Serialize and Deserialize Debug Scopes (#76934)

This patch adds support for serialization and deserialization of
debug scopes.

Debug scopes are serialized in post order and enablement is 
controlled through the experimental-serialize-debug-info flag which
is turned off by default. Functions only referred to by these debug
scopes are deserialized as zombie functions directly.

Author: usama54321

include/swift/Frontend/FrontendOptions.h

@@ -129,6 +129,7 @@ class FrontendOptions {
   /// Include local definitions/references in the index data.
   bool IndexIncludeLocals = false;
 
+  bool SerializeDebugInfoSIL = false;
   /// If building a module from interface, ignore compiler flags
   /// specified in the swiftinterface.
   bool ExplicitInterfaceBuild = false;

include/swift/Option/Options.td

@@ -827,6 +827,10 @@ def experimental_package_interface_load:
   Flags<[FrontendOption, HelpHidden]>,
   HelpText<"Enables loading a package interface if in the same package specified with package-name">;
 
+def experimental_serialize_debug_info:
+  Flag<["-"], "experimental-serialize-debug-info">,
+  Flags<[FrontendOption, HelpHidden]>,
+  HelpText<"Enables seriailzation/deserialization of debug scopes">;
 // Diagnostic control options
 def suppress_warnings : Flag<["-"], "suppress-warnings">,
   Flags<[FrontendOption]>,

include/swift/Serialization/SerializationOptions.h

@@ -151,6 +151,7 @@ class SerializationOptions {
 
   bool AutolinkForceLoad = false;
   bool SerializeAllSIL = false;
+  bool SerializeDebugInfoSIL = false;
   bool SerializeOptionsForDebugging = false;
   bool IsSIB = false;
   bool DisableCrossModuleIncrementalInfo = false;

lib/Driver/ToolChains.cpp

@@ -204,6 +204,12 @@ void ToolChain::addCommonFrontendArgs(const OutputInfo &OI,
     arguments.push_back("-disable-objc-interop");
   }
 
+  if (const Arg *arg = inputArgs.getLastArg(
+        options::OPT_experimental_serialize_debug_info)) {
+    arguments.push_back(
+        inputArgs.MakeArgString(Twine("-experimental-serialize-debug-info")));
+  }
+
   if (inputArgs.hasArg(options::OPT_experimental_hermetic_seal_at_link)) {
     arguments.push_back("-enable-llvm-vfe");
     arguments.push_back("-enable-llvm-wme");

lib/Frontend/ArgsToFrontendOptionsConverter.cpp

@@ -89,6 +89,8 @@ bool ArgsToFrontendOptionsConverter::convert(
   Opts.IndexSystemModules |= Args.hasArg(OPT_index_system_modules);
   Opts.IndexIgnoreStdlib |= Args.hasArg(OPT_index_ignore_stdlib);
   Opts.IndexIncludeLocals |= Args.hasArg(OPT_index_include_locals);
+  Opts.SerializeDebugInfoSIL |=
+      Args.hasArg(OPT_experimental_serialize_debug_info);
 
   Opts.EmitVerboseSIL |= Args.hasArg(OPT_emit_verbose_sil);
   Opts.EmitSortedSIL |= Args.hasArg(OPT_emit_sorted_sil);

lib/Frontend/Frontend.cpp

@@ -200,6 +200,7 @@ SerializationOptions CompilerInvocation::computeSerializationOptions(
   serializationOpts.ModuleLinkName = opts.ModuleLinkName;
   serializationOpts.UserModuleVersion = opts.UserModuleVersion;
   serializationOpts.AllowableClients = opts.AllowableClients;
+  serializationOpts.SerializeDebugInfoSIL = opts.SerializeDebugInfoSIL;
 
   serializationOpts.PublicDependentLibraries =
       getIRGenOptions().PublicLinkLibraries;

lib/SIL/Parser/ParseSIL.cpp

@@ -86,11 +86,16 @@ SILParserState::~SILParserState() {
   }
 
   // Turn any debug-info-only function declarations into zombies.
-  for (auto *Fn : PotentialZombieFns)
-    if (Fn->isExternalDeclaration()) {
+  markZombies();
+}
+
+void SILParserState::markZombies() {
+  for (auto *Fn : PotentialZombieFns) {
+    if (Fn->isExternalDeclaration() && !Fn->isZombie()) {
       Fn->setInlined();
       M.eraseFunction(Fn);
     }
+  }
 }
 
 std::unique_ptr<SILModule>
@@ -124,6 +129,11 @@ ParseSILModuleRequest::evaluate(Evaluator &evaluator,
            "Failed to parse SIL but did not emit any errors!");
     return SILModule::createEmptyModule(desc.context, desc.conv, desc.opts);
   }
+
+  // Mark functions as zombies before calling SILVerifier as functions referred
+  //to by debug scopes only can fail verifier checks
+  parserState.markZombies();
+
   // If SIL parsing succeeded, verify the generated SIL.
   if (!parser.Diags.hadAnyError() && !DisableInputVerify) {
     silMod->verify(/*SingleFunction=*/true, !ParseIncompleteOSSA);

lib/SIL/Parser/SILParserState.h

@@ -62,6 +62,9 @@ class SILParserState : public SILParserStateBase {
   bool parseSILCoverageMap(Parser &P) override;
   bool parseSILProperty(Parser &P) override;
   bool parseSILScope(Parser &P) override;
+
+  /// Mark potential zombie functions as zombies.
+  void markZombies();
 };
 
 } // end namespace swift