[qt/clang/llvm-project]: Summary of bulk changes made

Git repository change summary for qt/clang/llvm-project
Pushed by mirror-service into branch 'upstream/users/gandhi56/sandbox-vectorizer/topdown-vec'.
Changed from 6c01528e0b3bad3348753818e613892d66622257 to 891b0be17585754084e9c37db66116c18296eb65
Acknowledgement was received that this change introduces only existing code that has been pushed to another public open source repository.

This change contains the following new commits:

Git commit b42ecb3529b13998a353a815250c6d903f77ca33 by Anshil Gandhi on 21/07/2026 at 17:01..
[SBVec] Refill ready list during topdown scheduling

Visit nodes which are ready according to the direction of scheduling.
https://invent.kde.org/qt/clang/llvm-project/-/commit/b42ecb3529b13998a353a815250c6d903f77ca33

Git commit 2b5182e95334e05c28f815896a02b2ee29b89423 by Anshil Gandhi on 21/07/2026 at 17:02..
[SBVec] Add top-down vectorization to the unified Sandbox Vectorizer

Extend the Sandbox Vectorizer's `bottom-up-vec` pass so a single
implementation can vectorize in either direction, and add the top-down
strategy that walks def-use chains forward from a seed.

Direction selection
--------------------
The pass direction is chosen from the Region's auxiliary pass argument:
"bottom-up" (or empty, the default) and "top-down" map onto a
SchedDirection, and any other value is rejected with a fatal usage error.
The vectorizer always runs in the same direction as the scheduler.

Top-down traversal
------------------
Bottom-up starts from a seed slice (e.g. stores to consecutive addresses)
and recurses into operands. Top-down instead starts from a seed of
consecutive loads and recurses into *users*:

- vectorizeRec() registers the current bundle's vector (pre-order) before
  recursing, so instructions are marked vectorized as soon as they are
  claimed. This prevents sibling user bundles from claiming the same
  instruction and guarantees termination.
- VecUtils::getNextUserBundles() drives the walk. For each user of lane 0
  it tries to assemble a matching user for every remaining lane, requiring
  the same opcode, type, parent block, and operand-usage indices, and
  claiming each instruction at most once. Only complete bundles (one user
  per lane) are returned.
- A non-Widen legality result stops the walk down that path: the bundle is
  left scalar and no action is recorded. DiamondReuse results cannot occur
  top-down because already-vectorized users are skipped, so a bundle never
  contains an instruction already in InstrMaps.

Operand and external-use handling
---------------------------------
Because a user bundle is emitted after its operand bundle, emitVectors()
looks up each operand's vector in InstrMaps and creates a pack when the
operand was not vectorized. emitUnpacksForExternalUses() now redirects
only the genuinely external (non-vectorized) uses via replaceUsesWithIf(),
instead of a blanket replaceAllUsesWith() that would corrupt the operands
of user bundles not yet emitted. Scheduling is currently skipped for the
top-down direction (TODO).

Refactoring
-----------
Unify the two strategies to avoid code duplication: introduce a shared
BundleTy alias, move user-bundle collection into VecUtils (with unit
tests), and thread the direction through legality checks and vector
emission.

Co-authored-by: Cursor <[email protected]>
https://invent.kde.org/qt/clang/llvm-project/-/commit/2b5182e95334e05c28f815896a02b2ee29b89423

Git commit 0dfd71ee4d51e085d80d5f158f7f8c12408f8a54 by Anshil Gandhi on 21/07/2026 at 17:02..
[SBVec] Refactor BottomUpVec pass for clarity and maintainability

- Corrected comments to clarify the direction of def-use and use-def chains.
- Changed the initialization of the SchedDirection variable to improve clarity.
- Updated documentation in vectorizeRec() to better describe the purpose of UserBndl.
- Removed outdated TODO comment regarding top-down vectorization scheduling.
https://invent.kde.org/qt/clang/llvm-project/-/commit/0dfd71ee4d51e085d80d5f158f7f8c12408f8a54

Git commit f7f74c0ce6949ca759ecfdf952ac61d7dbc8d792 by Anshil Gandhi on 21/07/2026 at 18:28..
[SBVec] Track claimed users across bundles
https://invent.kde.org/qt/clang/llvm-project/-/commit/f7f74c0ce6949ca759ecfdf952ac61d7dbc8d792

Git commit 891b0be17585754084e9c37db66116c18296eb65 by Anshil Gandhi on 21/07/2026 at 19:08..
3 element tests
https://invent.kde.org/qt/clang/llvm-project/-/commit/891b0be17585754084e9c37db66116c18296eb65