perf tools: Fix build break on powerpc due to sample_reg_masks

The perf_regs.c file does not get built on Powerpc as CONFIG_PERF_REGS
is false.  So the weak definition for 'sample_regs_masks' doesn't get
picked up.

Adding perf_regs.o to util/Build unconditionally, exposes a redefinition
error for 'perf_reg_value()' function (due to the static inline version
in util/perf_regs.h). So use #ifdef HAVE_PERF_REGS_SUPPORT' around that
function.

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Dominik Dingel <dingel@linux.vnet.ibm.com>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: linuxppc-dev@ozlabs.org
Link: http://lkml.kernel.org/r/20150930182836.GA27858@us.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/Build

@@ -18,6 +18,7 @@ libperf-y += levenshtein.o
 libperf-y += llvm-utils.o
 libperf-y += parse-options.o
 libperf-y += parse-events.o
+libperf-y += perf_regs.o
 libperf-y += path.o
 libperf-y += rbtree.o
 libperf-y += bitmap.o
@@ -104,7 +105,6 @@ libperf-$(CONFIG_LIBBABELTRACE) += data-convert-bt.o
 
 libperf-y += scripting-engines/
 
-libperf-$(CONFIG_PERF_REGS) += perf_regs.o
 libperf-$(CONFIG_ZLIB) += zlib.o
 libperf-$(CONFIG_LZMA) += lzma.o
 

tools/perf/util/perf_regs.c

@@ -6,6 +6,7 @@ const struct sample_reg __weak sample_reg_masks[] = {
 	SMPL_REG_END
 };
 
+#ifdef HAVE_PERF_REGS_SUPPORT
 int perf_reg_value(u64 *valp, struct regs_dump *regs, int id)
 {
 	int i, idx = 0;
@@ -29,3 +30,4 @@ out:
 	*valp = regs->cache_regs[id];
 	return 0;
 }
+#endif

tools/perf/util/perf_regs.h

@@ -2,6 +2,7 @@
 #define __PERF_REGS_H
 
 #include <linux/types.h>
+#include <linux/compiler.h>
 
 struct regs_dump;