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Better variable sb-rotate-byte.

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The rotate instructions only look at the low bits of the rotate amount
register. Which means rotating left a negative amount is the same
rotating right (- negative-amount).

Do that for x86-64 and arm64.
This commit is contained in:
Stas Boukarev 2023-11-04 21:08:53 +03:00
parent d74645fa7d
commit f3e88e63e0
2 changed files with 10 additions and 32 deletions
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16
contrib/sb-rotate-byte/arm64-vm.lisp
View file

@ -25,16 +25,12 @@
(:args (count :scs (sb-vm::signed-reg))
(integer :scs (sb-vm::unsigned-reg)))
(:arg-types sb-vm::tagged-num sb-vm::unsigned-num)
(:temporary (:sc sb-vm::signed-reg) temp)
(:results (res :scs (sb-vm::unsigned-reg)))
(:result-types sb-vm::unsigned-num)
(:generator 10
(inst mov temp 32)
(inst cmp count 0)
(inst csel temp sb-vm::zr-tn temp :le)
(inst sub temp temp count)
(inst neg sb-vm::tmp-tn count)
(inst ror (sb-vm::32-bit-reg res)
(sb-vm::32-bit-reg integer) (sb-vm::32-bit-reg temp))))
(sb-vm::32-bit-reg integer) (sb-vm::32-bit-reg sb-vm::tmp-tn))))
;;; 64-bit
(define-vop (%64bit-rotate-byte/c)
@ -59,12 +55,8 @@
(:args (count :scs (sb-vm::signed-reg))
(integer :scs (sb-vm::unsigned-reg)))
(:arg-types sb-vm::tagged-num sb-vm::unsigned-num)
(:temporary (:sc sb-vm::signed-reg) temp)
(:results (res :scs (sb-vm::unsigned-reg)))
(:result-types sb-vm::unsigned-num)
(:generator 10
(inst mov temp 64)
(inst cmp count 0)
(inst csel temp sb-vm::zr-tn temp :le)
(inst sub temp temp count)
(inst ror res integer temp)))
(inst neg sb-vm::tmp-tn count)
(inst ror res integer sb-vm::tmp-tn)))

26
contrib/sb-rotate-byte/x86-64-vm.lisp
View file

@ -30,16 +30,9 @@
(:results (result :scs (sb-vm::unsigned-reg) :from :load))
(:result-types sb-vm::unsigned-num)
(:generator 10
(move result integer)
(move rcx count :dword)
(inst cmp :dword rcx 0)
(inst jmp :ge label)
(inst neg :dword rcx)
(inst ror :dword result :cl)
(inst jmp end)
LABEL
(inst rol :dword result :cl)
END))
(move result integer)
(move rcx count :dword)
(inst rol :dword result :cl)))
;;; 64-bit rotates
@ -70,13 +63,6 @@
(:results (result :scs (sb-vm::unsigned-reg) :from :load))
(:result-types sb-vm::unsigned-num)
(:generator 10
(move result integer)
(move rcx count :dword)
(inst cmp :dword rcx 0)
(inst jmp :ge label)
(inst neg :dword rcx)
(inst ror result :cl)
(inst jmp end)
LABEL
(inst rol result :cl)
END))
(move result integer)
(move rcx count :dword)
(inst rol result :cl)))