linux-kernel - Re: [PATCH 3/4] KVM-S390: Less function calls in kvm_s390_import_bp

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Message-ID: <57711295-6c3c-c2f3-41e3-a85a552de82b@redhat.com>
Date:   Wed, 31 Aug 2016 14:29:41 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     SF Markus Elfring <elfring@...rs.sourceforge.net>,
        Cornelia Huck <cornelia.huck@...ibm.com>
Cc:     kvm@...r.kernel.org, linux-s390@...r.kernel.org,
        Christian Bornträger <borntraeger@...ibm.com>,
        David Hildenbrand <dahi@...ux.vnet.ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org,
        Julia Lawall <julia.lawall@...6.fr>
Subject: Re: [PATCH 3/4] KVM-S390: Less function calls in
 kvm_s390_import_bp_data() after error detection



On 22/08/2016 23:17, SF Markus Elfring wrote:
>> If in doubt, the compiler will be _much_ better at optimizing
>> that kind of stuff anyway.
> 
> Which compiler (or optimizer) implementation is capable to restructure
> the jump targets for you automatically in the way I propose here?

If kfree were implemented as

	if (p)
		really_kfree(p);

then the compiler would be able to jump over the NULL test.  In
principle one could also add a "does nothing if NULL" attribute to GCC
and annotate kfree with it.

Paolo