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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/strcmp.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/strcmp.S')
-rw-r--r--libc/string/xtensa/strcmp.S313
1 files changed, 313 insertions, 0 deletions
diff --git a/libc/string/xtensa/strcmp.S b/libc/string/xtensa/strcmp.S
new file mode 100644
index 000000000..90c418d12
--- /dev/null
+++ b/libc/string/xtensa/strcmp.S
@@ -0,0 +1,313 @@
+/* Optimized strcmp 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>
+
+#ifdef __XTENSA_EB__
+#define MASK0 0xff000000
+#define MASK1 0x00ff0000
+#define MASK2 0x0000ff00
+#define MASK3 0x000000ff
+#else
+#define MASK0 0x000000ff
+#define MASK1 0x0000ff00
+#define MASK2 0x00ff0000
+#define MASK3 0xff000000
+#endif
+
+#define MASK4 0x40404040
+
+ .literal .Lmask0, MASK0
+ .literal .Lmask1, MASK1
+ .literal .Lmask2, MASK2
+ .literal .Lmask3, MASK3
+ .literal .Lmask4, MASK4
+
+ .text
+ENTRY (strcmp)
+ /* a2 = s1, a3 = s2 */
+
+ l8ui a8, a2, 0 // byte 0 from s1
+ l8ui a9, a3, 0 // byte 0 from s2
+ movi a10, 3 // mask
+ bne a8, a9, .Lretdiff
+
+ or a11, a2, a3
+ bnone a11, a10, .Laligned
+
+ xor a11, a2, a3 // compare low two bits of s1 and s2
+ bany a11, a10, .Lunaligned // if they have different alignment
+
+ /* s1/s2 are not word-aligned. */
+ addi a2, a2, 1 // advance s1
+ beqz a8, .Leq // bytes equal, if zero, strings are equal
+ addi a3, a3, 1 // advance s2
+ bnone a2, a10, .Laligned // if s1/s2 now aligned
+ l8ui a8, a2, 0 // byte 1 from s1
+ l8ui a9, a3, 0 // byte 1 from s2
+ addi a2, a2, 1 // advance s1
+ bne a8, a9, .Lretdiff // if different, return difference
+ beqz a8, .Leq // bytes equal, if zero, strings are equal
+ addi a3, a3, 1 // advance s2
+ bnone a2, a10, .Laligned // if s1/s2 now aligned
+ l8ui a8, a2, 0 // byte 2 from s1
+ l8ui a9, a3, 0 // byte 2 from s2
+ addi a2, a2, 1 // advance s1
+ bne a8, a9, .Lretdiff // if different, return difference
+ beqz a8, .Leq // bytes equal, if zero, strings are equal
+ addi a3, a3, 1 // advance s2
+ j .Laligned
+
+/* s1 and s2 have different alignment.
+
+ If the zero-overhead loop option is available, use an (almost)
+ infinite zero-overhead loop with conditional exits so we only pay
+ for taken branches when exiting the loop.
+
+ Note: It is important for this unaligned case to come before the
+ code for aligned strings, because otherwise some of the branches
+ above cannot reach and have to be transformed to branches around
+ jumps. The unaligned code is smaller and the branches can reach
+ over it. */
+
+ .align 4
+ /* (2 mod 4) alignment for loop instruction */
+.Lunaligned:
+#if XCHAL_HAVE_LOOPS
+ _movi.n a8, 0 // set up for the maximum loop count
+ loop a8, .Lretdiff // loop forever (almost anyway)
+#endif
+.Lnextbyte:
+ l8ui a8, a2, 0
+ l8ui a9, a3, 0
+ addi a2, a2, 1
+ bne a8, a9, .Lretdiff
+ addi a3, a3, 1
+#if XCHAL_HAVE_LOOPS
+ beqz a8, .Lretdiff
+#else
+ bnez a8, .Lnextbyte
+#endif
+.Lretdiff:
+ sub a2, a8, a9
+ retw
+
+/* s1 is word-aligned; s2 is word-aligned.
+
+ If the zero-overhead loop option is available, use an (almost)
+ infinite zero-overhead loop with conditional exits so we only pay
+ for taken branches when exiting the loop. */
+
+/* New algorithm, relying on the fact that all normal ASCII is between
+ 32 and 127.
+
+ Rather than check all bytes for zero:
+ Take one word (4 bytes). Call it w1.
+ Shift w1 left by one into w1'.
+ Or w1 and w1'. For all normal ASCII bit 6 will be 1; for zero it won't.
+ Check that all 4 bit 6's (one for each byte) are one:
+ If they are, we are definitely not done.
+ If they are not, we are probably done, but need to check for zero. */
+
+ .align 4
+#if XCHAL_HAVE_LOOPS
+.Laligned:
+ .begin no-transform
+ l32r a4, .Lmask0 // mask for byte 0
+ l32r a7, .Lmask4
+ /* Loop forever. (a4 is more than than the maximum number
+ of iterations) */
+ loop a4, .Laligned_done
+
+ /* First unrolled loop body. */
+ l32i a8, a2, 0 // get word from s1
+ l32i a9, a3, 0 // get word from s2
+ slli a5, a8, 1
+ bne a8, a9, .Lwne2
+ or a9, a8, a5
+ bnall a9, a7, .Lprobeq
+
+ /* Second unrolled loop body. */
+ l32i a8, a2, 4 // get word from s1+4
+ l32i a9, a3, 4 // get word from s2+4
+ slli a5, a8, 1
+ bne a8, a9, .Lwne2
+ or a9, a8, a5
+ bnall a9, a7, .Lprobeq2
+
+ addi a2, a2, 8 // advance s1 pointer
+ addi a3, a3, 8 // advance s2 pointer
+.Laligned_done:
+ or a1, a1, a1 // nop
+
+.Lprobeq2:
+ /* Adjust pointers to account for the loop unrolling. */
+ addi a2, a2, 4
+ addi a3, a3, 4
+
+#else /* !XCHAL_HAVE_LOOPS */
+
+.Laligned:
+ movi a4, MASK0 // mask for byte 0
+ movi a7, MASK4
+ j .Lfirstword
+.Lnextword:
+ addi a2, a2, 4 // advance s1 pointer
+ addi a3, a3, 4 // advance s2 pointer
+.Lfirstword:
+ l32i a8, a2, 0 // get word from s1
+ l32i a9, a3, 0 // get word from s2
+ slli a5, a8, 1
+ bne a8, a9, .Lwne2
+ or a9, a8, a5
+ ball a9, a7, .Lnextword
+#endif /* !XCHAL_HAVE_LOOPS */
+
+ /* align (0 mod 4) */
+.Lprobeq:
+ /* Words are probably equal, but check for sure.
+ If not, loop over the rest of string using normal algorithm. */
+
+ bnone a8, a4, .Leq // if byte 0 is zero
+ l32r a5, .Lmask1 // mask for byte 1
+ l32r a6, .Lmask2 // mask for byte 2
+ bnone a8, a5, .Leq // if byte 1 is zero
+ l32r a7, .Lmask3 // mask for byte 3
+ bnone a8, a6, .Leq // if byte 2 is zero
+ bnone a8, a7, .Leq // if byte 3 is zero
+ addi.n a2, a2, 4 // advance s1 pointer
+ addi.n a3, a3, 4 // advance s2 pointer
+#if XCHAL_HAVE_LOOPS
+
+ /* align (1 mod 4) */
+ loop a4, .Leq // loop forever (a4 is bigger than max iters)
+ .end no-transform
+
+ l32i a8, a2, 0 // get word from s1
+ l32i a9, a3, 0 // get word from s2
+ addi a2, a2, 4 // advance s1 pointer
+ bne a8, a9, .Lwne
+ bnone a8, a4, .Leq // if byte 0 is zero
+ bnone a8, a5, .Leq // if byte 1 is zero
+ bnone a8, a6, .Leq // if byte 2 is zero
+ bnone a8, a7, .Leq // if byte 3 is zero
+ addi a3, a3, 4 // advance s2 pointer
+
+#else /* !XCHAL_HAVE_LOOPS */
+
+ j .Lfirstword2
+.Lnextword2:
+ addi a3, a3, 4 // advance s2 pointer
+.Lfirstword2:
+ l32i a8, a2, 0 // get word from s1
+ l32i a9, a3, 0 // get word from s2
+ addi a2, a2, 4 // advance s1 pointer
+ bne a8, a9, .Lwne
+ bnone a8, a4, .Leq // if byte 0 is zero
+ bnone a8, a5, .Leq // if byte 1 is zero
+ bnone a8, a6, .Leq // if byte 2 is zero
+ bany a8, a7, .Lnextword2 // if byte 3 is zero
+#endif /* !XCHAL_HAVE_LOOPS */
+
+ /* Words are equal; some byte is zero. */
+.Leq: movi a2, 0 // return equal
+ retw
+
+.Lwne2: /* Words are not equal. On big-endian processors, if none of the
+ bytes are zero, the return value can be determined by a simple
+ comparison. */
+#ifdef __XTENSA_EB__
+ or a10, a8, a5
+ bnall a10, a7, .Lsomezero
+ bgeu a8, a9, .Lposreturn
+ movi a2, -1
+ retw
+.Lposreturn:
+ movi a2, 1
+ retw
+.Lsomezero: // There is probably some zero byte.
+#endif /* __XTENSA_EB__ */
+.Lwne: /* Words are not equal. */
+ xor a2, a8, a9 // get word with nonzero in byte that differs
+ bany a2, a4, .Ldiff0 // if byte 0 differs
+ movi a5, MASK1 // mask for byte 1
+ bnone a8, a4, .Leq // if byte 0 is zero
+ bany a2, a5, .Ldiff1 // if byte 1 differs
+ movi a6, MASK2 // mask for byte 2
+ bnone a8, a5, .Leq // if byte 1 is zero
+ bany a2, a6, .Ldiff2 // if byte 2 differs
+ bnone a8, a6, .Leq // if byte 2 is zero
+#ifdef __XTENSA_EB__
+.Ldiff3:
+.Ldiff2:
+.Ldiff1:
+ /* Byte 0 is equal (at least) and there is a difference before a zero
+ byte. Just subtract words to get the return value.
+ The high order equal bytes cancel, leaving room for the sign. */
+ sub a2, a8, a9
+ retw
+
+.Ldiff0:
+ /* Need to make room for the sign, so can't subtract whole words. */
+ extui a10, a8, 24, 8
+ extui a11, a9, 24, 8
+ sub a2, a10, a11
+ retw
+
+#else /* !__XTENSA_EB__ */
+ /* Little-endian is a little more difficult because can't subtract
+ whole words. */
+.Ldiff3:
+ /* Bytes 0-2 are equal; byte 3 is different.
+ For little-endian need to have a sign bit for the difference. */
+ extui a10, a8, 24, 8
+ extui a11, a9, 24, 8
+ sub a2, a10, a11
+ retw
+
+.Ldiff0:
+ /* Byte 0 is different. */
+ extui a10, a8, 0, 8
+ extui a11, a9, 0, 8
+ sub a2, a10, a11
+ retw
+
+.Ldiff1:
+ /* Byte 0 is equal; byte 1 is different. */
+ extui a10, a8, 8, 8
+ extui a11, a9, 8, 8
+ sub a2, a10, a11
+ retw
+
+.Ldiff2:
+ /* Bytes 0-1 are equal; byte 2 is different. */
+ extui a10, a8, 16, 8
+ extui a11, a9, 16, 8
+ sub a2, a10, a11
+ retw
+
+#endif /* !__XTENSA_EB */
+
+libc_hidden_def (strcmp)
+
+#ifndef __UCLIBC_HAS_LOCALE__
+strong_alias (strcmp, strcoll)
+libc_hidden_def (strcoll)
+#endif