Qualcomm AI Engine Direct - Support MSVC-compatible code

[zhaoxul-qti]

Summary

1. Remove the designated initializers for C++

Why it compiles on Linux but not on Windows MSVC?

• Designated initializers for C++ aggregates were standardized in C++20. GCC and Clang have supported them as a C++11/14/17 extension — they silently accept the syntax even when compiling in -std=c++17 mode. MSVC is strictly conformant: it only accepts designated initializers when /std:c++20 (or /std:c++latest) is active.

2. Remove the GNU statement expressions

Why it compiles on Linux but not on Windows MSVC?

• The GNU statement expression is a GNU C / GNU C++ language extension that lets you treat a block of statements as if it were a single expression that produces a value. It is not part of standard C or C++, but it is widely supported by GCC and Clang. MSVC does not support it.

3. Replace constexpr inside the lambda [&]

• ET_INTERNAL_SWITCH wraps the NAME in [&] { ... }(). The [&] capture means the lambda captures all local variables by reference, including NAME.
• However, inside the lambda [&], NAME is accessed via the closure's implicit this pointer — it is (*this).name in the closure's internal representation to capture variables by reference. Dereferencing this is not a constant expression because this is a runtime pointer to the closure object, which is not a constant expression and only exists at runtime.

Why it compiles on Linux but not on Windows MSVC?

• GCC and Clang are more permissive here. They apply a special rule: if the captured variable is itself constexpr and its value is a compile-time constant, they allow it to be used as a constant expression inside the lambda, effectively treating the capture as a constant propagation rather than a runtime dereference. This is a quality-of-implementation extension beyond what the standard strictly requires.

4. Replace the __attribute__((visibility("default"))) with corresponding MSVC-compatible syntax

• Use Microsoft-specific C/C++ extensions __declspec(dllexport) and __declspec(dllimport) to control symbol visibility when working with Windows DLLs.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/19686

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

❗ 1 Active SEVs

There are 1 currently active SEVs. If your PR is affected, please view them below:

• Run pull request jobs on OSDC runners in shadow mode

⚠️ 15 Awaiting Approval

As of commit d7cddf0 with merge base a4bd823 ():

AWAITING APPROVAL - The following workflows need approval before CI can run:

• Build Aarch64 Linux Wheels (gh)
• Build documentation (gh)
• Build Linux Wheels (gh)
• Build macOS Wheels (gh)
• Build Presets (gh)
• Build Windows Wheels (gh)
• Cadence Build & Test (gh)
• Lint (gh)
• periodic (gh)
• pull (gh)
• Test ARM Backend (gh)
• Test CoreML Backend (gh)
• Test QNN Backend (gh)
• Test Vulkan Backend (gh)
• Test XNNPACK Backend (gh)

This comment was automatically generated by Dr. CI and updates every 15 minutes.

[github-actions]

This PR needs a release notes: label

If your change should be included in the release notes (i.e. would users of this library care about this change?), please use a label starting with release notes:. This helps us keep track and include your important work in the next release notes.

To add a label, you can comment to pytorchbot, for example
@pytorchbot label "release notes: none"

For more information, see
https://github.com/pytorch/pytorch/wiki/PyTorch-AutoLabel-Bot#why-categorize-for-release-notes-and-how-does-it-work.

[zhaoxul-qti]

This PR also fix the issue mentioned in 4b7bea2