Simplify Dispatcher case for zero arguments (#104613)
MSVC detects calling Dispatcher::callWithDispatchKeySlowPath with zero arguments. This PR fixes it and simplifies code.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/104613
Approved by: https://github.com/ezyang
diff --git a/aten/src/ATen/core/dispatch/Dispatcher.h b/aten/src/ATen/core/dispatch/Dispatcher.h
index 0066786..b794f37 100644
--- a/aten/src/ATen/core/dispatch/Dispatcher.h
+++ b/aten/src/ATen/core/dispatch/Dispatcher.h
@@ -589,27 +589,27 @@
auto dispatchKey = dispatchKeySet.highestPriorityTypeId();
auto& schema = op.schema();
auto schema_ref = std::reference_wrapper<const FunctionSchema>(schema);
- if (guard.needsInputs()) {
- constexpr auto num_boxed_args = impl::boxed_size<Args...>();
- // If we used std::array<IValue, num_boxed_args> here, we would
- // have to spend time default constructing the IValues in
- // boxedArgs. aligned_storage has no such requirement.
- // Max to avoid zero-size array.`
- std::aligned_storage_t<sizeof(IValue), alignof(IValue)> boxedArgs[std::max(num_boxed_args, static_cast<size_t>(1))];
- // For debugging only; could be removed (but the compiler will do
- // that for us and it's nice to have the extra assurance of
- // correctness from our debug builds).
- int lastArgIdx = 0;
- impl::boxArgsToStack(boxedArgs, lastArgIdx, args...);
- TORCH_INTERNAL_ASSERT_DEBUG_ONLY(lastArgIdx == num_boxed_args);
- // I don't *think* we need std::launder here, because IValue has
- // no subclasses and no const or reference fields. (We also
- // couldn't use it even if we wanted to because we are currently
- // stuck on C++14 rather than C++17, but we could do a backport
- // similar to folly::launder if needed.)
- runRecordFunction(guard, schema_ref, dispatchKey, c10::ArrayRef<const c10::IValue>(reinterpret_cast<IValue *>(boxedArgs), num_boxed_args));
- for (size_t ii = 0; ii < num_boxed_args; ++ii) {
- reinterpret_cast<IValue *>(&boxedArgs[ii])->~IValue();
+ constexpr auto num_boxed_args = impl::boxed_size<Args...>();
+ if constexpr (num_boxed_args != 0) {
+ if (guard.needsInputs()) {
+ // If we used std::array<IValue, num_boxed_args> here, we would
+ // have to spend time default constructing the IValues in
+ // boxedArgs. aligned_storage has no such requirement.
+ impl::IValueAlignedStorage boxedArgs[num_boxed_args];
+ // For debugging only; could be removed (but the compiler will do
+ // that for us and it's nice to have the extra assurance of
+ // correctness from our debug builds).
+ int lastArgIdx = 0;
+ impl::boxArgsToStack(boxedArgs, lastArgIdx, args...);
+ TORCH_INTERNAL_ASSERT_DEBUG_ONLY(lastArgIdx == num_boxed_args);
+ // I don't *think* we need std::launder here, because IValue has
+ // no subclasses and no const or reference fields.
+ runRecordFunction(guard, schema_ref, dispatchKey, c10::ArrayRef<const c10::IValue>(reinterpret_cast<IValue *>(boxedArgs), num_boxed_args));
+ for (size_t ii = 0; ii < num_boxed_args; ++ii) {
+ reinterpret_cast<IValue *>(&boxedArgs[ii])->~IValue();
+ }
+ } else {
+ runRecordFunction(guard, schema_ref, dispatchKey);
}
} else {
runRecordFunction(guard, schema_ref, dispatchKey);
