common-lisp/sbcl.sbcl
1
0
Fork 0
mirror of git://git.code.sf.net/p/sbcl/sbcl synced 2026-09-10 07:26:40 -04:00
Code Issues Actions 8 Packages Projects Releases Wiki Activity

arm64/character-string-to-utf8: don't use a lookup table for sizes

Browse source 
Use a sequence of gpr instructions. Sits somewhere in the middle
between a lookup table and vector instructions, but doesn't depend on
the L1 cache.
This commit is contained in:
Stas Boukarev 2026-08-15 02:52:21 +03:00
parent 3c314be353
commit 4c9ebabb78
1 changed files with 12 additions and 9 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

21
src/code/arm64-simd.lisp
View file

@ -1423,7 +1423,7 @@
((tmp unsigned-reg))
((full-table any-reg t))
((size-table any-reg t))
((tmp2 any-reg t))
((shift-mask complex-double-reg))
((c-d800 complex-double-reg))
@ -1533,12 +1533,6 @@
(load-inline-constant shift-mask :oword #x6000000040000000200000000)
(load-inline-constant full-table (make-full-table))
(load-inline-constant size-table (let ((table (make-array 256 :element-type '(unsigned-byte 8))))
(loop for row below 256
for total-bytes = (loop for lane below 4
sum (1+ (ldb (byte 2 (* lane 2)) row)))
do (setf (aref table row) total-bytes))
table))
(inst movi c-d800 #xd800 :4s)
(inst movi length1 3 :16b)
(load-inline-constant length2 :oword #x00000000000000010101010202020202)
@ -1570,7 +1564,16 @@
(inst addv temp temp :4s)
(inst umov tmp temp 0 :b)
(inst ldrb tmp-tn (@ size-table tmp))
;; Do a sum of lengths in gprs,
;; since addv+umov uses already saturated vector execution ports.
;; Using a lookup table might be slightly faster
;; but relies on it always being in L1.
(progn
(inst and (32-bit-reg tmp-tn) tmp #x33333333)
(inst and (32-bit-reg tmp2) tmp #xCCCCCCCC)
(inst add tmp-tn tmp-tn (lsr tmp2 2))
(inst add tmp-tn tmp-tn (lsr tmp-tn 4))
(inst and tmp-tn tmp-tn #x0F))
;; Multiply by 48 (3 * 16)
(inst add tmp tmp (lsl tmp 1))
@ -1583,7 +1586,7 @@
(inst and bytes bytes and-mask :16b)
(inst orr bytes bytes orr-mask :16b)
(inst str bytes (@ byte-array))
(inst str bytes (@ byte-array 4 :post-index))
(inst add byte-array byte-array tmp-tn)
(inst add string string 16))