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Re: wide-int, ada
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: Andrew Pinski <pinskia at gmail dot com>, Richard Earnshaw <rearnsha at arm dot com>, Eric Botcazou <ebotcazou at adacore dot com>, Kenneth Zadeck <zadeck at naturalbridge dot com>, "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, Mike Stump <mikestump at comcast dot net>
- Date: Tue, 26 Nov 2013 15:16:12 +0100
- Subject: Re: wide-int, ada
- Authentication-results: sourceware.org; auth=none
- References: <0075C6DB-B432-4E6F-8A48-3AE0C4D842FE at comcast dot net> <1464599 dot QpNUskFgRu at polaris> <5293FE59 dot 6090801 at naturalbridge dot com> <14902105 dot e0dHrA5yuq at polaris> <5294A5AF dot 4080803 at arm dot com> <CAFiYyc0hWZh+9xZd7po=KdhLm2a=jtqfHDnrdPJoqE9+cBmGkQ at mail dot gmail dot com> <CAMe9rOqhkzwRaLTtH2+oxKUEoNJ+1B2pRrwgUJ39LM=vQ1hP+g at mail dot gmail dot com> <AD249CE6-A0C0-484D-B796-14129FC9C5B2 at gmail dot com> <CAMe9rOr_vOcRWuh4c0kfv0egNzv1GBdGqfV+ytwBA0Uw78CYMQ at mail dot gmail dot com>
On Tue, Nov 26, 2013 at 3:15 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Tue, Nov 26, 2013 at 6:03 AM, <pinskia@gmail.com> wrote:
>>
>>
>>> On Nov 26, 2013, at 6:00 AM, "H.J. Lu" <hjl.tools@gmail.com> wrote:
>>>
>>> On Tue, Nov 26, 2013 at 5:55 AM, Richard Biener
>>> <richard.guenther@gmail.com> wrote:
>>>> On Tue, Nov 26, 2013 at 2:44 PM, Richard Earnshaw <rearnsha@arm.com> wrote:
>>>>> On 26/11/13 09:18, Eric Botcazou wrote:
>>>>>>> you are correct - this was an incorrect change. I believe that the
>>>>>>> patch below would be correct, but it is impossible to test it because (i
>>>>>>> believe) that gcc no longer works if the host_bits_per_wide_int is 32.
>>>>>>> I could be wrong about this but if i am correct, what do you want me to do?
>>>>>>
>>>>>> While you're right that most mainstream architectures now require a 64-bit
>>>>>> HWI, not all of them do according to config.gcc, so I don't think that this
>>>>>> path is entirely dead yet. I'll carry out the testing once we agree on the
>>>>>> final change.
>>>>>
>>>>> I'm hoping, once this patch series is in that we might be able to
>>>>> migrate the ARM port back to supporting a 32-bit HWI. The driving
>>>>> factor behind the original switch was supporting 128-bit constants for
>>>>> Neon and these patches should resolve that.
>>>>
>>>> i?86 would be another candidate (if you don't build a compiler with -m64
>>>> support).
>>>
>>> Not true for x86 since we have
>>>
>>> Variable
>>> HOST_WIDE_INT ix86_isa_flags = TARGET_64BIT_DEFAULT |
>>> TARGET_SUBTARGET_ISA_DEFAULT
>>>
>>> in i386.opt. We need more than 32 bits for ix86_isa_flags.
>>
>> Then that should be HOST_WIDEST_INT instead.
>>
>
> Also one function in i386.c generates less optimal
> results when HOST_WIDE_INT is 32-bit such that
> we were generating different outputs from the same
> input on x86 and on x86-64 with -m32.
Well - we knew the code would bitrot once we decided to always
default to 64bit HWI ...
Richard.
> --
> H.J.