diff options
Diffstat (limited to 'testsuite/tests/simplCore/should_compile/OpaqueNoRebox2.hs')
| -rw-r--r-- | testsuite/tests/simplCore/should_compile/OpaqueNoRebox2.hs | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/testsuite/tests/simplCore/should_compile/OpaqueNoRebox2.hs b/testsuite/tests/simplCore/should_compile/OpaqueNoRebox2.hs new file mode 100644 index 0000000000..1384eea1d6 --- /dev/null +++ b/testsuite/tests/simplCore/should_compile/OpaqueNoRebox2.hs @@ -0,0 +1,23 @@ +module OpaqueNoRebox2 where + +{-# OPAQUE f #-} +f :: Int -> Int -> (Int, Int) +f x y = (x,y) + +-- No W/W happens for f because it is OPAQUE, and by design its CPR +-- information is stripped, which is good! +-- +-- If we hadn't stripped the CPR information, we would make a worker/wrapper +-- for g that would rebox the result of 'g': +-- +-- $wg :: Bool -> Int -> (# Int, Int #) +-- $wg True a = case f 2 a of (x, y) -> (# x, y #) +-- $wg False a = $wg True (a + 1) +-- +-- g ds a = case $wg ds a of (# x, y#) -> (x, y) +-- +-- as $wg was expecting that a worker for f that would be inlined. +-- +-- See Note [The OPAQUE pragma and avoiding the reboxing of results] +g True a = f 2 a +g False a = g True (a+1) |