4 files changed, 56 insertions, 6 deletions

diff --git a/clang/lib/Driver/MSVCToolChain.cpp b/clang/lib/Driver/MSVCToolChain.cpp
index acfb507fea5..4f38ec52f53 100644
--- a/clang/lib/Driver/MSVCToolChain.cpp
+++ b/clang/lib/Driver/MSVCToolChain.cpp
@@ -19,6 +19,7 @@
 #include "llvm/Config/llvm-config.h"
 #include "llvm/Option/Arg.h"
 #include "llvm/Option/ArgList.h"
+#include "llvm/Support/ConvertUTF.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Process.h"
@@ -37,6 +38,8 @@
     #define NOMINMAX
   #endif
   #include <windows.h>
+
+  #pragma comment(lib, "version.lib")
 #endif
 
 using namespace clang::driver;
@@ -457,6 +460,45 @@ bool MSVCToolChain::getVisualStudioBinariesFolder(const char *clangProgramPath,
   return true;
 }
 
+VersionTuple MSVCToolChain::getMSVCVersionFromExe() const {
+  VersionTuple Version;
+#ifdef USE_WIN32
+  std::string BinPath;
+  if (!getVisualStudioBinariesFolder("", BinPath))
+    return Version;
+  SmallString<128> ClExe = BinPath;
+  llvm::sys::path::append(ClExe, "cl.exe");
+
+  std::wstring ClExeWide;
+  if (!llvm::ConvertUTF8toWide(ClExe.c_str(), ClExeWide))
+    return Version;
+
+  const DWORD VersionSize = ::GetFileVersionInfoSizeW(ClExeWide.c_str(),
+                                                      nullptr);
+  if (VersionSize == 0)
+    return Version;
+
+  SmallVector<uint8_t, 4 * 1024> VersionBlock(VersionSize);
+  if (!::GetFileVersionInfoW(ClExeWide.c_str(), 0, VersionSize,
+                             VersionBlock.data()))
+    return Version;
+
+  VS_FIXEDFILEINFO *FileInfo = nullptr;
+  UINT FileInfoSize = 0;
+  if (!::VerQueryValueW(VersionBlock.data(), L"\\",
+                        reinterpret_cast<LPVOID *>(&FileInfo), &FileInfoSize) ||
+      FileInfoSize < sizeof(*FileInfo))
+    return Version;
+
+  const unsigned Major = (FileInfo->dwFileVersionMS >> 16) & 0xFFFF;
+  const unsigned Minor = (FileInfo->dwFileVersionMS      ) & 0xFFFF;
+  const unsigned Micro = (FileInfo->dwFileVersionLS >> 16) & 0xFFFF;
+
+  Version = VersionTuple(Major, Minor, Micro);
+#endif
+  return Version;
+}
+
 // Get Visual Studio installation directory.
 bool MSVCToolChain::getVisualStudioInstallDir(std::string &path) const {
   // First check the environment variables that vsvars32.bat sets.
@@ -618,7 +660,7 @@ MSVCToolChain::ComputeEffectiveClangTriple(const ArgList &Args,
       ToolChain::ComputeEffectiveClangTriple(Args, InputType);
   llvm::Triple Triple(TripleStr);
   VersionTuple MSVT =
-      tools::visualstudio::getMSVCVersion(/*D=*/nullptr, Triple, Args,
+      tools::visualstudio::getMSVCVersion(/*D=*/nullptr, *this, Triple, Args,
                                           /*IsWindowsMSVC=*/true);
   if (MSVT.empty())
     return TripleStr;
diff --git a/clang/lib/Driver/ToolChains.h b/clang/lib/Driver/ToolChains.h
index b8fe086380f..5e1e6ca2f22 100644
--- a/clang/lib/Driver/ToolChains.h
+++ b/clang/lib/Driver/ToolChains.h
@@ -1028,6 +1028,7 @@ public:
   bool getVisualStudioInstallDir(std::string &path) const;
   bool getVisualStudioBinariesFolder(const char *clangProgramPath,
                                      std::string &path) const;
+  VersionTuple getMSVCVersionFromExe() const override;
 
   std::string ComputeEffectiveClangTriple(const llvm::opt::ArgList &Args,
                                           types::ID InputType) const override;
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index cbc2e6575c5..c408e6c79e0 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -3293,7 +3293,7 @@ static void appendUserToPath(SmallVectorImpl<char> &Result) {
   Result.append(UID.begin(), UID.end());
 }
 
-VersionTuple visualstudio::getMSVCVersion(const Driver *D,
+VersionTuple visualstudio::getMSVCVersion(const Driver *D, const ToolChain &TC,
                                           const llvm::Triple &Triple,
                                           const llvm::opt::ArgList &Args,
                                           bool IsWindowsMSVC) {
@@ -3335,8 +3335,14 @@ VersionTuple visualstudio::getMSVCVersion(const Driver *D,
     if (Major || Minor || Micro)
       return VersionTuple(Major, Minor, Micro);
 
-    // FIXME: Consider bumping this to 19 (MSVC2015) soon.
-    return VersionTuple(18);
+    if (IsWindowsMSVC) {
+      VersionTuple MSVT = TC.getMSVCVersionFromExe();
+      if (!MSVT.empty())
+        return MSVT;
+
+      // FIXME: Consider bumping this to 19 (MSVC2015) soon.
+      return VersionTuple(18);
+    }
   }
   return VersionTuple();
 }
@@ -5226,7 +5232,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
 
   // -fms-compatibility-version=18.00 is default.
   VersionTuple MSVT = visualstudio::getMSVCVersion(
-      &D, getToolChain().getTriple(), Args, IsWindowsMSVC);
+      &D, getToolChain(), getToolChain().getTriple(), Args, IsWindowsMSVC);
   if (!MSVT.empty())
     CmdArgs.push_back(
         Args.MakeArgString("-fms-compatibility-version=" + MSVT.getAsString()));
diff --git a/clang/lib/Driver/Tools.h b/clang/lib/Driver/Tools.h
index c9d5c2238d6..723b1dcfa9b 100644
--- a/clang/lib/Driver/Tools.h
+++ b/clang/lib/Driver/Tools.h
@@ -682,7 +682,8 @@ public:
 
 /// Visual studio tools.
 namespace visualstudio {
-VersionTuple getMSVCVersion(const Driver *D, const llvm::Triple &Triple,
+VersionTuple getMSVCVersion(const Driver *D, const ToolChain &TC,
+                            const llvm::Triple &Triple,
                             const llvm::opt::ArgList &Args, bool IsWindowsMSVC);
 
 class LLVM_LIBRARY_VISIBILITY Linker : public Tool {