Peter Collingbourne 75bb30ddbf
Move {load,store}(llvm.protected.field.ptr) lowering to InstCombine.
The previous position of llvm.protected.field.ptr lowering for loads
and stores was problematic as it not only inhibited optimizations such
as DSE (as stores to a llvm.protected.field.ptr were not considered to
must-alias stores to the non-protected.field pointer) but also required
changes to other optimization passes to avoid transformations that would
reduce PFP coverage.

Address this by moving the load/store part of the lowering to
InstCombine, where it will run earlier than the PFP-breaking and
AA-relying transformations. The deactivation symbol, null comparison
and EmuPAC parts of the lowering remain in PreISelLowering.

Now that the transformation inhibitions are no longer needed, remove them
(i.e. partially revert #151649, and revert #182976).

This change resulted in a 2.4% reduction in Fleetbench .text size and
the following improvements to PFP performance overhead for BM_PROTO_Arena
on various microarchitectures:

                    before   after
  Apple M2 Ultra     3.5%    3.3%
  Google Axion C4A   3.3%    2.9%
  Google Axion N4A   2.7%    2.2%

Reviewers: fmayer, nikic, vitalybuka

Reviewed By: fmayer

Pull Request: https://github.com/llvm/llvm-project/pull/186548
2026-04-06 17:47:24 -07:00
..

This directory contains test cases for the instcombine transformation.  The
dated tests are actual bug tests, whereas the named tests are used to test
for features that the this pass should be capable of performing.