Alexander Dupuy wrote:
Note also that there is a bug in the libpcap BPF optimizer (as of 0.8.3) that breaks the hack described above,
Try it with the top-of-tree CVS version; I've made some optimizer fixes that will, I think, fix this.
However, the libpcap 0.7 optimizer not only generates correct BPF, but it is shorter than any of the above, entirely eliminating the use of the index register:
(000) ldh [12]
(001) jeq #0x800 jt 2 jf 6
(002) ld [26]
(003) jge #0x1020304 jt 4 jf 6
(004) jgt #0x1020506 jt 6 jf 5
(005) ret #96
(006) ret #0
I'm not sure whether that's a case of the code generator not generating code that uses the X register there, or a missing optimization - I have a change that should put that optimization back.
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