[PATCH 13/16] aarch64: inline __libc_mtag_address_get_tag

[Szabolcs Nagy <szabolcs.nagy@arm.com>]

This is a common operation when heap tagging is enabled, so inline the
instruction instead of using an extern call.

The .inst directive is used instead of the name of the instruction (or
acle intrinsics) because malloc.c is not compiled for armv8.5-a+memtag
architecture, runtime cpu support detection is used.

Prototypes are removed from the comments as they were not always
correct.
---
 sysdeps/aarch64/Makefile                 |  3 +--
 sysdeps/aarch64/__mtag_address_get_tag.S | 32 ------------------------
 sysdeps/aarch64/libc-mtag.h              | 14 +++++++----
 3 files changed, 10 insertions(+), 39 deletions(-)
 delete mode 100644 sysdeps/aarch64/__mtag_address_get_tag.S

diff --git a/sysdeps/aarch64/Makefile b/sysdeps/aarch64/Makefile
index 259070cfad..5d594debea 100644
--- a/sysdeps/aarch64/Makefile
+++ b/sysdeps/aarch64/Makefile
@@ -40,8 +40,7 @@ endif
 
 ifeq ($(subdir),misc)
 sysdep_headers += sys/ifunc.h
-sysdep_routines += __mtag_address_get_tag \
-		   __mtag_tag_zero_region \
+sysdep_routines += __mtag_tag_zero_region \
 		   __mtag_new_tag \
 		   __mtag_tag_region
 
diff --git a/sysdeps/aarch64/__mtag_address_get_tag.S b/sysdeps/aarch64/__mtag_address_get_tag.S
deleted file mode 100644
index eab6c49285..0000000000
--- a/sysdeps/aarch64/__mtag_address_get_tag.S
+++ /dev/null
@@ -1,32 +0,0 @@
-/* Copyright (C) 2020-2021 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
-   <http://www.gnu.org/licenses/>.  */
-
-#include <sysdep.h>
-
-#ifdef USE_MTAG
-#define ptr x0
-
-	.arch armv8.5-a
-	.arch_extension memtag
-
-ENTRY (__libc_mtag_address_get_tag)
-
-	ldg	ptr, [ptr]
-	ret
-END (__libc_mtag_address_get_tag)
-#endif /* USE_MTAG */
diff --git a/sysdeps/aarch64/libc-mtag.h b/sysdeps/aarch64/libc-mtag.h
index f58402ccf9..da1b6be776 100644
--- a/sysdeps/aarch64/libc-mtag.h
+++ b/sysdeps/aarch64/libc-mtag.h
@@ -35,17 +35,21 @@
 #define __MTAG_MMAP_FLAGS PROT_MTE
 
 /* Set the tags for a region of memory, which must have size and alignment
-   that are multiples of __MTAG_GRANULE_SIZE.  Size cannot be zero.
-   void *__libc_mtag_tag_region (const void *, size_t)  */
+   that are multiples of __MTAG_GRANULE_SIZE.  Size cannot be zero.  */
 void *__libc_mtag_tag_region (void *, size_t);
 
 /* Optimized equivalent to __libc_mtag_tag_region followed by memset to 0.  */
 void *__libc_mtag_tag_zero_region (void *, size_t);
 
 /* Convert address P to a pointer that is tagged correctly for that
-   location.
-   void *__libc_mtag_address_get_tag (void*)  */
-void *__libc_mtag_address_get_tag (void *);
+   location.  */
+static __always_inline void *
+__libc_mtag_address_get_tag (void *p)
+{
+  register void *x0 asm ("x0") = p;
+  asm (".inst 0xd9600000 /* ldg x0, [x0] */" : "+r" (x0));
+  return x0;
+}
 
 /* Assign a new (random) tag to a pointer P (does not adjust the tag on
    the memory addressed).
-- 
2.17.1