[clang] [llvm] [Driver][SYCL] Add initial SYCL offload compilation support (PR #107493)

[Michael Toguchi via llvm-commits]

================
@@ -5116,15 +5123,39 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   if (const Arg *PF = Args.getLastArg(options::OPT_mprintf_kind_EQ))
     PF->claim();
 
-  if (Args.hasFlag(options::OPT_fsycl, options::OPT_fno_sycl, false)) {
+  Arg *SYCLStdArg = Args.getLastArg(options::OPT_sycl_std_EQ);
+
+  if (IsSYCLDevice) {
+    // Host triple is needed when doing SYCL device compilations.
+    llvm::Triple AuxT = C.getDefaultToolChain().getTriple();
+    std::string NormalizedTriple = AuxT.normalize();
+    CmdArgs.push_back("-aux-triple");
+    CmdArgs.push_back(Args.MakeArgString(NormalizedTriple));
+
+    // We want to compile sycl kernels.
     CmdArgs.push_back("-fsycl-is-device");
 
-    if (Arg *A = Args.getLastArg(options::OPT_sycl_std_EQ)) {
-      A->render(Args, CmdArgs);
+    // Set O2 optimization level by default
+    if (!Args.getLastArg(options::OPT_O_Group))
+      CmdArgs.push_back("-O2");
+  }
+
+  if (IsSYCL) {
+    // Set options for both host and device
+    if (SYCLStdArg) {
+      SYCLStdArg->render(Args, CmdArgs);
     } else {
       // Ensure the default version in SYCL mode is 2020.
       CmdArgs.push_back("-sycl-std=2020");
     }
+
+    // Add any options that are needed specific to SYCL offload while
+    // performing the host side compilation.
+    if (!IsSYCLDevice) {
+      // Let the front-end host compilation flow know about SYCL offload
+      // compilation.
+      CmdArgs.push_back("-fsycl-is-host");
+    }
----------------
mdtoguchi wrote:

Being in an `else` for `IsSYCLDevice` will pass `-fsycl-is-host` to all non-SYCL device compilations, even when offloading isn't enabled.  Maybe this can be structured to all be in an `IsSYCL` condition.  I will look into that.

https://github.com/llvm/llvm-project/pull/107493