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Groups > linux.kernel > #1398428
| From | "H. Peter Anvin" <hpa@zytor.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH -v2] x86/hweight: Get rid of the special calling convention |
| Date | 2016-05-10 21:10 +0200 |
| Message-ID | <rxlcD-uF-29@gated-at.bofh.it> (permalink) |
| References | (6 earlier) <rvbAK-2kO-19@gated-at.bofh.it> <rvrcu-B8-23@gated-at.bofh.it> <rvs8y-1oa-27@gated-at.bofh.it> <rxjaP-6ly-9@gated-at.bofh.it> <rxjDP-75T-1@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On May 10, 2016 10:23:13 AM PDT, Peter Zijlstra <peterz@infradead.org> wrote:
>On Tue, May 10, 2016 at 06:53:18PM +0200, Borislav Petkov wrote:
>> static __always_inline unsigned int __arch_hweight32(unsigned int w)
>> {
>> - unsigned int res = 0;
>> + unsigned int res;
>>
>> - asm (ALTERNATIVE("call __sw_hweight32", POPCNT32,
>X86_FEATURE_POPCNT)
>> - : "="REG_OUT (res)
>> - : REG_IN (w));
>> + if (likely(static_cpu_has(X86_FEATURE_POPCNT))) {
>> + /* popcnt %eax, %eax */
>> + asm volatile(POPCNT32
>> + : "="REG_OUT (res)
>> + : REG_IN (w));
>>
>> - return res;
>> + return res;
>> + }
>> + return __sw_hweight32(w);
>> }
>
>So what was wrong with using the normal thunk_*.S wrappers for the
>calls? That would allow you to use the alternative() stuff which does
>generate smaller code.
Also, to be fair... if the problem is with these being in C then we could just do it in assembly easily enough.
--
Sent from my Android device with K-9 Mail. Please excuse brevity and formatting.
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[RFC PATCH] x86/hweight: Get rid of the special calling convention Borislav Petkov <bp@suse.de> - 2016-05-04 20:50 +0200
Re: [RFC PATCH] x86/hweight: Get rid of the special calling convention Brian Gerst <brgerst@gmail.com> - 2016-05-04 21:40 +0200
Re: [RFC PATCH] x86/hweight: Get rid of the special calling convention "H. Peter Anvin" <hpa@zytor.com> - 2016-05-04 21:40 +0200
Re: [RFC PATCH] x86/hweight: Get rid of the special calling convention Borislav Petkov <bp@suse.de> - 2016-05-04 21:50 +0200
Re: [RFC PATCH] x86/hweight: Get rid of the special calling convention "H. Peter Anvin" <hpa@zytor.com> - 2016-05-04 22:00 +0200
Re: [RFC PATCH] x86/hweight: Get rid of the special calling convention Borislav Petkov <bp@suse.de> - 2016-05-04 22:30 +0200
Re: [RFC PATCH] x86/hweight: Get rid of the special calling convention "H. Peter Anvin" <hpa@zytor.com> - 2016-05-04 23:00 +0200
Re: [RFC PATCH] x86/hweight: Get rid of the special calling convention Andi Kleen <andi@firstfloor.org> - 2016-05-04 23:20 +0200
Re: [RFC PATCH] x86/hweight: Get rid of the special calling convention Denys Vlasenko <dvlasenk@redhat.com> - 2016-05-05 15:10 +0200
Re: [RFC PATCH] x86/hweight: Get rid of the special calling convention Borislav Petkov <bp@suse.de> - 2016-05-05 16:10 +0200
[PATCH -v2] x86/hweight: Get rid of the special calling convention Borislav Petkov <bp@suse.de> - 2016-05-10 19:00 +0200
Re: [PATCH -v2] x86/hweight: Get rid of the special calling convention Peter Zijlstra <peterz@infradead.org> - 2016-05-10 19:30 +0200
Re: [PATCH -v2] x86/hweight: Get rid of the special calling convention "H. Peter Anvin" <hpa@zytor.com> - 2016-05-10 21:10 +0200
Re: [PATCH -v2] x86/hweight: Get rid of the special calling convention Borislav Petkov <bp@suse.de> - 2016-05-10 21:20 +0200
Re: [PATCH -v2] x86/hweight: Get rid of the special calling convention "H. Peter Anvin" <hpa@zytor.com> - 2016-05-11 00:40 +0200
Re: [PATCH -v2] x86/hweight: Get rid of the special calling convention Borislav Petkov <bp@suse.de> - 2016-05-11 06:20 +0200
Re: [PATCH -v2] x86/hweight: Get rid of the special calling convention Brian Gerst <brgerst@gmail.com> - 2016-05-11 13:20 +0200
Re: [PATCH -v2] x86/hweight: Get rid of the special calling convention Peter Zijlstra <peterz@infradead.org> - 2016-05-11 13:30 +0200
Re: [PATCH -v2] x86/hweight: Get rid of the special calling convention Borislav Petkov <bp@suse.de> - 2016-05-11 14:50 +0200
Re: [PATCH -v2] x86/hweight: Get rid of the special calling convention "H. Peter Anvin" <hpa@zytor.com> - 2016-05-12 07:00 +0200
Re: [PATCH -v2] x86/hweight: Get rid of the special calling convention Borislav Petkov <bp@suse.de> - 2016-05-12 14:00 +0200
Re: [PATCH -v2] x86/hweight: Get rid of the special calling convention Peter Zijlstra <peterz@infradead.org> - 2016-05-12 14:20 +0200
Re: [PATCH -v2] x86/hweight: Get rid of the special calling convention Borislav Petkov <bp@suse.de> - 2016-05-10 21:10 +0200
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