1 /* SPDX-License-Identifier: GPL-2.0-only */ !! 1 /* SPDX-License-Identifier: GPL-2.0 */
2 /* 2 /*
3 * Based on arch/arm/lib/strrchr.S !! 3 * arch/alpha/lib/strrchr.S
>> 4 * Contributed by Richard Henderson (rth@tamu.edu)
4 * 5 *
5 * Copyright (C) 1995-2000 Russell King !! 6 * Return the address of the last occurrence of a given character
6 * Copyright (C) 2013 ARM Ltd. !! 7 * within a null-terminated string, or null if it is not found.
7 */ 8 */
>> 9 #include <linux/export.h>
>> 10 #include <asm/regdef.h>
8 11
9 #include <linux/linkage.h> !! 12 .set noreorder
10 #include <asm/assembler.h> !! 13 .set noat
11 14
12 /* !! 15 .align 3
13 * Find the last occurrence of a character in !! 16 .ent strrchr
14 * !! 17 .globl strrchr
15 * Parameters: !! 18 strrchr:
16 * x0 - str !! 19 .frame sp, 0, ra
17 * x1 - c !! 20 .prologue 0
18 * Returns: !! 21
19 * x0 - address of last occurrence of 'c' !! 22 zapnot a1, 1, a1 # e0 : zero extend our test character
20 */ !! 23 mov zero, t6 # .. e1 : t6 is last match aligned addr
21 SYM_FUNC_START(__pi_strrchr) !! 24 sll a1, 8, t5 # e0 : replicate our test character
22 mov x3, #0 !! 25 mov zero, t8 # .. e1 : t8 is last match byte compare mask
23 and w1, w1, #0xff !! 26 or t5, a1, a1 # e0 :
24 1: ldrb w2, [x0], #1 !! 27 ldq_u t0, 0(a0) # .. e1 : load first quadword
25 cbz w2, 2f !! 28 sll a1, 16, t5 # e0 :
26 cmp w2, w1 !! 29 andnot a0, 7, v0 # .. e1 : align source addr
27 b.ne 1b !! 30 or t5, a1, a1 # e0 :
28 sub x3, x0, #1 !! 31 lda t4, -1 # .. e1 : build garbage mask
29 b 1b !! 32 sll a1, 32, t5 # e0 :
30 2: mov x0, x3 !! 33 cmpbge zero, t0, t1 # .. e1 : bits set iff byte == zero
31 ret !! 34 mskqh t4, a0, t4 # e0 :
32 SYM_FUNC_END(__pi_strrchr) !! 35 or t5, a1, a1 # .. e1 : character replication complete
33 SYM_FUNC_ALIAS_WEAK(strrchr, __pi_strrchr) !! 36 xor t0, a1, t2 # e0 : make bytes == c zero
34 EXPORT_SYMBOL_NOKASAN(strrchr) !! 37 cmpbge zero, t4, t4 # .. e1 : bits set iff byte is garbage
>> 38 cmpbge zero, t2, t3 # e0 : bits set iff byte == c
>> 39 andnot t1, t4, t1 # .. e1 : clear garbage from null test
>> 40 andnot t3, t4, t3 # e0 : clear garbage from char test
>> 41 bne t1, $eos # .. e1 : did we already hit the terminator?
>> 42
>> 43 /* Character search main loop */
>> 44 $loop:
>> 45 ldq t0, 8(v0) # e0 : load next quadword
>> 46 cmovne t3, v0, t6 # .. e1 : save previous comparisons match
>> 47 cmovne t3, t3, t8 # e0 :
>> 48 addq v0, 8, v0 # .. e1 :
>> 49 xor t0, a1, t2 # e0 :
>> 50 cmpbge zero, t0, t1 # .. e1 : bits set iff byte == zero
>> 51 cmpbge zero, t2, t3 # e0 : bits set iff byte == c
>> 52 beq t1, $loop # .. e1 : if we havnt seen a null, loop
>> 53
>> 54 /* Mask out character matches after terminator */
>> 55 $eos:
>> 56 negq t1, t4 # e0 : isolate first null byte match
>> 57 and t1, t4, t4 # e1 :
>> 58 subq t4, 1, t5 # e0 : build a mask of the bytes up to...
>> 59 or t4, t5, t4 # e1 : ... and including the null
>> 60
>> 61 and t3, t4, t3 # e0 : mask out char matches after null
>> 62 cmovne t3, t3, t8 # .. e1 : save it, if match found
>> 63 cmovne t3, v0, t6 # e0 :
>> 64
>> 65 /* Locate the address of the last matched character */
>> 66
>> 67 /* Retain the early exit for the ev4 -- the ev5 mispredict penalty
>> 68 is 5 cycles -- the same as just falling through. */
>> 69 beq t8, $retnull # .. e1 :
>> 70
>> 71 and t8, 0xf0, t2 # e0 : binary search for the high bit set
>> 72 cmovne t2, t2, t8 # .. e1 (zdb)
>> 73 cmovne t2, 4, t2 # e0 :
>> 74 and t8, 0xcc, t1 # .. e1 :
>> 75 cmovne t1, t1, t8 # e0 :
>> 76 cmovne t1, 2, t1 # .. e1 :
>> 77 and t8, 0xaa, t0 # e0 :
>> 78 cmovne t0, 1, t0 # .. e1 (zdb)
>> 79 addq t2, t1, t1 # e0 :
>> 80 addq t6, t0, v0 # .. e1 : add our aligned base ptr to the mix
>> 81 addq v0, t1, v0 # e0 :
>> 82 ret # .. e1 :
>> 83
>> 84 $retnull:
>> 85 mov zero, v0 # e0 :
>> 86 ret # .. e1 :
>> 87
>> 88 .end strrchr
>> 89 EXPORT_SYMBOL(strrchr)
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