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Re: implementation question
- From: Daniel Gutson <daniel dot gutson at tallertechnologies dot com>
- To: Richard Biener <richard dot guenther at gmail dot com>
- Cc: Andrew Haley <aph at redhat dot com>, gcc Mailing List <gcc at gcc dot gnu dot org>
- Date: Fri, 9 May 2014 14:05:02 -0300
- Subject: Re: implementation question
- Authentication-results: sourceware.org; auth=none
- References: <CAF5HaEWgup1evKX=CLB0in6Eqe=Fd2pBoPPjMhMY6b3sLPk_UA at mail dot gmail dot com> <CAFiYyc2kFMbsWdzK25iypbA1jHnr5j=r61PcpacPZ-4J4JpnBQ at mail dot gmail dot com> <536759A7 dot 3040408 at redhat dot com> <CAFiYyc0A=7_Hn3tuGT+MG3Q=8ttQY=7cGc0fB7OxTzsxM6bYGw at mail dot gmail dot com>
On Mon, May 5, 2014 at 8:57 AM, Richard Biener
> On Mon, May 5, 2014 at 11:28 AM, Andrew Haley <firstname.lastname@example.org> wrote:
>> On 05/05/2014 08:47 AM, Richard Biener wrote:
>>> It really depends on how "3x" should materialize in the end.
>>> How do you triplicate ops with side-effects? If you only
>>> triplicate ops without side-effects what is the sink that keeps
>>> the duplicated ops live?
>> The vote, surely. CSE would be absolutely determined to get rid of
>> all this redundant work. I guess it'd all have to be done very late
>> or we'd need a new node that CSE can't see through.
>> Would it be enough to mark all nodes that go into the vote as volatile?
>> I guess not: we wouldn't want to generate extra memory traffic.
> Well, it can end up using the exact same registers 3 times and spilling
> the result to the stack anyway.
> It has to be done before register allocation I suppose, and thus
> postreload-cse will come along ...
Thanks for all your feedback guys.
Based on our experiments, we noted too many exposure in the stack frames,
so it seems that a hardened ABI should be considered (with redundancy and
All these facts lead to work on a specific RTL backend (e.g. hardened-x86,
Any more comment will be greatly appreciated.
Daniel F. Gutson
Chief Engineering Officer, SPD
San Lorenzo 47, 3rd Floor, Office 5
Phone: +54 351 4217888 / +54 351 4218211