Hi,

I'm getting this error while trying to use valgrind to profile an application:

vex amd64->IR: unhandled instruction bytes: 0xF3 0xF 0xB8 0x4 0x11 0x48
==19771== valgrind: Unrecognised instruction at address 0xf728338.
==19771== Your program just tried to execute an instruction that Valgrind
==19771== did not recognise.  There are two possible reasons for this.
==19771== 1. Your program has a bug and erroneously jumped to a non-code
==19771==    location.  If you are running Memcheck and you just saw a
==19771==    warning about a bad jump, it's probably your program's fault.
==19771== 2. The instruction is legitimate but Valgrind doesn't handle it,
==19771==    i.e. it's Valgrind's fault.  If you think this is the case or
==19771==    you are not sure, please let us know and we'll try to fix it.
==19771== Either way, Valgrind will now raise a SIGILL signal which will
==19771== probably kill your program.

I get this error regardless of which program I am profiling and which valgrind tool I am using.

$ valgrind --version
valgrind-3.5.0
$ uname -a
Linux localhost 2.6.34-gentoo-r6 #1 SMP PREEMPT Sat Sep 11 21:04:31 EEST 2010 x86_64 Intel(R) Core(TM) i5 CPU 750 @ 2.67GHz GenuineIntel GNU/Linux

A response on the valgrind-developer mailing list of John Reiser states the following:
"
> cat /proc/cpuinfo on the cpu emulated since r2011 says
>
> flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca mov
> pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm
> constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf
> pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm
> sse4_1 sse4_2 popcnt aes lahf_lm ida arat tpr_shadow vnmi flexpriority ept
> vpid

Note that 'popcnt' is in the list [so is 'aes'.]  However, there is
no case for 0x0F 0xB8 in file VEX/priv/guest_x86_toIR.c.  Oops.
[It doesn't help that there is an "extra" 0xF3 prefix.]
"