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authorMike Frysinger <vapier@gentoo.org>2008-01-05 10:05:27 +0000
committerMike Frysinger <vapier@gentoo.org>2008-01-05 10:05:27 +0000
commit124ec188720b6bdea85ade49e7ea195161b12fce (patch)
tree2bce39bc1e51bd587e010a61419b47d122be3165 /libc/string/xtensa/memset.S
parent9c95d5d28d8d40f7b826c9399f5ce781bbc61567 (diff)
Chris Zankel writes:
The following patches add support for the Xtensa processor architecture to uClibc. They are based on a recent SVN checkout (12/05/2007). The first patch (attached to this post) adds Xtensa support to various shared configuration and make files. The following patches then include the Xtensa specific files and directories. I welcome any feedback and would appreciate it if you could include the patches into the mainline tree. I am certainly committed to maintain the port. Bob Wilson was kind enough to review the patches. Some notes about the architecture: Xtensa is a configurable and extensible processor architecture developed by Tensilica. For more information, please visit: www.linux-xtensa.org.
Diffstat (limited to 'libc/string/xtensa/memset.S')
-rw-r--r--libc/string/xtensa/memset.S165
1 files changed, 165 insertions, 0 deletions
diff --git a/libc/string/xtensa/memset.S b/libc/string/xtensa/memset.S
new file mode 100644
index 000000000..c0928825d
--- /dev/null
+++ b/libc/string/xtensa/memset.S
@@ -0,0 +1,165 @@
+/* Optimized memset for Xtensa.
+ Copyright (C) 2001, 2007 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, write to the Free
+ Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
+ Boston, MA 02110-1301, USA. */
+
+#include "../../sysdeps/linux/xtensa/sysdep.h"
+#include <bits/xtensa-config.h>
+
+/* Do not use .literal_position in the ENTRY macro. */
+#undef LITERAL_POSITION
+#define LITERAL_POSITION
+
+/* void *memset (void *dst, int c, size_t length)
+
+ The algorithm is as follows:
+
+ Create a word with c in all byte positions.
+
+ If the destination is aligned, set 16B chunks with a loop, and then
+ finish up with 8B, 4B, 2B, and 1B stores conditional on the length.
+
+ If the destination is unaligned, align it by conditionally
+ setting 1B and/or 2B and then go to aligned case.
+
+ This code tries to use fall-through branches for the common
+ case of an aligned destination (except for the branches to
+ the alignment labels). */
+
+
+/* Byte-by-byte set. */
+
+ .text
+ .align 4
+ .literal_position
+__memset_aux:
+
+ /* Skip a byte to get 1 mod 4 alignment for LOOPNEZ
+ (0 mod 4 alignment for LBEG). */
+ .byte 0
+
+.Lbyteset:
+#if XCHAL_HAVE_LOOPS
+ loopnez a4, 2f
+#else
+ beqz a4, 2f
+ add a6, a5, a4 // a6 = ending address
+#endif
+1: s8i a3, a5, 0
+ addi a5, a5, 1
+#if !XCHAL_HAVE_LOOPS
+ blt a5, a6, 1b
+#endif
+2: retw
+
+
+/* Destination is unaligned. */
+
+ .align 4
+
+.Ldst1mod2: // dst is only byte aligned
+
+ /* Do short sizes byte-by-byte. */
+ bltui a4, 8, .Lbyteset
+
+ /* Set 1 byte. */
+ s8i a3, a5, 0
+ addi a5, a5, 1
+ addi a4, a4, -1
+
+ /* Now retest if dst is aligned. */
+ _bbci.l a5, 1, .Ldstaligned
+
+.Ldst2mod4: // dst has 16-bit alignment
+
+ /* Do short sizes byte-by-byte. */
+ bltui a4, 8, .Lbyteset
+
+ /* Set 2 bytes. */
+ s16i a3, a5, 0
+ addi a5, a5, 2
+ addi a4, a4, -2
+
+ /* dst is now aligned; return to main algorithm */
+ j .Ldstaligned
+
+
+ENTRY (memset)
+ /* a2 = dst, a3 = c, a4 = length */
+
+ /* Duplicate character into all bytes of word. */
+ extui a3, a3, 0, 8
+ slli a7, a3, 8
+ or a3, a3, a7
+ slli a7, a3, 16
+ or a3, a3, a7
+
+ mov a5, a2 // copy dst so that a2 is return value
+
+ /* Check if dst is unaligned. */
+ _bbsi.l a2, 0, .Ldst1mod2
+ _bbsi.l a2, 1, .Ldst2mod4
+.Ldstaligned:
+
+ /* Get number of loop iterations with 16B per iteration. */
+ srli a7, a4, 4
+
+ /* Destination is word-aligned. */
+#if XCHAL_HAVE_LOOPS
+ loopnez a7, 2f
+#else
+ beqz a7, 2f
+ slli a6, a7, 4
+ add a6, a6, a5 // a6 = end of last 16B chunk
+#endif
+ /* Set 16 bytes per iteration. */
+1: s32i a3, a5, 0
+ s32i a3, a5, 4
+ s32i a3, a5, 8
+ s32i a3, a5, 12
+ addi a5, a5, 16
+#if !XCHAL_HAVE_LOOPS
+ blt a5, a6, 1b
+#endif
+
+ /* Set any leftover pieces smaller than 16B. */
+2: bbci.l a4, 3, 3f
+
+ /* Set 8 bytes. */
+ s32i a3, a5, 0
+ s32i a3, a5, 4
+ addi a5, a5, 8
+
+3: bbci.l a4, 2, 4f
+
+ /* Set 4 bytes. */
+ s32i a3, a5, 0
+ addi a5, a5, 4
+
+4: bbci.l a4, 1, 5f
+
+ /* Set 2 bytes. */
+ s16i a3, a5, 0
+ addi a5, a5, 2
+
+5: bbci.l a4, 0, 6f
+
+ /* Set 1 byte. */
+ s8i a3, a5, 0
+6: retw
+
+libc_hidden_def (memset)