Add compiler perf test for #14565wip/sjakobi/T14565-test

Closes #14565.

2 files changed, 41 insertions, 0 deletions

diff --git a/testsuite/tests/perf/compiler/T14565.hs b/testsuite/tests/perf/compiler/T14565.hs
new file mode 100644
index 0000000000..d7998e082e
--- /dev/null
+++ b/testsuite/tests/perf/compiler/T14565.hs
@@ -0,0 +1,33 @@
+-- GHC-8.2.2 gets stuck in SpecConstr while compiling this module
+module T14565 where
+
+import           Control.Monad (forM_, when)
+import qualified Data.Vector.Unboxed as V
+import qualified Data.Vector.Unboxed.Mutable as VM
+
+data Dimensions = Dimensions Int Int Int Int
+  deriving (Show)
+
+-- Changing this to `toIdx = const 0` removes the issue.
+toIdx :: Dimensions -> Int
+toIdx (Dimensions _ _ _ _) = 0
+
+data Grid = Grid Dimensions (V.Vector Double)
+  deriving (Show)
+
+pointsGrid
+  :: Dimensions
+  -> Grid
+  -> Grid
+pointsGrid scs (Grid _ gv) = Grid scs $ V.create $ do
+  let v0 = V.fromList [(0::Int)]
+
+  v <- VM.replicate 100 0
+
+  -- Removing one of `V.forM_ v0` branches seems to remove the issue.
+  V.forM_ v0 $ \_ ->
+    V.forM_ v0 $ \_ ->
+      V.forM_ v0 $ \_ ->
+        V.forM_ v0 $ \_ -> VM.unsafeModify v (+ 0) (toIdx scs)
+
+  pure v
diff --git a/testsuite/tests/perf/compiler/all.T b/testsuite/tests/perf/compiler/all.T
index 937858c2a7..eee481dee5 100644
--- a/testsuite/tests/perf/compiler/all.T
+++ b/testsuite/tests/perf/compiler/all.T
@@ -452,3 +452,11 @@ test ('T9198',
       [ collect_compiler_stats('bytes allocated',2) ],
       compile,
       [''])
+
+test('T14565',
+     [ reqlib('vector'),
+       only_ways(['optasm']),
+       collect_compiler_stats('bytes allocated',2),
+     ],
+     compile,
+     ['-O2 -fspec-constr'])