the debug information individual Decls came from.
We've had a metadata infrastructure for a while,
which was intended to solve a problem we've since
dealt with in a different way. (It was meant to
keep track of which definition of an Objective-C
class was the "true" definition, but we now find
it by searching the symbols for the class symbol.)
The metadata is attached to the ExternalASTSource,
which means it has a one-to-one correspondence with
AST contexts.
I've repurposed the metadata infrastructure to
hold the object file and DIE offset for the DWARF
information corresponding to a Decl. There are
methods in ClangASTContext that get and set this
metadata, and the ClangASTImporter is capable of
tracking down the metadata for Decls that have been
copied out of the debug information into the
parser's AST context without using any additional
memory.
To see the metadata, you just have to enable the
expression log:
-
(lldb) log enable lldb expr
-
and watch the import messages. The high 32 bits
of the metadata indicate the index of the object
file in its containing DWARFDebugMap; I have also
added a log which you can use to track that mapping:
-
(lldb) log enable dwarf map
-
This adds 64 bits per Decl, which in my testing
hasn't turned out to be very much (debugging Clang
produces around 6500 Decls in my tests). To track
how much data is being consumed, I've also added a
global variable g_TotalSizeOfMetadata which tracks
the total number of Decls that have metadata in all
active AST contexts.
Right now this metadata is enormously useful for
tracking down bugs in the debug info parser. In the
future I also want to use this information to provide
more intelligent error messages instead of printing
empty source lines wherever Clang refers to the
location where something is defined.
llvm-svn: 154634
60217120b5