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avx2/utf8-strlen: fix the 1/2 byte fast path

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Which omits overlongs coming from the full path.
This commit is contained in:
Stas Boukarev 2026-08-24 03:33:31 +03:00
parent c104c75a3c
commit ff86fee2c0
1 changed files with 9 additions and 10 deletions
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19
src/code/x86-64-simd.lisp
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@ -2465,8 +2465,12 @@
(inst test :dword tmp tmp)
(inst jmp :z VALIDATED)
(inst vperm2i128 tmp1 prev current #x21)
(inst vpalignr tmp1 current tmp1 15)
(inst vpsubusb tmp2 tmp2 (inline-const #xDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFDFDF))
(inst vptest tmp2 tmp2)
(inst jmp :nz full)
;; 1/2 bytes
@ -2478,19 +2482,17 @@
(inst vpand tmp4 tmp4 tmp2) ;; it's a signed comparison, remove ascii
;; Find #xC0 or #xC1, which are overlong
(inst vpandn tmp1 tmp3 tmp2) ;; neither ascii or continuations
(inst vpxor tmp1 tmp1 tmp4) ;; nor a valid leading byte
(inst vpandn tmp2 tmp3 tmp2) ;; neither ascii or continuations
(inst vpxor tmp2 tmp2 tmp4) ;; nor a valid leading byte
;; Continuations must follow leading bytes,
;; they must align with the shifted input
(inst vpcmpgtb tmp2 prev-len zeros)
;; Identify leading non-ascii bytes, shifted left by
;; one byte, with the previous byte shifted in
(inst vperm2i128 tmp2 tmp2 tmp4 #x21)
(inst vpalignr tmp2 tmp4 tmp2 15)
(inst vpxor tmp2 tmp2 tmp3)
(inst vpsubusb tmp1 tmp1 (inline-const #xC1C1C1C1C1C1C1C1C1C1C1C1C1C1C1C1C1C1C1C1C1C1C1C1C1C1C1C1C1C1C1C1))
(inst vpcmpgtb tmp1 tmp1 zeros)
(inst vpxor tmp1 tmp1 tmp3)
(inst vpor tmp1 tmp1 tmp2)
(inst vpor errors errors tmp1)
@ -2503,9 +2505,6 @@
(inst jmp VALIDATED)
FULL
;; The Keiser, Lemire algorithm
(inst vperm2i128 tmp1 prev current #x21)
(inst vpalignr tmp1 current tmp1 15)
(inst vpsrlw tmp2 tmp1 4)
(inst vpand tmp2 tmp2 mask-0f)