[llvm] [DebugInfo] Lower DW_OP_LLVM_implicit_pointer to DWARF (PR #186763)

[Shivam Kunwar via llvm-commits]

phyBrackets wrote:

Hi @yonghong-song , This PR only covers the backend lowering, given IR that already contains `DW_OP_LLVM_implicit_pointer`, it correctly emits` DW_OP_implicit_pointer` in the DWARF output. The test uses hand-crafted IR for this reason.

No optimization pass emits `DW_OP_LLVM_implicit_pointer` today, `ArgumentPromotion` still poisons the debug uses. The producer-side change to `ArgumentPromotion` is planned as the next patch in the series, which will make clang -O3 -g produce it automatically for your reproducer. I am preparing a RFC for the same.

https://github.com/llvm/llvm-project/pull/186763