[PATCH] Use vec::reserve before vec_safe_grow_cleared is called

[Jan Hubicka]

> It runs for me in:
> 
> $ time ./a.out 1000000000
> 
> real	0m10.048s
> user	0m9.742s
> sys	0m0.305s

Did you do chroot to the chromium build?
> 
> Note that there may be an interleaving load on the machine.
> Perf says:
> 
>     55.40%  a.out    libc-2.26.so      [.] realloc
>     36.01%  a.out    a.out             [.] realloc@plt
>      4.98%  a.out    libc-2.26.so      [.] mremap_chunk
>      3.60%  a.out    a.out             [.] main

How one can do perfing on kunlun?
> 
> while on my machine I see:
> 
> real	0m4.998s
> user	0m4.947s
> sys	0m0.050s
> 
>     54.49%  a.out    libc-2.31.so      [.] realloc
>     37.63%  a.out    libc-2.31.so      [.] mremap_chunk
>      3.72%  a.out    a.out             [.] realloc@plt

Honza
> 
> Martin
> 
> > 
> > GDB stops at:
> > (gdb) bt
> > #0  0x00007ffff7e70bfe in realloc () from /lib/x86_64-linux-gnu/libc.so.6
> > #1  0x00005555555550bf in main ()
> > on debian while:
> > (gdb) bt
> > #0  0x00007ffff7e7d6d0 in mem2mem_check () from /lib64/libc.so.6
> > #1  0x00007ffff7e81c7d in realloc_check () from /lib64/libc.so.6
> > #2  0x00005555555550bf in main ()
> > on kunlun.
> > 
> > Perhaps someone enabled some cool security harnessing feature without
> > much of benchmarking :) (but even debian numbers seems like they can be
> > improved)
> > 
> > Honza
> > > 
> > > Martin
> > > 
> > > > 
> > > > Honza
> > > > > 
> > > > > Martin
> > > 
>