[clang] Fix amdgpu-arch for dll name on Windows (PR #101350)

[Matt Arsenault via cfe-commits]

================
@@ -31,16 +44,118 @@ typedef hipError_t (*hipGetDeviceCount_t)(int *);
 typedef hipError_t (*hipDeviceGet_t)(int *, int);
 typedef hipError_t (*hipGetDeviceProperties_t)(hipDeviceProp_t *, int);
 
-int printGPUsByHIP() {
+extern cl::opt<bool> Verbose;
+
 #ifdef _WIN32
-  constexpr const char *DynamicHIPPath = "amdhip64.dll";
+static std::vector<std::string> getSearchPaths() {
+  std::vector<std::string> Paths;
+
+  // Get the directory of the current executable
+  if (auto MainExe = sys::fs::getMainExecutable(nullptr, nullptr);
+      !MainExe.empty())
+    Paths.push_back(sys::path::parent_path(MainExe).str());
+
+  // Get the system directory
+  wchar_t SystemDirectory[MAX_PATH];
+  if (GetSystemDirectoryW(SystemDirectory, MAX_PATH) > 0) {
+    std::string Utf8SystemDir;
+    if (convertUTF16ToUTF8String(
+            ArrayRef<UTF16>(reinterpret_cast<const UTF16 *>(SystemDirectory),
+                            wcslen(SystemDirectory)),
+            Utf8SystemDir))
+      Paths.push_back(Utf8SystemDir);
+  }
+
+  // Get the Windows directory
+  wchar_t WindowsDirectory[MAX_PATH];
+  if (GetWindowsDirectoryW(WindowsDirectory, MAX_PATH) > 0) {
+    std::string Utf8WindowsDir;
+    if (convertUTF16ToUTF8String(
+            ArrayRef<UTF16>(reinterpret_cast<const UTF16 *>(WindowsDirectory),
+                            wcslen(WindowsDirectory)),
+            Utf8WindowsDir))
+      Paths.push_back(Utf8WindowsDir);
+  }
+
+  // Get the current working directory
+  SmallVector<char, 256> CWD;
+  if (sys::fs::current_path(CWD))
+    Paths.push_back(std::string(CWD.begin(), CWD.end()));
+
+  // Get the PATH environment variable
+  if (auto PathEnv = sys::Process::GetEnv("PATH")) {
+    SmallVector<StringRef, 16> PathList;
+    StringRef(*PathEnv).split(PathList, sys::EnvPathSeparator);
+    for (auto &Path : PathList)
+      Paths.push_back(Path.str());
+  }
+
+  return Paths;
+}
+
+// Custom comparison function for dll name
+static bool compareVersions(const std::string &a, const std::string &b) {
+  // Extract version numbers
+  int versionA = std::stoi(a.substr(a.find_last_of('_') + 1));
+  int versionB = std::stoi(b.substr(b.find_last_of('_') + 1));
+  return versionA > versionB;
+}
+
+#endif
+
+// On Windows, prefer amdhip64_n.dll where n is ROCm major version and greater
+// value of n takes precedence. If amdhip64_n.dll is not found, fall back to
+// amdhip64.dll. The reason is that a normal driver installation only has
+// amdhip64_n.dll but we do not know what n is since this progrm may be used
+// with a future version of HIP runtime.
+//
+// On Linux, always use default libamdhip64.so.
+static std::pair<std::string, bool> findNewestHIPDLL() {
+#ifdef _WIN32
+  StringRef HipDLLPrefix = "amdhip64_";
+  StringRef HipDLLSuffix = ".dll";
+
+  std::vector<std::string> SearchPaths = getSearchPaths();
+  std::vector<std::string> DLLNames;
+
+  for (const auto &Dir : SearchPaths) {
+    std::error_code EC;
+    for (sys::fs::directory_iterator DirIt(Dir, EC), DirEnd;
+         DirIt != DirEnd && !EC; DirIt.increment(EC)) {
+      StringRef Filename = sys::path::filename(DirIt->path());
+      if (Filename.starts_with(HipDLLPrefix) &&
+          Filename.ends_with(HipDLLSuffix))
+        DLLNames.push_back(sys::path::convert_to_slash(DirIt->path()));
+    }
+    if (!DLLNames.empty())
+      break;
+  }
+
+  if (DLLNames.empty())
+    return {"amdhip64.dll", true};
+
+  std::sort(DLLNames.begin(), DLLNames.end(), compareVersions);
+  return {DLLNames[0], false};
 #else
-  constexpr const char *DynamicHIPPath = "libamdhip64.so";
+  // On Linux, fallback to default shared object
+  return {"libamdhip64.so", true};
 #endif
+}
+
+int printGPUsByHIP() {
+  auto [DynamicHIPPath, IsFallback] = findNewestHIPDLL();
+
+  if (Verbose) {
+    if (IsFallback)
+      outs() << "Using default HIP runtime: " << DynamicHIPPath << "\n";
+    else
+      outs() << "Found HIP runtime: " << DynamicHIPPath << "\n";
----------------
arsenm wrote:

```suggestion
    if (IsFallback)
      outs() << "Using default HIP runtime: " << DynamicHIPPath << '\n';
    else
      outs() << "Found HIP runtime: " << DynamicHIPPath << '\n';
```

https://github.com/llvm/llvm-project/pull/101350