--- /dev/null
+/*
+ * arch/xtensa/lib/strnlen_user.S
+ *
+ * This file is subject to the terms and conditions of the GNU General
+ * Public License. See the file "COPYING" in the main directory of
+ * this archive for more details.
+ *
+ * Returns strnlen, including trailing zero terminator.
+ * Zero indicates error.
+ *
+ * Copyright (C) 2002 Tensilica Inc.
+ */
+
+#include <xtensa/coreasm.h>
+
+/* Load or store instructions that may cause exceptions use the EX macro. */
+
+#define EX(insn,reg1,reg2,offset,handler) \
+9: insn reg1, reg2, offset; \
+ .section __ex_table, "a"; \
+ .word 9b, handler; \
+ .previous
+
+/*
+ * size_t __strnlen_user(const char *s, size_t len)
+ */
+.text
+.begin literal
+.align 4
+.Lmask0:
+ .byte 0xff, 0x00, 0x00, 0x00
+.Lmask1:
+ .byte 0x00, 0xff, 0x00, 0x00
+.Lmask2:
+ .byte 0x00, 0x00, 0xff, 0x00
+.Lmask3:
+ .byte 0x00, 0x00, 0x00, 0xff
+.end literal
+
+# Register use:
+# a2/ src
+# a3/ len
+# a4/ tmp
+# a5/ mask0
+# a6/ mask1
+# a7/ mask2
+# a8/ mask3
+# a9/ tmp
+# a10/ tmp
+
+.align 4
+.global __strnlen_user
+.type __strnlen_user,@function
+__strnlen_user:
+ entry sp, 16 # minimal stack frame
+ # a2/ s, a3/ len
+ addi a4, a2, -4 # because we overincrement at the end;
+ # we compensate with load offsets of 4
+ l32r a5, .Lmask0 # mask for byte 0
+ l32r a6, .Lmask1 # mask for byte 1
+ l32r a7, .Lmask2 # mask for byte 2
+ l32r a8, .Lmask3 # mask for byte 3
+ bbsi.l a2, 0, .L1mod2 # if only 8-bit aligned
+ bbsi.l a2, 1, .L2mod4 # if only 16-bit aligned
+
+/*
+ * String is word-aligned.
+ */
+.Laligned:
+ srli a10, a3, 2 # number of loop iterations with 4B per loop
+#if XCHAL_HAVE_LOOPS
+ loopnez a10, .Ldone
+#else
+ beqz a10, .Ldone
+ slli a10, a10, 2
+ add a10, a10, a4 # a10 = end of last 4B chunk
+#endif /* XCHAL_HAVE_LOOPS */
+.Loop:
+ EX(l32i, a9, a4, 4, lenfixup) # get next word of string
+ addi a4, a4, 4 # advance string pointer
+ bnone a9, a5, .Lz0 # if byte 0 is zero
+ bnone a9, a6, .Lz1 # if byte 1 is zero
+ bnone a9, a7, .Lz2 # if byte 2 is zero
+ bnone a9, a8, .Lz3 # if byte 3 is zero
+#if !XCHAL_HAVE_LOOPS
+ blt a4, a10, .Loop
+#endif
+
+.Ldone:
+ EX(l32i, a9, a4, 4, lenfixup) # load 4 bytes for remaining checks
+
+ bbci.l a3, 1, .L100
+ # check two more bytes (bytes 0, 1 of word)
+ addi a4, a4, 2 # advance string pointer
+ bnone a9, a5, .Lz0 # if byte 0 is zero
+ bnone a9, a6, .Lz1 # if byte 1 is zero
+.L100:
+ bbci.l a3, 0, .L101
+ # check one more byte (byte 2 of word)
+ # Actually, we don't need to check. Zero or nonzero, we'll add one.
+ # Do not add an extra one for the NULL terminator since we have
+ # exhausted the original len parameter.
+ addi a4, a4, 1 # advance string pointer
+.L101:
+ sub a2, a4, a2 # compute length
+ retw
+
+# NOTE that in several places below, we point to the byte just after
+# the zero byte in order to include the NULL terminator in the count.
+
+.Lz3: # byte 3 is zero
+ addi a4, a4, 3 # point to zero byte
+.Lz0: # byte 0 is zero
+ addi a4, a4, 1 # point just beyond zero byte
+ sub a2, a4, a2 # subtract to get length
+ retw
+.Lz1: # byte 1 is zero
+ addi a4, a4, 1+1 # point just beyond zero byte
+ sub a2, a4, a2 # subtract to get length
+ retw
+.Lz2: # byte 2 is zero
+ addi a4, a4, 2+1 # point just beyond zero byte
+ sub a2, a4, a2 # subtract to get length
+ retw
+
+.L1mod2: # address is odd
+ EX(l8ui, a9, a4, 4, lenfixup) # get byte 0
+ addi a4, a4, 1 # advance string pointer
+ beqz a9, .Lz3 # if byte 0 is zero
+ bbci.l a4, 1, .Laligned # if string pointer is now word-aligned
+
+.L2mod4: # address is 2 mod 4
+ addi a4, a4, 2 # advance ptr for aligned access
+ EX(l32i, a9, a4, 0, lenfixup) # get word with first two bytes of string
+ bnone a9, a7, .Lz2 # if byte 2 (of word, not string) is zero
+ bany a9, a8, .Laligned # if byte 3 (of word, not string) is nonzero
+ # byte 3 is zero
+ addi a4, a4, 3+1 # point just beyond zero byte
+ sub a2, a4, a2 # subtract to get length
+ retw
+
+ .section .fixup, "ax"
+ .align 4
+lenfixup:
+ movi a2, 0
+ retw
+
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