[all-commits] [llvm/llvm-project] 121bab: [SelectionDAG] Don't remove unused negated constan...

[Qiu Chaofan via All-commits]

  Branch: refs/heads/release/11.x
  Home:   https://github.com/llvm/llvm-project
  Commit: 121babae56e9f08acedf3d6d44757e35556d0a37
      https://github.com/llvm/llvm-project/commit/121babae56e9f08acedf3d6d44757e35556d0a37
  Author: Qiu Chaofan <qiucofan at cn.ibm.com>
  Date:   2020-10-06 (Tue, 06 Oct 2020)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
    M llvm/test/CodeGen/X86/pr47517.ll

  Log Message:
  -----------
  [SelectionDAG] Don't remove unused negated constant immediately

This reverts partial of a2fb5446 (actually, 2508ef01) about removing
negated FP constant immediately if it has no uses. However, as discussed
in bug 47517, there're cases when NegX is folded into constant from
other places while NegY is removed by that line of code and NegX is
equal to NegY. In these cases, NegX is deleted before used and crash
happens. So revert the code and add necessary test case.

(cherry picked from commit b326d4ff946d2061a566a3fcce9f33b484759fe0)