Index: lib/IR/IntrinsicInst.cpp
===================================================================
--- lib/IR/IntrinsicInst.cpp
+++ lib/IR/IntrinsicInst.cpp
@@ -43,8 +43,10 @@
   if (auto *V = dyn_cast<ValueAsMetadata>(MD))
     return V->getValue();
 
-  // When the value goes to null, it gets replaced by an empty MDNode.
-  assert(!cast<MDNode>(MD)->getNumOperands() && "Expected an empty MDNode");
+  if (!AllowNullOp) {
+    // When the value goes to null, it gets replaced by an empty MDNode.
+    assert(!cast<MDNode>(MD)->getNumOperands() && "Expected an empty MDNode");
+  }
   return nullptr;
 }
 
Index: test/DebugInfo/Generic/PR37395.ll
===================================================================
--- /dev/null
+++ test/DebugInfo/Generic/PR37395.ll
@@ -0,0 +1,65 @@
+; RUN: opt -lcssa -S %s | FileCheck %s
+source_filename = "small.c"
+
+@a = common dso_local global i32 0, align 4, !dbg !0
+
+; CHECK-LABEL: @f
+define dso_local void @f() !dbg !11 {
+entry:
+  br label %for.cond, !dbg !18
+
+for.cond:                                         ; preds = %for.inc, %entry
+  %0 = load i32, i32* @a, align 4, !dbg !19
+  %tobool = icmp ne i32 %0, 0, !dbg !20
+  br i1 %tobool, label %for.body, label %for.end, !dbg !20
+
+for.body:                                         ; preds = %for.cond
+  br label %L, !dbg !20
+
+; CHECK: L:
+; CHECK:   call void @llvm.dbg.label
+L:                                                ; preds = %for.body
+  call void @llvm.dbg.label(metadata !15), !dbg !21
+  br label %for.inc, !dbg !20
+
+for.inc:                                          ; preds = %L
+  %1 = load i32, i32* @a, align 4, !dbg !22
+  %inc = add nsw i32 %1, 1, !dbg !22
+  store i32 %inc, i32* @a, align 4, !dbg !22
+  br label %for.cond, !dbg !23, !llvm.loop !24
+
+for.end:                                          ; preds = %for.cond
+  ret void, !dbg !26
+}
+
+declare void @llvm.dbg.label(metadata)
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!7, !8, !9}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line: 1, type: !6, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 7.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
+!3 = !DIFile(filename: "small.c", directory: "./")
+!4 = !{}
+!5 = !{!0}
+!6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!7 = !{i32 2, !"Dwarf Version", i32 4}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{i32 1, !"wchar_size", i32 4}
+!11 = distinct !DISubprogram(name: "f", scope: !3, file: !3, line: 3, type: !12, isLocal: false, isDefinition: true, scopeLine: 4, isOptimized: true, unit: !2, retainedNodes: !14)
+!12 = !DISubroutineType(types: !13)
+!13 = !{null}
+!14 = !{!15}
+!15 = !DILabel(scope: !16, name: "L", file: !3, line: 6)
+!16 = distinct !DILexicalBlock(scope: !17, file: !3, line: 5, column: 3)
+!17 = distinct !DILexicalBlock(scope: !11, file: !3, line: 5, column: 3)
+!18 = !DILocation(line: 5, column: 3, scope: !11)
+!19 = !DILocation(line: 5, column: 10, scope: !16)
+!20 = !DILocation(line: 5, column: 3, scope: !17)
+!21 = !DILocation(line: 6, column: 3, scope: !16)
+!22 = !DILocation(line: 5, column: 14, scope: !16)
+!23 = !DILocation(line: 5, column: 3, scope: !16)
+!24 = distinct !{!24, !20, !25}
+!25 = !DILocation(line: 6, column: 5, scope: !17)
+!26 = !DILocation(line: 7, column: 1, scope: !11)