[clang] [HIP] Allow partial linking for `-fgpu-rdc` (PR #81700)

[Yaxun Liu via cfe-commits]

================
@@ -36,6 +47,146 @@ static std::string normalizeForBundler(const llvm::Triple &T,
                      : T.normalize();
 }
 
+// Collect undefined __hip_fatbin* and __hip_gpubin_handle* symbols from all
+// input object or archive files.
+class HIPUndefinedFatBinSymbols {
+public:
+  HIPUndefinedFatBinSymbols(const Compilation &C)
+      : C(C), DiagID(C.getDriver().getDiags().getCustomDiagID(
+                  DiagnosticsEngine::Error,
+                  "Error collecting HIP undefined fatbin symbols: %0")),
+        Quiet(C.getArgs().hasArg(options::OPT__HASH_HASH_HASH)),
+        Verbose(C.getArgs().hasArg(options::OPT_v)) {
+    populateSymbols();
+    if (Verbose) {
+      for (auto Name : FatBinSymbols)
+        llvm::errs() << "Found undefined HIP fatbin symbol: " << Name << "\n";
+      for (auto Name : GPUBinHandleSymbols)
+        llvm::errs() << "Found undefined HIP gpubin handle symbol: " << Name
+                     << "\n";
+    }
+  }
+
+  const std::set<std::string> &getFatBinSymbols() const {
+    return FatBinSymbols;
+  }
+
+  const std::set<std::string> &getGPUBinHandleSymbols() const {
+    return GPUBinHandleSymbols;
+  }
+
+private:
+  const Compilation &C;
+  unsigned DiagID;
+  bool Quiet;
+  bool Verbose;
+  std::set<std::string> FatBinSymbols;
+  std::set<std::string> GPUBinHandleSymbols;
+  const std::string FatBinPrefix = "__hip_fatbin";
+  const std::string GPUBinHandlePrefix = "__hip_gpubin_handle";
+
+  void populateSymbols() {
+    std::deque<const Action *> WorkList;
+    std::set<const Action *> Visited;
+
+    for (const auto &Action : C.getActions()) {
+      WorkList.push_back(Action);
+    }
+
+    while (!WorkList.empty()) {
+      const Action *CurrentAction = WorkList.front();
+      WorkList.pop_front();
+
+      if (!CurrentAction || !Visited.insert(CurrentAction).second)
+        continue;
+
+      if (const auto *IA = dyn_cast<InputAction>(CurrentAction)) {
+        std::string ID = IA->getId().str();
+        if (!ID.empty()) {
+          ID = llvm::utohexstr(llvm::MD5Hash(ID), /*LowerCase=*/true);
+          FatBinSymbols.insert(Twine(FatBinPrefix + "_" + ID).str());
+          GPUBinHandleSymbols.insert(
+              Twine(GPUBinHandlePrefix + "_" + ID).str());
+          continue;
+        }
+        const char *Filename = IA->getInputArg().getValue();
+        auto BufferOrErr = llvm::MemoryBuffer::getFile(Filename);
+        // Input action could be options to linker, therefore ignore it
+        // if cannot read it.
----------------
yxsamliu wrote:

If the argument is an input file and it fails to be read, the error will be captured by the linker and error will be emitted there.

will fix the comment.

https://github.com/llvm/llvm-project/pull/81700