diff --git a/src/compiler/x86/arith.lisp b/src/compiler/x86/arith.lisp index c01faf07f0c5ccc564a4a236ed200ab3da6c3bd0..13c04250a2bee329bfbe0980119dd145e777a67d 100644 --- a/src/compiler/x86/arith.lisp +++ b/src/compiler/x86/arith.lisp @@ -1459,29 +1459,48 @@ (move ecx count) (inst sar result :cl)) (immediate - (inst sar result (tn-value count)))))) + (let ((amount (tn-value count))) + ;; If the amount is greater than 31, it's the same as + ;; shifting by 31, leaving just the sign bit. + (inst sar result (if (>= amount vm:word-bits) + (1- vm:word-bits) + amount))))))) (define-vop (digit-lshr digit-ashr) (:translate bignum::%digit-logical-shift-right) (:generator 2 - (move result digit) (sc-case count (unsigned-reg + (move result digit) (move ecx count) (inst shr result :cl)) (immediate - (inst shr result (tn-value count)))))) + (let ((amount (tn-value count))) + ;; If the amount is greater than 31, the result is 0 because + ;; all the bits get shifted right and out. + (cond ((>= amount vm:word-bits) + (inst mov result 0)) + (t + (move result digit) + (inst shr result count)))))))) (define-vop (digit-ashl digit-ashr) (:translate bignum::%ashl) (:generator 2 - (move result digit) (sc-case count (unsigned-reg + (move result digit) (move ecx count) (inst shl result :cl)) (immediate - (inst shl result (tn-value count)))))) + (let ((amount (tn-value count))) + ;; If the amount is greater than 31, the result is 0 because + ;; all the bits get shifted left and out. + (cond ((>= amount vm:word-bits) + (inst mov result 0)) + (t + (move result digit) + (inst shl result amount)))))))) ;;;; Static functions.