libpfm4 faults on P4 machine

[Lin Ming <ming.m.lin@intel.com>]

On P4 machine, intel_x86_arch_support.get_event_info(...) faults because
intel_x86_arch_support.pe is NULL.

intel_x86_arch_support.pe is set at run time, but P4 does not have arch
event support, so intel_x86_arch_support.pe is always NULL.

#gdb libpfm4/examples/check_events

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xb785caf0 (LWP 3950)]
0x0804d74b in pfm_intel_x86_get_event_info (this=0x81c5f80, idx=0, info=0xbff45f14)
    at pfmlib_intel_x86.c:667
667		info->desc  = pe[idx].desc;
(gdb) bt
#0  0x0804d74b in pfm_intel_x86_get_event_info (this=0x81c5f80, idx=0, info=0xbff45f14)
    at pfmlib_intel_x86.c:667
#1  0x08049cd3 in pfmlib_parse_event (event=0x804fb7b "PERF_COUNT_HW_CPU_CYCLES", d=0xbff45f7c)
    at pfmlib_common.c:676
#2  0x08049f3f in pfm_get_event_encoding (str=0x804fb7b "PERF_COUNT_HW_CPU_CYCLES", dfl_plm=8, 
    fstr=0xbff464d4, idx=0xbff464c8, codes=0xbff464d0, count=0xbff464cc) at pfmlib_common.c:877
#3  0x08048dc1 in main (argc=<value optimized out>, argv=0xbff46584) at check_events.c:118
(gdb) list
662	
663		/*
664		 * pmu and idx filled out by caller
665		 */
666		info->name  = pe[idx].name;
667		info->desc  = pe[idx].desc;
668		info->code  = pe[idx].code;
669		info->equiv = pe[idx].equiv;
670	
671		/* unit masks + modifiers */
(gdb)

Any fix?

Lin Ming