[all-commits] [llvm/llvm-project] 8e6d92: [DAG][PowerPC] Fix dropped `nsw` flag in `Simplify...

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  Branch: refs/heads/temp-test-main
  Home:   https://github.com/llvm/llvm-project
  Commit: 8e6d92026c624386b85675a4664e2666225fcfac
      https://github.com/llvm/llvm-project/commit/8e6d92026c624386b85675a4664e2666225fcfac
  Author: Kai Luo <lkail at cn.ibm.com>
  Date:   2020-11-25 (Wed, 25 Nov 2020)

  Changed paths:
    M llvm/include/llvm/CodeGen/SelectionDAG.h
    M llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
    M llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
    M llvm/test/CodeGen/PowerPC/setcc-sub-flag.ll

  Log Message:
  -----------
  [DAG][PowerPC] Fix dropped `nsw` flag in `SimplifySetCC` by adding `doesNodeExist` helper

`SimplifySetCC` invokes `getNodeIfExists` without passing `Flags` argument and `getNodeIfExists` uses a default `SDNodeFlags` to intersect the original flags, as a consequence, flags like `nsw` is dropped. Added a new helper function `doesNodeExist` to check if a node exists without modifying its flags.

Reviewed By: #powerpc, nemanjai

Differential Revision: https://reviews.llvm.org/D89938