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Diffstat (limited to 'arch/alpha/lib/ev67-strchr.S')
| -rw-r--r-- | arch/alpha/lib/ev67-strchr.S | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/arch/alpha/lib/ev67-strchr.S b/arch/alpha/lib/ev67-strchr.S new file mode 100644 index 000000000..fbf89e0b6 --- /dev/null +++ b/arch/alpha/lib/ev67-strchr.S @@ -0,0 +1,90 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * arch/alpha/lib/ev67-strchr.S + * 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com> + * + * Return the address of a given character within a null-terminated + * string, or null if it is not found. + * + * 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 + * Try not to change the actual algorithm if possible for consistency. + */ +#include <asm/export.h> +#include <asm/regdef.h> + + .set noreorder + .set noat + + .align 4 + .globl strchr + .ent strchr +strchr: + .frame sp, 0, ra + .prologue 0 + + ldq_u t0, 0(a0) # L : load first quadword Latency=3 + and a1, 0xff, t3 # E : 00000000000000ch + insbl a1, 1, t5 # U : 000000000000ch00 + insbl a1, 7, a2 # U : ch00000000000000 + + insbl t3, 6, a3 # U : 00ch000000000000 + or t5, t3, a1 # E : 000000000000chch + andnot a0, 7, v0 # E : align our loop pointer + lda t4, -1 # E : build garbage mask + + mskqh t4, a0, t4 # U : only want relevant part of first quad + or a2, a3, a2 # E : chch000000000000 + inswl a1, 2, t5 # E : 00000000chch0000 + inswl a1, 4, a3 # E : 0000chch00000000 + + or a1, a2, a1 # E : chch00000000chch + or a3, t5, t5 # E : 0000chchchch0000 + cmpbge zero, t0, t2 # E : bits set iff byte == zero + cmpbge zero, t4, t4 # E : bits set iff byte is garbage + + /* This quad is _very_ serialized. Lots of stalling happens */ + or t5, a1, a1 # E : chchchchchchchch + xor t0, a1, t1 # E : make bytes == c zero + cmpbge zero, t1, t3 # E : bits set iff byte == c + or t2, t3, t0 # E : bits set iff char match or zero match + + andnot t0, t4, t0 # E : clear garbage bits + cttz t0, a2 # U0 : speculative (in case we get a match) + nop # E : + bne t0, $found # U : + + /* + * Yuk. This loop is going to stall like crazy waiting for the + * data to be loaded. Not much can be done about it unless it's + * unrolled multiple times - is that safe to do in kernel space? + * Or would exception handling recovery code do the trick here? + */ +$loop: ldq t0, 8(v0) # L : Latency=3 + addq v0, 8, v0 # E : + xor t0, a1, t1 # E : + cmpbge zero, t0, t2 # E : bits set iff byte == 0 + + cmpbge zero, t1, t3 # E : bits set iff byte == c + or t2, t3, t0 # E : + cttz t3, a2 # U0 : speculative (in case we get a match) + beq t0, $loop # U : + +$found: negq t0, t1 # E : clear all but least set bit + and t0, t1, t0 # E : + and t0, t3, t1 # E : bit set iff byte was the char + addq v0, a2, v0 # E : Add in the bit number from above + + cmoveq t1, $31, v0 # E : Two mapping slots, latency = 2 + nop + nop + ret # L0 : + + .end strchr + EXPORT_SYMBOL(strchr) |