[MachineVerifier] Accept a MBB with a single landing pad successor.

The MachineVerifier used to check that there was always exactly one
unconditional branch to a non-landingpad (normal) successor.
If that normal successor to an invoke BB is unreachable, it seems
reasonable to only have one successor, the landing pad.
On targets other than AArch64 (and on AArch64 with a different testcase),
the branch folder turns the branch to the landing pad into a fallthrough.
The MachineVerifier, which relies on AnalyzeBranch, is unable to check
the condition, and doesn't complain. However, it does in this specific
testcase, where the branch to the landing pad remained.
Make the MachineVerifier accept it.

llvm-svn: 223059

1 files changed, 5 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/MachineVerifier.cpp b/llvm/lib/CodeGen/MachineVerifier.cpp
index 99f058312e6..cd19083f81b 100644
--- a/llvm/lib/CodeGen/MachineVerifier.cpp
+++ b/llvm/lib/CodeGen/MachineVerifier.cpp
@@ -592,7 +592,11 @@ MachineVerifier::visitMachineBasicBlockBefore(const MachineBasicBlock *MBB) {
       }
     } else if (TBB && !FBB && Cond.empty()) {
       // Block unconditionally branches somewhere.
-      if (MBB->succ_size() != 1+LandingPadSuccs.size()) {
+      // If the block has exactly one successor, that happens to be a
+      // landingpad, accept it as valid control flow.
+      if (MBB->succ_size() != 1+LandingPadSuccs.size() &&
+          (MBB->succ_size() != 1 || LandingPadSuccs.size() != 1 ||
+           *MBB->succ_begin() != *LandingPadSuccs.begin())) {
         report("MBB exits via unconditional branch but doesn't have "
                "exactly one CFG successor!", MBB);
       } else if (!MBB->isSuccessor(TBB)) {