[llvm-dev] Slow debugger starts of LLVM tools

Zachary Turner via llvm-dev llvm-dev at lists.llvm.org
Wed Jan 9 18:17:10 PST 2019

This is admittedly a longshot, but Can you check whether you experience
unusually long run times with LLDB? If there’s something strange about tge
binaries we generate, maybe lldb will exhibit some strangeness too and we
can more easily profile it.
On Wed, Jan 9, 2019 at 2:48 PM Shoaib Meenai via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> I don't know about the issues with running being slow, but using a GDB
> index greatly speeds up initial symbol loading. Compile with
> `-ggnu-pubnames` and link with `-Xlinker --gdb-index` and you should get
> significantly faster symbol load times. (I'd be curious to see if it helps
> with the issues with run being slow as well.)
> On 1/9/19, 2:07 PM, "llvm-dev on behalf of David Greene via llvm-dev" <
> llvm-dev-bounces at lists.llvm.org on behalf of llvm-dev at lists.llvm.org>
> wrote:
>     David Jones via llvm-dev <llvm-dev at lists.llvm.org> writes:
>     > GDB likes to load all symbols from shared libraries up front. And on
>     > x86_64 your main executable is really just another shared library.
>     Yes, but does gdb reload everything on each execution?  Every time I
>     execute "run" I see the same slow behavior.  Loading the symbols for
>     small tools like llvm-rc takes hardly any time at all (i.e. "file
>     llvm-rc" is almost instantaneous).  But executing it causes gdb to chew
>     up CPU cycles for a while.  Every time.
>                              -David
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