1/* 2 * arch/alpha/lib/strrchr.S 3 * Contributed by Richard Henderson (rth@tamu.edu) 4 * 5 * Return the address of the last occurrence of a given character 6 * within a null-terminated string, or null if it is not found. 7 */ 8 9#include <asm/regdef.h> 10 11 .set noreorder 12 .set noat 13 14 .align 3 15 .ent strrchr 16 .globl strrchr 17strrchr: 18 .frame sp, 0, ra 19 .prologue 0 20 21 zapnot a1, 1, a1 # e0 : zero extend our test character 22 mov zero, t6 # .. e1 : t6 is last match aligned addr 23 sll a1, 8, t5 # e0 : replicate our test character 24 mov zero, t8 # .. e1 : t8 is last match byte compare mask 25 or t5, a1, a1 # e0 : 26 ldq_u t0, 0(a0) # .. e1 : load first quadword 27 sll a1, 16, t5 # e0 : 28 andnot a0, 7, v0 # .. e1 : align source addr 29 or t5, a1, a1 # e0 : 30 lda t4, -1 # .. e1 : build garbage mask 31 sll a1, 32, t5 # e0 : 32 cmpbge zero, t0, t1 # .. e1 : bits set iff byte == zero 33 mskqh t4, a0, t4 # e0 : 34 or t5, a1, a1 # .. e1 : character replication complete 35 xor t0, a1, t2 # e0 : make bytes == c zero 36 cmpbge zero, t4, t4 # .. e1 : bits set iff byte is garbage 37 cmpbge zero, t2, t3 # e0 : bits set iff byte == c 38 andnot t1, t4, t1 # .. e1 : clear garbage from null test 39 andnot t3, t4, t3 # e0 : clear garbage from char test 40 bne t1, $eos # .. e1 : did we already hit the terminator? 41 42 /* Character search main loop */ 43$loop: 44 ldq t0, 8(v0) # e0 : load next quadword 45 cmovne t3, v0, t6 # .. e1 : save previous comparisons match 46 cmovne t3, t3, t8 # e0 : 47 addq v0, 8, v0 # .. e1 : 48 xor t0, a1, t2 # e0 : 49 cmpbge zero, t0, t1 # .. e1 : bits set iff byte == zero 50 cmpbge zero, t2, t3 # e0 : bits set iff byte == c 51 beq t1, $loop # .. e1 : if we havnt seen a null, loop 52 53 /* Mask out character matches after terminator */ 54$eos: 55 negq t1, t4 # e0 : isolate first null byte match 56 and t1, t4, t4 # e1 : 57 subq t4, 1, t5 # e0 : build a mask of the bytes up to... 58 or t4, t5, t4 # e1 : ... and including the null 59 60 and t3, t4, t3 # e0 : mask out char matches after null 61 cmovne t3, t3, t8 # .. e1 : save it, if match found 62 cmovne t3, v0, t6 # e0 : 63 64 /* Locate the address of the last matched character */ 65 66 /* Retain the early exit for the ev4 -- the ev5 mispredict penalty 67 is 5 cycles -- the same as just falling through. */ 68 beq t8, $retnull # .. e1 : 69 70 and t8, 0xf0, t2 # e0 : binary search for the high bit set 71 cmovne t2, t2, t8 # .. e1 (zdb) 72 cmovne t2, 4, t2 # e0 : 73 and t8, 0xcc, t1 # .. e1 : 74 cmovne t1, t1, t8 # e0 : 75 cmovne t1, 2, t1 # .. e1 : 76 and t8, 0xaa, t0 # e0 : 77 cmovne t0, 1, t0 # .. e1 (zdb) 78 addq t2, t1, t1 # e0 : 79 addq t6, t0, v0 # .. e1 : add our aligned base ptr to the mix 80 addq v0, t1, v0 # e0 : 81 ret # .. e1 : 82 83$retnull: 84 mov zero, v0 # e0 : 85 ret # .. e1 : 86 87 .end strrchr 88