Add regression test for #7378wip/sjakobi/T7378-test

Closes #7378.

3 files changed, 15 insertions, 0 deletions

diff --git a/testsuite/tests/simplCore/should_compile/T7378.hs b/testsuite/tests/simplCore/should_compile/T7378.hs
new file mode 100644
index 0000000000..d32014bb5a
--- /dev/null
+++ b/testsuite/tests/simplCore/should_compile/T7378.hs
@@ -0,0 +1,11 @@
+module T7378 where
+
+-- The original example, now compiled to a simple right-shift
+fun0 :: Int -> Int
+fun0 i = i `div` 2
+
+-- We expect CSE to combine the alternatives of a redundant
+-- case analysis on `i > 0`.
+-- This didn't happen before GHC 8.2.
+fun1 :: Int -> Int
+fun1 i = i `div` 12345
diff --git a/testsuite/tests/simplCore/should_compile/T7378.stderr b/testsuite/tests/simplCore/should_compile/T7378.stderr
new file mode 100644
index 0000000000..b8bee5ec94
--- /dev/null
+++ b/testsuite/tests/simplCore/should_compile/T7378.stderr
@@ -0,0 +1,3 @@
+      case i of { I# ww1 ->
+      case <# ww1 0# of {
+  = / i -> case i of { I# ww1 -> I# (uncheckedIShiftRA# ww1 1#) }
diff --git a/testsuite/tests/simplCore/should_compile/all.T b/testsuite/tests/simplCore/should_compile/all.T
index 3a16d55508..70324ea44d 100644
--- a/testsuite/tests/simplCore/should_compile/all.T
+++ b/testsuite/tests/simplCore/should_compile/all.T
@@ -130,6 +130,7 @@ test('T6082-RULE', normal, compile, [''])
 test('T7165', [], makefile_test, ['T7165'])
 test('T7287', normal, compile, [''])
 test('T7360', only_ways(['optasm']), compile, ['-ddump-simpl -dsuppress-uniques -dsuppress-ticks'])
+test('T7378', [grep_errmsg(r'case'), only_ways(['optasm'])], compile, ['-O -funfolding-use-threshold=109 -ddump-simpl -dsuppress-all -dsuppress-uniques'])
 test('T5366',
      normal,
      makefile_test, ['T5366'])