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Re: FRE may run out of memory
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: dxq <ziyan01 at 163 dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Sat, 8 Feb 2014 15:47:45 +0100
- Subject: Re: FRE may run out of memory
- Authentication-results: sourceware.org; auth=none
- References: <1391844590227-1009578 dot post at n5 dot nabble dot com>
On Sat, Feb 8, 2014 at 8:29 AM, 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).
>
> 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.
This was fixed for GCC 4.8, FRE no longer uses compute_avail (but PRE
still does).
Basically GCC 4.8 should (at -O1) compile most extreme cases just fine.
Richard.
> 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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