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

Git repository change summary for qt/clang/llvm
Pushed by mirror-service into branch 'upstream/users/jeanPerier/merge_memory_passes_3'.
Changed from 0000000000000000000000000000000000000000 to fe44e4902ff39e129b69d0704da1dfb93318d9ba
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 e9a17d03184d4389987a55e3eb6a306b71c74918 by Jean Perier (on behalf of root) on 20/07/2026 at 09:01..
[flang][NFC] Extract StackArrays analysis and rewrite into a header

Move InsertionPoint, StackArraysAnalysisWrapper, and AllocMemConversion
out of the anonymous namespace in StackArrays.cpp into a new
StackArrays.h header (in namespace fir), so the "which fir.allocmem can
be safely moved to the stack, and where" analysis and the heap-to-stack
rewrite pattern can be reused by other passes.

The dataflow internals (AllocationState, LatticePoint, AllocationAnalysis),
the command-line options, and all method definitions remain in the .cpp.
No functional change intended.
https://invent.kde.org/qt/clang/llvm/-/commit/e9a17d03184d4389987a55e3eb6a306b71c74918

Git commit e0e7544fd7d593175f863e198d1e9e20824e74fa by Jean Perier (on behalf of root) on 20/07/2026 at 15:22..
[flang] Add policy-driven allocation-placement pass

Introduce a new function-level pass, allocation-placement, that unifies the
stack/heap placement decisions currently split between the stack-arrays and
memory-allocation-opt passes. For each array allocation it consults a policy
to decide whether it should live on the stack (fir.alloca) or the heap
(fir.allocmem) and rewrites it accordingly, reusing fir::replaceAllocas for
stack-to-heap and the StackArrays analysis/rewrite for heap-to-stack (so
heap-to-stack only happens where it is provably safe).

The default policy (AllocationPlacementPolicy.h) is threshold-driven:
  - small constant-size arrays go on the stack within a per-function stack
    budget, otherwise on the heap;
  - big constant-size arrays: user variables stay on the stack, temporaries
    go on the heap;
  - runtime-sized arrays go on the heap;
  - an aggressive mode places all arrays on the stack (best effort).
User variables are distinguished from compiler temporaries via the presence
of a uniqued name. A hook lets downstream users override the thresholds per
allocation (e.g. for device routines or parallel regions).

The pass is not wired into any pipeline yet; it is reachable through fir-opt
and covered by isolated tests.
https://invent.kde.org/qt/clang/llvm/-/commit/e0e7544fd7d593175f863e198d1e9e20824e74fa

Git commit fe44e4902ff39e129b69d0704da1dfb93318d9ba by root on 20/07/2026 at 15:40..
[flang] Wire allocation-placement into the optimizer pipeline (experimental)

Add a hidden -enable-allocation-placement flag that, when set, replaces the
stack-arrays and memory-allocation-opt passes in the default FIR optimizer
pipeline with the unified allocation-placement pass. The flag is off by
default, so the legacy passes remain the default path and behavior is
unchanged.

When enabled, the pass runs with its default byte-size thresholds; the
-fstack-arrays strategy is forwarded through the new stackArrays option.
https://invent.kde.org/qt/clang/llvm/-/commit/fe44e4902ff39e129b69d0704da1dfb93318d9ba