[Incremental] Plumb -verify-incremental-dependencies Through The Frontend and Driver

When enabled at the driver level, the frontends will inherit the flag. For each frontend that recieves this option, all primaries will have their reference dependencies validated.

include/swift/AST/DiagnosticsDriver.def

@@ -159,6 +159,9 @@ WARNING(warn_ignore_embed_bitcode_marker, none,
 WARNING(verify_debug_info_requires_debug_option,none,
         "ignoring '-verify-debug-info'; no debug info is being generated", ())
 
+ERROR(verify_incremental_dependencies_needs_incremental,none,
+      "'-verify-incremental-dependencies' requires '-incremental'", ())
+
 ERROR(error_profile_missing,none,
       "no profdata file exists at '%0'", (StringRef))
 

include/swift/Frontend/DiagnosticVerifier.h

@@ -21,7 +21,9 @@
 #include "swift/Basic/LLVM.h"
 
 namespace swift {
+  class FileUnit;
   class SourceManager;
+  class SourceFile;
 
   /// Set up the specified source manager so that diagnostics are captured
   /// instead of being printed.
@@ -34,6 +36,9 @@ namespace swift {
   /// This returns true if there are any mismatches found.
   bool verifyDiagnostics(SourceManager &SM, ArrayRef<unsigned> BufferIDs,
                          bool autoApplyFixes, bool ignoreUnknown);
+
+  bool verifyDependencies(SourceManager &SM, ArrayRef<FileUnit *> SFs);
+  bool verifyDependencies(SourceManager &SM, ArrayRef<SourceFile *> SFs);
 }
 
 #endif

include/swift/Frontend/FrontendOptions.h

@@ -263,6 +263,9 @@ public:
   /// Should we lock .swiftinterface while generating .swiftmodule from it?
   bool DisableInterfaceFileLock = false;
 
+  /// Should we enable the dependency verifier for all primary files known to this frontend?
+  bool VerifyDependencies = false;
+
   /// The different modes for validating TBD against the LLVM IR.
   enum class TBDValidationMode {
     Default,        ///< Do the default validation for the current platform.

include/swift/Option/Options.td

@@ -184,6 +184,11 @@ Flag<["-"], "driver-verify-fine-grained-dependency-graph-after-every-import">,
 InternalDebugOpt,
 HelpText<"Debug DriverGraph by verifying it after every import">;
 
+def verify_incremental_dependencies :
+  Flag<["-"], "verify-incremental-dependencies">,
+  Flags<[FrontendOption, HelpHidden]>,
+  HelpText<"Enable the dependency verifier for each frontend job">;
+
 def driver_emit_fine_grained_dependency_dot_file_after_every_import :
 Flag<["-"], "driver-emit-fine-grained-dependency-dot-file-after-every-import">,
 InternalDebugOpt,

lib/Driver/Driver.cpp

@@ -179,6 +179,24 @@ static void validateDebugInfoArgs(DiagnosticEngine &diags,
       diags.diagnose(SourceLoc(), diag::error_invalid_debug_prefix_map, A);
 }
 
+static void validateVerifyIncrementalArgs(DiagnosticEngine &diags,
+                                          const ArgList &args) {
+  // No option? No problem!
+  if (!args.hasArg(options::OPT_verify_incremental_dependencies)) {
+    return;
+  }
+
+  // Make sure we see -incremental but not -wmo, no matter in what order they're
+  // in - the build systems can pass them both and just hope the last one wins.
+  if (args.hasArg(options::OPT_incremental) &&
+      !args.hasArg(options::OPT_whole_module_optimization)) {
+    return;
+  }
+
+  diags.diagnose(SourceLoc(),
+                 diag::verify_incremental_dependencies_needs_incremental);
+}
+
 static void validateCompilationConditionArgs(DiagnosticEngine &diags,
                                              const ArgList &args) {
   for (const Arg *A : args.filtered(options::OPT_D)) {
@@ -239,6 +257,7 @@ static void validateArgs(DiagnosticEngine &diags, const ArgList &args,
   validateCompilationConditionArgs(diags, args);
   validateSearchPathArgs(diags, args);
   validateAutolinkingArgs(diags, args, T);
+  validateVerifyIncrementalArgs(diags, args);
 }
 
 std::unique_ptr<ToolChain>

lib/Driver/ToolChains.cpp

@@ -254,7 +254,9 @@ static void addCommonFrontendArgs(const ToolChain &TC, const OutputInfo &OI,
   inputArgs.AddLastArg(arguments, options::OPT_disable_parser_lookup);
   inputArgs.AddLastArg(arguments,
                        options::OPT_enable_experimental_concise_pound_file);
-
+  inputArgs.AddLastArg(arguments,
+                       options::OPT_verify_incremental_dependencies);
+  
   // Pass on any build config options
   inputArgs.AddAllArgs(arguments, options::OPT_D);
 

lib/Frontend/ArgsToFrontendOptionsConverter.cpp

@@ -176,6 +176,7 @@ bool ArgsToFrontendOptionsConverter::convert(
 
   Opts.EnableSourceImport |= Args.hasArg(OPT_enable_source_import);
   Opts.ImportUnderlyingModule |= Args.hasArg(OPT_import_underlying_module);
+  Opts.VerifyDependencies |= Args.hasArg(OPT_verify_incremental_dependencies);
 
   computeImportObjCHeaderOptions();
   computeImplicitImportModuleNames();

lib/FrontendTool/FrontendTool.cpp

@@ -1480,6 +1480,12 @@ computeDeallocatableResources(const CompilerInvocation &Invocation,
     return DeallocatableResources::SILModule;
   }
 
+  // Verifying incremental dependencies relies on access to the Swift Module's
+  // source files. We can still free the SIL module, though.
+  if (Invocation.getFrontendOptions().VerifyDependencies) {
+    return DeallocatableResources::SILModule;
+  }
+
   // If there are multiple primary inputs it is too soon to free
   // the ASTContext, etc.. OTOH, if this compilation generates code for > 1
   // primary input, then freeing it after processing the last primary is