Index: llvm/utils/gn/secondary/lldb/source/Initialization/BUILD.gn
===================================================================
--- llvm/utils/gn/secondary/lldb/source/Initialization/BUILD.gn
+++ llvm/utils/gn/secondary/lldb/source/Initialization/BUILD.gn
@@ -8,10 +8,13 @@
 
     # XXX:
     # lldbPluginProcessPOSIX on linux/android
-    # lldbPluginProcessWindowsCommon on win
     "//llvm/lib/Support",
   ]
 
+  if (current_os == "win") {
+    deps += [ "//lldb/source/Plugins/Process/Windows/Common" ]
+  }
+
   # SystemInitializerCommon.cpp includes headers from Plugins/Process/....
   include_dirs = [ ".." ]
   sources = [
Index: llvm/utils/gn/secondary/lldb/source/Plugins/BUILD.gn
===================================================================
--- llvm/utils/gn/secondary/lldb/source/Plugins/BUILD.gn
+++ llvm/utils/gn/secondary/lldb/source/Plugins/BUILD.gn
@@ -40,6 +40,10 @@
     "//lldb/source/Plugins/DynamicLoader/Static",
     "DynamicLoaderStatic",
   ],
+  [
+    "//lldb/source/Plugins/DynamicLoader/Windows-DYLD",
+    "DynamicLoaderWindowsDYLD",
+  ],
   [
     "//lldb/source/Plugins/Instruction/ARM",
     "InstructionARM",
@@ -207,7 +211,7 @@
   # These are in separate variables to make sure ProcessWindowsCommon is
   # initalized after all plugins, but before ProcessGDBRemote.
   if (current_os == "win") {
-    values += [ "LLDB_PROCESS_WINDOWS_PLUGIN=LLDB_PLUGIN(XXX)" ]
+    values += [ "LLDB_PROCESS_WINDOWS_PLUGIN=LLDB_PLUGIN(ProcessWindowsCommon)" ]
   } else {
     values += [ "LLDB_PROCESS_WINDOWS_PLUGIN=" ]
   }
Index: llvm/utils/gn/secondary/lldb/source/Plugins/DynamicLoader/Windows-DYLD/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/lldb/source/Plugins/DynamicLoader/Windows-DYLD/BUILD.gn
@@ -0,0 +1,13 @@
+static_library("Windows-DYLD") {
+  output_name = "lldbPluginDynamicLoaderWindowsDYLD"
+  configs += [ "//llvm/utils/gn/build:lldb_code" ]
+  deps = [
+    "//lldb/source/Core",
+    "//lldb/source/Target",
+    "//llvm/lib/Support",
+  ]
+
+  # Uses source-relative includes for own headers.
+  include_dirs = [ "//lldb/source" ]
+  sources = [ "DynamicLoaderWindowsDYLD.cpp" ]
+}
Index: llvm/utils/gn/secondary/lldb/source/Plugins/ObjectFile/JIT/BUILD.gn
===================================================================
--- llvm/utils/gn/secondary/lldb/source/Plugins/ObjectFile/JIT/BUILD.gn
+++ llvm/utils/gn/secondary/lldb/source/Plugins/ObjectFile/JIT/BUILD.gn
@@ -9,5 +9,7 @@
     #"//lldb/source/Target", # 2-hop dependency cycle.
     "//llvm/lib/Support",
   ]
+  # For Utility/UuidCompatibility.h.
+  include_dirs = [ "//lldb/source" ]
   sources = [ "ObjectFileJIT.cpp" ]
 }
Index: llvm/utils/gn/secondary/lldb/source/Plugins/ObjectFile/Mach-O/BUILD.gn
===================================================================
--- llvm/utils/gn/secondary/lldb/source/Plugins/ObjectFile/Mach-O/BUILD.gn
+++ llvm/utils/gn/secondary/lldb/source/Plugins/ObjectFile/Mach-O/BUILD.gn
@@ -11,6 +11,10 @@
     "//llvm/lib/Support",
   ]
 
+  if (current_os == "win") {
+    defines = [ "_ENABLE_EXTENDED_ALIGNED_STORAGE" ]
+  }
+
   # Reaches into Plugins/Process/Utility.
   include_dirs = [ "//lldb/source" ]
   sources = [ "ObjectFileMachO.cpp" ]
Index: llvm/utils/gn/secondary/lldb/source/Plugins/ObjectFile/PECOFF/BUILD.gn
===================================================================
--- llvm/utils/gn/secondary/lldb/source/Plugins/ObjectFile/PECOFF/BUILD.gn
+++ llvm/utils/gn/secondary/lldb/source/Plugins/ObjectFile/PECOFF/BUILD.gn
@@ -20,6 +20,6 @@
 
   if (current_os == "win") {
     # Dbghelp is used on windows for writing minidump files.
-    libs = [ "dbghelp" ]
+    libs = [ "dbghelp.lib" ]
   }
 }
Index: llvm/utils/gn/secondary/lldb/source/Plugins/Process/Windows/Common/BUILD.gn
===================================================================
--- /dev/null
+++ llvm/utils/gn/secondary/lldb/source/Plugins/Process/Windows/Common/BUILD.gn
@@ -0,0 +1,48 @@
+static_library("Common") {
+  output_name = "lldbPluginProcessWindowsCommon"
+  configs += [ "//llvm/utils/gn/build:lldb_code" ]
+  deps = [
+    "//lldb/source/Core",
+    "//lldb/source/Host",
+    "//lldb/source/Interpreter",
+    "//lldb/source/Plugins/DynamicLoader/Windows-DYLD",
+    "//lldb/source/Symbol",
+    "//lldb/source/Target",
+    "//llvm/lib/Support",
+  ]
+  libs = [
+    "psapi.lib",
+    "rpcrt4.lib",
+    "ws2_32.lib",
+  ]
+
+  include_dirs = [
+    # ../Process/Windows/Common/x64/RegisterContextWindows_x64.h uses an
+    # unqualified include for "RegisterContextWindows.h".
+    ".",
+
+    # Reaches into Plugins/Process/Utility.
+    "//lldb/source",
+  ]
+  sources = [
+    "DebuggerThread.cpp",
+    "LocalDebugDelegate.cpp",
+    "NativeProcessWindows.cpp",
+    "NativeRegisterContextWindows.cpp",
+    "NativeRegisterContextWindows_WoW64.cpp",
+    "NativeRegisterContextWindows_arm.cpp",
+    "NativeRegisterContextWindows_arm64.cpp",
+    "NativeRegisterContextWindows_i386.cpp",
+    "NativeRegisterContextWindows_x86_64.cpp",
+    "NativeThreadWindows.cpp",
+    "ProcessDebugger.cpp",
+    "ProcessWindows.cpp",
+    "ProcessWindowsLog.cpp",
+    "RegisterContextWindows.cpp",
+    "TargetThreadWindows.cpp",
+    "arm/RegisterContextWindows_arm.cpp",
+    "arm64/RegisterContextWindows_arm64.cpp",
+    "x64/RegisterContextWindows_x64.cpp",
+    "x86/RegisterContextWindows_x86.cpp",
+  ]
+}
Index: llvm/utils/gn/secondary/lldb/source/Utility/BUILD.gn
===================================================================
--- llvm/utils/gn/secondary/lldb/source/Utility/BUILD.gn
+++ llvm/utils/gn/secondary/lldb/source/Utility/BUILD.gn
@@ -59,6 +59,13 @@
     "XcodeSDK.cpp",
   ]
 
+  if (current_os == "win") {
+    libs = [
+      "rpcrt4.lib",
+      "ws2_32.lib",
+    ]
+  }
+
   # FIXME:
   # if (APPLE)
   #   list(APPEND LLDB_SYSTEM_LIBS
@@ -75,10 +82,6 @@
   #
   # list(APPEND LLDB_SYSTEM_LIBS ${CMAKE_DL_LIBS})
   #
-  # if (CMAKE_SYSTEM_NAME MATCHES "Windows")
-  #   list(APPEND LLDB_SYSTEM_LIBS ws2_32 rpcrt4)
-  # endif ()
-  #
   # if (NOT HAVE_CXX_ATOMICS64_WITHOUT_LIB )
   #     list(APPEND LLDB_SYSTEM_LIBS atomic)
   # endif()