[Debug] LCSSA: Insert dbg.value at the first available insertion point

Inserting a dbg.value instruction at the start of a basic block with a
landingpad instruction triggers a verifier failure. We should be OK if
we insert the instruction a bit later.

Speculative fix for the bot failure described here:
https://reviews.llvm.org/D42551

llvm-svn: 323482

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index a7eaffd1a7a..337ee0e9ef5 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -1373,7 +1373,9 @@ void llvm::insertDebugValuesForPHIs(BasicBlock *BB,
         auto PhiMAV = MetadataAsValue::get(C, ValueAsMetadata::get(PHI));
         NewDbgII->setOperand(0, PhiMAV);
         BasicBlock *Parent = PHI->getParent();
-        NewDbgII->insertBefore(Parent->getFirstNonPHIOrDbgOrLifetime());
+        auto InsertionPt = Parent->getFirstInsertionPt();
+        assert(InsertionPt != Parent->end() && "Ill-formed basic block");
+        NewDbgII->insertBefore(&*InsertionPt);
       }
     }
   }