[PATCH] DebugInfo: SROA on references should result in undef dbg.values

[Adrian Prantl]

I've been wishing for a DW_OP_addr_of before. But, I was just browsing through the DWARF spec and came across:

DW_OP_stack_value
The DW_OP_stack_value operation specifies that the object does not exist in memory but its value is nonetheless known and is at the top of the DWARF expression stack. In this form of location description, the DWARF expression represents the actual value of the object, rather than its location. The DW_OP_stack_value operation terminates the expression.

This *could* be interpreted as the DW_OP_addr_of we're looking for. 

I set aside some time this week to experiment with moving the complex expression part of DIVariable into an additional operand of dbg.value. My main motivation is reducing the memory footprint of OpPiece exprs. This will be a massive refactoring, but I'll keep you updated on how that goes.

http://reviews.llvm.org/D3714