[clang] [llvm] [Offload] Introduce the concept of "default streams" (PR #95371)

[Matt Arsenault via llvm-commits]

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@@ -1125,6 +1125,22 @@ void Clang::AddPreprocessingOptions(Compilation &C, const JobAction &JA,
     CmdArgs.push_back("__clang_openmp_device_functions.h");
   }
 
+  if (Args.hasArg(options::OPT_foffload_via_llvm)) {
+    // Add llvm_wrappers/* to our system include path.  This lets us wrap
+    // standard library headers and other headers.
+    SmallString<128> P(D.ResourceDir);
+    llvm::sys::path::append(P, "include");
+    llvm::sys::path::append(P, "llvm_offload_wrappers");
+    CmdArgs.push_back("-internal-isystem");
+    CmdArgs.push_back(Args.MakeArgString(P));
+
+    CmdArgs.push_back("-include");
+    if (JA.isDeviceOffloading(Action::OFK_OpenMP))
+      CmdArgs.push_back("__llvm_offload_device.h");
+    else
+      CmdArgs.push_back("__llvm_offload_host.h");
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arsenm wrote:

Push pack select of string name? 

https://github.com/llvm/llvm-project/pull/95371