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Re: [PATCH/RFC] Reduce call chain length in netfilter

To: "David S. Miller" <davem@xxxxxxxxxxxxx>
Subject: Re: [PATCH/RFC] Reduce call chain length in netfilter
From: Patrick McHardy <kaber@xxxxxxxxx>
Date: Thu, 27 Jan 2005 23:48:04 +0100
Cc: bdschuym@xxxxxxxxxx, netdev@xxxxxxxxxxx, netfilter-devel@xxxxxxxxxxxxxxxxxxx, snort2004@xxxxxxx, rusty@xxxxxxxxxxxxxxx, ak@xxxxxxx, bridge@xxxxxxxx, gandalf@xxxxxxxxxxxxxx, dwmw2@xxxxxxxxxxxxx, shemminger@xxxxxxxx
In-reply-to: <20050127114726.2205b4ed.davem@xxxxxxxxxxxxx>
References: <1131604877.20041218092730@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> <p73zn0ccaee.fsf@xxxxxxxxxxxxx> <1105117559.11753.34.camel@xxxxxxxxxxxxxxxxxxxxxxx> <20050107100017.454ddadc@xxxxxxxxxxxxxxxxx> <1105133241.3375.16.camel@xxxxxxxxxxxxxxxxxxxxx> <20050118135735.4b77d38d.davem@xxxxxxxxxxxxx> <1106433059.4486.11.camel@xxxxxxxxxxxxxxxxxxxxx> <1106436153.20995.42.camel@xxxxxxxxxxxxxx> <1106484019.3376.5.camel@xxxxxxxxxxxxxxxxxxxxx> <1106496509.1085.1.camel@xxxxxxxxxxxxxx> <20050125220558.6e824f8a.davem@xxxxxxxxxxxxx> <1106730510.4041.4.camel@xxxxxxxxxxxxxxxxxxxxx> <41F82C6D.7020006@xxxxxxxxx> <20050126231801.7bf90338.davem@xxxxxxxxxxxxx> <41F929FA.3050800@xxxxxxxxx> <20050127114726.2205b4ed.davem@xxxxxxxxxxxxx>
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David S. Miller wrote:

In the generated asm on sparc64, invoke2() gets a tail-call
whereas invoke() does not.  Hmmm...


Apparently support for indirect tail-calls was added to gcc 3.4.

gcc-3.3.5:
0x0000000000000000 <invoke+0>:  sub    $0x8,%rsp
0x0000000000000004 <invoke+4>:  callq  *%esi
0x0000000000000006 <invoke+6>:  add    $0x8,%rsp
0x000000000000000a <invoke+10>: retq
gcc-3.4.4:
0x0000000000000000 <invoke+0>:  mov    %rsi,%r11
0x0000000000000003 <invoke+3>:  jmpq   *%r11d

Regards
Patrick


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