[all-commits] [llvm/llvm-project] 866646: [instcombine] Exploit UB implied by nofree attributes

[Philip Reames via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 86664638898e9c3756ad17d612de1873fead6813
      https://github.com/llvm/llvm-project/commit/86664638898e9c3756ad17d612de1873fead6813
  Author: Philip Reames <listmail at philipreames.com>
  Date:   2021-02-18 (Thu, 18 Feb 2021)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
    M llvm/test/Transforms/InstCombine/malloc-free-delete.ll

  Log Message:
  -----------
  [instcombine] Exploit UB implied by nofree attributes

This patch simply implements the documented UB of the current nofree attributes as specified. It doesn't try to be fancy about inference (yet), it just implements the cases already specified and inferred.

Note: When this lands, it may expose miscompiles. If so, please revert and provide a test case. It's likely the bug is in the existing inference code and without a relatively complete test case, it will be hard to debug.

Differential Revision: https://reviews.llvm.org/D96349