[all-commits] [llvm/llvm-project] ea5f74: [CodeGen] Move rollback capabilities outside of th...

[Lucas Ramirez via All-commits]

  Branch: refs/heads/users/lucas-rami/rematerializer-rollback-listener
  Home:   https://github.com/llvm/llvm-project
  Commit: ea5f742d2d4cfd3ec6223268be9c83ce7fccdd5f
      https://github.com/llvm/llvm-project/commit/ea5f742d2d4cfd3ec6223268be9c83ce7fccdd5f
  Author: Lucas Ramirez <lucas.rami at proton.me>
  Date:   2026-03-24 (Tue, 24 Mar 2026)

  Changed paths:
    M llvm/include/llvm/CodeGen/Rematerializer.h
    M llvm/lib/CodeGen/Rematerializer.cpp
    M llvm/unittests/CodeGen/RematerializerTest.cpp

  Log Message:
  -----------
  [CodeGen] Move rollback capabilities outside of the rematerializer

The rematerializer implements support for rolling back
rematerializations by modifying MIs that should normally be deleted in
an attempt to make them "transparent" to other analyses. This involves:

1. setting their opcode to DBG_VALUE and
2. setting their read register operands to the sentinel register.

This approach has several drawbacks.

1. It forces the rematerializer to support tracking these "dead MIs".
2. It is not actually clear whether this mechanism will interact well
   with all other analyses. This is an issue since the intent of the
   rematerializer is to be usable in as many contexts as possible.
3. In practice, it has shown itself to be relatively error-prone.

This commit removes rollback support from the rematerializer and moves
those capabilties to a rematerializer listener than can be instantiated
on-demand and implements the same functionnality on top of standard
rematerializer operations. The rematerializer now actually deletes MIs
that are no longer useful after rematerializations, and has support for
re-creating them on-demand without requiring additional tracking on its
part.



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