[DWARF] Allow forward declarations of a class template instantiation

to have child entries describing the template parameters.  This will
be on by default for SCE tuning.

Differential Revision: https://reviews.llvm.org/D14358


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@314444 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Driver/CC1Options.td

@@ -200,6 +200,9 @@ def arange_sections : Flag<["-"], "arange_sections">,
 def dwarf_ext_refs : Flag<["-"], "dwarf-ext-refs">,
   HelpText<"Generate debug info with external references to clang modules"
            " or precompiled headers">;
+def debug_forward_template_params : Flag<["-"], "debug-forward-template-params">,
+  HelpText<"Emit complete descriptions of template parameters in forward"
+           " declarations">;
 def fforbid_guard_variables : Flag<["-"], "fforbid-guard-variables">,
   HelpText<"Emit an error if a C++ static local initializer would need a guard variable">;
 def no_implicit_float : Flag<["-"], "no-implicit-float">,

include/clang/Frontend/CodeGenOptions.def

@@ -219,6 +219,10 @@ CODEGENOPT(EnableSplitDwarf, 1, 0) ///< Whether to enable split DWARF
 CODEGENOPT(SplitDwarfInlining, 1, 1) ///< Whether to include inlining info in the
                                      ///< skeleton CU to allow for symbolication
 				     ///< of inline stack frames without .dwo files.
+CODEGENOPT(DebugFwdTemplateParams, 1, 0) ///< Whether to emit complete
+                                         ///< template parameter descriptions in
+                                         ///< forward declarations (versus just
+                                         ///< including them in the name).
 
 CODEGENOPT(EmitLLVMUseLists, 1, 0) ///< Control whether to serialize use-lists.
 

lib/CodeGen/CGDebugInfo.cpp

@@ -833,6 +833,10 @@ CGDebugInfo::getOrCreateRecordFwdDecl(const RecordType *Ty,
   llvm::DICompositeType *RetTy = DBuilder.createReplaceableCompositeType(
       getTagForRecord(RD), RDName, Ctx, DefUnit, Line, 0, Size, Align,
       llvm::DINode::FlagFwdDecl, FullName);
+  if (CGM.getCodeGenOpts().DebugFwdTemplateParams)
+    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)));

lib/Driver/ToolChains/Clang.cpp

@@ -2969,6 +2969,11 @@ static void RenderDebugOptions(const ToolChain &TC, const Driver &D,
     CmdArgs.push_back("-generate-type-units");
   }
 
+  // Decide how to render forward declarations of template instantiations.
+  // SCE wants full descriptions, others just get them in the name.
+  if (DebuggerTuning == llvm::DebuggerKind::SCE)
+    CmdArgs.push_back("-debug-forward-template-params");
+
   RenderDebugInfoCompressionArgs(Args, CmdArgs, D);
 }
 

lib/Frontend/CompilerInvocation.cpp

@@ -528,6 +528,7 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   Opts.SplitDwarfInlining = !Args.hasArg(OPT_fno_split_dwarf_inlining);
   Opts.DebugTypeExtRefs = Args.hasArg(OPT_dwarf_ext_refs);
   Opts.DebugExplicitImport = Triple.isPS4CPU();
+  Opts.DebugFwdTemplateParams = Args.hasArg(OPT_debug_forward_template_params);
 
   for (const auto &Arg : Args.getAllArgValues(OPT_fdebug_prefix_map_EQ))
     Opts.DebugPrefixMap.insert(StringRef(Arg).split('='));

test/CodeGenCXX/debug-info-fwd-template-param.cpp

@@ -0,0 +1,20 @@
+// RUN: %clang_cc1 %s -triple=%itanium_abi_triple -debug-info-kind=limited -debug-forward-template-params -emit-llvm -o - | FileCheck --check-prefix=CHILD %s
+// RUN: %clang_cc1 %s -triple=%itanium_abi_triple -debug-info-kind=limited -emit-llvm -o - | FileCheck --check-prefix=NONE %s
+// A DWARF forward declaration of a template instantiation should have template
+// parameter children (if we ask for them).
+
+template<typename T> class A;
+A<int> *p;
+
+// CHILD:      !DICompositeType(tag: DW_TAG_class_type, name: "A<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: [[BTYPE:![0-9]*]]
+// CHILD:      [[BTYPE]] = !DIBasicType(name: "int"
+
+// NONE:       !DICompositeType(tag: DW_TAG_class_type, name: "A<int>"
+// NONE-SAME:      flags: DIFlagFwdDecl
+// NONE-NOT:       templateParams:
+// NONE-SAME:      )