2 files changed, 36 insertions, 2 deletions

diff --git a/lib/CodeGen/MachineBasicBlock.cpp b/lib/CodeGen/MachineBasicBlock.cpp
index 4c5fe4c..f05b6c1 100644
--- a/lib/CodeGen/MachineBasicBlock.cpp
+++ b/lib/CodeGen/MachineBasicBlock.cpp
@@ -297,8 +297,14 @@ void MachineBasicBlock::updateTerminator() {
         TII->RemoveBranch(*this);
     } else {
       // The block has an unconditional fallthrough. If its successor is not
-      // its layout successor, insert a branch.
-      TBB = *succ_begin();
+      // its layout successor, insert a branch. First we have to locate the
+      // only non-landing-pad successor, as that is the fallthrough block.
+      for (succ_iterator SI = succ_begin(), SE = succ_end(); SI != SE; ++SI) {
+        if ((*SI)->isLandingPad())
+          continue;
+        assert(!TBB && "Found more than one non-landing-pad successor!");
+        TBB = *SI;
+      }
       if (!isLayoutSuccessor(TBB))
         TII->InsertBranch(*this, TBB, 0, Cond, dl);
     }
diff --git a/test/CodeGen/X86/block-placement.ll b/test/CodeGen/X86/block-placement.ll
index 7361ae4..8a8bf13 100644
--- a/test/CodeGen/X86/block-placement.ll
+++ b/test/CodeGen/X86/block-placement.ll
@@ -475,3 +475,31 @@ exit:
 }
 
 !2 = metadata !{metadata !"branch_weights", i32 3, i32 1}
+
+declare i32 @__gxx_personality_v0(...)
+
+define void @test_eh_lpad_successor() {
+; Some times the landing pad ends up as the first successor of an invoke block.
+; When this happens, a strange result used to fall out of updateTerminators: we
+; didn't correctly locate the fallthrough successor, assuming blindly that the
+; first one was the fallthrough successor. As a result, we would add an
+; erroneous jump to the landing pad thinking *that* was the default successor.
+; CHECK: test_eh_lpad_successor
+; CHECK: %entry
+; CHECK-NOT: jmp
+; CHECK: %loop
+
+entry:
+  invoke i32 @f() to label %preheader unwind label %lpad
+
+preheader:
+  br label %loop
+
+lpad:
+  %lpad.val = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          cleanup
+  resume { i8*, i32 } %lpad.val
+
+loop:
+  br label %loop
+}