import GHC.Data.Pair
 import GHC.Types.Unique.Supply
+import GHC.Types.Unique.FM
+
+import GHC.Data.Maybe     ( orElse, catMaybes, isJust, isNothing )
+import GHC.Data.Pair
+import GHC.Data.FastString
+
+import GHC.Utils.Misc
 import GHC.Utils.Outputable
 import GHC.Utils.Panic.Plain
 import GHC.Utils.Constants (debugIsOn)
-import GHC.Data.FastString
-import GHC.Types.Unique.FM
 import GHC.Utils.Monad
-import Control.Monad    ( zipWithM )
-import Data.List (nubBy, sortBy, partition, dropWhileEnd, mapAccumL )
+import GHC.Utils.Trace
+
 import GHC.Builtin.Names ( specTyConKey )
-import GHC.Unit.Module
+
 import GHC.Exts( SpecConstrAnnotation(..) )
+import GHC.Serialized   ( deserializeWithData )
+
+import Control.Monad    ( zipWithM )
+import Data.List (nubBy, sortBy, partition, dropWhileEnd, mapAccumL )
 import Data.Ord( comparing )
 
 {-
diff --git a/compiler/GHC/Core/Opt/Specialise.hs b/compiler/GHC/Core/Opt/Specialise.hs
index 1f0b6fb2a0..88f5d408de 100644
--- a/compiler/GHC/Core/Opt/Specialise.hs
+++ b/compiler/GHC/Core/Opt/Specialise.hs
@@ -42,6 +42,7 @@ import GHC.Builtin.Types  ( unboxedUnitTy )
 import GHC.Data.Maybe     ( mapMaybe, maybeToList, isJust )
 import GHC.Data.Bag
 import GHC.Data.FastString
+import GHC.Data.List.SetOps
 
 import GHC.Types.Basic
 import GHC.Types.Unique.Supply
@@ -60,6 +61,7 @@ import GHC.Utils.Monad    ( foldlM )
 import GHC.Utils.Misc
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
+import GHC.Utils.Trace
 
 import GHC.Unit.Module( Module )
 import GHC.Unit.Module.ModGuts
diff --git a/compiler/GHC/Core/Opt/WorkWrap.hs b/compiler/GHC/Core/Opt/WorkWrap.hs
index d7f4c1c0ee..58ac9f4c62 100644
--- a/compiler/GHC/Core/Opt/WorkWrap.hs
+++ b/compiler/GHC/Core/Opt/WorkWrap.hs
@@ -9,32 +9,35 @@ module GHC.Core.Opt.WorkWrap ( wwTopBinds ) where
 
 import GHC.Prelude
 
+import GHC.Driver.Session
+
 import GHC.Core.Opt.Arity  ( manifestArity )
 import GHC.Core
 import GHC.Core.Unfold
 import GHC.Core.Unfold.Make
 import GHC.Core.Utils  ( exprType, exprIsHNF )
 import GHC.Core.FVs    ( exprFreeVars )
+import GHC.Core.Type
+import GHC.Core.Opt.WorkWrap.Utils
+import GHC.Core.FamInstEnv
+import GHC.Core.SimpleOpt( SimpleOpts(..) )
+
 import GHC.Types.Var
 import GHC.Types.Id
 import GHC.Types.Id.Info
-import GHC.Core.Type
 import GHC.Types.Unique.Supply
 import GHC.Types.Basic
-import GHC.Driver.Session
-import GHC.Driver.Ppr
 import GHC.Types.Demand
 import GHC.Types.Cpr
 import GHC.Types.SourceText
-import GHC.Core.Opt.WorkWrap.Utils
-import GHC.Core.SimpleOpt( SimpleOpts(..) )
+import GHC.Types.Unique
+
 import GHC.Utils.Misc
 import GHC.Utils.Outputable
-import GHC.Types.Unique
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
-import GHC.Core.FamInstEnv
 import GHC.Utils.Monad
+import GHC.Utils.Trace
 
 {-
 We take Core bindings whose binders have:
diff --git a/compiler/GHC/Core/Opt/WorkWrap/Utils.hs b/compiler/GHC/Core/Opt/WorkWrap/Utils.hs
index 878bcdd068..3eb4b31c52 100644
--- a/compiler/GHC/Core/Opt/WorkWrap/Utils.hs
+++ b/compiler/GHC/Core/Opt/WorkWrap/Utils.hs
@@ -18,44 +18,48 @@ where
 
 import GHC.Prelude
 
+import GHC.Driver.Session
+import GHC.Driver.Config (initSimpleOpts)
+
 import GHC.Core
 import GHC.Core.Utils   ( exprType, mkCast, mkDefaultCase, mkSingleAltCase
                         , bindNonRec, dataConRepFSInstPat
                         , normSplitTyConApp_maybe, exprIsHNF )
-import GHC.Types.Id
-import GHC.Types.Id.Info ( JoinArity )
 import GHC.Core.DataCon
-import GHC.Types.Demand
-import GHC.Types.Cpr
 import GHC.Core.Make     ( mkAbsentErrorApp, mkCoreUbxTup, mkCoreApp, mkCoreLet
                          , mkWildValBinder, mkLitRubbish )
-import GHC.Types.Id.Make ( voidArgId, voidPrimId )
-import GHC.Builtin.Types ( tupleDataCon )
-import GHC.Types.Var.Env ( mkInScopeSet )
-import GHC.Types.Var.Set ( VarSet )
 import GHC.Core.Type
 import GHC.Core.Multiplicity
 import GHC.Core.Predicate ( isClassPred )
 import GHC.Core.Coercion
 import GHC.Core.FamInstEnv
-import GHC.Types.Basic       ( Boxity(..) )
 import GHC.Core.TyCon
 import GHC.Core.TyCon.RecWalk
 import GHC.Core.SimpleOpt( SimpleOpts )
 
+import GHC.Types.Id
+import GHC.Types.Id.Info ( JoinArity )
+import GHC.Types.Demand
+import GHC.Types.Cpr
+import GHC.Types.Id.Make ( voidArgId, voidPrimId )
+import GHC.Types.Var.Env ( mkInScopeSet )
+import GHC.Types.Var.Set ( VarSet )
+import GHC.Types.Basic       ( Boxity(..) )
 import GHC.Types.Unique.Supply
 import GHC.Types.Unique
 import GHC.Types.Name ( getOccFS )
+
+import GHC.Data.FastString
+import GHC.Data.OrdList
+import GHC.Data.List.SetOps
+
+import GHC.Builtin.Types ( tupleDataCon )
+
 import GHC.Utils.Misc
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
-import GHC.Driver.Session
-import GHC.Driver.Ppr
-import GHC.Driver.Config( initSimpleOpts )
-import GHC.Data.FastString
-import GHC.Data.OrdList
-import GHC.Data.List.SetOps
+import GHC.Utils.Trace
 
 import Control.Applicative ( (<|>) )
 import Control.Monad ( zipWithM )
diff --git a/compiler/GHC/Core/Rules.hs b/compiler/GHC/Core/Rules.hs
index 207e0b97a2..878b905929 100644
--- a/compiler/GHC/Core/Rules.hs
+++ b/compiler/GHC/Core/Rules.hs
@@ -27,10 +27,14 @@ module GHC.Core.Rules (
 
 import GHC.Prelude
 
-import GHC.Core         -- All of it
+import GHC.Driver.Session      ( DynFlags, gopt, targetPlatform, homeUnitId_ )
+import GHC.Driver.Flags
+
 import GHC.Unit.Types    ( primUnitId, bignumUnitId )
 import GHC.Unit.Module   ( Module )
 import GHC.Unit.Module.Env
+
+import GHC.Core         -- All of it
 import GHC.Core.Subst
 import GHC.Core.SimpleOpt ( exprIsLambda_maybe )
 import GHC.Core.FVs       ( exprFreeVars, exprsFreeVars, bindFreeVars
@@ -39,13 +43,16 @@ import GHC.Core.Utils     ( exprType, eqExpr, mkTick, mkTicks
                           , stripTicksTopT, stripTicksTopE
                           , isJoinBind )
 import GHC.Core.Ppr       ( pprRules )
+import GHC.Core.Unify as Unify ( ruleMatchTyKiX )
 import GHC.Core.Type as Type
    ( Type, TCvSubst, extendTvSubst, extendCvSubst
    , mkEmptyTCvSubst, substTy )
-import GHC.Tc.Utils.TcType  ( tcSplitTyConApp_maybe )
-import GHC.Builtin.Types    ( anyTypeOfKind )
 import GHC.Core.Coercion as Coercion
 import GHC.Core.Tidy     ( tidyRules )
+
+import GHC.Tc.Utils.TcType  ( tcSplitTyConApp_maybe )
+import GHC.Builtin.Types    ( anyTypeOfKind )
+
 import GHC.Types.Id
 import GHC.Types.Id.Info ( RuleInfo( RuleInfo ) )
 import GHC.Types.Var
@@ -56,18 +63,18 @@ import GHC.Types.Name.Set
 import GHC.Types.Name.Env
 import GHC.Types.Unique.FM
 import GHC.Types.Tickish
-import GHC.Core.Unify as Unify ( ruleMatchTyKiX )
 import GHC.Types.Basic
-import GHC.Driver.Session      ( DynFlags, gopt, targetPlatform, homeUnitId_ )
-import GHC.Driver.Ppr
-import GHC.Driver.Flags
-import GHC.Utils.Outputable
-import GHC.Utils.Panic
-import GHC.Utils.Constants (debugIsOn)
+
 import GHC.Data.FastString
 import GHC.Data.Maybe
 import GHC.Data.Bag
+
 import GHC.Utils.Misc as Utils
+import GHC.Utils.Trace
+import GHC.Utils.Outputable
+import GHC.Utils.Panic
+import GHC.Utils.Constants (debugIsOn)
+
 import Data.List (sortBy, mapAccumL, isPrefixOf)
 import Data.Function    ( on )
 import Control.Monad    ( guard )
diff --git a/compiler/GHC/Core/Subst.hs b/compiler/GHC/Core/Subst.hs
index 06aa024f16..3d93084fc4 100644
--- a/compiler/GHC/Core/Subst.hs
+++ b/compiler/GHC/Core/Subst.hs
@@ -36,8 +36,6 @@ module GHC.Core.Subst (
 
 import GHC.Prelude
 
-import GHC.Driver.Ppr
-
 import GHC.Core
 import GHC.Core.FVs
 import GHC.Core.Seq
@@ -51,7 +49,6 @@ import GHC.Core.Type hiding
    , isInScope, substTyVarBndr, cloneTyVarBndr )
 import GHC.Core.Coercion hiding ( substCo, substCoVarBndr )
 
-import GHC.Builtin.Names
 import GHC.Types.Var.Set
 import GHC.Types.Var.Env
 import GHC.Types.Id
@@ -60,11 +57,16 @@ import GHC.Types.Var
 import GHC.Types.Tickish
 import GHC.Types.Id.Info
 import GHC.Types.Unique.Supply
+
+import GHC.Builtin.Names
 import GHC.Data.Maybe
+
+import GHC.Utils.Trace
 import GHC.Utils.Misc
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
+
 import Data.List (mapAccumL)
 
 
diff --git a/compiler/GHC/Core/Unfold.hs b/compiler/GHC/Core/Unfold.hs
index 55561c9cbc..fc05566d9f 100644
--- a/compiler/GHC/Core/Unfold.hs
+++ b/compiler/GHC/Core/Unfold.hs
@@ -40,7 +40,6 @@ module GHC.Core.Unfold (
 
 import GHC.Prelude
 
-import GHC.Driver.Ppr
 import GHC.Driver.Flags
 
 import GHC.Core
@@ -1295,7 +1294,7 @@ tryUnfolding logger opts !case_depth id lone_variable
              , text "ANSWER =" <+> if yes_or_no then text "YES" else text "NO"]
 
     ctx = log_default_dump_context (logFlags logger)
-    str = "Considering inlining: " ++ showSDocDump ctx (ppr id)
+    str = "Considering inlining: " ++ renderWithContext ctx (ppr id)
     n_val_args = length arg_infos
 
            -- some_benefit is used when the RHS is small enough
diff --git a/compiler/GHC/Core/Utils.hs b/compiler/GHC/Core/Utils.hs
index 3ec00d76be..969ede72bc 100644
--- a/compiler/GHC/Core/Utils.hs
+++ b/compiler/GHC/Core/Utils.hs
@@ -67,12 +67,21 @@ module GHC.Core.Utils (
 import GHC.Prelude
 import GHC.Platform
 
-import GHC.Driver.Ppr
-
 import GHC.Core
-import GHC.Builtin.Names (makeStaticName, unsafeEqualityProofName)
 import GHC.Core.Ppr
 import GHC.Core.FVs( exprFreeVars )
+import GHC.Core.DataCon
+import GHC.Core.Type as Type
+import GHC.Core.FamInstEnv
+import GHC.Core.Predicate
+import GHC.Core.TyCo.Rep( TyCoBinder(..), TyBinder )
+import GHC.Core.Coercion
+import GHC.Core.TyCon
+import GHC.Core.Multiplicity
+
+import GHC.Builtin.Names (makeStaticName, unsafeEqualityProofName)
+import GHC.Builtin.PrimOps
+
 import GHC.Types.Var
 import GHC.Types.SrcLoc
 import GHC.Types.Var.Env
@@ -80,35 +89,30 @@ import GHC.Types.Var.Set
 import GHC.Types.Name
 import GHC.Types.Literal
 import GHC.Types.Tickish
-import GHC.Core.DataCon
-import GHC.Builtin.PrimOps
 import GHC.Types.Id
 import GHC.Types.Id.Info
-import GHC.Core.Type as Type
-import GHC.Core.FamInstEnv
-import GHC.Core.Predicate
-import GHC.Core.TyCo.Rep( TyCoBinder(..), TyBinder )
-import GHC.Core.Coercion
-import GHC.Core.TyCon
-import GHC.Core.Multiplicity
 import GHC.Types.Unique
+import GHC.Types.Basic     ( Arity, FullArgCount )
+import GHC.Types.Unique.Set
+
+import GHC.Data.FastString
+import GHC.Data.Maybe
+import GHC.Data.List.SetOps( minusList )
+import GHC.Data.Pair
+import GHC.Data.OrdList
+
 import GHC.Utils.Constants (debugIsOn)
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
-import GHC.Data.FastString
-import GHC.Data.Maybe
-import GHC.Data.List.SetOps( minusList )
-import GHC.Types.Basic     ( Arity, FullArgCount )
 import GHC.Utils.Misc
-import GHC.Data.Pair
+import GHC.Utils.Trace
+
 import Data.ByteString     ( ByteString )
 import Data.Function       ( on )
 import Data.List           ( sort, sortBy, partition, zipWith4, mapAccumL )
 import Data.Ord            ( comparing )
-import GHC.Data.OrdList
 import qualified Data.Set as Set
-import GHC.Types.Unique.Set
 
 {-
 ************************************************************************
diff --git a/compiler/GHC/CoreToIface.hs b/compiler/GHC/CoreToIface.hs
index a1c8d0fe78..4ca3065ece 100644
--- a/compiler/GHC/CoreToIface.hs
+++ b/compiler/GHC/CoreToIface.hs
@@ -46,38 +46,43 @@ module GHC.CoreToIface
 
 import GHC.Prelude
 
-import GHC.Driver.Ppr
-import GHC.Iface.Syntax
-import GHC.Core.DataCon
-import GHC.Types.Id
-import GHC.Types.Literal
-import GHC.Types.Id.Info
 import GHC.StgToCmm.Types
+
 import GHC.Core
 import GHC.Core.TyCon hiding ( pprPromotionQuote )
 import GHC.Core.Coercion.Axiom
+import GHC.Core.DataCon
+import GHC.Core.Type
+import GHC.Core.Multiplicity
+import GHC.Core.PatSyn
+import GHC.Core.TyCo.Rep
+import GHC.Core.TyCo.Tidy ( tidyCo )
+
 import GHC.Builtin.Types.Prim ( eqPrimTyCon, eqReprPrimTyCon )
 import GHC.Builtin.Types ( heqTyCon )
-import GHC.Types.Id.Make ( noinlineIdName )
 import GHC.Builtin.Names
+
+import GHC.Iface.Syntax
+import GHC.Data.FastString
+
+import GHC.Types.Id
+import GHC.Types.Id.Info
+import GHC.Types.Id.Make ( noinlineIdName )
+import GHC.Types.Literal
 import GHC.Types.Name
 import GHC.Types.Basic
-import GHC.Core.Type
-import GHC.Core.Multiplicity
-import GHC.Core.PatSyn
-import GHC.Utils.Outputable
-import GHC.Utils.Panic
-import GHC.Data.FastString
-import GHC.Utils.Misc
 import GHC.Types.Var
 import GHC.Types.Var.Env
 import GHC.Types.Var.Set
 import GHC.Types.Tickish
-import GHC.Core.TyCo.Rep
-import GHC.Core.TyCo.Tidy ( tidyCo )
 import GHC.Types.Demand ( isTopSig )
 import GHC.Types.Cpr ( topCprSig )
 
+import GHC.Utils.Outputable
+import GHC.Utils.Panic
+import GHC.Utils.Misc
+import GHC.Utils.Trace
+
 import Data.Maybe ( catMaybes )
 
 {- Note [Avoiding space leaks in toIface*]
@@ -297,7 +302,7 @@ toIfaceCoercionX fr co
                                           (toIfaceTypeX fr t2)
     go (TyConAppCo r tc cos)
       | tc `hasKey` funTyConKey
-      , [_,_,_,_, _] <- cos         = pprPanic "toIfaceCoercion" empty
+      , [_,_,_,_, _] <- cos         = panic "toIfaceCoercion"
       | otherwise                =
         IfaceTyConAppCo r (toIfaceTyCon tc) (map go cos)
     go (FunCo r w co1 co2)   = IfaceFunCo r (go w) (go co1) (go co2)
diff --git a/compiler/GHC/CoreToStg.hs b/compiler/GHC/CoreToStg.hs
index bf20cc4286..38050e79e1 100644
--- a/compiler/GHC/CoreToStg.hs
+++ b/compiler/GHC/CoreToStg.hs
@@ -17,42 +17,46 @@ module GHC.CoreToStg ( coreToStg ) where
 
 import GHC.Prelude
 
+import GHC.Driver.Session
+
 import GHC.Core
 import GHC.Core.Utils   ( exprType, findDefault, isJoinBind
                         , exprIsTickedString_maybe )
 import GHC.Core.Opt.Arity   ( manifestArity )
+import GHC.Core.Type
+import GHC.Core.TyCon
+import GHC.Core.DataCon
+
 import GHC.Stg.Syntax
 import GHC.Stg.Debug
 
-import GHC.Core.Type
 import GHC.Types.RepType
-import GHC.Core.TyCon
 import GHC.Types.Id.Make ( coercionTokenId )
 import GHC.Types.Id
 import GHC.Types.Id.Info
-import GHC.Core.DataCon
 import GHC.Types.CostCentre
 import GHC.Types.Tickish
 import GHC.Types.Var.Env
-import GHC.Unit.Module
 import GHC.Types.Name   ( isExternalName, nameModule_maybe )
 import GHC.Types.Basic  ( Arity )
-import GHC.Builtin.Types ( unboxedUnitDataCon )
 import GHC.Types.Literal
+import GHC.Types.ForeignCall
+import GHC.Types.IPE
+import GHC.Types.Demand    ( isUsedOnceDmd )
+import GHC.Types.SrcLoc    ( mkGeneralSrcSpan )
+
+import GHC.Unit.Module
+import GHC.Builtin.Types ( unboxedUnitDataCon )
+import GHC.Data.FastString
+import GHC.Platform.Ways
+import GHC.Builtin.PrimOps ( PrimCall(..) )
+
 import GHC.Utils.Outputable
 import GHC.Utils.Monad
 import GHC.Utils.Misc (HasDebugCallStack)
-import GHC.Data.FastString
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
-import GHC.Driver.Session
-import GHC.Platform.Ways
-import GHC.Driver.Ppr
-import GHC.Types.ForeignCall
-import GHC.Types.IPE
-import GHC.Types.Demand    ( isUsedOnceDmd )
-import GHC.Builtin.PrimOps ( PrimCall(..) )
-import GHC.Types.SrcLoc    ( mkGeneralSrcSpan )
+import GHC.Utils.Trace
 
 import Control.Monad (ap)
 import Data.Maybe (fromMaybe)
diff --git a/compiler/GHC/CoreToStg/Prep.hs b/compiler/GHC/CoreToStg/Prep.hs
index 4529bc7d1b..30c28a6db2 100644
--- a/compiler/GHC/CoreToStg/Prep.hs
+++ b/compiler/GHC/CoreToStg/Prep.hs
@@ -32,7 +32,6 @@ import GHC.Builtin.Names
 import GHC.Builtin.PrimOps
 import GHC.Builtin.Types
 import GHC.Builtin.Types.Prim ( realWorldStatePrimTy )
-import GHC.Types.Id.Make ( realWorldPrimId, mkPrimOpId )
 
 import GHC.Core.Utils
 import GHC.Core.Opt.Arity
@@ -48,10 +47,10 @@ import GHC.Core.DataCon
 import GHC.Core.Opt.OccurAnal
 import GHC.Core.TyCo.Rep( UnivCoProvenance(..) )
 
-
 import GHC.Data.Maybe
 import GHC.Data.OrdList
 import GHC.Data.FastString
+import GHC.Data.Pair
 
 import GHC.Utils.Error
 import GHC.Utils.Misc
@@ -60,6 +59,7 @@ import GHC.Utils.Panic.Plain
 import GHC.Utils.Outputable
 import GHC.Utils.Monad  ( mapAccumLM )
 import GHC.Utils.Logger
+import GHC.Utils.Trace
 
 import GHC.Types.Demand
 import GHC.Types.Var
@@ -67,6 +67,7 @@ import GHC.Types.Var.Set
 import GHC.Types.Var.Env
 import GHC.Types.Id
 import GHC.Types.Id.Info
+import GHC.Types.Id.Make ( realWorldPrimId, mkPrimOpId )
 import GHC.Types.Basic
 import GHC.Types.Name   ( NamedThing(..), nameSrcSpan, isInternalName )
 import GHC.Types.SrcLoc ( SrcSpan(..), realSrcLocSpan, mkRealSrcLoc )
@@ -75,7 +76,6 @@ import GHC.Types.Tickish
 import GHC.Types.TyThing
 import GHC.Types.Unique.Supply
 
-import GHC.Data.Pair
 import Data.List        ( unfoldr )
 import Data.Functor.Identity
 import Control.Monad
diff --git a/compiler/GHC/Data/Bool.hs b/compiler/GHC/Data/Bool.hs
new file mode 100644
index 0000000000..1428e7d2fd
--- /dev/null
+++ b/compiler/GHC/Data/Bool.hs
@@ -0,0 +1,18 @@
+module GHC.Data.Bool
+  ( OverridingBool(..)
+  , overrideWith
+  )
+where
+
+import GHC.Prelude
+
+data OverridingBool
+  = Auto
+  | Always
+  | Never
+  deriving Show
+
+overrideWith :: Bool -> OverridingBool -> Bool
+overrideWith b Auto   = b
+overrideWith _ Always = True
+overrideWith _ Never  = False
diff --git a/compiler/GHC/Data/List/SetOps.hs b/compiler/GHC/Data/List/SetOps.hs
index 76e421c940..fac12fadd8 100644
--- a/compiler/GHC/Data/List/SetOps.hs
+++ b/compiler/GHC/Data/List/SetOps.hs
@@ -1,3 +1,5 @@
+{-# LANGUAGE CPP #-}
+
 {-
 (c) The University of Glasgow 2006
 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
@@ -20,7 +22,10 @@ module GHC.Data.List.SetOps (
         equivClasses,
 
         -- Indexing
-        getNth
+        getNth,
+
+        -- Membership
+        isIn, isn'tIn,
    ) where
 
 import GHC.Prelude
@@ -28,7 +33,7 @@ import GHC.Prelude
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Misc
-import GHC.Driver.Ppr
+import GHC.Utils.Trace
 
 import qualified Data.List as L
 import qualified Data.List.NonEmpty as NE
@@ -176,3 +181,31 @@ findDupsEq _  [] = []
 findDupsEq eq (x:xs) | L.null eq_xs  = findDupsEq eq xs
                      | otherwise     = (x :| eq_xs) : findDupsEq eq neq_xs
     where (eq_xs, neq_xs) = L.partition (eq x) xs
+
+-- Debugging/specialising versions of \tr{elem} and \tr{notElem}
+
+# if !defined(DEBUG)
+isIn, isn'tIn :: Eq a => String -> a -> [a] -> Bool
+isIn    _msg x ys = x `elem` ys
+isn'tIn _msg x ys = x `notElem` ys
+
+# else /* DEBUG */
+isIn, isn'tIn :: (HasDebugCallStack, Eq a) => String -> a -> [a] -> Bool
+isIn msg x ys
+  = elem100 0 x ys
+  where
+    elem100 :: Eq a => Int -> a -> [a] -> Bool
+    elem100 _ _ [] = False
+    elem100 i x (y:ys)
+      | i > 100 = warnPprTrace True (text ("Over-long elem in " ++ msg)) (x `elem` (y:ys))
+      | otherwise = x == y || elem100 (i + 1) x ys
+
+isn'tIn msg x ys
+  = notElem100 0 x ys
+  where
+    notElem100 :: Eq a => Int -> a -> [a] -> Bool
+    notElem100 _ _ [] =  True
+    notElem100 i x (y:ys)
+      | i > 100 = warnPprTrace True (text ("Over-long notElem in " ++ msg)) (x `notElem` (y:ys))
+      | otherwise = x /= y && notElem100 (i + 1) x ys
+# endif /* DEBUG */
diff --git a/compiler/GHC/Driver/CodeOutput.hs b/compiler/GHC/Driver/CodeOutput.hs
index 7c9c08e4c1..e0b8879fd9 100644
--- a/compiler/GHC/Driver/CodeOutput.hs
+++ b/compiler/GHC/Driver/CodeOutput.hs
@@ -43,6 +43,7 @@ import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Logger
 import GHC.Utils.Exception (bracket)
+import GHC.Utils.Ppr (Mode(..))
 
 import GHC.Unit
 import GHC.Unit.State
@@ -148,7 +149,8 @@ outputC logger dflags filenm cmm_stream packages =
                           "C backend output"
                           FormatC
                           doc
-            printForC dflags h doc
+            let ctx = initSDocContext dflags (PprCode CStyle)
+            printSDocLn ctx LeftMode h doc
       Stream.consume cmm_stream id writeC
 
 {-
diff --git a/compiler/GHC/Driver/Env.hs b/compiler/GHC/Driver/Env.hs
index 6606f551e5..cbddfa0ef3 100644
--- a/compiler/GHC/Driver/Env.hs
+++ b/compiler/GHC/Driver/Env.hs
@@ -32,15 +32,14 @@ where
 
 import GHC.Prelude
 
-import GHC.Driver.Ppr
 import GHC.Driver.Session
 import GHC.Driver.Errors ( printOrThrowDiagnostics )
 import GHC.Driver.Errors.Types ( GhcMessage )
 import GHC.Driver.Config.Logger (initLogFlags)
+import GHC.Driver.Env.Types ( Hsc(..), HscEnv(..) )
 
 import GHC.Runtime.Context
 import GHC.Runtime.Interpreter.Types (Interp)
-import GHC.Driver.Env.Types ( Hsc(..), HscEnv(..) )
 
 import GHC.Unit
 import GHC.Unit.Module.ModGuts
@@ -61,6 +60,7 @@ import GHC.Types.Error ( emptyMessages, Messages )
 import GHC.Types.Name
 import GHC.Types.Name.Env
 import GHC.Types.TyThing
+import GHC.Types.Unique.FM
 
 import GHC.Builtin.Names ( gHC_PRIM )
 
@@ -72,7 +72,7 @@ import GHC.Utils.Monad
 import GHC.Utils.Panic
 import GHC.Utils.Misc
 import GHC.Utils.Logger
-import GHC.Types.Unique.FM
+import GHC.Utils.Trace
 
 import Data.IORef
 import qualified Data.Set as Set
diff --git a/compiler/GHC/Driver/Ppr.hs b/compiler/GHC/Driver/Ppr.hs
index a43f9eaa1d..49188d08f0 100644
--- a/compiler/GHC/Driver/Ppr.hs
+++ b/compiler/GHC/Driver/Ppr.hs
@@ -3,39 +3,21 @@ module GHC.Driver.Ppr
    ( showSDoc
    , showSDocUnsafe
    , showSDocForUser
-   , showSDocDebug
-   , showSDocDump
    , showPpr
    , showPprUnsafe
-   , pprDebugAndThen
    , printForUser
-   , printForC
-   -- ** Trace
-   , warnPprTrace
-   , pprTrace
-   , pprTraceM
-   , pprTraceDebug
-   , pprTraceIt
-   , pprSTrace
-   , pprTraceException
    )
 where
 
 import GHC.Prelude
 
-import {-# SOURCE #-} GHC.Driver.Session
+import GHC.Driver.Session
 import {-# SOURCE #-} GHC.Unit.State
 
-import GHC.Utils.Exception
-import GHC.Utils.Constants (debugIsOn)
-import GHC.Utils.Misc
 import GHC.Utils.Outputable
-import GHC.Utils.Panic
-import GHC.Utils.GlobalVars
 import GHC.Utils.Ppr       ( Mode(..) )
 
 import System.IO ( Handle )
-import Control.Monad.IO.Class
 
 -- | Show a SDoc as a String with the default user style
 showSDoc :: DynFlags -> SDoc -> String
@@ -51,77 +33,7 @@ showSDocForUser dflags unit_state unqual doc = renderWithContext (initSDocContex
       sty  = mkUserStyle unqual AllTheWay
       doc' = pprWithUnitState unit_state doc
 
-showSDocDump :: SDocContext -> SDoc -> String
-showSDocDump ctx d = renderWithContext ctx (withPprStyle defaultDumpStyle d)
-
-showSDocDebug :: DynFlags -> SDoc -> String
-showSDocDebug dflags d = renderWithContext ctx d
-   where
-      ctx = (initSDocContext dflags defaultDumpStyle)
-               { sdocPprDebug = True
-               }
-
 printForUser :: DynFlags -> Handle -> PrintUnqualified -> Depth -> SDoc -> IO ()
 printForUser dflags handle unqual depth doc
   = printSDocLn ctx (PageMode False) handle doc
     where ctx = initSDocContext dflags (mkUserStyle unqual depth)
-
--- | Like 'printSDocLn' but specialized with 'LeftMode' and
--- @'PprCode' 'CStyle'@.  This is typically used to output C-- code.
-printForC :: DynFlags -> Handle -> SDoc -> IO ()
-printForC dflags handle doc =
-  printSDocLn ctx LeftMode handle doc
-  where ctx = initSDocContext dflags (PprCode CStyle)
-
-pprDebugAndThen :: SDocContext -> (String -> a) -> SDoc -> SDoc -> a
-pprDebugAndThen ctx cont heading pretty_msg
- = cont (showSDocDump ctx doc)
- where
-     doc = sep [heading, nest 2 pretty_msg]
-
--- | If debug output is on, show some 'SDoc' on the screen
-pprTrace :: String -> SDoc -> a -> a
-pprTrace str doc x
-  | unsafeHasNoDebugOutput = x
-  | otherwise              = pprDebugAndThen defaultSDocContext trace (text str) doc x
-
-pprTraceM :: Applicative f => String -> SDoc -> f ()
-pprTraceM str doc = pprTrace str doc (pure ())
-
-pprTraceDebug :: String -> SDoc -> a -> a
-pprTraceDebug str doc x
-   | debugIsOn && unsafeHasPprDebug = pprTrace str doc x
-   | otherwise                      = x
-
--- | @pprTraceWith desc f x@ is equivalent to @pprTrace desc (f x) x@.
--- This allows you to print details from the returned value as well as from
--- ambient variables.
-pprTraceWith :: String -> (a -> SDoc) -> a -> a
-pprTraceWith desc f x = pprTrace desc (f x) x
-
--- | @pprTraceIt desc x@ is equivalent to @pprTrace desc (ppr x) x@
-pprTraceIt :: Outputable a => String -> a -> a
-pprTraceIt desc x = pprTraceWith desc ppr x
-
--- | @pprTraceException desc x action@ runs action, printing a message
--- if it throws an exception.
-pprTraceException :: ExceptionMonad m => String -> SDoc -> m a -> m a
-pprTraceException heading doc =
-    handleGhcException $ \exc -> liftIO $ do
-        putStrLn $ showSDocDump defaultSDocContext (sep [text heading, nest 2 doc])
-        throwGhcExceptionIO exc
-
--- | If debug output is on, show some 'SDoc' on the screen along
--- with a call stack when available.
-pprSTrace :: HasCallStack => SDoc -> a -> a
-pprSTrace doc = pprTrace "" (doc $$ callStackDoc)
-
--- | Just warn about an assertion failure, recording the given file and line number.
-warnPprTrace :: HasCallStack => Bool -> SDoc -> a -> a
-warnPprTrace _     _    x | not debugIsOn     = x
-warnPprTrace _     _msg x | unsafeHasNoDebugOutput = x
-warnPprTrace False _msg x = x
-warnPprTrace True   msg x
-  = pprDebugAndThen defaultSDocContext trace (text "WARNING:")
-                    (msg $$ callStackDoc )
-                    x
diff --git a/compiler/GHC/Driver/Ppr.hs-boot b/compiler/GHC/Driver/Ppr.hs-boot
deleted file mode 100644
index 58f812d6d8..0000000000
--- a/compiler/GHC/Driver/Ppr.hs-boot
+++ /dev/null
@@ -1,9 +0,0 @@
-module GHC.Driver.Ppr where
-
-import GHC.Prelude
-import GHC.Stack
-import {-# SOURCE #-} GHC.Driver.Session
-import {-# SOURCE #-} GHC.Utils.Outputable
-
-showSDoc :: DynFlags -> SDoc -> String
-warnPprTrace :: HasCallStack => Bool -> SDoc -> a -> a
diff --git a/compiler/GHC/Driver/Session.hs b/compiler/GHC/Driver/Session.hs
index d51fa4d8f2..d35e0d96d4 100644
--- a/compiler/GHC/Driver/Session.hs
+++ b/compiler/GHC/Driver/Session.hs
@@ -241,6 +241,7 @@ import GHC.Utils.Misc
 import GHC.Utils.Constants (debugIsOn)
 import GHC.Utils.GlobalVars
 import GHC.Data.Maybe
+import GHC.Data.Bool
 import GHC.Utils.Monad
 import GHC.Types.Error (DiagnosticReason(..))
 import GHC.Types.SrcLoc
diff --git a/compiler/GHC/HsToCore/Binds.hs b/compiler/GHC/HsToCore/Binds.hs
index 184dda1481..01a8d1d9a5 100644
--- a/compiler/GHC/HsToCore/Binds.hs
+++ b/compiler/GHC/HsToCore/Binds.hs
@@ -24,6 +24,12 @@ where
 
 import GHC.Prelude
 
+import GHC.Driver.Session
+import GHC.Driver.Ppr
+import GHC.Driver.Config
+import qualified GHC.LanguageExtensions as LangExt
+import GHC.Unit.Module
+
 import {-# SOURCE #-}   GHC.HsToCore.Expr  ( dsLExpr )
 import {-# SOURCE #-}   GHC.HsToCore.Match ( matchWrapper )
 
@@ -42,41 +48,41 @@ import GHC.Core.Utils
 import GHC.Core.Opt.Arity     ( etaExpand )
 import GHC.Core.Unfold.Make
 import GHC.Core.FVs
-import GHC.Data.Graph.Directed
 import GHC.Core.Predicate
-
-import GHC.Builtin.Names
 import GHC.Core.TyCon
-import GHC.Tc.Types.Evidence
-import GHC.Tc.Utils.TcType
 import GHC.Core.Type
 import GHC.Core.Coercion
 import GHC.Core.Multiplicity
+import GHC.Core.Rules
+
+import GHC.Builtin.Names
 import GHC.Builtin.Types ( naturalTy, typeSymbolKind, charTy )
+
+import GHC.Tc.Types.Evidence
+
 import GHC.Types.Id
 import GHC.Types.Name
 import GHC.Types.Var.Set
-import GHC.Core.Rules
 import GHC.Types.Var.Env
 import GHC.Types.Var( EvVar )
-import GHC.Utils.Outputable
-import GHC.Utils.Panic
-import GHC.Utils.Panic.Plain
-import GHC.Utils.Constants (debugIsOn)
-import GHC.Unit.Module
 import GHC.Types.SrcLoc
+import GHC.Types.Basic
+import GHC.Types.Unique.Set( nonDetEltsUniqSet )
+
 import GHC.Data.Maybe
 import GHC.Data.OrdList
+import GHC.Data.Graph.Directed
 import GHC.Data.Bag
-import GHC.Types.Basic
-import GHC.Driver.Session
-import GHC.Driver.Ppr
-import GHC.Driver.Config
 import GHC.Data.FastString
+
+import GHC.Utils.Constants (debugIsOn)
 import GHC.Utils.Misc
-import GHC.Types.Unique.Set( nonDetEltsUniqSet )
 import GHC.Utils.Monad
-import qualified GHC.LanguageExtensions as LangExt
+import GHC.Utils.Outputable
+import GHC.Utils.Panic
+import GHC.Utils.Panic.Plain
+import GHC.Utils.Trace
+
 import Control.Monad
 
 {-**********************************************************************
diff --git a/compiler/GHC/Iface/Load.hs b/compiler/GHC/Iface/Load.hs
index eac1ba3e9d..cc7a154b2a 100644
--- a/compiler/GHC/Iface/Load.hs
+++ b/compiler/GHC/Iface/Load.hs
@@ -47,7 +47,6 @@ import GHC.Driver.Env
 import GHC.Driver.Errors.Types
 import GHC.Driver.Session
 import GHC.Driver.Backend
-import GHC.Driver.Ppr
 import GHC.Driver.Hooks
 import GHC.Driver.Plugins
 
@@ -67,6 +66,7 @@ import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
 import GHC.Utils.Constants (debugIsOn)
 import GHC.Utils.Logger
+import GHC.Utils.Trace
 
 import GHC.Settings.Constants
 
diff --git a/compiler/GHC/Iface/Make.hs b/compiler/GHC/Iface/Make.hs
index 4af7ddbf05..7421eac86d 100644
--- a/compiler/GHC/Iface/Make.hs
+++ b/compiler/GHC/Iface/Make.hs
@@ -51,7 +51,6 @@ import GHC.Core.Unify( RoughMatchTc(..) )
 import GHC.Driver.Env
 import GHC.Driver.Backend
 import GHC.Driver.Session
-import GHC.Driver.Ppr
 import GHC.Driver.Plugins (LoadedPlugin(..))
 
 import GHC.Types.Id
@@ -77,6 +76,7 @@ import GHC.Utils.Outputable
 import GHC.Utils.Panic.Plain
 import GHC.Utils.Misc  hiding ( eqListBy )
 import GHC.Utils.Logger
+import GHC.Utils.Trace
 
 import GHC.Data.FastString
 import GHC.Data.Maybe
diff --git a/compiler/GHC/Iface/Recomp.hs b/compiler/GHC/Iface/Recomp.hs
index 7759aea72d..9bfbe218d6 100644
--- a/compiler/GHC/Iface/Recomp.hs
+++ b/compiler/GHC/Iface/Recomp.hs
@@ -42,6 +42,7 @@ import GHC.Utils.Fingerprint
 import GHC.Utils.Exception
 import GHC.Utils.Logger
 import GHC.Utils.Constants (debugIsOn)
+import GHC.Utils.Trace
 
 import GHC.Types.Annotations
 import GHC.Types.Name
diff --git a/compiler/GHC/Iface/Tidy.hs b/compiler/GHC/Iface/Tidy.hs
index 3285fb88e5..2a6f9ecbca 100644
--- a/compiler/GHC/Iface/Tidy.hs
+++ b/compiler/GHC/Iface/Tidy.hs
@@ -47,6 +47,7 @@ import GHC.Iface.Env
 import GHC.Utils.Outputable
 import GHC.Utils.Misc( filterOut )
 import GHC.Utils.Panic
+import GHC.Utils.Trace
 import GHC.Utils.Logger as Logger
 import qualified GHC.Utils.Error as Err
 
diff --git a/compiler/GHC/Parser/Lexer.x b/compiler/GHC/Parser/Lexer.x
index 1466e7da71..7c9b951eba 100644
--- a/compiler/GHC/Parser/Lexer.x
+++ b/compiler/GHC/Parser/Lexer.x
@@ -89,6 +89,7 @@ import Data.Char
 import Data.List (stripPrefix, isInfixOf, partition)
 import Data.Maybe
 import Data.Word
+import Debug.Trace (trace)
 
 import GHC.Data.EnumSet as EnumSet
 
diff --git a/compiler/GHC/Rename/Names.hs b/compiler/GHC/Rename/Names.hs
index 05bbb71c6e..7fbbb7167e 100644
--- a/compiler/GHC/Rename/Names.hs
+++ b/compiler/GHC/Rename/Names.hs
@@ -55,6 +55,7 @@ import qualified GHC.LanguageExtensions as LangExt
 import GHC.Utils.Outputable as Outputable
 import GHC.Utils.Misc as Utils
 import GHC.Utils.Panic
+import GHC.Utils.Trace
 
 import GHC.Types.Fixity.Env
 import GHC.Types.SafeHaskell
diff --git a/compiler/GHC/Runtime/Eval.hs b/compiler/GHC/Runtime/Eval.hs
index 1c3c72d228..e28b2daeba 100644
--- a/compiler/GHC/Runtime/Eval.hs
+++ b/compiler/GHC/Runtime/Eval.hs
@@ -93,6 +93,7 @@ import GHC.Utils.Error
 import GHC.Utils.Outputable
 import GHC.Utils.Misc
 import GHC.Utils.Logger
+import GHC.Utils.Trace
 
 import GHC.Types.RepType
 import GHC.Types.Fixity.Env
diff --git a/compiler/GHC/Stg/Pipeline.hs b/compiler/GHC/Stg/Pipeline.hs
index 5754b23baa..57996cbffa 100644
--- a/compiler/GHC/Stg/Pipeline.hs
+++ b/compiler/GHC/Stg/Pipeline.hs
@@ -28,7 +28,6 @@ import GHC.Driver.Session
 import GHC.Utils.Error
 import GHC.Types.Unique.Supply
 import GHC.Utils.Outputable
-import GHC.Utils.Panic
 import GHC.Utils.Logger
 import Control.Monad
 import Control.Monad.IO.Class
@@ -86,7 +85,7 @@ stg2stg logger dflags ictxt this_mod binds
             return binds
 
           StgStats ->
-            trace (showStgStats binds) (return binds)
+            logTraceMsg logger "STG stats" (text (showStgStats binds)) (return binds)
 
           StgCSE -> do
             let binds' = {-# SCC "StgCse" #-} stgCse binds
diff --git a/compiler/GHC/Stg/Subst.hs b/compiler/GHC/Stg/Subst.hs
index d47107bb35..487b8b8adc 100644
--- a/compiler/GHC/Stg/Subst.hs
+++ b/compiler/GHC/Stg/Subst.hs
@@ -11,8 +11,7 @@ import GHC.Utils.Monad.State.Strict
 import GHC.Utils.Outputable
 import GHC.Utils.Misc
 import GHC.Utils.Panic
-
-import GHC.Driver.Ppr
+import GHC.Utils.Trace
 
 -- | A renaming substitution from 'Id's to 'Id's. Like 'RnEnv2', but not
 -- maintaining pairs of substitutions. Like 'GHC.Core.Subst.Subst', but
diff --git a/compiler/GHC/StgToCmm/Bind.hs b/compiler/GHC/StgToCmm/Bind.hs
index 13b07c2dd2..7d89b71309 100644
--- a/compiler/GHC/StgToCmm/Bind.hs
+++ b/compiler/GHC/StgToCmm/Bind.hs
@@ -15,6 +15,14 @@ module GHC.StgToCmm.Bind (
 
 import GHC.Prelude hiding ((<*>))
 
+import GHC.Driver.Session
+
+import GHC.Core          ( AltCon(..) )
+import GHC.Runtime.Heap.Layout
+import GHC.Unit.Module
+
+import GHC.Stg.Syntax
+
 import GHC.Platform
 import GHC.Platform.Profile
 
@@ -32,29 +40,26 @@ import GHC.StgToCmm.Closure
 import GHC.StgToCmm.Foreign    (emitPrimCall)
 
 import GHC.Cmm.Graph
-import GHC.Core          ( AltCon(..) )
 import GHC.Cmm.BlockId
-import GHC.Runtime.Heap.Layout
 import GHC.Cmm
 import GHC.Cmm.Info
 import GHC.Cmm.Utils
 import GHC.Cmm.CLabel
-import GHC.Stg.Syntax
+
 import GHC.Types.CostCentre
 import GHC.Types.Id
 import GHC.Types.Id.Info
 import GHC.Types.Name
-import GHC.Unit.Module
-import GHC.Data.List.SetOps
-import GHC.Utils.Misc
 import GHC.Types.Var.Set
 import GHC.Types.Basic
 import GHC.Types.Tickish ( tickishIsCode )
+
+import GHC.Utils.Misc
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
+
 import GHC.Data.FastString
-import GHC.Driver.Session
-import GHC.Driver.Ppr
+import GHC.Data.List.SetOps
 
 import Control.Monad
 
@@ -764,9 +769,10 @@ closureDescription
         -- Not called for StgRhsCon which have global info tables built in
         -- CgConTbls.hs with a description generated from the data constructor
 closureDescription dflags mod_name name
-  = showSDocDump (initSDocContext dflags defaultDumpStyle) (char '<' <>
+  = let ctx = initSDocContext dflags defaultDumpStyle
+    -- defaultDumpStyle, because we want to see the unique on the Name.
+    in renderWithContext ctx (char '<' <>
                     (if isExternalName name
                       then ppr name -- ppr will include the module name prefix
                       else pprModule mod_name <> char '.' <> ppr name) <>
                     char '>')
-   -- showSDocDump, because we want to see the unique on the Name.
diff --git a/compiler/GHC/StgToCmm/Ticky.hs b/compiler/GHC/StgToCmm/Ticky.hs
index e9e67f6b83..76748f2b0d 100644
--- a/compiler/GHC/StgToCmm/Ticky.hs
+++ b/compiler/GHC/StgToCmm/Ticky.hs
@@ -102,6 +102,8 @@ module GHC.StgToCmm.Ticky (
 
 import GHC.Prelude
 
+import GHC.Driver.Session
+
 import GHC.Platform
 import GHC.Platform.Profile
 
@@ -126,9 +128,6 @@ import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Misc
 
-import GHC.Driver.Session
-import GHC.Driver.Ppr
-
 -- Turgid imports for showTypeCategory
 import GHC.Builtin.Names
 import GHC.Tc.Utils.TcType
@@ -243,7 +242,9 @@ emitTickyCounter cloType name args
                    then n <+> parens (ppr mod_name) <+> ext <+> p
                    else n <+> ext <+> p
 
-        ; fun_descr_lit <- newStringCLit $ showSDocDebug dflags ppr_for_ticky_name
+        ; let ctx = (initSDocContext dflags defaultDumpStyle)
+                      { sdocPprDebug = True }
+        ; fun_descr_lit <- newStringCLit $ renderWithContext ctx ppr_for_ticky_name
         ; arg_descr_lit <- newStringCLit $ map (showTypeCategory . idType . fromNonVoid) args
         ; emitDataLits ctr_lbl
         -- Must match layout of includes/rts/Ticky.h's StgEntCounter
diff --git a/compiler/GHC/Tc/Gen/Sig.hs b/compiler/GHC/Tc/Gen/Sig.hs
index 42d5300d1e..850b0bb48a 100644
--- a/compiler/GHC/Tc/Gen/Sig.hs
+++ b/compiler/GHC/Tc/Gen/Sig.hs
@@ -26,8 +26,11 @@ module GHC.Tc.Gen.Sig(
 
 import GHC.Prelude
 
+import GHC.Driver.Session
+import GHC.Driver.Backend
+
 import GHC.Hs
-import GHC.Tc.Errors.Types ( LevityCheckProvenance(..) )
+
 import GHC.Tc.Gen.HsType
 import GHC.Tc.Types
 import GHC.Tc.Solver( pushLevelAndSolveEqualitiesX, reportUnsolvedEqualities )
@@ -41,26 +44,30 @@ import GHC.Tc.Utils.Unify( tcSkolemise, unifyType )
 import GHC.Tc.Utils.Instantiate( topInstantiate, tcInstTypeBndrs )
 import GHC.Tc.Utils.Env( tcLookupId )
 import GHC.Tc.Types.Evidence( HsWrapper, (<.>) )
+import GHC.Tc.Errors.Types ( LevityCheckProvenance(..) )
+
 import GHC.Core( hasSomeUnfolding )
 import GHC.Core.Type ( mkTyVarBinders )
 import GHC.Core.Multiplicity
 
-import GHC.Driver.Session
-import GHC.Driver.Backend
-import GHC.Driver.Ppr
 import GHC.Types.Var ( TyVar, Specificity(..), tyVarKind, binderVars )
 import GHC.Types.Id  ( Id, idName, idType, setInlinePragma
                      , mkLocalId, realIdUnfolding )
-import GHC.Builtin.Names( mkUnboundName )
 import GHC.Types.Basic
-import GHC.Unit.Module( getModule )
 import GHC.Types.Name
 import GHC.Types.Name.Env
-import GHC.Utils.Outputable
-import GHC.Utils.Panic
 import GHC.Types.SrcLoc
+
+import GHC.Builtin.Names( mkUnboundName )
+import GHC.Unit.Module( getModule )
+
 import GHC.Utils.Misc as Utils ( singleton )
+import GHC.Utils.Outputable
+import GHC.Utils.Panic
+import GHC.Utils.Trace
+
 import GHC.Data.Maybe( orElse )
+
 import Data.Maybe( mapMaybe )
 import Control.Monad( unless )
 
diff --git a/compiler/GHC/Tc/Types/Origin.hs b/compiler/GHC/Tc/Types/Origin.hs
index cb15e962f6..371093a183 100644
--- a/compiler/GHC/Tc/Types/Origin.hs
+++ b/compiler/GHC/Tc/Types/Origin.hs
@@ -46,7 +46,7 @@ import GHC.Data.FastString
 
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
-import GHC.Driver.Ppr
+import GHC.Utils.Trace
 
 {- *********************************************************************
 *                                                                      *
diff --git a/compiler/GHC/Tc/Utils/TcMType.hs b/compiler/GHC/Tc/Utils/TcMType.hs
index 3172a6791a..1a8be64e29 100644
--- a/compiler/GHC/Tc/Utils/TcMType.hs
+++ b/compiler/GHC/Tc/Utils/TcMType.hs
@@ -96,46 +96,48 @@ module GHC.Tc.Utils.TcMType (
   ensureNotLevPoly, checkForLevPoly, checkForLevPolyX,
   ) where
 
--- friends:
 import GHC.Prelude
 
-import {-# SOURCE #-}   GHC.Tc.Utils.Unify( unifyType {- , unifyKind -} )
+import GHC.Driver.Session
+import qualified GHC.LanguageExtensions as LangExt
+
+import GHC.Tc.Types.Origin
+import GHC.Tc.Utils.Monad        -- TcType, amongst others
+import GHC.Tc.Types.Constraint
+import GHC.Tc.Types.Evidence
+import {-# SOURCE #-} GHC.Tc.Utils.Unify( unifyType {- , unifyKind -} )
+import GHC.Tc.Utils.TcType
+import GHC.Tc.Errors.Types
 
 import GHC.Core.TyCo.Rep
 import GHC.Core.TyCo.Ppr
-import GHC.Tc.Utils.TcType
 import GHC.Core.Type
 import GHC.Core.TyCon
 import GHC.Core.Coercion
 import GHC.Core.Class
-import GHC.Types.Var
 import GHC.Core.Predicate
-import GHC.Tc.Errors.Types
-import GHC.Tc.Types.Origin
 
--- others:
-import GHC.Tc.Utils.Monad        -- TcType, amongst others
-import GHC.Tc.Types.Constraint
-import GHC.Tc.Types.Evidence
+import GHC.Types.Var
 import GHC.Types.Id as Id
 import GHC.Types.Name
 import GHC.Types.Var.Set
-import GHC.Builtin.Types
 import GHC.Types.Var.Env
 import GHC.Types.Name.Env
+import GHC.Types.Unique.Set
+import GHC.Types.Basic ( TypeOrKind(..) )
+
+import GHC.Builtin.Types
+
+import GHC.Data.FastString
+import GHC.Data.Bag
+import GHC.Data.Pair
+
 import GHC.Utils.Misc
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
 import GHC.Utils.Constants (debugIsOn)
-import GHC.Data.FastString
-import GHC.Data.Bag
-import GHC.Data.Pair
-import GHC.Types.Unique.Set
-import GHC.Driver.Session
-import GHC.Driver.Ppr
-import qualified GHC.LanguageExtensions as LangExt
-import GHC.Types.Basic ( TypeOrKind(..) )
+import GHC.Utils.Trace
 
 import Control.Monad
 import GHC.Data.Maybe
diff --git a/compiler/GHC/Types/Id.hs b/compiler/GHC/Types/Id.hs
index 7c78c1928b..8ac7fc214b 100644
--- a/compiler/GHC/Types/Id.hs
+++ b/compiler/GHC/Types/Id.hs
@@ -163,8 +163,7 @@ import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
 import GHC.Utils.GlobalVars
-
-import GHC.Driver.Ppr
+import GHC.Utils.Trace
 
 -- infixl so you can say (id `set` a `set` b)
 infixl  1 `setIdUnfolding`,
diff --git a/compiler/GHC/Types/TyThing/Ppr.hs b/compiler/GHC/Types/TyThing/Ppr.hs
index 2e8476c851..efe1a748b5 100644
--- a/compiler/GHC/Types/TyThing/Ppr.hs
+++ b/compiler/GHC/Types/TyThing/Ppr.hs
@@ -18,8 +18,6 @@ module GHC.Types.TyThing.Ppr (
 
 import GHC.Prelude
 
-import GHC.Driver.Ppr (warnPprTrace)
-
 import GHC.Types.TyThing ( TyThing(..), tyThingParent_maybe )
 import GHC.Types.Name
 
@@ -33,6 +31,7 @@ import GHC.Iface.Syntax ( ShowSub(..), ShowHowMuch(..), AltPpr(..)
 import GHC.Iface.Make ( tyThingToIfaceDecl )
 
 import GHC.Utils.Outputable
+import GHC.Utils.Trace
 
 -- -----------------------------------------------------------------------------
 -- Pretty-printing entities that we get from the GHC API
diff --git a/compiler/GHC/Utils/Error.hs b/compiler/GHC/Utils/Error.hs
index 9a1ea88aa7..93ab233788 100644
--- a/compiler/GHC/Utils/Error.hs
+++ b/compiler/GHC/Utils/Error.hs
@@ -64,7 +64,6 @@ module GHC.Utils.Error (
 import GHC.Prelude
 
 import GHC.Driver.Session
-import GHC.Driver.Ppr
 
 import GHC.Data.Bag
 import GHC.Utils.Exception
diff --git a/compiler/GHC/Utils/Logger.hs b/compiler/GHC/Utils/Logger.hs
index 77506682bd..e497b8c965 100644
--- a/compiler/GHC/Utils/Logger.hs
+++ b/compiler/GHC/Utils/Logger.hs
@@ -77,7 +77,6 @@ where
 
 import GHC.Prelude
 import GHC.Driver.Flags
-import GHC.Driver.Ppr
 import GHC.Types.Error
 import GHC.Types.SrcLoc
 
@@ -101,6 +100,7 @@ import System.IO
 import Control.Monad
 import Control.Concurrent.MVar
 import System.IO.Unsafe
+import Debug.Trace (trace)
 
 ---------------------------------------------------------------
 -- Log flags
@@ -528,7 +528,7 @@ defaultTraceAction :: TraceAction a
 defaultTraceAction logflags title doc x =
   if not (log_enable_debug logflags)
     then x
-    else trace (showSDocDump (log_default_dump_context logflags)
+    else trace (renderWithContext (log_default_dump_context logflags)
                              (sep [text title, nest 2 doc])) x
 
 
diff --git a/compiler/GHC/Utils/Misc.hs b/compiler/GHC/Utils/Misc.hs
index d19d78c876..181d6c91e7 100644
--- a/compiler/GHC/Utils/Misc.hs
+++ b/compiler/GHC/Utils/Misc.hs
@@ -42,8 +42,6 @@ module GHC.Utils.Misc (
         isSingleton, only, expectOnly, GHC.Utils.Misc.singleton,
         notNull, snocView,
 
-        isIn, isn'tIn,
-
         chunkList,
 
         changeLast,
@@ -122,10 +120,6 @@ module GHC.Utils.Misc (
         -- * Call stacks
         HasCallStack,
         HasDebugCallStack,
-
-        -- * Utils for flags
-        OverridingBool(..),
-        overrideWith,
     ) where
 
 import GHC.Prelude
@@ -160,11 +154,6 @@ import qualified Data.Set as Set
 
 import Data.Time
 
-#if defined(DEBUG)
-import {-# SOURCE #-} GHC.Utils.Outputable ( text )
-import {-# SOURCE #-} GHC.Driver.Ppr ( warnPprTrace )
-#endif
-
 infixr 9 `thenCmp`
 
 
@@ -524,34 +513,6 @@ expectOnly _   (a:_) = a
 #endif
 expectOnly msg _     = panic ("expectOnly: " ++ msg)
 
--- Debugging/specialising versions of \tr{elem} and \tr{notElem}
-
-# if !defined(DEBUG)
-isIn, isn'tIn :: Eq a => String -> a -> [a] -> Bool
-isIn    _msg x ys = x `elem` ys
-isn'tIn _msg x ys = x `notElem` ys
-
-# else /* DEBUG */
-isIn, isn'tIn :: (HasDebugCallStack, Eq a) => String -> a -> [a] -> Bool
-isIn msg x ys
-  = elem100 0 x ys
-  where
-    elem100 :: Eq a => Int -> a -> [a] -> Bool
-    elem100 _ _ [] = False
-    elem100 i x (y:ys)
-      | i > 100 = warnPprTrace True (text ("Over-long elem in " ++ msg)) (x `elem` (y:ys))
-      | otherwise = x == y || elem100 (i + 1) x ys
-
-isn'tIn msg x ys
-  = notElem100 0 x ys
-  where
-    notElem100 :: Eq a => Int -> a -> [a] -> Bool
-    notElem100 _ _ [] =  True
-    notElem100 i x (y:ys)
-      | i > 100 = warnPprTrace True (text ("Over-long notElem in " ++ msg)) (x `notElem` (y:ys))
-      | otherwise = x /= y && notElem100 (i + 1) x ys
-# endif /* DEBUG */
-
 
 -- | Split a list into chunks of /n/ elements
 chunkList :: Int -> [a] -> [[a]]
@@ -1486,14 +1447,3 @@ type HasDebugCallStack = HasCallStack
 #else
 type HasDebugCallStack = (() :: Constraint)
 #endif
-
-data OverridingBool
-  = Auto
-  | Always
-  | Never
-  deriving Show
-
-overrideWith :: Bool -> OverridingBool -> Bool
-overrideWith b Auto   = b
-overrideWith _ Always = True
-overrideWith _ Never  = False
diff --git a/compiler/GHC/Utils/Outputable.hs b/compiler/GHC/Utils/Outputable.hs
index 7d33007ead..7d0436f2f2 100644
--- a/compiler/GHC/Utils/Outputable.hs
+++ b/compiler/GHC/Utils/Outputable.hs
@@ -57,6 +57,7 @@ module GHC.Utils.Outputable (
         showSDocUnsafe,
         showPprUnsafe,
         renderWithContext,
+        pprDebugAndThen,
 
         pprInfixVar, pprPrefixVar,
         pprHsChar, pprHsString, pprHsBytes,
@@ -607,6 +608,13 @@ showPprUnsafe :: Outputable a => a -> String
 showPprUnsafe a = renderWithContext defaultSDocContext (ppr a)
 
 
+pprDebugAndThen :: SDocContext -> (String -> a) -> SDoc -> SDoc -> a
+pprDebugAndThen ctx cont heading pretty_msg
+ = cont (renderWithContext ctx doc)
+ where
+     doc = withPprStyle defaultDumpStyle (sep [heading, nest 2 pretty_msg])
+
+
 isEmpty :: SDocContext -> SDoc -> Bool
 isEmpty ctx sdoc = Pretty.isEmpty $ runSDoc sdoc (ctx {sdocPprDebug = True})
 
diff --git a/compiler/GHC/Utils/Panic.hs b/compiler/GHC/Utils/Panic.hs
index fb72886be7..497ea65003 100644
--- a/compiler/GHC/Utils/Panic.hs
+++ b/compiler/GHC/Utils/Panic.hs
@@ -29,7 +29,6 @@ module GHC.Utils.Panic
    , assertPprM
    , massertPpr
    , sorry
-   , trace
    , panicDoc
    , sorryDoc
    , pgmErrorDoc
@@ -60,7 +59,6 @@ import Control.Monad.IO.Class
 import qualified Control.Monad.Catch as MC
 import Control.Concurrent
 import Data.Typeable      ( cast )
-import Debug.Trace        ( trace )
 import System.IO.Unsafe
 
 #if !defined(mingw32_HOST_OS)
diff --git a/compiler/GHC/Utils/Ppr/Colour.hs b/compiler/GHC/Utils/Ppr/Colour.hs
index 7283edd182..92044d96e4 100644
--- a/compiler/GHC/Utils/Ppr/Colour.hs
+++ b/compiler/GHC/Utils/Ppr/Colour.hs
@@ -2,7 +2,7 @@ module GHC.Utils.Ppr.Colour where
 import GHC.Prelude
 
 import Data.Maybe (fromMaybe)
-import GHC.Utils.Misc (OverridingBool(..), split)
+import GHC.Data.Bool
 import Data.Semigroup as Semi
 
 -- | A colour\/style for use with 'coloured'.
@@ -93,6 +93,11 @@ parseScheme input    (b, cs) =
     }
   )
   where
+    split :: Char -> String -> [String]
+    split c s = case break (==c) s of
+        (chunk,[])     -> [chunk]
+        (chunk,_:rest) -> chunk : split c rest
+
     table = do
       w <- split ':' input
       let (k, v') = break (== '=') w
diff --git a/compiler/GHC/Utils/Trace.hs b/compiler/GHC/Utils/Trace.hs
new file mode 100644
index 0000000000..ac29cd6fd8
--- /dev/null
+++ b/compiler/GHC/Utils/Trace.hs
@@ -0,0 +1,77 @@
+-- | Tracing utilities
+module GHC.Utils.Trace
+  ( pprTrace
+  , pprTraceM
+  , pprTraceDebug
+  , pprTraceIt
+  , pprSTrace
+  , pprTraceException
+  , warnPprTrace
+  , trace
+  )
+where
+
+import GHC.Prelude
+import GHC.Utils.Outputable
+import GHC.Utils.Exception
+import GHC.Utils.Panic
+import GHC.Utils.GlobalVars
+import GHC.Utils.Constants
+import GHC.Stack
+
+import Debug.Trace (trace)
+import Control.Monad.IO.Class
+
+-- | If debug output is on, show some 'SDoc' on the screen
+pprTrace :: String -> SDoc -> a -> a
+pprTrace str doc x
+  | unsafeHasNoDebugOutput = x
+  | otherwise              = pprDebugAndThen defaultSDocContext trace (text str) doc x
+
+pprTraceM :: Applicative f => String -> SDoc -> f ()
+pprTraceM str doc = pprTrace str doc (pure ())
+
+pprTraceDebug :: String -> SDoc -> a -> a
+pprTraceDebug str doc x
+   | debugIsOn && unsafeHasPprDebug = pprTrace str doc x
+   | otherwise                      = x
+
+-- | @pprTraceWith desc f x@ is equivalent to @pprTrace desc (f x) x@.
+-- This allows you to print details from the returned value as well as from
+-- ambient variables.
+pprTraceWith :: String -> (a -> SDoc) -> a -> a
+pprTraceWith desc f x = pprTrace desc (f x) x
+
+-- | @pprTraceIt desc x@ is equivalent to @pprTrace desc (ppr x) x@
+pprTraceIt :: Outputable a => String -> a -> a
+pprTraceIt desc x = pprTraceWith desc ppr x
+
+-- | @pprTraceException desc x action@ runs action, printing a message
+-- if it throws an exception.
+pprTraceException :: ExceptionMonad m => String -> SDoc -> m a -> m a
+pprTraceException heading doc =
+    handleGhcException $ \exc -> liftIO $ do
+        putStrLn $ renderWithContext defaultSDocContext
+                 $ withPprStyle defaultDumpStyle
+                 $ sep [text heading, nest 2 doc]
+        throwGhcExceptionIO exc
+
+-- | If debug output is on, show some 'SDoc' on the screen along
+-- with a call stack when available.
+pprSTrace :: HasCallStack => SDoc -> a -> a
+pprSTrace doc = pprTrace "" (doc $$ traceCallStackDoc)
+
+-- | Just warn about an assertion failure, recording the given file and line number.
+warnPprTrace :: HasCallStack => Bool -> SDoc -> a -> a
+warnPprTrace _     _    x | not debugIsOn     = x
+warnPprTrace _     _msg x | unsafeHasNoDebugOutput = x
+warnPprTrace False _msg x = x
+warnPprTrace True   msg x
+  = pprDebugAndThen defaultSDocContext trace (text "WARNING:")
+                    (msg $$ withFrozenCallStack traceCallStackDoc )
+                    x
+
+traceCallStackDoc :: HasCallStack => SDoc
+traceCallStackDoc =
+    hang (text "Call stack:")
+       4 (vcat $ map text $ lines (prettyCallStack callStack))
diff --git a/compiler/ghc.cabal.in b/compiler/ghc.cabal.in
index b896cbbfb8..fe1beacc8b 100644
--- a/compiler/ghc.cabal.in
+++ b/compiler/ghc.cabal.in
@@ -361,6 +361,7 @@ Library
         GHC.Core.Utils
         GHC.Data.Bag
         GHC.Data.Bitmap
+        GHC.Data.Bool
         GHC.Data.BooleanFormula
         GHC.Data.EnumSet
         GHC.Data.FastMutInt
@@ -742,6 +743,7 @@ Library
         GHC.Utils.Ppr
         GHC.Utils.Ppr.Colour
         GHC.Utils.TmpFs
+        GHC.Utils.Trace
 
         Language.Haskell.Syntax
         Language.Haskell.Syntax.Binds
-- 
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