Test case for #T7619

(artificial test cases are so nice: 90.7% improvement!)

testsuite/tests/perf/should_run/T7619.hs

+{-# LANGUAGE TypeFamilies #-}
+module Main where
+data family Foo a
+
+data instance Foo Int = FooInt Int Int
+
+foo :: Foo Int -> Int
+foo (FooInt a 0) = 0
+foo (FooInt a b) = foo (FooInt a (b-1))
+
+main :: IO ()
+main = foo (FooInt 0 10000) `seq` return ()

testsuite/tests/perf/should_run/all.T

@@ -314,3 +314,11 @@ test('T4267',
      compile_and_run,
      ['-O'])
 
+test('T7619',
+     [stats_num_field('bytes allocated',
+                      [ (wordsize(64), 40992, 10)]),
+                      # previously, it was >400000 bytes
+      only_ways(['normal'])],
+     compile_and_run,
+     ['-O'])
+