Add a test for plusWord2#, addIntC#, subIntC#

3 files changed, 91 insertions, 0 deletions

diff --git a/testsuite/tests/numeric/should_run/CarryOverflow.hs b/testsuite/tests/numeric/should_run/CarryOverflow.hs
new file mode 100644
index 0000000000..f83c1cf15c
--- /dev/null
+++ b/testsuite/tests/numeric/should_run/CarryOverflow.hs
@@ -0,0 +1,89 @@
+{-# LANGUAGE MagicHash, UnboxedTuples #-}
+
+import GHC.Prim
+import GHC.Word
+import GHC.Exts
+
+import Control.Monad
+import Data.Bits
+import Data.List
+import System.Exit
+
+allEqual :: Eq a => [a] -> Bool
+allEqual [] = error "allEqual: nothing to compare"
+allEqual (x:xs) = all (== x) xs
+
+testWords :: [Word]
+testWords = map head . group . sort $
+            concatMap (\w -> [w - 1, w, w + 1]) $
+            concatMap (\w -> [w, maxBound - w]) $
+            trailingOnes ++ randoms
+  where trailingOnes = takeWhile (/= 0) $ iterate (`div` 2) $ maxBound
+        -- What would a Haskell program be without some Fibonacci numbers?
+        randoms = take 40 $ drop 100 fibs
+        fibs = 0 : 1 : zipWith (+) fibs (tail fibs)
+
+
+wordSizeInBits :: Int
+wordSizeInBits = length $ takeWhile (/= 0) $ iterate (`div` 2) (maxBound :: Word)
+
+
+-- plusWord2# (Word# carry)
+
+ways_plusWord2# :: [Word -> Word -> Bool]
+ways_plusWord2# = [ltTest, integerTest, primopTest]
+  where ltTest x y =
+          let r = x + y in r < x
+        integerTest x y =
+          let r = fromIntegral x + fromIntegral y :: Integer
+          in r > fromIntegral (maxBound :: Word)
+        primopTest (W# x) (W# y) = case plusWord2# x y of
+          (# 0##, _ #) -> False
+          (# 1##, _ #) -> True
+          _            -> error "unexpected result from plusWord2#"
+
+-- addIntC# (Int# addition overflow)
+
+ways_addIntC# :: [Int -> Int -> Bool]
+ways_addIntC# = [ltTest, integerTest, highBitTest, primopTest]
+  where ltTest x y =
+          let r = x + y in (y > 0 && r < x) || (y < 0 && r > x)
+        integerTest x y =
+          let r = fromIntegral x + fromIntegral y :: Integer
+          in r < fromIntegral (minBound :: Int) || r > fromIntegral (maxBound :: Int)
+        highBitTest x y =
+          let r = x + y in testBit ((x `xor` r) .&. (y `xor` r)) (wordSizeInBits - 1)
+        primopTest (I# x) (I# y) = case addIntC# x y of
+          (# _, 0# #) -> False
+          _ -> True
+
+-- subIntC# (Int# subtraction overflow)
+
+ways_subIntC# :: [Int -> Int -> Bool]
+ways_subIntC# = [ltTest, integerTest, highBitTest, primopTest]
+  where ltTest x y =
+          let r = x - y in (y > 0 && r > x) || (y < 0 && r < x)
+        integerTest x y =
+          let r = fromIntegral x - fromIntegral y :: Integer
+          in r < fromIntegral (minBound :: Int) || r > fromIntegral (maxBound :: Int)
+        highBitTest x y =
+          let r = x - y in testBit ((x `xor` r) .&. complement (y `xor` r)) (wordSizeInBits - 1)
+        primopTest (I# x) (I# y) = case subIntC# x y of
+          (# _, 0# #) -> False
+          _ -> True
+
+runTest :: Show a => String -> [a -> a -> Bool] -> a -> a -> IO ()
+runTest label ways x y = do
+  let results = map (\f -> f x y) ways
+  unless (allEqual results) $ do
+    putStrLn $ "Failed (" ++ label ++ "): " ++ show (x,y) ++ " " ++ show results
+    exitWith (ExitFailure 1)
+
+main :: IO ()
+main = do
+  forM_ testWords $ \x ->
+    forM_ testWords $ \y -> do
+      runTest "ways_plusWord2#" ways_plusWord2# x y
+      runTest "ways_addIntC#" ways_addIntC# (fromIntegral x) (fromIntegral y)
+      runTest "ways_subIntC#" ways_subIntC# (fromIntegral x) (fromIntegral y)
+  putStrLn "Passed"
diff --git a/testsuite/tests/numeric/should_run/CarryOverflow.stdout b/testsuite/tests/numeric/should_run/CarryOverflow.stdout
new file mode 100644
index 0000000000..863339fb8c
--- /dev/null
+++ b/testsuite/tests/numeric/should_run/CarryOverflow.stdout
@@ -0,0 +1 @@
+Passed
diff --git a/testsuite/tests/numeric/should_run/all.T b/testsuite/tests/numeric/should_run/all.T
index 3953fe6339..72c8e6a74a 100644
--- a/testsuite/tests/numeric/should_run/all.T
+++ b/testsuite/tests/numeric/should_run/all.T
@@ -62,3 +62,4 @@ test('T7014',
 test('T7233', normal, compile_and_run, [''])
 test('NumDecimals', normal, compile_and_run, [''])
 test('T8726', normal, compile_and_run, [''])
+test('CarryOverflow', omit_ways(['ghci']), compile_and_run, [''])