Index: include/clang/Basic/LangOptions.def
===================================================================
--- include/clang/Basic/LangOptions.def
+++ include/clang/Basic/LangOptions.def
@@ -141,6 +141,7 @@
 LANGOPT(POSIXThreads      , 1, 0, "POSIX thread support")
 LANGOPT(Blocks            , 1, 0, "blocks extension to C")
 BENIGN_LANGOPT(EmitAllDecls      , 1, 0, "emitting all declarations")
+BENIGN_LANGOPT(EmitFwdTemplateChildren, 1, 0, "emit template parameter children in forward declarations")
 LANGOPT(MathErrno         , 1, 1, "errno in math functions")
 BENIGN_LANGOPT(HeinousExtensions , 1, 0, "extensions that we really don't like and may be ripped out at any time")
 LANGOPT(Modules           , 1, 0, "modules extension to C")
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -1412,6 +1412,14 @@
   HelpText<"Emit macro debug information">;
 def fno_debug_macro : Flag<["-"], "fno-debug-macro">, Group<f_Group>, Flags<[CoreOption]>,
   HelpText<"Do not emit macro debug information">;
+def fdebug_forward_template_params : Flag<["-"],
+  "fdebug-forward-template-params">, Group<f_Group>,
+  Flags<[DriverOption, CC1Option]>,
+  HelpText<"Debug info describes template parameters in forward declarations">;
+def fno_debug_forward_template_params : Flag<["-"],
+  "fno-debug-forward-template-params">, Group<f_Group>,
+  Flags<[DriverOption, CC1Option]>,
+  HelpText<"Debug info omits template parameters in forward declarations">;
 def fstrict_aliasing : Flag<["-"], "fstrict-aliasing">, Group<f_Group>,
   Flags<[DriverOption, CoreOption]>;
 def fstrict_enums : Flag<["-"], "fstrict-enums">, Group<f_Group>, Flags<[CC1Option]>,
Index: lib/CodeGen/CGDebugInfo.cpp
===================================================================
--- lib/CodeGen/CGDebugInfo.cpp
+++ lib/CodeGen/CGDebugInfo.cpp
@@ -833,6 +833,10 @@
   llvm::DICompositeType *RetTy = DBuilder.createReplaceableCompositeType(
       getTagForRecord(RD), RDName, Ctx, DefUnit, Line, 0, Size, Align,
       llvm::DINode::FlagFwdDecl, FullName);
+  if (CGM.getLangOpts().EmitFwdTemplateChildren)
+    if (auto *TSpecial = dyn_cast<ClassTemplateSpecializationDecl>(RD))
+      DBuilder.replaceArrays(RetTy, llvm::DINodeArray(),
+                             CollectCXXTemplateParams(TSpecial, DefUnit));
   ReplaceMap.emplace_back(
       std::piecewise_construct, std::make_tuple(Ty),
       std::make_tuple(static_cast<llvm::Metadata *>(RetTy)));
Index: lib/Driver/ToolChains/Clang.cpp
===================================================================
--- lib/Driver/ToolChains/Clang.cpp
+++ lib/Driver/ToolChains/Clang.cpp
@@ -2969,6 +2969,13 @@
     CmdArgs.push_back("-generate-type-units");
   }
 
+  // Decide how to render forward declarations of template instantiations.
+  // SCE defaults to on, others default to off.
+  if (Args.hasFlag(options::OPT_fdebug_forward_template_params,
+                   options::OPT_fno_debug_forward_template_params,
+                   DebuggerTuning == llvm::DebuggerKind::SCE))
+    CmdArgs.push_back("-fdebug-forward-template-params");
+
   RenderDebugInfoCompressionArgs(Args, CmdArgs, D);
 }
 
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -2201,6 +2201,7 @@
   Opts.EncodeExtendedBlockSig =
     Args.hasArg(OPT_fencode_extended_block_signature);
   Opts.EmitAllDecls = Args.hasArg(OPT_femit_all_decls);
+  Opts.EmitFwdTemplateChildren = Args.hasArg(OPT_fdebug_forward_template_params);
   Opts.PackStruct = getLastArgIntValue(Args, OPT_fpack_struct_EQ, 0, Diags);
   Opts.MaxTypeAlign = getLastArgIntValue(Args, OPT_fmax_type_align_EQ, 0, Diags);
   Opts.AlignDouble = Args.hasArg(OPT_malign_double);
Index: test/CodeGenCXX/debug-info-fwd-template-param.cpp
===================================================================
--- test/CodeGenCXX/debug-info-fwd-template-param.cpp
+++ test/CodeGenCXX/debug-info-fwd-template-param.cpp
@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 %s -triple=%itanium_abi_triple -debug-info-kind=limited -fdebug-forward-template-params -emit-llvm -o - | FileCheck --check-prefix=CHILD %s
+// RUN: %clang_cc1 %s -triple=%itanium_abi_triple -debug-info-kind=limited -fno-debug-forward-template-params -emit-llvm -o - | FileCheck --check-prefix=NONE %s
+// A forward declaration of a template instantiation should have template
+// parameter children (if we ask for them).
+
+template<typename T> class A {
+public:
+  A(T val);
+private:
+  T x;
+};
+
+struct B {
+  A<const int> *p;
+};
+
+B b;
+
+// CHILD:      !DICompositeType(tag: DW_TAG_class_type, name: "A<const int>"
+// CHILD-SAME:     flags: DIFlagFwdDecl
+// CHILD-SAME:     templateParams: [[PARAM_LIST:![0-9]*]]
+// CHILD:      [[PARAM_LIST]] = !{[[PARAM:![0-9]*]]}
+// CHILD:      [[PARAM]] = !DITemplateTypeParameter(name: "T",
+// CHILD-SAME:     type: [[CTYPE:![0-9]*]]
+// CHILD:      [[CTYPE]] = !DIDerivedType(tag: DW_TAG_const_type
+// CHILD-SAME:     baseType: [[BTYPE:![0-9]*]]
+// CHILD:      [[BTYPE]] = !DIBasicType(name: "int"
+
+// NONE:       !DICompositeType(tag: DW_TAG_class_type, name: "A<const int>"
+// NONE-SAME:      flags: DIFlagFwdDecl
+// NONE-NOT:       templateParams:
+// NONE-SAME:      )
Index: test/Driver/clang_f_opts.c
===================================================================
--- test/Driver/clang_f_opts.c
+++ test/Driver/clang_f_opts.c
@@ -495,6 +495,11 @@
 // CHECK-PROFILE-DEBUG: -fdebug-info-for-profiling
 // CHECK-NO-PROFILE-DEBUG-NOT: -fdebug-info-for-profiling
 
+// RUN: %clang -### -S -fdebug-forward-template-params %s 2>&1 | FileCheck -check-prefix=CHECK-FWD-TMPL %s
+// RUN: %clang -### -S -fno-debug-forward-template-params %s 2>&1 | FileCheck -check-prefix=CHECK-NO-FWD-TMPL %s
+// CHECK-FWD-TMPL: -fdebug-forward-template-params
+// CHECK-NO-FWD-TMPL-NOT: -fdebug-forward-template-params
+
 // RUN: %clang -### -S -fallow-editor-placeholders %s 2>&1 | FileCheck -check-prefix=CHECK-ALLOW-PLACEHOLDERS %s
 // RUN: %clang -### -S -fno-allow-editor-placeholders %s 2>&1 | FileCheck -check-prefix=CHECK-NO-ALLOW-PLACEHOLDERS %s
 // CHECK-ALLOW-PLACEHOLDERS: -fallow-editor-placeholders