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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/memcpy.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/memcpy.S')
-rw-r--r--libc/string/xtensa/memcpy.S297
1 files changed, 297 insertions, 0 deletions
diff --git a/libc/string/xtensa/memcpy.S b/libc/string/xtensa/memcpy.S
new file mode 100644
index 000000000..19f3a6818
--- /dev/null
+++ b/libc/string/xtensa/memcpy.S
@@ -0,0 +1,297 @@
+/* Optimized memcpy 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>
+
+ .macro src_b r, w0, w1
+#ifdef __XTENSA_EB__
+ src \r, \w0, \w1
+#else
+ src \r, \w1, \w0
+#endif
+ .endm
+
+ .macro ssa8 r
+#ifdef __XTENSA_EB__
+ ssa8b \r
+#else
+ ssa8l \r
+#endif
+ .endm
+
+/* If the Xtensa Unaligned Load Exception option is not used, this
+ code can run a few cycles faster by relying on the low address bits
+ being ignored. However, if the code is then run with an Xtensa ISS
+ client that checks for unaligned accesses, it will produce a lot of
+ warning messages. Set this flag to disable the use of unaligned
+ accesses and keep the ISS happy. */
+
+#define UNALIGNED_ADDRESSES_CHECKED 1
+
+/* Do not use .literal_position in the ENTRY macro. */
+#undef LITERAL_POSITION
+#define LITERAL_POSITION
+
+
+/* void *memcpy (void *dst, const void *src, size_t len)
+
+ The algorithm is as follows:
+
+ If the destination is unaligned, align it by conditionally
+ copying 1- and/or 2-byte pieces.
+
+ If the source is aligned, copy 16 bytes with a loop, and then finish up
+ with 8, 4, 2, and 1-byte copies conditional on the length.
+
+ Else (if source is unaligned), do the same, but use SRC to align the
+ source data.
+
+ This code tries to use fall-through branches for the common
+ case of aligned source and destination and multiple of 4 (or 8) length. */
+
+
+/* Byte by byte copy. */
+
+ .text
+ .align 4
+ .literal_position
+__memcpy_aux:
+
+ /* Skip a byte to get 1 mod 4 alignment for LOOPNEZ
+ (0 mod 4 alignment for LBEG). */
+ .byte 0
+
+.Lbytecopy:
+#if XCHAL_HAVE_LOOPS
+ loopnez a4, 2f
+#else
+ beqz a4, 2f
+ add a7, a3, a4 // a7 = end address for source
+#endif
+1: l8ui a6, a3, 0
+ addi a3, a3, 1
+ s8i a6, a5, 0
+ addi a5, a5, 1
+#if !XCHAL_HAVE_LOOPS
+ blt a3, a7, 1b
+#endif
+2: retw
+
+
+/* Destination is unaligned. */
+
+ .align 4
+.Ldst1mod2: // dst is only byte aligned
+
+ /* Do short copies byte-by-byte. */
+ _bltui a4, 7, .Lbytecopy
+
+ /* Copy 1 byte. */
+ l8ui a6, a3, 0
+ addi a3, a3, 1
+ addi a4, a4, -1
+ s8i a6, a5, 0
+ addi a5, a5, 1
+
+ /* Return to main algorithm if dst is now aligned. */
+ _bbci.l a5, 1, .Ldstaligned
+
+.Ldst2mod4: // dst has 16-bit alignment
+
+ /* Do short copies byte-by-byte. */
+ _bltui a4, 6, .Lbytecopy
+
+ /* Copy 2 bytes. */
+ l8ui a6, a3, 0
+ l8ui a7, a3, 1
+ addi a3, a3, 2
+ addi a4, a4, -2
+ s8i a6, a5, 0
+ s8i a7, a5, 1
+ addi a5, a5, 2
+
+ /* dst is now aligned; return to main algorithm. */
+ j .Ldstaligned
+
+
+ENTRY (memcpy)
+ /* a2 = dst, a3 = src, a4 = len */
+
+ mov a5, a2 // copy dst so that a2 is return value
+ _bbsi.l a2, 0, .Ldst1mod2
+ _bbsi.l a2, 1, .Ldst2mod4
+.Ldstaligned:
+
+ /* Get number of loop iterations with 16B per iteration. */
+ srli a7, a4, 4
+
+ /* Check if source is aligned. */
+ movi a8, 3
+ _bany a3, a8, .Lsrcunaligned
+
+ /* Destination and source are word-aligned, use word copy. */
+#if XCHAL_HAVE_LOOPS
+ loopnez a7, 2f
+#else
+ beqz a7, 2f
+ slli a8, a7, 4
+ add a8, a8, a3 // a8 = end of last 16B source chunk
+#endif
+1: l32i a6, a3, 0
+ l32i a7, a3, 4
+ s32i a6, a5, 0
+ l32i a6, a3, 8
+ s32i a7, a5, 4
+ l32i a7, a3, 12
+ s32i a6, a5, 8
+ addi a3, a3, 16
+ s32i a7, a5, 12
+ addi a5, a5, 16
+#if !XCHAL_HAVE_LOOPS
+ blt a3, a8, 1b
+#endif
+
+ /* Copy any leftover pieces smaller than 16B. */
+2: bbci.l a4, 3, 3f
+
+ /* Copy 8 bytes. */
+ l32i a6, a3, 0
+ l32i a7, a3, 4
+ addi a3, a3, 8
+ s32i a6, a5, 0
+ s32i a7, a5, 4
+ addi a5, a5, 8
+
+3: bbsi.l a4, 2, 4f
+ bbsi.l a4, 1, 5f
+ bbsi.l a4, 0, 6f
+ retw
+
+ /* Copy 4 bytes. */
+4: l32i a6, a3, 0
+ addi a3, a3, 4
+ s32i a6, a5, 0
+ addi a5, a5, 4
+ bbsi.l a4, 1, 5f
+ bbsi.l a4, 0, 6f
+ retw
+
+ /* Copy 2 bytes. */
+5: l16ui a6, a3, 0
+ addi a3, a3, 2
+ s16i a6, a5, 0
+ addi a5, a5, 2
+ bbsi.l a4, 0, 6f
+ retw
+
+ /* Copy 1 byte. */
+6: l8ui a6, a3, 0
+ s8i a6, a5, 0
+
+.Ldone:
+ retw
+
+
+/* Destination is aligned; source is unaligned. */
+
+ .align 4
+.Lsrcunaligned:
+ /* Avoid loading anything for zero-length copies. */
+ _beqz a4, .Ldone
+
+ /* Copy 16 bytes per iteration for word-aligned dst and
+ unaligned src. */
+ ssa8 a3 // set shift amount from byte offset
+#if UNALIGNED_ADDRESSES_CHECKED
+ and a11, a3, a8 // save unalignment offset for below
+ sub a3, a3, a11 // align a3
+#endif
+ l32i a6, a3, 0 // load first word
+#if XCHAL_HAVE_LOOPS
+ loopnez a7, 2f
+#else
+ beqz a7, 2f
+ slli a10, a7, 4
+ add a10, a10, a3 // a10 = end of last 16B source chunk
+#endif
+1: l32i a7, a3, 4
+ l32i a8, a3, 8
+ src_b a6, a6, a7
+ s32i a6, a5, 0
+ l32i a9, a3, 12
+ src_b a7, a7, a8
+ s32i a7, a5, 4
+ l32i a6, a3, 16
+ src_b a8, a8, a9
+ s32i a8, a5, 8
+ addi a3, a3, 16
+ src_b a9, a9, a6
+ s32i a9, a5, 12
+ addi a5, a5, 16
+#if !XCHAL_HAVE_LOOPS
+ blt a3, a10, 1b
+#endif
+
+2: bbci.l a4, 3, 3f
+
+ /* Copy 8 bytes. */
+ l32i a7, a3, 4
+ l32i a8, a3, 8
+ src_b a6, a6, a7
+ s32i a6, a5, 0
+ addi a3, a3, 8
+ src_b a7, a7, a8
+ s32i a7, a5, 4
+ addi a5, a5, 8
+ mov a6, a8
+
+3: bbci.l a4, 2, 4f
+
+ /* Copy 4 bytes. */
+ l32i a7, a3, 4
+ addi a3, a3, 4
+ src_b a6, a6, a7
+ s32i a6, a5, 0
+ addi a5, a5, 4
+ mov a6, a7
+4:
+#if UNALIGNED_ADDRESSES_CHECKED
+ add a3, a3, a11 // readjust a3 with correct misalignment
+#endif
+ bbsi.l a4, 1, 5f
+ bbsi.l a4, 0, 6f
+ retw
+
+ /* Copy 2 bytes. */
+5: l8ui a6, a3, 0
+ l8ui a7, a3, 1
+ addi a3, a3, 2
+ s8i a6, a5, 0
+ s8i a7, a5, 1
+ addi a5, a5, 2
+ bbsi.l a4, 0, 6f
+ retw
+
+ /* Copy 1 byte. */
+6: l8ui a6, a3, 0
+ s8i a6, a5, 0
+ retw
+
+libc_hidden_def (memcpy)