x86: Import the glibc memset implementation

The new implementation is about twice as fast as the old. This is from
glibc-2.14, sysdeps/i386/memset.c.

Signed-off-by: Gabe Black <gabeblack@chromium.org>

diff --git a/arch/x86/include/asm/string.h b/arch/x86/include/asm/string.h
index 3643a79fdfc1c014d25d3aade1c8f3a13164c411..3aa6c1131b21cd3d192a454414c8c9ccb61dd75f 100644 (file)
--- a/arch/x86/include/asm/string.h
+++ b/arch/x86/include/asm/string.h
@@ -23,7 +23,7 @@ extern void * memmove(void *, const void *, __kernel_size_t);
 #undef __HAVE_ARCH_MEMCHR
 extern void * memchr(const void *, int, __kernel_size_t);
 
-#undef __HAVE_ARCH_MEMSET
+#define __HAVE_ARCH_MEMSET
 extern void * memset(void *, int, __kernel_size_t);
 
 #undef __HAVE_ARCH_MEMZERO

diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index eb5fa10398e9da81a65b3b752e6a313df485ff92..90f328333ccdc0c1106f7cdb92e402bf321ddf1d 100644 (file)
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -38,6 +38,7 @@ COBJS-$(CONFIG_SYS_GENERIC_TIMER) += pcat_timer.o
 COBJS-$(CONFIG_PCI) += pci.o
 COBJS-$(CONFIG_PCI) += pci_type1.o
 COBJS-$(CONFIG_SYS_X86_REALMODE)       += realmode.o
+COBJS-y        += string.o
 COBJS-$(CONFIG_SYS_X86_ISR_TIMER)      += timer.o
 COBJS-$(CONFIG_VIDEO)  += video_bios.o
 COBJS-$(CONFIG_VIDEO)  += video.o

diff --git a/arch/x86/lib/string.c b/arch/x86/lib/string.c
new file mode 100644 (file)
index 0000000..f2ea7e4
--- /dev/null
+++ b/arch/x86/lib/string.c
@@ -0,0 +1,87 @@
+/*
+ * Copyright (C) 1991,1992,1993,1997,1998,2003, 2005 Free Software Foundation, Inc.
+ * This file is part of the GNU C Library.
+ * Copyright (c) 2011 The Chromium OS Authors.
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+/* From glibc-2.14, sysdeps/i386/memset.c */
+
+#include <compiler.h>
+#include <asm/string.h>
+#include <linux/types.h>
+
+typedef uint32_t op_t;
+
+void *memset(void *dstpp, int c, size_t len)
+{
+       int d0;
+       unsigned long int dstp = (unsigned long int) dstpp;
+
+       /* This explicit register allocation improves code very much indeed. */
+       register op_t x asm("ax");
+
+       x = (unsigned char) c;
+
+       /* Clear the direction flag, so filling will move forward.  */
+       asm volatile("cld");
+
+       /* This threshold value is optimal.  */
+       if (len >= 12) {
+               /* Fill X with four copies of the char we want to fill with. */
+               x |= (x << 8);
+               x |= (x << 16);
+
+               /* Adjust LEN for the bytes handled in the first loop.  */
+               len -= (-dstp) % sizeof(op_t);
+
+               /*
+                * There are at least some bytes to set. No need to test for
+                * LEN == 0 in this alignment loop.
+                */
+
+               /* Fill bytes until DSTP is aligned on a longword boundary. */
+               asm volatile(
+                       "rep\n"
+                       "stosb" /* %0, %2, %3 */ :
+                       "=D" (dstp), "=c" (d0) :
+                       "0" (dstp), "1" ((-dstp) % sizeof(op_t)), "a" (x) :
+                       "memory");
+
+               /* Fill longwords.  */
+               asm volatile(
+                       "rep\n"
+                       "stosl" /* %0, %2, %3 */ :
+                       "=D" (dstp), "=c" (d0) :
+                       "0" (dstp), "1" (len / sizeof(op_t)), "a" (x) :
+                       "memory");
+               len %= sizeof(op_t);
+       }
+
+       /* Write the last few bytes. */
+       asm volatile(
+               "rep\n"
+               "stosb" /* %0, %2, %3 */ :
+               "=D" (dstp), "=c" (d0) :
+               "0" (dstp), "1" (len), "a" (x) :
+               "memory");
+
+       return dstpp;
+}