(:result-types tagged-num)
(:policy :fast-safe)
(:generator 2
- (inst rlwinm res x
- (mod (- 32 posn) 32) ; effectively rotate right
- (- 32 size n-fixnum-tag-bits)
- (- 31 n-fixnum-tag-bits))))
+ (let ((phantom-bits (- (+ size posn) 30)))
+ (cond
+ ((plusp phantom-bits)
+ ;; The byte to be loaded into RES includes sign bits which are not
+ ;; present in the input X physically. RLWINM as used below would
+ ;; mask these out with 0 even for negative inputs.
+ (inst srawi res x phantom-bits)
+ (inst rlwinm res x
+ (mod (- 32 posn (- phantom-bits)) 32)
+ (- 32 size n-fixnum-tag-bits)
+ (- 31 n-fixnum-tag-bits)))
+ (t
+ (inst rlwinm res x
+ (mod (- 32 posn) 32) ; effectively rotate right
+ (- 32 size n-fixnum-tag-bits)
+ (- 31 n-fixnum-tag-bits)))))))
(define-vop (ldb-c/signed)
(:translate %%ldb)
(:args (x :scs (signed-reg)))
- (:arg-types signed-num (:constant (integer 1 29)) (:constant (integer 0 29)))
+ (:arg-types signed-num (:constant (integer 1 29)) (:constant (integer 0 31)))
(:info size posn)
(:results (res :scs (any-reg)))
(:result-types tagged-num)
(define-vop (ldb-c/unsigned)
(:translate %%ldb)
(:args (x :scs (unsigned-reg)))
- (:arg-types unsigned-num (:constant (integer 1 29)) (:constant (integer 0 29)))
+ (:arg-types unsigned-num (:constant (integer 1 29)) (:constant (integer 0 31)))
(:info size posn)
(:results (res :scs (any-reg)))
(:result-types tagged-num)
(mod (- (+ 32 n-fixnum-tag-bits) posn) 32)
(- 32 size n-fixnum-tag-bits)
(- 31 n-fixnum-tag-bits))))
-
\f
;;;; Modular functions:
(define-modular-fun lognot-mod32 (x) lognot :untagged nil 32)