add support of omp_get_wtime

hermit/usr/libgomp/time.c

@@ -0,0 +1,64 @@
+/* Copyright (C) 2015 RWTH Aachen University, Germany.
+   Contributed by Stefan Lankes <slankes@eonerc.rwth-aachen.de>.
+
+   Libgomp 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 3, or (at your option)
+   any later version.
+
+   Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+   FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+   more details.
+
+   Under Section 7 of GPL version 3, you are granted additional
+   permissions described in the GCC Runtime Library Exception, version
+   3.1, as published by the Free Software Foundation.
+
+   You should have received a copy of the GNU General Public License and
+   a copy of the GCC Runtime Library Exception along with this program;
+   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/*
+ * This file contains system specific timer routines.  It is expected that
+ * a system may well want to write special versions of each of these.
+ */
+
+#include "libgomp.h"
+#include <unistd.h>
+
+extern unsigned int get_cpufreq(void);
+static unsigned long long start_tsc;
+
+inline static unsigned long long rdtsc(void)
+{
+	unsigned long lo, hi;
+	asm volatile ("rdtsc" : "=a"(lo), "=d"(hi) :: "memory");
+	return ((unsigned long long) hi << 32ULL | (unsigned long long) lo);
+}
+
+__attribute__((constructor)) static void timer_init()
+{
+	start_tsc = rdtsc();
+}
+
+double
+omp_get_wtime (void)
+{
+	double ret;
+
+	ret = (double) (rdtsc() - start_tsc) / ((double) get_cpufreq() * 1000000.0);
+	//printf("CPU frequency: %d MHz\n", get_cpufreq());
+
+	return ret;
+}
+
+double
+omp_get_wtick (void)
+{
+	return 1.0 / ((double) get_cpufreq() * 1000000.0);
+}
+
+ialias (omp_get_wtime)
+ialias (omp_get_wtick)