Re: FRE may run out of memory

[Andrew Pinski <pinskia@gmail.com>]

On Fri, Feb 7, 2014 at 11:29 PM, dxq <ziyan01@163.com> wrote:
> hi all,
>
> We found that gcc would run out of memory on Windows when compiling a *big*
> function (100000 lines).

My suggestion to you is file a bug to http://gcc.gnu.org/bugzilla with
the preprocessed source.  Also with the exact version of GCC you have
tried.  There have been some improvements with the extreme testcases;
at least on the trunk of GCC sources.

Thanks,
Andrew Pinski

>
> More investigation shows that gcc crashes at the function *compute_avail*,
> in tree-fre pass.  *compute_avail* collects information from basic blocks,
> so memory is allocated to record informantion.
> However, if there are huge number of basic blocks,  the memory would be
> exhausted and gcc would crash down, especially for Windows PC, only 2G or 4G
> memory generally. It's ok On linux, and *compute_avail* allocates *2.4G*
> memory. I guess some optimization passes in gcc like FRE didn't consider the
> extreme
> case.
>
> When disable tree-fre pass, gcc crashes at IRA pass.  I will do more
> investigation about that.
>
> Any suggestions?
>
> Thanks!
>
> danxiaoqiang
>
>
>
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