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

[Tom Honermann via cfe-commits]

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@@ -979,6 +1000,44 @@ void Driver::CreateOffloadingDeviceToolChains(Compilation &C,
     return;
   }
 
+  //
+  // SYCL
+  //
+  // We need to generate a SYCL toolchain if the user specified -fsycl.
+  // If -fsycl is supplied we will assume SPIR-V.
+  bool IsSYCL =
+      C.getInputArgs().hasFlag(options::OPT_fsycl, options::OPT_fno_sycl,
+                               false);
+
+  auto argSYCLIncompatible = [&](OptSpecifier OptId) {
+    if (!IsSYCL)
+      return;
+    if (Arg *IncompatArg = C.getInputArgs().getLastArg(OptId))
+      Diag(clang::diag::err_drv_argument_not_allowed_with)
+          << IncompatArg->getSpelling() << "-fsycl";
+  };
+  // -static-libstdc++ is not compatible with -fsycl.
+  argSYCLIncompatible(options::OPT_static_libstdcxx);
+  // -ffreestanding cannot be used with -fsycl
+  argSYCLIncompatible(options::OPT_ffreestanding);
+
+  llvm::SmallVector<llvm::Triple, 4> UniqueSYCLTriplesVec;
+
+  // If -fsycl is supplied we will assume SPIR-V.
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tahonermann wrote:

Actually, this comment doesn't seem all that helpful here either. Perhaps it would be better colocated with `addSYCLDefaultTriple()`. Hmm, no, perhaps `getDefaultSYCLArch()` then?

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