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