[project @ 1996-01-22 18:37:39 by partain]

[ghc-hetmet.git] / ghc / compiler / main / CmdLineOpts.lhs

diff --git a/ghc/compiler/main/CmdLineOpts.lhs b/ghc/compiler/main/CmdLineOpts.lhs
index 210251c..4588a88 100644 (file)
--- a/ghc/compiler/main/CmdLineOpts.lhs
+++ b/ghc/compiler/main/CmdLineOpts.lhs
@@ -276,6 +276,17 @@ data SimplifierSwitch
   | SimplNoLetFromCase     -- used when turning off floating entirely
   | SimplNoLetFromApp      -- (for experimentation only) WDP 95/10
   | SimplNoLetFromStrictLet
+
+  | SimplDontFoldBackAppend
+                       -- we fold `foldr (:)' back into flip (++),
+                       -- but we *don't* want to do it when compiling
+                       -- List.hs, otherwise 
+                       -- xs ++ ys = foldr (:) ys xs
+                       -- {- via our loopback -}
+                       -- xs ++ ys = xs ++ ys
+                       -- Oops!
+                       -- So only use this flag inside List.hs
+                       -- (Sigh, what a HACK, Andy.  WDP 96/01)
 {-
   | Extra__SimplFlag1
   | Extra__SimplFlag2
@@ -609,6 +620,7 @@ classifyOpts opts
          "-fdo-eta-reduction" -> GLOBAL_SIMPL_SW(SimplDoEtaReduction)
          "-fdo-lambda-eta-expansion" -> GLOBAL_SIMPL_SW(SimplDoLambdaEtaExpansion)
          "-fdo-foldr-build"  -> GLOBAL_SIMPL_SW(SimplDoFoldrBuild)
+         "-fdo-not-fold-back-append"  -> GLOBAL_SIMPL_SW(SimplDontFoldBackAppend)
          "-fdo-new-occur-anal"  -> GLOBAL_SIMPL_SW(SimplDoNewOccurAnal)
          "-fdo-arity-expand"  -> GLOBAL_SIMPL_SW(SimplDoArityExpand)
          "-fdo-inline-foldr-build"  -> GLOBAL_SIMPL_SW(SimplDoInlineFoldrBuild)
@@ -790,6 +802,7 @@ tagOf_SimplSwitch KeepUnusedBindings                = ILIT(25)
 tagOf_SimplSwitch SimplNoLetFromCase           = ILIT(26)
 tagOf_SimplSwitch SimplNoLetFromApp            = ILIT(27)
 tagOf_SimplSwitch SimplNoLetFromStrictLet      = ILIT(28)
+tagOf_SimplSwitch SimplDontFoldBackAppend       = ILIT(29)
 -- If you add anything here, be sure to change lAST_SIMPL_SWITCH_TAG, too!
 
 {-
@@ -805,7 +818,7 @@ tagOf_SimplSwitch Extra__SimplFlag8         = ILIT(32)
 tagOf_SimplSwitch _ = case (panic "tagOf_SimplSwitch") of -- BUG avoidance
                        s -> tagOf_SimplSwitch s
 
-lAST_SIMPL_SWITCH_TAG = IBOX(tagOf_SimplSwitch SimplNoLetFromStrictLet)
+lAST_SIMPL_SWITCH_TAG = IBOX(tagOf_SimplSwitch SimplDontFoldBackAppend)
 \end{code}
 
 %************************************************************************