testsuite: Add test for #20142

2 files changed, 31 insertions, 0 deletions

diff --git a/testsuite/tests/cmm/opt/T20142.hs b/testsuite/tests/cmm/opt/T20142.hs
new file mode 100644
index 0000000000..c729265009
--- /dev/null
+++ b/testsuite/tests/cmm/opt/T20142.hs
@@ -0,0 +1,30 @@
+{-# LANGUAGE BangPatterns, CPP, MagicHash, RankNTypes, ScopedTypeVariables, UnboxedTuples #-}
+{-# OPTIONS_GHC -O2 -dcmm-lint #-}
+
+module Data.Text.Lazy.Builder.Int ( hexadecimal) where
+
+import GHC.Exts
+import Data.Int (Int8)
+import Prelude
+
+type Builder = [Char]
+
+singleton :: a -> [a]
+singleton x = [x]
+
+hexadecimal :: Int8 -> Builder
+hexadecimal i = go i
+  where
+    go n | n < 16    = hexDigit n
+         | otherwise = go (n `quot` 16) <> hexDigit (n `rem` 16)
+{-# NOINLINE[0] hexadecimal #-}
+
+hexDigit :: Integral a => a -> Builder
+hexDigit n
+    | n <= 9    = singleton $! i2d (fromIntegral n)
+    | otherwise = singleton $! toEnum (fromIntegral n + 87)
+{-# INLINE hexDigit #-}
+
+{-# INLINE i2d #-}
+i2d :: Int -> Char
+i2d (I# i#) = C# (chr# (ord# '0'# +# i#))
diff --git a/testsuite/tests/cmm/opt/all.T b/testsuite/tests/cmm/opt/all.T
index da7e95d5c4..0e4fc9abf2 100644
--- a/testsuite/tests/cmm/opt/all.T
+++ b/testsuite/tests/cmm/opt/all.T
@@ -2,3 +2,4 @@
 # to the same target.
 test('T15188', normal, makefile_test, [])
 test('T18141', normal, compile, [''])
+test('T20142', normal, compile, [''])