[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 9ab51a638292ff993893c1ab22b5d0a593ac9631 to 0cdc13f8a7b106140d22516e519ad70c7d24dace
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 06bbd269cb8863279c235f07c8e08d6ed2744db8 by GitHub (on behalf of Anshil Gandhi) on 22/07/2026 at 05:14..
[SandboxVec][Scheduler] Refill ready list during topdown scheduling (#211046)

Visit nodes which are ready according to the direction of scheduling.
https://invent.kde.org/qt/clang/llvm-project/-/commit/06bbd269cb8863279c235f07c8e08d6ed2744db8

Git commit 8b992480dbc5d6af582118d65ceb46139589e289 by Anshil Gandhi on 22/07/2026 at 05:14..
[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/8b992480dbc5d6af582118d65ceb46139589e289

Git commit 8970b1bdcb0eb55295a06433bce05fa60198252b by Anshil Gandhi on 22/07/2026 at 05:14..
[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/8970b1bdcb0eb55295a06433bce05fa60198252b

Git commit 967bf78680ee0a938b71ff6031190b499e2fe8dc by Anshil Gandhi on 22/07/2026 at 05:14..
[SBVec] Track claimed users across bundles
https://invent.kde.org/qt/clang/llvm-project/-/commit/967bf78680ee0a938b71ff6031190b499e2fe8dc

Git commit 5d90d816f9426dffd94c9a64c56bf1d649023976 by Anshil Gandhi on 22/07/2026 at 05:14..
3 element tests

- nits
https://invent.kde.org/qt/clang/llvm-project/-/commit/5d90d816f9426dffd94c9a64c56bf1d649023976

Git commit 0cdc13f8a7b106140d22516e519ad70c7d24dace by Anshil Gandhi on 22/07/2026 at 05:14..
Add 3-way test to check for consecutive matching
https://invent.kde.org/qt/clang/llvm-project/-/commit/0cdc13f8a7b106140d22516e519ad70c7d24dace