[commit: ghc] master: Some improvements on CoreToDos passed to plugins (bcd55a9)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/bcd55a94f234f5efa4bb4fd24429dafc79d93106/ghc

>---------------------------------------------------------------

commit bcd55a94f234f5efa4bb4fd24429dafc79d93106
Author: Ömer Sinan Ağacan <omeragacan at gmail.com>
Date:   Sun Nov 29 22:49:46 2015 +0100

    Some improvements on CoreToDos passed to plugins
    
    This patch does two improvements:
    
    - We now show ToDos in `CoreDoPasses`. This is pretty important,
      otherwise `CoreDoPasses` makes debugging impossible in some cases.
    
    - Before running ToDos we run a cleanup pass on ToDos to remove
      `CoreDoNothing`s and flatten `CoreDoPasses`. This removes a lot of
      noise from `[CoreToDo]` argument passed to plugins.
    
    Reviewers: simonpj, bgamari, austin
    
    Reviewed By: bgamari, austin
    
    Subscribers: thomie
    
    Differential Revision: https://phabricator.haskell.org/D1548


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bcd55a94f234f5efa4bb4fd24429dafc79d93106
 compiler/simplCore/CoreMonad.hs | 2 +-
 compiler/simplCore/SimplCore.hs | 9 ++++++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/compiler/simplCore/CoreMonad.hs b/compiler/simplCore/CoreMonad.hs
index ce5286d..fa72834 100644
--- a/compiler/simplCore/CoreMonad.hs
+++ b/compiler/simplCore/CoreMonad.hs
@@ -169,7 +169,7 @@ instance Outputable CoreToDo where
   ppr CoreDoPrintCore          = ptext (sLit "Print core")
   ppr (CoreDoRuleCheck {})     = ptext (sLit "Rule check")
   ppr CoreDoNothing            = ptext (sLit "CoreDoNothing")
-  ppr (CoreDoPasses {})        = ptext (sLit "CoreDoPasses")
+  ppr (CoreDoPasses passes)    = ptext (sLit "CoreDoPasses") <+> ppr passes
 
 pprPassDetails :: CoreToDo -> SDoc
 pprPassDetails (CoreDoSimplify n md) = vcat [ ptext (sLit "Max iterations =") <+> int n
diff --git a/compiler/simplCore/SimplCore.hs b/compiler/simplCore/SimplCore.hs
index 9207cf4..8670e30 100644
--- a/compiler/simplCore/SimplCore.hs
+++ b/compiler/simplCore/SimplCore.hs
@@ -109,7 +109,7 @@ core2core hsc_env guts@(ModGuts { mg_module  = mod
 
 getCoreToDo :: DynFlags -> [CoreToDo]
 getCoreToDo dflags
-  = core_todo
+  = flatten_todos core_todo
   where
     opt_level     = optLevel           dflags
     phases        = simplPhases        dflags
@@ -322,6 +322,13 @@ getCoreToDo dflags
         maybe_rule_check (Phase 0)
      ]
 
+    -- Remove 'CoreDoNothing' and flatten 'CoreDoPasses' for clarity.
+    flatten_todos [] = []
+    flatten_todos (CoreDoNothing : rest) = flatten_todos rest
+    flatten_todos (CoreDoPasses passes : rest) =
+      flatten_todos passes ++ flatten_todos rest
+    flatten_todos (todo : rest) = todo : flatten_todos rest
+
 -- Loading plugins
 
 addPluginPasses :: [CoreToDo] -> CoreM [CoreToDo]