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