[Driver][SYCL] Cleanup Windows defaultlib linking behaviors (#7856)

Changes from the community has caused a section of duplicate code when
dealing with adding the required default libraries for Windows linking.
This is causing a doubling up of the predefined macros (_MT, _DLL and
_DEBUG) as well as multiple inclusions of the MSVC runtime libs. The
duplication of the runtime libs is also causing a warning to be emitted
from the linker due to 2 different variants of the library being linked
in when -fsycl compilations are enabled.

Cleanup this portion of code, moving the SYCL specific additions to the
new function.

Author: mdtoguchi

clang/lib/Driver/ToolChains/Clang.cpp

@@ -4676,13 +4676,22 @@ static void ProcessVSRuntimeLibrary(const ArgList &Args,
                                     const ToolChain &TC) {
   unsigned RTOptionID = options::OPT__SLASH_MT;
 
+  bool isSPIR = TC.getTriple().isSPIR();
+  bool isSYCL = Args.hasArg(options::OPT_fsycl);
+  // For SYCL Windows, /MD is the default.
+  if (isSYCL)
+    RTOptionID = options::OPT__SLASH_MD;
+
   if (Args.hasArg(options::OPT__SLASH_LDd))
-    // The /LDd option implies /MTd. The dependent lib part can be overridden,
-    // but defining _DEBUG is sticky.
-    RTOptionID = options::OPT__SLASH_MTd;
+    // The /LDd option implies /MTd (/MDd for SYCL). The dependent lib part
+    // can be overridden, but defining _DEBUG is sticky.
+    RTOptionID = isSYCL ? options::OPT__SLASH_MDd : options::OPT__SLASH_MTd;
 
-  if (Arg *A = Args.getLastArg(options::OPT__SLASH_M_Group))
+  Arg *SetArg = nullptr;
+  if (Arg *A = Args.getLastArg(options::OPT__SLASH_M_Group)) {
     RTOptionID = A->getOption().getID();
+    SetArg = A;
+  }
 
   if (Arg *A = Args.getLastArg(options::OPT_fms_runtime_lib_EQ)) {
     RTOptionID = llvm::StringSwitch<unsigned>(A->getValue())
@@ -4691,40 +4700,43 @@ static void ProcessVSRuntimeLibrary(const ArgList &Args,
                      .Case("dll", options::OPT__SLASH_MD)
                      .Case("dll_dbg", options::OPT__SLASH_MDd)
                      .Default(options::OPT__SLASH_MT);
+    SetArg = A;
   }
+  if (isSYCL && !isSPIR && SetArg &&
+      (RTOptionID == options::OPT__SLASH_MT ||
+       RTOptionID == options::OPT__SLASH_MTd))
+      // Use of /MT or /MTd is not supported for SYCL.
+    TC.getDriver().Diag(diag::err_drv_unsupported_opt_dpcpp)
+        << SetArg->getOption().getName();
 
-  bool isSPIR = TC.getTriple().isSPIR();
-  StringRef FlagForCRT;
-  switch (RTOptionID) {
-  case options::OPT__SLASH_MD:
-    if (Args.hasArg(options::OPT__SLASH_LDd))
+  enum { addDEBUG = 0x1, addMT = 0x2, addDLL = 0x4 };
+  auto addPreDefines = [&](unsigned Defines) {
+    if (Defines & addDEBUG)
       CmdArgs.push_back("-D_DEBUG");
-    if (!isSPIR) {
+    if (Defines & addMT && !isSPIR)
       CmdArgs.push_back("-D_MT");
+    if (Defines & addDLL && !isSPIR)
       CmdArgs.push_back("-D_DLL");
-    }
+  };
+  StringRef FlagForCRT;
+  switch (RTOptionID) {
+  case options::OPT__SLASH_MD:
+    addPreDefines((Args.hasArg(options::OPT__SLASH_LDd) ? addDEBUG : 0x0) |
+                  addMT | addDLL);
     FlagForCRT = "--dependent-lib=msvcrt";
     break;
   case options::OPT__SLASH_MDd:
-    CmdArgs.push_back("-D_DEBUG");
-    if (!isSPIR) {
-      CmdArgs.push_back("-D_MT");
-      CmdArgs.push_back("-D_DLL");
-    }
+    addPreDefines(addDEBUG | addMT | addDLL);
     FlagForCRT = "--dependent-lib=msvcrtd";
     break;
   case options::OPT__SLASH_MT:
-    if (Args.hasArg(options::OPT__SLASH_LDd))
-      CmdArgs.push_back("-D_DEBUG");
-    if (!isSPIR)
-      CmdArgs.push_back("-D_MT");
+    addPreDefines((Args.hasArg(options::OPT__SLASH_LDd) ? addDEBUG : 0x0) |
+                  addMT);
     CmdArgs.push_back("-flto-visibility-public-std");
     FlagForCRT = "--dependent-lib=libcmt";
     break;
   case options::OPT__SLASH_MTd:
-    CmdArgs.push_back("-D_DEBUG");
-    if (!isSPIR)
-      CmdArgs.push_back("-D_MT");
+    addPreDefines(addDEBUG | addMT);
     CmdArgs.push_back("-flto-visibility-public-std");
     FlagForCRT = "--dependent-lib=libcmtd";
     break;
@@ -4741,6 +4753,15 @@ static void ProcessVSRuntimeLibrary(const ArgList &Args,
     // users want.  The /Za flag to cl.exe turns this off, but it's not
     // implemented in clang.
     CmdArgs.push_back("--dependent-lib=oldnames");
+    // Add SYCL dependent library
+    if (Args.hasArg(options::OPT_fsycl) &&
+        !Args.hasArg(options::OPT_nolibsycl)) {
+      if (RTOptionID == options::OPT__SLASH_MDd)
+        CmdArgs.push_back("--dependent-lib=sycl" SYCL_MAJOR_VERSION "d");
+      else
+        CmdArgs.push_back("--dependent-lib=sycl" SYCL_MAJOR_VERSION);
+      CmdArgs.push_back("--dependent-lib=sycl-devicelib-host");
+    }
   }
 }
 
@@ -8165,85 +8186,8 @@ void Clang::AddClangCLArgs(const ArgList &Args, types::ID InputType,
                            ArgStringList &CmdArgs,
                            codegenoptions::DebugInfoKind *DebugInfoKind,
                            bool *EmitCodeView) const {
-  unsigned RTOptionID = options::OPT__SLASH_MT;
   bool isNVPTX = getToolChain().getTriple().isNVPTX();
-  bool isSPIR = getToolChain().getTriple().isSPIR();
-  // FIXME: isSYCL should not be enabled by "isSPIR"
-  bool isSYCL = Args.hasArg(options::OPT_fsycl) || isSPIR;
-  // For SYCL Windows, /MD is the default.
-  if (isSYCL)
-    RTOptionID = options::OPT__SLASH_MD;
-
-  if (Args.hasArg(options::OPT__SLASH_LDd))
-    // The /LDd option implies /MTd (/MDd for SYCL). The dependent lib part
-    // can be overridden but defining _DEBUG is sticky.
-    RTOptionID = isSYCL ? options::OPT__SLASH_MDd : options::OPT__SLASH_MTd;
-
-  if (Arg *A = Args.getLastArg(options::OPT__SLASH_M_Group)) {
-    RTOptionID = A->getOption().getID();
-    if (isSYCL && !isSPIR &&
-        (RTOptionID == options::OPT__SLASH_MT ||
-         RTOptionID == options::OPT__SLASH_MTd))
-      // Use of /MT or /MTd is not supported for SYCL.
-      getToolChain().getDriver().Diag(diag::err_drv_unsupported_opt_dpcpp)
-          << A->getOption().getName();
-  }
-
-  enum { addDEBUG = 0x1, addMT = 0x2, addDLL = 0x4 };
-  auto addPreDefines = [&](unsigned Defines) {
-    if (Defines & addDEBUG)
-      CmdArgs.push_back("-D_DEBUG");
-    if (Defines & addMT && !isSPIR)
-      CmdArgs.push_back("-D_MT");
-    if (Defines & addDLL && !isSPIR)
-      CmdArgs.push_back("-D_DLL");
-  };
-  StringRef FlagForCRT;
-  switch (RTOptionID) {
-  case options::OPT__SLASH_MD:
-    addPreDefines((Args.hasArg(options::OPT__SLASH_LDd) ? addDEBUG : 0x0) |
-                  addMT | addDLL);
-    FlagForCRT = "--dependent-lib=msvcrt";
-    break;
-  case options::OPT__SLASH_MDd:
-    addPreDefines(addDEBUG | addMT | addDLL);
-    FlagForCRT = "--dependent-lib=msvcrtd";
-    break;
-  case options::OPT__SLASH_MT:
-    addPreDefines((Args.hasArg(options::OPT__SLASH_LDd) ? addDEBUG : 0x0) |
-                  addMT);
-    CmdArgs.push_back("-flto-visibility-public-std");
-    FlagForCRT = "--dependent-lib=libcmt";
-    break;
-  case options::OPT__SLASH_MTd:
-    addPreDefines(addDEBUG | addMT);
-    CmdArgs.push_back("-flto-visibility-public-std");
-    FlagForCRT = "--dependent-lib=libcmtd";
-    break;
-  default:
-    llvm_unreachable("Unexpected option ID.");
-  }
-
-  if (Args.hasArg(options::OPT__SLASH_Zl)) {
-    CmdArgs.push_back("-D_VC_NODEFAULTLIB");
-  } else {
-    CmdArgs.push_back(FlagForCRT.data());
-
-    // This provides POSIX compatibility (maps 'open' to '_open'), which most
-    // users want.  The /Za flag to cl.exe turns this off, but it's not
-    // implemented in clang.
-    CmdArgs.push_back("--dependent-lib=oldnames");
 
-    // Add SYCL dependent library
-    if (Args.hasArg(options::OPT_fsycl) &&
-        !Args.hasArg(options::OPT_nolibsycl)) {
-      if (RTOptionID == options::OPT__SLASH_MDd)
-        CmdArgs.push_back("--dependent-lib=sycl" SYCL_MAJOR_VERSION "d");
-      else
-        CmdArgs.push_back("--dependent-lib=sycl" SYCL_MAJOR_VERSION);
-      CmdArgs.push_back("--dependent-lib=sycl-devicelib-host");
-    }
-  }
   ProcessVSRuntimeLibrary(Args, CmdArgs, getToolChain());
 
   if (Arg *ShowIncludes =