Index: lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp
+++ lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp
@@ -209,6 +209,29 @@
                             DbgValues, DbgLabels);
   LLVM_DEBUG(DbgValues.dump());
 
+  auto AnalyzeDbgValue = [&](const MachineInstr &DV) {
+    bool InsidePrologue = false;
+    for (auto &MBB : *DV.getParent()->getParent())
+      for (auto &MI : MBB) {
+        if (!MI.isMetaInstruction() && !MI.getFlag(MachineInstr::FrameSetup) &&
+            MI.getDebugLoc())
+          goto done;
+        InsidePrologue |= (&MI == &DV);
+      }
+done:
+    errs() << "DV: " << DV;
+    if (!InsidePrologue) {
+      if (DV.getOperand(0).isReg()) {
+        if (DV.getOperand(0).getReg())
+          errs() << "  reg value outside prologue\n";
+        else
+          errs() << "  $noreg outside prologue\n";
+      } else
+        errs() << "  other type of value outside prologue\n";
+    } else
+      errs() << "  already inside prologue\n";
+  };
+
   // Request labels for the full history.
   for (const auto &I : DbgValues) {
     const auto &Ranges = I.second;
@@ -221,6 +244,7 @@
     if (DIVar->isParameter() &&
         getDISubprogram(DIVar->getScope())->describes(&MF->getFunction())) {
       LabelsBeforeInsn[Ranges.front().first] = Asm->getFunctionBegin();
+      AnalyzeDbgValue(*Ranges.front().first);
       if (Ranges.front().first->getDebugExpression()->isFragment()) {
         // Mark all non-overlapping initial fragments.
         for (auto I = Ranges.begin(); I != Ranges.end(); ++I) {
@@ -229,8 +253,10 @@
                           [&](DbgValueHistoryMap::InstrRange Pred) {
                             return !Fragment->fragmentsOverlap(
                                 Pred.first->getDebugExpression());
-                          }))
+                          })) {
             LabelsBeforeInsn[I->first] = Asm->getFunctionBegin();
+            AnalyzeDbgValue(*I->first);
+          }
           else
             break;
         }