Retain INLINE pragma information during indirection-shorting

During indirection-shorting, we were dropping the InlinePragInfo,
although were were carefully retaining strictness info etc.
I think this is a long-standing bug.

diff --git a/compiler/simplCore/SimplCore.lhs b/compiler/simplCore/SimplCore.lhs
index a386a3d..24c8603 100644 (file)
--- a/compiler/simplCore/SimplCore.lhs
+++ b/compiler/simplCore/SimplCore.lhs
@@ -23,6 +23,7 @@ import PprCore                ( pprCoreBindings, pprCoreExpr, pprRules )
 import OccurAnal       ( occurAnalysePgm, occurAnalyseExpr )
 import IdInfo          ( setNewStrictnessInfo, newStrictnessInfo, 
                          setWorkerInfo, workerInfo,
+                         setInlinePragInfo, inlinePragInfo,
                          setSpecInfo, specInfo, specInfoRules )
 import CoreUtils       ( coreBindsSize )
 import Simplify                ( simplTopBinds, simplExpr )
@@ -468,6 +469,9 @@ simplifyPgm mode switches hsc_env us imp_rule_base guts
                -- because indirection-shorting uses the export flag on *occurrences*
                -- and that isn't guaranteed to be ok until after the first run propagates
                -- stuff from the binding site to its occurrences
+               --
+               -- ToDo: alas, this means that indirection-shorting does not happen at all
+               --       if the simplifier does nothing (not common, I know, but unsavoury)
           let { binds'' = _scc_ "ZapInd" shortOutIndirections binds' } ;
 
                -- Dump the result of this iteration
@@ -600,8 +604,8 @@ type IndEnv = IdEnv Id              -- Maps local_id -> exported_id
 shortOutIndirections :: [CoreBind] -> [CoreBind]
 shortOutIndirections binds
   | isEmptyVarEnv ind_env = binds
-  | no_need_to_flatten   = binds'
-  | otherwise            = [Rec (flattenBinds binds')] -- See Note [Rules and indirect-zapping]
+  | no_need_to_flatten   = binds'                      -- See Note [Rules and indirect-zapping]
+  | otherwise            = [Rec (flattenBinds binds')] -- for this no_need_to_flatten stuff
   where
     ind_env           = makeIndEnv binds
     exp_ids           = varSetElems ind_env    -- These exported Ids are the subjects
@@ -663,12 +667,19 @@ shortMeOut ind_env exported_id local_id
 
 -----------------
 transferIdInfo :: Id -> Id -> Id
+-- If we have
+--     lcl_id = e; exp_id = lcl_id
+-- and lcl_id has useful IdInfo, we don't want to discard it by going
+--     gbl_id = e; lcl_id = gbl_id
+-- Instead, transfer IdInfo from lcl_id to exp_id
+-- Overwriting, rather than merging, seems to work ok.
 transferIdInfo exported_id local_id
   = modifyIdInfo transfer exported_id
   where
     local_info = idInfo local_id
     transfer exp_info = exp_info `setNewStrictnessInfo` newStrictnessInfo local_info
                                 `setWorkerInfo`        workerInfo local_info
+                                `setInlinePragInfo`    inlinePragInfo local_info
                                 `setSpecInfo`          addSpecInfo (specInfo exp_info)
                                                                    (specInfo local_info)
 \end{code}