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Re: [patch] Support 64-bit constants/enums on 32-bit host [Re: [PATCH] Allow 64-bit enum values]
- From: Tom Tromey <tromey at redhat dot com>
- To: Jan Kratochvil <jan dot kratochvil at redhat dot com>
- Cc: Siddhesh Poyarekar <siddhesh at redhat dot com>, gdb-patches at sourceware dot org
- Date: Tue, 17 Apr 2012 09:48:34 -0600
- Subject: Re: [patch] Support 64-bit constants/enums on 32-bit host [Re: [PATCH] Allow 64-bit enum values]
- References: <20120220132724.GB4753@spoyarek.pnq.redhat.com> <87d397syts.fsf@fleche.redhat.com> <20120229135148.GA32128@spoyarek.pnq.redhat.com> <20120301224428.GA30631@host2.jankratochvil.net> <20120305063542.GA30196@spoyarek.pnq.redhat.com> <20120305080512.GA12311@host2.jankratochvil.net> <20120321100630.GA14496@spoyarek.pnq.redhat.com> <20120417130833.GB15356@host2.jankratochvil.net> <20120417143219.GA25827@host2.jankratochvil.net> <87zkaav1i4.fsf@fleche.redhat.com> <20120417153202.GB27888@host2.jankratochvil.net>
>>>>> "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