[Offload] Treat an empty packager architecture as 'generic' (llvm#126655)

Summary:
The `clang-offload-packager` records the architecture of the job.
Currently there are cases where this will be empty. SYCL, CPU, and when
the user manually overrides it to be empty. In these cases we should
alwas consider it 'generic'. Adding this string both makes it clear how
it behaves and triggers the special handling for this architecture,
allowing it to bind to different architectures.

Author: jhuber6

clang/lib/Driver/ToolChains/Clang.cpp

@@ -9163,7 +9163,7 @@ void OffloadPackager::ConstructJob(Compilation &C, const JobAction &JA,
     SmallVector<std::string> Parts{
         "file=" + File.str(),
         "triple=" + TC->getTripleString(),
-        "arch=" + Arch.str(),
+        "arch=" + (Arch.empty() ? "generic" : Arch.str()),
         "kind=" + Kind.str(),
     };
 

clang/test/Driver/linker-wrapper.c

@@ -59,7 +59,7 @@ __attribute__((visibility("protected"), used)) int x;
 // RUN:   --linker-path=/usr/bin/ld.lld --whole-archive %t.a --no-whole-archive \
 // RUN:   %t.o -o a.out 2>&1 | FileCheck %s --check-prefix=CPU-LINK
 
-// CPU-LINK: clang{{.*}} -o {{.*}}.img --target=x86_64-unknown-linux-gnu -march=native -O2 -flto -Wl,--no-undefined {{.*}}.o {{.*}}.o -Wl,-Bsymbolic -shared -Wl,--whole-archive {{.*}}.a -Wl,--no-whole-archive
+// CPU-LINK: clang{{.*}} -o {{.*}}.img --target=x86_64-unknown-linux-gnu -O2 -flto -Wl,--no-undefined {{.*}}.o {{.*}}.o -Wl,-Bsymbolic -shared -Wl,--whole-archive {{.*}}.a -Wl,--no-whole-archive
 
 // RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -o %t.o
 // RUN: clang-linker-wrapper --dry-run --host-triple=x86_64-unknown-linux-gnu -mllvm -openmp-opt-disable \

clang/test/Driver/sycl-offload-jit.cpp

@@ -27,7 +27,7 @@
 // CHK-DEVICE-TRIPLE-SAME: "-aux-triple" "x86_64-unknown-linux-gnu"
 // CHK-DEVICE-TRIPLE-SAME: "-fsycl-is-device"
 // CHK-DEVICE-TRIPLE-SAME: "-O2"
-// CHK-DEVICE-TRIPLE: clang-offload-packager{{.*}} "--image=file={{.*}}.bc,triple=spirv64-unknown-unknown,arch=,kind=sycl"
+// CHK-DEVICE-TRIPLE: clang-offload-packager{{.*}} "--image=file={{.*}}.bc,triple=spirv64-unknown-unknown,arch=generic,kind=sycl"
 
 /// Check -fsycl-is-device is passed when compiling for the device.
 /// Check -fsycl-is-host is passed when compiling for host.

clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp

@@ -474,8 +474,6 @@ Expected<StringRef> clang(ArrayRef<StringRef> InputFiles, const ArgList &Args) {
 
   const llvm::Triple Triple(Args.getLastArgValue(OPT_triple_EQ));
   StringRef Arch = Args.getLastArgValue(OPT_arch_EQ);
-  if (Arch.empty())
-    Arch = "native";
   // Create a new file to write the linked device image to. Assume that the
   // input filename already has the device and architecture.
   auto TempFileOrErr =
@@ -492,11 +490,14 @@ Expected<StringRef> clang(ArrayRef<StringRef> InputFiles, const ArgList &Args) {
       "-o",
       *TempFileOrErr,
       Args.MakeArgString("--target=" + Triple.getTriple()),
-      Triple.isAMDGPU() ? Args.MakeArgString("-mcpu=" + Arch)
-                        : Args.MakeArgString("-march=" + Arch),
-      Args.MakeArgString("-" + OptLevel),
   };
 
+  if (!Arch.empty())
+    Triple.isAMDGPU() ? CmdArgs.push_back(Args.MakeArgString("-mcpu=" + Arch))
+                      : CmdArgs.push_back(Args.MakeArgString("-march=" + Arch));
+
+  CmdArgs.push_back(Args.MakeArgString("-" + OptLevel));
+
   // Forward all of the `--offload-opt` and similar options to the device.
   CmdArgs.push_back("-flto");
   for (auto &Arg : Args.filtered(OPT_offload_opt_eq_minus, OPT_mllvm))
@@ -826,8 +827,9 @@ DerivedArgList getLinkerArgs(ArrayRef<OffloadFile> Input,
 
   // Set the subarchitecture and target triple for this compilation.
   const OptTable &Tbl = getOptTable();
+  StringRef Arch = Args.MakeArgString(Input.front().getBinary()->getArch());
   DAL.AddJoinedArg(nullptr, Tbl.getOption(OPT_arch_EQ),
-                   Args.MakeArgString(Input.front().getBinary()->getArch()));
+                   Arch == "generic" ? "" : Arch);
   DAL.AddJoinedArg(nullptr, Tbl.getOption(OPT_triple_EQ),
                    Args.MakeArgString(Input.front().getBinary()->getTriple()));