Driver: loosen restrictions for -force-autolink-symbol

On targets which support COMDAT (PE/COFF, ELF), use that to relax the
constraints on the emission of `-force-autolink-symbol` so that it is
possible to use that with `-incremental`.

Author: compnerd

lib/Driver/Driver.cpp

@@ -206,14 +206,18 @@ static void validateSearchPathArgs(DiagnosticEngine &diags,
 }
 
 static void validateAutolinkingArgs(DiagnosticEngine &diags,
-                                    const ArgList &args) {
+                                    const ArgList &args,
+                                    const llvm::Triple &T) {
   auto *forceLoadArg = args.getLastArg(options::OPT_autolink_force_load);
   if (!forceLoadArg)
     return;
   auto *incrementalArg = args.getLastArg(options::OPT_incremental);
   if (!incrementalArg)
     return;
 
+  if (T.supportsCOMDAT())
+    return;
+
   // Note: -incremental can itself be overridden by other arguments later
   // on, but since -autolink-force-load is a rare and not-really-recommended
   // option it's not worth modeling that complexity here (or moving the
@@ -223,14 +227,15 @@ static void validateAutolinkingArgs(DiagnosticEngine &diags,
 }
 
 /// Perform miscellaneous early validation of arguments.
-static void validateArgs(DiagnosticEngine &diags, const ArgList &args) {
+static void validateArgs(DiagnosticEngine &diags, const ArgList &args,
+                         const llvm::Triple &T) {
   validateBridgingHeaderArgs(diags, args);
   validateWarningControlArgs(diags, args);
   validateProfilingArgs(diags, args);
   validateDebugInfoArgs(diags, args);
   validateCompilationConditionArgs(diags, args);
   validateSearchPathArgs(diags, args);
-  validateAutolinkingArgs(diags, args);
+  validateAutolinkingArgs(diags, args, T);
 }
 
 std::unique_ptr<ToolChain>
@@ -783,7 +788,7 @@ Driver::buildCompilation(const ToolChain &TC,
   std::unique_ptr<DerivedArgList> TranslatedArgList(
       translateInputAndPathArgs(*ArgList, workingDirectory));
 
-  validateArgs(Diags, *TranslatedArgList);
+  validateArgs(Diags, *TranslatedArgList, TC.getTriple());
 
   // Perform toolchain specific args validation.
   TC.validateArguments(Diags, *TranslatedArgList);

lib/IRGen/IRGenModule.cpp

@@ -1184,14 +1184,17 @@ void IRGenModule::emitAutolinkInfo() {
   }
 
   if (!IRGen.Opts.ForceLoadSymbolName.empty() &&
-      isFirstObjectFileInModule(*this)) {
+      (Triple.supportsCOMDAT() || isFirstObjectFileInModule(*this))) {
     llvm::SmallString<64> buf;
     encodeForceLoadSymbolName(buf, IRGen.Opts.ForceLoadSymbolName);
     auto ForceImportThunk =
         llvm::Function::Create(llvm::FunctionType::get(VoidTy, false),
                                llvm::GlobalValue::ExternalLinkage, buf,
                                &Module);
     ApplyIRLinkage(IRLinkage::ExternalExport).to(ForceImportThunk);
+    if (Triple.supportsCOMDAT())
+      if (auto *GO = cast<llvm::GlobalObject>(ForceImportThunk))
+        GO->setComdat(Module.getOrInsertComdat(ForceImportThunk->getName()));
 
     auto BB = llvm::BasicBlock::Create(getLLVMContext(), "", ForceImportThunk);
     llvm::IRBuilder<> IRB(BB);

test/Driver/autolink-force-load-comdat.swift

@@ -0,0 +1,11 @@
+// RUN: %swiftc_driver -incremental -autolink-force-load %s 2>&1 | %FileCheck -check-prefix=AUTOLINK_FORCE_LOAD %s
+// RUN: %swiftc_driver -autolink-force-load -incremental %s 2>&1 | %FileCheck -check-prefix=AUTOLINK_FORCE_LOAD %s
+
+// MACHO targets do not support COMDAT
+// UNSUPPORTED: OS=macosx
+// UNSUPPORTED: OS=tvos
+// UNSUPPORTED: OS=watchos
+// UNSUPPORTED: OS=ios
+
+// AUTOLINK_FORCE_LOAD-NOT: error: '-autolink-force-load' is not supported with '-incremental'
+

test/Driver/autolink-force-load-no-comdat.swift

@@ -0,0 +1,8 @@
+// RUN: not %swiftc_driver -incremental -autolink-force-load %s 2>&1 | %FileCheck -check-prefix=AUTOLINK_FORCE_LOAD %s
+// RUN: not %swiftc_driver -autolink-force-load -incremental %s 2>&1 | %FileCheck -check-prefix=AUTOLINK_FORCE_LOAD %s
+
+// MACHO targets do not support COMDAT
+// REQUIRES-ANY: OS=macosx, OS=tvos, OS=watchos, OS=ios
+
+// AUTOLINK_FORCE_LOAD: error: '-autolink-force-load' is not supported with '-incremental'
+

test/Driver/options.swift

@@ -101,10 +101,6 @@
 // ASSUME_SINGLE_THREADED: swift
 // ASSUME_SINGLE_THREADED: -frontend {{.*}} -assume-single-threaded
 
-// RUN: not %swiftc_driver -incremental -autolink-force-load %s 2>&1 | %FileCheck -check-prefix=AUTOLINK_FORCE_LOAD %s
-// RUN: not %swiftc_driver -autolink-force-load -incremental %s 2>&1 | %FileCheck -check-prefix=AUTOLINK_FORCE_LOAD %s
-// AUTOLINK_FORCE_LOAD: error: '-autolink-force-load' is not supported with '-incremental'
-
 // RUN: %swift_driver -### -g -debug-info-format=codeview %s | %FileCheck -check-prefix DEBUG_INFO_FORMAT_CODEVIEW %s
 // RUN: %swift_driver -### -g -debug-info-format=dwarf %s | %FileCheck -check-prefix DEBUG_INFO_FORMAT_DWARF %s
 // RUN: %swiftc_driver -### -g -debug-info-format=codeview %s | %FileCheck -check-prefix DEBUG_INFO_FORMAT_CODEVIEW %s
@@ -132,4 +128,4 @@
 // RUN: %swiftc_driver -F %t/test.framework/ %s 2>&1 | %FileCheck -check-prefix SEARCH_PATH_INCLUDES_FRAMEWORK_EXTENSION %s
 // RUN: %swift_driver -Fsystem %t/test.framework/ %s 2>&1 | %FileCheck -check-prefix SEARCH_PATH_INCLUDES_FRAMEWORK_EXTENSION %s
 // RUN: %swiftc_driver -Fsystem %t/test.framework/ %s 2>&1 | %FileCheck -check-prefix SEARCH_PATH_INCLUDES_FRAMEWORK_EXTENSION %s
-// SEARCH_PATH_INCLUDES_FRAMEWORK_EXTENSION: warning: framework search path ends in ".framework"
+// SEARCH_PATH_INCLUDES_FRAMEWORK_EXTENSION: warning: framework search path ends in ".framework"