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x86-64/truncate-c: correctly determine if the quotient is unused

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Fixes lp#2148782
This commit is contained in:
Stas Boukarev 2026-04-19 20:05:31 +03:00
parent 566883ab44
commit cfdbd482aa
1 changed files with 8 additions and 6 deletions
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14
src/compiler/x86-64/arith.lisp
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@ -2066,6 +2066,7 @@
(:temporary (:sc any-reg :from :eval :to :result) y-arg)
(:results (quo :scs (any-reg))
(rem :scs (any-reg)))
(:optional-results quo)
(:result-types tagged-num tagged-num)
(:note "inline fixnum arithmetic")
(:vop-var vop)
@ -2075,7 +2076,7 @@
;; on TRUNCATE and I don't understand how they get tried in the optimal order.
;; The benefit of that is we could just invoke the fastrem-32 or fastrem-64 vop
;; rather than having to replicate them inside here.
(when (and (not (sb-c::tn-reads quo))
(when (and (eq (tn-kind quo) :unused)
(typep y '(unsigned-byte 64))
(csubtypep (tn-ref-type (vop-args vop)) (specifier-type '(unsigned-byte 64))))
;; The reason for the concern about inputs is that the general algorithm to accept
@ -2112,11 +2113,12 @@
(inst cqo)
(inst mov y-arg (fixnumize y))
(inst idiv y-arg)
(if (location= quo rax)
(inst shl rax n-fixnum-tag-bits)
(if (= n-fixnum-tag-bits 1)
(inst lea quo (ea rax rax))
(inst lea quo (ea nil rax (ash 1 n-fixnum-tag-bits)))))
(unless (eq (tn-kind quo) :unused)
(if (location= quo rax)
(inst shl rax n-fixnum-tag-bits)
(if (= n-fixnum-tag-bits 1)
(inst lea quo (ea rax rax))
(inst lea quo (ea nil rax (ash 1 n-fixnum-tag-bits))))))
(move rem rdx))))
(define-vop (fast-truncate/unsigned=>unsigned fast-safe-arith-op)