[v2,3/5] LoongArch: Define __ASSUME_SYSCALL_NAMED_WORKS for Linux
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Commit Message
LoongArch calling convention treats the non-floating-point variable
arguments same as named ones, and when each argument is an integer
not wider than long or a pointer, the ith argument is in register $ai
(0 <= i < 8) or the stack slot at ($sp + sizeof(long) * (i - 8))
(i >= 8) no matter how many arguments are passed. So we can define
__ASSUME_SYSCALL_NAMED_WORKS to avoid unnecessary stack stores in the
syscall wrappers caused by va_start.
---
.../sysv/linux/loongarch/kernel-features.h | 29 +++++++++++++++++++
1 file changed, 29 insertions(+)
create mode 100644 sysdeps/unix/sysv/linux/loongarch/kernel-features.h
new file mode 100644
@@ -0,0 +1,29 @@
+/* Set flags signalling availability of kernel features based on given
+ kernel version number.
+ Copyright (C) 2023 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/>. */
+
+#include_next <kernel-features.h>
+
+/* Define this if the calling convention for passing x named arguments and y
+ variable arguments is same as passing (x + y) named arguments, while each
+ argument is either an integer of which the width is less than or equal to
+ "long", or a pointer; and an argument can be fetched from the same register
+ or the same offset from the stack pointer no matter how many (maybe zero)
+ arguments are passed after it. It avoids useless stack stores caused by
+ usage of va_start. */
+#define __ASSUME_SYSCALL_NAMED_WORKS 1