Re: [patch] Support 64-bit constants/enums on 32-bit host [Re: [PATCH] Allow 64-bit enum values]

Tom Tromey
2012-04-17T15:48:53Z

>>>>> "Jan" == Jan Kratochvil <jan.kratochvil@redhat.com> writes:

Tom> This idea would make lazy CU expansion a bit faster, because you
Tom> wouldn't have to re-scan the DIEs to make the symbol table.

Jan> I think this would be a win contrary to other disadvantages; I have
Jan> sure no technical arguments for that, other than accessing memory
Jan> outside of the CPU cache is terribly slow and several more bytes
Jan> are worth the acceleration.

Yeah, that makes sense to me.
Not scanning the .debug_info again seems like it could really win.

Tom> and as you pointed out on irc, the result will
Tom> still probably be slower than idb -- IOW, we're doing something really
Tom> wrong, so why not start by finding that?

Jan> BTW without making some big decisions one should do some more
Jan> serious test of idb, or at least to be tested by a second person, I
Jan> did just a quick test myself (that GDB is 800%-times slower even
Jan> with .gdb_index), I could make some mistakes and I even no longer
Jan> remember all the details how I specifically did the test.

Yeah, I'd like to get to it eventually.

One nice thing about the psymtab->symtab thought experiment is that I've
convinced myself that the problem, whatever it may be, can at least be
isolated down to dwarf2read.c. So, I feel it must be fixable without
excessive work on gdb.

Tom