[Offload] Refactor device information queries to use new tagging

Instead using strings to look up device information (which is brittle
and slow), use the new tags that the plugins specify when building the
nodes.

Author: RossBrunton

offload/liboffload/src/Helpers.hpp

@@ -75,23 +75,16 @@ class InfoWriter {
   InfoWriter(InfoWriter &) = delete;
   ~InfoWriter() = default;
 
-  template <typename T> llvm::Error write(llvm::Expected<T> &&Val) {
-    if (Val)
-      return getInfo(Size, Target, SizeRet, *Val);
-    return Val.takeError();
+  template <typename T> llvm::Error write(T Val) {
+    return getInfo(Size, Target, SizeRet, Val);
   }
 
-  template <typename T>
-  llvm::Error writeArray(llvm::Expected<T> &&Val, size_t Elems) {
-    if (Val)
-      return getInfoArray(Elems, Size, Target, SizeRet, *Val);
-    return Val.takeError();
+  template <typename T> llvm::Error writeArray(T Val, size_t Elems) {
+    return getInfoArray(Elems, Size, Target, SizeRet, Val);
   }
 
-  llvm::Error writeString(llvm::Expected<llvm::StringRef> &&Val) {
-    if (Val)
-      return getInfoString(Size, Target, SizeRet, *Val);
-    return Val.takeError();
+  llvm::Error writeString(llvm::StringRef Val) {
+    return getInfoString(Size, Target, SizeRet, Val);
   }
 
 private:

offload/liboffload/src/OffloadImpl.cpp

@@ -299,78 +299,63 @@ Error olGetDeviceInfoImplDetail(ol_device_handle_t Device,
     return Plugin::error(ErrorCode::UNIMPLEMENTED, ErrBuffer.c_str());
   };
 
-  // Find the info if it exists under any of the given names
-  auto getInfoString =
-      [&](std::vector<std::string> Names) -> llvm::Expected<const char *> {
-    for (auto &Name : Names) {
-      if (auto Entry = Device->Info.get(Name)) {
-        if (!std::holds_alternative<std::string>((*Entry)->Value))
-          return makeError(ErrorCode::BACKEND_FAILURE,
-                           "plugin returned incorrect type");
-        return std::get<std::string>((*Entry)->Value).c_str();
-      }
-    }
-
-    return makeError(ErrorCode::UNIMPLEMENTED,
-                     "plugin did not provide a response for this information");
-  };
-
-  auto getInfoXyz =
-      [&](std::vector<std::string> Names) -> llvm::Expected<ol_dimensions_t> {
-    for (auto &Name : Names) {
-      if (auto Entry = Device->Info.get(Name)) {
-        auto Node = *Entry;
-        ol_dimensions_t Out{0, 0, 0};
-
-        auto getField = [&](StringRef Name, uint32_t &Dest) {
-          if (auto F = Node->get(Name)) {
-            if (!std::holds_alternative<size_t>((*F)->Value))
-              return makeError(
-                  ErrorCode::BACKEND_FAILURE,
-                  "plugin returned incorrect type for dimensions element");
-            Dest = std::get<size_t>((*F)->Value);
-          } else
-            return makeError(ErrorCode::BACKEND_FAILURE,
-                             "plugin didn't provide all values for dimensions");
-          return Plugin::success();
-        };
-
-        if (auto Res = getField("x", Out.x))
-          return Res;
-        if (auto Res = getField("y", Out.y))
-          return Res;
-        if (auto Res = getField("z", Out.z))
-          return Res;
-
-        return Out;
-      }
-    }
+  // These are not implemented by the plugin interface
+  if (PropName == OL_DEVICE_INFO_PLATFORM)
+    return Info.write<void *>(Device->Platform);
+  if (PropName == OL_DEVICE_INFO_TYPE)
+    return Info.write<ol_device_type_t>(OL_DEVICE_TYPE_GPU);
+  // TODO: Update when https://github.com/llvm/llvm-project/pull/147314 is merged
+  if (PropName > OL_DEVICE_INFO_MAX_WORK_GROUP_SIZE)
+    return createOffloadError(ErrorCode::INVALID_ENUMERATION,
+                              "getDeviceInfo enum '%i' is invalid", PropName);
 
+  auto EntryOpt = Device->Info.get(static_cast<DeviceInfo>(PropName));
+  if (!EntryOpt)
     return makeError(ErrorCode::UNIMPLEMENTED,
                      "plugin did not provide a response for this information");
-  };
+  auto Entry = *EntryOpt;
 
   switch (PropName) {
-  case OL_DEVICE_INFO_PLATFORM:
-    return Info.write<void *>(Device->Platform);
-  case OL_DEVICE_INFO_TYPE:
-    return Info.write<ol_device_type_t>(OL_DEVICE_TYPE_GPU);
   case OL_DEVICE_INFO_NAME:
-    return Info.writeString(getInfoString({"Device Name"}));
   case OL_DEVICE_INFO_VENDOR:
-    return Info.writeString(getInfoString({"Vendor Name"}));
-  case OL_DEVICE_INFO_DRIVER_VERSION:
-    return Info.writeString(
-        getInfoString({"CUDA Driver Version", "HSA Runtime Version"}));
-  case OL_DEVICE_INFO_MAX_WORK_GROUP_SIZE:
-    return Info.write(getInfoXyz({"Workgroup Max Size per Dimension" /*AMD*/,
-                                  "Maximum Block Dimensions" /*CUDA*/}));
-  default:
-    return createOffloadError(ErrorCode::INVALID_ENUMERATION,
-                              "getDeviceInfo enum '%i' is invalid", PropName);
+  case OL_DEVICE_INFO_DRIVER_VERSION: {
+    // String values
+    if (!std::holds_alternative<std::string>(Entry->Value))
+      return makeError(ErrorCode::BACKEND_FAILURE,
+                       "plugin returned incorrect type");
+    return Info.writeString(std::get<std::string>(Entry->Value).c_str());
   }
 
-  return Error::success();
+  case OL_DEVICE_INFO_MAX_WORK_GROUP_SIZE: {
+    // {x, y, z} triples
+    ol_dimensions_t Out{0, 0, 0};
+
+    auto getField = [&](StringRef Name, uint32_t &Dest) {
+      if (auto F = Entry->get(Name)) {
+        if (!std::holds_alternative<size_t>((*F)->Value))
+          return makeError(
+              ErrorCode::BACKEND_FAILURE,
+              "plugin returned incorrect type for dimensions element");
+        Dest = std::get<size_t>((*F)->Value);
+      } else
+        return makeError(ErrorCode::BACKEND_FAILURE,
+                         "plugin didn't provide all values for dimensions");
+      return Plugin::success();
+    };
+
+    if (auto Res = getField("x", Out.x))
+      return Res;
+    if (auto Res = getField("y", Out.y))
+      return Res;
+    if (auto Res = getField("z", Out.z))
+      return Res;
+
+    return Info.write(Out);
+  }
+
+  default:
+    llvm_unreachable("Unimplemented device info");
+  }
 }
 
 Error olGetDeviceInfoImplDetailHost(ol_device_handle_t Device,