Current user_id_t format is:
63{isDebugTypes} 62..32{dwo || 7fffffff}
31..0 {die_offset}
while current DIERef format is (I have made up the bit positions but the
field widths do match):
63{m_section==isDebugTypes} 62{m_dwo_num_valid} 61..32{m_dwo_num}
31..0 {m_die_offset}
Proposing to change user_id_t to:
63{isDebugTypes} 62{dwo_is_valid} 61..32{dwo; 0 if !valid}
31..0 {die_offset}
There is no benefit of having 31-bits wide dwo_num in user_id_t when it
gets converted to 30-bits width in DIERef.
This patch is for future DWZ patchset which extends the dwo_is_valid bit
into a 2-bit field (normal, DWO, DWZ, DWZcommon) so that both user_id_t
and DIERef can be changed then the same way.
It would be best to somehow unify user_id_t and DIERef but I do not plan
to do that. user_id_t should probably remain a number for the Python API
compatibility while there still needs to be some class with all the
methods to access it.
SymbolFileDWARF::GetDwpSymbolFile() and SymbolFileDWARF::GetDIE use
0x3fffffff for DWP but that does not clash:
formerly:
31bits32..62:0x7fffffff = normal unit / not any DWO
31bits32..62:0x3fffffff = DWP
31bits32..62:others = DWO unit number
after this patch:
bit62=0 30bits32..61:any = normal unit / not any DWO
bit62=1 30bits32..61:0x3fffffff = DWP
bit62=1 30bits32..61:others = DWO unit number
Differential Revision: https://reviews.llvm.org/D90413
In DWARF5 DW_AT_low_pc (and DW_AT_entry_pc, and possibly others) can use
DW_FORM_addrx to refer to the address indirectly. This means we need to
have processed the DW_AT_addr_base attribute before we can do anything
with these.
Since we were processing the unit attributes serially, this created a
problem in cases where the DW_AT_addr_base comes after DW_AT_low_pc --
we would end up computing the wrong unit base address, which also
corrupted any values which later depended on that (for instance range
lists). Clang currently always emits DW_AT_addr_base last.
The fix is simple -- process DW_AT_addr_base first, regardless of its
position in the attribute list.
