[all-commits] [llvm/llvm-project] 3ddd1f: [SCEV] Don't invalidate past dependency-breaking i...

[Nikita Popov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 3ddd1ffb721dd0ac3faa4a53c76b6904e862b7ab
      https://github.com/llvm/llvm-project/commit/3ddd1ffb721dd0ac3faa4a53c76b6904e862b7ab
  Author: Nikita Popov <npopov at redhat.com>
  Date:   2023-04-28 (Fri, 28 Apr 2023)

  Changed paths:
    M llvm/lib/Analysis/ScalarEvolution.cpp

  Log Message:
  -----------
  [SCEV] Don't invalidate past dependency-breaking instructions

When invalidating a value, we walk all users of that value and
invalidate them as well. This can be very expensive for large use
graphs.

However, we only need to invalidate a user U of instruction I if
SCEV(U) can depend on SCEV(I). This is not the case if U is an
instruction that always produces a SCEVUnknown, such as a load.
If the load pointer operand is invalidated, there is no need to
invalidate the load result, which is completely unrelated from a
SCEV perspective.

Differential Revision: https://reviews.llvm.org/D149323