We received a bug report where someone was trying to print a global
variable without a process. This would succeed in a debug build but fail
in a on optimized build. We traced the issue back to the location being
described by a DW_OP_addr + DW_OP_piece.
The issue is that the DWARF expression evaluator only support reading
pieces from a load address. There's no reason it cannot do the same for
a file address, and indeed, that solves the problem.
I unsuccessfully tried to craft a test case to illustrate the original
example, using a global struct and trying to trick the compiler into
breaking it apart with SROA. Instead I wrote a unit test that uses a
mock target to read memory from.
rdar://127435923
7dc84e225e