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Re: ARMv8, GCC 4.9 and necessary code optimized away?
- From: Jeffrey Walton <noloader at gmail dot com>
- To: Andrew Haley <aph at redhat dot com>
- Cc: "gcc-help at gcc dot gnu dot org" <gcc-help at gcc dot gnu dot org>
- Date: Wed, 1 Jun 2016 05:36:16 -0400
- Subject: Re: ARMv8, GCC 4.9 and necessary code optimized away?
- Authentication-results: sourceware.org; auth=none
- References: <CAH8yC8=KPf7edhTRgKV4nVJfwMpSXwmU+PDGfL6i4xA4SDwJwQ at mail dot gmail dot com> <574D89F2 dot 70108 at foss dot arm dot com> <CAH8yC8m0p+N2duSKcBMo4TKFrMwo6Ed+j+Frt2SjT=ZBR14CPA at mail dot gmail dot com> <574E8F75 dot 6020805 at redhat dot com> <CAH8yC8kz4-+UYciiDiQx+X0O9VBkrN21FNQHdcrPygLgmGVdqA at mail dot gmail dot com> <574E9E3F dot 3080507 at redhat dot com>
- Reply-to: noloader at gmail dot com
>> ...
>>
>> An statement to test for the presence of an instruction is only code.
>
> This is a mistake by the programmer. To test for the presence of an
> instruction, they need to emit the instruction. Asm statements do
> that.
Thanks Andrew. Doesn't the intrinsic do that?
ARM instrinsics are very appealing for us. They work on Linux,
Android, iOS, Windows Phone, Windows Store, and Aarch32 on Aarch64.
(I want to ensure I'm not wandering into unwanted or unseen side effects).
Jeff