[clang] [Driver][SYCL][Windows] Add SYCL windows runtime library linking support for SYCL JIT compilations (PR #194744)

[Michael Toguchi via cfe-commits]

================
@@ -85,10 +85,62 @@ void visualstudio::Linker::ConstructJob(Compilation &C, const JobAction &JA,
       CmdArgs.push_back(Args.MakeArgString("--dependent-lib=amath"));
   }
 
+  // SYCL requires dynamic CRT because STL objects cross DLL boundaries.
+  // Library dependency is added via --dependent-lib at compiler stage.
+  // Here we validate CRT compatibility and add the library search path.
+  if (Args.hasFlag(options::OPT_fsycl, options::OPT_fno_sycl, false) &&
+      !Args.hasArg(options::OPT_nolibsycl) &&
+      !Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles)) {
+
+    // Check if static CRT is being used. Use getLastArg to handle overriding
+    // options (e.g., /MT /MD -> /MD wins).
+    bool HasStaticCRT = false;
+
+    if (const Arg *A = Args.getLastArg(options::OPT_fms_runtime_lib_EQ)) {
+      StringRef RuntimeLib = A->getValue();
+      if (RuntimeLib == "static" || RuntimeLib == "static_dbg")
+        HasStaticCRT = true;
+    }
+
+    if (const Arg *A = Args.getLastArg(options::OPT__SLASH_M_Group)) {
+      if (A->getOption().matches(options::OPT__SLASH_MT) ||
+          A->getOption().matches(options::OPT__SLASH_MTd))
+        HasStaticCRT = true;
+    }
+
+    if (HasStaticCRT) {
+      TC.getDriver().Diag(diag::err_drv_sycl_requires_dynamic_crt);
+    } else {
+      // Add library search path so linker can find LLVMSYCL[d].lib.
+      SmallString<128> LibPath(TC.getDriver().Dir);
+      llvm::sys::path::append(LibPath, "..", "lib");
+      CmdArgs.push_back(Args.MakeArgString(Twine("-libpath:") + LibPath));
+    }
+  }
+
   if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles) &&
       !C.getDriver().IsCLMode() && !C.getDriver().IsFlangMode()) {
     CmdArgs.push_back("-defaultlib:libcmt");
     CmdArgs.push_back("-defaultlib:oldnames");
+
+    // SYCL: Add runtime library for clang (non-clang-cl) with MSVC target.
+    // For clang-cl, --dependent-lib is used at compiler stage instead.
+    if (Args.hasFlag(options::OPT_fsycl, options::OPT_fno_sycl, false) &&
+        !Args.hasArg(options::OPT_nolibsycl)) {
+      bool IsDebugBuild = false;
+      if (const Arg *A = Args.getLastArg(options::OPT_fms_runtime_lib_EQ)) {
+        StringRef RuntimeVal = A->getValue();
+        if (RuntimeVal == "dll_dbg")
+          IsDebugBuild = true;
+      }
+      // Check for /MDd flag, use getLastArg to handle overriding options
+      if (const Arg *A = Args.getLastArg(options::OPT__SLASH_M_Group)) {
+        if (A->getOption().matches(options::OPT__SLASH_MDd))
+          IsDebugBuild = true;
+      }
----------------
mdtoguchi wrote:

The `/M*` options are only available when using `clang-cl`.  No need to add this check.

https://github.com/llvm/llvm-project/pull/194744