1/* SPDX-License-Identifier: GPL-2.0 */ 2/* 3 * arch/alpha/lib/ev67-strrchr.S 4 * 21264 version by Rick Gorton <rick.gorton@alpha-processor.com> 5 * 6 * Finds length of a 0-terminated string. Optimized for the 7 * Alpha architecture: 8 * 9 * - memory accessed as aligned quadwords only 10 * - uses bcmpge to compare 8 bytes in parallel 11 * 12 * Much of the information about 21264 scheduling/coding comes from: 13 * Compiler Writer's Guide for the Alpha 21264 14 * abbreviated as 'CWG' in other comments here 15 * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html 16 * Scheduling notation: 17 * E - either cluster 18 * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1 19 * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1 20 */ 21 22#include <asm/export.h> 23#include <asm/regdef.h> 24 25 .set noreorder 26 .set noat 27 28 .align 4 29 .ent strrchr 30 .globl strrchr 31strrchr: 32 .frame sp, 0, ra 33 .prologue 0 34 35 and a1, 0xff, t2 # E : 00000000000000ch 36 insbl a1, 1, t4 # U : 000000000000ch00 37 insbl a1, 2, t5 # U : 0000000000ch0000 38 ldq_u t0, 0(a0) # L : load first quadword Latency=3 39 40 mov zero, t6 # E : t6 is last match aligned addr 41 or t2, t4, a1 # E : 000000000000chch 42 sll t5, 8, t3 # U : 00000000ch000000 43 mov zero, t8 # E : t8 is last match byte compare mask 44 45 andnot a0, 7, v0 # E : align source addr 46 or t5, t3, t3 # E : 00000000chch0000 47 sll a1, 32, t2 # U : 0000chch00000000 48 sll a1, 48, t4 # U : chch000000000000 49 50 or t4, a1, a1 # E : chch00000000chch 51 or t2, t3, t2 # E : 0000chchchch0000 52 or a1, t2, a1 # E : chchchchchchchch 53 lda t5, -1 # E : build garbage mask 54 55 cmpbge zero, t0, t1 # E : bits set iff byte == zero 56 mskqh t5, a0, t4 # E : Complete garbage mask 57 xor t0, a1, t2 # E : make bytes == c zero 58 cmpbge zero, t4, t4 # E : bits set iff byte is garbage 59 60 cmpbge zero, t2, t3 # E : bits set iff byte == c 61 andnot t1, t4, t1 # E : clear garbage from null test 62 andnot t3, t4, t3 # E : clear garbage from char test 63 bne t1, $eos # U : did we already hit the terminator? 64 65 /* Character search main loop */ 66$loop: 67 ldq t0, 8(v0) # L : load next quadword 68 cmovne t3, v0, t6 # E : save previous comparisons match 69 nop # : Latency=2, extra map slot (keep nop with cmov) 70 nop 71 72 cmovne t3, t3, t8 # E : Latency=2, extra map slot 73 nop # : keep with cmovne 74 addq v0, 8, v0 # E : 75 xor t0, a1, t2 # E : 76 77 cmpbge zero, t0, t1 # E : bits set iff byte == zero 78 cmpbge zero, t2, t3 # E : bits set iff byte == c 79 beq t1, $loop # U : if we havnt seen a null, loop 80 nop 81 82 /* Mask out character matches after terminator */ 83$eos: 84 negq t1, t4 # E : isolate first null byte match 85 and t1, t4, t4 # E : 86 subq t4, 1, t5 # E : build a mask of the bytes up to... 87 or t4, t5, t4 # E : ... and including the null 88 89 and t3, t4, t3 # E : mask out char matches after null 90 cmovne t3, t3, t8 # E : save it, if match found Latency=2, extra map slot 91 nop # : Keep with cmovne 92 nop 93 94 cmovne t3, v0, t6 # E : 95 nop # : Keep with cmovne 96 /* Locate the address of the last matched character */ 97 ctlz t8, t2 # U0 : Latency=3 (0x40 for t8=0) 98 nop 99 100 cmoveq t8, 0x3f, t2 # E : Compensate for case when no match is seen 101 nop # E : hide the cmov latency (2) behind ctlz latency 102 lda t5, 0x3f($31) # E : 103 subq t5, t2, t5 # E : Normalize leading zero count 104 105 addq t6, t5, v0 # E : and add to quadword address 106 ret # L0 : Latency=3 107 nop 108 nop 109 110 .end strrchr 111 EXPORT_SYMBOL(strrchr) 112