Index: cfe/trunk/lib/CodeGen/CGDebugInfo.cpp
===================================================================
--- cfe/trunk/lib/CodeGen/CGDebugInfo.cpp
+++ cfe/trunk/lib/CodeGen/CGDebugInfo.cpp
@@ -1827,32 +1827,24 @@
 }
 
 llvm::DINodeArray CGDebugInfo::CollectVarTemplateParams(const VarDecl *VL,
-    llvm::DIFile *Unit) {
-  if (auto *TS = dyn_cast<VarTemplateSpecializationDecl>(VL)) {
-    auto T = TS->getSpecializedTemplateOrPartial();
-    auto TA = TS->getTemplateArgs().asArray();
-    // Collect parameters for a partial specialization
-    if (T.is<VarTemplatePartialSpecializationDecl *>()) {
-      const TemplateParameterList *TList =
-        T.get<VarTemplatePartialSpecializationDecl *>()
-        ->getTemplateParameters();
-      return CollectTemplateParams(TList, TA, Unit);
-    }
-
-    // Collect parameters for an explicit specialization
-    if (T.is<VarTemplateDecl *>()) {
-      const TemplateParameterList *TList = T.get<VarTemplateDecl *>()
-        ->getTemplateParameters();
-      return CollectTemplateParams(TList, TA, Unit);
-    }
-  }
-  return llvm::DINodeArray();
+                                                        llvm::DIFile *Unit) {
+  // Always get the full list of parameters, not just the ones from the
+  // specialization. A partial specialization may have fewer parameters than
+  // there are arguments.
+  auto *TS = dyn_cast<VarTemplateSpecializationDecl>(VL);
+  if (!TS)
+    return llvm::DINodeArray();
+  VarTemplateDecl *T = TS->getSpecializedTemplate();
+  const TemplateParameterList *TList = T->getTemplateParameters();
+  auto TA = TS->getTemplateArgs().asArray();
+  return CollectTemplateParams(TList, TA, Unit);
 }
 
 llvm::DINodeArray CGDebugInfo::CollectCXXTemplateParams(
     const ClassTemplateSpecializationDecl *TSpecial, llvm::DIFile *Unit) {
-  // Always get the full list of parameters, not just the ones from
-  // the specialization.
+  // Always get the full list of parameters, not just the ones from the
+  // specialization. A partial specialization may have fewer parameters than
+  // there are arguments.
   TemplateParameterList *TPList =
       TSpecial->getSpecializedTemplate()->getTemplateParameters();
   const TemplateArgumentList &TAList = TSpecial->getTemplateArgs();
Index: cfe/trunk/test/CodeGenCXX/debug-info-template-member.cpp
===================================================================
--- cfe/trunk/test/CodeGenCXX/debug-info-template-member.cpp
+++ cfe/trunk/test/CodeGenCXX/debug-info-template-member.cpp
@@ -30,7 +30,7 @@
 // CHECK: {{![0-9]+}} = distinct !DIGlobalVariable(
 // CHECK-SAME: name: "var"
 // CHECK-SAME: templateParams: {{![0-9]+}}
-// CHECK: !DITemplateTypeParameter(name: "P", type: {{![0-9]+}})
+// CHECK: !DITemplateTypeParameter(name: "T", type: {{![0-9]+}})
 // CHECK: {{![0-9]+}} = distinct !DIGlobalVariable(
 // CHECK-SAME: name: "varray"
 // CHECK-SAME: templateParams: {{![0-9]+}}
Index: cfe/trunk/test/CodeGenCXX/debug-info-var-template-partial.cpp
===================================================================
--- cfe/trunk/test/CodeGenCXX/debug-info-var-template-partial.cpp
+++ cfe/trunk/test/CodeGenCXX/debug-info-var-template-partial.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -emit-llvm -triple x86_64-linux-gnu %s -o - -debug-info-kind=limited | FileCheck %s
+
+template <typename LHS, typename RHS> constexpr bool is_same_v = false;
+template <typename T> constexpr bool is_same_v<T, T> = true;
+
+template constexpr bool is_same_v<int, int>;
+static_assert(is_same_v<int, int>, "should get partial spec");
+
+// Note that the template arguments for the instantiated variable use the
+// parameter names from the primary template. The partial specialization might
+// not have enough parameters.
+
+// CHECK: distinct !DIGlobalVariable(name: "is_same_v", linkageName: "_Z9is_same_vIiiE", {{.*}} templateParams: ![[PARAMS:[0-9]+]])
+// CHECK: ![[PARAMS]] = !{![[LHS:[0-9]+]], ![[RHS:[0-9]+]]}
+// CHECK: ![[LHS]] = !DITemplateTypeParameter(name: "LHS", type: ![[INT:[0-9]+]])
+// CHECK: ![[INT]] = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+// CHECK: ![[RHS]] = !DITemplateTypeParameter(name: "RHS", type: ![[INT]])