[DebugInfo] Support for DW_OP_implicit_pointer (DW_OP_LLVM_implicit_pointer)

[alok]

Summary

This patch (2/N) stems from D69787
It is suggested by @aprantl

Summary:

New dwarf operator DW_OP_LLVM_implicit_pointer is introduced (present only in LLVM IR)
This is needed ecause representation and specification (types of operands) of it a bit different that actual dwarf expression DW_OP_LLVM_implicit_pointer. while creating actual dwarf info it will be converted to DW_OP_LLVM_implicit_pointer.

Testing:

• llvm-as, llvm-dis
• check-llvm
• check-debuginfo (the debug info integration tests)

[jmorse]

llvm/docs/LangRef.rst

4828–4829

IMHO, "variable represented by first operand" should become something like "the DILocalVariable referred to by the instructions value/address operand". This would make it clear that we're referring to a metadata node, and that the "first operand" is of the containing debug intrinsic, not a dwarf operators operand.

llvm/lib/IR/DebugInfoMetadata.cpp

909

Shouldn't this also check that the expression has the offset argument, and (as I understand it) no other elements?

[alok]

llvm/docs/LangRef.rst

4828–4829

Thanks for your comment. It will be incorporated in next version.

[alok]

Update includes comments from @jmorse.

[aprantl]

Can you please add an assembler round-trip test to test/IR that runs llvm-as | llvm-dis | llvm-as - | llvm-dis ? There are a bunch of examples in that directory.

[alok]

In D70643#1769810, @aprantl wrote:

Can you please add an assembler round-trip test to test/IR that runs llvm-as | llvm-dis | llvm-as - | llvm-dis ? There are a bunch of examples in that directory.

Thanks @aprantl for your suggestion. Next version would have a testcase. Though the actual test case would need some changes from future patches, I would work-around that to just test the round-trip. Test case would be updated in future patch as needed.

[alok]

Updated to re-base and include a test case as suggested by @aprantl.