[Autolink] Autolinking on COFF for Cygwin/MinGW

Cygwin and MinGW should use the autolink feature in the sameway of Linux
due to the linker's limit. Now swift-autolink-extract recognizes the
COFF format file for Cygwin/MinGW.

docs/Testing.rst

@@ -273,7 +273,7 @@ code for the target that is not the build machine:
   ``armv7``, ``armv7k``, ``arm64``).
 
 * ``%target-os``: the target operating system (``macosx``, ``darwin``,
-  ``linux``, ``freebsd``).
+  ``linux``, ``freebsd``, ``windows-cygnus``, ``windows-gnu``).
 
 * ``%target-object-format``: the platform's object format (``elf``, ``macho``,
   ``coff``).

lib/Driver/Driver.cpp

@@ -1316,7 +1316,8 @@ void Driver::buildActions(const ToolChain &TC,
   if (OI.shouldLink() && !AllLinkerInputs.empty()) {
     auto *LinkAction = new LinkJobAction(AllLinkerInputs, OI.LinkAction);
 
-    if (TC.getTriple().getObjectFormat() == llvm::Triple::ELF) {
+    if (TC.getTriple().getObjectFormat() == llvm::Triple::ELF ||
+        TC.getTriple().isOSCygMing()) {
       // On ELF platforms there's no built in autolinking mechanism, so we
       // pull the info we need from the .o files directly and pass them as an
       // argument input file to the linker.

test/AutolinkExtract/empty.swift

@@ -4,3 +4,4 @@
 // REQUIRES: autolink-extract
 
 // CHECK-elf: -lswiftCore
+// CHECK-coff: -lswiftCore

test/AutolinkExtract/empty_archive.swift

@@ -6,3 +6,4 @@
 // REQUIRES: autolink-extract
 
 // CHECK-elf: -lswiftCore
+// CHECK-coff: -lswiftCore

test/AutolinkExtract/import.swift

@@ -9,4 +9,7 @@
 // CHECK-elf-DAG: -lswiftCore
 // CHECK-elf-DAG: -lempty
 
+// CHECK-coff-DAG: -lswiftCore
+// CHECK-coff-DAG: -lempty
+
 import empty

test/AutolinkExtract/import_archive.swift

@@ -10,4 +10,7 @@
 // CHECK-elf-DAG: -lswiftCore
 // CHECK-elf-DAG: -lempty
 
+// CHECK-coff-DAG: -lswiftCore
+// CHECK-coff-DAG: -lempty
+
 import empty

test/AutolinkExtract/linker-order.ll

@@ -1,4 +1,6 @@
 ; RUN: llc -mtriple armv7--linux-gnueabihf -filetype obj -o - %s | %target-swift-autolink-extract -o - - | FileCheck %s
+; RUN: llc -mtriple x86_64--windows-gnu -filetype obj -o - %s | %target-swift-autolink-extract -o - - | FileCheck %s
+; RUN: llc -mtriple x86_64--windows-cygnus -filetype obj -o - %s | %target-swift-autolink-extract -o - - | FileCheck %s
 ; REQUIRES: autolink-extract
 
 ; Ensure that the options in the object file preserve ordering.  The linker

test/lit.cfg

@@ -691,17 +691,30 @@ if run_vendor == 'apple':
         "%s clang++ %s" %
         (xcrun_prefix, config.target_cc_options))
 
-elif run_os == 'linux-gnu' or run_os == 'linux-gnueabihf' or run_os == 'freebsd':
-    # Linux/FreeBSD
-    if run_os == 'freebsd':
+elif run_os in ['linux-gnu', 'linux-gnueabihf', 'freebsd', 'windows-cygnus', 'windows-gnu']:
+    # Linux/FreeBSD/Cygwin
+    if run_os == 'windows-cygnus':
+      lit_config.note("Testing Cygwin " + config.variant_triple)
+      config.target_object_format = "coff"
+      config.target_dylib_extension = "dll"
+      config.target_sdk_name = "cygwin"
+    elif run_os == 'windows-gnu':
+      lit_config.note("Testing MinGW " + config.variant_triple)
+      config.target_object_format = "coff"
+      config.target_dylib_extension = "dll"
+      config.target_sdk_name = "mingw"
+    elif run_os == 'freebsd':
       lit_config.note("Testing FreeBSD " + config.variant_triple)
+      config.target_object_format = "elf"
+      config.target_dylib_extension = "so"
+      config.target_sdk_name = "freebsd"
     else:
       lit_config.note("Testing Linux " + config.variant_triple)
-    config.target_object_format = "elf"
-    config.target_dylib_extension = "so"
+      config.target_object_format = "elf"
+      config.target_dylib_extension = "so"
+      config.target_sdk_name = "linux"
     config.target_runtime = "native"
     config.target_swift_autolink_extract = inferSwiftBinary("swift-autolink-extract")
-    config.target_sdk_name = "freebsd" if run_os == "freebsd" else "linux"
     config.target_build_swift = (
         '%s -target %s %s %s %s %s'
         % (config.swiftc, config.variant_triple, resource_dir_opt, mcp_opt,

tools/driver/autolink_extract_main.cpp

@@ -31,6 +31,7 @@
 #include "llvm/Option/Option.h"
 #include "llvm/Object/Archive.h"
 #include "llvm/Object/ObjectFile.h"
+#include "llvm/Object/COFF.h"
 #include "llvm/Object/ELFObjectFile.h"
 
 using namespace swift;
@@ -106,32 +107,44 @@ public:
   }
 };
 
-// Look inside the binary 'Bin' and append any linker flags found in its
-// ".swift1_autolink_entries" section to 'LinkerFlags'. If 'Bin' is an archive,
-// recursively look inside all children within the archive. Return 'true' if
-// there was an error, and 'false' otherwise.
+/// Look inside the object file 'ObjectFile' and append any linker flags found in
+/// its ".swift1_autolink_entries" section to 'LinkerFlags'.
+static void
+extractLinkerFlagsFromObjectFile(const llvm::object::ObjectFile *ObjectFile,
+                                 std::vector<std::string> &LinkerFlags) {
+  // Search for the section we hold autolink entries in
+  for (auto &Section : ObjectFile->sections()) {
+    llvm::StringRef SectionName;
+    Section.getName(SectionName);
+    if (SectionName == ".swift1_autolink_entries") {
+      llvm::StringRef SectionData;
+      Section.getContents(SectionData);
+
+      // entries are null-terminated, so extract them and push them into
+      // the set.
+      llvm::SmallVector<llvm::StringRef, 4> SplitFlags;
+      SectionData.split(SplitFlags, llvm::StringRef("\0", 1), -1,
+                        /*KeepEmpty=*/false);
+      for (const auto &Flag : SplitFlags)
+        LinkerFlags.push_back(Flag);
+    }
+  }
+}
+
+/// Look inside the binary 'Bin' and append any linker flags found in its
+/// ".swift1_autolink_entries" section to 'LinkerFlags'. If 'Bin' is an archive,
+/// recursively look inside all children within the archive. Return 'true' if
+/// there was an error, and 'false' otherwise.
 static bool extractLinkerFlags(const llvm::object::Binary *Bin,
                                CompilerInstance &Instance,
                                StringRef BinaryFileName,
                                std::vector<std::string> &LinkerFlags) {
   if (auto *ObjectFile = llvm::dyn_cast<llvm::object::ELFObjectFileBase>(Bin)) {
-    // Search for the section we hold autolink entries in
-    for (auto &Section : ObjectFile->sections()) {
-      llvm::StringRef SectionName;
-      Section.getName(SectionName);
-      if (SectionName == ".swift1_autolink_entries") {
-        llvm::StringRef SectionData;
-        Section.getContents(SectionData);
-
-        // entries are null-terminated, so extract them and push them into
-        // the set.
-        llvm::SmallVector<llvm::StringRef, 4> SplitFlags;
-        SectionData.split(SplitFlags, llvm::StringRef("\0", 1), -1,
-                          /*KeepEmpty=*/false);
-        for (const auto &Flag : SplitFlags)
-          LinkerFlags.push_back(Flag);
-      }
-    }
+    extractLinkerFlagsFromObjectFile(ObjectFile, LinkerFlags);
+    return false;
+  } else if (auto *ObjectFile =
+                 llvm::dyn_cast<llvm::object::COFFObjectFile>(Bin)) {
+    extractLinkerFlagsFromObjectFile(ObjectFile, LinkerFlags);
     return false;
   } else if (auto *Archive = llvm::dyn_cast<llvm::object::Archive>(Bin)) {
     for (const auto &Child : Archive->children()) {