perf tools: xtensa: add DWARF register names

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

tools/perf/arch/xtensa/Build

+libperf-y += util/

tools/perf/arch/xtensa/Makefile

+ifndef NO_DWARF
+PERF_HAVE_DWARF_REGS := 1
+endif

tools/perf/arch/xtensa/util/Build

+libperf-$(CONFIG_DWARF) += dwarf-regs.o

tools/perf/arch/xtensa/util/dwarf-regs.c

+/*
+ * Mapping of DWARF debug register numbers into register names.
+ *
+ * Copyright (c) 2015 Cadence Design Systems Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <stddef.h>
+#include <dwarf-regs.h>
+
+#define XTENSA_MAX_REGS 16
+
+const char *xtensa_regs_table[XTENSA_MAX_REGS] = {
+	"a0", "a1", "a2", "a3", "a4", "a5", "a6", "a7",
+	"a8", "a9", "a10", "a11", "a12", "a13", "a14", "a15",
+};
+
+const char *get_arch_regstr(unsigned int n)
+{
+	return n < XTENSA_MAX_REGS ? xtensa_regs_table[n] : NULL;
+}