[clang] [clang] Support --sysroot= for ${arch}-windows-msvc targets (PR #96417)

[via cfe-commits]

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@@ -95,43 +95,52 @@ void visualstudio::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   // the environment variable is set however, assume the user knows what
   // they're doing. If the user passes /vctoolsdir or /winsdkdir, trust that
   // over env vars.
-  if (const Arg *A = Args.getLastArg(options::OPT__SLASH_diasdkdir,
-                                     options::OPT__SLASH_winsysroot)) {
-    // cl.exe doesn't find the DIA SDK automatically, so this too requires
-    // explicit flags and doesn't automatically look in "DIA SDK" relative
-    // to the path we found for VCToolChainPath.
-    llvm::SmallString<128> DIAPath(A->getValue());
-    if (A->getOption().getID() == options::OPT__SLASH_winsysroot)
-      llvm::sys::path::append(DIAPath, "DIA SDK");
-
-    // The DIA SDK always uses the legacy vc arch, even in new MSVC versions.
-    llvm::sys::path::append(DIAPath, "lib",
-                            llvm::archToLegacyVCArch(TC.getArch()));
-    CmdArgs.push_back(Args.MakeArgString(Twine("-libpath:") + DIAPath));
-  }
-  if (!llvm::sys::Process::GetEnv("LIB") ||
-      Args.getLastArg(options::OPT__SLASH_vctoolsdir,
-                      options::OPT__SLASH_winsysroot)) {
-    CmdArgs.push_back(Args.MakeArgString(
-        Twine("-libpath:") +
-        TC.getSubDirectoryPath(llvm::SubDirectoryType::Lib)));
-    CmdArgs.push_back(Args.MakeArgString(
-        Twine("-libpath:") +
-        TC.getSubDirectoryPath(llvm::SubDirectoryType::Lib, "atlmfc")));
-  }
-  if (!llvm::sys::Process::GetEnv("LIB") ||
-      Args.getLastArg(options::OPT__SLASH_winsdkdir,
-                      options::OPT__SLASH_winsysroot)) {
-    if (TC.useUniversalCRT()) {
-      std::string UniversalCRTLibPath;
-      if (TC.getUniversalCRTLibraryPath(Args, UniversalCRTLibPath))
+  auto SysRoot = TC.getDriver().SysRoot;
+  if (SysRoot.empty()) {
+    if (const Arg *A = Args.getLastArg(options::OPT__SLASH_diasdkdir,
+                                       options::OPT__SLASH_winsysroot)) {
+      // cl.exe doesn't find the DIA SDK automatically, so this too requires
+      // explicit flags and doesn't automatically look in "DIA SDK" relative
+      // to the path we found for VCToolChainPath.
+      llvm::SmallString<128> DIAPath(A->getValue());
+      if (A->getOption().getID() == options::OPT__SLASH_winsysroot)
+        llvm::sys::path::append(DIAPath, "DIA SDK");
+
+      // The DIA SDK always uses the legacy vc arch, even in new MSVC versions.
+      llvm::sys::path::append(DIAPath, "lib",
+                              llvm::archToLegacyVCArch(TC.getArch()));
+      CmdArgs.push_back(Args.MakeArgString(Twine("-libpath:") + DIAPath));
+    }
+    if (!llvm::sys::Process::GetEnv("LIB") ||
+        Args.getLastArg(options::OPT__SLASH_vctoolsdir,
+                        options::OPT__SLASH_winsysroot)) {
+      CmdArgs.push_back(Args.MakeArgString(
+          Twine("-libpath:") +
+          TC.getSubDirectoryPath(llvm::SubDirectoryType::Lib)));
+      CmdArgs.push_back(Args.MakeArgString(
+          Twine("-libpath:") +
+          TC.getSubDirectoryPath(llvm::SubDirectoryType::Lib, "atlmfc")));
+    }
+    if (!llvm::sys::Process::GetEnv("LIB") ||
+        Args.getLastArg(options::OPT__SLASH_winsdkdir,
+                        options::OPT__SLASH_winsysroot)) {
+      if (TC.useUniversalCRT()) {
+        std::string UniversalCRTLibPath;
+        if (TC.getUniversalCRTLibraryPath(Args, UniversalCRTLibPath))
+          CmdArgs.push_back(
+              Args.MakeArgString(Twine("-libpath:") + UniversalCRTLibPath));
+      }
+      std::string WindowsSdkLibPath;
+      if (TC.getWindowsSDKLibraryPath(Args, WindowsSdkLibPath))
         CmdArgs.push_back(
-            Args.MakeArgString(Twine("-libpath:") + UniversalCRTLibPath));
+            Args.MakeArgString(std::string("-libpath:") + WindowsSdkLibPath));
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zmodem wrote:

Might as well use Twine while we're here.

https://github.com/llvm/llvm-project/pull/96417