Add testcase for #4267

testsuite/tests/perf/should_run/T4267.hs

+data Tree a = Leaf | Node a !(Tree a) !(Tree a)
+
+{-
+
+This should produce a walker with unboxed integers.
+
+Bad:
+
+Rec {
+go_r1us
+  :: GHC.Types.Int -> Main.Tree GHC.Types.Int -> GHC.Types.Int
+[GblId, Arity=2, Caf=NoCafRefs, Str=DmdType SS]
+go_r1us =
+  \ (z_aeS :: GHC.Types.Int) (ds_dmD :: Main.Tree GHC.Types.Int) ->
+    case ds_dmD of _ {
+      Main.Leaf -> z_aeS;
+      Main.Node a1_aeU l_aeV r_aeW ->
+        case go_r1us z_aeS l_aeV of _ { GHC.Types.I# ipv_snn ->
+        case a1_aeU of _ { GHC.Types.I# y_anh ->
+        go_r1us (GHC.Types.I# (GHC.Prim.+# ipv_snn y_anh)) r_aeW
+        }
+        }
+    }
+end Rec }
+
+
+Good:
+
+Rec {
+$wgo_r2fS
+  :: GHC.Prim.Int# -> Main.Tree GHC.Types.Int -> GHC.Prim.Int#
+[GblId, Arity=2, Caf=NoCafRefs, Str=DmdType <L,U><S,1*U>]
+$wgo_r2fS =
+  \ (ww_s2eZ :: GHC.Prim.Int#) (w_s2eW :: Main.Tree GHC.Types.Int) ->
+    case w_s2eW of _ [Occ=Dead] {
+      Main.Leaf -> ww_s2eZ;
+      Main.Node a1_aqv l_aqw r_aqx ->
+        case $wgo_r2fS ww_s2eZ l_aqw of ww1_s2f3 { __DEFAULT ->
+        case a1_aqv of _ [Occ=Dead] { GHC.Types.I# y_aTz ->
+        $wgo_r2fS (GHC.Prim.+# ww1_s2f3 y_aTz) r_aqx
+        }
+        }
+    }
+end Rec }
+
+-}
+
+-- Strict, pre-order fold.
+fold' :: (a -> b -> a) -> a -> Tree b -> a
+fold' f = go
+  where
+    go z Leaf = z
+    go z (Node a l r) = let z'  = go z l
+                            z'' = f z' a
+                        in z' `seq` z'' `seq` go z'' r
+
+
+sumTree :: Int -> Tree Int -> Int
+sumTree = fold' (+)
+
+
+tree = Node 0 (Node 0 Leaf Leaf) (Node 0 Leaf Leaf)
+
+main = sum [sumTree n tree | n <- [0..1000]] `seq` return ()

testsuite/tests/perf/should_run/all.T

@@ -306,3 +306,11 @@ test('T5949',
      compile_and_run,
      ['-O'])
 
+test('T4267',
+     [stats_num_field('bytes allocated',
+                      [ (wordsize(64), 130000, 10)]),
+                      # previously, it was >170000 bytes
+      only_ways(['normal'])],
+     compile_and_run,
+     ['-O'])
+