Messages in this thread | | | From | Andy Lutomirski <> | Date | Tue, 3 Jan 2017 10:35:15 -0800 | Subject | Re: [PATCH 1/2] x86/CPU: Add native CPUID variants returning a single datum |
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On Sat, Dec 31, 2016 at 3:09 AM, Borislav Petkov <bp@alien8.de> wrote: > On Fri, Dec 30, 2016 at 06:13:24PM -0800, Andy Lutomirski wrote: >> Now you call it and ignore the return value and the compiler optimizes >> it out :) > > Does it, really? > > It is an inlined asm volatile. I checked all call sites and the CPUID > call is there. gcc 6 simply issues the CPUID and then later code > overwrites rAX. I.e., it looks ok to me. > > Or what example scenario do you have in mind?
That's why I didn't type "volatile". :)
> >> Also, someone reading the code might scratch their head and >> wonder why you picked eax and not ebx, ecx, or edx. > > We have comments for her/him :-)
Okay. Anyway, this particular nit is minor and I'll shut up.
> > -- > Regards/Gruss, > Boris. > > ECO tip #101: Trim your mails when you reply. > --
-- Andy Lutomirski AMA Capital Management, LLC
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