DebugInfo: Add (initially no-op) -gsimple-template-names={simple,mangled}

This is to build the foundation of a new debug info feature to use only
the base name of template as its debug info name (eg: "t1" instead of
the full "t1<int>"). The intent being that a consumer can still retrieve
all that information from the DW_TAG_template_*_parameters.

So gno-simple-template-names is business as usual/previously ("t1<int>")
   =simple is the simplified name ("t1")
   =mangled is a special mode to communicate the full information, but
   also indicate that the name should be able to be simplified. The data
   is encoded as "_STNt1|<int>" which will be matched with an
   llvm-dwarfdump --verify feature to deconstruct this name, rebuild the
   original name, and then try to rebuild the simple name via the DWARF
   tags - then compare the latter and the former to ensure that all the
   data necessary to fully rebuild the name is present.

1 files changed, 14 insertions, 0 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 10b2e96..2368e68 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1411,6 +1411,14 @@ void CompilerInvocation::GenerateCodeGenArgs(
                llvm::DICompileUnit::DebugNameTableKind::Default))
     GenerateArg(Args, OPT_gpubnames, SA);
 
+  auto TNK = Opts.getDebugSimpleTemplateNames();
+  if (TNK != codegenoptions::DebugTemplateNamesKind::Full) {
+    if (TNK == codegenoptions::DebugTemplateNamesKind::Simple)
+      GenerateArg(Args, OPT_gsimple_template_names_EQ, "simple", SA);
+    if (TNK == codegenoptions::DebugTemplateNamesKind::Mangled)
+      GenerateArg(Args, OPT_gsimple_template_names_EQ, "mangled", SA);
+
+  }
   // ProfileInstrumentUsePath is marshalled automatically, no need to generate
   // it or PGOUseInstrumentor.
 
@@ -1685,6 +1693,12 @@ bool CompilerInvocation::ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args,
           : Args.hasArg(OPT_gpubnames)
                 ? llvm::DICompileUnit::DebugNameTableKind::Default
                 : llvm::DICompileUnit::DebugNameTableKind::None);
+  if (const Arg *A = Args.getLastArg(OPT_gsimple_template_names_EQ)) {
+    Opts.setDebugSimpleTemplateNames(
+        StringRef(A->getValue()) == "simple"
+            ? codegenoptions::DebugTemplateNamesKind::Simple
+            : codegenoptions::DebugTemplateNamesKind::Mangled);
+  }
 
   if (!Opts.ProfileInstrumentUsePath.empty())
     setPGOUseInstrumentor(Opts, Opts.ProfileInstrumentUsePath);