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Re: Re: Why does gcc generate const local array on stack?
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: Jonathan Wakely <jwakely dot gcc at gmail dot com>
- Cc: lh_mouse <lh_mouse at 126 dot com>, Bingfeng Mei <bingfeng dot mei at broadcom dot com>, gcc <gcc at gcc dot gnu dot org>
- Date: Thu, 21 Apr 2016 12:15:37 +0200
- Subject: Re: Re: Why does gcc generate const local array on stack?
- Authentication-results: sourceware.org; auth=none
- References: <CAAvcwYdM4AR0JjN4pY=xndyYAmgLTQ8i54EzeUrj4L=wtGBAog at mail dot gmail dot com> <31a6f6bf dot e3788 dot 15434b9ee28 dot Coremail dot lh_mouse at 126 dot com> <CAH6eHdRbbAZodOqt0kyQHk51Xkb0fs8W7TRCkjaWXd4DPcZPSw at mail dot gmail dot com> <744b2890 dot e5490 dot 15436b1f476 dot Coremail dot lh_mouse at 126 dot com> <CAH6eHdTHsSddkFSo6NQGo5gP+ezn3oDwHfOqr73XDzBNym_rvw at mail dot gmail dot com>
On Thu, Apr 21, 2016 at 11:39 AM, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
> On 21 April 2016 at 03:41, lh_mouse wrote:
>> See this example: http://coliru.stacked-crooked.com/a/048b4aa5046da11b
>>
>> In this example the function is called recursively.
>
> See the original email you replied to:
>
> "I understand if this function is recursive and pointer of the array
> is involved, GCC would have to maintain the array on stack and hence
> the initialization."
>
> The question is about cases where that doesn't happen.
The decision on whether to localize the array and inline the init is
done at gimplification time.
The plan is to delay this until SRA which could then also apply the
desired optimization
of removing the local in case it is never written to.
Richard.