Fix a latent bug where, after emitting an expression statement, we would

delete the block we began emitting into if it had no predecessors.  We never
want to do this, because there are several valid cases during statement
emission where an existing block has no known predecessors but will acquire
some later.  The case in my test case doesn't inherently fall into this 
category, because we could safely emit the case-range code before the statement
body, but there are examples with labels that can't be fallen into 
that would also demonstrate this bug.

rdar://problem/8837067

llvm-svn: 123303

1 files changed, 17 insertions, 0 deletions

diff --git a/clang/test/CodeGen/switch.c b/clang/test/CodeGen/switch.c
index dc2d27bc16d..8b94a0976e6 100644
--- a/clang/test/CodeGen/switch.c
+++ b/clang/test/CodeGen/switch.c
@@ -194,3 +194,20 @@ int f13(unsigned x) {
     return 0;
   }
 }
+
+// Don't delete a basic block that we want to introduce later references to.
+// This isn't really specific to switches, but it's easy to show with them.
+// rdar://problem/8837067
+int f14(int x) {
+  switch (x) {
+
+  // case range so that the case block has no predecessors
+  case 0 ... 15:
+    // any expression which doesn't introduce a new block
+    (void) 0;
+    // kaboom
+
+  default:
+    return x;
+  }
+}