1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * arch/alpha/lib/ev67-strchr.S 4 * 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com> 5 * 6 * Return the address of a given character within a null-terminated 7 * string, or null if it is not found. 8 * 9 * Much of the information about 21264 scheduling/coding comes from: 10 * Compiler Writer's Guide for the Alpha 21264 11 * abbreviated as 'CWG' in other comments here 12 * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html 13 * Scheduling notation: 14 * E - either cluster 15 * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1 16 * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1 17 * Try not to change the actual algorithm if possible for consistency. 18 */ 19 #include <linux/export.h> 20 #include <asm/regdef.h> 21 22 .set noreorder 23 .set noat 24 25 .align 4 26 .globl strchr 27 .ent strchr 28 strchr: 29 .frame sp, 0, ra 30 .prologue 0 31 32 ldq_u t0, 0(a0) # L : load first quadword Latency=3 33 and a1, 0xff, t3 # E : 00000000000000ch 34 insbl a1, 1, t5 # U : 000000000000ch00 35 insbl a1, 7, a2 # U : ch00000000000000 36 37 insbl t3, 6, a3 # U : 00ch000000000000 38 or t5, t3, a1 # E : 000000000000chch 39 andnot a0, 7, v0 # E : align our loop pointer 40 lda t4, -1 # E : build garbage mask 41 42 mskqh t4, a0, t4 # U : only want relevant part of first quad 43 or a2, a3, a2 # E : chch000000000000 44 inswl a1, 2, t5 # E : 00000000chch0000 45 inswl a1, 4, a3 # E : 0000chch00000000 46 47 or a1, a2, a1 # E : chch00000000chch 48 or a3, t5, t5 # E : 0000chchchch0000 49 cmpbge zero, t0, t2 # E : bits set iff byte == zero 50 cmpbge zero, t4, t4 # E : bits set iff byte is garbage 51 52 /* This quad is _very_ serialized. Lots of stalling happens */ 53 or t5, a1, a1 # E : chchchchchchchch 54 xor t0, a1, t1 # E : make bytes == c zero 55 cmpbge zero, t1, t3 # E : bits set iff byte == c 56 or t2, t3, t0 # E : bits set iff char match or zero match 57 58 andnot t0, t4, t0 # E : clear garbage bits 59 cttz t0, a2 # U0 : speculative (in case we get a match) 60 nop # E : 61 bne t0, $found # U : 62 63 /* 64 * Yuk. This loop is going to stall like crazy waiting for the 65 * data to be loaded. Not much can be done about it unless it's 66 * unrolled multiple times - is that safe to do in kernel space? 67 * Or would exception handling recovery code do the trick here? 68 */ 69 $loop: ldq t0, 8(v0) # L : Latency=3 70 addq v0, 8, v0 # E : 71 xor t0, a1, t1 # E : 72 cmpbge zero, t0, t2 # E : bits set iff byte == 0 73 74 cmpbge zero, t1, t3 # E : bits set iff byte == c 75 or t2, t3, t0 # E : 76 cttz t3, a2 # U0 : speculative (in case we get a match) 77 beq t0, $loop # U : 78 79 $found: negq t0, t1 # E : clear all but least set bit 80 and t0, t1, t0 # E : 81 and t0, t3, t1 # E : bit set iff byte was the char 82 addq v0, a2, v0 # E : Add in the bit number from above 83 84 cmoveq t1, $31, v0 # E : Two mapping slots, latency = 2 85 nop 86 nop 87 ret # L0 : 88 89 .end strchr 90 EXPORT_SYMBOL(strchr) 91