[PATCH] D133926: [DebugInfo] Allow non-stack_value variadic expressions and use in DBG_INSTR_REF

[Felipe de Azevedo Piovezan via Phabricator via llvm-commits]

fdeazeve added a comment.

> I'll take a quick look - off the top of my head, there should be an interface to treat `!DIExpression(DW_OP_LLVM_arg, 0, <ops>)` identically to `!DIExpression(<ops>)`, and if it either doesn't exist or is only applicable to specific cases then it should be created/generalized.

Thank you!

>> Also note that the `CodeGen/AsmPrinter/DwarfExpression.cpp` code for `DwarfExpression::addExpression` doesn't expect an EntryValue as anything but the first operand of the op list.

I think the problem here is that, inside `DwarfCompileUnit::constructVariableDIEImpl`, we are now taking the *variadic path* which ends up calling addExpression.
More concretely, inside that function we have:

  if (auto *DVal = DV.getValueLoc()) {
    if (!DVal->isVariadic()) {

We are taking the else path of that second if, i.e., we are treating things as variadic where we before we wouldn't?

  (lldb) p DV.getValueLoc()->isVariadic()
  (bool) $2 = true
  (lldb) p DV.getValueLoc()->dump()
  Loc = { reg=134 } !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_entry_value, 1, DW_OP_plus_uconst, 16, DW_OP_plus_uconst, 16, DW_OP_deref, DW_OP_deref)

Because of this, we end calling `DwarfExpression::addExpression`, which crashes for that example because it doesn't expect an entry value.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D133926/new/

https://reviews.llvm.org/D133926