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Re: [PATCH 5/6] Optimize i386 syscall inlining
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Roland McGrath <roland at hack dot frob dot com>
- Cc: GNU C Library <libc-alpha at sourceware dot org>
- Date: Thu, 15 Oct 2015 13:13:39 -0700
- Subject: Re: [PATCH 5/6] Optimize i386 syscall inlining
- Authentication-results: sourceware.org; auth=none
- References: <20151012232028 dot GC8797 at intel dot com> <20151015195427 dot 98E272C3C0E at topped-with-meat dot com>
On Thu, Oct 15, 2015 at 12:54 PM, Roland McGrath <roland@hack.frob.com> wrote:
> This needs comments explaining why the compiler version conditional
> makes sense.
How about this?
--
H.J.
----
diff --git a/sysdeps/unix/sysv/linux/i386/sysdep.h
b/sysdeps/unix/sysv/linux/i386/sysdep.h
index 5324da6..76db7b8 100644
--- a/sysdeps/unix/sysv/linux/i386/sysdep.h
+++ b/sysdeps/unix/sysv/linux/i386/sysdep.h
@@ -227,6 +227,10 @@
extern int __syscall_error (int)
attribute_hidden __attribute__ ((__regparm__ (1)));
+/* Since GCC 5 and above can properly spill %ebx with PIC when needed,
+ we can inline syscalls with 6 arguments if GCC 5 or above is used
+ to compile glibc. */
+
#if !__GNUC_PREREQ (5,0)
/* We need some help from the assembler to generate optimal code. We
define some macros here which later will be used. */