[PATCH] D114958: [SLP]Fix reused extracts cost.

[Qiongsi Wu via Phabricator via llvm-commits]

qiongsiwu1 added subscribers: RolandF, qiongsiwu1.
qiongsiwu1 added a comment.

This patch causes a crash when compiling the IR below.

  define dso_local void @foo() local_unnamed_addr {
  entry:
    %0 = extractelement <2 x double> undef, i32 1
    br label %loop_do_
  
  loop_do_:
    %a1 = phi double [ %a1, %loop_do_ ], [ %0, %entry ]
    %a2 = phi double [ undef, %loop_do_ ], [ undef, %entry ]
    br label %loop_do_
  }

The patch moved the `isSlat(VL)` check after we process `ExtractValue`, but this test case has a tree where one value is `undef`, and the other is an `extractvalue`. Should we match not only `isa<ExtractElementInst, UndefValue>(V)`, but also an undef value itself as well?

Thanks a lot! FYI @RolandF


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D114958/new/

https://reviews.llvm.org/D114958