[DebugInfo][CodeGenPrepare] Debug value loss caused by deleting the and instruction

[Apochens]

CodeGenPrepare pass deletes the and instruction without salvaging the debug value: https://godbolt.org/z/3d5f7v3oG

llvm-project/llvm/lib/CodeGen/CodeGenPrepare.cpp

Line 2274 in fa2a6d6

AndI->eraseFromParent();

IR before CodeGenPrepare:

entry:
  %and = and i32 %a, 4, !dbg !13
    #dbg_value(i32 %and, !9, !DIExpression(), !13)
  br i1 %c, label %bb0, label %bb2, !dbg !14

IR after CodeGenPrepare:

  entry:
      #dbg_value(i32 poison, !9, !DIExpression(), !11)
    br i1 %c, label %bb0, label %bb2, !dbg !12

I'd like to give a PR to fix it.

cc @OCHyams, could you please give me an example of how regression tests check the debug info in CodeGen? (I'm not very familiar with CodeGen...)

[llvmbot]

@llvm/issue-subscribers-debuginfo

Author: Shan Huang (Apochens)

CodeGenPrepare pass deletes the `and` instruction without salvaging the debug value: https://godbolt.org/z/3d5f7v3oG

llvm-project/llvm/lib/CodeGen/CodeGenPrepare.cpp

Line 2274 in fa2a6d6

AndI->eraseFromParent();

IR before CodeGenPrepare:

entry:
  %and = and i32 %a, 4, !dbg !13
    #dbg_value(i32 %and, !9, !DIExpression(), !13)
  br i1 %c, label %bb0, label %bb2, !dbg !14

IR after CodeGenPrepare:

  entry:
      #dbg_value(i32 poison, !9, !DIExpression(), !11)
    br i1 %c, label %bb0, label %bb2, !dbg !12

I'd like to give a PR to fix it.

cc @OCHyams, could you please give me an example of how regression tests check the debug info in CodeGen? (I'm not very familiar with CodeGen...)