libpmc: fix the 'cycles' event alias on x86

Looking for "tsc-tsc" in the pmu tables will fail every time. Instead,
make this an alias for the static TSC event defined in pmc_events.h.
This fixes 'pmcstat -s cycles' on Intel and AMD.

Reviewed by:	emaste
MFC after:	1 week
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D32197

lib/libpmc/libpmc.c

@@ -178,7 +178,7 @@ static const struct pmc_event_descr cortex_a76_event_table[] =
 
 static const struct pmc_event_descr tsc_event_table[] =
 {
-	__PMC_EV_TSC()
+	__PMC_EV_ALIAS_TSC()
 };
 
 #undef	PMC_CLASS_TABLE_DESC

lib/libpmc/libpmc_pmu_util.c

@@ -74,7 +74,6 @@ static struct pmu_alias pmu_intel_alias_table[] = {
 	{"BRANCH-INSTRUCTION-RETIRED", "BR_INST_RETIRED.ALL_BRANCHES"},
 	{"BRANCH_MISSES_RETIRED", "BR_MISP_RETIRED.ALL_BRANCHES"},
 	{"BRANCH-MISSES-RETIRED", "BR_MISP_RETIRED.ALL_BRANCHES"},
-	{"cycles", "tsc-tsc"},
 	{"unhalted-cycles", "CPU_CLK_UNHALTED.THREAD_P_ANY"},
 	{"instructions", "inst_retired.any_p"},
 	{"branch-mispredicts", "br_misp_retired.all_branches"},

sys/dev/hwpmc/pmc_events.h

@@ -54,6 +54,9 @@
 #define        PMC_EV_TSC_FIRST        PMC_EV_TSC_TSC
 #define        PMC_EV_TSC_LAST         PMC_EV_TSC_TSC
 
+#define	__PMC_EV_ALIAS_TSC()			\
+__PMC_EV_ALIAS("cycles",	TSC_TSC)
+
 /*
  * Software events are dynamically defined.
  */