1*4882a593Smuzhiyun/* SPDX-License-Identifier: GPL-2.0 */ 2*4882a593Smuzhiyun/* 3*4882a593Smuzhiyun * arch/alpha/lib/ev67-strrchr.S 4*4882a593Smuzhiyun * 21264 version by Rick Gorton <rick.gorton@alpha-processor.com> 5*4882a593Smuzhiyun * 6*4882a593Smuzhiyun * Finds length of a 0-terminated string. Optimized for the 7*4882a593Smuzhiyun * Alpha architecture: 8*4882a593Smuzhiyun * 9*4882a593Smuzhiyun * - memory accessed as aligned quadwords only 10*4882a593Smuzhiyun * - uses bcmpge to compare 8 bytes in parallel 11*4882a593Smuzhiyun * 12*4882a593Smuzhiyun * Much of the information about 21264 scheduling/coding comes from: 13*4882a593Smuzhiyun * Compiler Writer's Guide for the Alpha 21264 14*4882a593Smuzhiyun * abbreviated as 'CWG' in other comments here 15*4882a593Smuzhiyun * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html 16*4882a593Smuzhiyun * Scheduling notation: 17*4882a593Smuzhiyun * E - either cluster 18*4882a593Smuzhiyun * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1 19*4882a593Smuzhiyun * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1 20*4882a593Smuzhiyun */ 21*4882a593Smuzhiyun 22*4882a593Smuzhiyun#include <asm/export.h> 23*4882a593Smuzhiyun#include <asm/regdef.h> 24*4882a593Smuzhiyun 25*4882a593Smuzhiyun .set noreorder 26*4882a593Smuzhiyun .set noat 27*4882a593Smuzhiyun 28*4882a593Smuzhiyun .align 4 29*4882a593Smuzhiyun .ent strrchr 30*4882a593Smuzhiyun .globl strrchr 31*4882a593Smuzhiyunstrrchr: 32*4882a593Smuzhiyun .frame sp, 0, ra 33*4882a593Smuzhiyun .prologue 0 34*4882a593Smuzhiyun 35*4882a593Smuzhiyun and a1, 0xff, t2 # E : 00000000000000ch 36*4882a593Smuzhiyun insbl a1, 1, t4 # U : 000000000000ch00 37*4882a593Smuzhiyun insbl a1, 2, t5 # U : 0000000000ch0000 38*4882a593Smuzhiyun ldq_u t0, 0(a0) # L : load first quadword Latency=3 39*4882a593Smuzhiyun 40*4882a593Smuzhiyun mov zero, t6 # E : t6 is last match aligned addr 41*4882a593Smuzhiyun or t2, t4, a1 # E : 000000000000chch 42*4882a593Smuzhiyun sll t5, 8, t3 # U : 00000000ch000000 43*4882a593Smuzhiyun mov zero, t8 # E : t8 is last match byte compare mask 44*4882a593Smuzhiyun 45*4882a593Smuzhiyun andnot a0, 7, v0 # E : align source addr 46*4882a593Smuzhiyun or t5, t3, t3 # E : 00000000chch0000 47*4882a593Smuzhiyun sll a1, 32, t2 # U : 0000chch00000000 48*4882a593Smuzhiyun sll a1, 48, t4 # U : chch000000000000 49*4882a593Smuzhiyun 50*4882a593Smuzhiyun or t4, a1, a1 # E : chch00000000chch 51*4882a593Smuzhiyun or t2, t3, t2 # E : 0000chchchch0000 52*4882a593Smuzhiyun or a1, t2, a1 # E : chchchchchchchch 53*4882a593Smuzhiyun lda t5, -1 # E : build garbage mask 54*4882a593Smuzhiyun 55*4882a593Smuzhiyun cmpbge zero, t0, t1 # E : bits set iff byte == zero 56*4882a593Smuzhiyun mskqh t5, a0, t4 # E : Complete garbage mask 57*4882a593Smuzhiyun xor t0, a1, t2 # E : make bytes == c zero 58*4882a593Smuzhiyun cmpbge zero, t4, t4 # E : bits set iff byte is garbage 59*4882a593Smuzhiyun 60*4882a593Smuzhiyun cmpbge zero, t2, t3 # E : bits set iff byte == c 61*4882a593Smuzhiyun andnot t1, t4, t1 # E : clear garbage from null test 62*4882a593Smuzhiyun andnot t3, t4, t3 # E : clear garbage from char test 63*4882a593Smuzhiyun bne t1, $eos # U : did we already hit the terminator? 64*4882a593Smuzhiyun 65*4882a593Smuzhiyun /* Character search main loop */ 66*4882a593Smuzhiyun$loop: 67*4882a593Smuzhiyun ldq t0, 8(v0) # L : load next quadword 68*4882a593Smuzhiyun cmovne t3, v0, t6 # E : save previous comparisons match 69*4882a593Smuzhiyun nop # : Latency=2, extra map slot (keep nop with cmov) 70*4882a593Smuzhiyun nop 71*4882a593Smuzhiyun 72*4882a593Smuzhiyun cmovne t3, t3, t8 # E : Latency=2, extra map slot 73*4882a593Smuzhiyun nop # : keep with cmovne 74*4882a593Smuzhiyun addq v0, 8, v0 # E : 75*4882a593Smuzhiyun xor t0, a1, t2 # E : 76*4882a593Smuzhiyun 77*4882a593Smuzhiyun cmpbge zero, t0, t1 # E : bits set iff byte == zero 78*4882a593Smuzhiyun cmpbge zero, t2, t3 # E : bits set iff byte == c 79*4882a593Smuzhiyun beq t1, $loop # U : if we havnt seen a null, loop 80*4882a593Smuzhiyun nop 81*4882a593Smuzhiyun 82*4882a593Smuzhiyun /* Mask out character matches after terminator */ 83*4882a593Smuzhiyun$eos: 84*4882a593Smuzhiyun negq t1, t4 # E : isolate first null byte match 85*4882a593Smuzhiyun and t1, t4, t4 # E : 86*4882a593Smuzhiyun subq t4, 1, t5 # E : build a mask of the bytes up to... 87*4882a593Smuzhiyun or t4, t5, t4 # E : ... and including the null 88*4882a593Smuzhiyun 89*4882a593Smuzhiyun and t3, t4, t3 # E : mask out char matches after null 90*4882a593Smuzhiyun cmovne t3, t3, t8 # E : save it, if match found Latency=2, extra map slot 91*4882a593Smuzhiyun nop # : Keep with cmovne 92*4882a593Smuzhiyun nop 93*4882a593Smuzhiyun 94*4882a593Smuzhiyun cmovne t3, v0, t6 # E : 95*4882a593Smuzhiyun nop # : Keep with cmovne 96*4882a593Smuzhiyun /* Locate the address of the last matched character */ 97*4882a593Smuzhiyun ctlz t8, t2 # U0 : Latency=3 (0x40 for t8=0) 98*4882a593Smuzhiyun nop 99*4882a593Smuzhiyun 100*4882a593Smuzhiyun cmoveq t8, 0x3f, t2 # E : Compensate for case when no match is seen 101*4882a593Smuzhiyun nop # E : hide the cmov latency (2) behind ctlz latency 102*4882a593Smuzhiyun lda t5, 0x3f($31) # E : 103*4882a593Smuzhiyun subq t5, t2, t5 # E : Normalize leading zero count 104*4882a593Smuzhiyun 105*4882a593Smuzhiyun addq t6, t5, v0 # E : and add to quadword address 106*4882a593Smuzhiyun ret # L0 : Latency=3 107*4882a593Smuzhiyun nop 108*4882a593Smuzhiyun nop 109*4882a593Smuzhiyun 110*4882a593Smuzhiyun .end strrchr 111*4882a593Smuzhiyun EXPORT_SYMBOL(strrchr) 112