MSVC: support version preference with search

Extend the logic for the WinSDK and UCRT handling to prefer a user
specified version of the VisualC++ tools and Windows SDK. This allows
us to now perform the regular search for the installation but select the
exact version of the SDK or VC++ tools to override the latest version.
Similar to the other flags controlling this behaviour, if the user
specifies a value, we will not perform validation on the input and will
attempt to prefer that, particularly in the case of VisualC++ tools
where no fallback occurs.

Author: compnerd

clang/lib/Driver/ToolChains/MSVC.cpp

@@ -430,8 +430,8 @@ MSVCToolChain::MSVCToolChain(const Driver &D, const llvm::Triple &Triple,
                                       WinSysRoot, VCToolChainPath, VSLayout) ||
       llvm::findVCToolChainViaEnvironment(getVFS(), VCToolChainPath,
                                           VSLayout) ||
-      llvm::findVCToolChainViaSetupConfig(getVFS(), VCToolChainPath,
-                                          VSLayout) ||
+      llvm::findVCToolChainViaSetupConfig(getVFS(), VCToolsVersion,
+                                          VCToolChainPath, VSLayout) ||
       llvm::findVCToolChainViaRegistry(VCToolChainPath, VSLayout);
 }
 
@@ -536,6 +536,10 @@ bool MSVCToolChain::getWindowsSDKLibraryPath(const ArgList &Args,
 
   llvm::SmallString<128> libPath(sdkPath);
   llvm::sys::path::append(libPath, "Lib");
+  if (sdkMajor >= 10)
+    if (!(WinSdkDir.has_value() || WinSysRoot.has_value()) &&
+        WinSdkVersion.has_value())
+      windowsSDKLibVersion = *WinSdkVersion;
   if (sdkMajor >= 8)
     llvm::sys::path::append(libPath, windowsSDKLibVersion, "um");
   return llvm::appendArchToWindowsSDKLibPath(sdkMajor, libPath, getArch(),
@@ -557,6 +561,10 @@ bool MSVCToolChain::getUniversalCRTLibraryPath(const ArgList &Args,
                                    UCRTVersion))
     return false;
 
+  if (!(WinSdkDir.has_value() || WinSysRoot.has_value()) &&
+      WinSdkVersion.has_value())
+    UCRTVersion = *WinSdkVersion;
+
   StringRef ArchName = llvm::archToWindowsSDKArch(getArch());
   if (ArchName.empty())
     return false;
@@ -686,6 +694,9 @@ void MSVCToolChain::AddClangSystemIncludeArgs(const ArgList &DriverArgs,
       if (llvm::getUniversalCRTSdkDir(getVFS(), WinSdkDir, WinSdkVersion,
                                       WinSysRoot, UniversalCRTSdkPath,
                                       UCRTVersion)) {
+        if (!(WinSdkDir.has_value() || WinSysRoot.has_value()) &&
+            WinSdkVersion.has_value())
+          UCRTVersion = *WinSdkVersion;
         AddSystemIncludeWithSubfolder(DriverArgs, CC1Args, UniversalCRTSdkPath,
                                       "Include", UCRTVersion, "ucrt");
       }
@@ -698,6 +709,10 @@ void MSVCToolChain::AddClangSystemIncludeArgs(const ArgList &DriverArgs,
     if (llvm::getWindowsSDKDir(getVFS(), WinSdkDir, WinSdkVersion, WinSysRoot,
                                WindowsSDKDir, major, windowsSDKIncludeVersion,
                                windowsSDKLibVersion)) {
+      if (major >= 10)
+        if (!(WinSdkDir.has_value() || WinSysRoot.has_value()) &&
+            WinSdkVersion.has_value())
+          windowsSDKIncludeVersion = windowsSDKLibVersion = *WinSdkVersion;
       if (major >= 8) {
         // Note: windowsSDKIncludeVersion is empty for SDKs prior to v10.
         // Anyway, llvm::sys::path::append is able to manage it.

lld/COFF/Driver.cpp

@@ -560,7 +560,7 @@ void LinkerDriver::detectWinSysRoot(const opt::InputArgList &Args) {
                                      WinSysRoot, vcToolChainPath, vsLayout) &&
       (Args.hasArg(OPT_lldignoreenv) ||
        !findVCToolChainViaEnvironment(*VFS, vcToolChainPath, vsLayout)) &&
-      !findVCToolChainViaSetupConfig(*VFS, vcToolChainPath, vsLayout) &&
+      !findVCToolChainViaSetupConfig(*VFS, {}, vcToolChainPath, vsLayout) &&
       !findVCToolChainViaRegistry(vcToolChainPath, vsLayout))
     return;
 

llvm/include/llvm/WindowsDriver/MSVCPaths.h

@@ -91,11 +91,15 @@ bool findVCToolChainViaEnvironment(vfs::FileSystem &VFS, std::string &Path,
                                    ToolsetLayout &VSLayout);
 
 // Query the Setup Config server for installs, then pick the newest version
-// and find its default VC toolchain.
+// and find its default VC toolchain.  If `VCToolsVersion` is specified, that
+// version is preferred over the latest version.
+//
 // This is the preferred way to discover new Visual Studios, as they're no
 // longer listed in the registry.
-bool findVCToolChainViaSetupConfig(vfs::FileSystem &VFS, std::string &Path,
-                                   ToolsetLayout &VSLayout);
+bool
+findVCToolChainViaSetupConfig(vfs::FileSystem &VFS,
+                              llvm::Optional<llvm::StringRef> VCToolsVersion,
+                              std::string &Path, ToolsetLayout &VSLayout);
 
 // Look in the registry for Visual Studio installs, and use that to get
 // a toolchain path. VS2017 and newer don't get added to the registry.

llvm/lib/ExecutionEngine/Orc/COFFVCRuntimeSupport.cpp

@@ -160,7 +160,7 @@ COFFVCRuntimeBootstrapper::getMSVCToolchainPath() {
   if (!findVCToolChainViaCommandLine(*VFS, None, None, None, VCToolChainPath,
                                      VSLayout) &&
       !findVCToolChainViaEnvironment(*VFS, VCToolChainPath, VSLayout) &&
-      !findVCToolChainViaSetupConfig(*VFS, VCToolChainPath, VSLayout) &&
+      !findVCToolChainViaSetupConfig(*VFS, {}, VCToolChainPath, VSLayout) &&
       !findVCToolChainViaRegistry(VCToolChainPath, VSLayout))
     return make_error<StringError>("Couldn't find msvc toolchain.",
                                    inconvertibleErrorCode());

llvm/lib/WindowsDriver/MSVCPaths.cpp

@@ -608,8 +608,9 @@ bool findVCToolChainViaEnvironment(vfs::FileSystem &VFS, std::string &Path,
   return false;
 }
 
-bool findVCToolChainViaSetupConfig(vfs::FileSystem &VFS, std::string &Path,
-                                   ToolsetLayout &VSLayout) {
+bool findVCToolChainViaSetupConfig(vfs::FileSystem &VFS,
+                                   Optional<StringRef> VCToolsVersion,
+                                   std::string &Path, ToolsetLayout &VSLayout) {
 #if !defined(USE_MSVC_SETUP_API)
   return false;
 #else
@@ -676,17 +677,23 @@ bool findVCToolChainViaSetupConfig(vfs::FileSystem &VFS, std::string &Path,
   std::string VCRootPath;
   convertWideToUTF8(std::wstring(VCPathWide), VCRootPath);
 
-  SmallString<256> ToolsVersionFilePath(VCRootPath);
-  sys::path::append(ToolsVersionFilePath, "Auxiliary", "Build",
-                    "Microsoft.VCToolsVersion.default.txt");
+  std::string ToolsVersion;
+  if (VCToolsVersion.has_value()) {
+    ToolsVersion = *VCToolsVersion;
+  } else {
+    SmallString<256> ToolsVersionFilePath(VCRootPath);
+    sys::path::append(ToolsVersionFilePath, "Auxiliary", "Build",
+                      "Microsoft.VCToolsVersion.default.txt");
+
+    auto ToolsVersionFile = MemoryBuffer::getFile(ToolsVersionFilePath);
+    if (!ToolsVersionFile)
+      return false;
 
-  auto ToolsVersionFile = MemoryBuffer::getFile(ToolsVersionFilePath);
-  if (!ToolsVersionFile)
-    return false;
+    ToolsVersion = ToolsVersionFile->get()->getBuffer().rtrim();
+  }
 
   SmallString<256> ToolchainPath(VCRootPath);
-  sys::path::append(ToolchainPath, "Tools", "MSVC",
-                    ToolsVersionFile->get()->getBuffer().rtrim());
+  sys::path::append(ToolchainPath, "Tools", "MSVC", ToolsVersion);
   auto Status = VFS.status(ToolchainPath);
   if (!Status || !Status->isDirectory())
     return false;