Test for #5237

Test that the rewrite rules fire. Check allocation figures to not depend
on the order of rule firings.

1 files changed, 15 insertions, 0 deletions

diff --git a/testsuite/tests/perf/should_run/T5237.hs b/testsuite/tests/perf/should_run/T5237.hs
new file mode 100644
index 0000000000..6a12f5ecea
--- /dev/null
+++ b/testsuite/tests/perf/should_run/T5237.hs
@@ -0,0 +1,15 @@
+{-# LANGUAGE BangPatterns #-}
+module Main (main) where
+
+-- Test that the rewrite rules for small exponents fire (#5237).
+-- If they don't fire, this will allocate much.
+
+fun :: Double -> Double
+fun x = go 0 1.0
+  where
+    go !acc z
+      | x < z   = acc
+      | otherwise = go (acc + 1/z^4) (z+1.0)
+
+main :: IO ()
+main = print (fun 1e7)