From 8fac4b9333ef3607e75b4520d847054316cb8c2d Mon Sep 17 00:00:00 2001
From: Ben Gamari <ben@smart-cactus.org>
Date: Fri, 4 Dec 2020 14:17:56 -0500
Subject: [PATCH] testsuite: Add a test for #18923

---
 testsuite/tests/perf/compiler/T18923.hs | 16 ++++++++++++++++
 testsuite/tests/perf/compiler/all.T     |  4 ++++
 2 files changed, 20 insertions(+)
 create mode 100644 testsuite/tests/perf/compiler/T18923.hs

diff --git a/testsuite/tests/perf/compiler/T18923.hs b/testsuite/tests/perf/compiler/T18923.hs
new file mode 100644
index 000000000000..4127469283b1
--- /dev/null
+++ b/testsuite/tests/perf/compiler/T18923.hs
@@ -0,0 +1,16 @@
+module T18923 (mergeRec, Rec) where
+
+mayMerge :: Maybe b -> Maybe b -> Maybe b
+mayMerge Nothing  y        = y
+mayMerge x        Nothing  = x
+mayMerge (Just x) (Just y) = Just y
+
+data Rec = Rec { v0,v1,v2,v3,v4,v5,v6,v7 :: !(Maybe Bool) }
+
+mergeRec :: Rec -> Rec -> Rec
+mergeRec
+  (Rec a0 a1 a2 a3 a4 a5 a6 a7)
+  (Rec b0 b1 b2 b3 b4 b5 b6 b7) =
+    Rec (mayMerge a0 b0) (mayMerge a1 b1) (mayMerge a2 b2) (mayMerge a3 b3)
+        (mayMerge a4 b4) (mayMerge a5 b5) (mayMerge a6 b6) (mayMerge a7 b7)
+
diff --git a/testsuite/tests/perf/compiler/all.T b/testsuite/tests/perf/compiler/all.T
index 46222c723a03..1eace3ac0a34 100644
--- a/testsuite/tests/perf/compiler/all.T
+++ b/testsuite/tests/perf/compiler/all.T
@@ -434,3 +434,7 @@ test ('T18223',
       ],
       compile,
       ['-v0 -O'])
+test ('T18923',
+      [ collect_compiler_stats('bytes allocated',2) ],
+      compile,
+      ['-v0 -O'])
-- 
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