test case https://bugs.llvm.org/show_bug.cgi?id=43222

gistfile1.diff

diff --git a/llvm/unittests/IR/InstructionsTest.cpp b/llvm/unittests/IR/InstructionsTest.cpp
index 9b9efe33cfed..159c63a5c5c4 100644
--- a/llvm/unittests/IR/InstructionsTest.cpp
+++ b/llvm/unittests/IR/InstructionsTest.cpp
@@ -1061,5 +1061,55 @@ TEST(InstructionsTest, FNegInstruction) {
   FNeg->deleteValue();
 }
 
+TEST(InstructionsTest, CallBrInstruction) {
+  LLVMContext Context;
+  std::unique_ptr<Module> M = parseIR(Context, R"(
+define void @foo() {
+entry:
+  callbr void asm sideeffect "// XXX: ${0:l}", "X"(i8* blockaddress(@foo, %branch_test.exit))
+          to label %land.rhs.i [label %branch_test.exit]
+
+land.rhs.i:
+  br label %branch_test.exit
+
+branch_test.exit:
+  %0 = phi i1 [ true, %entry ], [ false, %land.rhs.i ]
+  br i1 %0, label %if.end, label %if.then
+
+if.then:
+  ret void
+
+if.end:
+  ret void
+}
+)");
+  Function *Foo = M->getFunction("foo");
+  auto BBs = Foo->getBasicBlockList().begin();
+  CallBrInst &CBI = cast<CallBrInst>(BBs->front());
+  ++BBs;
+  ++BBs;
+  BasicBlock &BranchTestExit = *BBs;
+  ++BBs;
+  BasicBlock &IfThen = *BBs;
+
+  // Test that setting the first indirect destination of callbr updates the dest
+  EXPECT_EQ(&BranchTestExit, CBI.getIndirectDest(0));
+  CBI.setIndirectDest(0, &IfThen);
+  EXPECT_EQ(&IfThen, CBI.getIndirectDest(0));
+
+  // Further, test that changing the indirect destination updates the arg
+  // operand to use the block address of the new indirect destination basic
+  // block. This is a critical invariant of CallBrInst.
+  BlockAddress *IndirectBA = BlockAddress::get(CBI.getIndirectDest(0));
+  BlockAddress *ArgBA = cast<BlockAddress>(CBI.getArgOperand(0));
+  EXPECT_EQ(IndirectBA, ArgBA) << "After setting the indirect destination, "
+    "callbr had an indirect destination of '" <<
+    CBI.getIndirectDest(0)->getName() << "', but a argument of '" <<
+    ArgBA->getBasicBlock()->getName() << "'. These should always match:\n" <<
+    CBI;
+  EXPECT_EQ(IndirectBA->getBasicBlock(), &IfThen);
+  EXPECT_EQ(ArgBA->getBasicBlock(), &IfThen);
+}
+
 } // end anonymous namespace
 } // end namespace llvm