1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * arch/alpha/lib/strrchr.S 4 * Contributed by Richard Henderson (rth@tamu.edu) 5 * 6 * Return the address of the last occurrence of a given character 7 * within a null-terminated string, or null if it is not found. 8 */ 9 #include <linux/export.h> 10 #include <asm/regdef.h> 11 12 .set noreorder 13 .set noat 14 15 .align 3 16 .ent strrchr 17 .globl strrchr 18 strrchr: 19 .frame sp, 0, ra 20 .prologue 0 21 22 zapnot a1, 1, a1 # e0 : zero extend our test character 23 mov zero, t6 # .. e1 : t6 is last match aligned addr 24 sll a1, 8, t5 # e0 : replicate our test character 25 mov zero, t8 # .. e1 : t8 is last match byte compare mask 26 or t5, a1, a1 # e0 : 27 ldq_u t0, 0(a0) # .. e1 : load first quadword 28 sll a1, 16, t5 # e0 : 29 andnot a0, 7, v0 # .. e1 : align source addr 30 or t5, a1, a1 # e0 : 31 lda t4, -1 # .. e1 : build garbage mask 32 sll a1, 32, t5 # e0 : 33 cmpbge zero, t0, t1 # .. e1 : bits set iff byte == zero 34 mskqh t4, a0, t4 # e0 : 35 or t5, a1, a1 # .. e1 : character replication complete 36 xor t0, a1, t2 # e0 : make bytes == c zero 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) 90