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Diffstat (limited to 'arch/alpha/lib/ev67-strrchr.S')
| -rw-r--r-- | arch/alpha/lib/ev67-strrchr.S | 111 |
1 files changed, 111 insertions, 0 deletions
diff --git a/arch/alpha/lib/ev67-strrchr.S b/arch/alpha/lib/ev67-strrchr.S new file mode 100644 index 000000000..7f80e3985 --- /dev/null +++ b/arch/alpha/lib/ev67-strrchr.S @@ -0,0 +1,111 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * 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 <asm/export.h> +#include <asm/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 up to... + 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 + EXPORT_SYMBOL(strrchr) |