[Offload] Refactor device information queries to use new tagging

[RossBrunton]

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.

[llvmbot]

@llvm/pr-subscribers-offload

Author: Ross Brunton (RossBrunton)

Changes

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.

---

Full diff: https://github.com/llvm/llvm-project/pull/147318.diff

2 Files Affected:

• (modified) offload/liboffload/src/Helpers.hpp (+6-13)
• (modified) offload/liboffload/src/OffloadImpl.cpp (+48-63)

diff --git a/offload/liboffload/src/Helpers.hpp b/offload/liboffload/src/Helpers.hpp
index 8b85945508b98..62e55e500fac7 100644
--- a/offload/liboffload/src/Helpers.hpp
+++ b/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:
diff --git a/offload/liboffload/src/OffloadImpl.cpp b/offload/liboffload/src/OffloadImpl.cpp
index f9da638436705..c84bf01460252 100644
--- a/offload/liboffload/src/OffloadImpl.cpp
+++ b/offload/liboffload/src/OffloadImpl.cpp
@@ -286,78 +286,63 @@ 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,

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