73038144e7
Backport of #20936 --- ## Description As part of the fix for: https://github.com/dotnet/runtime/issues/99248 we disabled dedup optimization in partial/hybrid AOT mode (when both interpreter and AOT compiler are enabled). This change got backported to .NET 8 and with the latest servicing release regressed build times and app sizes significantly as reported in: https://github.com/xamarin/xamarin-macios/issues/20848 However, it turns out that disabling dedup optimization is not required to fix https://github.com/dotnet/runtime/issues/99248 but instead we should correct the Xamarin SDK integration with this optimization which this PR is doing. The following section describes the initial problem in more details. ## Overview of AOT modes and dedup optimization When the repro project from https://github.com/dotnet/runtime/issues/99248 is built with dedup enabled in hybrid AOT+interpreter mode, the app crashes with: ``` 024-07-23 14:32:37.524110+0200 IvansApp[12711:20244208] debug: AOT NOT FOUND: (wrapper other) object:gsharedvt_out_sig (intptr). 2024-07-23 14:32:37.524120+0200 IvansApp[12711:20244208] error: * Assertion at /Users/ivan/repos/runtime-mono-iOS/src/mono/mono/mini/interp/interp.c:2667, condition `is_ok (error)' not met, function:init_jit_call_info, Attempting to JIT compile method '(wrapper other) void object:gsharedvt_out_sig (intptr)' while running in aot-only mode. See https://learn.microsoft.com/xamarin/ios/internals/limitations for more information. ``` To track down why these wrappers which are used to transition from interpreter to AOT code, are not generated we need to understand when they are compiled in different AOT modes with and without dedup optimization enabled: - In full AOT setup - all assemblies AOT compiled - `gsharedvt_out_sig` methods are never generated - In hybrid AOT + interpreter setup - all assemblies AOT compiled: `MtouchInterpreter=-all` - Dedup OFF: - `gsharedvt_out_sig` methods are generated in AOT images of every assembly (to enable interpreter calling into each specific assembly - here wrappers with same signatures are duplicated) - Dedup ON: - `gsharedvt_out_sig` methods are generated only in `aot-instances` AOT image - during AOT compilation of individual assemblies generation of `gsharedvt_out_sig` is skipped - during AOT compilation of `aot-instances` assembly we collect all `gsharedvt_out_sig` variants from the full program scope and generate code for them in `aot-instances` AOT image - In hybrid AOT + interpreter setup - all assemblies interpreted except a given assembly: `MtouchInterpreter=all,-MyAssembly` - Dedup OFF: - `gsharedvt_out_sig` methods are generated in AOT image of `MyAssembly` (to enable interpreter calling into it) - Dedup ON: <- $${\color{red} ISSUE }$$ - `gsharedvt_out_sig` methods *should* be generated only in `aot-instances` AOT image, but the `aot-instances` image is missing - explanation: - what happens is that generation of `gsharedvt_out_sig` is skipped during AOT compilation of `MyAssembly` (as expected). - But, the build does not mark `aot-instances` assembly as the one that should be AOT compiled. - The reason for this is that we have a global `_IsDedupEnabled` flag, but when custom linker step analysis `aot-instances.dll` it does not see it as an assembly which should not be interpreted. - To explain that better: we mark *all* assemblies as to be interpreted (via: `MtouchInterpreter=all`), but exclude only `MyAssembly` (via: `MtouchInterpreter=all,-MyAssembly`). - So when custom linker step processes `aot-instaces.dll` it treats it as an assembly to be interpreted, so it does not mark it for AOT compilation. - This further results with `aot-instances` AOT image missing, and all the methods which we skipped during AOT compilation never get generated. ## The fix To fix this and address regressions reported in: https://github.com/xamarin/xamarin-macios/issues/20848 we are reenabling dedup optimization whenever AOT compilation is requested and fixing the issue where the custom linker step for generating AOT parameters always treates the dedup assembly as the one to be AOTed. Once approved this should be backported to .NET 8 as servicing releases are also affected with it. --------- Co-authored-by: Ivan Povazan <ivan.povazan@gmail.com> Co-authored-by: GitHub Actions Autoformatter <github-actions-autoformatter@xamarin.com> |
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README.md
.NET for iOS, Mac Catalyst, macOS, tvOS
Welcome!
This module is the main repository for:
- .NET for iOS
- .NET for Mac Catalyst
- .NET for macOS
- .NET for tvOS
These SDKs allow us to create native iOS, Mac Catalyst, macOS and tvOS applications using the same UI controls we would in Objective-C and Xcode, except with the flexibility and elegance of a modern language (C#), the power of the .NET Base Class Library (BCL), and first-class IDEs and editors—Visual Studio and Visual Studio Code—at our fingertips.
This repository is where we do development for the .NET for iOS, Mac Catalyst, macOS, and tvOS SDKs. .NET for iOS, Mac Catalyst, macOS, and tvOS are part of .NET MAUI, and may also be used independently for native iOS and macOS development with .NET.
There are a few ways that you can contribute, for example:
- Submit bugs and feature requests
- Review source code changes
- Submit pull requests to resolve issues and fix bugs
Support
.NET for iOS, Mac Catalyst, macOS, and tvOS are part of .NET MAUI, since it was introduced in May 2022 as part of .NET 6, and is currently supported as described on the .NET MAUI Support Policy.
Support for Xamarin.iOS and Xamarin.Mac ended on May 1, 2024 as per the Xamarin Support Policy:
Xamarin support ended on May 1, 2024 for all Xamarin SDKs including Xamarin.Forms. Android API 34 and Xcode 15 SDKs (iOS and iPadOS 17, macOS 14) are the final versions Xamarin targets from existing Xamarin SDKs (i.e. no new APIs are planned).
Contributing
If you are interested in fixing issues and contributing directly to the code base, please see the document How to Contribute, which covers the following:
- How to build and run from source
- The development workflow, including debugging and running tests
- Coding Guidelines
- Submitting pull requests
Downloads
The preferred method for installing Xamarin.iOS and Mac is to use the Visual Studio installers (Windows, Mac).
The team also strongly recommends using the latest Xamarin SDK and Xcode whenever possible.
However, we provide links to older Xamarin.iOS and Mac packages for macOS downgrades and build machine configuration, see Downloads.
Feedback
- Ask a question on Stack Overflow or the Xamarin Forums
- Request a new feature on GitHub
- Vote on existing feature requests
- Submit bugs to GitHub Issues
- Discuss development and design on Discord
License
Copyright (c) .NET Foundation Contributors. All rights reserved. Licensed under the MIT License.