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Re: [Patch]Extend GAS arm_feature_set struct to provide more available bits
- From: pinskia at gmail dot com
- To: Terry Guo <flameroc at gmail dot com>
- Cc: Nicholas Clifton <nickc at redhat dot com>, Alan Modra <amodra at gmail dot com>, "binutils at sourceware dot org" <binutils at sourceware dot org>, Richard Earnshaw <Richard dot Earnshaw at arm dot com>, Ramana Radhakrishnan <ramana dot radhakrishnan at arm dot com>
- Date: Mon, 23 Mar 2015 23:35:48 -0700
- Subject: Re: [Patch]Extend GAS arm_feature_set struct to provide more available bits
- Authentication-results: sourceware.org; auth=none
- References: <007001d0572b$922edf60$b68c9e20$ at arm dot com> <54FECF9B dot 9010602 at redhat dot com> <CAGbRaL6Ypk7U1Tr8RW2atLjA6A+7N2+sEz6j-M7b4BME_4asjw at mail dot gmail dot com> <20150316074237 dot GC12856 at bubble dot grove dot modra dot org> <CAGbRaL6HiBoESpiwXAmQ3WVSKgKfii=QPRzr9k5YqDtVjAMt-w at mail dot gmail dot com> <20150316114857 dot GE12856 at bubble dot grove dot modra dot org> <CAGbRaL6SPjtQbcf=aB3MDyojN8dGo7U2AXE8p6ady=JZHnH5XA at mail dot gmail dot com>
> On Mar 16, 2015, at 7:22 PM, Terry Guo <flameroc@gmail.com> wrote:
>
>> On Mon, Mar 16, 2015 at 7:48 PM, Alan Modra <amodra@gmail.com> wrote:
>>> On Mon, Mar 16, 2015 at 04:27:04PM +0800, Terry Guo wrote:
>>>> On Mon, Mar 16, 2015 at 3:42 PM, Alan Modra <amodra@gmail.com> wrote:
>>>>> On Mon, Mar 16, 2015 at 02:43:01PM +0800, Terry Guo wrote:
>>>>> I am also curious here. As you can see from below URL, the default
>>>>> mode for gcc 4.7 and 4.8 is still c90 which doesn't support long long.
>>>>
>>>> https://gcc.gnu.org/onlinedocs/gcc/Long-Long.html
>>>> Note "as an extension GCC supports them in C90 mode".
>>>
>>> Thanks Alan. So in your opinion can we say it is safe to use long long
>>> here? Will there be any other subtle performance issue if we use long
>>> long?
>>
>> I was really just replying to your comments about gcc and C90.
>> I don't want to get into a stoush with the ARM maintainers. :)
>> But now that I've looked at your patch, I'd be inclined to
>> #include "bfd_stdint.h" and use uint64_t for the bitmask.
>>
>> --
>
> Hi Alan, thanks for your comments.
>
> Hi Alan and Nick, I noticed that GDB now can be built with g++
> https://sourceware.org/ml/gdb-patches/2015-03/msg00194.html. Is there
> any plan to build whole binutils with g++? If so, I am thinking that
> maybe I can use c++ bitset to handle those arm feature stuff which
> should be more flexible and clean.
Also c++ bitset is very inefficient for a few bits. If anything sbitmap or bitmap that is part of gcc is much better are more efficient. One of them (can't remember which one off hand) is a fixed size bitmask.
Thanks,
Andrew
>
> BR,
> Terry