Index: llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
===================================================================
--- llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -1578,11 +1578,16 @@
     assert(Element->getTag() == dwarf::DW_TAG_subrange_type);
 
     const DISubrange *Subrange = cast<DISubrange>(Element);
-    assert(!Subrange->getRawLowerBound() &&
-           "codeview doesn't support subranges with lower bounds");
     int64_t Count = -1;
-    if (auto *CI = Subrange->getCount().dyn_cast<ConstantInt*>())
-      Count = CI->getSExtValue();
+    // Calculate the count if either LowerBound is absent or is zero and
+    // either of Count or UpperBound are constant.
+    auto *LI = Subrange->getLowerBound().dyn_cast<ConstantInt *>();
+    if (!Subrange->getRawLowerBound() || (LI && (LI->getSExtValue() == 0))) {
+      if (auto *CI = Subrange->getCount().dyn_cast<ConstantInt*>())
+        Count = CI->getSExtValue();
+      else if (auto *UI = Subrange->getUpperBound().dyn_cast<ConstantInt*>())
+        Count = UI->getSExtValue() + 1; // LowerBound is zero
+    }
 
     // Forward declarations of arrays without a size and VLAs use a count of -1.
     // Emit a count of zero in these cases to match what MSVC does for arrays