[glibc] AArch64: Add hp-timing.h

[glibc] AArch64: Add hp-timing.h

[Wilco Dijkstra]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=6a34c928c2ac9fce926b1348d61dae34262e3f77

commit 6a34c928c2ac9fce926b1348d61dae34262e3f77
Author: Wilco Dijkstra <wilco.dijkstra@arm.com>
Date:   Thu Jul 1 15:42:05 2021 +0100

    AArch64: Add hp-timing.h
    
    Add hp-timing.h using the cntvct_el0 counter. Return timing in nanoseconds
    so it is fully compatible with generic hp-timing. Don't set HP_TIMING_INLINE
    in the dynamic linker since it adds unnecessary overheads and some ancient
    kernels may not handle emulating cntcvt correctly. Currently cntvct_el0 is
    only used for timing in the benchtests.
    
    Reviewed-by: Szabolcs Nagy  <szabolcs.nagy@arm.com>

Diff:
---
 sysdeps/aarch64/hp-timing.h | 47 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/sysdeps/aarch64/hp-timing.h b/sysdeps/aarch64/hp-timing.h
new file mode 100644
index 0000000000..f9822e725c
--- /dev/null
+++ b/sysdeps/aarch64/hp-timing.h
@@ -0,0 +1,47 @@
+/* High precision, low overhead timing functions.  AArch64 version.
+   Copyright (C) 2021 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
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _HP_TIMING_H
+#define _HP_TIMING_H	1
+
+#include <time.h>
+#include <stdint.h>
+#include <hp-timing-common.h>
+#include <libc-symbols.h>
+
+/* Don't use inline timer in ld.so.  */
+#if IS_IN(rtld)
+# define HP_TIMING_INLINE	(0)
+#else
+# define HP_TIMING_INLINE	(1)
+#endif
+
+typedef uint64_t hp_timing_t;
+
+#define HP_TIMING_NOW(var) \
+  __asm__ __volatile__ ("isb; mrs %0, cntvct_el0" : "=r" (var))
+
+/* Compute elapsed time in nanoseconds.  */
+#undef HP_TIMING_DIFF
+#define HP_TIMING_DIFF(Diff, Start, End)			\
+({  hp_timing_t freq;						\
+    __asm__ __volatile__ ("mrs %0, cntfrq_el0" : "=r" (freq));	\
+   (Diff) = ((End) - (Start)) * (UINT64_C(1000000000) / freq);	\
+})
+
+#endif	/* hp-timing.h */