[llvm-dev] Slow debugger starts of LLVM tools

Roman Lebedev via llvm-dev llvm-dev at lists.llvm.org
Wed Jan 9 13:32:58 PST 2019

On Thu, Jan 10, 2019 at 12:28 AM David Greene via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> I'm wondering if anyone else is running into this problem.
> When I do a Debug build and attempt to run a tool (opt, llvm-dis,
> whatever) in gdb, the program takes a LOOOOONG time to begin executing.
> Loading the executable into gdb is not the problem.  I type "run" and
> the debugger sits there for many seconds and then things start going.
> gdb emits no messages indicating what it is doing but it's basically
> using 100% CPU.
I do see such perf issues, although i *think* for me they happen
when initially loading the executable in gdb, and the 'run' itself works fast.

> I'm wondering if this is an artifact of the gdb I'm using (buggy?) or
> something inherent to the way LLVM tools are built.  I see the same slow
> operation across different versions of gdb and I do not see the same
> slow operation with other executables.
It probably has the same source as the Release vs Debug filesize -
debug info for LLVM is *big*.
(It would be interesting to know if there is a solution, other than
using lldb of course.)

>                          -David

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