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authorTulio Magno Quites Machado Filho <tuliom@linux.vnet.ibm.com>2012-06-04 13:46:37 -0500
committerRyan S. Arnold <rsa@linux.vnet.ibm.com>2012-06-04 13:46:37 -0500
commitd9dc34cd569bcfe714fe8c708e58c028106e8b2e (patch)
tree82c7c02aab8419ffd869c72b1b5644b1dae6eb38 /sysdeps
parent06775cb82b8c8381ea0cc636a70ed9e7ca81b548 (diff)
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Manual for platform-specific features and new __ppc_get_timebase inline.
[BZ #13743] A new class of installed headers has been documented for low-level platform-specific functionality. PowerPC added the first instance with a function to provide time base register access (__ppc_get_timebase). This is required for applications that measure time at high frequencies with high precision that can't afford a syscall.
Diffstat (limited to 'sysdeps')
-rw-r--r--sysdeps/powerpc/Makefile5
-rw-r--r--sysdeps/powerpc/sys/platform/ppc.h47
-rw-r--r--sysdeps/powerpc/test-gettimebase.c46
3 files changed, 98 insertions, 0 deletions
diff --git a/sysdeps/powerpc/Makefile b/sysdeps/powerpc/Makefile
index 23a9a16730..79dd6fa976 100644
--- a/sysdeps/powerpc/Makefile
+++ b/sysdeps/powerpc/Makefile
@@ -26,3 +26,8 @@ gen-as-const-headers += rtld-global-offsets.sym
# get offset to __locale_struct.__ctype_tolower
gen-as-const-headers += locale-defines.sym
endif
+
+ifeq ($(subdir),misc)
+sysdep_headers += sys/platform/ppc.h
+tests += test-gettimebase
+endif
diff --git a/sysdeps/powerpc/sys/platform/ppc.h b/sysdeps/powerpc/sys/platform/ppc.h
new file mode 100644
index 0000000000..165652c7cc
--- /dev/null
+++ b/sysdeps/powerpc/sys/platform/ppc.h
@@ -0,0 +1,47 @@
+/* Facilities specific to the PowerPC architecture
+ Copyright (C) 2012 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _SYS_PLATFORM_PPC_H
+#define _SYS_PLATFORM_PPC_H 1
+
+#include <stdint.h>
+
+/* Read the Time Base Register. */
+static inline uint64_t
+__ppc_get_timebase (void)
+{
+#ifdef __powerpc64__
+ uint64_t __tb;
+ /* "volatile" is necessary here, because the user expects this assembly
+ isn't moved after an optimization. */
+ __asm__ volatile ("mfspr %0, 268" : "=r" (__tb));
+ return __tb;
+#else /* not __powerpc64__ */
+ uint32_t __tbu, __tbl, __tmp; \
+ __asm__ volatile ("0:\n\t"
+ "mftbu %0\n\t"
+ "mftbl %1\n\t"
+ "mftbu %2\n\t"
+ "cmpw %0, %2\n\t"
+ "bne- 0b"
+ : "=r" (__tbu), "=r" (__tbl), "=r" (__tmp));
+ return (((uint64_t) __tbu << 32) | __tbl);
+#endif /* not __powerpc64__ */
+}
+
+#endif /* sys/platform/ppc.h */
diff --git a/sysdeps/powerpc/test-gettimebase.c b/sysdeps/powerpc/test-gettimebase.c
new file mode 100644
index 0000000000..0e828ff868
--- /dev/null
+++ b/sysdeps/powerpc/test-gettimebase.c
@@ -0,0 +1,46 @@
+/* Check __ppc_get_timebase() for architecture changes
+ Copyright (C) 2012 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+/* Test if __ppc_get_timebase() is compatible with the current processor and if
+ it's changing between reads. A read failure might indicate a Power ISA or
+ binutils change. */
+
+#include <inttypes.h>
+#include <stdio.h>
+
+#include <sys/platform/ppc.h>
+
+static int
+do_test (void)
+{
+ uint64_t t1, t2, t3;
+ t1 = __ppc_get_timebase ();
+ printf ("Time Base = %"PRIu64"\n", t1);
+ t2 = __ppc_get_timebase ();
+ printf ("Time Base = %"PRIu64"\n", t2);
+ t3 = __ppc_get_timebase ();
+ printf ("Time Base = %"PRIu64"\n", t3);
+ if (t1 != t2 && t1 != t3 && t2 != t3)
+ return 0;
+
+ printf ("Fail: timebase reads should always be different.");
+ return 1;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"