[Assignment Tracking] Fix replaceVariableLocationOp for dbg.assign with DIArgList

The last time this function was updated DIArgLists were not supported for
dbg.assigns. Without this patch it's possible to now dereference an invalid
(the end) iterator. This occurs when the Address component gets replaced and
there's a DIArgList for the Value component (the contained values are
irrelevant).

The added unittest crashes without the code change in this patch.

Reviewed By: jmorse

Differential Revision: https://reviews.llvm.org/D147922

1 files changed, 7 insertions, 7 deletions

diff --git a/llvm/lib/IR/IntrinsicInst.cpp b/llvm/lib/IR/IntrinsicInst.cpp
index 1c78d4b..9270d70 100644
--- a/llvm/lib/IR/IntrinsicInst.cpp
+++ b/llvm/lib/IR/IntrinsicInst.cpp
@@ -135,14 +135,14 @@ void DbgVariableIntrinsic::replaceVariableLocationOp(Value *OldValue,
   assert(NewValue && "Values must be non-null");
   auto Locations = location_ops();
   auto OldIt = find(Locations, OldValue);
-  assert((OldIt != Locations.end() || DbgAssignAddrReplaced) &&
-         "OldValue must be a current location");
+  if (OldIt == Locations.end()) {
+    assert(DbgAssignAddrReplaced &&
+           "OldValue must be dbg.assign addr if unused in DIArgList");
+    return;
+  }
+
+  assert(OldIt != Locations.end() && "OldValue must be a current location");
   if (!hasArgList()) {
-    // Additional check necessary to avoid unconditionally replacing this
-    // operand when a dbg.assign address is replaced (DbgAssignAddrReplaced is
-    // true).
-    if (OldValue != getVariableLocationOp(0))
-      return;
     Value *NewOperand = isa<MetadataAsValue>(NewValue)
                             ? NewValue
                             : MetadataAsValue::get(