Serialization: serialize if the module is a static library

If the `-static` option is specified, store that in the generated
swiftmodule file.  When de-serializing, recover this information in the
representative SILModule.

This will be used for code generation on Windows.  It is the missing
piece to allow static linking to function properly.  It additionally
opens the path to additional optimization on ELF-ish targets - GOT, PLT
references can be avoided when the linked module is known to be static.

Co-authored by: Saleem Abdulrasool <compnerd@compnerd.org>

Author: eeckstein

include/swift/AST/Decl.h

@@ -588,7 +588,10 @@ class alignas(1 << DeclAlignInBits) Decl {
     HasAnyUnavailableValues : 1
   );
 
-  SWIFT_INLINE_BITFIELD(ModuleDecl, TypeDecl, 1+1+1+1+1+1+1+1+1+1,
+  SWIFT_INLINE_BITFIELD(ModuleDecl, TypeDecl, 1+1+1+1+1+1+1+1+1+1+1,
+    /// If the module is compiled as static library.
+    StaticLibrary : 1,
+
     /// If the module was or is being compiled with `-enable-testing`.
     TestingEnabled : 1,
 

include/swift/AST/Module.h

@@ -424,6 +424,14 @@ class ModuleDecl : public DeclContext, public TypeDecl {
     DebugClient = R;
   }
 
+  /// Returns true if this module is compiled as static library.
+  bool isStaticLibrary() const {
+    return Bits.ModuleDecl.StaticLibrary;
+  }
+  void setStaticLibrary(bool isStatic = true) {
+    Bits.ModuleDecl.StaticLibrary = isStatic;
+  }
+
   /// Returns true if this module was or is being compiled for testing.
   bool isTestingEnabled() const {
     return Bits.ModuleDecl.TestingEnabled;

include/swift/Frontend/FrontendOptions.h

@@ -314,6 +314,9 @@ class FrontendOptions {
   /// skip nodes entirely, depending on the errors involved.
   bool AllowModuleWithCompilerErrors = false;
 
+  /// True if the "-static" option is set.
+  bool Static = 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/Serialization/SerializationOptions.h

@@ -136,6 +136,7 @@ namespace swift {
     bool SerializeOptionsForDebugging = false;
     bool IsSIB = false;
     bool DisableCrossModuleIncrementalInfo = false;
+    bool StaticLibrary = false;
   };
 
 } // end namespace swift

include/swift/Serialization/Validation.h

@@ -98,6 +98,7 @@ class ExtendedValidationInfo {
   struct {
     unsigned ArePrivateImportsEnabled : 1;
     unsigned IsSIB : 1;
+    unsigned IsStaticLibrary: 1;
     unsigned IsTestable : 1;
     unsigned ResilienceStrategy : 2;
     unsigned IsImplicitDynamicEnabled : 1;
@@ -131,6 +132,10 @@ class ExtendedValidationInfo {
   void setImplicitDynamicEnabled(bool val) {
     Bits.IsImplicitDynamicEnabled = val;
   }
+  bool isStaticLibrary() const { return Bits.IsStaticLibrary; }
+  void setIsStaticLibrary(bool val) {
+    Bits.IsStaticLibrary = val;
+  }
   bool isTestable() const { return Bits.IsTestable; }
   void setIsTestable(bool val) {
     Bits.IsTestable = val;

lib/AST/Module.cpp

@@ -475,6 +475,7 @@ ModuleDecl::ModuleDecl(Identifier name, ASTContext &ctx,
 
   setAccess(AccessLevel::Public);
 
+  Bits.ModuleDecl.StaticLibrary = 0;
   Bits.ModuleDecl.TestingEnabled = 0;
   Bits.ModuleDecl.FailedToLoad = 0;
   Bits.ModuleDecl.RawResilienceStrategy = 0;

lib/Frontend/ArgsToFrontendOptionsConverter.cpp

@@ -258,6 +258,8 @@ bool ArgsToFrontendOptionsConverter::convert(
 
   Opts.SkipInheritedDocs = Args.hasArg(OPT_skip_inherited_docs);
 
+  Opts.Static = Args.hasArg(OPT_static);
+
   return false;
 }
 

lib/Frontend/Frontend.cpp

@@ -182,6 +182,8 @@ SerializationOptions CompilerInvocation::computeSerializationOptions(
   serializationOpts.DisableCrossModuleIncrementalInfo =
       opts.DisableCrossModuleIncrementalBuild;
 
+  serializationOpts.StaticLibrary = opts.Static;
+
   return serializationOpts;
 }
 

lib/Serialization/ModuleFile.h

@@ -461,6 +461,11 @@ class ModuleFile
     return Core->Bits.IsTestable;
   }
 
+  /// Whether this module is compiled as static library.
+  bool isStaticLibrary() const {
+    return Core->Bits.IsStaticLibrary;
+  }
+
   /// Whether the module is resilient. ('-enable-library-evolution')
   ResilienceStrategy getResilienceStrategy() const {
     return ResilienceStrategy(Core->Bits.ResilienceStrategy);

lib/Serialization/ModuleFileSharedCore.cpp

@@ -131,6 +131,9 @@ static bool readOptionsBlock(llvm::BitstreamCursor &cursor,
       options_block::IsSIBLayout::readRecord(scratch, IsSIB);
       extendedInfo.setIsSIB(IsSIB);
       break;
+    case options_block::IS_STATIC_LIBRARY:
+      extendedInfo.setIsStaticLibrary(true);
+      break;
     case options_block::IS_TESTABLE:
       extendedInfo.setIsTestable(true);
       break;
@@ -1180,6 +1183,7 @@ ModuleFileSharedCore::ModuleFileSharedCore(
       UserModuleVersion = info.userModuleVersion;
       Bits.ArePrivateImportsEnabled = extInfo.arePrivateImportsEnabled();
       Bits.IsSIB = extInfo.isSIB();
+      Bits.IsStaticLibrary = extInfo.isStaticLibrary();
       Bits.IsTestable = extInfo.isTestable();
       Bits.ResilienceStrategy = unsigned(extInfo.getResilienceStrategy());
       Bits.IsImplicitDynamicEnabled = extInfo.isImplicitDynamicEnabled();