add file

git-svn-id: svn+ssh://jackaudio.org/trunk/jack@176 0c269be4-1314-0410-8aa9-9f06e86f4224

jack/cycles.h

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+/*
+    Copyright (C) 2001 Paul Davis
+    Code derived from various headers from the Linux kernel
+    
+    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.
+
+    This program 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.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+    $Id$
+*/
+
+#ifndef __jack_cycles_h__
+#define __jack_cycles_h__
+
+#ifdef __i386__
+
+/*
+ * Standard way to access the cycle counter on i586+ CPUs.
+ * Currently only used on SMP.
+ *
+ * If you really have a SMP machine with i486 chips or older,
+ * compile for that, and this will just always return zero.
+ * That's ok, it just means that the nicer scheduling heuristics
+ * won't work for you.
+ *
+ * We only use the low 32 bits, and we'd simply better make sure
+ * that we reschedule before that wraps. Scheduling at least every
+ * four billion cycles just basically sounds like a good idea,
+ * regardless of how fast the machine is. 
+ */
+typedef unsigned long long cycles_t;
+
+extern cycles_t cacheflush_time;
+
+#define rdtscll(val) \
+     __asm__ __volatile__("rdtsc" : "=A" (val))
+
+static inline cycles_t get_cycles (void)
+{
+	unsigned long long ret;
+
+	rdtscll(ret);
+	return ret;
+}
+
+#else  /* !i386 */
+
+#ifdef __ppc__
+
+typedef unsigned long cycles_t;
+
+/*
+ * For the "cycle" counter we use the timebase lower half.
+ * Currently only used on SMP.
+ */
+
+extern cycles_t cacheflush_time;
+
+static inline cycles_t get_cycles(void)
+{
+	cycles_t ret = 0;
+
+	__asm__ __volatile__(
+		"98:	mftb %0\n"
+		"99:\n"
+		".section __ftr_fixup,\"a\"\n"
+		"	.long %1\n"
+		"	.long 0\n"
+		"	.long 98b\n"
+		"	.long 99b\n"
+		".previous"
+		: "=r" (ret) : "i" (CPU_FTR_601));
+	return ret;
+}
+#else /* PPC */
+#error You are compiling JACK on a platform for which jack/cycles.h needs work
+#endif /* PPC */
+#endif /* i386 */
+
+#endif /* __jack_cycles_h__ */