1 files changed, 110 insertions, 0 deletions
diff --git a/test/Transforms/LowerSwitch/fold-popular-case-to-unreachable-default.ll b/test/Transforms/LowerSwitch/fold-popular-case-to-unreachable-default.ll
new file mode 100644
index 0000000..54929c5
--- /dev/null
+++ b/test/Transforms/LowerSwitch/fold-popular-case-to-unreachable-default.ll
@@ -0,0 +1,110 @@
+; RUN: opt %s -lowerswitch -S | FileCheck %s
+
+define void @foo(i32 %x, i32* %p) {
+; Cases 2 and 4 are removed and become the new default case.
+; It is now enough to use two icmps to lower the switch.
+;
+; CHECK-LABEL: @foo
+; CHECK:       icmp slt i32 %x, 5
+; CHECK:       icmp eq i32 %x, 1
+; CHECK-NOT:   icmp
+;
+entry:
+  switch i32 %x, label %default [
+    i32 1, label %bb0
+    i32 2, label %popular
+    i32 4, label %popular
+    i32 5, label %bb1
+  ]
+bb0:
+  store i32 0, i32* %p
+  br label %exit
+bb1:
+  store i32 1, i32* %p
+  br label %exit
+popular:
+  store i32 2, i32* %p
+  br label %exit
+exit:
+  ret void
+default:
+  unreachable
+}
+
+define void @unreachable_gap(i64 %x, i32* %p) {
+; Cases 6 and INT64_MAX become the new default, but we still exploit the fact
+; that 3-4 is unreachable, so four icmps is enough.
+
+; CHECK-LABEL: @unreachable_gap
+; CHECK:       icmp slt i64 %x, 2
+; CHECK:       icmp slt i64 %x, 5
+; CHECK:       icmp eq  i64 %x, 5
+; CHECK:       icmp slt i64 %x, 1
+; CHECK-NOT:   icmp
+
+entry:
+  switch i64 %x, label %default [
+    i64 -9223372036854775808, label %bb0
+    i64 1, label %bb1
+    i64 2, label %bb2
+    i64 5, label %bb3
+    i64 6, label %bb4
+    i64 9223372036854775807, label %bb4
+  ]
+bb0:
+  store i32 0, i32* %p
+  br label %exit
+bb1:
+  store i32 1, i32* %p
+  br label %exit
+bb2:
+  store i32 2, i32* %p
+  br label %exit
+bb3:
+  store i32 3, i32* %p
+  br label %exit
+bb4:
+  store i32 4, i32* %p
+  br label %exit
+exit:
+  ret void
+default:
+  unreachable
+}
+
+
+
+define void @nocases(i32 %x, i32* %p) {
+; Don't fall over when there are no cases.
+;
+; CHECK-LABEL: @nocases
+; CHECK-LABEL: entry
+; CHECK-NEXT:  br label %default
+;
+entry:
+  switch i32 %x, label %default [
+  ]
+default:
+  unreachable
+}
+
+define void @nocasesleft(i32 %x, i32* %p) {
+; Cases 2 and 4 are removed and we are left with no cases.
+;
+; CHECK-LABEL: @nocasesleft
+; CHECK-LABEL: entry
+; CHECK-NEXT:  br label %popular
+;
+entry:
+  switch i32 %x, label %default [
+    i32 2, label %popular
+    i32 4, label %popular
+  ]
+popular:
+  store i32 2, i32* %p
+  br label %exit
+exit:
+  ret void
+default:
+  unreachable
+}